Year of Dis Cov Ery: 260 B.C

100 Greatest Sci ence Dis cov er ies of All Time

Kend all Ha ven

Westport, Con nect i cut • London Li brary of Con gress Cat a log ing-in-Pub li ca tion Data Ha ven, Kend all F. 100 great est science dis cov er ies of all time / Kendall Ha ven. p. cm. Includes biblio graph i cal refer ences and index. ISBN-13: 978-1-59158-265-6 (alk. paper) ISBN-10: 1-59158-265-2 (alk. paper) 1. Dis cov er ies in sci ence. I. Title. II. Ti tle: One hundred great est science dis cov er ies of all time. Q180.55.D57H349 2007 509—dc22 2006032417 Brit ish Li brary Cat a logu ing in Pub li ca tion Data is avail able. Copyright © 2007 by Kendall Haven All rights reserved. No portion of this book may be repro duced, by any process or technique, without the express written consent of the publisher. Library of Congress Cata log Card Number: 2006032417 ISBN: 978-1-59158-265-6 First published in 2007 Librar ies Unlim ited, 88 Post Road West, Westport, CT 06881 A Member of the Greenwood Publish ing Group, Inc. www.lu.com Printed in the United States of Amer ica

The paper used in this book complies with the Perma nent Paper Standard issued by the National In for ma tion Stan dards Or ga ni za tion (Z39.48-1984). 10 9 8 7 6 5 4 3 2 1 Con tents

Con tents Con tents

Acknowl edg ments ...... ix In tro duc tion ...... xi How to Use this Book ...... xv

Levers and Buoyancy ...... 3 The Sun Is the Center of the Universe ...... 5 Hu man Anat omy ...... 7 The Law of Falling Objects ...... 9 Plan e tary Mo tion ...... 11 Ju pi ter’s Moons ...... 13 Hu man Cir cu la tory Sys tem ...... 15 Air Pressure ...... 17 Boyle’s Law ...... 19 The Ex is tence of Cells ...... 21 Uni ver sal Grav i ta tion ...... 23 Fos sils...... 25 Distance to the Sun...... 27 Bac te ria...... 29 Laws of Motion ...... 31 Order in Nature ...... 33 Gal ax ies ...... 36 The Na ture of Elec tric ity ...... 38 Oceans Con trol Global Weather...... 40 Ox y gen ...... 43 Pho to syn the sis ...... 45 Con ser va tion of Mat ter...... 47 The Na ture of Heat ...... 49 Erosion of the Earth ...... 51 Vac ci na tions ...... 53 In fra red and Ul travi o let ...... 55 An es the sia...... 57 At oms ...... 59 Elec tro chem i cal Bond ing ...... 61 The Ex is tence of Mol e cules ...... 63 Elec tro mag ne tism ...... 65 First Di no saur Fos sil...... 67 Ice Ages ...... 69 Cal o ries (Units of Energy) ...... 71 Con ser va tion of En ergy ...... 73

v vi Con tents

Dopp ler Ef fect ...... 75 Germ The ory ...... 77 The The ory of Evolu tion ...... 79 Atomic Light Sig natures ...... 81 Elec tro mag netic Ra di a tion/Ra dio Waves...... 83 He red ity ...... 86 Deep-Sea Life...... 88 Pe ri odic Chart of El e ments...... 90 Cell Di vi sion...... 92 X-Rays ...... 95 Blood Types ...... 97 Elec tron ...... 99 Vi rus ...... 101 Mi to chon dria ...... 103 Ra dio ac tiv ity...... 105 At mo spheric Lay ers ...... 107 Hor mones ...... 109 E = mc2 ...... 111 Rel a tiv ity ...... 114 Vi ta mins ...... 117 Ra dio ac tive Dat ing ...... 119 Func tion of Chro mo somes ...... 121 An ti bi ot ics ...... 124 Fault Lines ...... 126 Su per con duc tiv ity...... 128 Atomic Bond ing ...... 131 Iso topes...... 133 Earth’s Core and Mantle ...... 136 Con ti nen tal Drift...... 138 Black Holes ...... 140 Insu lin ...... 142 Neurotransmitters ...... 144 Hu man Evo lu tion ...... 146 Quan tum The ory...... 148 Ex pand ing Uni verse ...... 150 Un cer tainty Prin ci ple ...... 153 Speed of Light ...... 155 Pen i cil lin...... 158 An ti mat ter...... 160 Neu tron...... 163 Cell Structure ...... 165 The Func tion of Genes ...... 167 Eco sys tem...... 169 Weak and Strong Force ...... 171 Me tab o lism...... 174 Con tents vii

Coe la canth ...... 176 Nu clear Fis sion...... 178 Blood Plasma ...... 181 Semi con duc tor Tran sis tor...... 183 The Big Bang ...... 185 Def i ni tion of In for ma tion ...... 188 Jumpin’ Genes ...... 190 Fu sion ...... 192 Or i gins of Life ...... 194 DNA ...... 196 Seafloor Spreading ...... 199 The Nature of the Atmo sphere ...... 201 Quarks ...... 203 Quasars and Pulsars ...... 205 Com plete Evo lu tion ...... 208 Dark Mat ter ...... 211 The Nature of Dino saurs ...... 213 Planets Exist Around Other Stars ...... 215 Ac cel er at ing Uni verse ...... 218 Hu man Ge nome ...... 220

Ref er ences ...... 223 Ap pen dix 1: Dis cov er ies by Sci en tific Field ...... 229 Ap pen dix 2: Sci en tists ...... 233 Appen dix 3: The Next 40 ...... 237 In dex...... 239

Ac knowl edg ments

I owe a great deal of thanks to those who have helped me research and shape these entries. The librar i ans at the Sonoma County Public Library and those at the Sonoma State Charles Schultz Library have been invalu able in helping me locate and review the many thousands of refer ences I used for this work. I owe a special thanks to Roni Berg, the love of my life, for her work in both shaping these indi vid ual entries and in creat ing the 100 fun facts you will read in this book. Finally, I owe a great thank you to Barbara Ittner, the Li- braries Unlim ited edi tor who steadfastly supported and encour aged me to create this book and whose wisdom and in sights shaped it and are reflected on every page.

In tro duc tion

In tro duc tion In tro duc tion

Discov ery! The very word sends tingles surging up your spine. It quickens your pulse. Dis cover ies are the mo ments of “Ah, ha! I under stand!” and of “Eureka! I found it!” Every one longs to discover something —anything! A discov ery is finding or observ ing something new—something unknown or unno ticed before. It is notic ing what was always there but had been overlooked by all before. It is stretching out into untouched and un- charted regions. Discov er ies open new hori zons, provide new insights, and create vast for- tunes. Dis cover ies mark the progress of human civi li za tions. They advance human knowledge. Courtroom ju ries try to dis cover the truth. Anthro pol o gists discover arti facts from past human civi li za tions and cultures. People under go ing psycho ther apy try to discover themselves. When we say that Colum bus “discov ered” the New World, we don’t mean that he created it, devel oped it, designed it, or invented it. The New World had always been there. Na- tives had lived on it for thousands of years be fore Co lumbus’s 1492 arrival. They knew the Carib bean Islands long before Colum bus arrived and certainly didn’t need a Euro pean to discover the islands for them. What Colum bus did do was make Euro pean soci et ies aware of this new conti nent. He was the first Euro pean to locate this new land mass and put it on the maps. That made it a discovery. Dis cov er ies are of ten un ex pected. Vera Ru bin dis cov ered cos mic dark mat ter in 1970. She wasn’t search ing for dark matter. In fact, she didn’t known that such a thing existed until her discov ery proved that it was there. She even had to invent a name (dark matter) for it af ter she had dis cov ered its existence. Sometimes a discov ery is built upon previ ous work by other scien tists, but more often not. Some dis cover ies are the re sult of long years of research by the discov er ing scien tist. But just as often, they are not. Discov er ies often come sud denly and repre sent the be ginning points for new fields of study or new focuses for existing scientific fields. Why study dis cov er ies? Be cause dis cov er ies chart the di rec tion of hu man de vel op - ment and prog ress. To day’s dis cov er ies will shape to mor row’s world. Ma jor dis cov er ies define the direc tions science takes, what scien tists believe, and how our view of the world changes over time. Einstein’s 1905 discov ery of rela tiv ity radi cally altered twentieth- century physics. Discov er ies chart the path and progress of science just as floating buoy mark ers reveal the course of a twisting chan nel through a wide and shallow bay. Dis cov er ies of ten rep re sent rad i cally new con cepts and ideas. They cre ate vir tu ally all of the sharp de partures from previ ous knowl edge, life, and think ing. These new scien tific discov er ies are as impor tant to our evolu tion as are the evolu tion ary changes to our DNA that have al lowed us to phys ically adapt to our changing environments.

xi xii In tro duc tion

This book briefly describes the 100 greatest science discov er ies of all time, the discov - eries that have had the greatest impact on the devel op ment of human science and thinking. Let me be clear about ex actly what that means: Great est: “Of highest impor tance; much higher in some quality or degree of under - stand ing” (Web ster’s New Col lege Dic tio nary). Sci ence: Any of the spe cific branches of sci en tific knowl edge (phys i cal sci ences, earth sci ences, and life sci ences) that derive knowledge from system atic ob ser vation, study, and ex per i men ta tion. Dis cov ery: The first time some thing is seen, found out about, re alized, or known. All time: The re corded (writ ten) his tory of hu man civ i li za tions. This book, then, de scribes the process of find ing out, of real iz ing key scien tific infor - mation for the 100 science discov er ies of the highest impor tance over the course of recorded human history. These are the biggest and most impor tant of all of the thousands of sci ence dis cov er ies. These are the sci ence dis cov er ies that rep re sent the great est ef forts by the best and brightest in the world of science. There are many areas of human de velop ment and many kinds of impor tant discov er ies not in cluded here—for ex am ple, dis cov er ies in art, cul ture, ex plo ra tion, phi los o phy, so ci - ety, history, or reli gion. I also ex cluded sci ence discov er ies that cannot be attrib uted to the work of one indi vid ual or to a small group of collab o ra tors. Global warming, as an exam ple, is a major re search focus of our time. Its dis covery may be criti cal to mil lions—if not billions—of human lives. However, no one indi vid ual can be credited with the discov ery of global warm ing. At a mini mum, 30 research ers spread over 25 years each had a hand in making this global discovery. So it is not included in my list of 100. You will meet many of the giants of science in this book. Many—but certainly not all. There are many who have made major contri bu tions to the his tory and thought of science without making one specific discov ery that quali fies as one of the 100 greatest. Many of the world’s greatest thinkers and discover ers are not here because their discov er ies do not qual- ify as sci ence discoveries. Discov er ies are not normally sought or made in response to exist ing practi cal needs, as are in ven tions. Dis cov er ies ex pand hu man knowl edge and un der stand ing. Of ten, it takes de cades (or even cen tu ries) for sci en tists to un der stand and ap pre ci ate dis cov er ies that turn out to be criti cal. Gregor Mendel’s discov ery of the concept of hered ity is a good exam ple. No one recog nized the im portance of this dis covery for more than 50 years—even though we now regard it as the founding point for the science of genet ics. Einstein’s theory of rela - tiv ity was in stantly rec og nized as a major dis cov ery. How ever, a century later, scien tists still strug gle to under stand what it means and how to use it as we inch farther into space. That would not be the case with a great inven tion. The process of inven tion focuses on the creation of prac tical devices and products. Inven tors apply knowledge and under stand - ing to solve exist ing, pressing problems. Great inven tions have an imme di ate and practical use. Intro duc tion xiii

Not so with discov er ies. Einstein’s theory of rela tiv ity produced no new products, prac tices, or concepts that af fect our daily life. Nei ther did Kepler’s dis cov ery of the ellip ti - cal orbits of the plan ets around the sun. The same is true of Alfred Wegener’s discov ery that the con ti nents drift. Yet each rep re sents a great and ir re place ably im por tant ad vance in our un derstand ing of our world and of the universe. I had three main purposes in shap ing and writing this book: 1. To pres ent key sci entific discov er ies and show their impact on our thinking and un der stand ing. 2. To present each discov ery within the contin uum of scien tific progress and devel - op ment. 3. To show the process of con ducting scien tific explo ra tion through the context of these dis cov er ies. It is inter est ing to note that the scien tists who are asso ciated with these 100 greatest sci ence dis cov er ies have more traits and char acter is tics in com mon than do those as so ci - ated with the 100 greatest sci ence inven tions (see my book by that title, Librar ies Unlim - ited, 2005). The scien tists listed in this book—those who have made major science dis cov er ies—in gen eral ex celled at math as students and received ad vanced de grees in sci ence or en gi neer ing. As a group they were fasci nated by nature and the world around them. They felt a strong passion for their fields of science and for their work. They were often already estab - lished profes sion als in their fields when they made their grand discov er ies. Their discov er - ies tend to be the re sult of dedi cated ef fort and cre ative initia tive. They got ex cited about some aspect of their scien tific field and worked hard, long hours with ded ica tion and in spi- ration. These are im pres sive men and women we can hold up as model scien tists, both fortu - nate in their oppor tu ni ties and to be emu lated in how they took advan tage of those oppor tu ni ties and applied both dili gence and honesty in their pursuit of their chosen fields. It is also amazing to con sider how re cent many of these dis cov er ies are that we take for granted and consider to be common knowledge. Seafloor spreading was only discov ered 50 years ago, the exis tence of other galax ies only 80 years ago, the exis tence of neutrons only 70 years ago. Science only discov ered the true nature and behav ior of dino saurs 30 years ago and of nuclear fusion only 50 years ago. The concept of an ecosys tem is only 70 years old, That of metab o lism is also only 70 years old. Yet already each of these concepts has woven itself into the tapes try of common knowledge for all Americans. I had to devise some crite ria to compare and rank the many impor tant science discov er - ies since I had lit er ally thousands of dis cov er ies to choose from. Here are the seven cri te ria I used: 1. Does this discov ery rep resent truly new thinking, or just a re finement and im- provement of some exist ing concept? 2. What is the extent to which this discov ery has altered and reshaped scien tific direc tion and re search? Has this dis cov ery changed the way sci ence views the world in a fun da men tal way? Has it rad i cally al tered or re di rected the way sci en - tists think and act? xiv In tro duc tion

3. What is the impor tance of this dis covery to the devel op ment of that specific field of sci ence? 4. Has this discov ery had long-term effects on human devel op ment? Has its impact filtered down to our daily lives? 5. Is this a discov ery within a recog nized field of science? Is it a sci ence dis cov ery? 6. Am I ade quately repre sent ing the breadth and diver sity of the many fields, subfields, and spe cial ties of sci ence? 7. Can this dis covery be correctly credited to one indi vid ual and to one event or to one prolonged re search effort? There are many worthy discov er ies and many worthy scien tists that did not make the final cut to be repre sented here. All of them are wor thy of study and of acclaim. Find your own fa vorites and re search them and their contri bu tions (see Appen dix 3 for ad ditional suggestions). Sev eral en tries in clude two dis cov er ies be cause they are closely linked and be cause neither alone quali fies as one of the 100 greatest. However, consid ered collec tively, they take on an im portance far greater than their indi vid ual im pact would suggest. Enjoy these stories. Revel in the wisdom and greatness of these discov er ies. Search for your own fa vorites. Then research them and create your own dis covery stories to share! How to Use This Book

How to Use this Book How to Use this Book

This book provides a wealth of infor ma tion on—obvi ously—sci ence discov er ies, but also on the process of doing science, and glimpses into the lives of the many fasci nat ing people who have ad vanced our scien tific knowledge. Use the book as a refer ence for science units and lessons focused on differ ent aspects of, or fields of science. Use it to intro duce units on discov er ies, or on the process of doing sci ence. Use it as a ref er ence for sci ence bi og ra phy re search. Use it as an in tro duc tion to the process of discov ery and the process of conduct ing scien tific study. Use it for fun reading. Each entry is divided into four sections. An intro duc tory section defines the discov ery and lists its name, year of discov ery, and discov er ing scien tist. This is followed by a brief justi fi ca tion for placing this discov ery on the greatest 100 list (“Why Is This One of the 100 Great est?”). The body of each en try (“How Was It Discov ered?”) focuses on how the dis covery was made. These sections pro vide a look at the process of science and will help students ap- preci ate the diffi culty of, the impor tance of, and the process of scien tific discov ery. Follow - ing this discus sion, I have included a Fun Fact (an intrigu ing fact related to the subject of the dis cov ery) and a few se lected ref er ences. More gen eral ref er ences are listed at the back of the book. Follow ing the 100 discov ery en tries, I have included three appen dixes and a list of general refer ences. The list of the 100 discov er ies by their field of science (Appen dix 1), an alpha bet i cal list of all mentioned scien tists (Appen dix 2), and a list of “The Next 40” (Ap - pendix 3). This is a list of 40 im portant discov er ies that just missed inclu sion on my 100 Greatest list and is an impor tant source list for addi tional dis cov eries for students to re - search and discover for themselves.

100 Great est Sci ence Dis cov er ies of All Time

Le vers and Buoy ancy

Levers and Buoyancy Levers And Buoyancy Year of Dis cov ery: 260 B.C.

What Is It? The two fun da men tal prin ci ples un der ly ing all phys ics and en gi neer ing. Who Dis cov ered It? Ar chi me des

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The concepts of buoyancy (water pushes up on an object with a force equal to the weight of water that the object displaces) and of levers (a force pushing down on one side of a le ver creates a lifting force on the other side that is pro portional to the lengths of the two sides of the lever) lie at the founda tion of all quanti ta tive science and engi neer ing. They repre sent hu man ity’s ear li est break throughs in un der stand ing the re la tion ships in the phys i cal world around us and in devis ing mathe mat ical ways to describe the physi cal phenom ena of the world. Countless engi neer ing and scien tific advances have depended on those two discoveries.

How Was It Discov ered?

How Was It Discov ered? In 260 B.C. 26-year-old Archi me des studied the two known sciences—as tron omy and geom e try—in Syra cuse, Sicily. One day Archi me des was distracted by four boys playing on the beach with a driftwood plank. They balanced the board over a waist-high rock. One boy straddled one end while his three friends jumped hard onto the other. The lone boy was tossed into the air. The boys slid the board off-center along their balanc ing rock so that only one-quarter of it re mained on the short side. Three of the boys climbed onto the short, top end. The fourth boy bounded onto the rising long end, crashing it back down to the sand and cata pult - ing his three friends into the air. Ar chi me des was fas ci nated. And he de ter mined to un der stand the prin ci ples that so eas ily al lowed a small weight (one boy) to lift a large weight (three boys). Archi me des used a strip of wood and small wooden blocks to model the boys and their driftwood. He made a trian gu lar block to model their rock. By measur ing as he balanced differ ent combi na tions of weights on each end of the lever (le ver came from the Latin word mean ing “to lift”), Archi medes re al ized that le vers were an ex ample of one of Euclid’s pro - portions at work. The force (weight) pushing down on each side of the lever had to be pro- portional to the lengths of board on each side of the balance point. He had discov ered the math emat ical concept of levers, the most common and basic lifting system ever devised. 3 4 Levers and Buoyancy

Fif teen years later, in 245 B.C., Archi me des was ordered by King Hieron to find out whether a goldsmith had cheated the king. Hieron had given the smith a weight of gold and asked him to fashion a solid-gold crown. Even though the crown weighed exactly the same as the origi nal gold, the king suspected that the gold smith had wrapped a thin layer of gold around some other, cheaper metal inside. Archi me des was or dered to discover whether the crown was solid gold without dam aging the crown itself. It seemed like an impos si ble task. In a public bathhouse Archi me des noticed his arm float ing on the water’s sur face. A vague idea began to form in his mind. He pulled his arm completely under the surface. Then he re laxed and it floated back up. He stood up in the tub. The water level dropped around the tub’s sides. He sat back down. The water level rose. He lay down. The wa ter rose higher, and he re alized that he felt lighter. He stood up. The water level fell and he felt heavier. Wa ter had to be push ing up on his sub merged body to make it feel lighter. He carried a stone and a block of wood of about the same size into the tub and sub merged them both. The stone sank, but felt lighter. He had to push the wood down to submerge it. That meant that water pushed up with a force related to the amount of water displaced by the ob ject (the object’s size) rather than to the object’s weight. How heavy the ob ject felt in the water had to re late to the object’s den sity (how much each unit vol ume of it weighed). That showed Archi me des how to answer the king’s question. He returned to the king. The key was den sity. If the crown was made of some other metal than gold, it could weigh the same but would have a differ ent den sity and thus oc cupy a differ ent volume. The crown and an equal weight of gold were dunked into a bowl of water. The crown displaced more wa ter and was thus shown to be a fake. More im por tant, Ar chi me des dis cov ered the prin ci ple of buoy ancy: Wa ter pushes up on ob jects with a force equal to the amount of water the objects displace.

Fun Facts: When Archi me des discov ered the concept of buoyancy, he leapt form the bath and shouted the word he made famous: “Eureka!” which means “I found it!” That word became the motto of the state of Cali - fornia after the first gold rush min ers shouted that they had found gold.

More to Ex plore

More to Explore: Allen, Pamela. Mr. Ar chi me des Bath. London: Garden ers Books, 1998. Ben dick, Jeanne. Archi me des and the Door to Science. New York: Bethle hem Books, 1995. Gow, Mary. Ar chi me des: Math e mat i cal Ge nius of the An cient World. Berkeley Heights, NJ: Enslow Publish ers, 2005. Heath, Tom. The Works of Archi me des: Edited in Modern Nota tion. Dover, DE: Ad a- mant Me dia Cor po ra tion, 2005. Stein, Sherman. Archi me des: What Did He Do Be sides Cry Eureka? Wash ing ton, DC: The Math e mat i cal As so ci a tion of Amer ica, 1999. Zannos, Susan. The Life and Times of Archi me des . Hockessin, DE: Mitchell Lane Pub - lish ers, 2004. The Sun Is the Center of the Universe

The Sun Is the Center of the Universe THE SUN IS THE CEN TER OF THE UNI VERSE Year of Dis cov ery: A.D. 1520

What Is It? The sun is the center of the universe and the earth rotates around it. Who Dis cov ered It? Nicholaus Co per ni cus

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Coper ni cus measured and observed the planets and stars. He gathered, compiled, and com pared the ob ser va tions of doz ens of other as tron o mers. In so do ing Co per ni cus chal - lenged a 2,000-year-old belief that the earth sat motion less at the center of the universe and that planets, sun, and stars rotated around it. His work repre sents the begin ning point for our un derstand ing of the universe around us and of modern astronomy. He was also the first to use sci entific ob ser vation as the ba sis for the devel op ment of a sci entific theory. (Before his time logic and thought had been the basis for the ory.) In this way Co perni cus launched both the field of modern astron omy and mod ern scientific methods.

How Was It Discov ered?

How Was It Discov ered? In 1499 Coper ni cus gradu ated from the Univer sity of Bolo gna, It aly; was or dained a priest in the Catho lic Church; and returned to Poland to work for his uncle, Bishop Waczenrode, at the Frauenburg Ca thedral. Coper ni cus was given the top rooms in a cathe - dral tower so he could continue his as tronomy measurements. At that time people still be lieved a model of the universe cre ated by the Greek sci en tist, Ptolemy, more than 1,500 years ear lier. Accord ing to Ptol emy, the earth was the cen ter of the universe and never moved. The sun and planets revolved around the earth in great circles, while the dis tant stars perched way out on the great spher i cal shell of space. But care ful mea sure ment of the movement of planets didn’t fit with Ptolomy’s model. So astron o mers modi fied Ptolemy’s universe of circles by adding more circles within cir cles, or epi-cir cles. The model now claimed that each planet trav eled along a small cir cle (epi-circle) that rolled along that planet’s big orbital circle around the earth. Cen tury af ter century, the errors in even this model grew more and more ev i dent. More epi-cir cles were added to the model so that planets moved along epi-circles within epi-circles.

5 6 The Sun Is the Center of the Universe

Coper ni cus hoped to use “modern” (sixteenth-cen tury) technol ogy to improve on Ptol- emy’s mea sure ments and, hope fully, elimi nate some of the epi-circles. For almost 20 years Coper ni cus painstak ingly measured the posi tion of the planets each night. But his ta bles of findings still made no sense in Ptolemy’s model. Over the years, Coper ni cus be gan to won der what the movement of the planets would look like from another moving planet. When his calcu la tions based on this idea more accu - rately predicted the plan ets’ ac tual movements, he began to won der what the motion of the planets would look like if the earth moved. Imme di ately, the logic of this notion became apparent. Each planet appeared at differ ent dis tances from the earth at differ ent times throughout a year. Co per ni cus re al ized that this meant Earth could not lie at the cen ter of the plan ets’ cir cu lar paths. From 20 years of obser va tions he knew that only the sun did not vary in appar ent size over the course of a year. This meant that the dis tance from Earth to the sun had to always re main the same. If the earth was not at the cen ter, then the sun had to be. He quickly cal cu - lated that if he placed the sun at the uni verse’s center and had the earth orbit around it, he could completely elimi nate all epi-circles and have the known planets travel in simple circles around the sun. But would anyone believe Coper ni cus’s new model of the universe? The whole world—and es pecially the all-power ful Catho lic Church—believed in an Earth-centered universe. For fear of retri bu tion from the Church, Coper ni cus dared not release his findings during his lifetime. They were made public in 1543, and even then they were consis tently scorned and ridi culed by the Church, astron o mers, and univer si ties alike. Finally, 60 years later, first Johannes Kepler and then Gali leo Galilei proved that Copernicus was right.

Fun Facts: Approx i mately one million Earths can fit inside the sun. But that is slowly changing. Some 4.5 pounds of sunlight hit the earth each sec ond.

More to Ex plore

More to Explore More to Explore Crowe, Mi chael. The o ries of the World from An tiq uity to the Co per ni can Rev o lu tion. New York: Do ver, 1994. Dreyer, J. A His tory of Astron omy from Thales to Kepler. New York: Do ver, 1998 Fradin, Dennis. Nicolaus Coper ni cus: The Earth Is a Planet. New York: Mondo Pub- lish ing, 2004. Goble, Todd. Nicolaus Coper ni cus and the Founding of Mod ern Astornomy. Greens - boro, NC: Morgan Reynolds, 2003. Knight, David C. Co per ni cus: Ti tan of Mod ern As tron omy. New York: Franklin Watts, 1996 Vollman, William. Uncentering the Earth: Co perni cus and the Revo lutions of the Heav enly Spheres. New York: W. W. Norton, 2006. Hu man Anat omy

Hu man Anat omy Hu man Anat omy Year of Dis cov ery: 1543

What Is It? The first sci en tific, accu rate guide to hu man anat omy. Who Dis cov ered It? Andreas Vesalius

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The human anatomy refer ences used by doctors through the year A.D. 1500 were actu ally based mostly on ani mal studies, more myth and error than truth. Andreas Vesalius was the first to insist on dissec tions, on exact physi o log i cal exper i ment and direct obser vation—sci en tific meth ods—to create his anatomy guides. His were the first reli able, ac curate books on the struc ture and workings of the human body. Versalius’s work de molished the long-held re liance on the 1,500-year-old ana tom i cal work by the early Greek, Galen, and marked a perma nent turn ing point for medi cine. For the first time, actual ana tom i cal fact re placed con jec ture as the ba sis for medical profession.

How Was It Discov ered?

How Was It Discov ered? Andreas Vesalius was born in Brussels in 1515. His fa ther, a doctor in the royal court, had collected an excep tional medi cal library. Young Vesalius poured over each volume and showed immense curi os ity about the function ing of living things. He often caught and dissected small an i mals and insects. At age 18 Vesalius traveled to Paris to study medi cine. Physi cal dissec tion of ani mal or human bodies was not a common part of accepted medi cal study. If a dissec tion had to be performed, profes sors lectured while a barber did the actual cutting. Anatomy was taught from the drawings and translated texts of Galen, a Greek doctor whose texts were written in 50 B.C. Vesalius was quickly recog nized as brilliant but arro gant and argu men ta tive. During the second dissec tion he attended, Vesalius snatched the knife from the barber and demon - strated both his skill at dissec tion and his knowl edge of anat omy, to the amaze ment of all in attendance. As a medi cal student, Vesalius became a ringleader, luring his fellow students to raid the boneyards of Paris for skel etons to study and graveyards for bodies to dissect. Vesalius regu larly braved vicious guard dogs and the gruesome stench of Paris’s mound of Monfaucon (where the bodies of exe cuted crimi nals were dumped) just to get his hands on freshly killed bodies to study.

7 8 Human Anatomy

In 1537 Vesalius gradu ated and moved to the Univer sity of Padua (Italy), where he began a long se ries of lec tures—each cen tered on ac tual dis sec tions and tis sue ex per i ments. Students and other profes sors flocked to his classes, fasci nated by his skill and by the new real ity he uncov ered—mus cles, arter ies, nerves, veins, and even thin structures of the human brain. This series culmi nated in Jan u ary 1540, with a lecture he presented to a packed theater in Bolo gna, Italy. Like all other medi cal students, Versalius had been trained to believe in Galen’s work. However, Vesalius had long been troubled because so many of his dissec - tions re vealed ac tual struc tures that dif fered from Galen’s descriptions. In this lecture, for the first time in pub lic, Vesalius revealed his evi dence to discredit Galen and to show that Galen’s de scriptions of curved hu man thighbones, heart chambers, segmented breast bones, etc., better matched the anat omy of apes than humans. In his lecture, Vesalius de tailed more than 200 dis crep an cies be tween ac tual hu man anat omy and Galen’s descrip tions. Time after time, Vesalius showed that what every doctor and surgeon in Europe relied on fit better with apes, dogs, and sheep than the human body. Galen, and every medi cal text based on his work, were wrong. Vesalius stunned the local medi cal commu nity with this lec ture. Then he secluded himself for three years pre paring his de tailed anatomy book. He used mas ter artists to draw what he dis sected—blood vessels, nerves, bones, organs, muscles, ten dons, and brain. Vesalius completed and published his magnif i cent anat omy book in 1543. When medical profes sors (who had taught and believed in Galen their entire lives) received Vesalius’s book with skepti cism and doubt, Vesalius flew into a rage and burned all of his notes and studies in a great bonfire, swearing that he would never again cut into human tissue. Luckily for us, his published book survived and became the stan dard anatomy text for over 300 years.

Fun Facts: The av erage human brain weighs three pounds and con tains 100 bil lion brain cells that con nect with each other through 500 trillion dendrites! No wonder it was hard for Vesalius to see indi vid ual neurons.

More to Ex plore

More to Explore More to Explore More to Explore O’Mal ley, C. Andreas Vesalius of Brussels. Novato, CA: Jeremy Norman Co., 1997. Persaud, T. Early His tory of Human Anatomy: From An tiquity to the Be ginning of the Mod ern Era. London: Charles C. Thomas Pub lishers, 1995. Saunders, J. The Illus tra tions from the Works of Andreas Vesalius of Brussels. New York: Do ver, 1993. Srebnik, Her bert. Concepts in Anat omy. New York: Springer, 2002. Tarshis, Jerome. Andreas Vesalius: Father of Modern Anatomy . New York: Dial Press, 1999. Vesalius, Andreas. On the Fabric of the Human Body. Novato, CA: Jeremy Norman, 1998. The Law of Fall ing Ob jects

The Law of Falling Objects The Law of Falling Objects Year of Dis cov ery: 1598

What Is It? Ob jects fall at the same speed re gard less of their weight. Who Dis cov ered It? Ga li leo Galilei

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? It seems a simple and obvi ous discov ery. Heavier objects don’t fall faster. Why does it qual ify as one of the great dis cov er ies? Be cause it ended the prac tice of sci ence based on the ancient Greek theo ries of Aris totle and Ptolemy and launched modern science. Gali leo’s discov ery brought physics into the Renais sance and the modern age. It laid the founda tion for New ton’s dis cov er ies of uni ver sal grav i ta tion and his laws of mo tion. Ga li leo’s work was an es sential building block of modern physics and engineering.

How Was It Discov ered?

How Was It Discov ered? Gali leo Galilei, a 24-year-old mathe mat ics pro fessor at the Univer sity of Pisa, Italy, often sat in a local cathe dral when some nagging problem weighed on his mind. Lamps gently swung on long chains to illu mi nate the cathe dral. One day in the summer of 1598, Ga li leo re al ized that those lamps al ways swung at the same speed. He de cided to time them. He used the pulse in his neck to mea sure the pe riod of each swing of one of the lamps. Then he timed a larger lamp and found that it swung at the same rate. He bor rowed one of the long tapers alter boys used to light the lamps and swung both large and small lamps more vigor ously. Over many days he timed the lamps and found that they always took exactly the same amount of time to travel through one complete arc. It didn’t matter how big (heavy) the lamp was or how big the arc was. Heavy lamps fell through their arc at the same rate as lighter lamps. Ga li leo was fas ci - nated. This obser vation contra dicted a 2,000-year-old corner stone of beliefs about the world. He stood before his class at the Univer sity of Pisa, Italy, holding bricks as if weighing and com paring them—a single brick in one hand and two bricks that he had cemented together in the other. “Gentle men, I have been watching pendu lums swing back and forth. And I have come to a conclu sion. Aris totle is wrong.”

9 10 The Law of Falling Objects

The class gasped, “Aris totle? Wrong?!” The first fact every schoolboy learned in beginning science was that the writings of the ancient Greek philos o pher, Aris totle, were the foun da tion of sci ence. One of Ar is totle’s cen tral the o rems stated that heavier ob jects fall faster be cause they weigh more. Gali leo climbed onto his desk, held the bricks at eye level, and let them fall. Thud! Both bricks crashed to the floor. “Did the heavier brick fall faster?” he demanded. The class shook their heads. No, it had not. They landed together. “Again!” cried Gali leo. His students were transfixed as Ga lileo again dropped the bricks. Crash! “Did the heavy brick fall faster?” No, again the bricks landed together. “Aris - totle is wrong,” de clared their teacher to a stunned cir cle of students. But the world was reluc tant to hear Gali leo’s truth. On seeing Gali leo’s brick demon - stration, friend and fel low mathe ma ti cian Ostilio Ricci ad mitted only that “This dou ble brick falls at the same rate as this sin gle brick. Still, I can not so easily be lieve Aris totle is wholly wrong. Search for another explanation.” Gali leo de cided that he needed a more dra matic, irre fut able, and public demon stra tion. It is believed (though not sub stan tiated) that, for this dem on stra tion, Ga lileo dropped a ten-pound and a one-pound cannon ball 191 feet from the top of the famed Leaning Tower of Pisa. Whether he actu ally dropped the cannon balls or not, the science discovery had been made.

Fun Facts: Speaking of falling objects, the highest speed ever reached by a woman in a speed skydiving compe ti tion is 432.12 kph (268.5 mph). Italian daredevil Lucia Bottari achieved this record-break ing veloc ity above Bottens, Swit zer land, on Sep tem ber 16, 2002, during the an nual Speed Skydiving World Cup.

More to Ex plore

More to Explor More to Explor More to Explore Aldrain, Buzz. Gali leo for Kids: His Life and Ideas. Chicago: Chicago Review Press, 2005. Atkins, Peter, Gali leo’s Finger: The Ten Great Ideas of Science. New York: Random House, 2004. Ben dick, Jeanne. Along Came Gali leo. San Luis Obispo, CA: Beauti ful Feet Books, 1999. Drake, Stillman. Ga li leo. New York: Hill and Wang, 1995. Fisher, Leon ard. Ga li leo. New York: Macmillan, 1998. Galilei, Ga li leo. Gali leo on the World Systems: A New Abridged Transla tion and Guide. Berke ley: Uni ver sity of Cal i for nia Press, 1997. MacHamer, Oeter, ed. The Cam bridge Com pan ion to Ga li leo. New York: Cambridge Uni ver sity Press, 1998. MacLachlan, James. Ga li leo Galilei: First Phys i cist. New York: Ox ford Uni versity Press, 1997. Sobel, Dava. Ga li leo’s Daugh ter. New York: Walker & Co., 1999. Plane tary Motion

Plan e tary Mo tion Plan e tary Mo tion Year of Dis cov ery: 1609

What Is It? The plan ets orbit the sun not in perfect cir cles, but in ellip ses. Who Dis cov ered It? Johannes Kepler

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Even after Coper ni cus simpli fied and corrected the structure of the solar system by discover ing that the sun, not the earth, lay at the center of it, he (like all astron o mers before him) assumed that the plan ets orbited the sun in perfect cir cles. As a re sult, errors con tinued to exist in the pre dicted position of the planets. Kepler discov ered the con cept of the ellipse and proved that planets actu ally follow slightly el lip tical orbits. With this dis cov ery, science was finally pre sented with an accu rate pictures of the posi tion and mechan ics of the solar system. After 400 years of vastly improved technol ogy, our image of how planets move is still the one Kepler created. We haven’t changed or corrected it one bit, and likely never will.

How Was It Discov ered?

How Was It Discov ered? For 2,000 years, as trono mers placed the earth at the center of the universe and assumed that all heavenly bodies moved in perfect circles around it. But predic tions using this system never matched ac tual mea sure ments. Sci en tists in vented epi-cir cles—small cir cles that the planets actu ally rolled around that, themselves, rolled around the great circu lar orbits for each planet. Still there were er rors, so sci en tists cre ated epi-circles on the epi-circles. Coper ni cus discov ered that the sun lay at the center of the so lar system, but still assumed that all planets traveled in per fect cir cles. Most epi-cir cles were elim i nated, but er - rors in plane tary plotting continued. Johannes Kep ler was born in Southern Germany in 1571, 28 years after the re lease of Co per ni cus’s dis cov ery. Kep ler suf fered through a trou bled up bring ing. His aunt was burned at the stake as a witch. His mother al most suf fered the same fate. The boy was of ten sick and had bad eyesight that glasses could not correct. Still, Kep ler en joyed a brilliant— but again troubled—university career. In 1597 he took a po sition as an as sis tant to Tycho Brahe, famed German astron o mer. For decades Tycho had been mea suring the posi tion of the planets (es pecially Mars) with far greater pre cision than any other Euro pean astron o mer. When Tycho died in 1601 he left all his notes and tables of plane tary readings to Kepler.

11 12 Plane tary Motion

Kep ler re jected the epi-cir cle on epi-cir cle model of how plan ets moved and de cided to work out an orbit for Mars that best fit Tycho’s data. It was still danger ous to sug gest that the sun lay at the center of the so lar system. The all-pow erful Catho lic Church had burned Friar Giordano Bruno at the stake for believ ing Coper ni cus. No other scien tist had dared come forth to support Coper ni cus’s radi cal notion. Still, Kepler was deter mined to use Co- perni cus’s orga ni za tion for the universe and Tycho’s data to make sense of the planets. Kepler tried many ideas and math emat ical approaches that didn’t work. His bad eyesight prevented him from making his own astro nom i cal sightings. He was forced to rely en- tirely on Tycho’s exist ing measure ments. In bitter frustra tion, he was finally driven to con sider what was—at the time—unthink able: plan etary or bits that were n’t per fect cir cles. Nothing else explained Tycho’s readings for Mars. Kep ler found that el lip ses (elon gated cir cles) fit far better with the ac cu mu lated read - ings. Yet the data still didn’t fit. In desper a tion, Kep ler was forced to consider something else that was also unthink able at that time: maybe the planets didn’t orbit the sun at a constant speed. With these two revo lu tion ary ideas Kepler found that el lip tical orbits fit perfectly with Tycho’s mea sured plan e tary mo tion. El lip ti cal or bits be came Kep ler’s first law. Kep ler then added his Sec ond Law: each planet’s speed altered as a function of its dis tance from the sun. As a planet flew closer, it flew faster. Kepler published his dis cover ies in 1609 and then spent the next 18 years calcu lat ing detailed ta bles of plane tary mo tion and posi tion for all six known plan ets. This was also the first prac tical use of loga rithms, invented by Scots man John Napier during the early years of Kep ler’s ef fort. With these ta bles of cal cu la tions (which ex actly matched mea sured plan e- tary posi tions) Kepler proved that he had discovered true planetary motion.

Fun Facts: Pluto was called the ninth planet for 75 years, since its discov ery in 1930. Pluto’s or bit is the least circu lar (most ellip ti cal) of all plan ets. At its farthest, it is 7.4 bil lion km from the sun. At its nearest it is only 4.34 bil lion km away. When Pluto is at its clos est, its orbit actu ally slips inside that of Neptune. For 20 years out of every 248, Pluto is actu - ally closer to the sun than Neptune is. That occurred from 1979 to 1999. For those 20 years Pluto was actu ally the eighth planet in our solar system and Nep tune was the ninth!

More to Ex plore

More to Explore More to Explore More to Explore Cas per, Max. Kep ler. New York: Do ver, 1993. Dreyer, J. A His tory of Astron omy from Thales to Kepler. New York: Do ver, 1993. Huff, Toby. The Rise of Early Modern Science . New York: Cambridge Univer sity Press, 1993. North, John. The Norton His tory of Astron omy and Cosmol ogy . New York: Norton, 1995. Stephenson, Bruce. Kep ler’s Phys i cal As tron omy. Princeton, NJ: Princeton Univer sity Press, 1997. Ju pi ter’s Moons

Ju pi ter’s Moons JU PI TER’ S MOONS Year of Dis cov ery: 1610

What Is It? Other planets (besides Earth) have moons. Who Dis cov ered It? Ga li leo Galilei

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Gali leo discov ered that other planets have moons and thus extended human under stand - ing beyond our own planet. His careful work with the telescopes he built launched modern astron omy. His dis cov er ies were the first as tro nom i cal dis cov er ies us ing the tele scope. Gali leo proved that Earth is not unique among planets of the uni verse. He turned specks of light in the night sky into fas cinat ing spheri cal ob jects—into places—rather than pinpricks of light. In so doing, he proved that Polish astron o mer Nicholaus Coper ni cus had been right when he claimed that the sun was the center of the solar system. With his sim ple telescope Gali leo single-handedly brought the so lar system, galaxy, and greater universe within our grasp. His telescope provided vistas and under stand ing that did not exist be fore and could not ex ist without the telescope.

How Was It Discov ered?

How Was It Discov ered? This was a discov ery made pos sible by an inven tion—the tele scope. Gali leo saw his first telescope in late 1608 and instantly recog nized that a more power ful telescope could be the answer to the prayers of ev ery astron o mer. By late 1609 Gali leo had produced a 40-power, two-lens tele scope. That 1609 tele scope was the first prac ti cal tele scope for sci en tific use. A paper by Johannes Kepler de scribing the or bits of the plan ets convinced Gali leo to believe the theory of Polish astron o mer Nicholaus Coper ni cus, who first claimed that the sun was the center of the universe, not the earth. Believ ing Coper ni cus was a danger ous thing to do. Friar Giordano Bruno had been burned at the stake for be lieving Coper ni cus. Gali leo decided to use his new telescope to prove that Coper ni cus was right by more accu - rately charting the motion of the planets. Gali leo first turned his telescope on the moon. There he clearly saw mountains and valleys. He saw deep craters with tall, jagged rims slicing like ser rated knives into the lu nar sky. The moon that Ga lileo saw was radi cally differ ent from the perfectly smooth sphere that Aris totle and Ptol emy said it was (the two Greek astron o mers whose teachings still formed the basis of all sci ence in 1610). Both the all-pow erful Catho lic Church and every univer sity and sci entist in Europe believed Aristotle and Ptolemy.

13 14 Jupi ter’s Moons

In one night’s viewing of the moon’s surface through his telescope, Gali leo proved Ar- is totle wrong—again. The last time Ga li leo’s ob ser va tions had con tra dicted Ar is totle’s teachings, Gali leo had been fired from his teaching posi tion for being right when he proved that all ob jects fall at the same rate re gard less of their weight. Gali leo next aimed his telescope at Jupi ter, the biggest planet, planning to carefully chart its motion over several months. Through his telescope (the name is a combi na tion of the Greek words for “distant” and “looking”) Gali leo saw a magni fied view of the heavens no human eye had ever seen. He saw Ju piter clearly, and, to his amazement, he found moons circling the gi ant planet. Aris totle had said (and all scien tists believed) that Earth was the only planet in the universe that had a moon. Within days, Gali leo discov ered four of Jupi - ter’s moons. These were the first discovered moons other than our own. Aris totle was wrong again. Still, old beliefs do not die eas ily. In 1616 the Council of Car dinals forbade Gali leo ever again to teach or promote Coper ni cus’s theo ries. Many senior church offi cials refused to look through a telescope, claiming it was a magi cian’s trick and that the moons were in the telescope. When Ga lileo ignored their warning, he was summoned to Rome by the Church’s all-pow er ful In qui si tion. A gru el ing trial fol lowed. Ga li leo was con demned by the Church and forced to publicly recant his views and findings. He was placed under house ar rest for the rest of his life, dying in 1640 without hearing even one voice other than his own pro- claim that his discov er ies were true. The Church did not rescind the con demna tion of Gali - leo and his discov er ies until Octo ber 1992, 376 years after they incorrectly condemned him.

Fun Facts: Gali leo would have been aston ished to learn that Jupi ter re- sembles a star in compo si tion. In fact, if it had been about 80 times more massive, it would have been clas si fied as a star rather than a planet.

More to Ex plore

More to Explore More to Explore More to Explore Aldrain, Buzz. Gali leo for Kids: His Life and Ideas. Chicago: Chicago Review Press, 2005. Atkins, Pe ter, Gali leo’s Finger: the Ten Great Ideas of Science. New York: Random House, 2004. Ben dick, Jeanne. Along Came Gali leo. San Luis Obispo, CA: Beauti ful Feet Books, 1999. Drake, Stillman. Ga li leo. New York: Hill and Wang, 1995. Fisher, Leonard. Ga li leo. New York: Macmillan, 1998. Galilei, Ga li leo. Gali leo on the World Systems: A New Abridged Transla tion and Guide. Berke ley: Uni ver sity of Cal i for nia Press, 1997. MacHamer, Oeter, ed. The Cam bridge Com pan ion to Ga li leo. New York: Cambridge Uni ver sity Press, 1998. MacLachlan, James. Ga li leo Galilei: First Phys i cist. New York: Ox ford Uni versity Press, 1997. Sobel, Dava. Ga li leo’s Daugh ter. New York: Walker & Co., 1999. Human Circu la tory System

Hu man Cir cu la tory Sys tem Hu man Cir cu la tory Sys tem Year of Dis cov ery: 1628

What Is It? The first complete under stand ing of how arter ies, veins, heart, and lungs func tion to form a single, complete circu la tory sys tem. Who Dis cov ered It? Wil liam Harvey

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The hu man cir cu la tory sys tem rep re sents the vir tual def i ni tion of life. No sys tem is more crit ical to our exis tence. Yet only 400 years ago, no one under stood our circu la tory system. Many seri ously thought that the thump ing inside the chest was the voice of the con- science trying to be heard. Most thought that blood was created in the liver and consumed by the mus cles. Some still thought that arter ies were filled with air. William Harvey discov ered the actual function of the major ele ments of the circu la tory sys tem (heart, lungs, ar ter ies, and veins) and cre ated the first complete and ac cu rate pic ture of human blood circu la tion. Harvey was also the first to use the scien tific method for bio - logi cal studies. Every scien tist since has followed his exam ple. Harvey’s 1628 book repre - sents the beginning of modern physiology.

How Was It Discov ered?

How Was It Discov ered? Through the sixteenth century, doctors relied on the 1,500-year-old writings of the Greek physi cian Galen, who said that food was converted into blood in the liver and was then con sumed by the body for fuel. Most agreed that the blood that flowed through arter ies had no connec tion with the blood that flowed through veins. William Harvey was born in 1578 in England and received med ical train ing at Ox ford. He was invited to study at Padua Univer sity in Italy, the acknowl edged medi cal center of Europe. When Harvey returned to England in 1602, he married the daughter of Queen Eliza - beth’s doctor, was ap pointed a phy sician in the court of King James I, and was then appointed personal phy sician to King Charles I in 1618. While serving the English kings, Harvey focused his studies on veins and arter ies. He con ducted ex ten sive ex per i ments with an i mals and hu man corpses. Dur ing these dis sections, he dis covered the series of flap valves that exist throughout the veins. He was not the first to find these valves, but he was the first to note that they always directed blood flow toward the heart. Blood flowed in veins only from the arms, legs, and head back to the heart.

15 16 Hu man Cir cu la tory Sys tem

He be gan a series of ani mal exper i ments in which he tied off a single artery or vein to see what hap pened. Sometimes he clamped an ar tery and later re leased it to see where this surge of blood would go. He did the same with veins, clamping a vein and then releas ing it. Some times he clamped both vein and ar tery and then re leased one at a time. These ex per i - ments proved that arter ies and veins were connected into a single circu la tory system and that blood always flowed from arteries to veins. Harvey turned to the heart it self and soon re al ized that the heart acted as a mus cle and pushed blood out to lungs and out into ar teries. Follow ing blood as it flowed through vari - ous ani mals, Harvey saw that blood was not consumed, but circu lated over and over again through the system, carry ing air and nourish ment to the body. By 1625 Harvey had discov ered an al most complete picture of the circu la tory sys tem. He faced two problems. First, he couldn’t figure out how blood got from an artery across to a vein, even though his ex peri ments proved that it did. (Harvey had no mi croscope and so could n’t see blood ves sels as small as cap il lar ies. By 1670—three years af ter Harvey’s death—Ital ian Marcello Malpighi had dis cov ered cap il lar ies with a mi cro scope, thus com - pleting Harvey’s circulatory system.) The second problem Harvey faced was his fear of mob reac tions, Church condem na - tion when he said that the heart was just a muscu lar pump and not the house of the soul and conscious ness, and the press (scribes). He was afraid he’d lose his job with the king. In 1628 Harvey found a small German publisher to publish a thin (72-page) summary of his work and discov er ies. He published it in Latin (the language of science), hoping no one in Eng - land would read it. News of Harvey’s book raced across Europe and made him instantly noto ri ous. He lost many pa tients, who were shocked by his claims. But Harvey’s sci ence was care ful and ac - curate. By 1650 Harvey’s book had become the accepted textbook on the circu la tory system.

Fun Facts: Ameri cans donate over 16 million pints of blood each year. That’s enough blood to fill a swimming pool 20 feet wide, 8 feet deep, and one-third of a mile long!

More to Ex plore

More to Explore Curtis, R. Great Lives: Med i cine. New York: Charles Scribner’s Sons Books for Young Readers, 1993. Harvey, William. On the Motion of the Heart and Blood in An imals . Whitefish, MT: Kessinger Pub lish ing, 2005. Power, D’Arcy. William Harvey: Mas ter of Medi cine. Whitefish, MT: Kessinger, 2005. Shackleford, Joel. William Harvey and the Mechan ics of the Heart. New York: Oxford Uni ver sity Press, 2003. Wyatt, Her vey. Wil liam Harvey: 1578 to 1657. Whitefish, MT: Kessinger, 2005. Yount, Lisa. Wil liam Harvey: Discov erer of How Blood Circu lates . Berke ley Heights, NJ: Enslow, 1998. Air Pres sure

Air Pressure Air Pressure Year of Dis cov ery: 1640

What Is It? Air (the atmo sphere) has weight and presses down on us. Who Dis cov ered It? Evangelista Torricelli

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? It is a simple, seem ingly obvi ous notion: air has weight; the atmo sphere presses down on us with a real force. However, humans don’t feel that weight. You aren’t aware of it because it has al ways been part of your world. The same was true for early sci en tists, who never thought to con sider the weight of air and atmosphere. Evangelista Torricelli’s discov ery began the seri ous study of weather and the atmo - sphere. It launched our under stand ing of the atmo sphere. This discov ery helped lay the founda tion for Newton and others to develop an un derstand ing of gravity. This same reve la tion also led Torricelli to discover the con cept of a vacuum and to invent the ba rom e ter—the most ba sic, fun da men tal in stru ment of weather study.

How Was It Discov ered?

How Was It Discov ered? On a clear Octo ber day in 1640, Gali leo conducted a suction-pump exper i ment at a pub lic well just off the market plaza in Florence, Italy. The famed Italian scien tist lowered a long tube into the well’s murky water. From the well, Gali leo’s tube draped up over a wooden cross-beam three meters above the well’s wall, and then down to a hand-powered pump held by two assis tants: Evangelista Torricelli, the 32-year-old the son of a wealthy mer chant and an aspir ing scien tist, and Giovanni Baliani, another Italian physicist. Torricelli and Baliani pumped the pump’s wooden handle bar, slowly sucking air out of Gali leo’s tube, pulling water higher into the tube. They pumped until the tube flattened like a run-over drinking straw. But no matter how hard they worked, water would not rise more than 9.7 me ters above the well’s wa ter level. It was the same in every test. Gali leo proposed that—somehow—the weight of the water column made it collapse back to that height. In 1643, Torricelli re turned to the suction pump mystery. If Ga lileo was correct, a heavier liquid should reach the same criti cal weight and collapse at a lower height. Liquid mer cury weighted 13.5 times as much as water. Thus, a column of mercury should never rise any higher than 1/13.5 the height of a water column, or about 30 inches.

17 18 Air Pres sure

Torricelli filled a six-foot glass tube with liquid mercury and shoved a cork into the open end. Then he inverted the tube and submerged the corked end in a tub of liquid mercury before he pulled out the stopper. As he expected, mercury flowed out of the tube and into the tub. But not all of the mercury ran out. Torricelli measured the height of the remain ing mercury column—30 inches, as expected. Still, Torricelli suspected that the mystery’s true answer had something to do with the vacuum he had cre ated above his col umn of mercury. The next day, with wind and a cold rain lash ing at the win dows, Torricelli repeated his exper i ment, planning to study the vacuum above the mercury. However, on this day the mer cury column only rose to a height of 29 inches. Torricelli was per plexed. He had ex pected the mer cury to rise to the same height as yester day. What was differ ent? Rain beat on the windows as Torricelli pondered this new wrin kle. What was dif fer ent was the at mo sphere, the weather. Torricelli’s mind latched onto a revo lu tion ary new idea. Air, itself, had weight. The real answer to the suction pump mystery lay not in the weight of the liquid, nor in the vac uum above it, but in the weight of the atmosphere pushing down around it. Torricelli real ized that the weight of the air in the atmo sphere pushed down on the mercury in the tub. That pressure forced mer cury up into the tube. The weight of the mercury in the tube had to be exactly equal to the weight of the atmo sphere pushing down on the mercury in the tub. When the weight of the atmo sphere changed, it would push down ei ther a little bit more or a little bit less on the mer cury in the tub and drive the col umn of mercury in the tube either a little higher or a lit tle lower. Changing weather must change the weight of the atmo - sphere. Torricelli had dis covered atmo spheric pressure and a way to measure and study it.

Fun Facts: Home barom e ters rarely drop more than 0.5 inch of mercury as the weather changes from fair to stormy. The great est pres sure drop ever recorded was 2.963 inches of mercury, measured inside a South Da- kota tor nado in June 2003.

More to Ex plore

More to Explore Asimov, Isaac. Asimov’s Chronol ogy of Science and Dis covery . New York: Harper & Row, 1989. Clark, Donald. En cy clo pe dia of Great In ven tors and Dis cov er ies. London: Marshall Caven dish Books, 1991. Ha ven, Kend all. Mar vels of Sci ence. Englewood, CO: Librar ies Unlim ited, 1994. Macus, Rebecca. Ga li leo and Ex per i men tal Sci ence. New York: Franklin Watts, 1991. Middleton, W. E. The History of the Barom e ter. New Brunswick, NJ: Johns Hopkins Uni ver sity Press, 2003. Boyle’s Law

Boyle’s Law Boyle’s Law Year of Discov ery: 1650

What Is It? The volume of a gas is inversely propor tional to the force squeez- ing it. Who Dis cov ered It? Robert Boyle

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The concept Robert Boyle discov ered (now called Boyle’s Law) laid the founda tion for all quan ti tative study and chem i cal analy sis of gasses. It was the first quan ti tative for- mula to describe the behav ior of gasses. Boyle’s Law is so basic to under stand ing chemis try that it is taught to ev ery student in beginning chemistry classes. A genius ex peri menter, Boyle also proved that gasses were made of atoms—just like solids. But in a gas, the atoms are spread far apart and discon nected so that they can be squeezed tighter. Through these exper i ments Boyle helped convince the scien tific world that atoms ex isted—an is sue still de bated 2,000 years af ter their ex is tence was first pro - posed by Democritus in 440 B.C.

How Was It Discov ered?

How Was It Discov ered? Robert Boyle was the son of an earl and a member of the British Scien tific Soci ety. During a 1662 so ciety meet ing, Robert Hooke read a pa per de scribing a French ex peri ment on the “springi ness of air.” The char acter is tics of air were of great in ter est to scien tists in the seventeenth century. French scien tists built a brass cylin der fitted tightly with a piston. Several men pushed down hard on the piston, compress ing the air trapped below. Then they let go. The piston sprang back up, but not all the way back up. No matter how often the French tried this ex- peri ment, the piston never bounced all the way back up. The French claimed this proved that air was not perfectly springy. Once compressed, it stayed slightly compressed. Robert Boyle claimed that the French exper i ment proved nothing. Their pis ton, he said, was too tight to bounce all the way back up. Others argued that, if they made the piston looser, air would leak around the edges and ruin the exper i ment. Boyle promised to create a perfect piston that was neither too tight nor too loose. He also claimed that his per fect piston would prove the French wrong.

19 20 Boyle’s Law

Two weeks later Robert Boyle stood before the soci ety with a large glass tube that he had shaped into a lopsided “U.” One side of the “U” rose over three feet high and was skinny. The other side was short and fat. The short side was sealed at the top. The tall, skinny side was open. Boyle poured liq uid mercury into his tube un til it covered the bottom of the “U” and rose just a little in both sides. A large pocket of air was trapped above this mercury in the short fat side. A piston, Boyle explained, was any de vise that com pressed air. Since his used mer cury to compress air, there would be no friction to affect the results—as had been true in the French experiment. Boyle recorded the glass piston’s weight and etched a line in the glass where mercury met the trapped air pocket. Boyle trickled liquid mercury down the long neck of the tall side of his piston until he had filled the neck. Mercury now rose well over halfway up the short side. The trapped air had been squeezed to less than half of its origi nal volume by the weight and force of mercury. Boyle drew a second line on the short chamber to mark the new level of mercury inside—mark ing the compressed vol ume of trapped air. He then drained mercury through a valve at the bottom of the “U” until the glass pis ton and mercury weighed exactly the same as they had at the be ginning. The mer cury level returned to its exact starting line. The trapped air had sprung back exactly to where it started. Air was perfectly springy. The French were wrong. Boyle was right. Robert Boyle contin ued the exper i ments with his funny glass piston and noticed something quite remark able. When he dou bled the pres sure (weight of mercury) on a trapped body of air, he halved its volume. When he tripled the pres sure, the air’s volume was reduced to one-third. The change in volume of air when com pressed was always propor tional to the change in the pres sure squeez ing that air. He cre ated a sim ple math e mat i cal equa tion to describe this propor tion al ity. Today we call it “Boyle’s Law.” No other con cept has been more useful in under stand ing and us ing gasses to serve the needs of humankind.

Fun Facts: Ocean og ra pher Syl via Earle set the women’s depth re cord for solo diving (1,000 meters or 3,281 feet). Accord ing to the concept Boyle discov ered, pres sure at that depth is over 100 times what it is at the sur face!

More to Ex plore

More to Explore Boyle, Robert. The Skepti cal Chemist . New York: Do ver, 2003. Hall, Marie. Rob ert Boyle on Nat u ral Phi los o phy. Bloomington: In di ana Uni ver sity Press, 1995. Hunter, Michael. Rob ert Boyle Re con sid ered. New York: Cambridge Univer sity Press, 2003. Irwin, Keith. The Romance of Chemis try. New York: Viking Press, 1996. Tiner, John. Robert Boyle: Trailblazer of Science. Fenton, MI: Mott Media, 1999. Wojcik, Jan. Robert Boyle and the Limits of Reason. New York: Cambridge Univer - sity Press, 2003. The Ex is tence of Cells

The Exis tence of Cells THE EXISTENCE OF CELLS Year of Dis cov ery: 1665

What Is It? The cell is the basic building block of all living organ isms. Who Dis cov ered It? Robert Hooke

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The cell is the basic unit of anatomy. Countless millions of cells build living plants and ani mals. The functions of a body can be studied by studying indi vid ual cells. Just as the dis - covery of the mol ecule and atom al lowed sci entists to better under stand chem ical substances, Hooke’s discov ery of the cell has allowed biol o gists to better understand living organisms. Hooke’s work with a micro scope opened the public’s eyes to the micro scopic world just as Gali leo’s work with the telescope opened their eyes to a vast and wondrous universe. Hooke’s work and dis cover ies mark the mo ment when micros copy came of age as a scien - tific discipline.

How Was It Discov ered?

How Was It Discov ered? Robert Hooke was a most inter est ing fel low. Weak and sickly as a child, Hooke’s parents never bothered to edu cate him because they didn’t think he would survive. When Hooke was still alive at age 11, his father be gan a halfhearted, homeschool edu ca tion. When Hooke was 12, he watched a portrait painter at work and decided, “I can do that.” Some initial sketches showed that he was good at it. The next year Hooke’s fa ther died, leaving Hooke a pal try inher i tance of only £100. Hooke de cided to use the money to ap prentice himself to a painter, but quickly learned that the paint fumes gave him ter ri ble headaches. He used his money in stead to en ter West minster school. On one of his first days there, Hooke listened to a man play the school organ and thought, “I can do that.” Hooke soon proved that he was good at it and learned both to play and to serve as a choirmas ter. Un for tu nately, the new Eng lish pu ri tan i cal gov ern ment banned such fri vol ity as church choirs and music. Hook’s money had been wasted. Not knowing what else to do, Hooke hired him self out as a servant to rich science students at nearby Ox ford Uni versity. Hooke was fasci nated with science and again thought, “I can do that.” As it turns out, he was excep tion ally good at it. His servi tude at Oxford (mostly to Robert Boyle) was the start of one of the most produc tive science careers in Eng lish history. Hooke soon de veloped an ex cel lent rep u ta tion as a builder and as an experimenter. 21 22 The Ex istence of Cells

Micro scopes were invented in the late 1590s. By 1660 only a few had been built that were able to mag nify ob jects 100 times nor mal size. As mi cro scopes became more pow er - ful, they main tained focus on only a tiny sliver of space and were increas ingly more diffi cult to focus and to use. Hooke was hired onto the staff of the Royal Soci ety (an early English scien tific orga ni - zation) in 1660 and soon began a long series of micro scopic studies. By 1662 he had helped design a 300-power mi croscope, which he used to exam ine the micro scopic structure of common objects. Using this micro scope and his artis tic talent, Hooke created the first detailed stud ies of the micro scopic world, ren dering with life like accu racy the con tours of a fly’s compound eyes, the structure of a feather, and a butter fly’s wing. He also drew and identified a series of microscopic bugs. In 1664 Hooke turned his micro scope onto a thin sheet of dried cork and found it to be composed of a tightly packed pat tern of tiny rectan gu lar holes. Actu ally, cork has large, open cells. That’s why Hooke was able to see them at all. The cells of other plants and ani - mal tissue he studied were all too small to be seen through his micro scopes. Hooke called these holes cells (the Latin word for small chambers that stand in a row—as in prison cells). These cells were empty be cause the cork was dead. Hooke cor - rectly suspected that, while living, these had been filled with fluid. The name “cell” stuck. More im portant, the concept galva nized biol o gists. The living world was constructed of countless tiny cells stacked together like bricks in a wall. The entire field of biol ogy shifted toward a study of cell structure and cell function.

Fun Facts: Cell biol ogy is the only science in which multi pli cation means the same thing as divi sion.

More to Ex plore

More to Explore Dyson, James. A His tory of Great Inven tions . New York: Carroll & Graf Pub lishers, 2001. Headstrom, Rich ard. Ad ven tures with a Mi cro scope. Mineola, NY: Dover Publi ca - tions, 1997. Inwood, Stephen. The For got ten Ge nius: The Bi og ra phy of Rob ert Hooke. San Fran- cisco: Mac Adam/Cage Pub lish ing, 2005. Jar dine, Lisa. The Curi ous Life of Robert Hooke. New York: HarperPerennial, 2005. Oxlade, Chris. The World of Micro scopes . New York: Usborne Books, 1999. Suplee, Curt. Milestones of Sci ence. Wash ing ton, DC: Na tional Geo graphic So ci ety, 2000. Yenne, Bill. 100 Inven tions That Shaped World History . New York: Bluewood Books, 1998. Univer sal Gravi ta tion

Uni ver sal Grav i ta tion UNIVERSAL GRAVITATION Year of Dis cov ery: 1666

What Is It? Gravity is the attrac tive force exerted by all ob jects on all other ob jects. Who Dis cov ered It? Isaac New ton

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? By the early seven teenth century, many forces had been identi fied: friction, gravity, air re sis tance, elec tri cal, forces peo ple ex erted, etc. New ton’s math e mat i cal con cept of grav ity was the first step in joining these seemingly differ ent forces into a single, unified concept. An apple fell; peo ple had weight; the moon orbited Earth—all for the same rea son. New- ton’s law of gravity was a giant, simplifying concept. New ton’s con cept of, and equations for, grav ity stand as one of the most used con cepts in all science. Most of our physics has been built upon Newton’s concept of univer sal gravi - tation and his idea that gravity is a funda men tal prop erty of all matter.

How Was It Discov ered?

How Was It Discov ered? In 1666, Isaac Newton was a 23-year-old junior fellow at Trinity College in Cam- bridge. With his fair complex ion and long blond hair, many thought he still looked more like a boy. His small, thin stature and shy, sober ways rein forced that impres sion. His intense eyes and seem ingly per manent scowl pushed people away. In Lon don, the bu bonic plague rav aged a ter ri fied pop u la tion. Uni ver si ties were closed, and ea ger ac a dem ics like Isaac New ton had to bide their time in safe coun try es tates waiting for the plague to loosen its death grip on the city. It was a frightening time. In his isola tion, Newton was obsessed with a question: What held the moon circling the earth, and what held the earth in a captive orbit around the sun? Why didn’t the moon fall down to the earth? Why didn’t the earth fall down to the sun? In later years New ton swore that this story actu ally hap pened. As he sat in the or chard at his sis ter’s es tate, he heard the fa mil iar soft “thunk” of an ap ple fall ing to the grass-car- peted ground, and turned in time to see a second apple fall from an over hanging branch and bounce once before settling gently into the spring grass. It was certainly not the first apple Isaac Newton had ever seen fall to the ground, nor was there any thing at all unusual about its short fall. However, while it offered no answers to the perplexed young scien tist, the falling apple did present Isaac with an impor tant new ques tion, “The ap ple falls to Earth while the moon does not. What’s the differ ence between the apple and the moon?” 23 24 Uni ver sal Grav i ta tion

Next morning, under a clearing sky, Newton saw his young nephew playing with a ball. The ball was tied to a string the boy held tight in his fist. He swung the ball, slowly at first, and then faster and faster un til it stretched straight out. With a start New ton re al ized that the ball was ex actly like the moon. Two forces acted on the ball—its motion (driv ing it outward) and the pull of a string (holding it in). Two forces acted on the moon. Its motion and the pull of gravity—the same pull (force) that made the ap ple fall. For the first time, Newton consid ered the possi bil ity that gravity was a univer sal at- tractive force instead of a force that applied only to planets and stars. His deep belief in alchemy and its concept of the attrac tion of matter led him to postu late that gravi ta tional attrac tion force did not just apply to heavenly objects, but to all objects with any mass. Gravity pulled apples to earth, made rain fall, and held planets in their orbits around the sun. Newton’s discov ery of the concept of univer sal gravi ta tion was a major blow to the preva lent belief that the laws of nature on Earth were differ ent from those that ruled the heavens. New ton showed that the machin ery that ruled the universe and nature is simple. New ton devel oped univer sal gravi ta tion as a property of all matter, not just of planets and stars. Uni ver sal grav i ta tion and its math e mat i cal ex pres sion lie at the foun da tion of all modern phys ics as one of the most im portant principles in all science.

Fun Facts: The Flower of Kent is a large green va ri ety of ap ple. Ac cording to the story, this is the apple Isaac Newton saw falling to ground from its tree, in spir ing his dis cov ery of uni ver sal grav i ta tion.

More to Ex plore

More to Explore Christianson, Gale. Isaac Newton and the Scien tific Revo lu tion. New York: Ox ford Uni ver sity Press, 1996. Gale, Christeanson. In the Pres ence of the Creator: Isaac Newton and His Times. New York: Collier Macmillan, 1994. Gleick, James. Isaac New ton. New York: Vintage , 2004 Koestler, Arthur. The Sleepwalk ers: A History of Man’s Changing Vision of the Uni - verse. London: Hutch inson & Co., 1999. Maury, Jean. Newton: The Father of Modern Astron omy. New York: Harry Abrams, 1996. Peteson, Ivars. Newton’s Clock. New York: W. H. Freeman, 1995. White, Mi chael. Isaac Newton: The Last Sorcerer. Jackson, TN: Perseus Books, 1999. Fos sils

Fos sils FOSSILS Year of Dis cov ery: 1669

What Is It? Fossils are the re mains of past liv ing organ isms. Who Dis cov ered It? Nich o las Steno

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The only way we can learn about the ancient past is to exam ine fos sil remains of now extinct plants and ani mals and try to re-create that long-gone life and envi ron ment. Scien - tists can only do this if they correctly inter pret the fos sil remains that are dug from ancient rock layers. That process began with Nicho las Steno. He provided the first true defi ni tion of the word “fossil” and the first under stand ing of the ori gin and na ture of fossils. Steno’s work repre sents the begin ning of our modern process of dating and studying fossils and the devel - op ment of modern geology.

How Was It Discov ered?

How Was It Discov ered? For 2,000 years, any thing dug from the earth was called a fos sil. By the middle ages, fos sil had come to be used for only those things made of stone that were dug from the earth and that looked remark ably like living creatures. Many thought these fossils were God’s practice attempts to create living things. Some claimed they were the Devil’s at tempts to imi tate God. Some believed they were the remains of drowned ani mals from Noah’s flood. No one thought them to be of scientific value. Nich o las Steno was born Niels Stensen in 1638 in Copen ha gen, Den mark. He changed his name to its Latinized form in 1660 when he moved first to Paris and then to Italy to study med i cine. Steno was a stu dent of Ga li leo’s ex per i men tal and math e mat i cal ap proach to sci - ence and focused his studies on hu man muscu lar systems and on us ing math and ge ome try to show how muscles contracted and moved bones and the skele ton. Steno gained consid er - able fame in Italy for these anatomical studies. In Oc tober 1666, two fish ermen caught what was de scribed as “a huge shark” near the town of Livorno, Italy. Because of its enormous size, Duke Ferdinand ordered that its head to be sent to Steno for study. Steno duti fully dissected the head, focus ing on the muscu la ture of the shark’s deadly jaw.

25 26 Fos sils

However, when he exam ined the shark’s teeth under a micro scope, Steno was struck by their re semblance to cer tain stone fos sils called glossopetrae, or “tongue stones,” that were found in rock layers throughout the coastal hills. Glossopetrae had been found and known since the early Roman Empire. The famed Roman author Pliny the Elder thought they were part of the moon that fell from the sky. As Steno compared his monstrous shark teeth with glossopetrae samples, he sus pected that glossopetrae not only re sem bled sharks’ teeth, they were sharks’ teeth. Ital ian sci en tists scoffed that glossopetrae could n’t be from a sea crea ture because they were often found miles from the sea. Steno argued that they must have been depos ited in shallow water or mud when the ancient shark died and that these areas had somehow been lifted up to become dry land. Others countered that glossopetrae couldn’t be teeth since sharks’ teeth were not made of stone. Steno expanded his study to include fossils that resem bled bones and bone fragments. When he viewed these under the micro scope he was convinced that they, too, had origi nally been bones, not stones. After months of study, Steno used the then new “corpus cu lar theory of mat ter” (a fore runner of atomic the ory) to argue that time and chemi cal ac tion could al ter the compo sition of teeth and bones into stone. Steno published his discov ery and support ing evi dence in 1669. In addi tion to proving that fossils were really the ancient bones of living creatures, Steno inves ti gated how these bones came to lie in the middle of rock layers. Through this work he discov ered the process of sedi men ta tion and of creat ing sedi men tary rock layers. For this discov ery Steno is also cred ited with founding modern geology. At the height of his sci en tific ca reer, Steno was or dained a Catho lic priest and com - pletely aban doned sci ence be cause he said that sci ence was in com pat i ble with the teach ings of the Church. Luckily, his discov er ies remained to ad vance and benefit science.

Fun Facts: When we think of fos sils, we think of giant dino saurs. But, the world’s largest rodent fos sil remains were dis covered in northern South America in 2003. The fossil remains of this giant rodent weighed 1,500 pounds (700 kilo grams) and dated back some eight million years.

More to Ex plore

More to Explore Ar cher, Mi chael. Fos sil Hunt ers: The Job of Pa le on tol o gists. New York: Scholas tic, 1999. Lutz, Frank. Nich o las Steno. New York: Do ver,1995. Mayor, Adrienne. The First Fos sil Hunt ers. Princeton, NJ: Princeton Univer sity Press, 2001. Stern berg, Charles. The Life of a Fossil Hunter. Bloomington: In di ana Uni ver sity Press, 1999. Dis tance to the Sun

Distance to the Sun DISTANCE TO THE SUN Year of Dis cov ery: 1672

What Is It? The first ac cu rate cal cu la tion of the dis tance from the earth to the sun, of the size of the so lar system, and even of the size of the universe. Who Dis cov ered It? Giovanni Cassini

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Our under stand ing of the universe depends on two founda tions—our ability to measure the dis tances to faraway stars, and our abil ity to measure the chemi cal compo sition of stars. The dis covery that allowed sci entists to de termine the compo sition of stars is described in the 1859 entry on spectro graphs. The distance to the sun has always been re- garded as the most impor tant and funda men tal of all ga lac tic measure ments. Cassini’s 1672 measure ment, how ever, was the first to accurately estimate that distance. Cassini’s discov ery also provided the first shocking hint of the truly immense size of the universe and of how small and insig nif i cant Earth is. Before Cassini, most scien tists believed that stars were only a few mil lion miles away. After Cassini, scien tists real ized that even the closest stars were billions (if not tril lions) of miles away!

How Was It Discov ered?

How Was It Discov ered? Born in 1625, Giovanni Cassini was raised and edu cated in It aly. As a young man he was fas cinated by astrol ogy, not as tronomy, and gained wide spread fame for his astro log i - cal knowledge. Hundreds sought his astro log i cal advice even though he wrote pa pers in which he proved that there was no truth to astro log i cal predictions. In 1668, af ter conduct ing a series of as tronom i cal studies in Italy that were widely praised, Cassini was offered a posi tion as the direc tor of the Paris Obser vatory. He soon de - cided to become a French citi zen and changed his name to Jean Dominique Cassini. With an improved, high-powered telescope that he carefully shipped from Italy, Cassini con tinued a string of astro nom i cal discov er ies that made him one of the world’s most famous scien tists. These discov er ies included the rota tional peri ods of Mars and Sat- urn, and the ma jor gaps in the rings of Saturn—still called the Cassini gaps. Cassini was also the first to suspect that light trav eled at a finite speed. Cassini refused to publish his evi dence, and later even spent many years trying to dis prove his own the ory. He was a deeply reli gious man and believed that light was of God. Light therefore had to be perfect and infi nite, and not lim ited by a fi nite speed of travel. Still, all of his astro nom ical work sup ported his dis covery that light traveled at a fixed and finite speed. 27 28 Distance to the Sun

Because of his deep faith in the Catho lic Church, Cassini also believed in an Earth-centered universe. By 1672, however, he had become at least partially convinced by the early writing of Kep ler and by Coper ni cus’s careful ar gu ments to con sider the pos sibil - ity that the sun lay at the center. This notion made Cassini decide to try to calcu late the dis tance from the earth to the sun. However, it was diffi cult and danger ous to make direct measure ments of the sun (one could go blind). Luckily, Kepler’s equations allowed Cassini to cal cu late the dis tance from the earth to the sun if he could mea sure the dis tance from the earth to any planet. Mars was close to Earth and well-known to Cassini. So he de cided to use his im proved tele scopes to mea sure the dis tance to Mars. Of course he could n’t ac tu ally measure that dis - tance. But if he mea sured the angle to a spot on Mars at the same time from two dif fer ent points on Earth, then he could use these angles and the geom e try of trian gles to calcu late the distance to Mars. To make the cal cula tion work, he would need to make that baseline distance between his two points on Earth both large and pre cisely known. He sent French astron o mer Jean Richer to Cayenne in French Guiana off the north cost of South Amer ica. Cassini stayed in Paris. On the same August night in 1672, at exactly the same moment, both men mea sured the angle to Mars and placed it exactly against the background of distant stars. When Richer re turned to Paris with his read ings, Cassini was able to cal cu late the dis tance to Mars. He then used Kep ler’s equa tions to discover that the dis tance to the sun had to be 87 million miles (149.6 million km). Modern science has found that Cassini’s calcu la tion was only 7 percent off the true distance (just over 93 million miles). Cassini went on to calcu late the distances to other planets and found that Saturn lay a stag gering 1,600,000,000 (1.6 billion) miles away! Cassini’s discov er ies of distance meant that the universe was millions of times bigger than anyone had dreamed.

Fun Facts: The sun’s diam e ter is 1.4 million km (875,000 miles). It is approx i mately 109 times wider than the earth.

More to Ex plore

More to Explore Brush, Stephen. The History of Modern Astron omy . New York: Garland, 1997. Core, Thomas. The Distance from the Sun to the Earth. New York: Do ver, 2002. Hinks, Arthur. New Measure ments of the Distance to the Sun. London: Taylor and Francis, 1995. Sell ers, Da vid. The Transit of Venus: The Quest to Find the True Distance to the Sun. New York: Magavelda Press, 2001. Bacte ria

Bac te ria BACTERIA Year of Dis cov ery: 1680

What Is It? Micro scopic organ isms exist that cannot be seen by the human eye. Who Dis cov ered It? Anton van Leeuwenhoek

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Just as Gali leo used his tele scope to open the hu man hori zon to the planets and stars of space, so van Leeuwenhoek used his micro scope to open human awareness to the micro - scopic world that was invis i bly small and that no one had even dreamed existed. He discov - ered proto zoa, bacte ria, blood cells, sperm, and capil lar ies. His work founded the science of micro bi ol ogy and opened tissue studies and plant studies to the micro scopic world. He completed hu man under stand ing of the circulatory system.

How Was It Discov ered?

How Was It Discov ered? Anton van Leeuwenhoek was born in 1632 in Delft, Holland. With no advanced school ing, he was ap prenticed as a cloth merchant and as sumed that buying and selling cloth would be his career. But van Leeuwenhoek was curi ous about the world and inter ested in mathe mat ics. Completely self-taught, he learned enough math to moonlight as a surveyor and read what he could about the natu ral world around him. He never learned any language other than Dutch, so he was never able to read any of the sci en tific papers and re search (all writ ten in Latin or French). Micro scopes existed in Holland by 1620. Christian Huygens and Robert Hooke were the first two scien tists to make scien tific use of micro scopes. Both designed and built two-lens micro scopes (two ground glass lenses inside a thin metal barrel). In 1657 van Leeuwenhoek looked through his first micro scope and was fasci nated. He tried a two-lens micro scope, but was disap pointed by its distor tion and low reso lu tion. When he built his first micro scope, he used a highly curved single lens to gain greater magnification. By 1673 van Leeuwenhoek had built a 270-power micro scope that was able to see objects only one-one-millionth of a meter in length. Van Leeuwenhoek remained very secre - tive about his work and never allowed others to see his micro scopes or setup.

29 30 Bac te ria

Van Leeuwenhoek started his micro scopic studies with objects he could mount on the point of a pin—a bee’s mouth parts, fleas, human hairs, etc. He described and drew what he saw in precise detail. By 1674 he had devel oped the ability to focus on a flat dish and turned his atten tion to liq uids—water drops, blood cells, etc. Those 1674 studies were where he made his great discov ery. He discov ered a host of mi cro scopic pro to zoa (bac te ria) in ev ery wa ter drop. He had dis cov ered mi cro scopic life, invis i ble to the human eye. Van Leeuwenhoek expanded his search for these unseeably small creatures and found them every where: on human eyelashes, on fleas, in dust, and on skin. He drew and described these tiny crea tures with ex cel lent, pre cise drawings. Each draw ing often took days to complete. As an ama teur, Van Leeuwenhoek had to work at his science in the evenings and early morning hours when not at work. Embar rassed by his lack of lan guage skills and by his poor spelling (even in Dutch), van Leeuwenhoek felt hesi tant to pub lish any arti cles about his won drous findings. Begin ning in 1676, he agreed to send letters and drawings to the Royal Soci ety of Lon- don. They had them trans lated into English. That ex tensive collec tion of letters (written and collected over many decades) formed the first and best map of the micro scopic world. What van Leeuwenhoek observed shattered many scien tific beliefs of the day and put him de cades—if not cen tu ries—ahead of other re search ers. He was the first to claim that bac te ria cause in fec tion and dis ease. (No one else be - lieved it until Pasteur proved it in 1856.) Van Leeuwenhoek saw that vin egar killed bacte ria and said that it would clean wounds. Again, it was two centu ries before his belief became stan dard med i cal practice. It was also 200 years before anyone built a better micro scope. But with his marvel ous mi cro scope, van Leeuwenhoek dis cov ered the crit i cally im por tant mi cro scopic world.

Fun Facts: In 1999 scien tists discov ered the largest bacte rium ever. The organ ism can grow to as large as .75 mm across—about the size of the period at the end of this sentence. The newfound bac terium is 100 times larger than the previ ous record holder. For compar i son, if the newly dis - cov ered bacte rium was the size of a blue whale, the aver age bac te rium would be the size of a newborn mouse.

More to Ex plore

More to Explore Dobell, Clifford. Anthony van Leeuwenhoek and His “Little Ani mals.” New York: Do ver, 1990. Ralston, Alma. The Cleere Observer: A Biog ra phy of Antony van Leeuwenhoek. New York: Macmillan, 1996. Ruestow, E. The Micro scope in the Dutch Repub lic: The Shaping of Discov ery. New York: Cambridge Univer sity Press, 1996. Schierbeek, A. Measur ing the Invis i ble World: The Life and Works of Anthony van Leeuwenhoek. London: Abelard-Schuman, 1999. Yount, Lisa. Antony van Leeuwenhoek: First to See Micro scopic Life. Beecher, IL: Sage brush, 2001. Laws of Mo tion

Laws of Motion LAWS OF MOTION Year of Dis cov ery: 1687

What Is It? The funda men tal rela tion ships of matter, force, and motion upon which are built all physi cal science and engi neer ing. Who Dis cov ered It? Isaac New ton

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? New ton’s three laws of mo tion form the very the foun dation of phys ics and engi neer - ing. They are the under ly ing theo rems that our physi cal sciences are built upon, just as Eu- clid’s basic theo rems form the founda tion of our modern geom e try. For the creation of these laws, combined with his discov ery of gravity and his creation of cal culus, Newton is con - sid ered the preem i nent scien tific intellect of the last millennium.

How Was It Discov ered?

How Was It Discov ered? Ever since Johannes Kepler’s 1609 discov ery that planets travel in ellip ti cal (not circu - lar) orbits around the sun, scien tists had been fran tically trying to mathe mat ically explain these orbits. Robert Hooke and John Halley both tried. But neither could make the mathematics work. Born in 1642 in Lincolnshire, England, 60 miles from Cambridge, Isaac Newton was a diffi cult child. His father died three months before Isaac’s birth. Isaac never liked his step- fa ther and was left to be raised by his grandpar ents. But Newton felt no affec tion toward anyone—not his mother, not his grandpar ents, nor even his half-brother and sister. He often threatened to hit them and to burn down the house. He was a disci pline problem in school. Only one man, William Ayscough, recog nized Isaac’s brilliance and poten tial and arranged for Newton to study at Trinity College (part of Cambridge Univer sity). Being poor and unable to pay the large tui tion, Newton worked as a servant to other students to pay for room and board. Newton was always soli tary and secre tive. Others said he was surly and argumentative. In 1665 Cambridge closed when the plague struck London. New ton retired to his sister’s coun try es tate. There he felt frus trated by the iso la tion and by a lack of math e mat i cal tools to describe the changing forces and motions he wanted to under stand. He was deter - mined to master the forces that made things move (or not move). Newton studied writings by Gali leo and Aris totle as well as the more recent works by Kepler and Halley. He gathered the scattered and often contra dic tory obser va tions and the- o ries de vel oped since the time of the early Greeks. He stud ied and re fined them, search ing 31 32 Laws of Motion

for com mon truths and for er rors. New ton was amazingly good at sift ing through this mountain of ideas for the few that held truth. New ton was not much of an exper i menter. He thought about problems, con ducting mind exper i ments as did Einstein. Newton thought about things intently for a long time until he formed the answers he needed. In his own words, he “kept the sub ject constantly before him and waited un til the first dawnings opened lit tle by lit tle into full light.” Solving the mystery of the forces that create motion quickly became an obses sion with New ton. He focused his atten tion on Ga lileo’s laws of falling bodies and on Kep ler’s laws about the motion of planets. He often went without sleep or food, to the edge of physi cal breakdown. New ton devel oped his three laws of mo tion in early 1666. They were the essen tial building blocks for his cre ation of cal culus and his dis covery of gravity. How ever, New ton did not publish these laws until Halley coaxed him to write Principia 20 years later. In 1684 Jean Picard produced the first accu rate figures for the size and mass of Earth. This finally gave Newton the numbers he needed to prove that his laws of motion combined with his equa tion for gravity cor rectly pre dicted the actual or bits of the plan ets. Even after com plet ing this math e mat i cal proof, New ton only pub lished Principia in 1687 because Halley begged and cajoled him to—mostly because Robert Hooke claimed (falsely) to have de vel oped uni ver sal laws of mo tion him self. Principia be came one of the most re vered and most used publi ca tions in the history of science.

Fun Facts: For every mo tion, there is a force. Gary Hardwick of Carlsbad, Cal i for nia, cre ated enough force to set a skate board speed re - cord (standing posi tion) of 100.66 km/h (62.55 mph) at Fountain Hills, Ar i zona, on Sep tem ber 26, 1998.

More to Ex plore

More to Explore Boorstin, Dan iel. The Discover ers: A History of Man’s Search to Know His World and Him self. New York: Random House, 1997. Christianson, Gale. Isaac New ton and the Sci en tific Rev o lu tion. New York: Ox ford Uni ver sity Press, 1996. Gale, Christeanson. In the Pres ence of the Creator: Isaac Newton and His Times. New York: Collier Macmillan, 1994. Gleick, James. Isaac New ton. New York: Vintage, 2004. Maury, Jean. Newton: The Father of Modern Astron omy. New York: Harry Abrams, 1996. Peteson, Ivars. Newton’s Clock. New York: W. H. Freeman, 1995. Westfall, Richard. The Life of Isaac Newton. New York: Cambridge Univer sity Press, 1997. White, Mi chael. Isaac Newton: The Last Sorcerer. Jackson, TN: Perseus Books, 1999. Or der in Na ture

Order in Nature ORDER IN NATURE Year of Dis cov ery: 1735

What Is It? All living plants and an imals can be grouped and orga nized into a sim ple hi er ar chy. Who Dis cov ered It? Carl Linnaeus

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Until the eighteenth cen tury, na ture was viewed as a wild profu sion of life. Carl Linnaeus dis cov ered or der and or ga ni za tion in that seem ing ran dom ness. His sys tem for nam ing, group - ing, and con cep tu ally or ga niz ing plants and an i mals pro vided in sights into bot any, bi ol ogy, ecosys tems, and bio log i cal structure that scien tists still rely on almost 300 years later. For his discov ery, Carl Linnaeus is called the father of modern taxon omy. (“Taxon omy” is Greek for “nam ing in order.”) The proof of his influ ence over, and impor tance to, mod ern science can be seen in two ways. First, all of sci ence still uses his sys tem and still uses Latin names for exist ing and new species as Linnaeus did—the last vestige of that ancient language once the uni ver sal lan guage of sci ence. Ev ery newly dis cov ered spe cies is im me di ately clas si fied and named accord ing to Linnaeus’s system. Second, every biol o gist has used Linnaeus’s system to orga nize, under stand, identify, and refer to every plant and an imal species. Linnaeus was the first to identify humans as homo sa pi ens and place humans in the greater flow of life as part of the pri mate order. His classi fi ca tion sys tem was the or igin of the con cept of a “tree of life” since ev ery liv ing thing be longed to a species, ge nus, family, class, order, and phyla and to the plant or ani mal kingdom—anal o gous to the twigs, branches, and trunk of a tree.

How Was It Discov ered?

How Was It Discov ered? Carl Linnaeus hated dis order. He claimed he could never under stand anything that was not sys tem ati cally ordered. Born in Sweden in 1707, he was supposed to become a priest like his fa ther. But Carl showed lit tle ap titude for, and no inter est in, the priesthood and was finally allowed to switch to medicine. He en tered the Univer sity of Lund’s School of Medi cine in 1727 but spent more time in the uni versity’s small botan i cal garden than in class. Linnaeus had been fasci nated by plants and flowers since he was a small child. In 1728 Linnaeus transferred to the Univer sity of Uppsala (partly because they had bigger botan i cal gardens). There he read a paper by French bota nist Sebastian Vaillant that claimed (it was con sidered shockingly rev o lution -

33 34 Or der in Na ture ary at the time) that plants re pro duced sex u ally and had male and fe male parts that cor re - sponded to the sexual organs of animals. The idea ap pealed to Linnaeus. As an ob ses sive cat a loger, he had al ways de tested the no tion that each of the thousands of plants he saw in bo tani cal gardens were indi vid ual and sepa rate species. Linnaeus began to wonder if he could use the differ ences in plants’ repro - ductive parts as a means of classi fy ing and order ing the vast array and profu sion of plants. His dream of bringing order to the chaos of nature was born. Glib, cordial, and with a natu ral talent for ingra ti at ing himself with rich and power ful sup- porters, Linnaeus was able to arrange finan cial support for a se ries of expe di tions across differ ent areas of Swe den to study and cata log plant species. He spent months tramp ing across the coun try- side list ing, describ ing, and studying every plant he found. His expe di tions were always the picture of perfect order. He started each day’s hike pre cisely at 7:00 in the morning. Linnaeus stopped for a meal break at 2:00 P.M. He paused for a rest and lec ture break at 4:00 P.M. During these expe di tions, Linnaeus focused his studies on the repro duc tive systems of each plant he found. Soon he discov ered common charac ter is tics of male and female plant parts in many species that he could group into a single cate gory. He lumped these cate go ries together into larger groups that were, again, combined with other groups into yet larger classi fi ca tions. He found that plants fit neatly into groups based on a few key traits and that order did exist in the natural world. By 1735 he had described more than 4,000 spe cies of plants and pub lished his clas sifi - cation system in a book, Systema Naturae. This system described the eight levels Linnaeus finally built into his system: species, genus, family, order, Class, Subphylum, Phylum, and Kingdom. This system—based solely on the sexual ele ments of plants and (later) ani mals— was contro ver sial with the public. But bota nists found it easy to use and appealing. Linnaeus’s system spread quickly across Europe and was often drawn as a tree, with giant branches being classes, down to the ti niest twigs of spe cies. From these drawings came the con cept of a “Tree of Life.” Linnaeus spent the next 30 years tour ing Europe add ing new plants to his system. In 1740 he added ani mal species into his sys tem. By 1758 he had described and classi fied 4,400 ani mal species and more than 7,700 plant species. In 1758, with the tenth edition of his book, he intro duced the bino mial (two-name) system of naming each plant and ani mal by species and genus. With that addi tion, Linnaeus’s system was complete. He had discov ered both that order ex isted in the natu ral world and a system for describ ing that order—a sys tem still very much alive and in use today.

Fun Facts: The world’s most massive living tree is General Sherman, the giant sequoia (Sequoia den dron giganteum) growing in the Sequoia National Park in Cal ifor nia. It stands 83.82m (274.9 ft.) tall and has a di- ame ter of 11.1 m (36 ft., 5 in.). This one tree is esti mated to contain enough wood to make five billion matches—one for al most every person on Earth. More to Explore 35

More to Ex plore

More to Explore Ander son, Marga ret. Carl Linnaeus: Father of Classi fi ca tion . Berkeley Heights, NJ: Enslow, 2001. Dickenson, Alice. Carl Linnaeus. New York: Franklin Watts, 1995. Fara, Pa tri cia. Sex, Botany, and Em pire: The Story of Carl Linnaeus and Joseph Banks. New York: Co lumbia Univer sity Press, 2004. Hagberg, Knut. Carl Linnaeus. New York: Dutton, 1992. Stoutenburg, Adrien. Beloved Bota nist: The Story of Carl Linnaeus. New York: Scribner, 1994. Tore, Frangsmyr, ed. Linnaeus: The Man and His Work. Berkeley: Uni versity of Cali - fornia Press, 2001. Gal ax ies

Gal ax ies GALAXIES Year of Dis cov ery: 1750

What Is It? Our sun is not the center of the universe but is rather part of a giant, disc-shaped cluster of stars that floats through space. Who Dis cov ered It? Thomas Wright and William Herschel

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The dis cov ery that stars are clumped into gal ax ies rep re sents the first ad vance in ef - forts to describe the actual shape of the universe and the dis tribu tion of stars in it. Wright’s theory of galax ies was the first astro nom i cal work to place our sun not in the center of the universe, but in a tightly packed cluster of stars that Wright called a galaxy. This discov ery led science a giant step forward in its efforts to under stand the vast universe of which our sun and Earth repre sent only tiny and very ordi nary specks. Twenty-five years later, Herschel conducted careful obser vational studies that proved Wright was right.

How Was It Discov ered?

How Was It Discov ered? For thousands of years scien tist believed that the universe consisted of a vast spher ical shell of stars, with Earth at its center. Noth ing ex isted in the immense void between Earth and that shell of stars except the few plan ets and the sun. By the mid-1600s, most scien tists acknowl edged that the sun, not the earth, sat at the center of the spheri cal universe. Some prom inent scien tists (Christian Huygens, for exam - ple) believed that stars were re ally holes in the black sphere of space where light from a lu- minous re gion of per petual day beyond shined through. Two men’s discov er ies combined to estab lish the exis tence of dense clusters of stars called galax ies. Born in 1711, English man Thomas Wright taught mathe mat ics and navi ga - tion but was a passion ate ama teur astron o mer. As had many astron o mers before him, Wright observed that the stars were not evenly spread across the sky. A seeming cloud of faint stars was densely packed along the band called the Milky Way. This both ered Wright. He be lieved that God had created a universe of perfect order. That should mean that stars were neatly and evenly—per fectly—spaced across the heav ens. Wright could not accept that the heavens were not perfect and so began to play with schemes for the place ment of stars to make them re ally be uniform in their place ment even though they ap peared not to be.

36 More to Explore 37

Wright consid ered that the stars might be spread along the surfaces of a field of giant bubbles. If we were packed along one of those rings of stars, looking along the ring would cause us to see more stars than if we looked straight out from it. He then con sidered the rings of Sat urn and pro posed that the stars might be packed into wide rings or a thin disk. If we were in that disc, it would account for the uneven distri bu tion of stars we saw—even if the stars were re ally evenly spaced across that disk. In 1750 Wright published a book, An Origi nal Theory on New Hypoth e sis of the Uni- verse, in which he proposed this the ory. He was the first to use the word gal axy to describe a gi ant clus ter of stars. Five years later, famed as trono mer and math ema ti cian Im man uel Kant proposed a sim ilar arrange ment of the stars into a giant disk-shaped cluster. English astron o mer William Hershel (born in 1738) read with in terest Wright’s theory. In 1785 Herschel decided to use statis ti cal methods to count the stars. He surely couldn’t count them all. So he ran domly picked 683 small regions of the sky and set about counting the stars in each region using a 48-inch telescope—con sid ered a giant scope at the time. Herschel quickly real ized that the number of stars per unit area of sky rose steadily as he approached the Milky Way and spiked in regions in the Milky Way. (The number of stars per unit area of sky reached a min imum in direc tions at right an gles to the Milky Way.) This made Herschel think of Wright’s and Kant’s theo ries. Hershel concluded that his counting results could only be explained if most of the stars were com pacted into a lens-shaped mass and that the sun was buried in this lens. Herschel was the first to add sta- tisti cal mea sure ment to Wright’s dis covery of the exis tence and shape of galaxies.

Fun Facts: The central galaxy of the Abell 2029 galaxy cluster, 1,070 million light years dis tant in Virgo, has a diam e ter of 5,600,000 light years, 80 times the diam e ter of our own Milky Way galaxy.

More to Ex plore

More to Explore Greenstein, George. Por traits of Dis cov ery: Pro files in Sci en tific Ge nius. New York: John Wiley & Sons, 1997. Hub bard, Elbert. Wil liam Hershel. Whitefish, MT: Kessinger, 2001. Roan, Carl. The Dis cov ery of the Gal ax ies. San Fran cisco: Jack daw Pub li ca tions, 2000. Taschek, Ka ren. Death Stars, Weird Galax ies, and a Quasar-Span gled Universe . Al- bu querque: Univer sity of New Mexico Press, 2006. Whit ney, Charles Allen. Discov ery of Our Galaxy . Iowa City: Iowa State Press, 1997. The Na ture of Electric ity

The Nature of Electric ity THE NA TURE OF ELEC TRIC ITY Year of Dis cov ery: 1752

What Is It? All forms of electric ity are the same. Who Dis cov ered It? Benjamin Franklin

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Elec tric ity is one of our greatest energy re sources and one of the few natu ral en ergy sources. Franklin’s electric ity ex peri ments were the first scien tific ventures into the na ture and use of electric ity and uncov ered its true nature. They set the stage for much of the scien - tific and engi neer ing devel op ment in the nineteenth century and for the explo sion of elec trical de vel op ment—bat ter ies, motors, generators, lights, etc.

How Was It Discov ered?

How Was It Discov ered? All that was known about electric ity in the mid-eighteenth century was that there were two kinds of it: playful static and deadly lightning. Benjamin Franklin was the first scien tist to be gin seri ous electri cal exper i ments (in 1746). He was also the first to suspect that static and light ning were two forms of the same thing. Franklin had been exper i ment ing with Leyden jars—large glass jars, partially filled with water and wrapped with tin foil both inside and out. A rod extended through an in sulat - ing cork out the top of the jar to a metal knob. Once a Leyden jar was charged with a hand crank, anyone who grabbed the knob got a resound ing shock. Franklin found ways to more than double the amount of electric ity his Leyden jars carried, and he invented a way to connect them in series so that they could, collec tively, carry an al most deadly punch. During a 1752 demon stra tion for friends, Frank lin ac ciden tally touched a Leyden jar’s knob. With a sharp crack, a sizzling blue arc leapt from jar to Franklin’s hand. He shot back half a dozen feet and crashed to the floor. Franklin re alized that that jolt looked ex actly like a mini-light ning bolt. He de cided to prove that static and lightning were the same by design ing a Leyden jar–like electric circuit to let electric ity flow from clouds just as it did into a jar. Frank lin’s “cir cuit” was made of a thin metal wire fixed to a kite (to gather elec tric ity from the clouds) and tied to a twine kite string. Electric ity would flow down the twine to a large iron key tied to the bottom. Franklin tied the other end of the key to a nonconducting silk ribbon that he would hold. Thus, electric ity would be trapped in the key, just as it was in a Leyden jar. 38 More to Explore 39

When an after noon storm brewed up dark and threaten ing a few weeks later, Franklin rushed to launch his kite. The wind howled and the clouds boiled. A cold rain pounded down about Franklin’s up turned collar. The kite twisted and tore at the air like a ram paging bull. Then it happened. No, a lightning bolt did not strike the kite, as has often been reported. And a good thing, too. A French scien tist was killed a few months later by a lightning strike when he tried to repeat Franklin’s exper i ment. No, what hap pened that stormy after noon was that the twine be gan to glow a faint blue. The twine’s fi bers lifted and bris tled straight out. Frank lin could al most see electric ity trick ling down the twine as if electric ity were liquid. Franklin reached out a cautious hand closer and closer to the key. And pop! A spark leapt to his knuckle and shocked him—just like a Leyden jar. Lightning and static were all the same, fluid electric ity! The practi cal outcome of this exper i ment was Franklin’s inven tion of the lightning rod, credited with saving thousands of houses and lives over the next 100 years. More important, Franklin’s work inspired exper i ments by Volta, Fara day, Oersted, and others in early part of the nineteenth cen tury that further unrav eled electricity’s nature.

Fun Facts: Popeye uses spinach to power his muscles. Now scien tists are looking to spin ach as a power source for supply ing electric ity. Chem- i cal sub stances ex tracted from spin ach are among the in gre di ents needed to make a solar cell that converts light into electric ity.

More to Ex plore

More to Explore Brands, H. W. Benjamin Frank lin: The Orig i nal Amer i can. New York: Barnes & No ble, 2004. Fradin, Dennis. Who Was Benjamin Franklin? New York: Penguin Young Readers’ Group, 2002. Isaacson, Wal ter. Benjamin Franklin: An Ameri can Life. New York: Simon & Schuster, 2003. McCormick, Ben. Ben Frank lin: Amer ica’s Orig i nal En tre pre neur. New York: McGraw-Hill, 2005. Mor gan, Edmund. Benjamin Franklin . New Haven, CT: Yale Univer sity Press, 2003. Sandak, Cass. Benjamin Frank lin. New York: Franklin Watts, , 1996. Skousen, Mark, ed. Com pleted Au to bi og ra phy of Benjamin Frank lin. Wash ing ton, DC: Regnery Publish ing, 2005. Wright, Esmond. Frank lin of Phil a del phia. Cam bridge, MA: Har vard Uni ver sity Press, 1996. Oceans Con trol Global Weather

Oceans Control Global Weather OCEANS CONTROL GLOBAL WEATHER Year of Dis cov ery: 1770

What Is It? By pumping massive amounts of heat through the oceans, vast ocean cur rents con trol weather and cli mate on land. Who Dis cov ered It? Benjamin Franklin

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The Atlan tic Ocean’s Gulf Stream is the most impor tant of our world’s ocean currents. It is a ma jor heat engine, carry ing massive amounts of warm water north to warm Europe. It has directed the patterns of ocean ex plora tion and commerce and may be a ma jor deter mi - nant of the onset of ice ages. Finally, it is the key to under stand ing global circu la tion pat - terns and the in ter con nec ted ness of the world’s oceans, weather, and climates. Ameri can statesman, inven tor, and scien tist Benjamin Franklin conducted the first scientific inves ti ga tion of the Gulf Stream and discov ered its impor tance to Earth’s weather and cli mate. His work launched sci en tific study of ocean currents, ocean temper ature, the inter ac tion of ocean current with winds, and the effect of ocean currents on climate. Frank- lin’s discov er ies mark the be ginnings of modern oceanographic science.

How Was It Discov ered?

How Was It Discov ered? Benjamin Franklin set out to map the Gulf Stream in or der to speed trans atlan tic shipping. He wound up discov er ing that ocean currents are a major control ling factor of global cli mate and weather. Ocean sur face cur rents were noted by early Norse sail ors as soon as they sailed the open Atlan tic. Colum bus and Ponce de Leon described the Gulf Stream current along the coast of Florida and in the strait between Florida and Cuba. Others noted North At lantic currents over the next hundred years. However, no one charted these currents, recorded them on maps, or connected the indi vid ual sightings into a grand, oceanwide system of massive currents. In 1769 British offi cials in Boston wrote to London complain ing that the British pack- ets (small navy ships that brought passen gers and mail to the colo nies) took two weeks longer in their trans-Atlan tic crossing than did Ameri can merchant ships. Benjamin Franklin, an Ameri can repre sen ta tive in London at the time, heard this report and refused to believe it. 40 How Was It Discov ered? 41

Packet ships rode higher in the wa ter, were faster ships, and were better crewed than heavy Rhode Island merchant ships. Franklin men tioned the re port to a Rhode Island merchant captain off-load ing cargo in London. This captain said it was abso lutely true and happened because Rhode Island whal- ers had taught Ameri can merchant captains about the Gulf Stream, a 3 mph current that spread eastward from New York and New England toward England. Ameri can captains knew to curve either north or south on westward trips to avoid fighting this powerful current. When Franklin checked, the Gulf Stream didn’t appear on any maps, nor did it appear in any of the British Navy shipping manu als. Franklin began inter view ing merchant and whal ing cap tains, record ing on maps and charts their expe ri ence with the Gulf Stream current. Whal ers, es pe cially, knew the cur rent well be cause whales tended to con gre gate along its edges. By 1770 Franklin had prepared detailed maps and descrip tions of this current. British Navy and merchant captains, however, didn’t believe him and refused to review his infor - mation. By 1773 rising tensions between England and the colo nies made Franklin withhold his new findings from the British. Frank lin be gan tak ing reg u lar wa ter tem per a ture read ings on ev ery At lan tic Ocean crossing. By 1783 he had made eight crossings, carefully plotting the exact course his ship took each time and marking his temper a ture readings on the ship’s map. On his last voyage from France to America, Frank lin talked the ship’s captain into track ing the edge of the Gulf Stream cur rent. This slowed the voyage as the ship zigzagged back and forth using the warm water temper a ture inside the Gulf Stream and the colder water temper a ture out side it to trace the current’s boundary. The captain also allowed Franklin to take both surface and subsurface (20 and 40 fath- oms) tem pera ture readings. Franklin was the first to consider the depth (and thus the vol - ume) of an ocean current. Franklin discov ered that the Gulf Stream poured masses of warm water (heat) from the tropi cal Carib bean to ward northern Europe to warm its climate. He began to study the in ter- action between wind and current and between ocean currents and weather. Through the brief papers he wrote de scribing the Gulf Stream data he had collected, Franklin brought sci ence’s at ten tion and in ter est to ocean cur rents and their effect on global climate. Frank lin’s descrip tion of the Gulf Stream was the most detailed available un til German sci entist Alex an der von Humbolt published his 1814 book about the Gulf Stream based on his measure ments from more than 20 crossings. These two sets of studies repre sent the be- ginnings of mod ern oceanographic study.

Fun Facts: The Gulf Stream is bigger than the combined flow of the Missis sippi, the Nile, the Congo, the Ama zon, the Volga, the Yangtze, and virtu ally ev ery other ma jor river in the world. 42 Oceans Control Global Weather

More to Ex plore

More to Explore Brands, H. W. Benjamin Frank lin: The Orig i nal Amer i can. New York: Barnes & No - ble, 2004. Fradin, Dennis. Who Was Benjamin Franklin? New York: Penguin Young Readers’ Group, 2002. Isaacson, Wal ter. Benjamin Franklin: An Ameri can Life. New York: Simon & Schuster, 2003. McCormick, Ben. Ben Frank lin: Amer ica’s Orig i nal En tre pre neur. New York: McGraw-Hill, 2005. Mor gan, Edmund. Benjamin Franklin . New Haven, CT: Yale Univer sity Press, 2003. Sandak, Cass. Benjamin Frank lin. New York: Franklin Watts, 1996. Skousen, Mark, ed. Com pleted Au to bi og ra phy of Benjamin Frank lin. Wash ing ton, DC: Regnery Publish ing, 2005. Wright, Esmond. Frank lin of Phil a del phia. Cam bridge, MA: Har vard Uni ver sity Press, 1996. Ox y gen

Ox y gen OXYGEN Year of Dis cov ery: 1774

What Is It? The first gas sep arated and iden ti fied as a unique el ement. Who Dis cov ered It? Joseph Priestley

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Priestley’s discov ery of oxy gen sparked a chemi cal revo lu tion. He was the first person to iso late a sin gle gas eous el e ment in the mix ture of gas ses we call “air.” Be fore Priestley’s discov ery, scien tific study had focused on metals. By discov er ing that air wasn’t a uniform thing, Priestley created a new inter est in the study of gasses and air. Because oxy gen is a cen tral ele ment of com bustion, Priestley’s dis covery also led to an under stand ing of what it means to burn something and to an under stand ing of the conver - sion of matter into energy during chemical reactions. Finally, Priestley estab lished a simple but ele gant and effec tive process for conduct ing anal y sis of new gasses and gas eous ele ments. What did it look like? Would it burn (first a candle and then wood splinters)? Would it keep a mouse alive? Was it absorbed by water?

How Was It Discov ered?

How Was It Discov ered? Rever end Joseph Priestley was more fasci nated by air than by his church duties. Air was one of the four tradi tional el ements (with fire, wa ter, and earth). But Priestley felt driven to find out what air was made of. Other scien tists wrote of creat ing new gasses that bubbled up during chemi cal reac - tions. Some had described these as “wild gasses” that built up enough pressure to explode glass jars or to triple the rate at which wood burned. But none had success fully iso lated and studied these new gasses. Priestley’s imagi na tion soared. He felt compelled to seek out and study these wild, untamed gas ses. In early 1774 Priestley de cided the only way to iso late and study these new gasses was to trap them under water in an upside down (inverted), water-filled glass jar in which there was no air. He de cided to begin by burning solid mercurius calcinatus and study ing the gas that re ac tion had been re ported to cre ate. On August 1, 1774, Priestley used a power ful magni fy ing lens to focus sunlight on a bottle of powdered mercurius calcinatus. A cork stopper sealed this bottle with a glass tube lead ing from it to a wash tub full of water, where wa ter-filled glass jars stood inverted on a 43 44 Ox y gen

wire mesh stand. Priestley’s glass tube ended just under the open mouth of one of these bottles so that whatever gas he produced would bubble up into, and be trapped in, that glass jar. As his powdered mer cury compound heated, clear bubbles began to drift up from the end of the glass tube. The jar be gan to fill. Priestley filled three bottles with the gas and was thus the first human to success fully trap this myste ri ous gas. But what was it? Priestley care fully raised one bot tle out of the wa ter. He held a lit can dle beneath its mouth. The dim glow around the candle’s wick erupted into a brilliant ball of fire. As reported, this strange gas did force substances to burn fiercely. Priestley placed a new jar, filled with ordi nary air, upside down on the wire stand next to a second jar of his mystery gas. He placed a mouse in each jar, and waited. The mouse in ordi nary air began to struggle for breath in 20 minutes. The mouse in his second jar of this strange gas breathed comfort ably for over 40 minutes! There seemed only one name for this amaz ing gas: “pure air.” Priestley care fully raised a jar of “pure air” out of his tub. He jammed his own nose into its wide mouth. His heart be gan to beat faster. He closed his eyes, gath ered his cour age, and breathed in as deeply as he could. Joseph felt nothing odd from this breath. He tried a second breath and felt happy and filled with en ergy. Priestley’s breath felt partic u larly light and easy for some time af ter- ward. It took another scien tist, Antoine Lavoisier in Paris, to give Priestley’s “pure air” the name we know it by today: “oxygen.”

Fun Facts: With out ox y gen, bi o log i cal death be gins to oc cur within three minutes. Free-diving World Champion Pipin Ferreras holds the world record for holding his breath: 8 minutes, 58 seconds.

More to Ex plore

More to Explore Bowden, Mary, ed. Joseph Priestley: Radi cal Thinker. Phil a del phia: Chem i cal Her i- tage Foun da tion, 2005. Conley, Kate. Jo seph Priestley and the Dis cov ery of Ox ygen. Hockessin, DE: Mitchell Lane, 2003. Crowther, J. G. Scien tists of the Indus trial Rev o lution: Jo seph Black, James Watt, Jo- seph Priestley, and Henry Cavendish . New York: Dufour Editions, 1996. Gibbs, Frank. Jo seph Priestley. New York: Doubleday, 1997. Irwin, Keith. The Romance of Chemis try . New York: Viking Press, 1996. Partington, James. A Short Course in Chemis try. New York: Do ver, 1999. Schofield, Rob ert. The En light en ment of Jo seph Priestley. Univer sity Park: Pennsyl - vania State Univer sity Press, 1997. Pho to syn the sis

Pho to syn the sis PHOTOSYNTHESIS Year of Dis cov ery: 1779

What Is It? Plants use sunlight to con vert carbon diox ide in the air into new plant matter. Who Dis cov ered It? Jan Ingenhousz

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Photo syn the sis is the process that drives plant produc tion all across Earth. It is also the process that produces most of the oxy gen that exists in our at mosphere for us to breathe. Plants and the process of photo syn the sis are key ele ments in the criti cal (for humans and other mammals) plan etary oxygen cycle. When Jan Ingenhousz discov ered the process of photo syn the sis, he vastly improved our basic under stand ing of how plants function on this planet and helped science gain a better un der stand ing of two im por tant at mo spheric gas ses: ox y gen and car bon di ox ide. Modern plant engi neer ing and crop sciences owe their founda tion to Jan Ingenhousz’s discovery.

How Was It Discov ered?

How Was It Discov ered? Jan Ingenhousz was born in Breda in the Nether lands in 1730. He was edu cated as a phy sician and settled down to start his medi cal prac tice back home in Breda. In 1774 Joseph Priestley discov ered oxy gen and exper i mented with this new, invis i ble gas. In one of these tests, Priestley inserted a lit candle into a jar of pure oxy gen and let it burn until all oxy gen had been consumed and the flame went out. With out allow ing any new air to enter the jar, Priestley placed mint sprigs floating in a glass of water in the jar to see if the mint would die in this “bad” air. But the mint thrived. After two months, Priestley placed a mouse in the jar. It also lived—proving that the mint plant had restored oxy gen to the jar’s air. But this exper i ment didn’t al ways work. Priestley admit ted that it was a mystery and then moved on to other studies. In 1777, Ingenhousz read about Priestley’s exper i ments and was fasci nated. He could focus on noth ing else and de cided to inves ti gate and explain Priestley’s mystery. Over the next two years, Ingenhousz conducted 500 exper i ments trying to account for every variable and every possi ble contin gency. He devised two ways to trap the gas that a plant pro duced. One was to enclose the plant in a sealed cham ber. The other was to submerge the plant.

45 46 Pho to syn the sis

Ingenhousz used both sys tems, but found it easier to collect and study the gas col lected un derwa ter as tiny bubbles. Every time he collected the gas that a plant gave off, he tested it to see if it would support a flame (have oxy gen) or if it would extin guish a flame (be carbon dioxide). Ingenhousz was amazed at the beauty and sym metry of what he discov ered. Humans inhaled oxy gen and ex haled car bon diox ide. Plants did just the oppo site—sort of. Plants in sun light absorbed human waste carbon diox ide and produced fresh oxy gen for us to breathe. Plants in deep shade or at night (in the dark), however, did just the oppo site. They acted like hu mans, absorb ing oxy gen and producing carbon dioxide. After hundreds of tests, Ingenhousz deter mined that plants produced far more oxy gen than they absorbed. Plants immersed in water produced a steady stream of tiny oxy gen bubbles when in direct sunlight. Bubble produc tion stopped at night. Plants left for extended peri ods in the dark gave off a gas that extin guished a flame. When he placed the same plant in direct sunlight, it produced a gas that turned a glowing ember into a burning inferno. The plant again produced oxygen. Ingenhousz showed that this gas pro duction depended on sun light. He contin ued his exper i ments and showed that plants did not produce new mass (leaf, stem, or twig) by ab- sorbing matter from the ground (as oth ers believed). The ground did not lose mass as a plant grew. Ingenhousz showed that new plant growth must come from sunlight. Plants captured car bon from car bon diox ide in the air and con verted it into new plant matter in the presence of sunlight. Ingenhousz had discov ered the process of pho to syn the sis. He proved that plants created new mass “from the air” by fixing carbon with sunlight. In 1779 he published his results in Ex per i ments Upon Veg e ta bles. The name pho to syn the sis was cre ated some years later and co mes from the Greek words mean ing “to be put together by light.”

Fun Facts: Some species of bamboo have been found to grow at up to 91 cm (3 ft.) per day. You can almost watch them grow!

More to Ex plore

More to Explore Allen, J. F., et al., eds. Dis cov er ies in Pho to syn the sis. New York: Springer-Verlag, 2006. Asimov, Isaac. How Did We Find Out About Photo syn the sis? New York: Walker & Co., 1993. Forti, G. Pho to syn the sis Two Cen tu ries Af ter Its Dis cov ery. New York: Springer-Verlag, 1999. Ingenhousz, Jan. Jan Ingenhousz: Plant Physi ol o gist. London: Chronica Botanica, 1989. Con ser va tion of Mat ter

Con ser va tion of Mat ter CONSERVATION OF MATTER Year of Dis cov ery: 1789

What Is It? The to tal amount of mat ter (mass) al ways re mains the same no mat ter what physi cal or chemi cal changes take place. Who Dis cov ered It? Antoine Lavoisier

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Lavoisier was the first chemist to believe in mea sure ment during and after exper i - ments. All chemists before had focused on ob ser va tion and de scrip tion of the reac tions dur - ing an ex peri ment. By carefully measur ing the weight of each substance, Lavoisier dis cov ered that mat ter is nei ther created nor destroyed dur ing a chem i cal re action. It may change from one form to another, but it can al ways be found, or accounted for. Scien tists still use this princi ple ev ery day and call it “conservation of matter.” Lavoisier’s work also estab lished the founda tion and methods of modern chemis try. He did much work with gasses, gave oxy gen its name (Joseph Priestley discov ered oxy gen but called it “pure air”) , and discov ered that oxy gen makes up 20 percent of the atmo - sphere. Lavoisier is con sidered the fa ther of modern chemis try.

How Was It Discov ered?

How Was It Discov ered? In the spring of 1781, Frenchman Antoine Lavoisier’s wife, Marie, translated a paper by English scien tist Robert Boyle into French. The paper described an exper i ment with tin during which Boyle had noted an unex plained weight change when the tin was heated. Boyle, like most sci en tists, was con tent to as sume that the extra weight had been “cre ated” during his chemical experiment. Lavoisier scoffed at the notion of myste ri ous creation or loss of mass (weight) during re ac tions. He was con vinced that chem ists’ tra di tional ex per i men tal ap proach was in ad e - quate. Dur ing ex per i ments chem ists care fully ob served and de scribed changes in a substance. Lavoisier claimed it was far more im por tant to re cord what could be mea sured. Weight was one property he could always measure. Lavoisier decided to re peat Boyle’s exper i ment, carefully mea sure weight, and dis - cover the source of the added weight. Antoine carried a small sheet of tin to his deli cate bal - anc ing scales and re corded its weight. Next he placed the tin in a heat-re sis tant glass flask and sealed its lid to con tain the entire reac tion within the flask.

47 48 Con ser va tion of Mat ter

He weighed the flask (and the tin inside) before heating it over a burner. A thick layer of calx (a light gray tarnish) formed on the tin as it heated—as Boyle had described in his pa per. Lavoisier turned off the burner, let the flask cool, and then reweighed it. The flask had not changed weight. He pried off the flask’s lid. Air rushed in, as if into a partial vacuum. Antoine removed and weighed the calx-covered tin. It had gained two grams of weight (as had Boyle’s). Lavoisier de duced that the weight had to have come from the air inside the flask and that was why new air rushed into the flask when he opened it. The tin gained two grams as it mixed with air to form calx. When he opened the lid, two grams of new air rushed in to replace the air that had been ab sorbed into calx. He repeated the exper i ment with a larger piece of tin. However, still only two grams of air were absorbed into calx. He ran the exper i ment again and measured the volume of air that was ab sorbed into calx—20 per cent of the to tal air inside the flask. He con cluded that only 20 percent of air was capa ble of bonding with tin. He real ized that this 20 percent of air must be the “pure air” Priestley had dis covered in 1774, and Lavoisier named it “oxy gen.” Through further exper i ments Lavoisier real ized that he had proved something far more impor tant. Boyle thought weight, or matter, was “created” during exper i ments. Lavoisier had proved that mat ter was neither created nor lost dur ing a chem i cal re action. It al ways came from someplace and went to someplace. Sci en tists could al ways find it if they measured care fully. The all-impor tant concept of conser va tion of matter had been discov ered. However, Lavoisier didn’t release this princi ple until he published his famed chemis try textbook in 1789.

Fun Facts: The Furnace Constel la tion (Fornax) was created to honor the famous French chem ist Antoine Lavoisier, who was guillo tined dur ing the French Revo lution in 1794.

More to Ex plore

More to Explore Dono van, Arthur. Antoine Lavoisier: Science Admin is tra tion and Revo lu tion . New York: Cambridge Univer sity Press, 1996. Grey, Vivian. The Chemist Who Lost His Head. Coward, McCann & Geoghegan, New York, 1982. Holmes, Law rence. Antoine Lavoisier: The Next Crucial Year or the Source of His Quan ti ta tive Method of Chem is try. Collingdale, PA: Diane Publish ing Co., 1998. Kjelle, Marylou. Antoine Lavoisier: Father of Chemis try . Hockessin, DE: Mitchell Lane, 2004. Riedman, Sa rah. Antoine Lavoisier: Sci en tist and Cit i zen. Scarborough, ON: Nelson, 1995. Susac, Andrew. The Clock, the Balance, and the Guillo tine: The Life of Antoine Lavoisier. New York: Doubleday, 1995. Yount, Lisa. Antoine Lavoisier: Founder of Modern Chemis try . Berkeley Heights, NJ: Enslow, 2001. The Na ture of Heat

The Nature of Heat THE NATURE OF HEAT Year of Dis cov ery: 1790

What Is It? Heat comes from fric tion, not from some in ternal chemi cal property of each sub stance. Who Dis cov ered It? Count Rumford

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Scien tists believed that heat was an in vis i ble, weight less liquid called ca lo ric. Things that were hot were stuffed with calo ric. Calo ric flowed from hot to cold. They also be lieved that fire (combus tion) came from another in visi ble sub stance called phlogiston, a vi tal es- sence of combus ti ble substances. As a substance burned, it lost phlogiston to air. The fire ended when all phlogiston had been lost. These er rone ous beliefs kept sci entists from un derstand ing the na ture of heat and of ox i da tion (in clud ing com bus tion), and stalled much of the phys i cal sci ences. Benjamin Thompson, who called himself Count Rumford, shattered these myths and discov ered the princi ple of friction. This dis covery opened the door to a true under stand ing of the nature of heat.

How Was It Discov ered?

How Was It Discov ered? In 1790, 37-year-old Count Rumford was serving the King of Bavaria as a mili tary ad - visor. As part of his du ties he was in charge of the king’s cannon manu fac turing. Born in Massa chu setts as Benjamin Thompson, Rumford had served as a British spy during the Ameri can Revo lu tion ary War. Then he spied on the British for the Prussians. In 1790 he fled to Ba varia and changed his name to Count Rumford. The cannon man u fac turing plant was a deafeningly noisy ware house. On one side, metal wheel rims and mounting brackets were hammered into shape around wooden wheels and can non car riages. Steam rose from hissing vats as glowing metal plates were cooled in slimy water. On the other side of the warehouse, great can nons were forged. Molten metal poured into huge molds—many 12 feet long and over 4 feet across. Spinning drills scraped and gouged out the inside of each can non barrel. Drill bits grew danger ously hot. Streams of water kept them from melting. Hissing steam billowed out of the cannon barrels toward the ceiling, where it condensed and dripped like rain onto the work ers below.

49 50 The Na ture of Heat

On one visit, Rumford rec og nized that great quanti ties of heat flowed into the air and wa ter from those can non bar rels. At that time sci en tists believed that, as a sub stance grew hotter, more calo ric squeezed into it. Even tually calo ric overflowed and spilled out in all direc tions to heat what ever it touched. Rumford wondered how so much ca loric (heat) could pour out of the metal of one cannon barrel—es pe cially since the can non barrels felt cold when the drilling started. Rumford decided to find out how much calo ric was in each barrel and where that ca loric was stored. He fashioned a long trough to catch all the water pouring out of a cannon barrel while it was be ing drilled so he could mea sure its in crease in temperature. He also directed that extra hoses be sprayed on the drilling to pre vent the forma tion of steam. Rumford didn’t want any calo ric escap ing as steam he couldn’t capture and measure. Drilling began with a great screeching. Hoses sprayed water onto the drill bits. The metal began to glow. A torrent of heated water eight inches deep tumbled down the narrow, foot-wide trough and past the Count and his thermom eters. Rumford was thrilled. More calo ric flowed out of that can non barrel than he could have imagined in even his wildest dreams. And still the hot wa ter con tinued to flow past him, all of it heated to more than 50 degrees celsius. Eventu ally the Count’s face soured. Something was very wrong. The metal cannon barrel had already lost more than enough heat (calo ric) to turn it into a bubbling pool of liq - uid metal many thousands of degrees hot. It seemed impos si ble for so much calo ric to have existed in the metal. Count Rumford watched the borers go back to work and real ized that what he saw was mo tion. As drill bits ground against the cannon’s metal, their mo tion as they crashed against the sur face of the metal must cre ate heat. Move ment was being converted into heat! To day we call it fric tion, and know it is one of the primary sources of heat. But in 1790, no one believed Count Rumford’s new theory of friction heat, and they held onto the notion of ca loric for another 50 years.

Fun Facts: Friction with air mole cules is what burns up mete ors as they plunge into the atmo sphere. That same friction forced NASA to line the bottom of every space shuttle with hundreds of heat-resis tant ceramic tiles. Failure of one of those tiles led to the ex plosion of the Co lum bia in 2004.

More to Ex plore

More to Explore Brown, Sanborn. Benjamin Thompson, Count Rumford. Boston: MIT Press, 1996. ———. Collected Works of Count Rumford. Cam bridge, MA: Harvard Univer sity Press, 1994. ———. Count Rumford: Phys i cist Ex traor di nary. Westport, CT: Greenwood, 1995. Ellis, George. Memoir of Benjamin Thompson, Count Rumford. Somerset, PA: New Library Press, 2003. van den Berg, J. H. Two Princi pal Laws of Ther mody nam ics: A Cul tural and Histor i - cal Ex plo ra tion. Pitts burgh: Duquesne Univer sity Press, 2004. Ero sion of the Earth

Erosion of the Earth EROSION OF THE EARTH Year of Dis cov ery: 1792

What Is It? The earth’s surface is shaped by giant forces that steadily, slowly act to build it up and wear it down. Who Dis cov ered It? James Hutton

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? In the eighteenth century scien tists still believed that Earth’s surface had remained unchanged until cata clys mic events (the great flood of Noah’s ark fame was the most often sited exam ple) radi cally and sud denly changed the face of our planet. They tried to under - stand the planet’s surface structures by searching for those few ex plosive events. At tempts to study the earth, its his tory, its land forms, and its age based on this belief led to wildly in- ac cu rate guesses and misinformation. James Hutton dis covered that the earth’s surface contin u ally and slowly changes, evolves. He discov ered the processes that gradu ally built up and wore down the earth’s sur - face. This discov ery provided the key to under stand ing our planet’s history and launched the mod ern study of earth sciences.

How Was It Discov ered?

How Was It Discov ered? In the 1780s, 57-year-old, more-or-less re tired phy sician and farmer (and ama teur ge olo - gist) James Hutton decided to try to improve on the wild guesses about the age of the earth that had been put forth by other scien tists. Hutton decided to study the rocks of his native Scotland and see if he could glean a better sense of Earth’s age by studying the earth’s rocks. Lanky Hutton walked with long pen du lum-like strides across steep, rolling green hills. Soon he re al ized that the ex ist ing geo log i cal the ory—called catastrophism—could n’t pos si - bly be right. Catastrophism claimed that all of the changes in the earth’s sur face were the re - sult of sudden, vio lent (cat astrophic) changes. (Great floods carved out valleys in hours. Great wrenchings shoved up moun tains overnight.) Hutton re alized that no cata strophic event could explain the roll ing hills and me ander ing river valleys he hiked across and studied. It was one thing to say that an exist ing popu lar theory was wrong. But it was quite an - other to prove that it was wrong or to suggest a replace ment theory that better explained Earth’s actual surface. Hutton’s search broad ened as he struggled to discover what forces actu ally formed the hills, moun tains, valleys, and plains of Earth. Late that summer Hutton stopped at a small stream tumbling out of a steep can yon. Without thinking, he bent down and picked up a handful of tiny pebbles and sand from the 51 52 Erosion of the Earth

streambed. As he sifted these tiny rocks be tween his fingers, he re al ized that these peb bles had drifted down this small stream, crashing and breaking into smaller pieces as they went. They used to sit somewhere up higher on the long ridge before him. This stream was carry ing dirt and rock from hilltop to valley floor. This stream was re- shaping the en tire hillside—slowly, grain by grain, day by day. Not cata stroph i cally as geol o gists claimed. The earth, Hutton real ized, was shaped slowly, not overnight. Rain pounding down on hills pulled parti cles of dirt and rock down into streams and then down to the plains. Streams gouged out channels, gullies, and valleys bit by bit, year by year. The wind tore at hills in the same way. The forces of na ture were ev ery where tearing down the earth, lev eling it out. Nature did this not in a day, but over countless centu ries of relent less, steady work by wind and water. Then he stopped. If that were true, why hadn’t nature already leveled out the earth? Why weren’t the hills and mountains worn down? There must be a second force that builds up the land, just as the forces of nature tear it down. For days James Hutton hiked and pondered. What built up the earth? It finally hit him: the heat of Earth’s core built up hills and mountains by pushing outward. Mountain ranges were forced up by the heat of the earth. Wind and rain slowly wore them back down. With no real begin ning and no end, these two great forces struggled in dynamic bal ance over eons, the real time scale for geo logic study. With that great discov ery, James Hutton forever changed the way geol o gists would look at the earth and its processes, and he completely changed human kind’s sense of the scale of time required to bring about these changes.

Fun Facts: Millions of years ago flowing water eroded the surface of Mars, leav ing behind the gul lies, banks, and dry riverbeds scien tists have found there. Now Mar’s at mosphere is too thin to sup port liquid wa ter. A cup of water on Mars would instantly vapor ize and vanish, blown away by the so lar winds.

More to Ex plore

More to Explore Baxter, Ste phen. Ages in Chaos : James Hutton and the Discov ery of Deep Time. New York: Forge Books, 2004. Geo logic So ci ety of Lon don. James Hutton—Present and Future . London: Geo logic So ci ety of Lon don, 1999. Gould, Stephen. Time’s Arrow, Time’s Cycle: Myth and Meta phor in the Discov ery of Geo log i cal Time. Cam bridge, MA: Harvard Univer sity Press, 1997. Hutton, James. Theory of the Earth. Whitefish, MT: Kessinger Publish ing, 2004. McIntyre, Don ald. James Hutton: The Founder of Modern Geol ogy. Ed in burgh, Scot- land: National Museum of Scot land, 2002. Repcheck, Jack. The Man Who Found Time: James Hutton and the Discov ery of Earth’s An tiq uity. Jackson, TN: Perseus Books Group, 2003. Vac ci na tions

Vac ci na tions VAC CI NA TIONS Year of Dis cov ery: 1798

What Is It? Humans can be protected from disease by inject ing them with mild forms of the very dis ease they are trying to avoid. Who Dis cov ered It? Lady Mary Wortley Montagu and Edward Jenner

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Have you had smallpox? Polio? Ty phoid? Prob ably not. However, such infec tious diseases used to plague human kind. The word plague co mes from one of these killer diseases—the bubonic plague. Throughout the fourteenth and fif- teenth cen turies, the plague killed nearly half of the pop u lation of Europe. Smallpox killed over 100,000 peo ple a year for a century and left millions hor ribly scarred and disfig ured. The influ enza epi demic of 1918 killed 25 million worldwide. Polio killed thousands in the early twenti eth century and left millions paralyzed. One simple dis covery not only stopped the spread of each of these diseases, it virtu ally erad i cated them. That dis cov ery was vac ci na tions. Vac ci na tions have saved mil lions of lives and have prevented un imag inable amounts of misery and suffer ing. Ameri can children are now regu larly vacci nated for as many as 15 diseases.

How Were Vac ci na tions Dis cov ered?

How Were Vac ci na tions Dis cov ered? Twenty-four-year-old Lady Mary Wortley Montagu, a well-known Eng lish poet, traveled to Turkey with her husband in 1712 when he became the British ambas sa dor. Lady Mary noticed that na tive popu lations in Turkey didn’t suffered from smallpox, the dread disease that had left her scarred and pockmarked and that killed tens of thousands in England each year. She soon learned that elderly tribal women performed what was called “ingraft ing.” Previ ous Brit ish trav elers had dismissed the practice as a meaning less tribal ritual. Lady Mary suspected that this annual event held the secret to their im munity from smallpox. Village fam ilies would de cide if anyone in the fam ily should have smallpox that year. An old woman ar rived carry ing a nutshell full of infected liq uid. She would open one of the volun teer’s veins with a needle dipped in the liquid, as the family sang and chanted. The infected person stayed in bed for two to three days with a mild fe ver and a slight rash. He or she was then as well as before, never getting a seri ous case of smallpox. Mary won dered if English popu lations could be protected by ingrafting.

53 54 Vac ci na tions

Upon her return to England in 1713, Lady Mary lectured about the poten tial of ingraft - ing. She was dismissed as an untrained and “silly” woman. In early 1714 Caroline, Princess of Wales, heard one of Lady Mary’s talks and approved Lady Mary’s ingraft ing of convicts and orphans. Lady Mary collected the puss from smallpox blisters of sick patients and injected small amounts of the deadly liquid into her test subjects. The death rate of those she in ocu lated was less than one-third that of the general public, and five times as many of her subjects got mild, non-scarring cases. However, there was a prob lem with in graft ing. Inoc u lations with live smallpox viruses were danger ous. Some patients died from the injec tions that were supposed to protect them. Enter Edward Jenner, a young English surgeon, in 1794. Living in a rural commu nity, Jenner noticed that milkmaids al most never got smallpox. However, virtu ally all milkmaids did get cowpox, a dis ease that caused mild blis tering on their hands. Jen ner the o rized that cowpox must be in the same family as smallpox and that getting mild cow pox was like in - graft ing and made a person immune to the deadly smallpox. He tested his theory by inject ing 20 children with liquid taken from the blisters of a milkmaid with cowpox. Each infected child got cowpox. Painful blis ters formed on their hands and arms, lasting sev eral days. Two months later, Jenner injected live smallpox into each of his test chil dren. If Jen- ner’s theory was wrong, many of these children would die. However, none of his test children showed any sign of smallpox. Jenner invented the word “vac ci na tion” to describe his process when he announced his results in 1798. Vacca is the Latin word for cow; vac cinia is Latin for cowpox.

Fun Facts: The World Health Orga ni za tion declared smallpox erad i- cated in 1979, and the Presi dent George H. Bush said that since then author i ties have not de tected a sin gle nat u ral case of the dis ease in the world.

More to Ex plore

More to Explore Asimov, Isaac. Asimov’s Chronol ogy of Science and Dis covery . New York: Harper & Row, 1989. Clark, Donald. En cy clo pe dia of Great In ven tors and Dis cov er ies. London: Marshall Caven dish Books, 1993. Dyson, James. A His tory of Great Inven tions . New York: Carroll & Graf Pub lishers, 2001. Haven, Kendall, and Donna Clark. 100 Most Popu lar Scien tists for Young Adults. Englewood, CO: Li brar ies Un lim ited, 1999. Vare, Ethlie Ann, and Greg Ptacek. Moth ers of In ven tion. New York: William Mor- row, 1989. Yenne, Bill. 100 Inven tions That Shaped World History . New York: Bluewood Books, 1993. Infra red and Ultra vi o let

Infrared and Ul tra vi o let INFRARED & ULTRA VIOLET Years of Dis covery: 1800 and 1801

What Is It? Energy is radi ated by the sun and other stars outside of the narrow vis i ble spec trum of col ors. Who Dis cov ered It? Freder ick Herschel (IR) and Johann Ritter (UV)

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? In fra red and ul tra vi o let ra di a tion are key parts of our sci en tific de vel op ment over the past 200 years. Yet until 1800 it never occurred to anyone that radi a tion could exist outside the narrow band that human eyes de tect. The discov ery of in frared and ultra vi o let light expanded science’s view beyond the vis ible light to the whole radi a tion spectrum, from radio waves to gamma rays. In fra red (IR) ra di a tion has been key to many as tro nom i cal dis cov er ies. In ad di tion, earth science uses IR to mea sure heat in stud ies of every thing from ocean temper atures to forest health. IR sensors power burglar alarms, fire alarms, and police and fire infra red de - tec tors. Biol o gists have discov ered that many birds and insects de tect IR radi a tion with their eyes. Ultra vi o let light (UV) led to a better under stand ing of solar radi a tion and to high-energy parts of the spectrum, including X-rays, microwaves, and gamma rays.

How Was It Discov ered?

How Was It Discov ered? Freder ick Herschel was born in Hanover, Germany, in 1738. As a young man, he grew into a gifted musi cian and astron o mer. It was Herschel who discov ered the planet Uranus in 1781, the first new planet discov ered in almost 2,000 years. In late 1799 Herschel be gan a study of solar light. He often used color filters to isolate parts of the light spectrum for these studies and noted that some filters grew hotter than others. Curi ous about this heat in so lar radi a tion, Herschel won dered if some col ors natu rally car ried more heat than others. To test this idea, Herschel built a large prism. In a darkened room, he projected the prism’s rainbow light spectrum onto the far wall and carefully measured the temper a ture inside each of these sep a rate col ored light beams. Herschel was sur prised to find that the temper a ture rose steadily from vio let (coolest) to a maxi mum in the band of red light. On a sudden impulse, Herschel placed a thermom e ter in the dark space right next to the band of red light (just be yond the light spectrum). This thermom e ter should have stayed cool. It was not in any direct light. But it didn’t. This ther mom e ter reg is tered the most heat of all. 55 56 Infrared and Ul tra vi o let

Herschel was amazed. He guessed that the sun ra di ated heat waves along with light waves and that these invis i ble heat rays refract slightly less while travel ing through a prism than do light rays. Over the course of sev eral weeks, he tested heat rays and found that they re fracted, re flected, bent, etc., ex actly like light. Be cause they ap peared be low red light, Herschel named them in fra red (mean ing below red). Johann Ritter was born in 1776 in Ger many and became a natu ral science philos o pher. His cen tral be liefs were that there was unity and sym metry in na ture and that all nat u ral forces could be traced back to one prime force, Urkraft. In 1801, Ritter read about Herschel’s discov ery of infra red radi a tion. Ritter had worked on sunlight’s effect on chemi cal reac tions and with electro chem is try (the effect of elec tri cal cur rents on chem i cals and on chemi cal re actions). Dur ing this work he had tested light’s effect on sil ver chloride and knew that ex po sure to light turned this chemi cal from white to black. (This discov ery later became the basis for photography.) Ritter decided to du pli cate Herschel’s ex per i ment, but to see if all col ors dark ened sil - ver chloride at the same rate. He coated strips of paper with silver chloride. In a dark room he re peated Herschel’s set up. But in stead of mea sur ing tem per a ture in each color of the rainbow spectrum projected on wall, Ritter timed how long it took for strips of silver chloride pa per to turn black in each color of the spectrum. He found that red hardly turned the paper at all. He also found that vio let darkened pa - per the fast est. Again mimick ing Herschel’s exper i ment, Ritter placed a silver chlo ride strip in the dark area just beyond the band of vio let light. This strip blackened the fastest of all! Even though this strip was not exposed to visi ble light, some ra di ation had acted on the chemi cals to turn them black. Ritter had dis cov ered ra di a tion be yond vi o let (ul tra vi o let) just as Herschel had dis cov - ered that radi a tion existed below the red end of the visi ble spectrum (infrared).

Fun Facts: A TV remote control uses infra red light to adjust the volume or change the channel.

More to Ex plore

More to Explore Herschel, Fred er ick. Pre lim i nary Dis course on the Study of Nat u ral Phi los o phy. Do- ver, DE: Ada mant Media, 2001. ———. Trea tise on As tron omy. Dover, DE: Ada mant Media, 2001. Herschel, John. Aspects of the Life and Thought of Sir John Freder ick Herschel. New York: Arno Press, 1994. Kaufl, Hans. High Res o lu tion In fra red Spec tros copy in As tron omy. New York: Springer-Verlag, 2003. Rob in son, Mi chael. Ripples in the Cosmos . Collingdale, PA: Diane Publish ing, 2000. An es the sia

An es the sia ANESTHESIA Year of Dis cov ery: 1801

What Is It? A medi ca tion used during surgery that causes loss of awareness of pain in pa tients. Who Dis cov ered It? Humphry Davy

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? An es the sia cre ated safe sur gery and made many med i cal and den tal op er a tions prac ti - cal and plau sible. The trauma suffered by patients from the pain of an oper a tion was often so danger ous that it kept doctors from attempt ing many surgi cal proce dures. That pain also kept many se verely ill pa tients from seeking medical help. Anes the sia elimi nated much of the pain, fear, anxi ety, and suffer ing for medi cal and dental patients during most proce dures and gave the medi cal profes sion a chance to develop and re fine the proce dures that would save countless lives. An es the si ol ogy is now a ma jor med i cal spe cialty and an im por tant po si tion in ev ery oper at ing room. While it is proba ble that new drugs and new types of anes the sia will be developed in the coming decades, this im portant aspect of med icine will be with us forever.

How Was It Discov ered?

How Was It Discov ered? The word an es the sia, from the Greek words meaning “lack of sensa tion,” was coined by Oli ver Wendell Holmes (father of the supreme court chief justice by the same name) in 1846. How ever, the con cept of an es the sia is mil len nia old. An cient Chi nese doc tors de vel oped acu- puncture techniques that blocked the transmis sion of pain sensa tions to the brain. Ancient Romans and Egyptians used mandrake (the root of the mandragora plant) to induce uncon - sciousness. Euro pean doc tors in the middle ages also fa vored mandrake. Inca shamans chewed coca leaves and spit the juice (co caine) into wounds and cuts to numb their pa tients’ pain. Three nine teenth-cen tury sci en tists each laid claim to the med i cal dis cov ery of modern anes - thesia. None of them deserves the credit because Humphry Davy had already earned that distinc tion. Scottish obste trician Sir Young Simpson was the first to exper i ment with chloro form. He observed that patients who inhaled a few breaths of the gas (a wad of cotton soaked in chloro form was placed under the nose) quickly be came re laxed and calm, and were soon uncon scious. His use of the drug drew no atten tion until, in 1838, Queen Victo ria asked for Simpson and his chloro form for the birth of her seventh child. Chloro form’s greatest use came during the Ameri can Civil War. Southern cotton was of ten traded in Eng land for med i cines—in clud ing chlo ro form—that be came a staple of 57 58 An es the sia

bat tle field op er at ing tents for South ern doc tors. Af ter the war, chlo ro form con tin ued to enjoy some popu larity—es pe cially in the South—until syn thetic drugs were devel oped in the early twen ti eth cen tury. Geor gia physi cian Crawford Long was the first to use ether dur ing an oper a tion. In 1842 he re moved a neck tu mor from James Venable, a local judge. The oper a tion went perfectly and the judge felt no pain. But Long never bothered to publi cize his success. Two years later Boston dentist Horace Wells took up the notion of using ether to dull op- era tion pain. Wells mistak enly turned off the gas too soon. His patient sat up and screamed. The crowd of observ ing doctors scoffed and called Well’s claims for ether a hoax. One year later (1845), Boston dentist William Morton gave ether another try. Morton’s op er a tion went flaw lessly. Only af ter Mor ton’s sec ond suc cess ful pub lic op er a tion with ether, and only after he had published several arti cles touting the glo ries of ether, did doctors across America—and then Europe—turn to ether as their primary anes thetic. However, none of these men was the first to discover modern medi cal anes the sia. In 1801, English scien tist Humphry Davy was ex peri ment ing with gasses when he combined nitro gen and oxy gen to produce nitrous oxide. Davy tested the result ing color less gas and eventu ally took sev eral deep breaths. He re ported a soar ing eupho ria that soon passed into an un control la - ble outburst of laughter and sobbing until he passed out (it made him un conscious). Davy named the stuff laugh ing gas and noted its tendency to make him unaware of pain. Davy recom mended it for use as an anes thetic during med ical and dental pro cedures. Even though doctors took no note of his discov ery, Davy’s work is the first scien tific identi - fica tion and test ing of an anesthetic.

Fun Facts: The common phrase “biting the bul let” dates from the days be fore anes thet ics were avail able on the bat tle field. Bit ing on the soft lead of a bullet ab sorbed the pressure of the bite without dam aging a soldier’s teeth.

More to Ex plore

More to Explore Asimov, Isaac. Asimov’s Chronol ogy of Science and Dis covery . New York: Harper & Row, 1989. Dyson, James. A His tory of Great Inven tions . New York: Carroll & Graf Pub lishers, 2001. Fradin, Dennis. We Have Conquered Pain: The Dis covery of Anes the sia . New York: Simon & Schuster Children’s, 1996. Fullmer, June. Young Humphry Davy: The Mak ing of an Ex peri men tal Chemist. Phil - a del phia: Amer i can Philo soph i cal So ci ety, 2000. Ga las, Ju dith. An es thet ics: Sur gery With out Pain. New York: Thomson Gale, 1995. Knight, David. Humphry Davy: Science and Power. New York: Cambridge Univer - sity Press, 1998. Lace, William. An es thet ics. New York: Lu cent Books, 2004. Radford, Ruby. Prelude to Fame: Crawford Long’s Discov ery of Anaes the sia . At- lanta, GA: Geron-X, 1990. Atoms

At oms ATOMS Year of Dis cov ery: 1802

What Is It? An atom is the small est par ti cle that can ex ist of any chemi cal el e ment. Who Dis cov ered It? John Dalton

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The modern worlds of chemis try and physics depend on knowing and studying the universe of atoms. But no one could actu ally see an atom until the inven tion of the electron micro scope in 1938. Cen turies before that, atoms were well known and were an impor tant part of chem istry and phys ics research. It was John Dalton who de fined the atom, allow ing scien tists to being seri ous study at the atomic level. An atom is the smallest parti cle of any ele ment and the basic building block of matter. All chemi cal compounds are built from combinations of atoms. Since atoms are the key to under stand ing chemis try and physics, Dalton’s discov ery of the atom ranks as one of the great turning points for science. Because of this discov ery, Dal- ton is of ten called the fa ther of modern physical science.

How Was It Discov ered?

How Was It Discov ered? In the fifth century B.C., Leucippus of Miletus and Democritus of Abdera the o rized that each form of mat ter could be bro ken into smaller and smaller pieces. They called that smallest parti cle that could no longer be broken into smaller pieces an atom. Ga li leo and Newton both used the term atom in the same general way. Robert Boyle and Antoine Lavoisier were the first to use the word el e ment to describe one of the newly discov ered chemi cal substances. All of this work, however, was based on general philosoph i cal theory, not on scien tific observation and evidence. John Dalton was born in 1766 near Man ches ter, England, and received a strict Quaker up bring ing. With lit tle for mal ed u ca tion, he spent 20 years study ing me te o rol ogy and teaching at reli gious, college-level schools. Near the end of this period, Dalton joined, and presented a vari ety of papers to, the Philosoph i cal Soci ety. These included papers on the barom e ter, the ther mom e ter, the hy grom e ter, rain fall, the for ma tion of clouds, evap o ra tion, atmo spheric moisture, and dew point. Each paper pre sented new theories and advanced research results. Dal ton quickly became fa mous for his in no vative thinking and shifted to science research full time. In 1801 he turned his atten tion from the study of atmo spheric gasses to 59 60 At oms

chem i cal com bi na tions. Dal ton had no ex pe ri ence or train ing in chem is try. Still, he plowed confi dently into his studies. By this time al most 50 chem i cal el ements had been dis cov ered—met als, gas ses, and non met als. But sci en tists study ing chem is try were blocked by a fun da men tal ques tion they couldn’t answer: How did ele ments ac tually combine to form the thousands of com pounds that could be found on Earth? For exam ple, how did hydro gen (a gas) combine with oxy gen (another gas) to form water (a liquid)? Further, why did exactly one gram of hydro gen al - ways combine with exactly eight grams of oxygen to make water—never more, never less? Dalton studied all of the chemi cal reac tions he could find (or create), trying to develop a gen eral the ory for how the fun da men tal par ti cle of each el e ment be haved. He com pared the weights of each chemi cal and the likely atomic struc ture of each el e ment in each com - pound. After a year of study, Dalton decided that these compounds were defined by simple nu mer ical ratios by weight. This de cision allowed him to de duce the number of parti cles of each ele ment in vari ous well-known compounds (water, ether, etc.). Dal ton the o rized that each el e ment con sisted of tiny, in de struc ti ble par ti cles that were what combined with other ele ments to form com pounds. He used the old Greek word, atom, for these par ti cles. But now it had a spe cific chemical meaning. Dalton showed that all atoms of any one ele ment were identi cal so that any of them could combine with the atoms of some other ele ment to form the known chem ical compounds. Each compound had to have a fixed number of atoms of each ele ment. Those fixed ratios never changed. He deduced that compounds would be made of the mini mum number possi ble of atoms of each ele ment. Thus water wouldn’t be H4O2 be cause H2O was simpler and had the same ratio of hydro gen and oxy gen at oms. Dalton was the first to use letter symbols (H, O, etc.) to repre sent the vari ous ele ments. Sci en tists readily ac cepted Dal ton’s the o ries and dis cov er ies, and his con cepts quickly spread across all West ern sci ence. We still use his con cept of an atom today.

Fun Facts: The smallest atom is the hydro gen atom, with just one elec - tron circling a single proton. The largest natu rally occur ring atom is the uranium atom, with 92 electrons circling a nucleus stuffed with 92 protons and 92 neutrons. Larger atoms have been arti fi cially created in the lab but do not occur natu rally on earth.

More to Ex plore

More to Explore Greenway, Frank. John Dal ton and the Atom. Ithaca, NY: Cornel Univer sity Press, 1997. Lewis, Spencer. The Mystery of John Dalton and His Alchemy Laws. Whitefish, MT: Kessinger, 2005. Millington, J. John Dal ton. London: AMS Press, 1996. Patterson, Eliz a beth. John Dalton and the Atomic Theory: The Biog ra phy of a Natu ral Phi los o pher. New York: Doubleday, 1996. Smith, Robert. Memoir of John Dalton and History of the Atomic Theory Up to His Time. Dover, DE: Ada mant Media, 2005. Smyth, A. L. John Dal ton: 1766–1844. New York: Do ver, 1998. Elec tro chem i cal Bond ing

Elec tro chem i cal Bond ing ELECTROCHEMICAL BONDING Year of Dis cov ery: 1806

What Is It? Mo lec u lar bonds be tween chem i cal el e ments are elec tri cal in na ture. Who Dis cov ered It? Humphry Davy

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Davy discov ered that the chemi cal bonds between indi vid ual atoms in a mol ecule are electri cal in nature. We now know that chemi cal bonds are created by the sharing or transfer of elec tri cally charged par ti cles—elec trons—be tween at oms. In 1800, the idea that chem is - try somehow involved elec tric ity was a radical discovery. Davy’s dis covery started the modern field of elec trochem istry and rede fined science’s view of chemi cal reac tions and how chemi cals bond together. Finally, Davy used this new concept to discover two new (and impor tant) ele ments: sodium and potassium.

How Was It Discov ered?

How Was It Discov ered? Humphry Davy was born in 1778 along the rugged coast of Cornwall, England. He re - ceived only mini mal school ing and was mostly self-taught. As a young teen ager, he was ap- prenticed to a surgeon and apothe cary. But the early writings of famed French scien tist Antoine Lavoisier sparked his inter est in science. In 1798 Davy was offered a chance by wealthy ama teur chemist Thomas Beddoes to work in Bristol, England, at a new lab Beddoes built and funded. Davy was free to pursue chemis try-re lated science whims. He exper i mented with gases in 1799, thinking that the best way to test these col orless creations was to breathe them. He sniffed ni trous oxide (N2O) and passed out, remem ber ing nothing but feeling happy and power ful. After he reported its effect, the gas quickly became a popu lar party drug under the name “laughing gas.” Davy used ni trous oxide for a wisdom tooth ex trac tion and felt no pain. Even though he re ported this in an arti cle, it was another 45 years before the med ical profes sion fi nally used ni trous oxide as its first anes thetic. Davy also exper i mented with carbon diox ide. He breathed it and almost died from carbon diox ide poison ing. A born showman, movie-star handsome, and always fashion ably dressed, Davy delighted in staging grand demon stra tions of each exper i ment and discov ery for thrilled audi ences of public admirers.

61 62 Elec tro chem i cal Bond ing

In 1799, Italian Alessandro Volta invented the battery and cre ated the world’s first man-made electri cal current. By 1803, Davy had talked Beddoes into building a giant “Vol- taic Pile” (battery) with 110 double plates to provide more power. Davy turned his full at ten tion to ex peri menting with bat teries. He tried dif ferent metals and even char coal for the two elec trodes in his battery and exper i mented with differ ent liq- uids (wa ter, ac ids, etc.) for the liq uid (called an elec tro lyte) that filled the space around the battery’s plates. In 1805 Davy noticed that a zinc electrode oxi dized while the battery was connected. That was a chem i cal re ac tion tak ing place in the pres ence of an elec tri cal cur rent. Then he no ticed other chemi cal re ac tions tak ing place on other elec trodes. Davy re al ized that the bat tery (elec tric cur rent) was caus ing chem i cal reactions to happen. As he ex per i mented with other elec trodes, Davy be gan to re al ize the elec tri cal na ture of chemi cal re actions. He tried a wide va ri ety of ma te ri als for the two elec trodes and dif fer - ent liq uids for the electrolyte. In a grand demon stra tion in 1806, Davy passed a strong elec tric current through pure water and showed that he produced only two gasses—hy dro gen and oxy gen. Wa ter mole - cules had been torn apart by an electric current. This demon stra tion showed that an electri - cal force could tear apart chem i cal bonds. To Davy this meant that the origi nal chemi cal bonds had to be electri cal in nature or an electric current couldn’t have ripped them apart. Davy had discov ered the ba sic nature of chem ical bond ing. Chemi cal bonds were some how electri cal. This dis cov ery radi cally changed the way sci en tists viewed the for ma - tion of mole cules and chemical bonds. Davy con tin ued ex per i ments, pass ing elec tri cal cur rents from elec trode to elec trode through almost every mate rial he could find. In 1807 he tried the power of a new battery with 250 zinc and copper plates on caustic potash and isolated a new ele ment that burst into brilliant flame as soon as it was formed on an elec trode. He named it po tas sium. A month later he isolated so dium. Davy had used his grand discov ery to discover two new elements.

Fun Facts: A popu lar use of electro chem i cal bonding is in cookware. The pro cess unites the an od ized sur face with the alu mi num base, cre at - ing a nonporous surface that is 400 percent harder than alumi num.

More to Ex plore

More to Explore Bow ers, Brian, ed. Cu ri os ity Per fectly Sat is fied: Far a day’s Trav els in Eu rope 1813–1815. Phil a del phia: In sti tute of Elec tri cal Engineers, 1996. Davy, John, ed. Collected Works of Sir Humphry Davy. Dorset, England: Thoemmes Con tin uum, 2001. Fullmer, June. Young Humphry Davy: The Mak ing of an Ex peri men tal Chemist. Phil - a del phia: Amer i can Philo soph i cal So ci ety, 2000. Golinski, Jan. Science as Public Culture: Chemis try and Enlight en ment in Britain, 1760–1820. New York: Cambridge Univer sity Press, 1999. Knight, David. Humphry Davy: Science and Power. Ames, IA: Blackwell Publish ers, 1995. The Ex is tence of Mol e cules

The Ex is tence of Mol e cules THE EX IS TENCE OF MOL E CULES Year of Dis cov ery: 1811

What Is It? A mol ecule is a group of attached at oms. An atom uniquely identi - fies one of the 100+ chemi cal ele ments that make up our planet. Bonding a number of differ ent atoms together makes a mole cule, which uniquely identi fies one of the many thou sands of substances that can exist. Who Dis cov ered It? Amedeo Avoga dro

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? If at oms are the ba sic build ing block of each el ement, then mol ecules are the ba sic building blocks of each substance on Earth. Scien tists were stalled by their inabil ity to accu - rately imag ine—let alone de tect—par ti cles as small as an atom or a mol e cule. Many had theo rized that some tiny parti cle (that they called an atom) was the smallest possi ble parti cle and the basic unit of each ele ment. However, the sub stances around us were not made of indi vid ual el e ments. Sci en tists were at a loss to explain the basic nature of substances. Avo ga dro’s dis cov ery cre ated a ba sic un der stand ing of the re la tion ship be tween all of the millions of substances on Earth and the few basic ele ments. It adjusted exist ing theory to con clude that every liter of gas (at the same tem per ature and pressure) had ex actly the same num ber of mol e cules in it. This dis cov ery al lowed sci en tists to make crit i cal cal cu la tions with and about gasses and allowed scien tists to under stand the nature of all substances. Avoga dro’s discov ery (and the re lated Avoga dro’s Number) have become one of the cor- nerstones of organic and inor ganic chem istry as well as the ba sis for the gas laws and much of the de vel op ment of quan ti ta tive chem is try.

How Was It Discov ered?

How Was It Discov ered? In the spring of 1811, 35-year-old col lege profes sor Amedeo Avoga dro sat in his class- room scowling at two scien tific papers laid out on his desk. Avoga dro taught natu ral science classes at Vercelli College in the Italian mountain town of Turin. Twenty-five students sat each day and listened to Profes sor Avoga dro lecture, discuss, and quiz them on whatever as pects of sci ence caught his fancy. This day he read these two papers to his class, claimed that he saw an impor tant mystery in them, and challenged his students to find it. 63 64 The Ex is tence of Mol e cules

In the two papers, the English chemist, Dalton, and the French chemist, Gay-Lussac, each described an exper i ment in which they combined hydro gen and oxy gen at oms to create water. Both re ported that it took exactly two liters of gas eous hydro gen at oms to combine with exactly one liter of oxy gen atoms to produce exactly two liters of gaseous water vapor. Dalton claimed that this exper i ment proved that water is the combi na tion of two atoms of hy drogen and one atom of oxy gen. Gay-Lussac also claimed it proved that a liter of any gas had to contain exactly the same number of atoms as a liter of any other gas, no matter what gas it was. These stud ies were her alded as major breakthroughs for chemi cal study. But from his first read ing, Pro fes sor Avo ga dro was both ered by a nag ging con tra dic tion. Both Dalton and Gay-Lus sac started with exactly two liters of hydro gen and one li ter of ox y gen. That’s a total of three liters of gas. But they both ended with only two li ters of water vapor gas. If every liter of every gas has to have exactly the same number of atoms, then how could all the atoms from three liters of gas fit into just two liters of wa ter va por gas? The Turin cathe dral bell chimed midnight before the answer struck Avoga dro’s mind. Dal ton and Gay-Lus sac had used the wrong word. What if they had each substi tuted “a group of attached at oms” for atom? Avo ga dro cre ated the word mol e cule (a Greek word meaning, “to move about freely in a gas”) for this “group of attached at oms.” Then he scratched out equations on pa per until he found a way to account for all of the atoms and mole cules in Dalton’s and Gay-Lussac’s exper i ments. If each mol e cule of hydro gen contained two atoms of hydro gen, and each mol e cule of ox y gen contained two atoms of ox y gen, then—if each mol e cule of wa ter va por contained two atoms of hydro gen and one atom of oxy gen, as both scien tists reported—each liter of hydro gen and each liter of oxy gen would have exactly the same number of mol e cules as each of the two result ing liters of water vapor (even though they contained a different number of atoms)! And so it was that, with out ever touching a test tube or chemi cal exper i ment of any kind, without even a background in chemis try, Amedeo Avoga dro discov ered the exis tence of mol e cules and cre ated the ba sic gas law—ev ery li ter of a gas con tains the same number of mol e cules of gas.

Fun Facts: The smallest mole cule is the hydro gen mole cule—just two protons and two elec trons. DNA is the largest known nat u rally occur ring mole cule, with over four billion atoms—each contain ing a number of protons, neu trons, and electrons.

More to Ex plore

More to Explore Adler, Robert. Sci ence Firsts, New York: John Wiley & Sons, 2002. Chang, Laura, ed. Sci en tists at Work. New York: McGraw-Hill, 2000. Downs, Robert. Landmarks in Science . Englewood, CO: Librar ies Unlim ited, 1996. Ha ven, Kend all. Mar vels of Sci ence. Englewood, CO: Librar ies Unlim ited, 1994. Morselli, Mario. Amedeo Avo ga dro. New York: D. Reidel, 1995. Elec tro mag ne tism

Elec tro mag ne tism ELECTROMAGNETISM Year of Dis cov ery: 1820

What Is It? An elec tric cur rent creates a mag netic field and vice versa. Who Dis cov ered It? Hans Oers ted

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Before 1820, the only known mag netism was the natu rally occur ring magne tism of iron magnets and of lodestones—small, weak direc tion finders. Yet the modern world of elec tric motors and elec tric gen er at ing power plants is mus cled by pow er ful electro mag - nets. So is ev ery hair dryer, mixer, and wash ing ma chine. Our in dustry, homes, and lives depend on electric motors—which all depend on electromagnetism. This 1820 discov ery has become one of the most impor tant for defin ing the shape of modern life. Oers ted’s discov ery opened the door to undreamed of possi bil i ties for re search and scien tific advance ment. It made possi ble the work of electro mag netic giants such as An dre Am pere and Michael Faraday.

How Was It Discov ered?

How Was It Discov ered? Hans Oersted was born in 1777 in southern Denmark. He studied science at the univer - sity, but leaned far more toward philos o phy. Oersted adopted the philos o phy teachings of John Ritter, who advo cated a nat u ral sci ence be lief that there was unity in all natu ral forces. Oers ted be lieved that he could trace all nat u ral forces back to the Urkraft, or pri mary force. When he was finally given a science teaching posi tion (in 1813), he focused his research efforts on find ing a way to trace all chemi cal re ac tions back to Urkraft in or der to cre ate a natural unity in all of chemistry. Re search and in ter est in elec tric ity mush roomed af ter Benjamin Frank lin’s ex per i - ments with static elec tric ity and sparks of energy created with Leyden jars. Then, in 1800, Volta invented the battery and the world’s first contin u ous flow of electric current. Electric - ity became the scien tific wonder of the world. Sixty-eight books on electric ity were published between 1800 and 1820. Only a few sci en tists sus pected that there might be a con nec tion be tween elec tric ity and magne tism. In 1776 and 1777 the Bavar ian Academy of Sciences offered a prize to anyone who could answer the question: Is there a physi cal anal ogy between electri cal and magnetic force? They found no winner. In 1808, the London Scien tific Soci ety made the same offer. Again there was no winner.

65 66 Elec tro mag ne tism

In the spring of 1820, Hans Oers ted was giv ing a lecture to one of his classes when an amazing thing happened. He made a grand discov ery—the only major scien tific discov ery made in front of a class of students. It was a simple demon stra tion for gradu ate-level students of how electric current heats a plati num wire. Oersted had not focused his research on either electric ity or mag netism. Neither was of partic u lar inter est to him. Still, he hap pened to have a needle magnet (a compass needle) nearby on the table when he conducted his demonstration. As soon as Oers ted con nected bat tery power to his wire, the com pass needle twitched and twisted to point perpen dic u lar to the plati num wire. When he discon nected the battery, the needle drifted back to its origi nal position. Each time he ran an electric current through that plati num wire, the nee dle snapped back to its per pen dic u lar po si tion. Oers ted’s stu dents were fas ci nated. Oers ted seemed flus- tered and shifted the talk to another topic. Oersted did not return to this amazing occur rence for three months—until the summer of 1820. He then be gan a se ries of ex per i ments to dis cover if his elec tric cur rent cre ated a force that at tracted the compass nee dle, or re pelled it. He also wanted to try to relate this strange force to Urkraft. He moved the wire above, be side, and be low the com pass nee dle. He re versed the cur rent through his plati num wire. He tried two wires instead of one. With every change in the wire and current, he watched for the effect these changes would produce on the com pass needle. Oers ted fi nally re al ized his elec tric cur rent cre ated both an at trac tive and a re pul sive force at the same time. Af ter months of study, he con cluded that an elec tric cur rent cre ated a mag netic force and that this force was a whole new type of force—radi cally differ ent than any of the forces Newton had described. This force acted not along straight lines, but in a circle around the wire car ry ing an elec tric cur rent. Clearly, he wrote, wires car ry ing an elec tric cur rent showed mag netic prop er ties. The con cept of elec tro mag ne tism had been dis cov ered.

Fun Facts: The au rora bo re alis, or “north ern lights,” are an elec tro mag - netic phe nom e non, caused when elec tri cally charged so lar par ti cles col - lide with Earth’s magnetic field. In the Southern hemisphere these waving curtains of light form around the south pole and are called the au- rora austra lis, or “southern lights.”

More to Ex plore

More to Explore Beau mont, LeIonce. Memoir of Oers ted. Wash ing ton, DC: Smith so nian In sti tu tion, 1997. Brain, R. M., ed. Hans Chris tian Oersted and the Roman tic Quest for Unity. New York: Springer, 2006. Co hen, Ber nard. Rev o lu tions in Sci ence. Cam bridge, MA: Harvard Univer sity Press, 1995. Dibner, Bern. Oers ted and the Dis cov ery of Elec tro mag ne tism. Cam bridge, MA: Burndy Li brary, 1995. Oers ted, Hans. The Discov ery of Electro mag ne tism Made in the Year 1820. London: H. H. Theiles, 1994. First Dino saur Fossil

First Di no saur Fos sil FIRST DINOSAUR FOSSIL Year of Dis cov ery: 1824

What Is It? The first proof that giant dino saurs once walked the earth. Who Dis cov ered It? Gid eon Mantell and Wil liam Buckland

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Most peo ple (and sci entists) assumed that the world and its mix of plants and an imals had always been as it was when these scien tists lived. The discov ery of dino saur fossils destroyed that be lief. This discov ery rep resented the first proof that entire groups of an cient— and now ex tinct—ani mals once roamed Earth. It was the first proof that mas sive beasts (dino saurs) much larger than anything that exists today once existed. This discov ery was a great leap forward for the fields of arche ol ogy and pale on tol ogy —both in their knowl edge as well as in their field tech niques. Dino saurs have proved to be the most dramatic of all relics from the past and have done more to acquaint the ordi nary person with the fact of bio logi cal evolu tion than anything else.

How Was It Discov ered?

How Was It Discov ered? People had always found fossil bones, but none had cor rectly iden tified them as extinct species. In 1677 Eng lishman Rob ert Plot found what 220 years later was iden tified as the end of the thighbone of a giant biped carniv o rous dino saur. Plot gained great fame when he claimed it was the fossil ized testi cles of a giant and said it proved that story giants were real. Science was clearly still in the dark ages until two English men, working inde pend - ently, both wrote arti cles on their discov ery of dino saurs in 1824. They share the credit for dis cov er ing dinosaurs. In 1809 (50 years before Darwin’s discov ery of evo lution) English coun try doctor Gideon Mantell lived in Lewes in the Sus sex district of England. While vis iting a pa tient one day, Mantell’s wife, Mary Ann, took a short stroll and then pre sented him with several puzzling teeth she had found. These massive teeth were obvi ously from an herbi vore but were far too large for any known ani mal. Mantell, an ama teur geol o gist, had been collect ing fossil relics of ancient land an imals for several years but could not iden tify these teeth. He re turned to the site and cor rectly iden ti fied the rock strata as from the Me so zoic era. Thus, the teeth had to be many millions of years old. These teeth were not the first large bones Mantell had found, but they were the most puzzling. Mantell took them to famed French natu ralist, Charles Cuvier, who thought they came from an or di nary rhi noc eros-like an i mal. Mantell set the teeth aside. 67 68 First Di no saur Fos sil

In 1822 Mantell came across the teeth of an iguana and re al ized that these teeth were exact minia tures of the ones he had found 13 years earlier. Com bined with other large bones he had re cov ered from the site, Mantell claimed that he had dis cov ered an an cient, gi ant rep tile that he named ig uano don (“iguana-toothed”). He eagerly published his discov ery in 1824. During this same period William Buckland, a profes sor at Oxford Univer sity, had been collect ing fossils in the Stonesfield region of England. During an 1822 outing he dis covered the jaw and several thighbones of an ancient and giant creature. (It turned out to be the same species dis covered—but not iden tified—by Robert Plot 150 years before.) Buckland de termined from these bones that this mon ster had been a bi ped (two-legged) carni vore. From the bone structure, Buckland claimed that it be longed to the reptile fam ily. Thus he named it megalosaurus (giant lizard) and pub lished a paper on it in 1824. With these two publi ca tions the era of dino saurs had been discovered.

Fun Facts: The word di no saur comes from the Greek words mean ing “ter ri ble liz ard.” Lots of di no saurs were named af ter Greek words that suited their person al ity or appear ance. Velociraptor means “speedy rob- ber” and triceratops means “three-horned head.”

More to Ex plore

More to Explore Cadbury, Deborah. Ter rible Lizard: The First Dino saur Hunters and the Birth of a New Sci ence. New York: Henry Holt, 1995. Dean, Dennis. Gideon Mantell and the Discov ery of Dino saurs . New York: Cam- bridge Univer sity Press, 1999. De bus, Allen. Paleoimagery: The Evolu tion of Dino saurs in Art. Jef fer son, NC: McFarland & Co., 2002. Hartzog, Brooke. Iguano don and Dr. Gideon Mantell. Cherry Hill, NJ: Rosen Group, 2001. Klaver, Jan. Ge ol ogy and Re li gious Sen ti ment: The Ef fect of Geo log i cal Dis cov er ies on English Soci ety between 1829 and 1859. Am ster dam: Brill Ac a demic Publishers, 1997. Knight, David, ed. Ge ol ogy and Min er al ogy Con sid ered with Ref er ence to Nat u ral The ol ogy. Abingdon, Eng land: Taylor & Francis, 2003. Ice Ages

Ice Ages ICE AGES Year of Dis cov ery: 1837

What Is It? Earth’s past includes peri ods of rad ically differ ent climate— ice ages—than the mild pres ent. Who Dis cov ered It? Louis Agassiz

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? It was a rev o lu tion ary idea: Earth’s cli mate had not al ways been the same. Ev ery sci en - tist for thousands of years had assumed that Earth’s climate had remained unchang ing for all time. Then Louis Agassiz dis covered proof that all Europe had once been covered by crushing glaciers. Earth’s climate had not always been as it was now. With that discov ery, Agassiz estab lished the con cept of an ever-changing Earth. This discov ery explained a number of bio log i cal puzzles that had confounded scien - tists for cen tu ries. Agassiz was also the first sci en tist to re cord care ful and ex ten sive field data to support and estab lish a new theory. Agassiz’s work did much to begin the field of geol ogy and our mod ern view of our planet’s history.

How Was It Discov ered?

How Was It Dis cov ered? Louis Agassiz thought of himself as a field geol o gist more than as a college profes sor. During weeks of ram bling hikes through his native Swiss Alps in the late 1820s he noticed sev eral phys i cal fea tures around the front faces of Swiss val ley gla ciers. First, gla ciers wormed their way down val leys that were “U” shaped—with flat valley bottoms. River valleys were always “V” shaped. At first he thought that glaciers natu rally formed in such valleys. Soon he re al ized that the gla ciers, themselves, carved val leys in this characteristic “U” shape. Next he noticed hori zon tal gouges and scratches in the rock walls of these glacier valleys—of ten a mile or more in front of the ac tual gla cier. Fi nally, he be came aware that many of these valleys featured large boulders and rock piles resting in the lower end of the valley where no known force or process could have deposited them. Soon Agassiz real ized that the mountain glaciers he studied must have been much bigger and longer in the past and that they, in some distant past, had gouged out the valleys, carried the rocks that scored the val leys’ rock walls leav ing claw-mark scratches, and depos ited gi ant boulders at their ancient heads.

69 70 Ice Ages

In the early 1830s Agassiz toured Eng land and the north ern Euro pean lowlands. Here, too, he found “U”-shaped valleys, hori zon tal gouges, and scratch marks in valley rock walls, and giant boulders myste ri ously perched in the lower valley reaches. It looked like the sig nature of glaciers he had come to know from his Swiss studies. But there were no glaciers for hun dreds of miles in any direc tion. By 1835, the awe-inspir - ing truth hit him. In some past age, all Europe must have been covered by giant gla ciers. The past must have been rad i cally dif fer ent than the pres ent. Cli mate was not always the same. In order to claim such a revo lu tion ary idea, he had to prove it. Agassiz and several hired assis tants spent two years survey ing Alpine gla ciers and docu ment ing the presence of the telltale signs of past glaciers. When Agassiz released his findings in 1837, geol o gists worldwide were awed. Never before had a re searcher gathered such exten sive and detailed field data to support a new theory. Be cause of the quality of his field data, Agassiz’s con clusions were immediately accepted—even though they radi cally changed all exist ing theo ries of Earth’s past. Agassiz created a vivid picture of ice ages and proved that they had existed. But it was Yugo sla vian phys icist Milutin Milankovich, in 1920, who explained why they hap pened. Milankovich showed that Earth’s orbit is neither circu lar, nor does it re main the same year af ter year and cen tury af ter cen tury. He proved that Earth’s or bit os cil lates be tween be ing more elongated and being more circu lar on a 40,000-year cycle. When its orbit pulled the earth a lit tle far ther away from the sun in win ter, ice ages hap pened. NASA sci en tists con - firmed this theory with research conducted between 2003 and 2005.

Fun Facts: Dur ing the last ice age the North Amer i can gla cier spread south to where St. Louis now sits and was over a mile thick over Minne - sota and the Dako tas. So much ice was locked into these vast glaciers that sea level was almost 500 feet lower than it is today.

More to Ex plore

More to Explore Agassiz, Louis. Louis Agassiz : His Life and Science . Whitefish, MT: Kessinger, 2004. Lee, Jeffery. Great Ge og raphers: Louis Agassiz. New York: Fo cus on Geog raphy, 2003. Lurie, Edward. Louis Agassiz: Life in Science . Balti more, MD: John Hopkins Univer - sity Press, 1998. Tallcott. Emogene. Gla cier Tracks. New York: Lothrop, Lee & Shepard, 2000. Teller, James. Louis Agassiz: Scien tist and Teacher. Colum bus: Ohio State Univer sity Press, 1997. Tharp, Louis. Louis Agassiz : Ad ven tur ous Sci en tist. New York: Little, Brown, 1995. Cal o ries (Units of En ergy)

Calo ries (Units of Energy) CALORIES (Units of Energy) Year of Dis cov ery: 1843

What Is It? All forms of energy and mechan i cal work are equiva lent and can be converted from one form to another. Who Dis cov ered It? James Joule

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? We now know that me chan i cal work, elec tric ity, mo men tum, heat, mag netic force, etc., can be converted from one to an other. There is always a loss in the process, but it can be done. That knowledge has been a tremen dous help for the devel op ment of our indus tries and technol o gies. Only 200 years ago, the thought had not occurred to anyone. James Joule discov ered that every form of energy could be converted into an equiva - lent amount of heat. In so doing, he was the first scien tist to come to grips with the general concept of energy and of how differ ent forms of energy are equiva lent to each other. Joule’s discov ery was an essen tial founda tion for the discov ery (40 years later) of the law of conser - vation of en ergy and for the devel op ment of the field of thermodynamics.

How Was It Discov ered?

How Was It Discov ered? Born on Christmas eve, 1818, James Joule grew up in a wealthy brewing family in Lancashire, England. He studied science with private tutors and, at the age of 20, started to work in the family brewery. Joule’s first self-appointed job was to see if he could con vert the brewery from steam power to new, “modern” electric power. He studied engines and energy supplies. He studied elec tri cal en ergy cir cuits and was fas ci nated to find that the elec tri cal wires grew hot when cur rent ran through them. He re al ized that some of the electri cal en ergy was be ing converted into heat. He felt it was impor tant for him to quantify that electri cal energy loss and began exper - iments on how energy was converted from electric ity to heat. Often he exper i mented with little regard for safety—his or others. More than once, a servant girl collapsed uncon scious from electri cal shocks during these exper i ments. While he never converted the brewery to electri cal power, these exper i ments turned his focus to the process of con verting energy from one form to another. Joule was deeply reli gious, and it seemed right to him that there should be a unity for all the forces of na ture. He sus pected that heat was some how the ul ti mate and nat u ral form for calcu lat ing the equiva lence of dif ferent forms of energy. 71 72 Calo ries (Units of Energy)

Joule turned his atten tion to the conver sion of mechan i cal energy into heat. In real life a moving body (with the mechan i cal energy of momen tum) eventu ally stopped. What happened to its energy? He designed a series of exper i ments using water to measure the conver - sion of mechan i cal motion into heat. Two of Joule’s exper i ments became fa mous. First, he sub merged an air-filled copper cylin der in a tub of wa ter and mea sured the water temper a ture. He then pumped air into the cylin der until it reached 22 atmo spheres of pres sure. The gas law said that the mechan i cal work to cre ate this in creased air pres sure should cre ate heat. But would it? Joule mea sured a 0.285°F rise in wa ter tem per a ture. Yes, me chan i cal energy had been converted to heat. Next, Joule attached paddles onto a verti cal shaft that he lowered into a tub of water. Falling weights (like on a grandfa ther clock) spun the paddles through the tub’s water. This me chan i cal ef fort should be par tially converted to heat. But was it? His results were incon clu sive until Joule switched from water to liquid mercury. With this denser fluid, he easily proved that the mechan i cal effort was converted to heat at a fixed rate. Liquid was heated by merely stir ring it. Joule real ized that all forms of en ergy could be con verted into equiv alent amounts of heat. He published these results in 1843 and intro duced standard heat energy units to use for calcu lat ing these equiva lences. Since then, physi cists and chemists typi cally use these units and have named them joules. Bi ol o gists prefer to use an alter nate unit called the cal o rie (4.18 joules = 1 calo rie). With this dis covery that any form of energy could be converted into an equiva lent amount of heat energy, Joule provided a way to advance the study of energy, mechanics, and technologies.

Fun Facts: The cal o ries on a food pack age are ac tu ally kilocalories, or units of 1,000 calo ries. A kilocalorie is 1,000 times larger than the calo rie used in chemis try and physics. A calo rie is the amount of energy needed to raise the temper a ture of 1 gram of water 1 degree Celsius. If you burn up 3,500 calo ries during exer cise, you will have burned up and lost one pound. However, even vigor ous exer cise rarely burns more than 1,000 cal o ries per hour.

More to Ex plore

More to Explore Cardwell, Donald, ed. The De vel op ment of Science and Tech nology in Nine- teenth-Cen tury Brit ain. Lon don: Ashgate Pub lish ing, 2003. ———. James Joule: A Biog raphy . New York: St. Mar tin’s Press, 1997. Joule, James. The Sci en tific Pa pers of James Prescott Joule. Wash ing ton, DC: Schol- arly Press, 1996. Smith, Crosbie. Sci ence of En ergy. Chicago: Univer sity of Chicago Press, 1999. Steffens, Henry. James Prescott Joule and the Concept of Energy. Sagamore Beach, MA: Wat son Pub lish ing, 1999. Con ser va tion of En ergy

Con ser va tion of En ergy CONSERVATION OF ENERGY Year of Dis cov ery: 1847

What Is It? Energy can nei ther be cre ated nor lost. It may be con verted from one form to another, but the total energy always remains constant within a closed sys tem. Who Dis cov ered It? Hermann von Helmholtz

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Energy is never lost. It can change from one form to another, but the total amount of en ergy never changes. That prin ci ple has al lowed sci en tists and en gi neers to cre ate the power systems that run your lights and house and fuel your car. It’s called conser va tion of energy and is one of the most im portant discov er ies in all sci ence. It has been called the most funda men tal con cept of all nature. It forms the first law of thermo dy namics. It is the key to under stand ing energy conver sion and the interchangeability of differ ent forms of energy. When Hermann von Hemholtz assem bled all of the studies and indi vid ual pieces of infor ma tion to dis cover this princi ple, he changed science and engineering forever.

How Was It Discov ered?

How Was It Discov ered? Born in 1821 in Potsdam, Germany, Hermann von Hemholtz grew up in a fam ily of gold merchants. At the age of 16, he took a govern ment scholar ship to study medi cine in exchange for 10 years of service in the Prussian Army. Offi cially he studied to be a doctor at the Berlin Medi cal Insti tute. However, he often slipped over to Berlin Univer sity to attend classes on chemis try and physiology. While serving in the army, he devel oped a research specialty: proving that the work muscles did was de rived from chemi cal and physi cal princi ples and not from some “unspec - i fied vi tal force.” Many re search ers used “vi tal forces” as a way to ex plain any thing they could n’t really explain. It was as if these “vi tal forces” could per pet u ally create energy out of nothing. Helmholtz wanted to prove that all mus cle-driven motion could be ac counted for by study ing phys i cal (me chan i cal) and chem i cal re ac tions within the mus cles. He wanted to discredit the “vital force” theory. During this effort, he devel oped a deep belief in the con - cept of conser vation of effort and energy. (No work could be cre ated without com ing from some where or lost without going some where.) He stud ied math e mat ics in or der to better de scribe the con ver sion of chemi cal en ergy into kinetic energy (motion and work) and the conver sion of physi cal muscle changes into 73 74 Con ser va tion of En ergy

work in order to prove that all work could be accounted for by these natu ral, physical processes. Helmholtz was able to prove that work could not be contin u ally produced from “nothing.” That dis covery led him to form the princi ple of con ser vation of kinetic energy. He de cided to ap ply this prin ci ple of con ser va tion to a va ri ety of dif fer ent sit u a tions. To do that, he studied the many pieces that had been dis covered by other scien tists—James Joule, Julius Mayer, Pierre Laplace, Antoine Lavoisier, and others who had studied either the conver sion of one form of energy into another or the conser va tion of specific kinds of energy (momentum, for example). Helmholtz augmented exist ing studies with his own exper i ments to show that, time and time again, energy was never lost. It might be con verted into heat, sound, or light, but it could always be found and accounted for. In 1847 Helmholtz re alized that his work proved the gen eral the ory of con ser va tion of energy: The amount of energy in the universe (or in any closed system) always remained constant. It could change be tween forms (elec tric ity, mag ne tism, chemi cal en ergy, ki netic energy, light, heat, sound, poten tial energy, or momen tum), but could neither be lost nor created. The greatest chal lenge to Helmholtz’s theory came from astron o mers who studied the sun. If the sun didn’t cre ate light and heat energy, where did the vast amounts of energy it radi ated come from? It couldn’t be burning it own matter as would a normal fire. Scien tists had al ready shown that the sun would consume itself within 20 mil lion years if it ac tually burned its mass to create light and heat. It took Helmholtz five years to real ize that the answer was gravity. Slowly the sun was collaps ing in on itself, and that grav ita tional force was being converted into light and heat. His answer was accepted (for 80 years—until nuclear energy was discov ered). More impor - tant, the criti cal concept of conser vation of en ergy had been discovered and accepted.

Fun Facts: Conser vation of en ergy plus the Big Bang tell us that all of the en ergy that ever was or ever will be anywhere in the universe was pres ent at the mo ment of the Big Bang. All of the fire and heat burning in ever star, all of the fire and energy in every volcano, all of the energy in the motion of every planet, comet, and star—all of it was re leased at the moment of the Big Bang. Now that must have been one BIG explo sion!

More to Ex plore

More to Explore Cahan, David. Hermann von Helmholtz and the Founda tions of Nineteenth-Cen tury Sci ence. Berke ley: Uni ver sity of Cal i for nia Press, 1996. ———, ed. Sci ence and Cul ture : Pop u lar and Philo soph i cal Es says. Chi cago: Uni- versity of Chicago Press, 1995. Hyder, David. Kant and Helmholtz on the Physi cal Meaning of Geom e try. Berlin: Walter De Gruyter, 2006. McKendrick, John. Hermann Ludwig Ferdinand von Helmholtz. Lon don: Longmans, Green & Co., 1995. Warren, R. M. Helmholtz on Per ception . New York: John Wiley & Sons, 1998. Dopp ler Ef fect

Dopp ler Ef fect DOPPLER EFFECT Year of Dis cov ery: 1848

What Is It? Sound- and light-wave frequen cies shift higher or lower de pend- ing on whether the source is moving toward or away from the observer. Who Dis cov ered It? Chris tian Dopp ler

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The Dopp ler Effect is one of the most pow erful and impor tant con cepts ever discov - ered for as tronomy. This dis covery allowed sci entists to measure the speed and direc tion of stars and galax ies many millions of light years away. It unlocked myster ies of distant galax - ies and stars and led to the discov ery of dark matter and of the actual age and motion of the universe. Doppler’s discov ery has been used in research efforts of a dozen scien tific fields. Few single concepts have ever proved more useful. Doppler’s discov ery is consid ered to be so funda men tal to science that it is included in virtu ally all middle and high school basic science courses.

How Was It Discov ered?

How Was It Discov ered? Aus trian-born Chris tian Dopp ler was a strug gling math e mat ics teacher—strug gling both because he was too hard on his students and earned the wrath of par ents and admin is - trators and because he wanted to fully under stand the geom e try and mathe mat i cal concepts he taught. He drifted in and out of teaching posi tions through the 1820s and 1830s as he passed through his twenties and thirties. Doppler was lucky to land a math teaching slot at Vienna Polytechnic Institute in 1838. By the late 1830s, trains capa ble of speeds in excess of 30 mph were dash ing across the country side. These trains made a sound phenom e non notice able for the first time. Never before had hu mans traveled faster than the slow trot of a horse. Trains allowed people to notice the effect of an object’s movement on the sounds that object produced. Doppler in tently watched trains pass and began to the o rize about what caused the sound shifts he observed. By 1843 Doppler had expanded his ideas to include light waves and de vel oped a gen eral the ory that claimed that an ob ject’s move ment ei ther in creased or decreased the frequency of sound and light it produced as measured by a station ary observer. Doppler claimed that this shift could explain the red and blue tinge to the light of distant twin stars. (The twin circling to ward Earth would have its light shifted to a higher frequency—to ward blue. The other, circling away, would shift lower, toward red.)

75 76 Dopp ler Ef fect

In a pa per he presented to the Bohe mian Scien tific Soci ety in 1844, Doppler presented his theory that the motion of objects moving toward an observer compresses sound and light waves so that they appear to shift to a higher tone and to a higher frequency color (blue). The reverse happened if the object was moving away (a shift toward red). He claimed that this ex plained the often observed red and blue tinge of many distant stars’ light. Actu ally, he was wrong. While tech ni cally correct, this shift would be too small for the instru ments of his day to detect. Doppler was challenged to prove his theory. He couldn’t with light because telescopes and measur ing equipment were not sophis ti cated enough. He de cided to dem onstrate his prin ci ple with sound. In his famed 1845 exper i ment, he placed mu sicians on a railway train playing a single note on their trum pets. Other musi cians, cho sen for their perfect pitch, stood on the station platform and wrote down what note they heard as the train approached and then receded. What the listen ers wrote down was consis tently first slightly higher and then slightly lower than what the moving musi cians actually played. Doppler repeated the exper i ment with a second group of trumpet players on the station platform. They and the moving musi cians played the same note as the train passed. Listen - ers could clearly hear that the notes sounded differ ent. The moving and station ary notes seemed to inter fere with each other, setting up a pulsing beat. Having proved the exis tence of his effect, Doppler named it the Dopp ler Shift. How- ever, he never en joyed the fame he sought. He died in 1853 just as the sci entific commu nity was begin ning to ac cept, and to see the value of, his discovery.

Fun Facts: Doppler shifts have been used to prove that the universe is expand ing. A conve nient analogy for the expan sion of the universe is a loaf of unbaked raisin bread. The raisins are at rest rela tive to one another in the dough before it is placed in the oven. As the bread rises, it also expands, mak ing the space be tween the rai sins increase. If the rai sins could see, they would observe that all the other rai sins were moving away from them although they themselves seemed to be station ary within the loaf. Only the dough—their “universe”—is ex panding.

More to Ex plore

More to Explore Dia gram Group. Facts on File Phys ics Handbook. New York: Facts on File, 2006. Eden, Alec. Search for Christian Doppler . New York: Springer-Verlag, 1997. Gill, T. P. Doppler Effect: An Intro duc tion to the Theory of the Effect. Chevy Chase, MD: Elsevier Science Publish ing, 1995. Haerten, Rainer, et al. Princi ples of Doppler and Color Doppler Imag ing. New York: John Wiley & Sons, 1997. Kinsella, John. Doppler Effect . Cam bridge, England: Salt Pub lishing, 2004. Germ Theory

Germ The ory GERM THEORY Year of Dis cov ery: 1856

What Is It? Micro or gan isms too small to be seen or felt exist every where in the air and cause disease and food spoilage. Who Dis cov ered It? Louis Pasteur

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Yogurt and other dairy products soured and curdled in just a few days. Meat rotted after a short time. Cow’s and goat’s milk had always been drunk as fresh milk. The con sumer had to be near the an imal since milk soured and spoiled in a day or two. Then Louis Pasteur discov ered that micro scopic organ isms floated every where in the air, un seen. It was these micro or gan isms that turned food into deadly, disease-rid den gar - bage. It was these same micro scopic organ isms that entered hu man flesh during oper a tions and through cuts to cause infec tion and disease. Pasteur discov ered the world of micro bi ol - ogy and devel oped the theory that germs cause disease. He also invented pasteur iza tion, a sim ple method for removing these organisms from liquid foods. How Was It Discov ered?

How Was It Discov ered? In the fall of 1856, 38-year-old Louis Pasteur was in his fourth year as Direc tor of Sci- en tific Affairs at the famed Ecole Normale in Paris. It was an hon ored ad min is tra tive po si - tion. But Pas teur’s heart was in pure research chemis try and he was angry. Many sci en tists be lieved that mi cro or gan isms had no par ent or gan ism. In stead, they sponta ne ously gen erated from the de caying mole cules of organic mat ter to spoil milk and rot meat. Felix Pouchet, the leading spokesman for this group, and had just published a paper claim ing to prove this thesis. Pas teur thought Pouchet’s theory was rubbish. Pasteur’s earlier discov ery that micro - scopic live or gan isms (bac te ria called yeasts) were al ways pres ent dur ing, and seemed to cause, the fer men ta tion of beer and wine, made Pas teur sus pect that mi cro or gan isms lived in the air and simply fell by chance onto food and all living matter, rapidly multi ply ing only when they found a decay ing substance to use as nutrient. Two questions were at the center of the argu ment. First, did liv ing microbes re ally float in the air? Second, was it possi ble for microbes to grow sponta ne ously (in a sterile en - viron ment where no mi crobes already existed)? Pasteur heated a glass tube to steril ize both the tube and the air inside. He plugged the open end with guncotton and used a vacuum pump to draw air through the cotton filter and into this ster ile glass tube. 77 78 Germ The ory

Pas teur reasoned that any microbes floating in the air should be con centrated on the outside of the cotton filter as air was sucked through. Bacte rial growth on the filter indi cated microbes floating freely in the air. Bacte rial growth in the sterile inte rior of the tube meant spon ta ne ous generation. After 24 hours the outside of his cotton wad turned dingy gray with bac terial growth while the inside of the tube remained clear. Question number 1 was answered. Yes, micro - scopic organ isms did ex ist, float ing, in the air. Any time they concen trated (as on a cotton wad) they be gan to multiply. Now for question number 2. Pasteur had to prove that micro scopic bacte ria could not spon ta ne ously gen er ate. Pasteur mixed a nutri ent-rich bullion (a favor ite food of hungry bacte ria) in a large beaker with a long, curving glass neck. He heated the beaker so that the bullion boiled and the glass glowed. This killed any bacte ria already in the bul lion or in the air inside the beaker. Then he quickly stoppered this sterile beaker. Any growth in the beaker now had to come from spon ta ne ous generation. He slid the beaker into a small warming oven, used to speed the growth of bacte rial cul tures. Twenty-four hours later, Pas ture checked the beaker. All was crys tal clear. He checked ev ery day for eight weeks. Nothing grew at all in the beaker. Bacte ria did not sponta ne ously gen erate. Pas teur broke the beaker’s neck and let normal, unster il ized air flow into the beaker. Seven hours later he saw the first faint tufts of bacte rial growth. Within 24 hours, the surface of the bul lion was covered. Pouchet was wrong. Without the origi nal airborne microbes floating into con tact with a nutri ent, there was no bacte rial growth. They did not sponta ne ously generate. Pas teur tri um phantly pub lished his dis cov er ies. More im por tant, his dis cov ery gave birth to a brand new field of study, micro bi ol ogy.

Fun Facts: The typi cal household sponge holds as many as 320 million dis ease-caus ing germs.

More to Ex plore

More to Explore Clark, Donald. Ency clo pe dia of Great Inven tors and Discov er ies . London: Marshall Caven dish Books, 1991. Dubos, Rene. Pasteur and Modern Science. Madi son, WI: Science Tech Publish ers, 1998. Dyson, James. A His tory of Great Inven tions . New York: Carroll & Graf Pub lishers, 2001. Fullick, Ann. Louis Pas teur. Portsmouth, NH: Heinemann Library, 2000. Gogerly, Liz. Louis Pas teur. New York: Raintree, 2002. Silverthorne, Eliz a beth. Louis Pas teur. New York: Thomson Gale, 2004. Smith, Linda. Louis Pas teur: Dis ease Fighter. Berkeley Heights, NJ: Enslow Publish - ers, 2001. Yount, Lisa. Louis Pas teur. New York: Thomson Gale, 1995. The The ory of Evo lu tion

The Theory of Evolu tion THE THEORY OF EVOLUTION Year of Dis cov ery: 1858

What Is It? Species evolve over time to best take advan tage of their surround ing envi ron ment, and those species most fit for their envi ron ment survive best. Who Dis cov ered It? Charles Dar win

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Dar win’s theory of evo lution and its con cept of survival of the fittest is the most funda - men tal and im por tant dis cov ery of mod ern bi ol ogy and ecol ogy. Dar win’s dis cov er ies are 150 years old and are still the foun dation of our un derstand ing of the history and evo lution of plant and animal life. Dar win’s dis cov ery an swered count less mys ter ies for an thro pol ogy and pa le on tol ogy. It made sense out of the wide distri bu tion and special design of species and sub species on Earth. While it has always stirred contro versy and oppo si tion, Darwin’s theory has been veri fied and supported by mountains of careful scien tific data over the past 150 years. His books were best sellers in his day and they are still widely read today.

How Was It Discov ered?

How Was It Discov ered? Charles Dar win en tered Cam bridge Univer sity in 1827 to become a priest, but switched to geol ogy and botany. He gradu ated in 1831 and, at age 22, took a posi tion as nat- u ralist aboard the HMS Beagle bound from England for South America and the Pacific. The Beagle’s three-year voy age stretched into five. Dar win for ever mar veled at the un ending vari ety of species in each place the ship visited. But it was their extended stop at the Pa cific Ocean Galapagos Islands that fo cused Dar win’s wonder into a new discovery. On the first island in the chain he visited (Chatham Island), Darwin found two distinct species of tor toise—one with long necks that ate leaves from trees, and one with short necks that ate ground plants. He also found four new species of finches (small, yellow birds com - mon across much of Europe). But these had differ ently shaped beaks from their Eu ropean cousins. The Beagle reached the third Galapagos Island (James Is land) in Octo ber 1835. Here, right on the equator, no day or season seemed any differ ent than any other. As he did every day on shore, Darwin hoisted his backpack with jars and bags for col- lecting samples, a note book for re cording and sketch ing, and his nets and traps and set off across the frightful land scape through twisted fields of crunchy black lava thrown up into giant, ragged waves. Gaping fissures from which dense steam and noxious yellow vapors 79 80 The Theory of Evolu tion

hissed from deep in the rock blocked his path. The broken lava was covered by stunted, sun- burned brushwood that looked far more dead than alive. In a grove of trees filled with chirping birds, Darwin found his thirteenth and fourteenth new species of finches. Their beaks were larger and rounder than any he’d seen on other is lands. More im por tant, these finches ate small red ber ries. Ev ery where else on Earth finches ate seeds. In these is lands some finches ate seeds, some in sects, and some ber ries! More amaz ingly, each spe cies of finch had a beak per fectly shaped to gather the specific type of food that spe cies pre ferred to eat. Darwin began to doubt the Christian teaching that God created each species just as it was and that species were unchang ing. He deduced that, long ago, one vari ety of finch arrived in the Galapagos from South America, spread out to the indi vid ual islands, and then adapted (evolved) to best survive in its partic u lar envi ron ment and with its partic u lar sources of food. These findings he reported in his book, A Nat u ral ist’s Voy age on the Beagle. After his re turn to England, Darwin read the collected essays of econ o mist Thomas Malthus, who claimed that, when human popu la tions could not produce enough food, the weakest people starved, died of disease, or were killed in fighting. Only the strong survived. Dar win re alized that this con cept should ap ply to the animal world as well. He blended this idea with his expe ri ences and obser va tions on the Beagle to conclude that all spe cies evolved to better en sure spe cies sur vival. He called it nat u ral selection. A shy and private man, Dar win ag o nized for years about reveal ing his theo ries to the public. Other natu ral ists finally convinced him to produce and publish Or i gin of Spe cies. With that book, Darwin’s discov er ies and the ory of evolu tion became the guiding light of biological sciences.

Fun Facts: Bats, with their ultra sonic echolocation, have evolved the most acute hear ing of any ter res trial ani mal. With it, bats can de tect in - sects the size of gnats and ob jects as fine as a hu man hair.

More to Ex plore

More to Explore Aydon, Cyril. Charles Darwin: The Natu ral ist Who Started a Scien tific Revo lu tion. New York: Carroll & Graf, 2003. Bowlby, John. Charles Dar win: A New Life. New York: W. W. Norton, 1998. Bowler, Pe ter. Charles Dar win: The Man and His Influ ence. New York: Cambridge Uni ver sity Press, 1998. Browne, Janet. Charles Dar win: Voy ag ing. London: Jona than Cape, 1998. Dennet, Dan iel. Darwin’s Danger ous Idea: Evolu tion and the Meanings of Life. New York: Simon & Schuster, 1996. Jenkins, Steve. Life on Earth: The Story of Evolu tion. New York: Houghton Mifflin, 2002. Mayr, Ernst. One Long Argu ment: Charles Darwin and the Gene sis of Modern Evolu - tion ary Thought. Cam bridge, MA: Harvard Univer sity Press, 1997. Woram, John. Charles Darwin Slept Here. Rockville Center, NY: Rockville Press, 2005. Atomic Light Sig na tures

Atomic Light Signa tures ATOMIC LIGHT SIGNATURES Year of Dis cov ery: 1859

What Is It? When heated, ev ery el ement ra di ates light at very specific and char ac ter is tic fre quen cies. Who Dis cov ered It? Gustav Kirchhoff and Robert Bun sen

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Twenty new ele ments (begin ning with the discov ery of cesium in 1860) were discov ered us ing one chem i cal anal y sis tech nique. That same tech nique al lows as tron o mers to de ter mine the chemi cal compo sition of stars millions of light years away. It also allowed phys icists to under stand our sun’s atomic fires that produce heat and light. That same technique allows other astron o mers to calcu late the ex act speed and motion of dis tant stars and gal axies. That one tech nique is spec trographic anal ysis, the discov ery of Kirchhoff and Bun sen, which ana lyzes the light emitted from burning chemi cals or from a distant star. They discov - ered that each ele ment emits light only at its own specific frequen cies. Spectrog ra phy provided the first proof that the ele ments of Earth are also found in other heavenly bodies—that Earth was not chemi cally unique in the universe. Their techniques are routinely used by scien - tists in vir tually ev ery field of science in the bi o logi cal, physi cal, and earth sciences.

How Was It Discov ered?

How Was It Discov ered? In 1814, German astron o mer Joseph Fraunhofer discov ered that the sun’s energy was not radi ated evenly in all frequen cies of the light spectrum, but rather was concen trated in spikes of en ergy at certain specific fre quencies. Some thought it inter est ing, none thought it impor tant. The idea lay dormant for 40 years. Gustav Kirchhoff (born in 1824) was an ener getic Polish physi cist who barely stood five feet in height. Through the mid-1850s he fo cused his re search on elec trical currents at the Univer sity of Breslau. In 1858, while helping another profes sor with a side project, Kirchhoff noted bright lines in the light spectrum produced by flames and recalled having read about a sim i lar oc cur rence in Fraun hofer’s ar ti cles. Upon in ves ti ga tion, Kirchhoff found that the bright spots (or spikes) in the light from his flame studies were at the exact same fre quency and wave lengths that Fraunhofer had detected in solar radiation. Kirchhoff pondered what this could mean and was struck by what turned out to be a brilliant insight: use a prism to sep arate any light beam he wanted to study into its constit u- ent parts (instead of peering at it through a sequence of colored glass filters as was the cus-

81 82 Atomic Light Signa tures

tom of the day). Kirchhoff believed that this would let him find spikes in the radi a tion coming from any burning gas. However, the scheme did not work well. The flame he used to heat his gasses was too bright and inter fered with his obser vations. Enter Robert Bunsen, the German-born chemist. In 1858, 47-year-old Bunsen had been devel op ing photochemistry—the study of light given off by burning ele ments. During this work, Bunsen had invented a new kind of burner in which air and gas were mixed prior to burning. This burner (which we still use and call a Bunsen burner) pro duced an extremely hot (over 2700°F) flame that produced very little light. Kirchhoff and Bunsen connected at the Univer sity of Heidel berg in 1859. Standing together, Kirchhoff barely reached Bunsen’s shoul der. The pair com bined Kirchhoff’s prism idea with Bun sen’s burner and spent six months to design and build the first spectro graph (a device to burn chemi cal samples and use a prism to sepa rate the light they produced into a spec trum of in di vid ual frequencies). They be gan to cat alog the spectral lines (specific fre quencies where each el ement ra di - ated its light energy) of each known el ement and dis covered that each and every ele ment always produced the same “signa ture” set of spectral lines that uniquely iden tified the pres ence of that element. Armed with this dis cov ery and their cat alog of each el ement’s char acter is tic spec tral lines, Kirchhoff and Bun sen made the first com plete chemi cal anal y sis of sea wa ter and of the sun—proving that hydro gen, helium, sodium, and half-a-dozen other trace ele ments common on Earth existed in the sun’s atmo sphere. This proved for the first time that Earth was not chemi cally unique in the universe. Kirchhoff and Bunsen had given science one of its most versa tile and flexi ble ana lyt i - cal tools and had dis covered a way to deter mine the compo sition of any star with the same accu racy as we deter mine sulfu ric acid, chlorine, or any other compound.

Fun Facts: Kirchhoff and Bunsen used their spectro graph to discover two new el e ments: ce sium in 1860 (they chose that name be cause ce sium means “sky blue,” the color of its spectro graph flame) and rubid ium in 1861. This ele ment has a bright red line in its spectro graph. Ru bid ium co - mes from the Latin word for red. More to Ex plore

More to Explore Clark, Donald. Ency clo pe dia of Great Inven tors and Discov er ies . London: Marshall Caven dish Books, 1991. Dia gram Group. Facts on File Chemis try Handbook . New York: Facts on File, 2000. Laidler, Keith. World of Phys i cal Chem is try. New York: Oxford Univer sity Press, 1995. Lomask, Milton. In ven tion and Tech nol ogy Great Lives. New York: Charles Scribner’s Sons, 1994. Philbin, Tom. The 100 Greatest Inven tions of All Time. New York: Cita del Press, 2003. Schwacz, Joe. The Man Behind the Burner: Robert Bunsen’s Discov er ies Changed the World of Chemis try in More Ways Than One. Chicago: Thomas Gale, 2005. Tuniz, R. J. Ac cel er a tor Mass Spec trom e try. New York: CRC Press, 1998. Electro mag netic Radi a tion/ Radio Waves

Elec tro mag netic Ra di a tion/Ra dio Waves ELECTROMAGNETIC RADIATION/RADIO WAVES Year of Dis cov ery: 1864

What Is It? All elec tric and mag netic en ergy waves are part of the one elec tro - mag netic spec trum and fol low sim ple math e mat i cal rules. Who Dis cov ered It? James Clerk Maxwell

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Throughout most of the nineteenth cen tury, peo ple thought that elec tric ity, magne - tism, and light were three sep a rate, un re lated things. Re search pro ceeded from that as sump - tion. Then Maxwell dis cov ered that they are all the same—forms of elec tro mag netic radi a tion. It was a startlingly grand dis covery, of ten called the greatest discov ery in phys ics in the nineteenth century. Maxwell did for electro mag netic radi a tion what Newton did for gravity—gave science math emat ical tools to understand and use that natural force. Maxwell uni fied magnetic and elec tri cal en ergy, cre ated the term elec tro mag netic ra- dia tion, and discov ered the four simple equations that govern the behav ior of electri cal and magnetic fields. While devel op ing these equa tions, Maxwell dis covered that light was part of the elec tro mag netic spec trum and pre dicted the ex is tence of ra dio waves, X-rays, and gamma rays.

How Was It Discov ered?

How Was It Discov ered? James Clerk was born in 1831 in Edin burgh, Scotland. The family later added the name Maxwell. James sailed easily through his univer sity schooling to earn top honors and a degree in mathe mat ics. He held vari ous profes sorships in math and phys ics thereafter. As a mathe ma ti cian, Maxwell explored the world—and the universe—through mathe - matic equations. His chose the rings of Saturn as the subject of his first major study. Maxwell used math emat ics to prove that these rings couldn’t be solid disks, nor could they consist of gas. His equations showed that they must consist of countless small, solid parti - cles. A century later, astron o mers proved him to be correct. Maxwell turned his at ten tion to gas ses and stud ied the math e mat i cal re la tion ships that gov erned the mo tion of rap idly moving gas parti cles. His re sults in this study completely re- vised science’s approach to studying the rela tion ship between heat (temper a ture) and gas motion. 83 84 Elec tro mag netic Ra di a tion/Ra dio Waves

In 1860 he turned his atten tion to early electri cal work by Michael Fara day. Fara day invented the elec tric motor by dis cover ing that a spin ning metal disk in a magnetic field created an elec tric cur rent and that a chang ing elec tric cur rent also changed a mag netic field and could cre ate physical motion. Maxwell de cided to math e mat i cally ex plore the re la tion ship be tween elec tric ity and mag ne tism and the “elec tri cal and mag netic lines of force” that Far a day had discovered. As Maxwell searched for math e mat i cal re la tion ships be tween var i ous as pects of elec tric - ity and magne tism, he devised exper i ments to test and confirm each of his results. By 1864 he had derived four sim ple equations that de scribed the behav ior of elec trical and mag netic fields and their in ter re lated na ture. Os cil lat ing (chang ing) elec tri cal fields (ones whose elec tri cal cur - rent rapidly shifted back and forth) pro duced magnetic fields and vice versa. The two types of en ergy were in te grally con nected. Maxwell re al ized that elec tric ity and magne tism were simply two ex pres sions of a single en ergy stream and named it elec tro mag - netic energy. When he first pub lished these equa tions and his dis cover ies in an 1864 arti cle, physi cists instantly recog nized the incred i ble value and meaning of Maxwell’s four equations. Maxwell contin ued to work with his set of equations and real ized that—as long as the elec tri cal source os cil lated at a high enough fre quency—the elec tro mag netic en ergy waves it created could and would fly through the open air—without conduct ing wires to travel along. This was the first pre diction of radio waves. He cal cu lated the speed at which these elec tro mag netic waves would travel and found that it matched the best calcu lations (at that time) of the speed of light. From this, Maxwell re al ized that light it self was just an other form of elec tro mag netic ra di a tion. Be cause elec tri - cally charged cur rents can os cil late at any fre quency, Maxwell re al ized that light was only a tiny part of a vast and contin u ous spectrum of electromagnetic radiation. Maxwell pre dicted that other forms of electro mag netic radi a tion along other parts of this spectrum would be found. As he predicted, X-rays were discov ered in 1896 by Wilhelm Roent gen. Eight years be fore that dis covery, Heinrich Hertz conducted exper i ments fol- lowing Maxwell’s equa tions to see if he could cause elec tromag netic radi a tion to fly through the air (trans mit through space in the form of waves of energy). He easily created and detected the world’s first ra dio waves, confirm ing Maxwell’s equations and predictions.

Fun Facts: Astron o mers have concluded that the most effi cient way of mak ing con tact with an in tel li gent civ i li za tion or bit ing an other star is to use ra dio waves. How ever, there are many nat u ral pro cesses in the uni verse that produce radio waves. If we could translate those natu rally produced radio waves into sound, they would sound like static we hear on a radio. In the search for in tel li gent life, as tron o mers use mod ern com put ers to dis tin guish be tween a “sig nal” (pos si ble mes sage) and the “noise” (static). More to Explore 85

More to Ex plore

More to Explore Camp bell, Lewis. The Life of James Clerk Maxwell. Do ver, DE: Ad a mant Me dia, 2001. Francis, C. W. James Clerk Maxwell: Phys i cist and Nat u ral Phi los o pher. New York: Scribner’s, 1994. Harmon, Pe ter. The Nat ural Phi loso phy of James Clerk Maxwell. New York: Cam - bridge Univer sity Press, 2001. Mahon, Basil. The Man Who Changed Every thing : The Life of James Clerk Maxwell. New York: John Wiley & Sons, 2004. Maxwell, James. Matter and Motion. Amherst, NY: Prome theus Books, 2002. Hered ity

HEREDITY HEREDITY Year of Dis cov ery: 1865

What Is It? The nat u ral sys tem that passes traits and char acter is tics from one gen er a tion to the next. Who Dis cov ered It? Gregor Mendel

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Gregor Mendel conducted the first seri ous study of hered ity. His findings, his methods, and his discov er ies laid the founda tion for the field of genet ics and the study of genes and hered ity. The discov er ies of genes, chromo somes, DNA, and the decod ing of the hu - man ge nome (completed in 2003) are all direct descendents of Mendel’s work. The medi cal breakthroughs in the fights to cure dozens of diseases are offshoots of the work begun by Gregor Mendel. Finally, Mendel’s discov ery, itself, provided great insights into the role of inher ited traits and into the ways those traits are passed form gener a tion to gen era tion.

How Was It Discov ered?

How Was It Discov ered? The wide fields and gar dens of the Austrian Monas tery of Bruun stretched up gently sloping hills surround ing the monas tery complex. Tucked into one corner of the monas - tery’s gar den com plex stood a small 120-foot-by-20-foot plot. This small garden lab o ratory was used by one of the monks, Fa ther Gregor Mendel, for his ex peri ments on hered ity; that is, on how indi vid ual traits are blended from an indi vid ual through succes sive gener a tions into a popu lation. In May 1865, he planted his sixth year of experimental pea plants. Eng lish sci en tist Charles Dar win ex plained evo lu tion but had n’t suc cess fully ad- dressed how charac ter is tics are passed down through the gener a tions, some to domi nate (appear) in every gen era tion—some to randomly pop up only every now and then. That was what Mendel wanted to study. Mendel crossed a strain of tall pea plants with one of short pea plants. He produced a row of all tall plants. And when he planted the seeds of those tall plants he got mostly tall with a few short plants. The short trait re turned in the second gener a tion. Simi larly, he cross bred yellow peas with green peas and got a gener a tion of all yel low peas. But in the next gener a tion he pro duced mostly yellow with a few green peas. But never a yel low-green. The green color trait re turned but the traits never mixed. The same happened when he cross bred smooth-skinned with wrinkled-skinned peas.

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Over six years of work, Mendel found the same pattern in every crossbreeding exper i - ment he tried. In the second gener a tion, one plant in four switched and showed the reces sive trait (the trait that hadn’t showed up at all in the first gen era tion). Al ways three to one. He knew that a plant inher ited one version of each trait (or gene) from father and mother plants. But what if, in each pairing of traits, one trait were always stronger (dom i- nant), and one always weaker (re ces sive)? Then, when the traits mixed, a first-gener ation plant would always show the domi nant one (all yellow, or all tall). But three to one . . . . That happened in the second gener a tion. Mendel real ized simple mathe mat i cal proba bil ity said there could be four possi ble combi na tions of traits in a sec - ond-gener a tion plant (ei ther dom inant or reces sive trait from either father or mother plant). In three of those combi na tions at least one domi nant trait would be present, and that would dic tate what the plant be came. In only one combi na tion (re ces sive trait from both parents) would there be nothing but recessive traits present. Three to one. Traits did not mix. They were inher ited from gener a tion to gener a tion and appear only when they are domi nant in an indi vid ual plant. Traits from countless ances tors flow into each of us, in sepa rate packages called “genes,” unblend ed for us to pass on even if a trait doesn’t “show” in our generation. It was not until 1900 that another scien tist—Dutch man Hugo de Vries—re alized the sci entific value of Mendel’s great gift to the world with his in sights on heredity.

Fun Facts: Gregor Mendel’s concept of hered ity required two parents. Dolly the sheep made scien tific history in 1997 when she was cre ated from the cells of a single adult sheep in a Scottish lab. She was cloned, an exact genetic dupli cate of her mother, with no contrib ut ing gene cells from a father.

More to Ex plore

More to Explore Bankston, John. Gregor Men del and the Dis covery of the Gene. Hockessin, DE: Mitch ell Lane, 2004. Bardoe, Cheryl. Gregor Mendel: The Friar Who Grew Peas. New York: Abrams Books for Young Readers, 2006. George, Wilma. Gregor Men del and Hered ity . Wayland, England: Howe Publish ers, 1995. Gribben, John. Men del in 90 Minutes. London: Consta ble Press, 1997. Ha ven, Kend all. Mar vels of Sci ence. Englewood, CO: Librar ies Unlim ited, 1995. Henig, Robin. The Monk in the Garden: The Lost and Found Genius of Gregor Men - del. New York: Houghton Mifflin, 2000. Yannuzzi, Della. Gregor Men del: Ge net ics Pi o neer. New York: Franklin Watts, 2004. Deep-Sea Life

DEEP-SEA LIFE DEEP-SEA LIFE Year of Dis cov ery: 1870

What Is It? Eter nally black, deep ocean wa ters are not life less deserts, but sup - port abundant life. Who Dis cov ered It? Charles Thomson

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Charles Thomson radi cally changed science’s view of deep oceans and of the require - ments for life in the oceans. There existed no light in the ocean depths, yet he discov ered abundant and varied life. He proved that life can exist without light. He even proved that plants can thrive in the lightless depths (though it took another century before scien tists fig- ured out how plants live without photosynthesis). Thomson’s discov ery extended known ocean life from the thin top layer of the oceans into the vast depths and provided the first scien tific study of the deep oceans. For his dis cov- eries, Thomson was knighted by Queen Victo ria in 1877.

How Was It Discov ered?

How Was It Discov ered? Charles Thomson was born in 1830 in the salt air of the Scottish coast. After college, he worked at vari ous univer sity research and teaching posi tions until, in 1867, he was appointed pro fes sor of bot any at the Royal College of Sci ence in Dublin, Ireland. Common wisdom at the time said that, since light only pen etrated the top 250 to 300 feet of the oceans, life only existed in that same narrow top layer where light could support the growth of ocean plants. The deep oceans were lifeless, lightless deserts. No one bothered to ques tion the logic of this be lief. Then, in early 1866, Michael Sars conducted some deep dredging oper a tions off the coast of Norway as part of a cable-lay ing project. He claimed that his dredge snared fish at depths of over 1,000 feet. Scien tists scoffed and said that his dredge must have caught the fish ei ther on the way down or on the way back up. He could n’t have caught them at a depth that far below the ocean’s “life zone” because nothing could live down there. However, the report caught Thomson’s imagi na tion. He began to wonder: What if living crea tures did lurk in the vast, dark depths of the ocean? Were ocean depths the lifeless desert every one imagined? Without ac tually going there, how could anyone really know? Con vinced that this ques tion was wor thy of se ri ous sci en tific in ves ti ga tion, Thomson persuaded the Royal Navy to grant him use of the HMS Light ning and HMS Por cu pine for

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summer dredging expe di tions for three consec u tive summers: 1868, 1869, and 1870. Dur- ing these voyages off the English and Scottish coasts, Thomson used deep sea nets and dredges to see what life he could find in wa ters over 2,000 feet deep. Most scien tists thought that he was wasting his time and the navy’s money and would make a fool of himself. Over those three brief summers, Thomson made over 370 deep-sea soundings. He dragged his nets and dredges through the oceans at depths of up to 4,000 feet (1,250 meters) and consis tently found the presence of life at all surveyed depths. His nets always snared a va ri ety of in ver te brates and fish. Thomson had discov ered that whole popu la tions of fish lived and thrived in the ocean depths where no light ever pene trated to spoil the total blackness. He also collected water samples from the deep, inky-black waters and found the constant presence of detri tus—dead plant life that fell through the water column to reach the depths without being eaten. Ma rine an imals also died and added to this rain of food to support creatures that lived in the depths. Thomson found all known marine inver te brate species living at these depths as well as many unknown fish species. He also dredged up bottom-dwell ing plants, proving that plants grew and thrived without sunlight. He re ported his startling dis cover ies in his 1873 book The Depths of the Sea—published just after Thomson set sail on the Chal lenger for an extended, five-year voyage to complete his 70,000 nauti cal miles of deep-sea research data collec tion that proved that deep-sea life ex isted in all of the world’s oceans.

Fun Facts: The largest giant squid ever studied was 36 feet long when it washed up dead on a South Ameri can beach. The circu lar suckers on its two long arms mea sured 2.2 inches across. Sperm whales have been caught with fresh scars from giant squid suckers measur ing over 22 inches across. That trans lates to a monster squid over 220 feet long! They’re out there, but no human has seen one since sailors talked of meeting giant sea mon sters hundreds of years ago.

More to Ex plore

More to Explore Collard, Sneed. The Deep-Sea Floor. Watertown, MA: Charlesbridge Publish ing, 2003. Gibbons, Gail. Explor ing the Deep Dark Sea. New York: Little, Brown, 1999. Hall, Michele. Se crets of the Ocean Realm. New York: Carroll &d Graf, 1997. Her ring, Pe ter. The Bi ology of the Deep Ocean. New York: Ox ford Uni versity Press, 2002. Ty ler, P. A. Eco sys tems of the Deep Ocean. Chevy Chase, MD: Elsevier Sci ence Pub - lish ing, 2003. Van Dover, Cindy. Deep-Ocean Journeys: Discov er ing New Life at the Bottom of the Sea. New York: Ad dison Wesley, 1997. Peri odic Chart of Ele ments

PERIODIC CHART OF ELEMENTS PERIODIC CHART OF ELEMENTS Year of Dis cov ery: 1880

What Is It? The first suc cess ful or ga niz ing sys tem for the chem i cal el e ments that compose Earth. Who Dis cov ered It? Dmitri Mendeleyev

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? When most people think of the chemi cal ele ments, they picture Mendeleyev’s Peri - odic Chart of the Ele ments. This orga ni za tional table has served as the one accepted orga - nizing system for the ele ments that make up our planet for 125 years. It is so impor tant that it is taught to every student in be ginning chemis try classes. It led to the discov ery of new elements and has been a corner stone of chemists’ under stand ing of the proper ties and rela - tionships of Earth’s ele ments. It has also helped in the design and conduct of chemi cal exper i ments and greatly sped the de velop ment of science’s under stand ing of the basic elements in the early twentieth century.

How Was It Discov ered?

How Was It Discov ered? By 1867, 33-year-old Dmitri Mendeleyev had landed a po sition as chem istry profes sor at St. Peters burg Univer sity—a re markable accom plish ment for the youngest of 14 chil dren of a Russian peas ant. With an untamed thicket of hair, a wild, trail ing beard, and dark, pene - trat ing eyes, Mendeleyev was called “that wild Rus sian” by other chemists in Europe. In 1868 he began work on a chemis try textbook for his students. The question he faced in begin ning the book was how to arrange and orga nize the growing list of 62 known ele ments so that his students could under stand their char acter is - tics. By this time, Mendeleyev had collected a hoard of data from his own work and—mostly—from the work of others, es pecially from the English chemists Newland and Meyers and French man de Chancourtois. Mendeleyev sorted the ele ments by atomic weight; by family re sem blance; by the way they did—or did not—combine with hydro gen, carbon, and oxy gen; by the kind of salts they formed; by whether an ele ment existed as a gas, liquid, or solid; by whether an ele ment is hard or soft; by whether an ele ment melts at a high or low temper a ture; and by the shape of the ele ment’s crystals. Nothing allowed him to make sense of all 62 known elements. Then Mendeleyev, a skilled piano player, real ized that the notes on a pi ano re peated at reg u lar inter vals. Ev ery eighth key was a “C.” He re al ized that in sea sons, in waves at the

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beach, even in trees, char acter is tics re peat over and over af ter a set period of time or dis - tance. Why shouldn’t the same thing hap pen with the elements? He wrote each el ement and its var i ous char acter is tics on cards and spread them across a ta - ble, arrang ing and re arrang ing the cards, search ing for repeat ing patterns. He quickly found that ev ery eighth el e ment shared many fam ily traits, or char ac ter is tics. That is, most of the time, every eighth el ement shared charac ter is tics with the oth ers in this family. But not al ways. Mendeleyev was again stuck. One day that summer, it struck him that it was possi ble that not all of Earth’s ele ments had been discov ered. His chart of the ele ments had to allow for miss ing elements. He returned to his stack of cards and arranged them into rows and columns so that the way that the ele ments in each column bonded with other ele ments was the same, and so that the phys i cal char ac ter is tics of the el e ments in each row were the same. All of the known ele ments fit perfectly into this two-dimen sional chart. However, he had to leave three holes in the chart that he claimed would be filled by three as-yet-undis - cov ered el e ments. Mendeleyev even de scribed what these “miss ing” el e ments would look like and act like based on the com mon traits of other ele ments in their row and col umn. All Europe laughed and said his predic tions were the crazy ramblings of a wild fortuneteller. Three years later the first of Mendeleyev’s “miss ing” el ements was dis cov ered in Ger - many. The scien tific commu nity thought it an inter est ing coin ci dence. Within eight years the other two had also been found. All three looked and behaved just as Mendeleyev had predicted. Scien tists around the world were amazed and called Mendeleev a genius who had unlocked the myster ies of the world of chemi cal ele ments. His discov ery has guided chemi cal re search ever since.

Fun Facts: Mendeleyev’s pe ri odic chart helped dis pel the an cient al che - mist’s myth of turning lead into gold. In 1980, Ameri can scien tist Glenn Seaborg used a power ful cyclo tron to re move pro tons and neutrons from several thousand atoms of lead (atomic num ber 82), changing it into gold (atomic num ber 79). No, he didn’t create instant wealth. The process is so ex pen sive that each atom of gold he cre ated cost as much as sev eral ounces of gold on the open market.

More to Ex plore

More to Explore Atkins, P. The Pe ri odic King dom. New York: Weidenfeld and Nicolson, 1999. ———. Peri odic Kingdom: A Journey into the Land of the Chemi cal Ele ment. New York: Basic Books, 1997. Gordon, Michael. A Well-Ordered Thing: Dmitri Mendeleev and the Shadow of the Pe ri odic Ta ble. Jack son, TN: Ba sic Books, 2004. Jensen, William, ed. Mendeleev on the Pe ri odic Law. New York: Do ver, 2005. Strathern, Paul. Mendeleyev’s Dream: The Quest for the El e ments. New York: St. Martin’s Press, 2001. Zannos, Susan. Dmitri Mendeleev and the Peri odic Table. Hockessin, DE: Mitchell Lane, 2004. Cell Divi sion

CELL DIVISI ON CELL DIVISI ON Year of Dis cov ery: 1882

What Is It? The process by which chro mosomes split so that cells can di vide to produce new cells. Who Dis cov ered It? Walther Flemming

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Chromo somes carry genes that hold the blueprints for building, oper at ing, and main- taining the cells of your body. Genet ics and hered ity re search could not advance un til these physi cal struc tures inside the nucleus of each cell had been discov ered and stud ied. Our basic under stand ing of biol ogy also depends, in part, on our knowledge of how cells divide, repli cat ing them selves countless times over the course of an organism’s life. Both of these key concepts were dis covered during one ex peri ment car ried out by Walther Flemming. His discov er ies form part of the ba sic founda tion of mod ern bio logi cal sci ences. Much of what we know today about cell divi sion (called mi to sis) orig i nated with Flemming’s discoveries.

How Was It Discov ered?

How Was It Discov ered? For most of the nineteenth century, studies of cells, cell functions, and cell structure through the mi cro scope were ham pered be cause cell walls and all of their in ter nal parts were translu cent to transpar ent. No matter how good the micro scope was, these inner structures were seen only as vague grey-on-grey shapes. It was diffi cult—if not im possi ble—to make out any detail. So scien tists stained the cells with dyes, hoping to make the cell parts more visi ble. However, all dyes killed the cells. But there was no other way and, hopefully, the dye would com bine with some intracellular struc tures and not with others so that a few would stand out and be easily studied through the micro scope. Most dyes, however, didn’t work. They smeared the whole cell with dark color and masked the very structures they were supposed to reveal. Walther Flemming was born in 1843 in Sachsenberg, Germany. He trained as a doctor and taught at univer si ties from 1873 (at the age of 30) until 1905 (age 62). He called himself an anato mist and special ized in the micro scopic study of cells.

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In 1879 Flemming found a new dye (a by-prod uct of coal tar) that com bined well with partic u lar, stringlike mate ri als inside the cell nucleus and did not stain most other cell parts. Finally, a dye ex isted that allowed him to fo cus his obser vations on one partic u lar structure within the cell’s nucleus. He named the mate rial stained by this dye chromatin (from the Greek word for color) and be gan a se ries of ex per i ments us ing sal a man der em bryos. Flemming cut tis sue-pa per thin slices of embry onic cells from fertil ized sala man der eggs and stained them with this dye. The dye, of course, killed the cells. This stopped all cell activ ity and cell divi sion. But it was a price Flemming had to pay in order to study these chromatin structures within the cell nucleus. Since the cells were dead before he could observe them, what Flemming saw through his micro scope was a series of “still” images of cells frozen in vari ous stages of division. Over time, and with enough samples to study, he was able to arrange these im ages in order to show the steps of the cell division process. As the process began, the chromatin collected into short, thread like objects (whose name Flemming changed from chromatin to chro mo somes from the Greek words meaning “colored bodies”). It was soon clear to Flemming that these threadlike chromo somes were a key feature of cell divi sion. Therefore, Flemming named the process mi to sis, from the Greek word for thread. The words chro mo somes and mi to sis are still used today. Flemming saw that the next step was for each indi vid ual chro mo some thread to break into two identi cal threads, doubling the number of chro mo somes. These two iden ti cal sets of chro mo somes then pulled apart, half going to one end of the cell, half going to the other. The cell itself then divided. Each of the two offspring cells was thus stocked with a complete set of chro mo somes that was identi cal to the original parent. Flemming had discov ered the process of cell divi sion and published his results in 1882. The real value of Flemming’s discov ery lay hidden for 18 years. Then, in 1900, Hugo deVries put Flemming’s discov ery together with Gregor Mendel’s discov er ies on hered ity and re alized that Flemming had discov ered how hered i tary traits were passed from parent to child and from cell to cell.

Fun Facts: Like all living species, humans grow from a single egg cell into com plex organ isms with tril lions of cells. Louise Brown, born July 25, 1978, in Oldham, England, was the first human test-tube baby. Her first cell divi sions took place not in her mother’s womb, but in a labo ra - tory test tube.

More to Ex plore

More to Explore Adler, Robert. Med i cal Firsts. New York: John Wiley & Sons, 2004. Alberts, Bruce. Mo lec u lar Bi ol ogy of the Cell. Abingdon, England: Taylor & Francis, 1999. Boorstin, Daniel. The Discover ers: A History of Man’s Search to Know His World and Him self. New York: Random House, 1997. 94 Cell Division

Enslow, Sharyn, ed. Dy nam ics of Cell Di vi sion. New York: Oxford Univer sity Press, 1998. Larison, L. L. The Center of Life: A Natu ral History of the Cell. New York: New York Times Book Co., 1997. Snedden, Robert. Cell Di vi sion and Ge net ics. Portsmouth, NH: Heinemann, 2002.

More to Explore X-Rays

X-Rays X-RAYS X-Rays Year of Dis covery: 1895

What Is It? High-frequency radi a tion that can pene trate through human flesh. Who Dis cov ered It? Wil helm Roentgen

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? If you have ever had an X-ray as part of a medi cal checkup, you owe thanks to Wil- helm Roentgen. Medi cal X-rays have been one of the most power ful, useful, and life-saving diag nos tic tools ever devel oped. X-rays were the first noninvasive technique devel oped to allow doc tors to see inside the body. X-rays led to the more modern MRI and CT technologies. Chemists have used X-rays to under stand and deci pher the structure of complex mole - cules (such as peni cil lin) and to better under stand the elec tromag netic spec trum. The discovery of X-rays earned Roentgen the 1901 Nobel Prize in physics.

How Was It Discov ered?

How Was It Discov ered? In 1895 Wilhelm Roent gen was just a 40-something ac ademic profes sor at the Univer - sity of Wurzburg, Ger many, do ing ho-hum research into the effects of passing electric ity through gas-filled bottles. In Novem ber of that year he began exper i ments in his home basement lab with a Crookes’ tube (a device that ampli fied an electri cal signal by passing it through a vacuum). On Novem ber 8, he happened to notice that a photo graphic plate that had been wrapped in black paper and tucked inside a leather case in the bottom drawer of his desk had myste ri ously been exposed and imprinted with the image of a key. The only key in the room was an over sized key for a garden gate he had tossed into the desk’s center drawer over a year ago. The image on his photo graphic plate was of that key. Even more strange, he found that the key in the center drawer lay along a straight line from his glass Crookes’ tube mounted on the wall to the pho tographic plate deep in the bottom drawer. But no visi ble rays emitted from the Crookes’ tube and surely no light could have pene trated through the desk and leather case to the photo graphic plate. What could have myste ri ously flown across the room and passed through wood, leather, and paper to expose the photo graphic plate? Whatever it was, it could not pass through the metal key—which was why a dark gray im age of the key was outlined on his photograph.

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Other scien tists the o rized that rays would be emitted from a Crookes’ tube and had named them cathode rays after the name of one of the metal plates inside the tube. Crookes thought these rays might come from another world. But no one had detected, measured, or studied these unknown rays. Roent gen sus pected that cathode rays had somehow exposed his film. Two weeks later he was able to prove the ex istence of these myste ri ous rays, which he named “X-rays” since “X” was used to repre sent the unknown. By this time, he had seen that X-rays could pass through wood, paper, cardboard, cement, cloth, and even most metals—but not lead. For this exper i ment, Roent gen coated a sheet of paper with bar ium platino-cy anide (a kind of flu o res cent salt) and hung it on the far wall of his lab. When he connected power to his Crookes’ tube, the fluo res cent sheet glowed a faint green. When he held an iron disk in front of the pa per, the paper turned back to black where the iron disk blocked the X-rays. Roentgen was shocked to also see the outline of every bone in his hand and arm in faint green outlines on the fluo res cent paper. When he moved a finger, the bones outlined in glowing green also moved. On seeing these first X-ray images, Roent gen’s wife shrieked in terror and thought that the rays were evil har bingers of death. Roentgen, however, began six weeks of inten sive study be fore releas ing his results on the na ture and po tential of X-rays. Within a month Wilhelm Roent gen’s X-rays were the talk of the world. Skep tics called them death rays that would de stroy the hu man race. Eager dream ers called them mir acle rays that could make the blind see again and could beam complex charts and dia grams straight into a student’s brain. Doc tors called X-rays the an swer to a prayer.

Fun Facts: The Z Machine at the Sandia Na tional Lab o ra to ries, New Mexico, can, very briefly, produce X-rays with a power output roughly equiva lent to 80 times that of all of the world’s elec tri cal gen er a tors.

More to Ex plore

More to Explore Aaseng, Na than. The In ven tors. Min ne ap o lis, MN: Lerner Pub li ca tions, 1998. Claxton, Keith. Wil helm Roent gen. London: Heron Books, 1994. Dibner, Bern. Wilhelm Conrad Röntgen and the Discov ery of X-Rays. New York: Franklin Watts, 1998. Esterer, Arnulf. Dis cov erer of X-Rays: Wil helm Roentgen. New York: J. Messner, 1997. Gar cia, Kimberly. Wil helm Roentgen and the Dis covery of X-Rays. Hockessin, DE: Mitch ell Lane, 2002. Nitske, Robert. The Life of Wilhelm Conrad Röntgen, Discov erer of the X-Ray. Tuc son: Uni ver sity of Ar i zona Press, 1996. Blood Types

Blood Types BLOOD TYPES Year of Dis cov ery: 1897

What Is It? Humans have differ ent types of blood that are not all compat i ble. Who Dis cov ered It? Karl Landsteiner

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Blood was blood—or so the world thought. Then Austrian physi cian Karl Landsteiner discov ered that there were four types of blood. Some could be safely mixed and some could not. That discov ery has saved millions of lives. The day that Karl Landsteiner’s results were published, blood transfu sions became a safe and risk-free part of sur gery. A patient’s chances of surviv ing surgi cal proce dures greatly increased. By making surgery safer, he made many new sur gi cal pro ce dures pos si ble and prac ti cal. Landsteiner’s discov ery also greatly ad vanced hu man under stand ing of blood structure and blood chemis try and paved the way for a num ber of key medi cal discov er ies in the early twen ti eth cen tury.

How Was It Discov ered?

How Was It Discov ered? Vienna, Austria, was a glamor ous city in 1897—as modern as any in the world. Dr. Karl Landsteiner worked in the Univer sity of Vienna hospi tal, where he conducted cause-of-death (post mor tem) med i cal ex am i na tions. One April day that year, Landsteiner exam ined four patients who had died during surgery. All died for the same reason: blood ag gluti na tion (clotting). Each pa tient had re ceived blood transfu sions and died when his or her own red blood cells clumped together with red blood cells in the blood they were given into thick clots. Landsteiner had seen this often during his thou sands of post mortem exam i na tions and wondered why it only happened with some patients. That evening, Landsteiner played pi ano for his wife and several friends. It was the one thing Karl felt he did well. Most who heard him thought he should give up medi cine for a brilliant career as a pia nist. In the middle of a famil iar piece, it suddenly occurred to Landsteiner that the answer had to be something in the patients’ blood. What if all blood was not the same, as every one sup posed? The next morning Landsteiner collected blood from 20 patients, wanting to see if he could pre dict which samples were safe to mix with each other.

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In long rows of test tubes, he mixed a few drops of each patient’s blood with a few drops of blood from every other patient. In his micro scope, he checked to see which red blood cells clumped together, and which did not. Be fore he had checked half the test tubes un der a micro scope, Karl was stunned to find that he could easily divide the blood samples into two distinct groups. Red blood cells from any member of one group agglu ti nated (stuck to) red blood cells from every member of the other group. But the cells never stuck to blood cells of other members from the same group. He named these groups “A” and “B.” Not all blood was compat i ble. Differ ent people’s blood was dif fer ent! He contin ued testing and found blood samples that didn’t agglu ti nate with ei ther type “A” or “B” red blood cells. Landsteiner re al ized that there must be a third group. Peo ple in this group could safely donate blood to anyone. He named this third blood group type “O.” Then he found one blood sample that agglu ti nated with both type A and type B blood. There ex isted a fourth type of blood that reacted to both A and B blood, just as type O blood re acted to nei ther. Karl named this fourth group type “AB.” Blood was not all the same. There were four dis tinct types. Safe transfu sions required a doctor to deter mine the blood types of both patient and donor. It seemed like such a simple, ob vious idea, and yet is one that has saved millions of lives.

Fun Facts: Humans have four blood types (A, B, AB, and O). Cats have the same number of possi ble blood types. Cows, however, have over 800!

More to Ex plore

More to Explore Adler, Robert. Med i cal Firsts. New York: John Wiley & Sons, 2004. Eibl, M., ed. Ep i sode Rec og ni tion Since Landsteiner’s Dis cov ery. New York: Springer, 2002. Ha ven, Kend all. Mar vels of Sci ence. Englewood, CO: Librar ies Unlim ited, 1995. Heidelberger, Mi chael. Karl Landsteiner: June 14, 1868–June 26, 1943. New York: Co lum bia Uni ver sity Press, 1995. Show ers, Paul. A Drop of Blood. New York: Crowell Publish ers, 1999. Speiser, Paul. Karl Landsteiner, the Discov erer of the Blood-Groups and a Pio neer in the Field of Immu nol ogy . Frank furt, Germany: Hollineck, 1994. Elec tron

Elec tron ELECTRON Year of Dis cov ery: 1897

What Is It? The first sub atomic par ti cle ever dis cov ered. Who Dis cov ered It? J. J. Thomson

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? At oms had never been seen. De fined as the smallest par ti cles pos si ble and the ba sic build ing blocks of all mat ter, they were invis i bly small—in the late nineteenth century still more theo reti cal than real. How could some one claim to have found something smaller? How could parti cles get any smaller? Thomson discov ered the elec tron and proved that it ex isted—with out ever being able to see or iso late one. Elec trons were the first sub atomic par ti cles to be dis cov ered, the first parti cle of matter identi fied that was smaller than an atom. This discov ery also finally pro - vided some phys ical proof of, and descrip tion of, the basic unit that carried elec tric ity. Thomson’s ex peri ments and discov ery be gan a new field of science—par ticle physics.

How Was It Discov ered?

How Was It Discov ered? He was born Joseph John Thomson in De cem ber, 1856, in Manches ter, England. By age 11 he had dropped his first names and used only his initials, J. J. Thomson began engi - neer ing studies at age 14 at Owens College and later brought a math and engi neer ing background to the study of phys ics. In 1884 he was appointed to chair Cambridge’s famed Caven dish phys ics lab. Thirteen years later and still at Cavendish, Thomson conducted the ex per i ment that dis cov ered the elec tron. Cath ode rays were dis covered by Ger man Julius Plucker in 1856. How ever, scien tists couldn’t agree on what cathode rays were. A great contro versy boiled: were they waves or were they par ti cles? Sci ence’s great est minds ar gued back and forth. In 1896 Thomson decided to design ex peri ments that would settle this dis pute. He built a cathode ray tube and fired its myste ri ous rays at a metal plate. The plate picked up a nega tive charge. This proved that cathode rays had to carry a nega tive charge. Next, he con - firmed with a flu o res cent-coated ruler that a mag netic field would de flect cathode rays. (Oth ers had con ducted this ex per i ment.) Thomson attached thin metal plates inside his cathode ray tube to a battery and showed that an electri cal field could also deflect cathode rays. (The spot that lit up on his fluo res cent ruler shifted when he connected the battery.)

99 100 Elec tron

Finally, Thomson built a new cathode ray tube with a thin slit through a metal plate. Cathode rays were channeled through this narrow slit. Beyond that metal plate he added a magnetic field to deflect cathode rays in one direc tion, followed by an electric field that would de flect them back in the other direc tion. Thomson knew the force these two fields created. Once he measured the amount of de- flec tion (change of di rec tion) each force cre ated in the stream of cath ode rays, he could cal - culate the mass of the parti cles in this cathode ray stream. That would finally solve the mys tery by iden ti fy ing the spe cific par ti cles. He ran his exper i ment and didn’t believe his re sults. The ratio of elec tric charge to parti cle mass was way too big, and that meant that the mass of these par ti cles had to be much smaller than any known par ticle. He re peated the exper i ment a hun dred times. He ripped apart and re built each piece of equip ment. The re sults were al ways the same. The mass of this par ti cle had to be less than 1/1000 of the mass of a proton (a hydro gen atom)—one thousand times smaller than the small est atom—sup pos edly the small est pos si ble par ti cle. Thomson had dis covered a new parti cle—the first subatomic parti cle. It took hundreds of demon stra tions and several detailed arti cles before anyone believed that his new parti cles ex isted. In 1891 Irish physi cist George Stoney had named the funda men tal unit (parti cle) of electric ity the “electron” without having any idea what that parti cle was like. Thomson decided to use Stoney’s name (elec tron) for his new par ti cle since it car ried elec tri cal cur rent. In 1898 a Frenchman named Bequerel found photo graphic proof of the exis tence of subatomic parti cles to con firm Thomson’s dis covery.

Fun Facts: If an elec tron weighed the same as a dime, a proton would weigh the same as a gal lon of milk

More to Ex plore

More to Explore Dahl, Per. Flash of the Cathode Rays: A History of J J Thomson’s Electron. Abingdon, England: Taylor & Francis, 1997. Da vis, E. J.J. Thomson and the Discov ery of the Elec tron. London: CRC, 1997. Ray leigh, D. The Life of Sir J.J. Thomson: Some time Master of Trin ity College, Cam- bridge. New Cas tle, DE: Dawsons of Pall Mall, 1996. Sherman, Josepha. J. J. Thomson & the Dis cov ery of Elec trons. Hockessin, DE: Mitch ell Lane, 2005. Thomp son, George. J. J. Thomson: Dis cov erer of the Elec tron. New York: An chor Books, 1998. ———. J.J. Thomson and the Cavendish Labo ratory in His Day. New York: Doubleday, 1996. Virus

Vi rus VIRUS Year of Dis cov ery: 1898

What Is It? The smallest, simplest living organ ism and causative agent for many human diseases, from sim ple colds to deadly yellow fe ver. Who Dis cov ered It? Dmitri Ivanovsky and Martinus Beijerinick

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Far smaller than cells and bac te ria, vi ruses are the small est life forms on Earth—so small they can only repro duce inside some host cell and do it by taking over control of that cell. Viruses are so small they easily slip through vir tually any filter or trap. Their discov ery answered many med ical questions at the be ginning of the twen tieth century and completed Pasteur’s germ theory. Viruses cause many of the most danger ous human diseases. Until they were dis covered, med ical sci ence had ground to a halt in its ad vance on curing these human illnesses. When Beijerinick discov ered viruses, he actu ally discov ered a new life form, one too small to be seen with any micro scope other than a mighty electron microscope.

How Was It Discov ered?

How Was It Discov ered? French sci en tist Louis Pas teur dis cov ered germs (mi cro scopic bac te ria) and claimed that germs caused dis ease and rot. How ever, he was never able to find a micro or gan ism (germs) that caused rabies, though he tried for over a decade before giving up in 1885. It left a shadow of doubt over his germ theory. Another disease for which no one could find an identi fi able causative agent was tobacco mosaic dis ease (so called be cause a mo saic pat tern forms on the leaves of in fected plants). In 1892 Russian bota nist Dmitri Ivanovsky decided to search for this myste ri ous agent. (It was safer to work with tobacco mosaic disease than with deadly rabies.) Ivanovsky mashed up infected leaves and passed the fluid through var ious paper and ceramic fil ters. These fil ters were sup posed to trap all or gan isms—even the tiniest bacteria. However, the fluid that strained through these sets of filters could still infect healthy tobacco plants with mosaic disease. That meant that Ivanovsky hadn’t trapped the causative agent in his fil ters. He tried dif ferent filter mate ri als, differ ent treatments, and baths for the leaves and mashed juice. His re sults were al ways the same. Whatever caused this dis ease, Ivanovsky couldn’t trap it in a filter.

101 102 Vi rus

Ivanovsky refused to believe that any living organ ism existed that was smaller than bac te ria and so con cluded that his fil ters were de fec tive and would not, in fact, catch small bacte ria. In disgust, he abandoned his project. In 1898 Dutch bota nist Martinus Beijerinick decided to try his luck at solving the mystery of tobacco mosaic disease. He repeated Ivanovsky’s exper i ment and got the same re - sult. However, Beijerinick was quite willing to conclude that this exper i ment proved that the causative agent was something new and unknown—some thing much smaller than bacteria. That was why it hadn’t been trapped in his filters. Beijerinick admit ted that he did not know what it was, but he claimed that his ex peri ment proved that it ex isted and that it was super-tiny. He named it a “vi rus,” the Latin word for poison. While this dis cov ery was in tel lec tu ally in ter est ing to some sci en tists, few cared about a dis ease unique to tobacco plants. The notion of viruses re ceived lit tle atten tion from the med i cal and sci en tific communities. In 1899 German scien tist Friedrich Loeffler conducted a simi lar test and concluded that the agent respon si ble for foot-and-mouth disease was too tiny to be bacte ria and so must be another virus. Two years later, in 1901, Ameri can army surgeon Walter Reed ex - hausted his attempts to discover the cause for yellow fever that had killed so many Ameri - can soldiers. Then he tested this mosquito-borne disease to see if whatever caused it was small enough to be a virus. It was. This discov ery con vinced the scien tific world that viruses—1/1000 the size of even a small bac terium—were the cause of many human ailments and had to be studied and treated sepa rately from bacte ria. Ivanovsky and Beijerinick discov ered viruses, but it took Walter Reed to make the medi cal and scien tific commu nity pay attention.

Fun Facts: What’s the most common dis ease-causing virus? The common group of rhinoviruses, of which there are at least 180 types. Rhinoviruses cause colds and are almost univer sal, affect ing every one except for those living in the frozen wastes of Antarctica.

More to Ex plore

More to Explore Fuffle, Cady. Vi ruses. New York: Gareth Stevens, 2003. Gallo, Robert. Virus Hunting: Aids, Cancer, and the Human Retrovirus: A Story of Sci en tific Dis cov ery. New York: Basic Books, 1997. Kanaly, Mi chael. Virus Clans: A Story of Evolu tion. New York: Penguin Books, 1999. Mahy, Brian, ed. Concepts in Virol ogy: From Ivanovsky to the Present. Abingdon, England: Taylor & Francis, 1996. van Iterson, G. Martinus Willem Beijerinck: His Life and Work. Wash ington, DC: Sci - ence Tech Publish ers, 1995. Mi to chon dria

Mi to chon dria MITOCHONDRIA Year of Dis cov ery: 1898

What Is It? All-impor tant parts of every cell that provide cell en ergy and also have their own sep a rate DNA. Who Dis cov ered It? Carl Benda

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Mito chon dria are tiny energy produc ers in every cell. One of many tiny structures floating in the cell’s cyto plasm (fluid) that are collec tively called organelles, mito chon dria are consid ered the most im portant of all cell parts—besides the nucleus. Amazingly, mito chon dria have their own sepa rate DNA. You depend on them. They depend on you. And yet they are sepa rate living organ isms that have proved invalu able in tracking human history and evolu tion as well as for under stand ing cell oper a tion. Their dis - covery in 1898 marked a great turn ing point for microbiology.

How Was It Discov ered?

How Was It Discov ered? English man Robert Hooke dis covered cells in 1665 when he turned his micro scope onto a thin sliver of cork. As micro scopes improved and grew in magni fi ca tion power, scientists struggled to iden tify cells in other plant and animal tissue. How ever, tech ni cal prob lems slowed their prog ress. More pow er ful mi cro scopes were increas ingly hard to focus and provided sharp focus on smaller and smaller areas. This was called “chro matic ab er ra tion.” In 1841 the achro matic mi cro scope was in vented and eased this problem. Tissue samples had to be dye-stained so that indi vid ual cells (and parts of cells) would show up under the micro scope. However, staining often damaged cells and masked the very cell parts it was in tended to reveal. In 1871 Camino Gogli devel oped a staining process he called “black re ac tion.” This pro cess fi nally of fered sci en tists a chance to see the cell in te - rior that lay beyond cell walls. In 1781 abbot Felice Fontant glimpsed the nucleus of a skin cell. Scotsman Robert Brown named it the “nucleus” and, while studying orchids, was the one who discov ered that the nucleus was an essen tial part of living cells. In 1891 Wilhelm Waldeyer discov ered nerve cells. By 1895 sev eral research ers had ac tually watched cells di vide through their micro - scopes and saw that a number of tiny structures (which they called organelles) existed inside each cell. 103 104 Mi to chon dria

One of these re searchers was Carl Benda, born in 1857 in southern Germany. Even as a youth, Benda had been fasci nated by the micro scopic world and was one of the first to call him self a mi cro bi ol o gist and to make a career out of studying the micro scopic world. Benda had been swept up in the excite ment of the effort to peer inside a living cell. By 1898 it was clear that the cell cy to plasm (the inter nal fluid part of a cell) was not a sim ple, homo ge neous fluid. Tiny struc tures floated in there doing no-one-knew-what. During an exper i ment in 1898, Benda was able to make out hundreds of tiny bodies in the cy toplasm through the membrane of a cell. Benda thought they must be tiny pillars that helped hold the shape of the cell. So he named them mi to chon dria, from the Greek words mean ing “threads of car ti lage.” Nei ther he nor other sci en tists at the time gave mi to chondria any sig nifi cance other than that they existed and were part of the inter nal structure of a cell. By 1910 scien tists were better able to glimpse through cell walls and watch living cells function. Many sci entists sus pected that mito chon dria pro vided en ergy to the cell. By 1920, scien tists had deter mined that mito chon dria were the power plants that supplied over 90 per cent of all cell energy needs. In 1963 it was discov ered that mito chon dria had their own DNA (called mDNA). This was a shatter ing discov ery and made mito chon dria one of the most impor tant parts of a living cell. It meant that we are really coop er at ing colo nies of micro scopic bugs. In some far-distant past, tiny mito chon dria or ganisms made a deal with bigger cells. They traded energy for protec tion. The mito chon dria moved inside, but kept their sepa rate DNA. That made these tiny sub struc tures unique among all ele ments of a living body and an important subject for ongoing research. But it all started with Benda’s discov ery—even though he had no idea of the ulti mate impor tance of what he discov ered.

Fun Facts: Mi to chon dria are called the “pow er house of the cells,” where all cell en ergy is produced. That in cludes the energy for you to blink your eyes, for your heart to beat, or for you to perform amazing tasks like com- pleting the an nual race up the 1,576 steps of the Empire State Building. The current record holder is Belinda Soszyn (Austra lia) in 1996, with a time of 12 minutes, 19 seconds. Imagine how much energy her mito - chondria had to produce!

More to Ex plore

More to Explore Chance, Britton. Energy-linked Functions of Mito chon dria . Washing ton, DC: Aca - demic Press, 1994. Daniell, Henry, ed. Mo lec u lar Bi ol ogy and Bio tech nol ogy of Plant Organelles: Chloroplasts and Mi to chon dria. New York: Springer-Verlag, 2005. Levings, Charles. Mo lec u lar Bi ol ogy of Plant Mi to chon dria. London: Kulwar Aca - demic Pub lish ers, 1995. Osawa, Syozo. Evolu tion of the Genetic Code. New York: Ox ford Uni versity Press, 1995. Scheffler, Immo. Mi to chon dria. Dover, DE: Wiley-Liss, 1999. Radio ac tiv ity

Ra dio ac tiv ity RADIOACTIVITY Year of Dis cov ery: 1901

What Is It? Atoms are not solid balls and the smallest possi ble parti cles of matter, but con tain a number of smaller parti cles within them. Who Dis cov ered It? Ma rie Cu rie

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Ma rie Cu rie’s dis cov ery of two nat u rally ra dio ac tive el e ments, po lo nium and ra dium, made headline news, but her real discov ery was that atoms were not small solid balls and that there must be even smaller parti cles inside them. This discov ery opened the door to all atomic and subatomic re search and even to the splitting of the atom. Cu rie car ried out her re search with ra dio ac tive el e ments be fore the dan gers of ra dio ac - tivity were under stood. She suffered from ill health (radi a tion sickness) for most of her adult life. Indeed, for many years after her death, her notebooks were still highly radioactive. Marie Cu rie’s stud ies rank as one of the great turn ing points of science. Physics after Curie was completely differ ent than before and focused on the undis cov ered subatomic world. She cracked open a door that pene trated inside the atom and has led to most of the great est ad vances of twen ti eth-cen tury physics.

How Was It Discov ered?

How Was It Discov ered? In 1896 Marie Cu rie de cided to com plete her doc toral disser tation in a totally new field: radi a tion. It was excit ing. It was something no one had ever seen or studied be fore. Scien tists knew that elec trically charged ra dia tion flooded the air around uranium, but not much else was known. Marie used a device her husband, profes sor Pierre Curie, invented to de tect elec tric charges around min eral sam ples. She named this process ra dioac tiv ity and con cluded that ra dio ac tiv ity was emit ted from in side a uranium atom. Since the Cu ries had had no money of their own to pay for her re search, and since the univer sity refused to fund a woman’s grad u ate-level physics research, Ma rie scrounged for free lab space. She found an abandoned shed that had been used by the Biol ogy Depart ment to hold ca davers. It was unbear ably hot in the summer and freezing cold in the winter, with a few wooden tables and chairs and a rusty old stove. In 1898 Marie was given a puzzling uranium mineral ore called pitchblende, which her tests showed gave off more ra dioac tive emis sions than ex pected from the amount of ura-

105 106 Ra dio ac tiv ity

nium it contained. She concluded that there must be another substance inside pitchblende that gave off the extra radiation. She be gan each test with 3.5 ounces of pitchblende. She planned to re move all of the known metals so that ulti mately all that would be left would be this new, highly active ele - ment. She ground the ore with mortar and pestle, passed it through a sieve, dissolved it in acid, boiled off the liq uid, fil tered it, distilled it, then electro lyzed it. Over the next six months Ma rie and her hus band, Pierre, chemi cally isolated and tested each of the 78 known chemi cal el ements to see if these mys te ri ous radio ac tive rays flowed from any other substance be sides ura nium. Most of their time was spent begging for tiny sam ples of the many el ements they could not afford to buy. Oddly, each time Ma rie removed more of the known ele ments, what was left of her pitchblende was always more radio ac tive than before. What should have taken weeks, dragged into long months because of their dis mal working condi tions. In March 1901, the pitchblende finally gave up its secrets. Marie had found not one, but two new ra dio ac tive el e ments: po lo nium (named af ter Ma rie’s na tive Po - land) and radium (so named because it was by far the most radio ac tive ele ment yet dis covered). Marie pro duced a tiny sample of pure ra dium salt. It weighed .0035 ounces—less than the weight of a potato chip—but it was a million times more radioactive than uranium! Because the dangers of radi a tion were not yet under stood, Ma rie and Pierre were plagued with health troubles. Aches and pains. Ulcer-cov ered hands. Contin u ous bouts of se ri ous ill nesses like pneu mo nia. Never-end ing ex haus tion. Fi nally, the ra di a tion Ma rie had stud ied all her life killed her in 1934.

Fun Facts: Female Nobel Prize laure ates ac counted for only 34 out of a total of 723 prizes awarded as of 2005. Marie Cu rie is not only the first woman to be awarded a No bel Prize, but also one of four per sons to have been awarded the No bel Prize twice.

More to Ex plore

More to Explore Boorse, Henry, and Lloyd Motz. The Atomic Sci en tist: A Bio graph i cal His tory. New York: John Wiley & Sons, 1989. Born, Max. Atomic Physics. New York: Do ver Pub li ca tions, 1979. Dunn, Andrew. Pi o neers of Sci ence, Ma rie Cu rie. New York: The Bookwright Press, 1991. Keller, Mollie. Ma rie Cu rie: An Im pact Bi og ra phy. New York: Franklin Watts, 1982. McGrayne, Sharon Bertsch. Nobel Prize Women in Science: Their Lives, Struggles, and Mo men tous Dis cov er ies. New York: Carol Publish ing Group, A Birch Lane Press Book, 1993. McKown, Robin. Ma rie Cu rie. New York: G.P. Putnam’s Sons, 1971. Parker, Steve. Sci ence Dis cov er ies: Ma rie Cu rie and Ra dium. New York: HarperCollins, 1992. Quinn, Susan. Marie Curie: A Life. New York: Simon & Schuster, 1996. Reid, Robert. Ma rie Cu rie. New York: Dutton, 1998. At mo spheric Lay ers

At mo spheric Lay ers ATMOSPHERIC LAYERS Year of Dis cov ery: 1902

What Is It? Earth’s atmo sphere has distinct layers of air, each with unique tem per a tures, den si ties, humidities, and other prop er ties. Who Dis cov ered It? Leon Philippe Teisserenc de Bort

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? What could be more basic to under stand ing planet Earth than to know what lies between the sur face and Earth’s cen ter, or be tween the sur face and outer space? Yet the twentieth century dawned with science having virtu ally no con cept of what the atmo sphere was like more than two miles above the earth’s surface. Teisserenc de Bort was the first to ex pand science’s knowledge into the upper reaches of Earth’s atmo sphere. His discov ery provided the first accu rate image of our atmo sphere and formed the ba sis for our un der stand ing of me te o ro log i cal phe nom ena (storms, winds, clouds, etc.). Teisserenc de Bort was also the first to take scien tific instru ments into the upper atmosphere.

How Was It Discov ered?

How Was It Discov ered? Born in Paris in 1855, Leon Philippe Teisserenc de Bort was ap pointed the chief of the Admin is tra tive Center of National Mete o rol ogy in Paris at the age of 30. There he was frustrated be cause he believed that science’s inabil ity to under stand and pre dict weather stemmed from lack of knowledge about the atmo sphere more than three or four ki lome ters above the surface. Cer tainly, manned bal loon flights (both hot air and gas filled) had carried in struments into the atmo sphere. But these flights never ven tured above four or five kilo me ters in alti - tude. There was n’t enough oxy gen up there for people to breathe. In 1895 Teisserenc de Bort quit his job to devote full time to devel op ing unmanned, high-al titude gas bal loons at his Versailles villa (outside of Paris). Over the next five years, Teisserenc de Bort designed an instru ment package in a wicker basket that his balloons would carry aloft. Ba sic thermom eters and ba rom eters were con nected to re cording de vices so that he would have writ ten re cords of upper atmo spheric con ditions once the balloon returned to Earth. He also designed a re lease sys tem and para chute to deploy af ter the bas ket re leased from the rising balloon to bring his instru ment package gently back down.

107 108 At mo spheric Lay ers

Teisserenc de Bort found that tracking the basket and parachute were more diffi cult than he first thought, even when he used a telescope. Each launch involved a mad scramble across the country side to keep the descend ing package in sight. Even so, a few were never found, some sunk in rivers or lakes, and some were smashed when the parachutes failed. Still, Teisserenc de Bort per sisted—and was amazed at what he dis cov ered. At mo - spheric tem per a ture de creased steadily at a con stant rate of 6.5°C per ki lo meter of al ti tude (19°F per mile). This de crease was expected. However, at an alti tude of around 11 km (7 miles, or about 37,000 feet) the temper a - ture stopped decreas ing at all. It remained level at around -53°C up to over 48,000 feet (as high as Teisserenc de Bort’s bal loons would fly). At first Teisserenc de Bort didn’t believe that the temper a ture could possi bly stop de- creasing. He suspected that the instru ments rose to a height where solar heating warmed the ther mom e ter and com pen sated for con tin ued at mo spheric tem per a ture decrease. He be gan to launch at night. It was harder to track the para chute’s de scent, but it prevented any possi bil ity of so lar heating. Even at night, his results were the same. The tem per- ature above 11 km remained constant. Af ter 234 tests, Teisserenc de Bort fi nally con cluded that his mea sure ments were ac cu - rate and that there were two, sepa rate layers to the at mo sphere. Near the sur face lay an 11-km-thick lower layer where temper a ture changes created currents, winds, clouds, and weather. Above that was a re gion where con stant temper a ture al lowed air to set tle into quiet, undisturbed layers He named the lower layer the tro po sphere, from the Greek words meaning “sphere of change,” and the upper layer the strato sphere, from the Greek words meaning “sphere of lay ers.” Teisserenc de Bort’s discov ery is still the basis of our under stand ing of the atmo sphere.

Fun Facts: Scien tists now know that the at mosphere has many layers, but the tropo sphere is the layer where all of Earth’s weather oc curs.

More to Ex plore

More to Explore Emanuel, Kerry. At mo spheric Con vec tion. New York: Oxford Univer sity Press, 1997. Hewitt, C. N., ed. Hand book of At mo spheric Sci ence: Prin ci ples and Ap pli ca tions. Boston: Blackwell Publish ers, 2003. Jones, Phil. His tory and Climate. London: Kluwer Aca demic Press, 2001. Parker, Sybil, ed. McGraw-Hill En cy clo pe dia of Ocean and At mo spheric Sci ences. New York: McGraw-Hill, 1997. Stull, Ron ald. In tro duc tion to Bound ary Layer Me te o rol ogy. London: Kluwer Aca - demic Press, 1998. Wallace, John. At mo spheric Sci ence, First Edi tion: An In tro duc tory Sur vey. New York: Aca demic Press, 1997. Hor mones

Hor mones HORMONES Year of Dis cov ery: 1902

What Is It? Chem i cal mes sen gers that trig ger ac tion in var i ous or gans within the body. Who Dis cov ered It? Wil liam Bayliss and Ernst Star ling

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? At the dawn of the twenti eth century, sci entists thought that all con trol sig nals in the human body were sent electri cally along nerve fibers. Then Bayliss and Starling discov ery that chem i cal mes sengers (called hor mones) as well as electric signals trigger body or gans to function. This startling dis covery started a whole new field of medi cal sci ence: endo cri - nology. It rev o lution ized physi ol ogy and has been called one of the greatest discov er ies of all time related to the human body. Once dis cov ered and com mer cially pro duced, these hor mones were hailed as mir a cle drugs when made available in the market place. Adrena lin (the first hormone to be dis covered) was the first “block buster” drug of the twenti eth century. Other hor mones followed close behind.

How Was It Discov ered?

How Was It Discov ered? Bayliss and Starling get credit for discov er ing hormones. However, we must give some credit to those who, several years be fore, actu ally discov ered the first hor mone—even though they did not real ize the true sig nifi cance of their discovery. Dur ing a long se ries of an i mal ex per i ments in 1894, Brit ish phys i ol o gist Ed ward Al- bert Sharpey-Schafer showed that fluid extracted from the adre nal gland would raise blood pres sure if injected into an ani mal’s blood stream. He thought it inter est ing, but did not see any practi cal value to his find. In 1898 Ameri can pharma col o gist John Abel recog nized the medi cal value of this substance and studied its ori gin and chemis try. He isolated the key chemi cal in this fluid and named it epi neph rine (from the Greek words meaning “above the kidney,” since that’s where the adrenal gland is housed). Two years later, Jap a nese en tre pre neur and chemist Jokichi Takamine set up a lab in New York to create a synthetic ver sion of epineph rine in pure crystal line form that could be commer cially produced. In 1901 he succeeded, and called it adren a line be cause the nat u ral chem i cal came from the ad re nal gland. While Takamine re al ized the com mer cial value of his creation (and quickly patented the name and manu fac tur ing process), he did not take

109 110 Hor mones

note of the bio log i cal signif i cance of finding a chemi cal substance that traveled through the bloodstream to deliver an activation message to an organ. In 1902 two pro fes sors and med ical researches at Univer sity College of London began a study of diges tive juices. One was 40-year-old William Bayliss. His partner was his 34-year-old brother-in-law, Ernst Starling. Med i cal sci en tists knew that the pan creas be gan to se crete diges tive juice as soon as the food con tent in the stomach first entered the small intes tine. But how did the pan creas know that it should begin to produce juice at that moment? All as sumed an electric signal was some how sent through nerve cells. Bayliss and Starling decided to test this theory. They cut the nerves lead ing to the pancreas of a lab o ratory dog. Yet the pancreas still performed on cue. Upon close ex ami na tion, they found that the lin ing of the dog’s small intes tine secreted a liquid substance as soon as stomach acid reached it. This fluid (which they named secretin) traveled through the bloodstream to the pancreas and signaled the pancreas to leap into action. Un like Takamine, Bayliss and Star ling in stantly real ized that this was the first doc u - mented case of a sig nal be ing sent chem i cally through the body instead of elec tri cally along nerve fibers. They announced their findings, to the delight and wonder of the scien tific community. Bayliss suspected that many more such chemi cal messen gers existed and would be found. As soon as he read a report on Takamine’s work, Bayliss real ized that Takamine had discov ered another in this group of chemi cal mes sengers when he isolated adrenalin. In 1905 Starling coined the name hor mones for this growing group of chemi cal mes- sengers, from the Greek words meaning “to arouse to ac tivity.” The third hormone to be discov ered was cor ti sone, in 1935, by Ameri can biochem ist Edward Calvin. Now, almost 30 hormones have been discov ered that speed signals through your body, and their impor tance can hardly be overstated.

Fun Facts: Robert Earl Hughes, the world’s largest man, weighed 484 kg (1,067 lb.) at his death in 1958. Years after his death, scien tists dis covered that he had too little of the hormone thy roxin in his system. Without this vi tal hor mone, his body couldn’t burn the food he ate, and so his body contin u ally stored it as fat.

More to Ex plore

More to Explore Bliss, Michael. Dis cov ery of In su lin. Chicago: Univer sity of Chicago Press, 1994. Fox, Ruth. Mile stones in Med i cine. New York: Random House, 1995. Frayn, Keith. Met a bolic Reg u la tion: A Hu man Per spec tive. Boston: Blackwell Pub- lish ers, 2003. Henderson, John. A Life of Ernest Starling. New York: Oxford Univer sity Press, 2004. Maleskey, Gale. Hor mone Con nec tion. New York: Rodale Press, 2001. E = mc2 2 E = mc 2 E = mc Year of Dis cov ery: 1905

What Is It? The first estab lished rela tion ship be tween matter and energy. Who Dis cov ered It? Albert Ein stein

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? For all of his tory, mat ter was mat ter and en ergy was en ergy. The two were sep arate, un re lated con cepts. Then Ein stein es tab lished the re la tion ship be tween mat ter and en ergy by creat ing the most famous equation in the history of human kind, E = mc2. (The sec ond most famous is the Pythag o rean Theo rem for a right tri angle, A2 = B2 + C2.) Einstein’s equation for the first time defined a quanti fied rela tion ship between matter and energy. It meant that these two aspects of the universe that had always been thought of as sep a rate were re ally in ter change able. This one equation altered the direc tion of physics research, made Michelson’s calcu la - tion of the speed of light (1928) criti cal, and led directly to the nuclear bomb and nuclear energy development.

How Was It Discov ered?

How Was It Discov ered? In 1903, 24-year-old Albert Einstein landed a job as a patent clerk for the Swiss patent office. His whole job was to check the techni cal correct ness of patent submis sions. Though he had al ways dreamed of, and aimed for, a ca reer in sci ence, he had ut terly failed to gain an entry into that world. He had failed high school and was barred from teaching. He had married his high school girlfriend. He was a low-level bureau crat scraping by in Berne, Swit zer land, and it seemed that that was all he would ever be. Though he had been shunned in his formal edu ca tion, Einstein was still a passion ate ama teur mathe ma ti cian and phys i cist. He spent virtu ally all of his free time mulling over the great mys teries and problems facing physi cists of the day. Einstein worked best through what he called mind ex peri ments. He searched for vivid mental images that would shed new light on, and provide a new perspec tive on, complex physics problems. Then he applied the mathe mat ics he knew so well to explain the images and to under stand their physics implications. By 1904 Einstein was at tempting to extend the exist ing physics of the day by focus ing on the rela tion ships between light, space, and time. He was able to show that light exists as both waves and as parti cles. (A parti cle, or quanta, of light we call a photon.)

111 112 E = mc2

This work led to Ein stein’s rev o lu tion ary con cept of rel a tiv ity. From the math e mat ics that described this concept, he came to several startling conclu sions. Time was as rubbery as space. It slowed down as an object sped up. Objects increase in mass as they approach nearer to light speed. Ein stein’s theory of rela tiv ity es tablished a direct link be tween space and time and showed that they both warp around heavy objects (like stars). Their measure - ment is only pos sible in a relative, not an absolute, sense. From this the o ret i cal foun da tion, Ein stein con tin ued his math e mat i cal de vel op ment and showed that, as an object approaches the speed of light, its length de creases, its mass increases, and time slows down. (This con cept was later confirmed with pre ci sion clocks car - ried on high-speed jet airplanes.) If matter changed as it sped up, then matter and energy had to be somehow related to each other. Einstein real ized that his the ory of rela tiv ity showed that matter has to be a highly concen trated form of energy. He sus pected that he could deduce a mathe mat ical rela - tionship between the two. Ein stein re al ized that this rev o lu tion ary con cept con tra dicted the famed and completely ac cepted concepts of conser vation of mass (Lavoisier, 1789) and conser vation of energy (Hemholtz, 1847). Einstein was saying that these two giants of science were both wrong and that neither en ergy nor matter were inde pend ently con served. How ever, combined, the total en ergy in this en ergy-matter system had to still be conserved. Einstein viewed the energy-mat ter equation he de rived (E = mc2) like frost ing on the cake of his rela tiv ity theory. He submit ted an arti cle on it almost as an after thought to his theory of rela tiv ity, as a sequel to it. To Einstein, this equation was only of inter est as a phys ics and sci ence concern, as a way to view the the o ret i cal in ter change be tween mass and energy. He did not think it was particularly important. Others, however, quickly real ized the impli ca tions of Einstein’s equation for weapons design and for nuclear energy produc tion. “The world,” said Aldous Huxley after review ing Einstein’s physics, “is not only queerer than we imagine, it is queerer than we can imagine.”

Fun Facts: Einstein’s famous equation tells us exactly how much energy exists in any given ob ject (or mass). How ever, only one reac tion re leases all of this energy: a matter–an ti matter colli sion, the only perfect conver - sion of matter into energy in our universe.

More to Ex plore

More to Explore Bartusiak, Mar cia. Einstein’s Unfin ished Symphony: Listen ing to the Sounds of Space-Time. Wash ington, DC: Joseph Henry Press, 2000. Bernstein, Jeremy. Ein stein. New York: Penguin, 1995. Brian, Denis. Ein stein: A Life. New York: John Wiley & Sons, 1996. Calaprice, Al ice. The Quot able Ein stein. Princeton, NJ: Princeton Univer sity Press, 1996. Folsing, Albrecht. Al bert Ein stein: A Bi og ra phy. New York: Viking, 1997. Gold smith, Don ald. The Ul ti mate Ein stein. New York: By ron Press, 1997. More to Explore 113

Goldsmith, Maurice, ed. Einstein: the First Hundred Years. New York: Pergamon Press, 1996. Overbye, Den nis. Ein stein in Love: A Scien tific Ro mance. New York: Viking, 2000. Parker, Barry. Einstein’s Dream: The Search for a Uni fied Theory of the Universe . New York: Plenum, 2000. Whitrow, G., ed. Einstein: The Man and His Achievements . New York: Dover Publi - ca tions, 1997. Rela tiv ity

Rel a tiv ity RELATIVITY Year of Dis cov ery: 1905

What Is It? Einstein’s theory that space and time merge to form the fabric of the universe that is warped and molded by grav ity. Who Dis cov ered It? Albert Ein stein

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Albert Einstein is one of only three or four scien tists in his tory who have changed the funda men tal ways in which humans view the universe. Einstein’s theory of rela tiv ity changed human kind’s core assump tions concern ing the nature of the universe and of Earth’s and of humans’ place in it. The twenti eth century’s devel op ments in technol ogy, science, and math owe their founda tion to this unas sum ing scien tist in a deep and fun damen tal way. He has touched our lives proba bly more than any other scien tist in history. But for the first 26 years of his life, no one thought he had any chance of enter ing the world of science at all.

How Was It Discov ered?

How Was It Discov ered? Raised in Munich, Germany, Albert Einstein showed no early signs of genius. He was described as a dull child who didn’t play well with other children. Grammar school teachers called him irksome and dis ruptive. At 16 he was expelled from school. Albert’s fa ther en- couraged him to ap ply to the Polytech nic Insti tute in Zurich, Switzer land, and learn a trade to help support the family. But Al bert failed the en trance exam. A school ad min is tra tor was, how ever, impressed with Albert’s math abili ties and arranged for him to complete high school in nearby Aarua, Switzer land. At 17, Albert trans ferred to Zurich. There he showed promise in math and science, but piled up far too many disci pline reports. He was free with his opinions whether they were offen sive or not. His teachers gave him bad reports. One called him “a lazy dog.” Einstein hoped to teach after gradu a tion but his grades weren’t good enough. He dropped out of science in disgust and supported himself with odd jobs. In 1902 he landed a job as a clerk in the Swiss Pat ent Of fice, as signed to check the tech ni cal cor rect ness of pat - ent appli cations. It appeared that all doors leading to a sci ence ca reer had been firmly closed.

114 More to Explore 115

It was while riding on a Berne, Switzer land, trolley car in the spring of 1904 that the im age first flashed across Al bert Ein stein’s mind. It was an im age of a man in an el e va tor that was falling from a great height. Ein stein real ized imme di ately that the image of this “thought ex peri ment” could bring focus to a problem that had been plaguing him (and all of science) for years. Einstein real ized that the man in the ele va tor would not know he was fall ing because, rela tive to his surround ings (the el eva tor), he was n’t falling. The man—like us—would not be able to detect that he (and his ele va tor) were caught in, and being pulled by, a gravi ta - tional field. If a hor i zon tal light beam entered the side of the ele va tor, it would strike the far wall higher up because the ele va tor would have dropped while the light beam crossed. To the man, it would appear that the light beam bent upwards. From our perspec tive (rel a tive to us), gravi ta tional fields bend light. Light not only could be, but routinely was, bent by the gravitational fields of stars and planets. It was a revo lution ary con cept, worthy of one of the world’s greatest sci entific minds. Einstein regu larly used these imag ina tive “thought exper i ments” to shed light on com plex questions of general princi ples. It was a new and unique way to ap proach the study of physics and led Einstein to write a series of four pa pers, which he submit ted to a sci ence journal in 1905. One of those four papers presented the special theory of rela tiv ity (rela tiv ity princi - ples applied to bodies either moving at a steady veloc ity or at rest). Impressed, the journal published all four papers in a single is sue. Another presented Einstein’s relation between matter and energy. The papers from this “ama teur” mathe ma ti cian had a deep, instant, and profound effect in the sci en tific commu nity. One was ac cepted as a doc toral the sis by Zu rich Uni ver - sity, which granted Einstein a Ph.D. Virtu ally all phys i cists shifted their studies to focus on Ein stein’s theo ries. In 1916, with war raging across Europe, Einstein published his general theory of rela - tivity, which described rela tiv ity theory applied to objects moving in more complex ways with non lin ear ac cel er a tion. The world applauded.

Fun Facts: We know that the look and sound of moving objects appear and sound differ ent depend ing on whether the receiver is station ary or moving. Special rel ativ ity is based on the mind-boggling concept that, no matter how fast you travel, the speed of light appears to remain the same!

More to Ex plore

More to Explore Bartusiak, Mar cia. Einstein’s Unfin ished Symphony: Listen ing to the Sounds of Space-Time. Wash ington, DC: Joseph Henry Press, 2000. Bernstein, Jeremy. Ein stein. New York,:Penguin, 1995. Brian, Denis. Ein stein: A Life. New York: John Wiley & Sons, 1996. Calaprice, Al ice. The Quot able Ein stein. Princeton, NJ: Princeton Univer sity Press, 1996. Folsing, Albrecht. Al bert Ein stein: A Bi og ra phy. New York: Viking, 1997. Gold smith, Don ald. The Ul ti mate Ein stein. New York: By ron Press, 1997. 116 Rel a tiv ity

Goldsmith, Maurice, ed. Einstein: The First Hundred Years. New York: Pergamon Press, 1996. Overbye, Den nis. Ein stein in Love: A Scien tific Ro mance. New York: Viking, 2000. Parker, Barry. Einstein’s Dream: The Search for a Uni fied Theory of the Universe . New York: Plenum, 2000. Whitrow, G., ed. Einstein: The Man and His Achievements . New York: Dover Publi - ca tions, 1997. Vita mins

Vi ta mins VITAMINS Year of Dis cov ery: 1906

What Is It? Trace di etary chemi cal com pounds that are es sen tial to life and health. Who Dis cov ered It? Christiaan Eijkman and Fredrick Hopkins

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? We la bel foods by their vita min con tent. We spend billions of dollars every year buying vi ta min sup ple ments. Vi ta mins are es sen tial to life and health. Yet any aware ness of vita mins—even the very notion of vita mins—is only 100 years old. It had not occurred to anyone to search for trace ele ments in food that human bodies needed. They had only con- sidered mea suring the amount of food and the cal o ries in it. The dis cov ery of vi ta mins rev o lu tion ized nu tri tional sci ence and the pub lic’s awareness of health, diet, and nutri tion. It radi cally changed bio logi cal sci ence and the study of how the hu man body functions.

How Was It Discov ered?

How Was It Discov ered? During the early 1890s, the disease beriberi wreaked havoc on the Dutch East India Com pany’s op er a tions in In dia. Since Pas teur had dis cov ered germs, sci en tists as sumed that all diseases were caused by germs. Yet Company doctors could find no germ for beriberi. In 1896, 35-year-old Dutch physi cian Christiaan Eijkman traveled to India to try his luck at the inves ti ga tion. Shortly after he arrived, a massive outbreak of beriberi swept through the flock of chick ens at the re search fa cil ity used for bac te ri o log i cal research. Eijkman began fran tic research on the diseased flock when, just as suddenly, the dis - ease vanished. Eijkman was baf fled until he inter viewed the cook who fed the chick ens and found that, just before and during the outbreak, he had switched the chickens’ feed to white rice intended for human con sumption. When company offi cials had yelled at him for feeding expen sive polished (white) rice to chickens, the cook had switched back to normal chicken feed using brown rice. He found that he could cause beriberi at will by switching chicken feed to white (polished) rice and cure it by switching back. He ex amined local jail diets and found that where prison ers were fed a diet of brown rice, no beri beri oc curred. In jails that used white rice, beriberi out breaks were common.

117 118 Vi ta mins

Eijkman believed that something in brown rice cured beriberi and wrote a report claiming victory over the dis ease. He never consid ered looked at it the other way: that beriberi was caused by the ab sence of something that was present in brown rice. Fred er ick Hopkins was an Amer i can med i cal re searcher who was born as the Civil War broke out in 1861. In 1900 he iso lated an amino acid. (Other research ers had dis covered two others before him but had not inves ti gated their impor tance.) Hopkins called his amino acid tryptophan. From a re view of other research, he found that farm ani mals could not be kept alive if their only sources of protein were things that included no tryptophan. No matter how much protein they got, ani mals seemed to require trace amounts of tryptophan to survive. By 1906 chemists had isolated at least 13 amino acids. Each was an essen tial building block of pro tein mole cules. It occurred to Hopkins that these partic u lar amino acids (which were com monly found in foods) were es sential to life. Not for the pro tein and cal o ries they provided; those could come from anywhere. There was something else these amino acids provided that was es sential to life—even if only sup plied in trace amounts. Hopkins reviewed Eijkman’s work and dis covered that it was an amino acid in brown rice feed that prevented beriberi. He found that it was not just fruit that prevented scurvy (as first discov ered by Lind in 1747). It was a partic u lar amino acid in fruit. Hopkins decided that diseases such as beriberi, scurvy, pella gra, and rickets were not caused by a thing (a germ) but by the ab sence (or defi ciency) of something. Hopkins believed that these dis eases were caused by a di etary defi ciency of amine groups of mole cules (combi na tions of nitro gen and hydro gen atoms found in amino acids). He named this group of ac ids by combin ing the Latin word for life with “amines” and got vitamines. A few years later, re search ers dis cov ered that not all es sen tial vi ta mins con tained amines. They dropped the “e” to form the word vi ta min—which we still use today. How- ever, research in nutri tion has ever since been shaped by Hopkins’s discov ery of vitamins.

Fun Facts: Think all sweets are bad for you? Hershey’s Sugar Free Choco late Syrup has 10 percent vita min E per serving.

More to Ex plore

More to Explore Apple, Rima. Vitamania: Vi ta mins in Amer i can Cul ture. New Brunswick, NJ: Rutgers Uni ver sity Press, 1996. Becker, Stan ley. Butter Makes Them Grow: An Epi sode in the Discov ery of Vita mins . Hart ford: Con nect i cut Ag ri cul tural Ex per i ment Station, 1997. Car pen ter, Ken neth. For got ten Myster ies in the Early History of Vi ta min D. Wash ington, DC: Amer i can In sti tute of Nu tri tion, 2005. Rucker, Robert. Hand book of Vi ta mins. New York: CRC Publish ers, 2001. Yan, Kun. Stories of the Discov ery of Vita mins: The Young Doctors Collec tion. Bloomington, IN: Authorhouse, 2005. Ra dio ac tive Dat ing

Ra dio ac tive Dat ing RADIOACTIVE DATING Year of Dis cov ery: 1907

What Is It? The use of ra dio active decay ing el ements to cal cu late the age of rocks. Who Dis cov ered It? Bertram Boltwood

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Nothing is more ba sic than know ing your age—or the age of your house, or of a tree in your yard. For science, the same is true for Earth and for the rocks that make up Earth’s crust. Scien tists had been es timat ing Earth’s age for thou sands of years. However, these were lit tle more than guesses. Boltwood discov ered the first reli able way to cal cu late the age of a rock. Since some rocks are nearly as old as the earth, dating these rocks provided the first rea son able es ti mate of Earth’s age. Boltwood’s dis covery also allowed sci entists to date indi vid ual rock layers and strata and to study the history of Earth’s crust. It led to ag ing tech niques devel oped for plants, docu ments, soci et ies, and an cient buildings. Boltwood gave back to geol ogy a sense of time that the misestimates of pre vi ous re search ers had taken away.

How Was It Discov ered?

How Was It Discov ered? Radio ac tiv ity was dis covered by Marie Cu rie at the end of the nineteenth cen tury. In 1902 Freder ick Soddy (who later discov ered isotopes) and Ernst Rutherford jointly discov - ered that ura nium and tho rium ra dio ac tively de cayed at a con stant rate. (It al ways takes ex - actly the same amount of time for ex actly half of the ra dioac tive atoms in a sample to de cay. It’s called a half-life.) They also discov ered that these two ra dioac tive ele ments fissioned (radio ac tively decayed) into other ele ments in a fixed sequence—they always fissiioned in the same way into the same ele ments. The stage was set for someone to figure out how to use this new information. Bertram Boltwood was born in 1870 in Amherst, Massa chu setts. He stud ied phys ics (and later taught physics) at Yale Univer sity. While doing research in 1905, Boltwood noticed that when he ana lyzed the compo si tion of miner als contain ing uranium or thorium, he always found lead. Thinking that this find might be signif i cant, he studied 43 mineral samples and ranked them by their es ti mated age. The amount of lead in these sam ples al ways in creased as the samples grew older, just as the amount of uranium in them decreased. Boltwood concluded 119 120 Ra dio ac tive Dat ing

that the radio ac tive decay series starting with uranium ended by creat ing lead—which was not radio ac tive. (Uranium eventu ally decayed into lead.) He studied the same process with thorium miner als and found the same result. Boltwood surmised that, if uranium and thorium decayed at fixed, known rates, then he should be able to use the amount of lead and the amount of either of these radio ac tive ma- teri als in a rock sam ple to de termine how old the rock is—that is, how long it had been since the ra dioac tive de cay pro cess in that rock be gan. In his test samples, he used a Geiger counter to esti mate how many at oms of uranium de cayed per minute and an early mass spec- trom e ter to de ter mine how much of each trace el e ment existed in the rock sample. Knowing how much lead and uranium currently existed in the sample, knowing how fast the uranium de cayed, and knowing the half-life of that partic u lar uranium iso tope, Boltwood could then calcu late how long radio ac tive decay had been occur ring in that rock. This would tell him how old the rock was. In 1907 Boltwood published his calcu la tions for the ages of 10 mineral samples. In every case they were startlingly old, showing that these rock samples (and the earth) were tens—and even hundreds—of times older than previ ously thought. Boltwood esti mated the age of Earth at over 2.2 billion years (low based on present knowledge, but well over 10 times older than any previ ous estimate). In 1947 Ameri can chemist Willard Libby real ized that the re cently discov ered car bon isotope, carbon-14, could be used to date plant and ani mal remains in the same way that uranium was used to date rocks. Libby’s carbon-14 dating accu rately dated plant tissue back to 45,000 years and has been used to date paper samples as well as plant tissue.

Fun Facts: Ra diomet ric dating can be per formed on sam ples as small as a billionth of a gram. The uranium-lead radio met ric dating scheme is one of the oldest available, as well as one of the most highly respected. It has been refined to the point that any error in dates of rocks about three billion years old is no more than two million years. The measure ment is 99.9 per cent ac cu rate.

More to Ex plore

More to Explore Badash, Law rence, ed. Rutherford and Boltwood: Letters on Radio ac tiv ity. New Ha- ven, CT: Yale Univer sity Press, 1999. Dickin, Alan. Ra dio genic Iso tope Ge ol ogy. New York: Cambridge Univer sity Press, 2005. Glut, Don ald. Carbon Dates. Jef ferson, NC: McFarland & Co., 1999. Liptak, Ka ren. Dating Dino saurs and Other Old Things. New York: Lerner Publish ing Group, 1998. Roth, Etinne. Nuclear Methods of Dating. New York: Springer-Verlag, 1997. Func tion of Chro mo somes

Func tion of Chro mo somes FUNCTION OF CHROMOSOMES Year of Dis cov ery: 1909

What Is It? Genes are grouped (linked) in groups that are strung along chro mo somes. Who Dis cov ered It? T. H. Morgan

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Morgan’s discov ery that genes were linked into groups and strung along chromo somes was the second major step in peeling back the mystery of hered ity and evo lution. Morgan’s discov ery formed much of the founda tion for later discov er ies of how genes and chromo - somes do their work as well as the struc ture of the DNA molecule. Men del es tab lished that traits (called “genes”) are passed from par ents into the next gen er a tion. Dar win es tab lished the con cepts that dic tated evo lu tion of spe cies. Still, sci ence had no idea how species evolved or how indi vid ual genes were passed to new generations. Studying a species of fruit flies, Profes sor T. H. Morgan at Colum bia Univer sity both proved that Mendel’s theory was correct and estab lished the exis tence of chromo somes as the car ri ers for genes.

How Was It Discov ered?

How Was It Discov ered? By 1910, 44-year-old profes sor T. H. Morgan was the head of the biol ogy depart ment at New York’s Colum bia Univer sity. All his energy, however, he saved for his research. Morgan refused to accept Mendel’s theo ries on hered ity. Morgan didn’t believe in the exis - tence of genes since no one had physically seen a gene. Neither did he accept Darwin’s concept of survival of the fittest as the driving force of evolu tion. Morgan believed that evolu tion came from random muta tions that slowly worked their way into and through a popu lation. Morgan created “The Fly Room” to prove his ideas. Morgan’s Fly Room labo ra tory was a small, messy room with the overpow er ing reek of rotting bananas. Two walls were lined floor to ceiling with rows of corked glass bottles contain ing tens of thousands of tiny fruit flies. Their constant buzz was diffi cult to talk over. He chose to study fruit flies for four reasons. First, they were small (only ¼-inch long). Sec ond, they lived their entire lives on nothing but mashed ba nana. Third, they created a new gener a tion in less than two weeks. Morgan could study almost 30 gener a tions a year. Finally, they had few genes and so were much easier to study than more complex species.

121 122 Func tion of Chro mo somes

Morgan searched and waited for a random physi cal muta tion (like eye color) to appear in one of the thousands of fruit flies born each month. He would then carefully track that muta tion through subse quent gener a tions to see if spread across the popu la tion and proved his the ory. It was a mind-numbing effort for Morgan and his as sis tants. Each month, many thousands of new fruit flies had to be carefully ex amined under the microscope for mutations. In Septem ber 1910 Morgan found a muta tion—a male fruit fly with clear white eyes in stead of the nor mal deep red. The white-eyed male was care fully seg re gated in his own bot tle and mated with a nor mal red-eyed female. If the eyes of these hatchlings were white, off-white, or even rose colored (as Morgan believed they would be), this random mu tation—that provided no real Darwin ian survival bene fit or ad vantage—would have evolved (perma nently changed) the species and Mor- gan’s theory of evo lution by muta tion would have been confirmed. It took three days to ex amine the 1,237 new flies. Every one had normal red eyes. Mor- gan was crushed. The mu tation had disap peared. It hadn’t changed the species at all. Mor- gan was wrong. By Octo ber 20 the grandchil dren of the origi nal white-eyed male were hatched. One-quarter of this gen era tion had white eyes; three-quarters had normal red eyes. 3 to 1: That was Mendel’s ratio for the in ter action of a dom i nant and a reces sive characteristic. T. H. Mor gan’s own exper i ment had just proved himself wrong and Mendel’s gene theory right! Addi tional muta tions occurred frequently over the next two years. By studying these muta tions and their effect on many gener a tions of descendents, Morgan and his assis tants real ized that many of the inher ited genes were always grouped together. (They called it “linked.”) By 1912 the team was able to estab lish that fruit fly genes were linked into four groups. Knowing that fruit flies had four chromo somes, Morgan suspected that genes must be strung along, and carried by, chromo somes. Af ter 18 months of ad ditional research, Mor- gan was able to prove this new theory. Chromo somes carried genes, and genes were strung in fixed-order lines (like beads) along chromosomes. While attempt ing to dis prove Men del’s work, Mor gan both con firmed that Mendel was right and discov ered the function of chromo somes and the rela tion ship between chro - mosomes and genes.

Fun Facts: Fruit flies can lay up to 500 eggs at a time, and their entire lifecycle is com plete in about a week.

More to Ex plore

More to Explore Aaseng, Na than. Ge net ics: Un lock ing the Se crets of Life. Min ne ap o lis, MN: Ol i ver Press, 1996. Allen, Garland. Thomas Hunt Mor gan: The Man and His Science. Princeton, NJ: Prince ton Uni ver sity Press, 1996. Edey, Maitland, and Donald Johanson. BLUEPRINTS: Solving the Mystery of Evolu - tion. New York: Penguin Books, 1994. More to Explore 123

Riley, Her bert. Thomas Hunt Mor gan. Frankfurt: Kentucky Academy of Sciences, 1994. Sherrow, Vic to ria. Great Sci en tists. New York: Facts on File, 1998. Shine, Ian. Thomas Hunt Mor gan, Pio neer of Ge netics. Frank furt: Uni ver sity Press of Ken tucky, 1996. Sturtevant, A. H. A History of Genet ics . Cold Spring Harbor, NY: Cold Spring Harbor Lab o ra tory Press, 2001. Anti bi ot ics

ANTIBIOTI CS ANTIBIOTI CS Year of Dis cov ery: 1910

What Is It? Chem i cal sub stances that kill in fec tious mi cro scopic or gan isms without harm ing the human host. Who Dis cov ered It? Paul Ehrlich

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The word “an tibi otic” comes from the Greek words mean ing “against life.” Early folk medi cine relied on some natu ral compounds that cured cer tain diseases—the ground bark of a tree, cer tain cheese molds, cer tain fungi. Doc tors knew that these nat u ral compounds worked, but had no idea of how or why they worked. Paul Ehrlich con ducted the first mod ern chem i cal in ves ti ga tion of an ti bi ot ics and discovered the first an tibi otic chemi cal compounds. His work opened a new era for medi cal and phar ma co log i cal re search and founded the field of che mo ther apy. An ti bi ot ics (pen i cil- lin, dis covered in 1928, is the most fa mous) have saved many millions of lives and trace their modern origin to Paul Ehrlich’s work.

How Was It Discov ered?

How Was It Discov ered? Paul Ehrlich was born in Germany in 1854. A gifted student, he entered gradu ate school to study for a medi cal degree. There he became deeply involved in the process of staining micro scopic tissue samples so that they would show up better under the micro - scope. The problem was that most dyes destroyed the tissue samples before they could be viewed. Ehrlich struggled to find new dyes that wouldn’t harm or kill del icate mi croscopic organ isms. This work showed Ehrlich that some chem i cal com pounds killed some types of tissue and made him won der if the process could be controlled. By 1885 it had become clear that the causative agent for many illnesses was micro or - ganisms. Many sci entists made a great effort to study these bac teria under the micro scope. Again Ehrlich found that many of the available dyes and stains killed the organ isms before they could be studied. This find ing inspired Ehrlich to propose that chemi cal compounds may ex ist that could kill these organ isms without harm ing the human pa tient, thus curing an illness by killing only its causative agent. In the mid-1890s, Ehrlich shifted his focus to studies of the immune system and how to control the reac tion between chemi cal toxins and anti tox ins. Again it occurred to Ehrlich that, just as anti tox ins specif i cally sought a toxin mole cule to which they were related and destroyed it, so, too, he might be able to create a chemi cal substance that would go straight 124 More to Explore 125

to some disease-caus ing organ ism and destroy it. Ehrlich called such a chemi cal substance a “magic bullet.” It seemed that 25 years of work had led him directly to this idea. Dur ing this same period, many spe cific dis ease-caus ing bac te ria were being identi fied and stud ied. This gave Ehrlich well-un derstood targets to attack as he sought ways to cre ate magic bullets. He chose to start with spirochaete, the mi cro or ganism that caused syph i lis. Ehrlich began testing differ ent chemi cals using an arsenic base for his compounds. Arsenic had been effec tive in destroy ing a number of other microorganisms. By 1907, Ehrlich had reached the 606th compound to be tested. He tested this compound on rabbits in fected with syphi lis. It cured the rabbits. Ehrlich named it sal var san and conducted over 100 ad ditional tests to be sure it worked and that it wouldn’t harm human patients. He then worked for two more years to develop a form of this drug that was eas ier to manu fac ture and that was easier to admin is ter. Of the thousand varia tions he tried, version number 914 was the best. He named it neo sal var san. Ehrlich’s final test of neo salvar san was to give it to termi nal pa tients suffer ing from the demen tia that was the final stage of syphi lis. While neosal varsan helped all of these patients, re mark ably, sev eral com pletely recovered. Neo sal var san was the first man-made chemi cal that would spe cif i cally de stroy a target organ ism and not affect the human patient. This discov ery founded the field of che mo ther apy.

Fun Facts: Resis tance to anti bi ot ics works by the ordi nary rules of natu - ral selec tion: that segment of the bacte ria popu la tion that has a natu ral ability to counter the drug’s effect will survive, so that their genes even- tually are shared by the entire popu la tion. Many disease-caus ing viruses and bac te ria have de vel oped vir tual im mu nity to many an ti bi ot ics, making med i cal plan ners fear massive dis ease out breaks in the near fu ture.

More to Ex plore

More to Explore Asimov, Isaac. Asimov’s Chronol ogy of Science and Dis covery . New York: Harper & Row, 1989. Baumier, Er nest. Paul Ehrlich: Sci entist for Life. Teaneck, NJ: Holmes & Meier, 1994. Dyson, James. A His tory of Great Inven tions . New York: Carroll & Graf Pub lishers, 2001. Ehrlich, Paul. Stud ies in Im mu nity. New York: John Wiley & Sons, 1990. Pickstone, John, ed. Med i cal In no va tions in His tor i cal Per spec tive. New York: Palgrave Macmillan, 1993. Zannos, Susan. Paul Ehrlich and Mod ern Drug De vel op ment . Hockessin, DE: Mitch- ell Lane, 2002. Fault Lines

FAULT LINES FAULT LINES Year of Dis cov ery: 1911

What Is It? Earth quakes happen both along, and be cause of, fault lines in the earth’s crust. Who Dis cov ered It? Harry Reid

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Scien tists now know that they can predict the loca tions of future earthquakes by mapping the lo cations of fault lines. However, just a cen tury ago this simple truth was not known. Harry Reid’s discov ery that earthquakes happen along exist ing fault lines provided the first under stand ing of the source and pro cess of earthquakes. This discov ery laid the foundation for the dis covery of Earth’s crustal plates and plate tec tonics in the late 1950s. Reid’s discov ery was called a major breakthrough in earth science and provided the first basic un derstand ing of Earth’s inter nal processes and of how rocks behave under stress.

How Was It Discov ered?

How Was It Discov ered? By 1750, scien tists knew that there were fault lines (like long cracks) snaking through Earth’s upper crust where two dis sim ilar kinds of rocks came to gether. By 1900, scien tists knew that these fault lines were as so ci ated with earth quakes. The mis take sci en tists made, how ever, was to agree that earth quakes caused the fault lines. It was as though the crust had been a smooth block of rock that had been cracked by an earthquake, with one side sliding past the other to create the rock mis match. Earthquakes hap pened, and fault lines were the tell tale res i dues of past earthquakes. Harry Fielding Reid was born in Balti more in 1859. When he received his early schooling in Switzer land, these ideas were what were taught in geol ogy classes. They were what Reid learned. How ever, earth quakes and fault lines were of lit tle in ter est to Reid. Liv - ing in Switzer land focused his pri mary inter est on mountains and glaciers. Reid returned to Balti more to attend college at Johns Hopkins Univer sity in 1865 (at the age of 16). He stayed long enough to receive a doctor ate in geol ogy in 1885. Begin ning in 1889, Reid took posi tions as a univer sity profes sor with a research empha sis on glaciers. Reid traveled exten sively through Alaska and the Swiss Alps mapping and studying gla ciers, their move ment, their for mation, and their ef fects on the land scape. He wrote ar ti - cles and pa pers on glacial structure and movement. 126 More to Explore 127

In April 1906 the great San Francisco earthquake struck and most of the city either top- pled or was burned. In late 1906 the state of Cali for nia formed the Cali for nia State Earth- quake In vesti ga tion Com mis sion to study the San Fran cisco earthquake and to deter mine the risk to the state of pos sible future earthquakes. Reid was asked to serve as a member of this nine-member commission. This commis sion study turned Reid’s inter est toward earthquakes and fault lines. He mapped and stud ied the San Andreas fault line and roamed the central Cal ifor nia coastal region map ping other fault lines. Always he searched for an answer to the question: What caused earthquakes? Reid carefully studied the rocks along Cali for nia fault lines and con cluded that they suffered from long-term physi cal stress, not just from the jolt of a sudden earthquake. Reid saw that great stresses must have existed in the rocks along the San Andreas fault line for cen tu ries—even for mil len nia—be fore the earth quake happened. That meant that the fault lines had to have ex isted first and stress along them caused the earthquake. Stress built up and built up in the rocks un til they snapped. That “snap” was an earth quake. Reid devel oped the image of the rock layers along fault lines acting like rubber bands. Stresses deep in the earth along these fault lines pulled the rocks in dif ferent direc tions, caus ing these rocks to stretch—like elas tic. Once the stress reached the break ing point, the rocks elasti cally snapped back—causing an earthquake. Fault lines caused earthquakes, not the other way around. That meant that studying fault lines was a way to pre dict earthquakes, not merely study their after math. Reid had discov ered the sig nif i cance of the earth’s spi der web maze of fault lines.

Fun Facts: The de struc tive San Fran cisco earthquake of 1906 hori zon - tally shifted land surfaces on either side of the San Andreas fault up to 21 ft (6.4 m).

More to Ex plore

More to Explore Branley, Franklyn. Earthquakes . New York: HarperTrophy, 1998. Har ri son, James. Dis cover Amaz ing Earth. New York: Sterling Publish ing Co., 2005. Sherrow, Vic to ria. Great Sci en tists. New York: Facts on File, 1998. Thomas, Gordon. The San Fran cisco Earthquake. New York: Day Books, 1996. Ulin, David. The Myth of Solid Ground. New York: Penguin, 2005. Su per con duc tiv ity

SUPERCONDUCTIVITY SUPERCONDUCTIVITY Year of Dis cov ery: 1911

What Is It? Some ma te ri als lose all re sis tance to elec tri cal cur rent at super-low tem per a tures. Who Dis cov ered It? Heike Kamerlingh Onnes

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Super con duc tiv ity is the flow of electri cal current without any resis tance to that flow. Even the best conduc tors have some resis tance to electri cal current. But super con duc tors do not. Unfor tu nately, super con duc tors only exist in the ex treme cold of near absolute zero. Even though the practi cal appli ca tion of this dis covery has not yet been real ized, super con duc tiv ity holds the prom ise of super-ef fi cient elec tri cal and mag netic mo tors, of electri cal current flowing thousands of miles with no loss of power, and of meet ing the dream of cheap and ef fi cient elec tric ity for ev ery one. Su per con duc tiv ity will likely spawn whole new in dustries and ways of gener at ing, process ing, and mov ing electri cal energy. But that potential still lies in the future.

How Was It Discov ered?

How Was It Discov ered? Heike Onnes was born in 1853 in Groningen, the Nether lands, into a wealthy family that owned a brick making factory. As he went through college and gradu ate school, he drew consid er able atten tion for his talent at solving scien tific problems. By the time he was 18, Onnes had become a firm believer in the value of physi cal experimentations and tended to discount the o ries that could not be demon strated by physical experiment. At the age of 25, Onnes focused his univer sity research on the proper ties of ma teri als at tem per a tures ap proach ing the cold est pos si ble tem per a ture (-456°F or -269°C). The ex is - tence of that tem per a ture, the tem per a ture at which all heat en ergy is gone and all mo tion —even inside an atom—ceases, was discov ered by Lord Kelvin, and is called 0° Kelvin (0°K) or ab so lute zero. Several theo ries existed about what happened near 0°K. Lord Kelvin believed that absolute zero would stop the motion of elec trons. Elec trical current would cease and re sis- tance to that current would be infi nitely large. Others believed the oppo site—that resis tance would fall to zero and electri cal currents would flow forever. Every one had a theory. Onnes decided to find out, to test the theo ries.

128 How Was It Discov ered? 129

However, there was a prob lem. No method ex isted to cool any thing anywhere near -269°C. Luckily, Onnes was the physics depart ment chair at the Uni versity of Leyden, and that de partment came equipped with a well-funded phys ics lab that Onnes could use. In 1907 Onnes invented thermom e ters that could measure temper a tures as extreme as abso lute zero. In 1908 he discov ered a way to cool the gas helium so cold that it turned into a liq uid. He was able to continue to chill the super-cold liq uid un til, late that year, he chilled liquid helium to 0.9°K—less than one degree above ab solute zero! Onnes real ized that he could use this liq uid he lium to chill other mate ri als to near 0°K to mea sure their electrical resistance. By 1911 Onnes had devel oped canis ters capa ble of holding and storing his super-cold liquid helium and had set up a small produc tion line. He began his electri cal studies by chill- ing first plati num and then gold to near abso lute zero. However, the electri cal currents he measured were er ratic, his results inconclusive. Onnes decided to switch to liquid mercury. He filled a U-shaped tube with mercury and at tached wires to each end of the U. The wires were at tached to a me ter to measure elec - trical resis tance. He used liquid helium at 0.9°K to cool the mercury. As the temper a ture dipped below 40°K (-229°C) electri cal resis tance began to drop. It dropped steadily as the temper a ture dipped below 20°K. And then, at 4.19°K resis tance abruptly disap peared. It fell to zero. Onnes repeated the exper i ment many times over the next few months and al ways got the same re sult. Be low 4.19°K, there was no re sis tance to the flow of elec tric ity. An elec tric current would flow un impeded for ever! He called it su per con duc tiv ity. Onnes had dis cov ered su per con duc tiv ity, but he could not the o ret i cally ex plain it. He only sus pected that it had some thing to do with the (then) recently discov ered Quantum Theory. It was not until 1951 that John Bardeen devel oped a mathe mat i cal theory to explain superconductivity. A search began to find ways to create super con duc tiv ity at higher (more practi cally reached) tem per a tures. The cur rent re cord (us ing—un for tu nately—toxic ce ramic com - pounds made with mercury and copper) is 138°K (-131°C). Once a way is found to create super con duc tiv ity at warmer tem pera tures, the value of Onnes’s discovery will be unlimited.

Fun Facts: AT CERN, the Euro pean high-energy phys ics research lab, scien tists used a one-time jolt of electric ity to start an electri cal current flow ing through a su per con duc tor cir cuit. That elec tri cal cur rent ran—with no addi tional voltage input—for five years with no loss of power. In common house wires, an electri cal current would stop within a few mil li sec onds once the volt age is re moved be cause of the re sis tance of elec tri cal wires. 130 Su per con duc tiv ity

More to Ex plore

More to Explore Ford, P. J. The Rise of Su per con duc tors. New York: CRC Press, 2005. Gale Ref er ence. Bi og ra phy: Heike Kamerlingh Onnes. New York: Gale Research, 2004. Lampton, Chris to pher. Su per con duc tors. Berkeley Heights, NJ: Enslow, 1997. Matricon, Jean. The Cold Wars: A History of Super con duc tiv ity. New Bruns wick, NJ: Rutgers Univer sity Press, 2003. Shachtman, T. Abso lute Zero and the Conquest of Cold. New York: Houghton Mifflin, 1999. Atomic Bond ing

Atomic Bonding ATOMIC BONDING Year of Dis cov ery: 1913

What Is It? The first working theory of how electrons gain, lose, and hold energy and how they orbit the nu cleus of an atom. Who Dis cov ered It? Niels Bohr

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Marie Cu rie opened the century by proving that there was a subatomic world. Ein stein, Dirac, Heisenberg, Born, Rutherford, and others provided the new theo reti cal descrip tions of this subatomic world. But prov ing what lurked within an atom’s shell, and what gov- erned its be havior, lin gered as the great phys ics chal lenges of the early twentieth century. It was Niels Bohr who discov ered the first con crete model of the electrons surround ing an atom’s nucleus—their placement, motion, radi a tion patterns, and energy transfers. Bohr’s theory solved a number of incon sis ten cies and flaws that had existed in previ ous at - tempts to guess at the structure and activ ity of electrons. He combined direct exper i ment with advanced theory to create an under stand ing of electrons. It was an essen tial step in science’s march into the nuclear age.

How Was It Discov ered?

How Was It Discov ered? Niels Bohr was only 26 in 1912—very young to step into the middle of a heated physics contro versy. But that spring, as a new physics profes sor at the Univer sity of Copen ha - gen, Bohr real ized atomic the ory no longer matched the growing body of exper i men tal atomic data. One of Bohr’s exper i ments showed that clas si cal the o ries predicted that an or - biting electron would contin u ously lose energy and slowly spiral into the nucleus. The atom would collapse and implode. But that didn’t happen. Atoms were amazingly stable. Some- thing was wrong with the existing theories—and Bohr said so. There was no way to actu ally see an atom, no way to peer inside and directly observe what was go ing on. Sci entists had to grope in the dark for their the o ries, sifting through in- direct clues for shreds of insight into the bi zarre workings of atoms. Atomic exper i ment ers were building mountains of data. They recorded the parti cles cre ated from atomic col li sions. They mea sured the an gles at which these new par ti cles raced away from the col li sion site. They mea sured elec tri cal en ergy lev els. But few of these data fit with atomic theories.

131 132 Atomic Bond ing

As Bohr began to orga nize his teaching in 1913, he read about two new ex peri men tal studies. First, Enrico Fermi found that atoms always emitted en ergy in the same few amounts (or bursts) of energy. He called these bursts discrete quanta (quanti ties) of energy. Second, chemists had studied the amount of energy that each ele ment’s atoms radi - ated. They found that if they passed this radi a tion through a prism, the radi a tion was not contin u ous over the whole frequency spectrum, but came in sharp spikes at cer tain discrete fre quen cies. Dif fer ent el e ments showed dif fer ent char ac ter is tic pat terns in these en ergy spikes. Neither study fit with existing theories. Bohr studied and compared these differ ent, and appar ently unre lated, bits of data, know ing that the new data had to re late some how—since they dealt with char acter is tics and emis sions from the same source: atoms. Bohr sifted and resifted the data and the theo ries over an eight-month period, searching for a way to make the ex per i men tal data fit with some atomic the ory. By late that year he had discov ered a revo lu tion ary idea: Electrons must not be as free to roam as previ ously thought. He theo rized that the electrons circling an atom’s nucleus could only exist in certain, discrete, fixed orbits. In order to jump to a closer orbit, an electron would have to give off a fixed amount of energy (the observed spikes and quanta of radi ated energy). If an elec tron were to jump into a higher orbit, it would have to ab sorb a fixed quanta of en ergy. Elec trons couldn’t go wherever they wanted or carry any amount of energy. Electrons must be in one or another of these few specific orbits. Electrons must gain and lose energy in specific quanta. Bohr’s atomic model was a revo lution ary idea and a complete depar ture from previ ous ideas. How ever, it fit well with exper i men tal obser vations and explained all of the incon sis - tencies of pre vious the o ries. This model also ex plained how and why chem ical ele ments bonded with each other as they did. Bohr’s discov ery re ceived in stant ac claim and accep tance. For 50 years it served as the accepted model of an atom and of the mo tion of elec trons within the atom.

Fun Facts: Niels Bohr worked at the secret Los Alamos lab o ratory in New Mex ico, on the Manhattan Pro ject (the code name for the ef fort to develop atomic bombs for the United States during World War II).

More to Ex plore

More to Explore Aserud, Finn. Redi rect ing Science: Niels Bohr and the Rise of Nuclear Physics. Lon- don: Cambridge Univer sity Press, 1990. Blaedel, Niels. Harmony and Unity: The Life of Niels Bohr. Chi cago: Sci ence Tech - nol ogy Pub lish ing, 1988. Moore, Ruth. Niels Bohr: The Man, His Science, and the World They Changed. Cam- bridge, MA: MIT Press, 1985. Murdoch, D. R. Niels Bohr’s Philos o phy of Physics. Lon don: Cam bridge Uni ver sity Press, 1999. Rozental, S. Niels Bohr: His Life and Work. New York: John Wiley & Sons, 1997. Iso topes

Iso topes ISOTOPES Year of Dis cov ery: 1913

What Is It? Iso topes are dif fer ent forms of the same chem i cal el ement that have iden ti cal phys i cal and chem i cal prop er ties but dif fer ent atomic weights. Who Dis cov ered It? Fred er ick Soddy

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Isotopes of an ele ment are slightly differ ent forms of that ele ment. Isotopes have the same chem i cal, phys i cal, and elec tri cal prop er ties as the origi nal el ement, but have a dif fer - ent number of neutrons in their nucleus. The discov ery of isotopes created a new dimen sion and concept for physics and chemistry. This discov ery an swered baffling problems that had stymied physics research ers studying radio ac tive ele ments. The study of isotopes became a key founda tion for the develop ment of atomic power and weapons. Isotopes are also criti cal to geol ogy since carbon dating and other rock-dating tech niques all de pend on the ratios of specific isotopes. This one discov ery removed roadblocks to scien tific progress, opened new fields of physics and chem is try research, and pro vided es sen tial re search tools to earth science re - search.

How Was It Discov ered?

How Was It Discov ered? Freder ick Soddy was born in 1877 in Sussex, England. In 1910 Soddy accepted a posi - tion at the Univer sity of Glasgow as a lecturer in radio ac tiv ity and chemistry. The study of ra dio ac tive el e ments was still ex cit ing and new. Ra dio ac tive el e ments were identi fied by dif fer ences in their mass, atomic charge, and ra dioac tive proper ties, in - cluding the kinds and en ergies of differ ent particles they emitted. However, using this system, scien tists had already identi fied 40 to 50 radio ac tive ele - ments. But there existed only 10 to 12 places for all of these radio ac tive ele ments on the peri - odic chart of ele ments. Either Mendeleyev’s peri odic chart was wrong or—for some unknown reason—ra dio ac tive ele ments fell outside the logic and order of the peri odic chart. Nei ther an swer made any sense, and ra dio ac tive re search ground to a halt. Soddy decided to study the three known subatomic parti cles emitted by the vari ous ra- dioac tive ele ments (alpha, beta, and gamma parti cles). Soddy found that alpha parti cle held a posi tive charge of two (as would two protons) and a mass equal to four protons. Gamma

133 134 Iso topes

rays had nei ther charge nor mass, only energy, so they didn’t affect the na ture of the atom at all. Beta par ti cles had no mea sur able mass but held a neg ative charge of one. They were ap par ently just elec trons. When an atom emit ted a beta par ti cle, it lost a neg a tive charge. Soddy re al ized that was the same as gain ing a posi tive charge. Emit an alpha par ticle and lose two posi tive charges from the nucleus. Emit a beta parti cle and gain one. Because the peri odic table was orga nized by the number of protons in the nucleus of an atom—from the lightest ele ment (hydro gen) up to the heaviest known ele ment (uranium), Soddy real ized that the emission of an alpha par ticle would, in effect, shift the atom two spaces to the left on the peri odic chart and the emission of a beta parti cle shifted it one place to the right. It must be, he concluded, that atoms of many ele ments could exist in several differ ent spaces on the peri odic chart. Soddy used new spectro graphic research techniques (discov - ered by Gustav Kirchhoff and Robert Bunsen in 1859) to show that—even though they had a differ ent atomic mass and so occu pied dif ferent spaces on the peri odic chart—atoms of uranium and thorium were still the same, original element. This meant that more than one ele ment could occupy the same spot on the peri odic chart and that atoms of one el ement could oc cupy more than one spot and still be the same, origi nal ele ment. Soddy named the versions of an ele ment that oc cupied spots on the peri - odic chart—other than that ele ment’s “normal” spot—iso topes, from the Greek words meaning “same place.” Later that same year (1913), Amer i can chem ist Theo dore Rich ards mea sured the atomic weights of lead isotopes result ing from the radio ac tive decay of uranium and of thorium and proved Soddy’s theory to be true. However, Soddy’s ex plana tion of his discov ery was not completely ac curate. Chadwick’s discov ery of the neu tron (in 1932) was needed to correct Soddy’s errors and to complete the under stand ing of Soddy’s concept of isotopes. Soddy had tried to ex plain his iso topes using only protons and electrons. Chadwick discov ered that as many neutrally charged neutrons existed in the nucleus as did posi tively charged protons. Gaining or los ing neutrons didn’t change the electric charge of or the proper ties of the ele ment (since ele ments were defined by the number of protons in the nucleus). It did, however, change the atomic mass of the atom and so created an isotope of that element. Soddy discov ered the concept of isotopes. But an under stand ing of neutrons was needed in order to fully under stand them.

Fun Facts: Isotopes are more impor tant than most people think. Every ancient rock, fossil, human remain, or plant ever dated was dated using iso topes of var i ous el e ments. Nat u ral ra dio ac tiv ity is cre ated by iso topes. The atomic bomb uses an isotope of uranium. More to Explore 135

More to Ex plore

More to Explore Clayton, Donald. Handbook of Iso topes in the Cosmos. New York: Cambridge Uni- versity Press, 2003. James, Richard. Ad ven tures of the El e ments. Pittsburgh: Three Rivers Council, 1997. Kauffman, George. Fred erick Soddy: Early Pi o neer in Radiochemistry. New York: Springer, 2002. Mer ricks, Linda. The World Made New: Freder ick Soddy, Science, and Envi ron ment. New York: Ox ford Uni versity Press, 1996. Rattanski, P. M. Pi o neers of Sci ence and Dis cov ery. Charleston, WV: Main Line Books, 1997. Earth’s Core and Mantle

EARTH’S CORE AND MANTLE EARTH’S CORE AND MANTLE Year of Dis cov ery: 1914

What Is It? The earth is made up of lay ers, each of a differ ent den sity, temper - a ture, and com po si tion. Who Dis cov ered It? Beno Gutenberg

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? It is impos si ble to see, to venture, or even to send probes more than a few miles under the surface of Earth. Almost all of the 4,000+ miles from the surface to the center is un- reachable to humans. Yet scien tists could not begin to under stand our planet and its forma - tion without having an accu rate knowledge of that interior. Beno Gutenberg provided the first rea sonable account ing of Earth’s inte rior. His dis - covery proved that Earth wasn’t a solid homo ge neous planet, but was divided into layers. Gutenberg was the first to cor rectly es ti mate the temper ature and phys i cal prop er ties of Earth’s core. His dis cover ies have been so impor tant that he is often con sidered the father of geophysics.

How Was It Discov ered?

How Was It Discov ered? Born in 1889 in Darmstadt, Germany, Beno Gutenberg loved science as a boy and always knew he’d be a mete o rolo gist. As he began his sec ond year of univer sity mete o rolog i - cal study in 1907, he saw a notice announc ing the forma tion of a depart ment of the new sci ence of geophys ics (Earth physics) at the University of Göttingen. The idea of a whole new sci ence fas ci nated Gutenberg. He trans ferred to Göttingen and, while holding onto a major in mete o rology, studied under Emil Wiechert, a pi o neer in the emerging science of seismol ogy—the study of seismic waves caused by earthquakes and earth tremors. By the time of his gradu a tion in 1913, Gutenberg had shifted from mete o rol ogy (study of the atmo sphere) to geo physics (study of Earth’s inte rior). It was a case of be ing in the right place at the right time. Gutenberg had ac cess to all of Wiechert’s data and stud ies, the most exten sive and com prehen sive collec tion of seis mic data in the world. Wiechert had focused on collect ing the data. Gutenberg focused on studying the patterns of those data. Gutenberg found that, typi cally, seismic waves did not reach all parts of the earth’s surface, even when the tremor was strong enough to have been de tected ev erywhere. There al ways ex isted a shadow zone more or less straight across the globe from an event where no seis mic waves were ever de tect able. 136 More to Explore 137

He also no ticed that seis mic waves seemed to travel at dif fer ent speeds on dif fer ent tra - jecto ries through the earth. This all made Gutenberg suspect that the inte rior of the earth was not a solid, homo ge neous mass. It must have sev eral sep arate layers or regions. Gutenberg set tled on the im age of the earth as an egg. The sur face of the earth was thin and brit tle like an eggshell. He real ized that there must be a core to Earth (like an egg yoke) that was more dense than the surround ing man tle (the egg white). If this image held true, seismic waves approach ing the core would change speeds and be diffracted (bent) because of the density differ ence between layers. One of the kinds of seismic waves that Gutenberg studied was trans verse waves. These waves would not enter the core at all. Knowing that transverse waves dissi pate quickly in the liquid ocean, Gutenberg surmised that Earth’s core also had to be liquid. Gutenberg had enough data from the re corded diffrac tions of enough seismic waves to calcu late how big the core had to be and what its density had to be in order to create the dif - fraction patterns seismol o gists recorded. The core of the earth, he said, had a radius of 2,100 miles. Based on these calcu la tions, on chem ical exper i ments he ran in early 1914, and on the measured chem i cal com po si tion of me te or ites, Gutenberg es ti mated that the core was a liq - uid mixture of nickel and iron, while the mantel was made up of rock material. Gutenberg’s model was quickly accepted and was not improved upon until 1938. In that year, Inge Lehman completed a detailed study of “P” waves (another kind of seismic wave) with vastly improved equipment from that used in 1914. Her research showed that Earth’s core was di vided into a solid inner core and a sur rounding liquid outer core. She also broke the mantle into an inner and an outer mantle. This discov ery completed our basic image of Earth’s interior.

Fun Facts: The crust of the earth is solid. So is the inner core. But in between, the outer core and man tle (90 percent of the mass of the earth) are liquid to molten semi-solid. We do not live on a partic u larly solid planet.

More to Ex plore

More to Explore Crossley, D. Earth’s Deep Inte rior. Abingdon, England: Taylor & Francis, 1997. Gib bons, Gail. Planet Earth: Inside Out. New York: HarperCollins, 1998. Gutenberg, Beno. Seis mic ity of the Earth and As so ci ated Phe nom ena. New York: Text book Pub lish ers, 2003. Jacobs, John. Earth’s Core. Chevy Chase, MD: Elsevier Science Books, 1997. Manzanero, Paula, ed. Scho las tic At las of Earth. New York: Scholas tic, 2005. Vogt, Gregory. Earth’s Core and Asthenosphere. New York: Lerner Group, 2004. Conti nen tal Drift

CONTINENTAL DRIFT CONTINENTAL DRIFT Year of Dis cov ery: 1915

What Is It? Earth’s con tinents drift and move over time. Who Dis cov ered It? Al fred Wegener

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Before Wegener’s discov ery, scien tists thought that the earth was a static body—never changing, now as it always has been. Al fred Wegener’s discov ery that Earth’s con tinents drift across the face of the planet led to modern tectonic plate theo ries and to a true under - stand ing of how Earth’s crust, mantel, and core move, flow, and inter act. It created the first sense of Earth’s dynamic history. Wegener’s discov ery solved nagging myster ies in a dozen fields of study—and stirred up new questions still be ing debated today. This dis covery stands as a corner stone of our mod ern un der stand ing of earth sciences.

How Was It Discov ered?

How Was It Discov ered? Albert Wegener was born in 1880 in Berlin. Always restless and more of a doer than a thinker, he switched his college major from as tronomy to mete o rology because “astron omy offered no oppor tu nity for physi cal activ ity.” Upon gradu a tion, Wegener signed on for mete o ro log i cal ex pe di tions to Ice land and Greenland in 1906 and 1908. While on tour in 1910, Wegener noticed the remark able fit of the coastlines of South America and Africa. He was not the first scien tist to no tice this fit, but one of the first to think that it was impor tant. In 1911, new ocean maps showed the Atlan tic Ocean conti nen tal shelves. (Con tinen tal shelves are shallow, under wa ter shelves extend ing out from conti nents.) Wegener noticed an even better fit between the con ti nen tal shelves of South Amer ica and Af rica. They “fit like pieces of a jigsaw puzzle.” Wegener knew that this perfect fit couldn’t be just a coin ci dence and sus pected that those two con tinents were once connected—even though they were now sepa rated by several thou sand miles of ocean. This was a rad i cal notion since all sci en tists as sumed that the conti nents never moved from their fixed positions on Earth. In that same year, Wegener read studies that noted the same fossil finds in South America and in corre spond ing parts of coastal Africa. Many scien tists proposed that there once ex isted a land bridge be tween the two so that plant and ani mal species could inter mix. This bridge, they as sumed, long ago sank to the bottom of the sea. 138 More to Explore 139

Wegener be lieved a land bridge was impos si ble. It would have left telltale signs on the ocean floor and would create gravi ta tional anoma lies that did not exist. In 1912, he de cided to build a body of evi dence from a vari ety of fields to prove that the conti nents had once been joined. He used the exten sive fieldwork of Eduard Suess to provide most of his geolog i cal data. Suess dis cov ered that, in place af ter place, rocks on coasts that faced each other across the oceans of ten matched exactly. Wegener poured through the findings of hundreds of geologic surveys to show that the rock forma tions, mix of rock kinds, and rock strati fi ca tion on the two conti nents (South America and Africa) matched up and down the coastline. He found forma tions known as pipes (as soci ated with di amonds) on both sides of the south Atlan tic, exactly opposite each other. He also collected re cords of past and present plant com muni ties on both sides of the Atlan tic and mapped them to show how they matched up and down the coast. The only expla na tion Wegener could offer for these simi lar i ties was that South Amer- ica and Af rica used to be joined as a single con tinent and one or both had since drifted off. He extended his theory to cover all conti nents (e.g., North America used to be joined with Europe) and arrived at the conclu sion that, at one time, all of Earth’s land masses had been joined in a sin gle mas sive con ti nent that he named Pangaea (Greek for “all Earth”) Wegener published his dis cover ies and his theory in 1915. Scien tists around the world were both skepti cal of his con clusions and im pressed by the amount of, and vari ety of, data he presented. Wegener had discov ered conti nen tal drift, but stumbled when he couldn’t say how the con tinents drifted (what force drove them through the denser oce anic floor). Forty years later, Harvey Hess discov ered sea floor spread ing and filled this hole in Wegener’s theory.

Fun Facts: The Hima la yas, the world’s highest mountain system, are the re - sult of the ongo ing colli sion of two huge tectonic plates (the Eurasia plate and the Indian sub conti nent), which began about 40 million years ago.

More to Ex plore

More to Explore Cohen, Bernard. Revo lu tions in Science. Cam bridge, MA: Harvard Univer sity Press, 1995. Hallam, Anthony. A Rev o lution in the Earth Sciences: From Conti nen tal Drift to Plate Tec ton ics. New York: Claren don Press, 1993. LeGrand, H. Drift ing Con ti nents and Shift ing The o ries. New York: Cambridge Uni- versity Press, 1998. Oreskes, Na omi. The Re jec tion of Con tinen tal Drift: Theory and Method in Amer ican Earth Sciences. New York: Ox ford Uni versity Press, 1999. Wegener, Alfred, and Kurt Wegener. The Ori gins of Conti nents and Oceans. New York: Do ver, 1996. Black Holes

BLACK HOLES BLACK HOLES Year of Dis cov ery: 1916

What Is It? A col lapsed star that is so dense, and whose grav ita tional pull is so great, that not even light can es cape it. Such stars would look like black holes in a black universe. Who Dis cov ered It? Karl Schwarzschild

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Many consider black holes to be the ulti mate wonder of the universe, the strangest of all stellar objects. Black holes might be the birthplace of new universes, even new dimen - sions. Black holes might mark the begin ning and end of time. Some consider them to be pos si ble time travel machines as well as a way to travel faster than the speed of light. Many believe that black holes could be the ulti mate future energy source, provid ing power sta- tions throughout the galaxy. Cer tainly, black holes were first a the o ret i cal, and then a prac ti cal, great mys tery of as - tronomy in the twenti eth century. Their discov ery led science a giant step closer to under - standing the universe around us and provided a solid confir ma tion of Einstein’s theory of relativity.

How Was It Discov ered?

How Was It Discov ered? A black hole is not re ally a hole at all. It is a col lapsed star that crushed in on itself. As the star con denses, its grav ity increases. If the collapsed star’s gravity becomes so strong that not even light (parti cles travel ing at light speed) can escape the gravi tational pull, then it will appear like a black hole (in the pitch black back ground of space). Two men get the credit for the discov ery of these bizarre and unsee able phenom ena. The first was Ger man as trono mer wonder-boy, Karl Schwarzschild. As a child, Schwarzschild was fas cinated by celes tial mechan ics (the mo tion of the stars), and he published his first two papers on the theory of how double stars move when he was only 16 (in 1889). In 1900, Schwarzschild pre sented a lec ture to the Ger man as tro nom i cal so ci ety in which he the o rized that space did not act like a regu lar three-dimen sional box. It warped in strange ways, pulled and pushed by gravity. Schwarzschild called it “the curva ture of space.” Five years later, Einstein published his en ergy equation and his the ory of rela tiv ity, which also talked of the curva ture of space. In 1916, while serving in the German army on the Russian front during World War I, Schwarzschild was the first to solve Einstein’s equations for general rel ativ ity. He found that, as a star collapsed into a single point of unimag in- 140 More to Explore 141

ably dense matter, its gravi ta tional pull would increase so that a parti cle would have to be trav el ing faster and faster to es cape from that grav ity (called the es cape ve loc ity). Schwarzschild’s calcu la tions showed that as a massive star collapsed to a single point of in- finitely dense mat ter, its escape veloc ity would exceed the speed of light. Noth ing would escape such a collapsed star. It would be as if the star disappeared and no longer existed in our universe. With these calcu la tions, Schwarzschild had discov ered the concept of a black hole. The terms we now use to de scribe a black hole (event ho ri zon, es cape ve loc ity, etc) were all cre ated by Schwarzschild in 1916. Schwarzschild math emat i cally “dis cov ered” black holes, but he didn’t believe they phys ically existed. He thought it was only a mathe mat ical exercise. Fifty years later, astron o mers began to seri ously search for Schwarzschild’s invis i ble col lapsed stars. As trono mers re al ized that, since a black hole could n’t ac tu ally be seen, the only way to detect one was to track un explained motion of the stars that they could see and show that that motion was the result of the grav ita tional pull of a nearby, unsee able black hole. (Astron o mer John Wheeler coined the name “black hole” in 1970.) In 1971, calcu la tions by Wheeler’s team confirmed that the X-ray bi nary star, Cygnus X-1, was a star cir cling a black hole. That was the first time a black hole had ever been phys - i cally de tected. It wasn’t until 2004 that a black hole was identi fied in the Milky Way galaxy, by Pro- fessor Phil Charles of the Univer sity of Southampton and Mark Wagner of the Univer sity of Ari zona, this one located 6,000 light years away from Earth in our galaxy’s halo. But it was Karl Schwarzschild in 1916 who discov ered what black holes “looked like” and how to locate one.

Fun Facts: Dis covered in Jan u ary 2000, the closest black hole is only 1,600 light years from Earth and is known as V4641 Sgr. Such normal black holes are sev eral times the mass of the sun. But supermassive black holes re side in the hearts of gal ax ies and can be as mas sive as several hun dred million times the mass of the sun.

More to Ex plore

More to Explore Asimov, Isaac. Black Holes, Pulsars, and Quasars . New York: Gareth Stevens, 2003. Da vis, Amanda. Black Holes. Minne ap o lis, MN: Powerkids Press, 2003. Jefferies, Daivd. Black Holes. New York: Crabtree Publish ing, 2006. Nardo, Don. Black Holes. New York: Thomson Gale, 2003. Rau, Dana. Black Holes. Mankato, MN: Capstone Press, 2005. Sipiera, Paul. Black Holes. New York: Scholas tic Library, 1997. Insu lin

INSULIN INSULIN Year of Dis cov ery: 1921

What Is It? Insu lin is a hormone produced by the pancreas that allows the body to pull sugar from blood and burn it to pro duce en ergy. Who Dis cov ered It? Fred er ick Banting

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Fred er ick Banting dis cov ered a way to re move and use the pan cre atic “juice” of an i - mals to save the lives of dia betic humans. This hormone is called insu lin. Its discov ery has saved millions of human lives. Dia be tes used to be a death sentence. There was no known way to replace the function of a pancreas that had stopped produc ing insu lin. Banting’s discovery changed all that. Although insu lin is not a cure for dia be tes, this discov ery turned the death sentence of dia be tes into a manage able malady with which millions of people live healthy and normal lives.

How Was It Discov ered?

How Was It Discov ered? In early 1921, 28-year-old Ca na dian or tho pe dic sur geon Fred er ick Banting de vel oped a theory—ac tu ally, it was more of a vague idea—for a way to help people suffer ing from diabetes. The outer cells of the pancreas produced strong diges tive juices. But the inner cells produced a deli cate hormone that flowed straight into the blood. Muscles got their energy from sugars in the bloodstream, which came from food. But the body couldn’t pull sugar out of the blood stream without that hormone from the inner cells of the pancreas. When the inner cells of a person’s pancreas stopped making that hormone, their muscles could n’t draw sugar from the bloodstream, and the bloodstream be came over loaded with sugar and struggled to get rid of it through excess urina tion. The body dehy drated; and the patient became deathly ill. This con di tion was called diabetes. In 1920 there was no cure for di abe tes. It was always fatal. Research ers had tried obtain ing the pan cre atic hormone (which they re ferred to as “juice”) from ani mals. But when a pancreas was ground up, the diges tive juices from the outer cells were so strong that they de stroyed the deli cate juice from the inner cells before it could be used. Banting read an ar ti cle by Dr. Mo ses Barron that described the fate of sev eral pa tients in whom a block age had devel oped in the ducts car rying pancre atic outer cell di gestive 142 More to Explore 143

juices to the stomach. These strong acids had been trapped in the outer cells of the pancreas and had de stroyed those cells. The cells liter ally shut down and dried up. Banting wondered if he could inten tion ally kill the outer pancre atic cells of an ani mal and then harvest its in ner cell juice for use by dia betic humans. His plan was simple enough. Oper ate to tie off the ducts from a dog’s pancre atic outer cells to the stomach, wait the eight weeks Dr. Barron had mentioned in his arti cle, and hope that the outer cells had dried up and died. Finally, in a second oper a tion, he would harvest the dog’s pancreas and see if it still contained life-giving inner cells and their pre cious juice. He would ar ti fi cially cre ate di abe tes in another dog s and see if the pan cre atic fluid from the first dog could keep it alive. With no funding, Banting talked his way into the use of a lab and six test dogs. The surgery was simple enough. Now he had to wait eight weeks for the outer cells to die. However, early in week six the dia betic dog slid into a coma. This was the last stage before death. Banting couldn’t wait any longer. He oper ated on one of the other dogs, suc- cessfully remov ing its pancreas. He ground up this tissue and extracted the juice by dissolv - ing it in a chloride solution. He injected a small amount of this juice into the dia betic dog. Within 30 minutes the dog awakened from its coma. Within two hours it was back on its feet. In five hours it began to slide back down hill. With another injec tion it perked up, with enough energy to bark and wag its tail. Banting was ec static. His hunch had been right! Dr. John Marcum named the juice, “insu lin” dur ing the two years that he and Dr. Banting searched for a way to create this precious juice without harming lab dogs—a feat they even tu ally ac com plished.

Fun Facts: In 1922 a 14-year-old boy suffer ing from type I dia be tes was the first person to be treated with insu lin. He showed rapid improve ment.

More to Ex plore

More to Explore Bankston, John. Freder ick Banting and the Discov ery of Insu lin . Hockessin, DE: Mitch ell Lane, 2001. Bliss, Michael. Dis cov ery of In su lin. Chicago: Univer sity of Chicago Press, 1994. Fox, Ruth. Mile stones in Med i cine. New York: Random House, 1995. Li, Alison. J. B. Collip and the Evolu tion of Medi cal Research in Canada. To ronto: McGill-Queens Univer sity Press, 2003. Mayer, Ann. Sir Fred er ick Banting. Monroe, WI: The Cre ative Co., 1994. Stottler, J. Fred er ick Banting. New York: Ad dison-Wes ley, 1996. Neurotransmitters

NEUROTRANSMITTERS NEUROTRANSMITTERS Year of Dis cov ery: 1921

What Is It? Chem i cal sub stances that trans mit nerve im pulses be tween in di vid ual neu ron fi bers. Who Dis cov ered It? Otto Loewi

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Like crack ing the ge netic code, like the creation of the atomic bomb, the discov ery of how the brain’s sys tem of neurons commu ni cates is one of the funda men tal science devel - op ments of the twen tieth century. Nerves signal sensa tions to the brain; the brain flashes back commands to muscles and organs through nerves. But how? Otto Loewi’s dis covery of neurotransmitters (the chem i- cals that make this com mu ni ca tion pos si ble) rev o lu tion ized the way sci en tists think about the brain and even what it means to be human. Neurotransmitters control memory, learning, thinking, behav ior, sleep, movement, and all sensory functions. This discov ery was one of the keys to under stand ing brain function and brain organization.

How Was It Discov ered?

How Was It Discov ered? In 1888 German anato mist Heinrich Walder-Hartz was the first to propose that the ner- vous sys tem was a sep arate network of cells. He named these nerve fibers neu rons. He concluded that the ends of indi vid ual nerve cells approached each other closely, but didn’t actu ally touch. In 1893 Italian scien tist Camillo Colgi used a new method for staining cells that brought out excep tion ally fine de tail un der a micro scope and proved that Walder-Hartz was correct. Walder-Hartz’s dis cov ery, how ever, cre ated a sci en tific con tro versy. If neu rons didn’t actu ally touch, how did they commu ni cate? Some scien tists argued that signals had to be sent elec tri cally, since elec tri cal cur rents existed in the brain. Some ar gued that nerve signals had to be sent chem i cally since there were no solid elec tri cal connec tions be tween indi - vidual neu rons. Neither side could prove its position. Otto Loewi was born in Frankfurt, Germany, in 1873. He wanted to become an art his- torian but buckled under family pressure and agreed to attend medi cal school. After barely passing his medi cal exam i na tion, Loewi worked in the City Hospi tal in Frankfurt. How- ever, he be came depressed by the count less deaths and great suffer ing of tuber cu lo sis and pneumo nia pa tients left to die in crowded hospi tal wards because there was no therapy for them. 144 More to Explore 145

Loewi quit medi cal prac tice and turned to pharma co log i cal research (the study of drugs and their effects on human or gans). Over the next 25 years (1895 to 1920) he studied how differ ent human organs responded to electri cal and chemi cal stimuli. His papers reported on many human or gans in cluding the kid ney, pancreas, liver, and brain. By 1920 Loewi was focus ing much of his atten tion on nerves. He was convinced that chem i cals car ried sig nals from one nerve fi ber to the next. But, like other re search ers, he couldn’t prove it. Loewi later said that the an swer came to him in a dream. It was the night be fore Easter Sunday, 1921. Loewi woke up with a start around midnight and scribbled notes about the dream’s idea. The next morning he was unable to read his scrawled notes. Nor could he re - mem ber what the dream had been about. All he could re mem ber was that the notes and the dream were crit i cal. The next night he awoke at 3:00 A.M. from the same dream, re member ing it clearly. He didn’t dare go back to sleep. He rose and drove to his lab, where he performed the simple ex- peri ment from his dream—an exper i ment that has become famous. Loewi surgi cally removed the still-beating hearts from two frogs and placed each in its own container of saline (salt) solu tion. He left the auto nomic nerve (the Vagus nerve) at - tached to heart number one, but not to the second heart. When he applied a tiny electri cal current to heart number 1’s Vagus nerve, the heart slowed down. When he then allowed some saline solu tion from container 1 to flow into container 2, the second heart slowed down to match the slower rate of the first heart. Elec tric ity could not have affected the sec ond heart. It had to be some chem i cal re - leased into the saline solu tion by heart 1’s Vagus nerve that then commu ni cated with and controlled heart 2. Loewi had proved that nerve cells commu ni cate with chemi cals. Loewi called this chemi cal vagusstoff. A friend of Loewi’s, English man Henry Dale, was the first to isolate and decode this chem i cal’s struc ture, which we now call ace tyl cho line. Dale coined the name neurotransmitters for this group of chemi cals that nerves use for com muni ca tion.

Fun Facts: The longest nerve cell in your body, the sciatic nerve, runs from your lower spine to your foot, roughly two to three feet in length!

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More to Explore Adler, Robert. Med i cal Firsts. New York: John Wiley & Sons, 2004. Lanzoni, Susan. A Lot of Nerve. New York: Thomson Gale, 2006. Mas ters, Roger, ed. The Neu ro trans mit ter Rev o lu tion. Cairo: Southern Il linois Uni- versity Press, 1996. Valenstein, Elliot. The War of the Soups and the Sparks: The Discov ery of Neurotransmitters and the Dispute Over How Nerves Commu ni cate . New York: Co lum bia Uni ver sity Press, 2005. Web ster, Roy. Neurotransmitters, Drugs and Brain Function. New York: John Wiley & Sons, 2001. Hu man Evo lu tion

HUMAN EVOLUTION HUMAN EVOLUTION Year of Dis cov ery: 1924

What Is It? Human oids evolved first in Africa and, as Darwin had postu lated, devel oped from the family of apes. Who Dis cov ered It? Raymond Dart

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Humans have always wondered how we came to be on this planet. Vir tually ev ery culture and reli gion has created myths to explain the creation of humans. In the early twenti eth century, most scien tists believed that the first humans appeared in Asia or Eastern Europe. Then Dart discov ered the Taung skull and provided the first solid evi dence both of an Afri - can evolu tion of the first human oids and a fossil link between humans and apes, substan ti at - ing one part of Darwin’s theo ries. This discov ery re directed all of human evo lution ary research and theory and has served as a corner stone of science’s mod ern beliefs about the history and origin of our species.

How Was It Discov ered?

How Was It Discov ered? Raymond Dart was born in Queensland, Austra lia, in 1893 on a bush farm where his family was struggling to raise cattle. He excelled in school and received scholar ships to study medi cine, spe cializ ing in neural anatomy (the anatomy of skull and brain). In 1920 he gained a presti gious po sition as assis tant to Grafton Elliot Smith at the Uni versity of Man chester, England. But their rela tion ship soured and, in 1922, shortly af ter his thir tieth birthday, Dart was sent off to be a profes sor of anatomy at the newly formed Univer sity of Witwatersrand in Johan nes burg, South Africa. Dart arrived feel ing bitterly betrayed and outcast. In 1924 Dart learned of several fossil baboon skulls that had been found at a nearby lime stone quarry at Taung. Dart asked that they be sent to him along with any other fossils found at the site. He did not an tici pate finding anything par ticu larly inter est ing in these fossils, but the new univer sity’s ana tom i cal museum desper ately needed anything it could get. The first two boxes of fossil bones were deliv ered to Dart’s house one Satur day after - noon in early Septem ber 1924, just as he was dressing for a wedding recep tion to be held at his house later that after noon. He almost set the boxes aside. But curi os ity made him open them there in his driveway. The first box con tained nothing of particular interest. However, on top of the heap of rock inside the second box lay what he instantly recog - nized as undoubt edly a cast or mold of the inte rior of a skull—a fossil ized brain (rare enough in and of itself). Dart knew at first glance that this was no ordi nary an thropoid (ape) 146 More to Explore 147

brain. It was three times the size of a baboon’s brain and consid er ably larger than even an adult chimpanzee’s. The brain’s shape was also differ ent from that of any ape Dart had studied. The forebrain had grown large and bulging, completely cover ing the hindbrain. It was closer to a human brain and yet, certainly, not fully human. It had to be a link between ape and human. Dart fever ishly searched through the box for a skull to match this brain so that he could put a face on this creature. Luckily he found a large stone with a depres sion into which the brain cast fit perfectly. He stood transfixed in the driveway with the brain cast and skull-contain ing rock in his hands, so long that he was late for the wedding. He spent the next three months pa tiently chipping away the rock matrix that covered the actual skull, us ing his wife’s sharpened knitting nee dles. Two days before Christ mas, a child’s face emerged, complete with a full set of milk teeth and per manent mo lars still in the process of erupting. The Taung skull and brain were that of an early humanlike child. Dart quickly wrote an arti cle for Na ture maga zine describ ing his discov ery of the early human oid and showed how the structure of the skull and spinal cord connec tion clearly showed that the child had walked up right. Dart claimed to have dis covered the “missing link” that showed how hu mans evolved in the Afri can plain from apes. The scien tific commu nity were neither impressed with Dart’s descrip tion nor con vinced. All Eu ro pean sci en tists re mained skep ti cal un til well-re spected Scots man Rob ert Broom discovered a second Afri can skull in 1938 that supported and substan tiated Dart’s discov ery.

Fun Facts: Dar win be lieved that human oids emerged in Africa. No one believed him for 50 years, until Dart uncov ered his famed skull in 1924.

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More to Explore Avi-Yonah, Michael. Dig This! Denver, CO: Runestone Press, 1993. Gundling, Tom. First in Line: Trac ing Our Ape Ances try. New Ha ven, CT: Yale Uni - versity Press, 2005. Leakey, Mary. Dis clos ing the Past. New York: McGraw-Hill, 1996. Leroi-Gourhan, Andre. The Hunt ers of Pre history. New York: Atheneum, 2000. McIntosh, Jane. The Prac ti cal Ar chae ol o gist. New York: Facts on File, 1999. Phillipson, Da vid W. Af ri can Ar chae ol ogy. Cam bridge: Cam bridge Uni ver sity Press, 2001. Scheller, William. Amaz ing Ar chae ol o gists and Their Finds. New York: Atheneum, 1994. Tan ner, Nancy Makepeace. On Be com ing Hu man. Cam bridge: Cam bridge Uni ver sity Press, 2001. Tat ter sall, I. The Fossil Trail: How We Know What We Think We Know About Human Evo lu tion. New York: Ox ford Uni versity Press, 1995. Trinkaus, E. The Neanderthals: Changing the Image of Mankind . New York: Al fred A. Knopf, 1992. Wheel house, Fran ces. Dart: Scien tist and Man of Grit. Hornsby, Austra lia: Transpareon Press, 2001. Quan tum The ory

QUANTUM THEORY QUANTUM THEORY Year of Dis cov ery: 1925

What Is It? A math e mat i cal sys tem that ac cu rately de scribes the be hav ior of the sub atomic world. Who Dis cov ered It? Max Born

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? (Max 150 words) In the first 20 years of the twen tieth century, phys ics buzzed with the incred ible discovery of the subatomic world. Long before micro scopes were power ful enough to allow research ers to see an atom, scien tists used math emat ics to probe into the sub atomic world of electrons, protons, and alpha and beta particles. Al bert Ein stein, Werner Heisenberg, Max Planck, Paul Dirac, and other famed re - searchers posed theo ries to explain this bizarre new terri tory. But it was quiet, unas sum ing Max Born who dis cov ered a uni fied quan tum the ory that sys tem at i cally, math e mat i cally described the subatomic world. Max Born’s gift to the world was a brand-new field of study we call “quantum mechanics” that is the basis of all modern atomic and nuclear physics and solid state mechan - ics. It is because of Max Born that we are now able to quanti ta tively describe the world of sub atomic par ti cles.

How Was It Discov ered?

How Was It Discov ered? Einstein published his gen eral theory of rela tiv ity in 1905. So, for the last year and a half of his univer sity study, 25-year-old Göttingen Uni versity mathe mat ics student Max Born lived in a world abuzz with the wonder, impli ca tions, and poten tial of Einstein’s bold and rev o lu tion ary theory. Bitterly frustrated that he couldn’t find a postgrad u ate po sition that would allow him to continue his studies of the subatomic world, Born returned home to live in his childhood room. Working alone for two years at the desk he used for homework as a boy, he tried to ap ply his math e mat i cal teach ings to the prob lems of sub atomic rel a tiv ity as de scribed in Einstein’s theory. Through this work, Max Born discov ered a simpli fied and more accu rate method of calcu lat ing the minuscule mass of an electron. Born wrote a paper on his findings that gener ated an offer for a full-time posi tion at Göttingen Uni versity. Two weeks after he started, the job evapo rated. Born limped back

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home for another full year of inde pend ent study and a sec ond paper, a review of the mathe - mat i cal im pli ca tions of Ein stein’s rel a tiv ity, be fore he was of fered a lec tur ing po si tion at Göttingen University. However, the only available research fund ing was des ignated for the study of the vibra - tional energy in crystals. Deeply disap pointed, feeling excluded from the grand hunt for the structure of the atom, Born launched his study of crystals. For five years Born and two assis - tants collected, grew, sliced into paper-thin wedges, studied, measured, and ana lyzed crystals. In 1915 Born shifted to the Univer sity of Berlin to work with physics giant Max Planck. Planck and Einstein were at the hub of the race to unravel and under stand the sub - atomic world. Born brought his math e mat i cal su pe ri or ity and his un der stand ing of crys tals to aid their efforts. It was a classic case of finally be ing in the right place at the right time with the right background. Theo ries abounded to explain the pecu liar behav ior of sub atomic parti cles. But no one was able to write down the mathe mat ics that proved and described those theo ries. The prob - lem had mys tified the greatest minds in the scien tific world for almost 20 years. It occurred to Born that the quantum phe nomena phys icists found so troubling in electrons looked remark ably simi lar to the behav ior of the crystals he had studied for five years. In 1916 Born started to apply what he had learned with crystals to the immense and complex numer i cal problem that surrounded subatomic parti cles. The work stretched the available mathe mat ical tools to their limits. The effort extended over nine years of work on black boards, on note pads, and with slide rules. In 1925 Born completed work on “Zur Quantenmechanik,” or “On Quantum Me chanics.” The phrase had never been used before. The pa per exploded across the sci entific world. It clearly, mathe mat i cally, laid out the fun damen tals that Einstein, Planck, Dirac, Niels Bohr, Hermann Minkow ski, Heisenberg, and others had talked about. It concretely explained and described the amazing world of subatomic particles. “Quan tum mechan ics” became the name of the new field of study that fo cused on a quan ti ta tive de scrip tion of sub atomic phe nom ena. Max Born be came its founder.

Fun Facts: In the bizarre quantum world, many of our “normal” laws do not apply. There, objects (like elec trons) can be (and regu larly are) in two differ - ent places at once without upset ting any of the laws of quantum ex istence.

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More to Explore Baggott, Jim. The Meaning of Quantum Theory . New York: Oxford Univer sity Press, 1998. Born, Max. Phys ics in My Gen er a tion. London: Cambridge Univer sity Press, 1996. Clive, Barbara. The Question ers: Physi cists and the Quantum Theory . New York: Thomas Crowell, 1995. Gribbin, John. In Search of Schrodinger’s Cat: Quantum Physics and Real ity . New York: Bantam Books, 1984. Keller, Alex. The Infancy of Atomic Physics . Oxford: Claren don Press, 1993. Tanor, Joseph, ed. McGraw-Hill Modern Men of Science . New York: McGraw-Hill, 1986. Wasson, Tyler, ed. Nobel Prize Winners . New York: H. W. Wil son, 1987. Ex pand ing Uni verse

Ex pand ing Uni verse EXPANDING UNIVERSE Year of Dis cov ery: 1926

What Is It? The universe is expand ing. The millions of galax ies move ever outward, away from its center. Who Dis cov ered It? Edwin Hub ble

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Hubble’s twin discov er ies (that there are many galax ies in the universe—not just the Milky Way—and that all of those galax ies are travel ing outward, expand ing the uni verse) rank as the most im por tant as tro nom i cal dis cov er ies of the twen ti eth cen tury. These dis cov - eries radi cally changed science’s view of the cosmos and of our place in it. Hubble’s work also rep re sents the first ac cu rate as sess ment of the movement of stars and galaxies. The dis covery that the uni verse is expand ing and ever changing for the first time allowed sci entists to ponder the universe’s past. This discov ery led directly to the discov ery of the Big Bang and the ori gin of the universe as well as to a new concept of time and of the future of the universe.

How Was It Discov ered?

How Was It Discov ered? In 1923 Edwin Hubble was a tall, broad-shouldered, power ful astron o mer of 33 who, 10 years earlier, had almost chosen a career as a profes sional boxer over astron omy. Hubble had been hired in 1920 to complete and oper ate the Mt. Wilson Obser va tory’s mammoth 100-inch tele scope in Cali for nia—the largest telescope in the world. In the early twenti eth century, the universe was thought to contain one galaxy—the Milky Way—plus scat tered stars and nebu lae drifting around its edges. Hubble de cided to use the giant 100-inch telescope to study several of these neb u lae and picked Andromeda as his first target—and he made the two most im portant astro nom i cal discov er ies of the twentieth century. This giant telescope’s power showed Hubble that Andromeda wasn’t a cloud of gas (as had been thought). It was a dense cluster of millions of sepa rate stars! It looked more like a sep a rate galaxy. Then Hub ble located sev eral Ceph eid stars in Andromeda. Cepheid stars pulse. The beat of their pulse is always a direct measure of the abso lute amount of light given off by the star. By measur ing their pulse rate and their ap par ent amount of light, scien tists can deter - mine the ex act dis tance to the star.

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Andromeda lay 900,000 light-years away. That proved that Andromeda was a sepa rate galaxy. It lay too far away to be a fringe part of the Milky Way. Within six months, Hubble had studied and measured 18 other nebu lae. They were all sepa rate galax ies, ranging from five to 100 million light-years from Earth. Astron o mers were shocked to learn that the universe was so big and that it likely contained thousands of sep a rate galaxies. But Hubble was just begin ning. He had noticed a consis tent red shift when studying the light emitted from these distant neb u lae. Sci en tists had dis cov ered that each el e ment (he lium, hy dro gen, ar gon, ox y gen, etc.) al ways emit ted en ergy in a char ac ter is tic set of spe cific fre quen cies that iden ti fied the el e- ment’s pres ence. If they made a spec tro graph (a chart of the en ergy ra di ated at each sep a rate frequency) of the light being emitted from a star, the lines on the spectro graph would tell them which el e ments were pres ent in the star and in what relative quantities. Hubble found all the common spectro graph lines for helium, hy drogen, and so forth that were normally found in a star. But all the lines on his graph were at slightly lower frequen cies than nor mal. It was called a red shift be cause when vis i ble light fre quen cies are lowered, their color shifts toward red. If their frequency is raised, their color shifts toward blue (a blue shift). Over the next two years, Edwin Hubble conducted exhaus tive tests of the 20 galax ies he had identi fied. He found that ev ery one (except Andromeda) was moving away from Earth. More startling, the gal axies moved away from us and away from each other. Ev ery galaxy he studied was speeding straight out into open space at speeds of between 800 and 50,000 ki lo me ters per second! The universe was expand ing, grow ing larger ev ery second as the gal axies raced outward. It was not a static thing that had re mained unchanged since the begin ning of time. In each moment the universe is differ ent than it has ever been before.

Fun Facts: Because the universe is expand ing, every galaxy in exis tence is mov ing away from our own Milky Way—except for one. Andromeda, our nearest neighbor, is moving on a colli sion course with the Milky Way. Don’t worry, though: the col lision won’t occur for several mil lion years.

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More to Explore Barrow, John. The Or igin of the Universe . New York: Basic Books, 1994. Burns, Ruth Ann. Stephen Hawking’s Universe (video). New York: WNET, 1997. Haven, Kendall, and Donna Clark. 100 Most Popu lar Scien tists for Young Adults. Englewood, CO: Librar ies Unlim ited, 1999. Munitz, Mil ton, ed. Theo ries of the Universe: From Baby lo nian Myths to Modern Sci- ence. New York: Free Press, 2001. Rees, Martin. “Explor ing Our Universe and Others.” Sci en tific Amer i can 281, no. 6 (De cem ber 1999): 78–83. 152 Ex pand ing Uni verse

Sandage, Alan. The Hubble At las of Galax ies. Wash ing ton, DC: Car ne gie In sti tu tion of Wash ing ton, 1994. Sharov, Alex an der S., and Igor D. Novikov. Edwin Hubble: The Discov erer of the Big Bang Universe. New York: Cambridge Univer sity Press, 1993. Wil son, Rob ert. Astron omy through the Ages. Princeton, NJ: Princeton Univer sity Press, 1998. Uncer tainty Princi ple

Un cer tainty Prin ci ple UNCERTAINTY PRINCIPLE Year of Dis cov ery: 1927

What Is It? It is impos si ble to know the posi tion and mo tion of an ele men tary par ti cle (e.g., an elec tron) at the same time. Who Dis cov ered It? Werner Heisenberg

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Werner Heisenberg is famed worldwide for discov er ing the Uncer tainty Princi ple, which states that it is impos si ble to de termine both the posi tion and mo mentum (motion) of an el e men tary par ti cle at the same time since the ef fort to de ter mine ei ther would change the other in unpre dict able ways. This pivotal theo rem marked a funda men tal turning point in science. For the first time it was no longer possi ble to precisely and completely measure or observe the world. At a certain point, Heisenberg showed, scien tists had to step back and take the mathe mat ical equations describing the world on faith. The Heisenberg Uncer tainty Princi ple also under mined the posi tion of cause and effect as a most basic and unas sail able founda tion block of scien tific research, a po sition it had enjoyed for over 2,500 years. Aat an ele men tary parti cle level, every cause had only a fixed prob abil ity of creat ing an anticipated effect.

How Was It Discov ered?

How Was It Discov ered? Opening the mail in his Helgoland, Ger many, home, in the fall of 1926, Werner Heisenberg found a letter from famed physi cist Max Planck. The letter glowed with praise for Heisenberg’s paper pre sent ing the “matrix mechan ics” Heisenberg had devel oped. It was Heisenberg’s fifth con gratu latory letter from a famed physi cist that week. Every letter hailed Heisenberg’s matrix mechan ics and talked about its “vast poten - tial.” They called it “new and ex cit ing” and “ex tremely valu able.” But Werner Heisenberg’s deep sense of unease was not re lieved by these let ters. Bur - ied in his ma trix equations, Heisenberg had de tected what he thought was a hard limit to science. If true, it would be the first time science had been told it was impos si ble to be more precise. A deep dread rumbled the founda tions of Heisenberg’s scien tific beliefs. Yet there it was in black and white. If he was right, sci ence had reached an unscalable wall. The great phys ics de bate at that time cen tered on the im age of an atom. Was it a ball of protons surrounded by shells of parti cle electrons, as Niels Bohr claimed, or were electrons really waves of energy flowing around the central nucleus, as others proposed? It occurred to Heisenberg to forget specu la tion and begin with what was known—that when electrons 153 154 Un cer tainty Prin ci ple

(what ever they were) be came ex cited, they re leased quanta of en ergy at spe cific char ac ter - istic frequen cies. Heisenberg decided to develop equations to describe and predict the end result, the spectral lines of this radiated energy. He turned to matrix analy sis to help him derive equations with terms such as fre - quency, po si tion, and mo men tum along with pre cise ways to math e mat i cally ma nip u late them. The result ing equa tions, while yielding good results, seemed strange and unwieldy. Uncer tain of their value, Heisenberg almost burned the final paper. Instead he sent a copy to someone he had studied with and trusted, Wolfgang Pauli. Pauli instantly recog nized the value of Heisenberg’s work and notified other physicists. Heisenberg’s dis cov ery, called ma trix mechan ics, gained him instant fame. But Heisenberg was deeply bothered by what happened when he completed his matrix calcu la - tions. Heisenberg noticed that, because of the matrix na ture of the calcu la tions, the value of a par ticle’s posi tion could affect the value he had to use for its mo mentum (the parti cle’s motion), and vice versa. While dealing with im preci sion was not new, it was new to real ize that the better he knew one term, the more it would add impre ci sion to an other. The better he knew po sition, the less he knew about momen tum. The more pre cisely he could de termine momen tum, the less he would know about position. Heisenberg had acci den tally discov ered the prin ciple of uncer tainty. In one sweep ing discov ery he destroyed the notion of a completely deter min is tic world. Hard limits sud - denly ex isted on sci ence’s ability to measure and observe. For the first time, there were places sci en tists could not go, events they could never see. Cause and effect be came cause and chance-of-effect. At the most funda men tal level the very approach to physi cal science was altered. Research was made instantly more complex, and yet new doors and ave nues to under stand ing and progress were opened. Heisenberg’s Uncer tainty Princi ple has been a guiding foundation of particle research ever since.

Fun Facts: Werner’s best sub jects were math e mat ics, phys ics, and re li - gion, but his record throughout his school career was excel lent all round. In fact his mathe mat i cal abili ties were such that in 1917 (when he was 16) he tutored a fam ily friend who was at the uni versity studying calcu lus.

More to Ex plore

More to Explore Daintith, John, et al., eds. Bio graph i cal En cy clo pe dia of Sci en tists, Sec ond Edi tion, Vol ume 1. Phil a del phia: In sti tute of Phys ics Pub lish ing, 1994. Eggenberger, David, ed. The McGraw-Hill En cy clo pe dia of World Bi og ra phy, Vol- ume 5. New York: McGraw-Hill, 1993. Gillispie, Charles, ed. Dic tio nary of Sci en tific Bi og ra phy, Vol ume XV. New York: Charles Scribner’s Sons, 1998. Hoffman, Banesh. The Strange Story of the Quantum. Cambridge, MA: Harvard Uni- versity Press, 1999. Rensberger, Boyce. How the World Works: A Guide to Science’s Greatest Discov er - ies. New York: William Morrow, 1994. Speed of Light

Speed of Light SPEED OF LIGHT Year of Dis cov ery: 1928

What Is It? The speed at which light travels—a univer sal constant. Who Dis cov ered It? Albert Michelson

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? In the late 1800s dis cover ing the true the speed of light had only minor im portance because as trono mers were the only ones who used this num ber. (Dis tances across space are mea sured in light-years—how far light trav els in one year’s time.) Since their mea sure - ments were only ap proxi ma tions any way, they could accept a 5 per cent (or even 10 percent) error in that value. Then Al bert Ein stein cre ated his famed en ergy-mat ter equation, E = mc2. In stantly the speed of light, “c,” be came crit i cal to a great many cal cu la tions. Dis cov er ing its true value jumped to the high est prior ity. Light speed became one of the two most impor tant con stants in all physics. A 1 percent error, or even a 0.1 percent error, in “c” was suddenly unac cept - ably large. But the problems of discov er ing the true speed of light—a speed faster than any clock could measure or other machines could detect—were enormous. Albert Michelson invented half a dozen new pre cision de vices and, after 50 years of attempts, was the first human to accurately measure light speed. His discov ery earned Michelson the first Nobel Prize to be given to an American physicist.

How Was It Discov ered?

How Was It Discov ered? This was a discov ery that was depend ent on the inven tion of new technol ogy and new equipment—just as Gali leo’s discov ery of moons around other planets was depend ent on the inven tion of the telescope. In 1928, 74-year-old Albert Michelson struggled to make one last try to accu rately mea sure the speed of light and discover the true value of “c” in Einstein’s famed equation. He had designed, financed, and completed a dozen attempts over the previ ous 50 years. Michelson was deter mined this time to measure the speed of light with no more than a 0.001 percent error. That value would finally be accu rate enough to support essen tial nuclear physics calculations. Four years earlier, Michelson had turned to the famed gyro scope manu fac turer, Elmer Sperry, to im prove upon the equipment available for his mea sure ments. Now in 1928, the third, and latest, round of equipment improve ments was repre sented by a small octag o nal 155 156 Speed of Light

cylin der that had just been driven in a thickly padded crate up the bumpy dirt road to the top of Mt. Baldy in Cal i for nia—Michelson’s test site. The ex peri ment Michelson de signed was sim ple. He shone a light onto this small mirrored cylin der as it rotated at a high speed, driven by a motor (also invented by Sperry) ca- pable of maintain ing an exact speed of rota tion. At some point as the mirror turned, it would be per fectly aligned to reflect this light beam to ward a station ary, curved mirror at the back of the room. However, the rotat ing mirror would only reflect light back to that mirror for a very small fraction of a second before it rotated on. This back wall mirror thus got short pulses of light from each face of the rotat ing mirror. Each pulse reflected through a focus ing lens and out through an opening in the wall 22 miles to Mt. San Anto nio. There it bounced off a mirror, through a second focus ing lens, and straight back to Mt. Baldy. Here the light pulse once again hit the back wall mirror, and finally reflected back to the rotat ing cylinder. Even though each pulse of light would complete this 44-mile journey in less than 1/4000 of a second, the ro tating cylin der would have already turned some by the time that light pulse got back from Mt. San Anto nio. Re turning light would reflect off the rotat ing mirror and hit a spot on the shed wall. The angle from the cylin der to that spot would tell Michelson how far the mirror had ro tated while a pulse of light made the 44-mile round-trip. That would tell him how fast the light had traveled. While it all sounded sim ple, it meant years of work to improve the neces sary equipment. Sperry cre ated a better light so that it would last through 44 miles of travel. He created a more ac curate motor drive so that Michelson would always know ex actly how fast the small cyl inder was turning. Sperry designed smoother focus ing lenses and a better mirrored cylin der—one that wouldn’t vibrate or distort its mirrored sides un der the tremen dous forces of high-speed rotation. Michelson switched on the motor and light. Faster than eyes could see, the light stream shot out to Mt. San Anto nio and back. It bounced off the ro tating cylin der and onto the far wall. From the cylin der’s rota tional speed and the placement of that mark on the wall, Michelson calcu lated the speed of light to be 186,284 miles per second—less than 2 mph off of the modern esti mate—an error of less than 0.001 percent. With this dis covery, scien - tists in the fields of physics, nuclear physics, and high-energy physics were able to proceed with the calcu la tions that led to nuclear en ergy and nuclear weapons.

Fun Facts: Travel ing at light speed, your ship could go from New York to Los Angeles 70 times in less than one second. In that same one second you could make seven and a half trips around the earth at the equa tor.

More to Ex plore

More to Explore Daintith, John, et al., eds. Bio graph i cal En cy clo pe dia of Sci en tists, Sec ond Edi tion, Vol ume 1. Phil a del phia: In sti tute of Phys ics Pub lish ing, 1994. Garraty, John, ed. En cy clo pe dia of Amer i can Bi og ra phy. New York: Harper & Row, 2000. More to Explore 157 Peni cil lin

PENICILLI N PENICILLI N Year of Dis cov ery: 1928

What Is It? The first com mer cially avail able an ti bi otic drug. Who Dis cov ered It? Al ex an der Flem ing

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Peni cil lin has saved millions of lives—tens of thousands during the last years of World War II alone. The first anti bi otic to success fully fight bac terial infec tions and disease, pen i- cil lin was called a mir acle cure for a dozen killer dis eases ram pant in the early twentieth century. Peni cil lin created a whole new arse nal of drugs in doc tors’ toolkits to fight disease and infec tion. It opened the door to en tire new fami lies and new gener a tions of anti bi otic drugs. Peni cil lin started the vast indus try of anti bi otic drugs and ushered in a new era of medicine.

How Was It Discov ered?

How Was It Discov ered? In 1928, 47-year-old Scottish born Alex an der Fleming was named chief biochem ist at St. Mary’s Hospi tal in London and given a basement labo ra tory tucked in next to the boiler room. As the staff bacte ri ol o gist, he grew (or “cultured”) bac teria in small, round, glass plates for hos pital study and ex peri ment. Using micro scopic amounts of a bacte rium (often collected from a sick pa tient), he grew enough of each to de termine why the patient was sick and how best to fight the infec tion. Small dishes of deadly staphy lo cocci, strepto cocci, and pneumococci bac te ria were lined and la beled across the one lab bench that stretched the length of Fleming’s lab. Molds were the one great haz ard to Flem ing’s lab oper a tion. Fleming’s lab al ternated between being drafty and stuffy, depend ing on the weather and how hard the boiler worked next door. His only venti la tion was a pair of windows that opened at ground level to the parklike gar dens of the hos pital. After noon breezes blew leaves, dust, and a great va riety of airborne molds through those windows. It seemed impos si ble to keep molds from drifting into, and contam inat ing, most of the bacteria Fleming tried to grow. On Septem ber 28, 1928, Fleming’s heart sank as he real ized that a prized dish of pure (and deadly) staphy lo cocci bacte ria had been ruined by a strange, green mold. The mold must have floated into the dish sometime early the previ ous eve ning and had been multi ply - ing since then. Greenish mold fuzz now covered half the dish.

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Flem ing grunted and sighed. Then he froze. Where this strange green mold had grown, the staphy lo cocci bacte ria had simply disap peared. Even bacte ria more than an inch from the mold had turned transpar ent and sickly. What kind of mold could destroy one of the most hearty, tena cious, and deadly bacte ria on earth? No other substance then known to man could attack staphy lo cocci so success fully. It took two weeks for Fleming to isolate and culture enough of the tough green mold to com plete an iden ti fi ca tion: Penicillium notatum. Within a month he had dis covered that the mold secreted a sub stance that killed bacte ria. He began to call this sub stance “penicillin.” Through cul ture dish ex per i ments he dis cov ered that pen i cil lin could eas ily de stroy all the com mon hu man-kill ing bac te ria—staph y lo cocci, strep to cocci, pneumococci, even the toughest of all, the ba cilli of diphthe ria. The only bacte rium peni cil lin fought but did not destroy was the weak, sen si tive bac te rium that caused influenza (flu). Fleming spent six months testing peni cil lin on rabbits to estab lish that the drug was safe for human use before, in late 1929, announc ing the discov ery of his mira cle mold that had drifted in the window. However, peni cil lin was diffi cult and slow to grow. It worked wonders but was available in such small quanti ties that it did lit tle practi cal good. In 1942 Dor o thy Hodgkin, a British researcher, devel oped a new process, called X-ray crystalography, to deci pher the structure of a peni cil lin mole cule. It took her 15 months and thousands of X-ray images of the mole cules in a peni cil lin crystal to iden tify each of the 35 at oms in a peni cil lin mol ecule. Dr. Hodg kin was awarded the 1964 Nobel Prize for her work. Ameri can doc tors Howard Florey and Ernst Chain were able to use Hodgkin’s map to syn thet i cally pro duce pen i cil lin mol e cules in mass pro duc tion be gin ning in 1943. For their effort, Florey and Chain were awarded the 1945 Nobel Price in Medi cine jointly with Alex - ander Fleming, the discoverer of penicillin.

Fun Facts: Amer i can re search ers in Peoria, Il li nois, were able to de - velop com mer cial pro duc tion of pen i cil lin first, be cause two of pen i cil- lin’s favor ite foods turned out to be a strain of local Illi nois corn and rotting can taloupes, donated by a Peoria market. Those food bases helped research ers increase their produc tion of pen icil lin from 400 million to over 650 bil lion units a month

More to Ex plore

More to Explore Bankston, John. Alex an der Fleming and the Story of Peni cil lin . Hockessin, DE: Mitch ell Lane, 2001. Birch, Beverly. Al ex an der Flem ing: Pi o neer with An ti bi ot ics. New York: Thomson Gale, 2002. Hantula, Rich ard. Al ex an der Flem ing. New York: Gareth Stevens, 2003. Parker, Steve. Al ex an der Flem ing. Portsmouth, NH: Heinemann, 2001. Snedden, Robert. Sci en tists and Dis cov er ies. Portsmouth, NH: Heinemann, 2001. Tocci, Salvatori. Al ex an der Flem ing: The Man Who Dis cov ered Pen i cil lin. Berkeley Heights, NJ: Enslow, 2002. Anti mat ter

An ti mat ter ANTIMATTER Year of Dis cov ery: 1929

What Is It? An ti mat ter are par ti cles of the same mass and com po si tion as pro - tons and electrons, but with an oppo site electri cal charge. Who Dis cov ered It? Paul Dirac

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Sci ence fic tion space ships are reg u larly pow ered by an ti mat ter drives. Fu tur is tic bombs are de signed around an timat ter. Yet neither you nor anyone you’ve ever met has even once seen a parti cle of anti mat ter. Anti mat ter does not come in fist-sized chunks, but as stray, indi vid ual subatomic particles. Paul Dirac is con sidered by many to be the greatest Brit ish the o reti cal physi cist since New ton. Dirac was the first to predict the nec essary exis tence of pos itrons and antiprotons, or anti mat ter. The concept of anti mat ter pro vided a new av enue of re search and under stand - ing in phys ics. Dirac’s an ti mat ter dis cov ery has be come the the o ret i cal frame work for modern parti cle physics. Modern cosmol o gists and physi cists are able to ex tend and apply the precepts of quan tum phys ics, quantum elec trody namics, and quantum mechanics in large part because of Dirac’s discovery.

How Was It Discov ered?

How Was It Discov ered? Shy, re tiring, and secre tive by na ture, 21-year-old Cambridge Univer sity phys ics gradu ate student Paul Dirac had made few friends, but had gained a rep u tation for mathe - mat i cal brilliance. By 1923, the theo ries of rel ativ ity and quan tum mechan ics were well-estab lished, but their limits and the ex act impli ca tions and mean ing were not. Quantum mechan ics, the study of systems so small that Newto nian physics breaks down, was based on the assump - tion that subatomic matter acts both like parti cles and waves. The contra dic tions and para - doxi cal impli ca tions of this assump tion and the mathe mat ics used to try to describe it were drawing physics toward a crisis. Through a series of cun ning re search ef forts and pre cise, ar tic u late pa pers, Dirac be - gan to chip away at these incon sis tencies, bring ing clarity and reason to what had previ - ously seemed to be chaotic uncer tainty. He improved the meth ods to calcu late a par ticle’s speed as de fined by “Edding ton’s equations”. He resolved the dis crep ancies of the covariance of Niels Bohr’s frequency condition.

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Still as a gradu ate student, he published five impor tant papers and turned his focus to the more general problem of uniting quantum mechan ics (the laws govern ing the micro-world of ele men tary parti cles) and rela tiv ity (the laws govern ing the macro-world of plane tary and univer sal gravi ta tion). To this work Dirac brought his en gineer’s ability to accept and use approx i ma tions when exact cal cula tions were not possi ble and where exact mea sure ments did not ex ist. This talent allowed Dirac to ven ture into new areas of analy sis whose lack of exact measurements had stopped previous researchers. Dirac worked mostly in the world of advanced mathe mat ics for these studies. He used the results of a number of lab studies conducted by other research ers to test and verify his equa tions and math e mat i cal models. Through com pletion of his doctoral work and through the first five years of his work as a researcher at Cambridge, Dirac struggled to resolve the appar ent incom pat i bil ity of these two major sys tems of thought and analy sis. By 1929 Dirac had re alized that his calcu la tions re quired that sev eral subatomic par ti cles had to exist that had never been detected or thought of before. In order for the equations that he had devel oped and tested against lab results to work, an entire set of new parti cles had to exist. These new parti cles would mimic the mass and compo si tion of the known parti cles, but would have the opposite electrical charge. Protons and neutrons were known. Dirac concluded that nega tively charged parti cles of equiva lent mass must also exist. The exis tence of this antiproton, or anti mat ter, was confirmed 25 years later. Simi larly, Dirac concluded that if an electron existed, posi tively and neutrally charged parti cles of simi lar mass (posi tron and neutrino respec tively) must also exist. The exis tence of posi trons was con firmed two years later, in 1932. Neu trinos were pos itively identi fied in the mid-1970s, but their mass was not confirmed until work done by Japanese researchers in 1998. Dirac thus dis cov ered the ex is tence of an ti mat ter and proved that the par ti cles we can see, touch, and deal with repre sent only half of the kinds of parti cles that inhabit our universe. In so do ing, Dirac moved science closer to an accu rate view of the physical world.

Fun Facts: When matter converts to energy, some resi due is always left. Only part of the matter can be converted into energy. Not so with anti - matter. When an timat ter collides with matter, 100 per cent of both mat ter and anti mat ter are con verted into usable energy. A gram of anti mat ter would carry as much poten tial energy as 1,000 space shuttle exter nal tanks carry.

More to Ex plore

More to Explore Daintith, John, et al., eds. Bio graph i cal En cy clo pe dia of Sci en tists, Sec ond Edi tion, Vol ume 1. Phil a del phia: In sti tute of Phys ics Pub lish ing, 1994. Devine, Eliz a beth, ed. The An nual Obit u ary, 1983. Chicago: St. James Press, 1990. Dirac, Paul. The Gen eral The ory of Rel a tiv ity. New York: John Wiley & Sons, 1995. ———. The Prin ci ples of Quan tum Me chan ics. Lon don: Cam bridge Uni ver sity Press, 1998. 162 An ti mat ter

Kragh, Helge. Dirac: A Sci en tific Bi og ra phy. New York: Cambridge Univer sity Press, 1996. Pais, Abra ham. Paul Dirac: The Man and His Work. New York: Cambridge Univer - sity Press, 2005. Scheller, Bill. Spaced Out!: An Extreme Reader . . . from Warps and Wormholes to Killer As ter oids. New York: Penguin, 1999. Wasson, Tyler, ed. Nobel Prize Winners . New York: H. W. Wil son, 1987. Neu tron

Neu tron NEUTRON Year of Dis cov ery: 1932

What Is It? A subatomic parti cle located in the nu cleus of an atom with the mass of a proton but no electri cal charge. Who Dis cov ered It? James Chadwick

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The discov ery of neutrons has been hailed as a major landmark of twenti eth-cen tury science. First, this discov ery completed our under stand ing of the structure of atoms. Sec- ond, because they have no electri cal charge, neutrons have been by far the most useful parti - cles for creat ing nuclear colli sions and reac tions and for explor ing the structure and reac tion of atoms. Neutrons were used by Ernest Lawrence at UC Berkeley to discover a dozen new ele ments. Neutrons were essen tial to the creation of nuclear fission and to the atomic bomb.

How Was It Discov ered?

How Was It Discov ered? Since the discov ery that a subatomic world existed (in 1901), only the two electri cally charged par ti cles—pro ton and elec tron—had been dis cov ered. Sci en tists as sumed that these two par ti cles made up the whole mass of every atom. But there was a problem. If atoms were made up of protons and electrons, spin didn’t add up cor rectly. The idea that each sub atomic par ti cle pos sessed a “spin” was dis cov ered in 1925 by George Uhlenbeck and Samuel Goudsmit in Germany. For exam ple, a nitro gen atom has an atomic mass of 14 (a proton has a mass of 1) and its nucleus has a posi tive electri cal charge of +7 (each pro ton has a charge of +1); to balance this pos i tive charge, seven electrons (charge of -1 each) orbit around the nucleus. But somehow, seven addi tional electrons had to exist in side the nucleus to cancel out the pos itive elec trical charge of the other seven protons. Thus, 21 parti cles (14 protons and 7 electrons) should re side in each nitro gen nucleus, each with a spin of either +½ or -½. Because 21 is an odd number of parti cles, no matter how they combined, the total spin of each nitro gen nucleus would have to have a ½ in it. But the measured spin of a nitro gen nucleus was always a whole inte ger. No half. Something was wrong. Er nest Rutherford pro posed that a proton-elec tron must ex ist and that a nitro gen nucleus has seven protons and seven proton-elec trons (for 14 par ticles—an even num ber— and the correct spin total). But it was only theory. He had no idea of how to detect a proton-elec tron since the only known way to de tect a parti cle was to detect its electrical charge. 163 164 Neu tron

Enter James Chadwick. Born in 1891 in England, Chadwick was another of the crop of physi cists who learned their atomic physics un der Rutherford. By the mid-1920s Chadwick was ob sessed with the search for Rutherford’s uncharged proton-elec tron. In 1928 Chadwick began to use beryl lium for his exper i ments. Beryl lium was a small, simple atom with an atomic mass of 9. He bom barded beryl lium with al pha par ticles from polo nium (a radio ac tive ele ment) and hoped that some beryl lium atoms would be struck by al pha par ti cles and burst apart into two new al pha par ti cles (each with a mass of 4). If that happened, these two al pha par ti cles would carry all of the electri cal charge of the origi nal beryl lium nucleus, but not all of its mass. One atomic unit of mass (the mass of a proton) would be left over from beryl lium’s origi nal mass of 9. But that last proton-sized parti cle from the breakup of this beryl lium nucleus would have no electri cal charge. It would therefore have to be the proton-elec tron (now called neu tron) Chadwick sought. If this exper i ment worked, Chadwick would create a stream of neutrons along with alpha parti cles. However, it took three years for Chadwick to find a way to detect the presence of any neu trons he cre ated in this way. He used a strong electri cal field to deflect alpha par ticles (all electri cally charged). Only uncharged par ticles would continue straight along the target path. Happily, Chadwick found that some thing was still smashing into a block of paraf fin wax he placed at the end of the target path. That “some thing” hit the par affin hard enough to break new alpha parti cles loose from the wax. That some thing had to have come from the colli sion of alpha parti cles with beryl lium atoms, had to be at least the size of a proton (to break new al pha par ti cles loose in the par af fin), and could n’t have an electri cal charge since it was n’t de flected by the elec tri cal field. It had to be a neutron. Chadwick had discov ered the neutron. He had proved that they existed. But it was Rutherford, not Chadwick, who named it neu tron for its neu tral elec tri cal charge.

Fun Facts: A neutron has nearly 1,840 times the mass of the electron. How does that size com pare with a proton?

More to Ex plore

More to Explore Adler, Robert. Sci ence Firsts, New York: John Wiley & Sons, 2002. Bortz, Fred. Neu tron. Cherry Hill, NJ: Rosen Publish ing Group, 2004. Brown, Andrew. The Neutron and the Bomb: A Biog ra phy of Sir James Chadwick. New York: Ox ford Uni versity Press, 1997. Bunch, Bryan. The History of Science and Tech nology. New York: Houghton Mifflin, 2004. Garwin, Laura. A Century of Nature: Twenty-One Discov er ies That Changed Science and the World. Chicago: Univer sity of Chicago Press, 2003. Cell Struc ture

Cell Structure CELL STRUCTURE Year of Dis cov ery: 1933

What Is It? The first ac cu rate map of the many in ter nal struc tures that make up a living cell. Who Dis cov ered It? Albert Claude

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Albert Claude was the first scien tist to develop proce dures for isolat ing and studying indi vid ual structures within a cell. He is the one who mapped the inner orga ni za tion and ac- tivity of a cell and its many compo nents. He is rightly called the founder of modern cell biology. Although he never grad u ated from high school, Claude pio neered the use of centri fuge techniques and the electron micro scope for the study of living cells. He discov ered a dozen key com po nents of cells, identi fied the func tion of other cell substruc tures, and laid the groundwork for a whole new field of cellular biology.

How Was It Discov ered?

How Was It Discov ered? Albert Claude received only a third-grade ed u cation before he was forced to quit school and get a mill job. After serving in the Belgian army during World War I, Claude was able to study medi cine in college when the Belgian govern ment allowed any return ing soldier to attend college—even though the Univer sity of Liege was less than eager to accept an il lit er ate country soldier. During his studies, Claude submit ted a lengthy research proposal to the Rockefeller In sti tute for Medi cal Re search in New York. It was ac cepted and Claude im mi grated to America. Claude proposed to study live can cer cells and discover how the disease was transmit - ted. His proposal called for him to sepa rate cells into differ ent compo nents for indi vid ual study, something that had never been tried before. There were no es tablished proce dures or equipment for such an oper a tion. Claude had to scrounge crude equipment from machine and butcher shops. He used commer cial meat grinders to pulver ize samples of chicken cancer ous tumors that he suspended in a liquid me dium. He used a high-speed centri fuge to sepa rate the ground-up cells into their vari ous subparts—heaviest on the bottom, lightest on top. He called the pro ce dure cell frac tion ation. He now had test tubes filled with layers of goo and mud. Since no one had ever sepa - rated cell subparts be fore, it took Claude several years of study and practice to deter mine 165 166 Cell Struc ture

what each isolated layer was and to learn how to success fully isolate the tumor agent from the rest of the cell. Claude’s chem i cal anal y sis showed this agent to be a ri bo nu cleic acid (RNA), a known constit u ent of vi ruses. This was the first ev idence that cancer was caused by a virus. Claude decided to continue using cell fraction ation to study healthy cells. Working full-time in his labo ra tory over the next six years using a centri fuge and a high-powered micro scope, Claude was able to iso late and de scribe the cell nu cleus (the struc ture that houses the chro mo somes), organelles (spe cial ized mi cro scopic struc tures within a cell that act like or gans), mi to chon dria (tiny rod-shaped gran ules where res pi ra tion and en ergy pro duc tion actu ally hap pen), and ribo somes (the sites within cells where proteins are formed). Claude was map ping a new world that had only been guessed at before. Still, his view was limited by the power of his micro scope. In 1942 the Rockefeller Insti tute was able to borrow the only electron micro scope in New York, used by physi cists attempt ing to probe inside an atom. This scope was capa ble of magni fy ing objects one million times their original size. However, the scope also bombarded a sample with a power ful beam of electrons in order to cre ate an im age. Such an elec tron stream de stroyed frag ile liv ing tis sue. Claude spent 18 months devel op ing success ful methods to prepare and protect cell samples to withstand the elec tron micro scope. By mid-1943 Claude had ob tained the first actual images of the in- ternal structure of a cell, images previ ously unthink able. In 1945 Claude published a cata - log of dozens of new cell structures and functions never before identified. The names of the scien tists who broke the barrier of an atom and discov ered what lay inside (e.g., Marie Curie, Max Born, Niels Bohr, Enrico Fermi, and Werner Heisenberg) are well known and revered. Albert Claude single-handedly broke through the barrier of a cell wall to dis cover and docu ment a universe of subparts and ac tivity inside.

Fun Facts: There are more than 250 dif ferent types of cells in your body. yet they all started as, and grew out of, one sin gle cell—the fer til ized egg cell.

More to Ex plore

More to Explore Daintith, John, ed. Biograph i cal Ency clo pe dia of Science. 2d ed. Phila del phia: Thomson Scien tific, 1994. Devine, Eliz a beth, ed. The An nual Obit u ary, 1978. Chicago, St. James Press, 1999. Kordon, Claude. The Language of the Cell. New York: McGraw-Hill, 1992. Rensberger, Boyce. Life Itself: Explor ing the Realm of the Liv ing Cell. New York: Ox- ford Uni versity Press, 1997. Wasson, Tyler, ed. Nobel Prize Winners. New York: H. W. Wil son, 1987. The Func tion of Genes

The Function of Genes THE FUNCTION OF GENES Year of Dis cov ery: 1934

What Is It? Bea dle dis covered how genes per form their vital function. Who Dis cov ered It? George Bea dle

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Genes are strung along chromo somes and contain direc tions for the oper a tion and growth of indi vid ual cells. But how can a mole cule of nucleic acid (a gene) direct an en tire com plex cell to per form in a cer tain way? George Bea dle an swered this crit i cal ques tion and vastly improved our un derstand ing of evolutionary genetics. Bea dle dis cov ered that each gene directs the for mation of a par tic u lar en zyme. En - zymes then swing the cell into action. His discov ery filled a huge gap in scien tists’ under - standing of how DNA blueprints are translated into physi cal cell-building action. Beadle’s groundbreak ing work shifted the focus of the entire field of genet ics research from the qual- i ta tive study of out ward char ac ter is tics (what phys i cal de for mi ties are cre ated by mu tated genes) to the quanti ta tive chemi cal study of genes and their mode of producing enzymes.

How Was It Discov ered?

How Was It Discov ered? George Beadle was sup posed to be a farmer. He was born on a farm outside Wahoo, Nebraska, in 1903. But a college study of the genet ics of hybrid wheat hooked Beadle on the won der of ge net ics. Ge net ics in stantly be came his life long passion. In 1937, at the age of 34, Beadle landed an appoint ment with the genet ics faculty at Stanford Uni versity. Stanford wanted to de velop their study of biochem ical genet ics. The study of ge netics was 80 years old. But biochem ical genet ics, or the molec u lar study of how ge net ics sig nals were cre ated and sent to cells, was still in its in fancy. Bea dle teamed with micro bi ol o gist Ed ward Tatum to try to de termine how genes exercise their controlling influence. In concept their work was simple. In practice it was painstak ingly tedious and demand - ing. They searched for the sim plest life form they could find, choosing the bread mold Neurospora because its simple gene structure had been well docu mented. They grew trays upon trays of colo nies of Neurospora in a common growth me dium. Then Beadle and Tatum bombarded every colony with X-rays, which were known to accel erate genetic mutations. Within 12 hours most colo nies contin ued to grow normally (they were unmutated), a few died (X-rays had destroyed them), and a precious few lived but failed to thrive (gene muta tions now made them unable to grow). 167 168 The Function of Genes

The inter est ing group was this third one because it had un dergone some genetic muta - tion that made it impos si ble for the mold to grow on its own. If Beadle and Tatum could discover exactly what this mutated mold now needed in order to grow, they would learn what its mu tated gene had done on its own before it was damaged. Beadle and Tatum placed indi vid ual spores from one of these colo nies into a thousand differ ent test tubes, each con taining the same stan dard growth me dium. To each tube they added one possi ble substance the origi nal mold had been able to synthe size for itself but that the mutated mold might not be produc ing. Then they waited to see which, if any, would begin to thrive. Only one tube be gan to grow normally—tube 299, the one to which they had added vita min B6. The mu tation to the mold’s gene must have left the mold unable to synthe size vita min B6 and thus unable to grow. That meant that the origi nal gene had produced something that made the cells able to synthe size the vita min on their own. The second step of Beadle and Tatum’s ex peri ment was to search for that something. Beadle found that when he removed, or blocked, certain enzymes the mold stopped growing. He was able to trace these enzymes back to genes and to show that the mutated gene from tube 299 no longer produced that specific enzyme. Through this exper i ment Bea dle dis covered how genes do their job. He proved that genes pro duce en zymes and that en zymes chem i cally di rect cells to act. It was a dis cov ery worthy of a Nobel Prize.

Fun Facts: Humans have be tween 25,000 and 28,000 genes. Differ ent genes direct every aspect of your growth and looks. Some do nothing at all. Called reces sive genes, they patiently wait to be passed on to the next gener a tion, when they might have the chance to become domi nant and con trol some thing.

More to Ex plore

More to Explore Bea dle, George. Language of Life: An Intro duc tion to the Science of Ge netics. New York: Doubleday, 1966. Davern, Cedric. Ge net ics: Read ings from Sci en tific Amer i can. San Francisco: W. H. Free man, 1998. Maitland Edey, and Donald Johanson. BLUEPRINTS: Solving the Mystery of Evolu - tion. New York: Penguin Books, 1996. Moritz, Charles, ed. Cur rent Bi og ra phy Year book, 1990. New York: H.W. Wil son, 1991. Tanor, Joseph, ed. McGraw-Hill Modern Men of Science . New York: McGraw-Hill, 1996. Wasson, Tyler, ed. Nobel Prize Winners. New York: H. W. Wil son, 1987. Eco sys tem

Eco sys tem ECOSYSTEM Year of Dis cov ery: 1935

What Is It? The plants, ani mals, and envi ron ment in a given place are all inter - de pen dent. Who Dis cov ered It? Arthur Tansley

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Many scien tists over the centu ries had studied the rela tion ship of vari ous species to their climate and en viron ment. They studied ele ments of ecology. However, it wasn’t until 1935 that Arthur Tansley real ized that all species in a given en viron ment were inter con - nected. Grasses affected top carni vores and the bugs that decom posed dead ani mals, and fallen trees affected grasses and bushes. Tansley dis covered that ev ery organ ism is part of a closed, inter de pen dent system—an eco sys tem. This dis cov ery was an im por tant de vel op ment in our un der stand ing of bi ol ogy and launched the modern en viron men tal movement and the science of ecology.

How Was It Discov ered?

How Was It Discov ered? Arthur Tansley was the person who saw the big pic ture and discov ered that all el e- ments of a local ecolog i cal system were depend ent upon each other, like indi vid ual threads in a tightly spun web. But he was not the first person to study ecology. Ar is totle and his stu dent, Theophrastus, stud ied the re la tion ships be tween an i mals and their envi ron ment in the fourth century B.C. In 1805, Ger man sci en tist Al ex an der von Humbolt published his studies of the rela tion ship between plant species and climate. He was the first to describe veg e ta tion zones. Alfred Wallace, a com peti tor of Darwin’s, was the first to propose (in 1870) a “geog raphy” of an imal species, re lating ani mals to their climate and ge og raphy. In the early nineteenth century, French scien tist Antoine Lavoisier discov ered the nitro gen cycle. This cycle linked plants, ani mals, wa ter, and at mosphere into a single inter de pen dent cy cle by trac ing how nitro gen cycles through the envi ron ment. What science needed was for someone to rec og nize that all of these in di vid ual pieces fit together like pieces in a jigsaw puzzle. Arthur Tansley was born into a wealthy family in London in 1871. He earned a degree in botany and lectured throughout his working ca reer at Univer sity College in London and then at Cambridge. Tansley was active in promot ing English plant ecology and helped found the Brit ish Eco log i cal Society.

169 170 Eco sys tem

In the late 1920s Tansley conducted a massive plant in ventory of England for the Eco- logi cal Soci ety. During this study, Tansley began to focus not just on the list of plants he set out to create, but on the rela tion ships between this vast list of plants. Which grasses were found with which others? With which bushes and weeds? Which grasses popu lated lowland mead ows? Which were found on craggy mountain sides? And so forth. By 1930 Tansley had real ized that he couldn’t fully ana lyze the re lation ships between plants without consid er ing the effects of ani mals. He began to inven tory and map the many brows ers—ani mals that ate grasses. Soon he real ized that any study of these browser an i- mals was woe fully incom plete un less he in cluded an inven tory of the car nivores that controlled browser populations. Then he real ized that he had to include recyclers and decomposers (organ isms that broke down decay ing plant and ani mal matter into the basic chemi cal nutri ents for plants). Fi nally he added the phys i cal (in or ganic) en vi ron ment (wa ter, pre cip i ta tion, climate, etc.). Tansley had real ized by 1935 that each area he stud ied repre sented an inte grated, en - closed local system that acted as a single unit and included all organ isms in that given area and their rela tion ship to the local inor ganic envi ron ment. It was a breathtak ingly grand concept. Each spe cies was linked to all oth ers. What hap pened to one affected all others. Water, sunlight, and some inor ganic chemi cals entered the system from the outside. All living organ isms inside the closed ecolog i cal system fed off each other, passing food up and then back down the food web. Tansley shortened the name from ecolog i cal system to eco sys tem. That term and that concept, however, did not gain popu lar ity until 1953 when Ameri can scien tist Eugene Odum published Fun da men tals of Ecol ogy, a book that explained the con cept of, and used the term, eco sys tem.

Fun Facts: An impor tant ecosys tem service that most people don’t think about is polli na tion. Ninety percent of the world’s food crops would not exist without pollinators like bees, bats, and wasps.

More to Ex plore

More to Explore Anker, Peder. Impe rial Ecology: Envi ron men tal Order in the British Empire, 1845–1945. Cam bridge, MA: Harvard Univer sity Press, 2002. Ball, Jackie. Ecol ogy. New York: Gareth Stevens, 2003. Dorling Kindersley Staff. Ecol ogy: Eye wit ness. New York: DK Publish ing, 2000. Lane, Brian. Ecol ogy. New York: DK Publish ing, 2005. Stone, Lynn. For ests. Vero Beach, FL: Rourke Publish ing, 2004. Weak and Strong Force

Weak and Strong Force WEAK AND STRONG FORCE Years of Dis covery: 1937 and 1983

What Is It? The last two of the four funda men tal phys ics forces of na ture. Who Dis cov ered It? Carlo Rubbia (weak force) and Hideki Yukawa (strong force)

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? For sev eral cen turies sci entists thought that grav ity and elec tromag netic forces gov- erned the universe. Then twen tieth-cen tury physi cists found atomic nu clei com posed of posi tively charged protons. Why didn’t they fly apart since pos itive elec trical forces re pel each other? Further, why did some atoms natu rally radio ac tively decay while others did not? Many physi cists proposed that two new forces (weak and strong) must exist. In 1935, Hideki Yukawa discov ered the strong force. It was not until 1983 that Carlo Rubbia dis covered the two par ti cles that de fined the weak force. These discov er ies completed our under stand ing of the four forces that govern the microscopic quantum world and di rect whole clus ters of galax ies. The weak and strong forces form the founda tion of quan tum physics.

How Was It Discov ered?

How Was It Discov ered? New ton math e mat i cally de fined grav ity in 1666. Far a day, Oers ted, and Maxwell defined elec tromag ne tism in the early nineteenth cen tury. Scien tists thought that these two forces ruled the universe. However, twenti eth-cen tury physi cists real ized that neither of these forces could hold an atom together. Electro mag netic repul sion of like charges (protons) should rip every atomic nu cleus apart. Why did nu clei and at oms ex ist? Other sci en tists re al ized that some force had to be respon si ble for the de cay of radioactive nuclei. Scien tists theo rized that two new forces had to exist: the strong force (the force that held atomic nu clei together) and the weak force (that cre ated ra dio ac tive de cay). No ev i - dence existed to prove that either force actu ally ex isted. Though many searched, by the late 1930s no one had detected or proved the exis tence of either force. In 1936 Hideki Yukawa reasoned that, since neither the weak nor the strong force had ever been de tected, they must act over a range that was smaller than the diam e ter of an atomic nucleus. (Thus, they would be unde tect able outside of that tiny space.) He began a

171 172 Weak and Strong Force

series of exper i ments in which he smashed protons (hydro gen nuclei) with neutrons to see if the colli sion products would give him a hint about how the strong force worked. Yukawa noticed the consis tent produc tion of large (for subatomic parti cles), short-lived par ti cles called pi-mesons (a kind of gluon) from these col lisions. That meant that pi-mesons ex isted inside the nucleus of atoms since that is where they sprang from. Yukawa proposed that mesons, in general, repre sented the at trac tive force called the strong force. Noting that photons (which repre sented electro mag netic force) and gravitons (which repre sented gravi ta tional force) were both virtu ally massless, he proposed that the greater the mass of these tiny par ti cles, the shorter the dis tance over which they exerted their effects. He proposed that the short-range strong force came about from the exchange of the mas sive me son parti cles between protons and neutrons. Yukawa could describe the mesons he believed repre sented the strong force, but he could not physi cally produce one. In 1947 Lattes, Muirhead, Occhialini, and Powell conducted a high-alti tude exper i - ment, flying photo graphic emulsions at 3,000 meters. These emulsions revealed the pion, which met all the re quire ments of the Yukawa particle. We now know that the pion is a meson, both types of the tiny par ticles called gluons, and that the strong inter ac tion is an exchange of mesons be tween quarks (the sub atomic parti cles that make up protons and neutrons). The weak force proved harder to confirm through ac tual discov ery. It was not until 1983 that Carlo Rubbia, at the Euro pean research center, CERN, first discov ered evi dence to prove the exis tence of the weak force. After complet ing initial work in the 1970s that allowed Rubbia to calcu late the size and other physi cal proper ties of the missing parti cles re- sponsi ble for car rying the weak force, Rubbia and a CERN team set out to find these particles. Rubbia then proposed that the large synchro tron at CERN be modi fied so that beams of ac cel er ated pro tons and antiprotons could be made to collide head-on, releas ing ener - gies great enough for weak boson par ti cles to ma te ri al ize. In 1983 his ex per i ments with the colliding-beam ap pa ra tus iso lated two short-lived parti cles, the W and Z parti cles. Rubbia was able to show that these par ti cles were the car ri ers of the so-called weak force in - volved in the ra dioac tive de cay of atomic nuclei. The four fun da men tal forces of nature (and the parti cles that carry and cre ate each of these forces) had finally been discov ered, to complete the standard model that has carried phys i cists into the twnety-first century.

Fun Facts: Hideki Yukawa was the first Japa nese to win the Nobel prize.

More to Ex plore

More to Explore Cottingham, W. N. An Intro duc tion to Nuclear Physics. New York: Cambridge Uni- versity Press, 2001. Gale Ref er ence Team. Bi og ra phy: Hideki Yukawa (1907–1981). New York: Gale Re - search, 2004. More to Explore 173

Galison, Peter. How Ex per i ments End. Chicago: Univer sity of Chicago Press, 1997. Lilley, J. S. Nu clear Phys ics. New York: John Wiley & Sons, 2001. Taubes, Gary. No bel Dreams: Power, De ceit, and the Ul ti mate Ex per i ment. Se at tle, WA: Microsoft Press, 1996. Watkins, Peter. Story of the W and Z. New York: Cambridge Univer sity Press, 1996. Yukawa, Hideki. Yukawa, 1907–1981. Berlin, PA: Berlin Publish ing, 1997. Me tab o lism

METABOLISM METABOLISM Year of Dis cov ery: 1938

What Is It? Krebs dis cov ered the cir cu lar chain of chem i cal re actions that turns sug ars into energy inside a cell and drives metab o lism. Who Dis cov ered It? Hans Adolf Krebs

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Muscles do the work for your body. You eat food and—somehow—it turns into energy that your muscles burn to move. But how? How does this thing called metab o lism work? The process of metab o lism in human bodies is so impor tant to our under stand ing of human anatomy that three Nobel prizes have been given to people who contrib uted to our un derstand ing of it. The third was given to Hans Adolf Krebs, who finally solved the mystery and discov ered how our bodies metab o lize food into energy. It was one of the great med i cal dis cov er ies of the twentieth century.

How Was It Discov ered?

How Was It Dis cov ered? British physi ol o gist Archibald Hill believed that muscles should produce heat when they con tracted. By 1913, he had devel oped ways to measure changes as small as 3/1000 of a degree. To his surprise he dis covered that, during mus cle contrac tion, no heat was pro - duced nor was any oxygen consumed. Five years later, German Otto Meyerhof discov ered that, during mus cle contrac tion, the chemi cal gly co gen dis ap pears and lac tic acid ap pears. He named this pro cess an aer o- bic, from the Greek words meaning “without oxy gen.” He later discov ered that oxy gen was used in the mus cle cells later to break down lactic acid. Other research ers found that when they added any of four differ ent carbon-based acids to muscle tissue slices, it stimu lated the tissue to absorb oxygen. Even though these discov er ies seemed impor tant, they created as much confu sion about the process of how muscles work as they provided answers. Someone had to make sense of these differ ent, seem ingly confus ing studies. Hans Krebs was born in 1900 in Ger many, the son of a surgeon. He studied chemis try and medi cine and was then hired to conduct research at Cambridge Univer sity. He focused this re search on the chem i cal pro cess of mus cle metabolism. Begin ning in 1937, Krebs studied pigeon liver and breast muscle tissue. He was able to mea sure the amounts of certain groups of acids—some that con tain four carbon atoms each 174 More to Explore 175

and other groups of acids that contain six carbon atoms each—that were created when sugars are ox idized (com bined with oxy gen). He also noted that this process created car bon diox ide, water, and energy. These results were confus ing. What did all these chemi cals have to do with simple me- tabo lism of sugars into energy? Krebs saw citric acid be ing broken down and yet at the same time, cit ric acid was be ing pro duced. The same was true for a num ber of other acids. Slowly Krebs re al ized that the pro cess worked in a cir cle—a cir cle with seven sepa rate chem i cal steps. It started with cit ric acid. Each step pro duced the chemi cals and acids that were needed for the next step in the cy cle. In the last step, cit ric acid was pro duced to start the cy cle all over again. The cycle contin ues endlessly in each of our cells. Along the way, glucose mole cules (sugars) supplied by the blood are consumed. Two waste products were produced by this seven-step cycle: carbon diox ide and free hydro gen atoms. These hydro gen atoms then combine with oxy gen and a form of high-en ergy phos phate to cre ate water and ATP, the chem i cal that stores en ergy for cells just like a battery. Sugar mole cules enter the cycle, and carbon diox ide, water, and ATP to power the cells exit the cycle. By 1938 Krebs had un raveled this amaz ingly com plex and yet amazingly ef fi cient seven-step chem i cal cy cle—spe cif i cally de signed to ac com plish a seem ingly simple task: convert sugars in the blood into energy for muscle cells. Amazingly, each muscle cell in our bod ies cre ates these seven se quen tial re actions, each sparked by a dif fer ent enzyme, every minute of ev ery day. And Hans Krebs discovered how it works.

Fun Facts: The av er age per son’s body could the o ret i cally gen er ate 100 watts of elec tric ity us ing a bio-nano gen er a tor, a nano-scale elec tro chem - ical fuel cell that draws power from blood glucose much the same way the body gen erates energy us ing the Krebs Cycle.

More to Ex plore

More to Explore Bailey, Donna. Energy for Our Bodies . New York: Steck-Vaughn, 1999. Curran, Christina. Meta bolic Processes and Energy Transfers: An Anthol ogy of Cur- rent Though. Cherry Hill, NJ: Rosen Central, 2005. Hew itt, Sally. Full of En ergy. New York: Scholas tic Library Pub lishing, 1998. Holmes, Fred er ick. Hans Krebs: Ar chi tect of In ter me di ary Me tab o lism. New York: Ox ford Uni ver sity Press, 1999. Nichols, Peter. Bi ol ogy of Ox y gen. Jef ferson, NC: McFarland, 1997. Coe la canth

COELACANTH COELACANTH Year of Dis cov ery: 1938

What Is It? A living fish species thought to be extinct for 80 million years. Who Dis cov ered It? J. L. B. Smith

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The scien tific world was shocked in 1938 when a coela canth was dis cov ered. All sci en - tists believed that this fish had been extinct for 80 million years. No fossil or trace of it had been found in more recent strata. This discov ery shattered the belief that the known fossil record repre sented a com plete and ac cu rate re cord of the ar rival and ex tinc tion of spe cies on this planet. It confirmed that the deep oceans hold bio logi cal myster ies still untapped and unimag ined. Equally impor tant, the coela canth is a “living fossil.” Unchanged for over 400 million years, this fish is a close rela tive of the fish that, hundreds of millions of years ago, was the first creature to crawl out of the sea onto land—the first amphib ian, the first land creature. Thus, the coela canth is one of our earli est ances tors. This discov ery has been called the most impor tant zoolog i cal find of the twenti eth century, as amazing as stumbling upon a living dinosaur.

How Was It Discov ered?

How Was It Discov ered? In the late 1930s, 32-year-old Margorie Courtenay-Latimer was the cu rator of a tiny museum in the port town of East London on the Indian Ocean side of South Africa. Local fishing boat captain Hendrick Gossen always called her when he returned to port with unusual or inter est ing fish that she might want for her collec tion. Usu ally these finds turned out to be noth ing important. On De cem ber 23, 1938, just be fore Margorie closed the mu seum for her Christmas holi - day, she got a call from Gossen. She almost didn’t go. She wanted to go home to wrap presents. However, she decided to swing quickly by the piers on her way. She climbed onto Gossen’s boat and noticed a blue fin protrud ing from beneath a pile of rays and sharks heaped upon the deck. She had never seen such an iri des cent blue on a fish fin before and she lit er ally gasped. Pushing the overlay ing fish aside re vealed what she described as “the most beauti ful fish I ever saw.” It was five feet long, pale mauve-blue with iri des cent mark ings. She had no idea what the fish was, but knew it was unlike any thing pre viously caught in lo cal waters. Besides the unique color ing, this fish’s fins did not at tach to a skele ton, but to fleshy lobes on the sides of its body as if they could be used to sup port the fish and allow it to crawl. 176 More to Explore 177

Back in her small museum office with the precious fish, she thumbed through refer - ence books and found a picture that led her to a seemingly impos si ble conclu sion. It looked exactly like a pre historic fish that had been ex tinct for 80 million years. She mailed a detailed descrip tion of the fish to profes sor J. L. B. Smith, a chemis try and biol ogy teacher at Rhodes Univer sity, 50 miles south of East London. Unfor tu nately, Smith had al ready left for Christmas vaca tion and did not read her message un til Janu ary 3, 1939. He im medi ately wired back, “IMPORTANT! PRESERVE SKELETON, ORGANS, AND GILLS OF FISH DESCRIBED!” By this time, however, the fish’s innards (includ ing gills) had been thrown away and the fish had been mounted for mu seum display. Smith reached Margorie’s museum on Feb- ru ary 16 and im me di ately con firmed Margorie’s ten ta tive iden ti fi ca tion. The fish was a coela canth (SEE-la-kanth), a fish be lieved to be ex tinct for over 80 million years. The find was impor tant not only because coe lacanths had been thought ex tinct for such a long time, but also because this recent speci men showed that they had remained unchanged for over 400 million years! But Smith needed a second, com plete speci men to be sure. He posted a £100 (British) reward for a complete speci men. Yet none were found. It was a tortu ously long 14 years before, on Decem ber 21, 1952, fishing captain Eric Hunt was handed a complete coela canth by native fisher men on the is land of Comoro, between Zanzibar and Africa. Hunt carried this second complete coela canth to Smith and the discov ery was con - firmed. Smith published the dis covery in his 1956 book on Indian Ocean marine species and rattled the imagi na tion of the world. If an 80-million-year-old creature could lurk unde - tected in oceans, what else swam, hidden, through the depths? World inter est in ma rine science skyrocketed. Since 1956, over 200 coela canths have been caught in the same general area. But it was the vigi lant obser vation of Margorie Courtenay-Latimer and the knowledge of J. L. B. Smith that kept this monu mental discov ery from being just another fish dinner.

Fun Facts: The Inter na tional Union for the Conser va tion of Nature and Natu ral Resources recently surveyed 40,177 species. Of that total, 16,119 are now listed as threatened with extinc tion. This includes one in three amphib i ans and a quar ter of the world’s conif er ous trees, as well as one in eight birds and one in four mammals.

More to Ex plore

More to Explore Smith, J. L. B. J. L. B. Smith Insti tute of Ichthy ol ogy: 50 Years of Ichthy ol ogy . London: Cassell, 1994. Thomp son, Keith. Living Fossil: The Story of the Coela canth. New York: W. W. Norton, 2001. Walker, Sally. Mystery Fish: Se crets of the Coela canth. New York: Lerner Group, 2005. Weber, Valerie. Coe la canth. New York: Gareth Stevens, 2005. Wein berg, Samantha. Fish Caught in Time: The Search for the Coela canth. New York: HarperCollins, 2001. Nu clear Fis sion

Nu clear Fis sion NUCLEAR FISSION Year of Dis cov ery: 1939

What Is It? The discov ery of how to split uranium atoms apart and produce vast amounts of en ergy. Who Dis cov ered It? Lise Meitner

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Nuclear fission—the splitting of ura nium atoms to produce en ergy—was one of the great physics advances of the twen tieth century. It answered one of the great physics puzzles of the age and opened the door to the atomic age. This discov ery is the basis for nuclear power and nuclear weapons. For her dis cov er ies, Lise Meitner has been called “the most sig nif i cant woman sci en - tist of this century.” Enrico Fermi deserves credit for many major discov er ies in the field of atomic physics. But Fermi is most famous for creat ing the world’s first self-sustained nu - clear reac tion. Fermi put Meitner’s discov ery to practi cal use and is thus the founding father of nuclear power.

How Was It Discov ered?

How Was It Discov ered? Lise Meitner and Otto Hahn were re search ers at the Kai ser Wil helm In sti tute in Berlin, Ger many. As part of their study of radio ac tive ele ments, Meitner and Hahn had struggled for years to create atoms heavier than uranium (transuranic ele ments). They bombarded uranium atoms with free protons. It seemed ob vious that some would hit the nu cleus and stick, cre ating an ele ment heavier than uranium. But it never worked. They had tested their methods with other heavy metals. Each performed exactly as expected. Ev ery thing worked as Lise’s phys ics equations said it should—until they reached uranium, the heaviest known ele ment. Throughout the 1930s, no one could figure out why the ex peri ment always failed with uranium. There was no physi cal reason why heavier atoms couldn’t exist. But in over 100 tries, it had never worked. Ob viously, something was happen ing in their exper i ments that they did not under stand. They needed a new kind of exper i ment to show them what really hap - pened when they bombarded uranium nuclei with free protons. Finally Otto conceived a plan using nonradioactive barium as a marker to contin u - ously detect and measure the presence of radio ac tive radium. If uranium decayed into ra - dium, the bar ium would detect it.

178 More to Explore 179

Three more months were consumed with prelim i nary tests to es tablish how barium reacted to ra dio ac tive ra dium in the pres ence of ura nium and to remeasure the ex act de cay rates and de cay pat terns of radium. Before they could finish and conduct their ac tual ex peri ment, Lise had to flee to Swe- den to escape the rise of Hitler’s Nazi party. Otto Hahn had to conduct their grand exper i - ment alone. Two weeks af ter Hahn com pleted this test, Lise re ceived a lengthy re port de scrib ing his failure. He bombarded uranium with a concen trated stream of protons. But he didn’t even get radium. He detected only more barium—far more barium than he started with. Be- wildered, he begged Lise to help him figure out what had happened. One week later, Lise took a long snowshoe walk through the early winter snows. A flash image ap peared in her mind of at oms tear ing them selves apart. The pic ture was so vivid, so startling, and so strong that she could almost feel the pulsing atomic nuclei and smell the siz zle of each atom as it ripped itself apart in her imagination. Instantly she knew that she had just been given their answer. Adding extra protons must have made the uranium nuclei unsta ble. They had split apart. One more exper i ment confirmed that, when radio ac tive uranium is bombarded with free protons, each uranium atom split in two, creat ing barium and krypton. In the process immense amounts of energy were released. Meitner had discov ered the process of nuclear fission. Almost four years later, at 2:20 P.M. on Decem ber 2, 1942, Enrico Fermi flipped the switch that raised hundreds of neutron-ab sorbing cad mium control rods out of stacks of graphite blocks laced with several tons of uranium oxide pellets. Fermi had stacked 42,000 graphite blocks in an under ground squash court situ ated under the west bleachers of Stagg’s field, the Uni versity of Chi cago foot ball field. It was the world’s first nuclear re actor—the product of Meitner’s discov ery. The 1945 creation of the atomic bomb was the sec ond appli cation of Meitner’s fission.

Fun Facts: After Lise Meitner’s death, the 109th ele ment on the Pe riodic Chart of El e ments was named af ter her: “meitnerium.”

More to Ex plore

More to Explore Barron, Ra chel. Lise Meitner: Dis cov erer of Nuclear Fis sion. New York, Franklin Watts, 2000. Boorse, Henry, and Lloyd Motz. The Atomic Sci en tist: A Bio graph i cal His tory. New York: John Wiley & Sons, 1989. Grinstein, Louise S., Rose K. Rose, and Mir iam H. Rafailovich. Women in Chemis try and Phys ics: A Biobibliographic Sourcebook. Westport, CT: Greenwood Press, 1993. Kass-Si mon, G., and Pa tri cia Farnes, eds. Women of Science: Righting the Record. Bloomington: In di ana Uni ver sity Press, 1990. McGrayne, Sharon Bertsch. Nobel Prize Women in Science: Their Lives, Struggles, and Mo men tous Dis cov er ies. New York: Carol Publish ing Group, A Birch Lane Press Book, 1993. 180 Nu clear Fis sion

Sime, Ruth Lewis. Lise Meitner: A Life in Physics. Berke ley: Uni ver sity of Cal i for nia Press, 1996. Stille, Darlene R. Ex traor di nary Women Sci en tists. Chicago: Children’s Press, 1995. Wasson, Tyler, ed. Nobel Prize Winners . New York: H. W. Wil son, 1987. Yount, Lisa. Twen ti eth-Cen tury Women Sci en tists. New York: Facts on File, 1996. Blood Plasma

Blood Plasma BLOOD PLASMA Year of Dis cov ery: 1940

What Is It? Plasma is that portion of human blood that remains after red blood cells have been sep a rated out. Who Dis cov ered It? Charles Drew

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Whole blood can be safely stored for only a few days. That had always meant that blood dona tions had to come from local sources and be given at the time of need. Blood couldn’t travel long distances. People with unusual blood types often had to do with out during surgery and suffered accord ingly. Drew discov ered the process of sepa rat ing blood into red blood cells and blood plasma. This discov ery greatly extended the shelf life of stored blood and has saved thousands —and proba bly millions—of lives. Drew’s discov ery made blood banks practi ca ble. His process and discov ery are still used by the Red Cross today for its blood dona tion and storage pro gram.

How Was It Discov ered?

How Was It Discov ered? The idea of blood trans fusions is thousands of years old and was prac ticed by Roman doctors. However, there was a prob lem: many patients died from the transfu sion. No one could under stand why this happened until Karl Landsteiner discov ered the four blood types in 1897 (A, B, O, and AB). By 1930, other research ers had further divided these groups into eight types by identi fy ing the RH factor for each group (e.g.: O+, O-, A+, A-, etc.). With these discov er ies, blood transfu sions became virtu ally 100 percent safe. But now hospi tals had to store eight kinds of blood in order to have whatever supply was needed for surger ies. However, most donated blood had to be thrown away because it spoiled before being used. Some common blood types ran out and pa tients faced grave dan ger when they had to undergo surgery without it. Blood storage became a criti cal problem for surger ies and hospitals in general. Charles Drew was born in mid-summer in 1904 in Washing ton, D.C. An all-Ameri can football player at Amherst Col lege, Drew chose to study med icine rather than play sports. In 1928 Drew was ac cepted into medi cal school at McGill Univer sity in Canada (one of the few univer sity medi cal schools to accept blacks in 1928). There Drew studied under Dr. John Beattie, a visit ing profes sor from England. In 1930 Beattie and Drew began a

181 182 Blood Plasma

study of ways to extend safe blood stor age time from the ex isting lim its of between two and six days. This short shelf life drasti cally limited available blood supplies. Drew gradu ated in 1935 and left the univer sity with little progress having been made. In 1938, he took a research posi tion at Colum bia Univer sity in New York City and contin - ued his blood research. There, he de veloped a centri fuge technique that allowed him to sep- a rate red blood cells from the rest of blood. This “rest” he called blood plasma. He quickly deter mined that red blood cells contain the unique substances that divide blood into the eight blood types. Blood plasma, however, was univer sal. No matching was neces sary. Blood plasma from any donor was com pati ble with any recip i ent. This made plasma espe cially at trac tive for blood supplies. Drew tested plasma and showed that it lasted far longer than whole blood. Next, he showed that red blood cells, sep arated from plasma, also could be stored longer than whole blood. In 1939 Drew dis covered that plasma could be dehy drated, shipped long distances, and then safely rehydrated (recon sti tuted) by adding wa ter just be fore surgery. Sud denly blood donors could be thousands of miles from recipients. In 1940 Drew published his doctorial disser tation. In it he pre sented his sta tisti cal and medi cal evi dence that plasma lasted longer than whole blood and detailed the process of sepa rat ing blood into red blood cells and plasma and the process for de hy drating plasma. It served as a blue print for manag ing the na tional blood supply. In 1941 Drew cre ated the first “bloodmo biles”—trucks equipped with re friger a tors—and started the first blood drive (collected for British airmen and soldiers). Drew had discov ered plasma and how to safely store blood for long transport, and had cre ated a practi cal system of blood banks and bloodmo biles to collect, process, store, and ship blood wherever it was needed. Finally, blood transfu sions were both safe and practical.

Fun Facts: Is all blood red? No. Crabs have blue blood. Their blood con- tains copper instead of iron. Earthworms and leeches have green blood; the green comes from an iron substance called chlorocruorin. Many in- verte brates, such as starfish, have clear or yel lowish blood.

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More to Explore Jackson, Garnet. Charles Drew, Doctor. New York: Modern Curric u lum Press, 1997. Salas, Laura. Charles Drew: Pio neer in Medi cine. Mankato, MN: Capstone Press, 2006. Schraff, Anne. Charles Drew: Pio neer in Med icine. Berkeley Heights, NJ: Enslow, 2003. Shapiro, Miles. Charles Drew: Founder of the Blood Bank. New York: Steck-Vaughn, 1997. Whitehurst, Susan. Dr. Charles Drew: Medi cal Pio neer. Chanhassen, MN: Child’s World, 2001. Semicon duc tor Transis tor

Semi con duc tor Tran sis tor SEMICONDUCTOR TRANSISTOR Year of Dis cov ery: 1947

What Is It? Semicon duc tor mate rial can be turned, momen tarily, into a super - con duc tor. Who Dis cov ered It? John Bardeen

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? John Bardeen won his first Nobel Prize for discov er ing the transis tor effect of semicon duc tor ma te ri als. Most ma te ri als ei ther con duct elec tric flow (con duc tors) or block that flow (in su la tors). But a few ma te ri als some times per mit ted some elec tric flow (semi con duc - tors). Though they had been identi fied by the late 1800s, no one knew the value of semicon - ductors until Bardeen discovered the transistor effect. The tran sis tor has been the back bone of ev ery com put ing, cal cu lat ing, com mu ni cat- ing, and logic electron ics chip and circuit built in the last 50 years. The transis tor revo lu - tionized the worlds of electron ics and made most of the modern pieces of essen tial electronic and comput ing hardware possi ble. There is no area of life or science that has not been deeply affected by this one discovery

How Was It Discov ered?

How Was It Discov ered? John Bardeen was a true child prod igy, skip ping fourth, fifth, and sixth grades and re- ceiving a master’s degree in physics at 21. With a Ph.D. from Harvard, he taught physics at the Univer sity of Minne sota un til, in 1945, he was hired by Bell Labo rato ries, a high-tech com mu ni ca tions and elec tron ics research plant. In the fall of 1947 Bardeen joined forces with William Shockley and Walter Brattain, who were al ready study ing the pos si ble use of semi con duc tor ma te ri als in elec tron ics. Shockley shared the “indus trial dream” of free ing electron ics from the bulki ness, fra gility, heat produc tion, and high power consump tion of the vacuum tube. To allow semicon duc - tors to replace tubes, Shockley had to make semicon duc tor mate rial both am plify and rec - tify electric signals. All of his attempts had failed. Bardeen first stud ied and con firmed that Shockley’s math e mat ics were cor rect and that his approach was consis tent with accepted theory. Shockley’s exper i ments should work. But the results they found using germa nium, a common semicon duc tor, didn’t match the theory. Bardeen guessed that unspec i fied surface inter fer ence on the germa nium must be blocking the electric current. The three men set about testing the responses of semicon duc - tor sur faces to light, heat, cold, liq uids, and the de posit of metal lic films. On wide lab 183 184 Semi con duc tor Tran sis tor

benches they tried to force electric current into the germa nium through liquid metals and then through soldered wire contact points. Most of Novem ber and much of Decem ber 1947 were consumed with these tests. They found that the contact points worked—sort of. A strong current could be forced through the germa nium to a metal base on the other side. But rather than ampli fy ing a signal (mak ing it stronger), it ac tually con sumed energy (made it weaker). Then Bardeen no ticed some thing odd and unex pected. He acci den tally misconnected his elec trical leads, send ing a micro-cur rent to the germa nium con tact point. When a very weak current was trickled through from wire solder point to base, it created a “hole” in the germa nium’s re sis tance to current flow. A weak current con verted the semi conduc tor into a superconductor. Bardeen had to repeat edly demon strate the phenom e non to convince both himself and his team mates that his amaz ing re sults were n’t fluke oc cur rences. Time af ter time the re - sults were the same with any semicon duc tor mate rial they tried: high current, high resis - tance; low current, vir tu ally no resistance. Bardeen named the phenom e non “transfer resis tors,” or transis tors. It provided engi - neers with a way to both rectify a weak signal and boost it to many times its origi nal strength. Transis tors required only 1/50 the space of a vacuum tube and 1/1,000,000 the power and could outper form vacuum tubes. For this dis covery, the three men shared the 1956 Nobel Prize for Physics.

Fun Facts: The first transis tor ra dio, the Regency TR-1, hit the market on Octo ber 18, 1954. It cost $49.95 (the equiva lent of $361 in 2005 dollars!). It wasn’t un til the late 1960s that tran sistor radios be came cheap enough for every one to afford one.

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More to Explore Aaseng, Na than. Amer i can Pro files: Twen ti eth-Cen tury In ven tors. New York: Facts on File, 1991. ———. The Inven tors: Nobel Prizes in Chemis try. Min ne ap o lis, MN: Lerner, 1988. Hoddeson, Lillian. True Genius: The Life and Sci ence of John Bardeen. Wash ing ton, DC: National Acad emy Press, 2005. Olney, Ross. Amazing Transis tor: Key to the Computer Age. New York: Simon & Schuster Children’s, 1998. Phelan, Glen. Flowing Currents: The Quest to Build Tiny Tran sis tors. Wash ing ton, DC: Na tional Geo graphic So ci ety, 2006. Riordan, Michael. Crystal Fire: The Birth of the In forma tion Age. New York: W. W. Norton, 1997. The Big Bang

The Big Ban g THE BIG BANG Year of Dis cov ery: 1948

What Is It? The universe began with the giant explo sion of an infi nitely dense, atom-sized point of mat ter. Who Dis cov ered It? George Gamow

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? The study of our history and or igins is crit ical to under stand ing who we are. That includes the history of humans, of life on our planet, of our planet itself, and of the universe as a whole. But how can anyone study a history that came and went unseen billions of years ago? Gamow’s work repre sents the first se ri ous attempt to cre ate a sci en tific, ra tio nal de- scription of the begin ning of our universe. It was Gamow who named that moment of explo - sive birth the “Big Bang,” a name still used today. Gamow was able to math emat i cally re-create the condi tions of the universe billions of years ago and to describe how those initial condi tions led to the present universe we can see and measure. His discov er ies began scientific study of the ancient past.

How Was It Discov ered?

How Was It Discov ered? In 1926 Edwin Hubble discov ered that the universe is expand ing—grow ing larger. That discov ery made scien tists wonder what the universe looked like in the past. Has it always been ex panding? How small did it used to be? Was there some moment when the universe began? What did it look like way back then? Some began to specu late about when and how the universe began. In 1927 Georges Lemaitre proposed that Hubble’s discov ery meant that at some distant point in the past, the entire universe had been com pressed into a single infi nitely dense atom of matter. He called it the “cos mic egg.” By 1930 a few sci entists had attempted to de scribe this “cosmic egg” and how it exploded to create our universe’s ongoing expansion. George Gamow was born in 1904 in Odessa, Ukraine. As a young astron omy student, Gamow was known as much for his practi cal jokes and late-night parties as for his science. Still, by 1934 he had immi grated to America and secured a profes sor ship of theo ret i cal physics at George Wash ington Univer sity in Wash ington, DC. It was there that Gamow first heard of the cosmic egg concept. The problem with this the ory was that there was no science, no data, no numer ical studies to back it up.

185 186 The Big Bang

Gamow decided to use available physics, mathe mat ics, and quantum theory tools to prove whether the universe began as a single immea sur ably dense atom called the cosmic egg. He started with Einstein’s equations on gen eral relativity. In the 1940s Gamow added his own ear lier work, which showed that the sun’s nu clear furnace was driven by the conver sion of hydro gen nuclei into he lium. He used the math e- matics of this model to deter mine what would happen to vari ous atoms in a primor dial fire- ball. He used research from the devel op ment of the atomic bomb and test data on high-energy radi a tion of vari ous nuclei to describe what happened inside a fire of almost infinite temperature. From these sources, he slowly built a model of the cos mic egg’s explo sion and of the chem i cal re ac tions that hap pened in the sec onds there af ter. He called that ex plo sion the “Big Bang” and mathe mat ically showed how, at that moment, the uni verse had been composed primar ily of densely packed neutrons. This allowed him to use available studies showing how neutrons, under extreme heat and pressure, combine into larger nuclei and also sepa rate into protons and electrons, form ing hydrogen and helium as they do. Gamow was able to math emat i cally trace this cos mic ex plosion for ward in time. This de scrip tion in cluded a de tailed, sec ond-by-sec ond pic ture of the fire ball ex plo sion and showed, accord ing to known physics and chemis try laws, how that explo sion resulted in the compo sition and distri bu tion of matter that makes up the present universe. Gamow also showed that the Big Bang would have created a vast surge of energy that spread and cooled as the universe expanded. But this energy would still be “out there” and could be detected as a faint “after glow” or echo of that great explo sion. This echo would show up as a band of noise at 5°K. This cosmic background radi a tion was finally detected in the late 1990s by advanced radio astron o mers, which confirmed Gamow’s Big Bang theory. Using physics, chemis try, and math, Gamow had discov ered the birth of the universe, 15 billion years ago.

Fun Facts: Gamow was an impos ing figure at six feet, three inches and over 225 pounds but was known for his impish practi cal jokes. He was once described as “the only sci en tist in Amer ica with a real sense of hu - mor” by a United Press Inter na tional reporter.

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More to Explore Alpher, Ralph. Gene sis of the Big Bang. New York: Ox ford Uni versity Press, 2001. Barrow, John. The Or igin of the Universe . New York: Basic Books, 1994. Fox, Karen. The Big Bang: What Is It, Where Does It Come From, and Why It Works. New York: John Wiley & Sons, 2002. Gribbin, John. In Search of the Big Bang. London: Heinemann, 1986. Hawking, Stephen. A Brief History of Time. New York: Bantam Books, 1988. Longair, Malcolm. The Or igins of the Uni verse. New York: Cambridge Univer sity Press, 1990. More to Explore 187

Munitz, Mil ton, ed. Theo ries of the Universe: From Baby lo nian Myths to Modern Sci- ence. New York: Free Press, 2001. Rees, Mar tin. Before the Be ginning: Our Universe and Others . Read ing, MA: Addi - son-Wes ley, 1997. Silk, Jo seph. The Big Bang, 3d ed. San Francisco: W. H. Freeman, 2001. Wein berg, Ste ven. The First Three Minutes . New York: Basic Books, 1987. Defi ni tion of Infor ma tion

DEFINITION OF INFORMATION DEFINITION OF INFORMATION Year of Dis cov ery: 1948

What Is It? In for ma tion can both fol low all math e mat i cal and phys i cal laws cre ated to de scribe mat ter and act like phys i cal mat ter. Who Dis cov ered It? Claude Shan non

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Every time you surf the Net, download an arti cle, print from your computer screen, use a cell phone, rent a DVD, or lis ten to a CD, you do so because of Claude Shannon’s dis covery. The whole digi tal revo lution started with Claude Shannon’s dis covery that infor ma tion can be turned into digi tal bits (single blocks) of in forma tion and treated like any physical flow of matter. Shan non made in for ma tion phys i cal. His dis cov ery al lowed phys i cists and en gi neers to switch from an alog to digi tal technol o gies and opened the door to the Infor ma tion Age. His 1948 arti cle describ ing the digi tal nature of infor ma tion has been called the Magna Carta of the Information Age.

How Was It Discov ered?

How Was It Discov ered? Claude Shan non was born in rural Michi gan in 1916 and grew up with a knack for electron ics—turn ing long fences of barbed wire into his private telephone system, and earn- ing money rebuild ing radios. He stud ied for his doc torate in mathe mat ics at the Massa chu - setts Insti tute of Technol ogy (MIT). His profes sors described him as brilliant, but not terri bly seri ous as a student, spending his time design ing rocket-powered Frisbees and juggling machines. However, his 1938 master’s thesis (written as part of his studies) startled the world of physics. In it Shannon described the perfect match be tween electronic switching cir cuits and the math emat ics of nineteenth-cen tury British ge nius George Boole. Shannon showed that a sim ple elec tronic circuit could carry out all of the oper a tions of Boolean sym bolic logic. This was the first time anyone had showed that more than simple mathe mat ics could be em bod ied in elec tronic circuits. This student the sis opened the door to dig ital comput ers, which followed a decade later. After gradu a tion Shannon was hired by Bell Telephone Labo ra to ries in New Jersey. Engi neers there faced a problem: how to stuff more “infor ma tion” into a noisy wire or mi- crowave channel. They gave the job to Claude Shan non, even though he was best known for riding a unicy cle through the lab hallways. 188 More to Explore 189

Shannon bypassed others’ attempts to work with specific kinds of infor ma tion—text, numbers, images, sounds, etc. He also de cided not to work on any sin gle way of transmit - ting infor ma tion—along a wire, sound waves through the air, radio waves, micro waves, etc. Instead, Shan non decided to focus on a question so ba sic, no one had thought to study it: What is infor ma tion? What hap pened when infor ma tion trav eled from sender to receiver? Shannon’s answer was that infor ma tion consumed energy and, upon deliv ery, reduced uncer tainty. In its sim plest form (an atom or a quantum of energy), infor ma tion answered a simple yes/no question. That answer reduced (or elimi nated) uncer tainty. Flip a coin. Will it be heads or tails? You don’t know. You are uncer tain. When it lands, you get infor ma tion: yes or no. It was heads or it wasn’t. Un cer tainty is gone. That’s information. Shannon real ized that he could con vert all infor ma tion into a long string of indi vid ual sim ple yes/no bits of infor ma tion and that elec trical circuits were ideal for process ing and transmit ting this kind of digi tal infor ma tion. In this way, he converted infor ma tion—in any form—into a string of digi tal yeses and nos: ones and zeros. Shannon was then able to apply the laws of physics to infor ma tion streams. He showed that there was a limit to the amount of infor ma tion that could be pushed through any com- muni ca tions channel—just as there was a limit to the amount of wa ter that can be pushed through a hose no matter how great the pressure. He also de rived a math emat ical equation to de scribe the re la tion ship be tween the range of fre quen cies avail able to carry in for mation and the amount of infor ma tion that can be carried. This became what we call “bandwidth.” Shannon’s discov ery made infor ma tion as physi cal and easy to work with as water flowing through a pipe or air pumped through a turbine. In this way, Shannon discov ered what infor ma tion is and opened the door to our modern digital age.

Fun Facts: There are 6,000 new com puter vi ruses re leased every month.

More to Ex plore

More to Explore Adler, Robert. Sci ence Firsts. New York: John Wiley & Sons, 2003. Horgan, John. “Claude Shannon: Unicyclist, Juggler, and Father of Infor ma tion The - ory.” Sci en tific Amer i can 262, no. 1 (1995): 22–22B. Liversidge, Anthony. “Claude Shannon.” OMNI (August 1997): 61. Riordan, Michael. Crystal Fire: The Birth of the In forma tion Age. New York: W. W. Norton, 1997. Shan non, Claude. The Math e mat i cal The ory of Com mu ni ca tion. Ur bana: Uni ver sity of Illi nois Press, 1999. Sloane, N., and Aaron Wyner. Claude Elwood Shannon: Collected Papers. Piscataway, NJ: IEEE Press, 1997. Jumpin’ Genes

JUMPIN’ GENES JUMPIN’ GENES Year of Dis cov ery: 1950

What Is It? Genes are not perma nently fixed on chromo somes, but can jump from po si tion to po si tion. Who Dis cov ered It? Barbara McClintock

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Every researcher in the world accepted that genes were strung along chromo somes in fixed posi tions like pearls on a necklace. Working alone in a small, windswept cornfield at Cold Springs Harbor, Long Is land, Barbara McClintock proved every other genetic sci entist in the world wrong. Carefully studying wild corn, Barbara McClintock found that genes not only can jump, but regu larly do jump from one posi tion to another on a chromo some. She found that a few control ling genes direct these jump ing messen ger genes to shift po sition and turn on, or turn off, the genes next to them in their new location. Barbara McClintock’s work became the building block for a dozen ma jor medi cal and disease-fight ing break throughs. The 1983 No bel Prize Commit tee called Barbara McClintock’s pio neer ing work “one of the two great dis cover ies of our time in genetics.”

How Was It Discov ered?

How Was It Discov ered? With a Ph.D. in genet ics, Barbara McClintock lived in a trim two-room apartment over the bright-green-painted garage of the Carne gie Insti tute’s Cold Spring Harbor Re search Fa cility. A small, slight woman, Barbara stood barely five feet tall and weighed less than 90 pounds. Her face and hands were worn and wrinkled from long expo sure to wind and sun. Cold Spring Har bor is an isolated spot on north eastern Long Island charac ter ized by wind, rolling sand dunes, and wav ing shore grass. Stooping in a small half-acre cornfield tucked between the facil ity’s clus ter of buildings and the choppy waters of the Long Island Sound, Barbara planted corn seeds by hand one-by-one in care fully laid out rows. The year 1950 was Barbara’s sixth year of planting, growing, and studying the genes of these corn plants as they passed from gen era tion to gen era tion. She often felt more like a farmer than a ge net ics re searcher. How Barbara spent her days depended on the season. In summer, most of her time was spent in the cornfield, nurtur ing the plants that would produce her data for the year, weed - ing, checking for pests and disease that could ruin her exper i ments. In the fall she harvested each ear by hand, carefully labeled it, and began her lab analy sis of each gene’s loca tion and 190 More to Explore 191

structure on the chromo somes of each ear. Her lab consisted of one power ful micro scope, chemi cal lab trays, and stacks of journals to record her findings. This work consumed the long hours of winter. In the spring she split her time be tween numer ical anal y sis of the previ ous year’s data and field planning and prep ara tion for the next gener a tion of corn plants. She care fully tracked color muta tions, patterns, and changes year af ter year and dis - covered that genes are not fixed along chromo somes as every one thought. Genes could move. They did move. Some genes seemed able to di rect other genes, tell ing them where to go and when to act. These ge netic direc tors con trolled the movement and ac tion of other genes that jumped posi tions on command and then turned on—or turned off—the genes next to them in their new location. It sounded like scien tific heresy. It contra dicted every ge netics textbook, every ge netics research pa per, and the best minds and most advanced research equipment on Earth. At the end of the 1950 harvest season Barbara debated about releas ing her results and finally decided to wait for one more year’s data. McClintock presented her research at the 1951 national sympo sium on genetic research. Her room had seats for 200. Thirty attended. A few more straggled in dur ing her talk. She was not asked a single question. Those few left in the room when she finished sim - ply stood up and left. As so often happens with radi cally new ideas, Barbara McClintock was simply dismissed by the audi ence with a bored and indif fer ent shrug. She was ignored. They couldn’t un derstand the im plica tions of what she said. Feeling both help less and frustrated, Barbara returned to harvest her cornfield and start her analy sis of the seventh year’s crop. It took another 25 years for the scien tific commu nity to under stand the impor tance of her dis cov ery.

Fun Facts: Barbara McClintock be came the first woman to re ceive an un shared Nobel Prize in Physi ol ogy or Medi cine. When she died in 1992, one of her obitu aries suggested that she might well be ranked as the greatest figure in bi ology in the twenti eth century.

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More to Explore Dash, Joan. The Triumph of Discov ery. New York: Simon & Shuster, 1991. Heiligman, Deborah. Barbara McClintock: Alone in Her Field. New York: W. H. Free man, 1998. Keller, Evelyn. A Feeling for the Or gan ism: The Life and Work of Barbara McClintock. San Francisco: W. H. Freeman, 1993. Maranto, Gina. “At Long Last—A Nobel for a Loner.” Dis cover (Decem ber 1983): 26. Opfell, Olga. The Lady Laure ates: Women Who Have Won the Nobel Prize. Metuchen, NJ: Scare crow Press, 1993. Shields, Barbara. Winners: Women and the Nobel Prize. Min ne ap o lis, MN: Dillon Press, 1999. Fu sion

FUSION FUSION Year of Dis cov ery: 1951

What Is It? The oppo site of fis sion, fu sion fuses two atomic nu clei into one, larger atom, releas ing tre mendous amounts of en ergy. Who Dis cov ered It? Lyman Spitzer

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Fusion en ergy is the power of the sun. It is a virtu ally unlim ited power source that can be created from hy drogen and lithium—com mon el ements in the earth’s crust. Fusion is clean, en viron men tally friendly, and nonpolluting. Fusion was theo rized in the late 1910s and the 1920s. It was math emat ically described in the 1930s. It was finally discov ered (demon strated in the lab) in 1951. Fusion’s technol ogy was turned into the hydro gen bomb shortly thereafter. But fusion has not yet been converted into its promised practi cal real ity. It still works only in the lab. If this discov ery can be converted into a working real ity, it will end energy shortages for thousands of years.

How Was It Discov ered?

How Was It Discov ered? Scien tists had always thought that the sun produced heat and light by actu ally burn ing its own matter through normal combus tion. In the nineteenth century, a few scien tists (most nota bly British Lord Kelvin) argued that the sun could create heat from its own gravi ta - tional collapse—but that such a pro cess could only last for a few million years. Einstein’s famous 1905 equation (E = mc2) allowed scien tists to real ize that even tiny amounts of matter could be turned into tremen dous amounts of en ergy. In 1919 Ameri can as tron o mer Henry Rus sell de scribed the phys ics and math e mat i cal pro cesses that would allow the sun to fuse hydro gen atoms into helium atoms and release vast amounts of energy in the process. The process was called fusion. This theory of how the sun works was confirmed in 1920 by astron o mer Francis Aston’s measure ments. The the ory of fusion existed. But was fusion something that could be practi cally devel - oped on Earth? In 1939 Ger man phys icist Hans Bethe de scribed—in math emat ical detail—the theory of how to create a fusion reac tion on Earth. But there was a problem. Bethe’s equations said that hydro gen atoms had to be raised to a temper a ture of over 100 mil lion degrees C (180 million°F) and had to be squeezed into a small space so that the protons in hydro gen nuclei would collide and fuse into helium nuclei. There was no known mate rial or force that could accomplish such a feat. 192 More to Explore 193

Dr. Lyman Spitzer founded the Princeton Univer sity Plasma Physics Lab in 1948. He soon re alized that the only way to con tain a fusion re action was with a high-energy magnetic field. He surrounded a do nut-shaped tube that con tained hy drogen gas with coils of wire to cre ate a mag netic field that kept hy dro gen at oms trapped while la sers heated them many millions of degrees. But there was a problem. When he looped thousands of loops of wire down through the middle of the donut and up along the out side, it natu rally packed the wires more densely on the in side of the donut than on the out side. That cre ated a stron ger magnetic field on the in - side (center) of the donut-shaped tube than on the outside. Hydro gen atoms were pushed to the outside and flung at near light speed out of the tube. The fusion gener a tor didn’t work. Then Spitzer discov ered a marvel ous remedy. He twisted the donut contain ing his hydrogen gas into a figure eight. As hy drogen sped through this looping tube, it spent part of each lap near the inside of the figure eight and part near the out side and so was kept from being pulled out of the tube by varia tions in the magnetic field In 1951 Spitzer completed work on this first hydro gen plasma fusion gener a tor. He called it a stellarator—since it was like creat ing a star—and fired it for the first time for only a small fraction of a sec ond, still not sure that superheated hydro gen plasma wouldn’t turn into a hy drogen bomb. For one glori ous half-second the donut-shaped mass of gas blazed super nova bright, like a blinding sun burning at 70 million degrees Fahren heit. Unimag in ably bright and hot, the gas became a two-foot diam e ter, seething, explo sively power ful pool of hy drogen plasma. Then it faded to dull purple, and, two seconds af ter it first ignited, turned back to black. For one flicker ing moment, Lyman Spitzer had created a new star—almost. More important, he had discov ered that fu sion was pos sible on Earth.

Fun Facts: As an alter na tive energy source, fusion has many advan - tages, includ ing world wide long-term availabil ity of low-cost fuel, no contri bu tion to acid rain or greenhouse gas emissions, no possi bil ity of a runaway chain reac tion, by-products that are unus able for weapons, and mini mum problems of waste dis posal.

More to Ex plore

More to Explore Fowler, T. The Fusion Quest. New York: Johns Hopkins Uni versity Press, 1997. Heiman, Robin. Fusion: The Search for Endless Energy . London: Cambridge Univer - sity Press, 1990. Peat, F. Cold Fusion. New York: Con tem po rary Books, 1999. Rich ard son, Ha zel. How to Split the Atom. New York: Franklin Watts, 2001. Ori gins of Life

ORIGINS OF LIFE ORIGINS OF LIFE Year of Dis cov ery: 1952

What Is It? The first labo ratory re-cre ation of the process of orig inally creat - ing life on Earth. Who Dis cov ered It? Stan ley Miller

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? One of the greatest myster ies has long been: How did life first form on this planet? Theo ries abound. Bacte ria not natu rally found on Earth have been found in mete or ites recovered in Antarctica. Possi bly life here came from some other planet. For over a hundred years, the most popu lar scien tific theory has been that DNA mole - cules (life) first evolved from amino acids that were somehow sponta ne ously created in the soupy chemi cal mix of the primor dial seas. It was just a theory—al beit a popu lar one—until Stanley Miller re-created the con ditions of the early oceans in his lab and showed that amino acids could, indeed, form from this chemical soup. This was the first labo ra tory evi dence, the first scien tific discov ery, to support the theory that life on Earth evolved natu rally from inor ganic compounds in the oceans. It has been a cor ner stone of bi o log i cal sciences ever since.

How Was It Discov ered?

How Was It Discov ered? By 1950 scien tists had used a va riety of methods to de termine that the earth was 4.6 billion years old. However, the oldest fossil records of even tiny bacte rial cells were no older than 3.5 bil lion years. That meant that Earth had spun through space for over a billion years as a life less planet be fore life sud denly emerged and spread across the globe. How, then, did life start? Most agreed that life had to have emerged from inor ganic chemi cals. While this theory made sense, no one was sure if it could really have happened. Through the late 1940s Harold Urey, a chemist at the Univer sity of Chicago, teamed with astron o mers and cosmol o gists to try to de termine what Earth’s early en viron ment looked like. They deter mined that Earth’s early atmo sphere would chemi cally resem ble the rest of the universe—90 percent hydro gen, 9 percent helium, with the final 1 percent made up of oxy gen, carbon, nitro gen, neon, sulfur, sili con, iron, and argon. Of these helium, argon, and neon don’t re act with other elements to form compounds. Through exper i ments, Urey deter mined that the re main ing ele ments, in their likely compo sition in Earth’s early atmo sphere, would have combined to form water, meth ane, ammo nia, and hydrogen sulfide. 194 More to Explore 195

Enter Stanley Miller. In 1952 this 32-year-old chemist decided to test the prevail ing theory and see if life could be produced from Urey’s mix of chem ical compounds. Miller carefully steril ized long sections of glass tubing, flasks, and beakers. He built what looked like a sprawling erector set of support poles in his lab and clamped flasks, beakers, and connect ing glass tubes to this structure. He filled one large beaker with steril ized water. He filled other flasks with the three gasses Urey had iden ti fied as part of Earth’s early at mo sphere—meth ane, am mo nia, and hy dro gen sul fide. Miller slowly boiled the beaker of water so that water vapor would rise into his en- closed “atmo sphere” of a laby rinth of glass tubes and beakers. There it mixed with the three other gasses in swirling clouds in a beaker labeled “at mosphere.” Miller re al ized he needed an en ergy source to start his life-cre at ing chem i cal re action. Since other scien tists had de termined that the early at mosphere contained almost contin ual roll ing thun der and light ning storms, Miller de cided to create arti fi cial light ning in his atmosphere. He hooked a battery to two electrodes and zapped lightning bolts across the “atmosphere” chamber. A glass pipe led from this chamber and past a cooling coil. Here water vapor recondensed and dripped into a collec tion beaker that was connected to the original water beaker. After one week of contin ual oper a tion of his closed-cy cle atmo sphere, Miller an alyzed the resi due of compounds that had settled in the collec tion beaker of his system. He found that 15 percent of the carbon in his system had now formed into organic compounds. Two percent had formed actual amino acids (the building blocks of proteins and of DNA). In just one short week, Miller had cre ated the build ing blocks of organic life! Vir tually all scien - tists were amazed at how easy it was for Miller to cre ate amino acids—the building blocks of life. In 1953 the structure of the DNA mole cule was finally discov ered. Its struc ture fit well with how Miller’s amino acid mole cules would most likely combine to create longer chains of life. This was another bit of evi dence to support the idea that Stanley Miller had discov - ered of how life on Earth began.

Fun Facts: There are 20 types of amino acids. Eight are “es sen tial amino acids” that the human body cannot make and must therefore obtain from food.

More to Ex plore

More to Explore Davies, Paul. Fifth Mira cle: The Search for the Ori gin and Meaning of Life. New York: Simon & Schuster, 2000. Gal lant, Roy. The Ori gins of Life. New York: Benchmark Books, 2000. Jenkins, Steve. Life on Earth: the Story of Evolu tion. New York: Houghton Mifflin, 2002. MacDougall, J. D. Short History of Planet Earth: Mountains, Mammals, Fire, and Ice. New York: John Wiley & Sons, 1998. Mor gan, Jennifer. From Lava to Life: The Universe Tells Our Earth Story. Ne vada City, CA: Dawn Publi ca tions, 2003. DNA

DNA DNA Year of Dis cov ery: 1953

What Is It? The mo lec u lar structure of, and shape of, the mol ecule that car ries the ge netic in for ma tion for ev ery liv ing or gan ism. Who Dis cov ered It? Fran cis Crick and James Wat son

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Brit ish bio chem ist Francis Crick, and his Amer i can part ner, James Wat son, cre ated the first ac curate model of the mo lec u lar structure of deoxy ribo nu cleic acid, or DNA, the master code to the building and oper a tion of all living organ isms. That discov ery has been called by many “the most signif i cant discovery of the century.” This dis cov ery of the details of the DNA mol ecule’s struc ture allowed med i cal sci en - tists to under stand, and to de velop cures for, many deadly diseases. Millions of lives have been saved. Now DNA evi dence is commonly used in court. This discov ery has also led to the unrav el ing of the human genome and promises to lead to cures for a wide vari ety of other seri ous aliments and birth defects. Crick’s discov er ies relat ing to DNA structure and function reshaped the study of genetics, virtu ally created the field of molec u lar biol ogy, and gave new direc tion to a host of endeav ors in vari ous fields of medicine.

How Was It Discov ered?

How Was It Discov ered? The room looked like a tinker toy party gone berserk, like the playroom of overac tive sec ond-grade boys. Com plex mo biles of wire, colored beads, strips of sheet metal, cardboard cutouts, wooden dowels, and wooden balls dangled from the ceiling like a forest of psyche delic sta lac tites. Construc tion supplies, scissors, and tin snips were strewn about the desks and floor, as were pages of complex equations, stacks of sci entific papers, and photo - graphic sheets of fuzzy X-ray crystallography images. The room was really the second-floor office shared by grad u ate students Francis Crick and James Watson in a 300-year-old build ing on the campus of Cambridge Univer sity. The year was 1953. The mo biles were not the idle toys of students with too much free time. Rather, they were a fran tic ef fort to win the world wide race to un ravel the very core of life and deci pher the shape of the DNA molecule. By 1950 biochem ists had al ready deduced that DNA in a cell’s nucleus carried ge netic infor ma tion. The key mystery was how the huge DNA mole cule repro duces itself to physi -

196 More to Explore 197

cally pass this infor ma tion to a new cell, a new organ ism, and a new gener a tion. To answer that question, someone had to first figure out what this giant DNA molecule looked like. At Cambridge, Crick teamed with Ameri can biol o gist James Watson. The two agreed to pool their efforts to construct a model of the DNA mole cule while they pursued their sep- a rate stud ies and the sis research. By 1951 bits and pieces of infor ma tion about the DNA mole cule were emerging from across the globe. Erwin Chargaff discov ered that a defi nite ratio of nucle o tide sequences could be detected in the DNA bases, suggest ing a paired rela tion ship. Oswald Avery conducted ex per i ments on bac te ria DNA show ing that DNA car ried ge netic in for ma tion. Linus Pauling con cep tu al ized the al pha he lix con fig u ra tion for certain chains of proteins. Crick and Watson at tempted to combine these sepa rate clues into a single phys ical structure. Using bits of wire, colored beads, sheet metal, and cardboard cutouts, Crick and Watson hung possi ble spiral models across their shared office. They correctly surmised that a linking chain of sugar and phos phate formed the backbone of the DNA spiral. They correctly linked base pairs of peptides. Still the model did not fit with available atomic data. Also at Cambridge, but inde pend ent of Crick and Watson’s efforts, Rosa lind Frank lin used X-ray crystal log ra phy to create two-dimen sional images of the DNA mole cule. In mid-Janu ary 1953, Rosa lind had rede signed the X-ray cameras she used. X-ray film from these cameras showed the now-fa mous “X” shape that suggested a he lix shape for the DNA molecule. Tipped off that Franklin had new infor ma tion, Crick stole one of Rosa lind’s X-shaped X-rays. This stolen insight finally put Crick and Watson ahead in the race to solve the structure of DNA. By mid-Feb ruary they had constructed the first com plete physi cal model of a DNA mole cule, using the now-famil iar double helix shape, like two inter twined spiral chains.

Fun Facts: If you straightened each strand of DNA from each cell in your body and lined them end-to-end, you’d have about nine million ki- lome ters of DNA. That’s enough to reach to the moon and back 13 times!

More to Ex plore

More to Explore Crick, Fran cis. Life Itself: Its Ori gins and Nature. New York: Simon & Schuster, 1981. ———. Of Mole cules and Men. Wash ing ton, DC: Wash ing ton Uni ver sity Press, 1966. Judson, Horace. The Eighth Day of Creation: Makers of the Revo lu tion in Biol ogy. London: S & S Trade Books, 1999. Maitland, Edey, and Donald Johanson. BLUEPRINTS: Solving the Mystery of Evolu - tion. New York: Penguin Books, 1996. More, Ruth. The Coil of Life: The Story of the Great Discov er ies of the Life Sciences. New York: Knopf, 1991. 198 DNA

Olby, Robert. The Path to the Double Helix. Se at tle: Uni ver sity of Wash ing ton Press, 1994. Sayre, Anne. Ros a lind Frank lin and DNA. New York: Norton, 1991. Stille, Darlene R. Ex traor di nary Women Sci en tists. Chicago: Children’s Press, 1995. Ulf, Lagerkvist. DNA Pio neers and Their Leg acy. New Ha ven, CT: Yale Uni ver sity Press, 1998. Wat son, James. The Double Helix: A Personal Account of the Discov ery of the Struc- ture of DNA. New York: Atheneum, 1985. Seafloor Spreading

Seafloor Spreading SEAFLOOR SPREADING Year of Dis cov ery: 1957

What Is It? The ocean floors slowly move, spread ing from central rifts, and carry the con tinents on their backs as they do. Who Dis cov ered It? Harry Hess

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? We now know that Earth’s conti nents move. Over hundreds of millions of years, they drift across Earth’s surface. You have likely seen pictures of what Earth looked like 500 million years ago. But just 60 years ago, no one be lieved that it was possi ble for mas sive conti nents to move. There was no force great enough to move vast conti nents weigh ing tril - lions of tons. Then Harry Hess discov ered the theory of ocean-floor spreading. That discov ery sud - denly not only made conti nen tal movement plausi ble, but made drifting conti nents a fact. Hess’s discov ery was the key ev idence that con firmed early the o ries on conti nen tal drift by Wegener. Hess’s work launched the study of plate tec tonics and created new under stand ing of the history and mechan ics of Earth’s crust and started the seri ous study of the past motion of Earth’s continents.

How Was It Discov ered?

How Was It Discov ered? Standing on the bridge of a mammoth deep-ocean drilling ship in the mid-Atlan tic in 1957, Navy Commander Harry Hess watched as a crane oper a tor maneu vered the drilling pipe sections from atop the drilling derrick mounted high above the deck. This was the first time a ship had been able to drill and col lect core sam ples from the ocean floor 13,000 feet below. Hess had designed and man aged the oper a tion. He should have been pleased and proud. But test after test showed the ocean bottom below them was less than 50 million years old—disprov ing every the ory about the ocean floor that Harry Hess had created and promoted. A geol ogy profes sor be fore he joined the navy, Hess had been given command of the trans port U.S.S. Cape John son op erat ing in the Pacific in 1945. Using Navy sonar systems, Hess made the first system atic echo-sounding surveys of the Pacific Ocean floor over a two-year pe riod as he steamed back and forth on navy as signments. He discov ered over 100 submerged, flat-topped seamounts 3,000 to 6,000 feet un der water be tween the Hawai ian and Mariana is lands. Hess de scribed these seamounts as “drowned an cient is lands” and named them guyots (to honor Arnold Guyot, a geology professor at Princeton). 199 200 Seafloor Spreading

Hess theo rized that guyots had origi nally been islands dating back to 800 million years ago, a period before coral existed. His argu ment rested, in part, on his hypoth e sis that con - tinual de posits of sedi ment on the seafloor had made the sea level rise. When, in 1956, fossils only 100 million years old were found in guyots, Hess changed his the ory to say that guyots had origi nally been volca noes that had eroded to flat tops by wave action. He abandoned this theory when erosion rate calcu la tions showed that the guyots couldn’t have eroded enough to reach their current depth. Then his 1957 oceanic core sam ples showed that the At lantic Ocean floor was much younger than the conti nents and that oceanic sedi men ta tion rates were slower than previ - ously thought. Hess—again—had to search for a new theory. Luckily, his 1957 survey al lowed him to collect core sam ples from more than 20 sites across the At lantic. These tests showed that the age of the ocean bot tom grew pro gres sively older as it moved away from the mid-oce anic ridge and toward either continent. The seafloor wasn’t fixed and motion less as every one had thought. It had to be spread - ing, moving as if on a gi ant con veyor belt, inch ing year by year away from the mid-oce anic ridge. Hess argued that magma rose from the earth’s mantle up through oceanic rifts and spread out lat er ally across the ocean floor. As the magma cooled, it formed new oce anic crust. He es ti mated the oce anic crust to be spreading apart along the mid-oce anic ridge by one to two inches a year. Hess’s discov ery be came known as seafloor spreading and was the founda tion of the plate tec tonics revo lution in the late 1960s and early 1970s.

Fun Facts: The Pacific Ocean is slowly shrinking as the Amer i cas slide west. Two hundred million years ago, the Atlan tic Ocean didn’t ex ist. South Amer ica and Af rica were joined, as were North America and Eu - rope. The At lantic is still spread ing and grow ing. So is the Red Sea. In 150 million years, that currently skinny sea will be as wide as the Atlan tic is now.

More to Ex plore

More to Explore Bermen, Howard, ed. The Na tional Cyclopedia of Amer i can Bi og ra phy, Vol ume N-63. Clifton, NJ: James T. White & Co., 1984. Daintith, John, ed. Bio graph i cal En cy clo pe dia of Sci ence. 2d ed. Phil adel phia: Norton Sci en tific, 1994. Gillispie, Charles Coulston, ed. Dic tio nary of Sci en tific Bi og ra phy. New York: Charles Scribner’s Sons, 1998. Hess, Harry. “His tory of the Ocean Bas ins.” In Pet ro log i cal Stud ies, edited by A. Engle and H. James. New York: Harper, 1992. Rubey, William. “Harry Hammond Hess.” In Year book of the Amer i can Philo soph i cal So ci ety (1995). New York: Amer i can Philo soph i cal So ci ety, 1996. The Na ture of the At mo sphere

The Nature of the Atmo sphere THE NATURE OF THE ATMOSPHERE Year of Dis cov ery: 1960

What Is It? The atmo sphere is chaotic and unpre dict able. Who Dis cov ered It? Ed Lorenz

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Ed Lorenz un cov ered a non lin ear, com plex, in ter de pen dent sys tem of equa tions that de scribe the real move ment of the atmo sphere. He showed that at mo spheric models are so depend ent on ini tial and boundary con ditions (starting data supplied to the model) that even seemingly infin i tes i mal changes in them create major changes in the system. In other words, when a butter fly flaps its wings over Beijing, the mod els might well predict that it will change the weather in New York. But ev eryone admitted that just couldn’t happen. Lorenz discov ered not how to make long-range predic tions, but rather the forces that make such predic tions impos si ble. He then devel oped chaos theory—the study of chaotic and un pre dict able sys tems. Sci en tists are dis cov er ing that many nat u ral, bi o log i cal, and en- viron men tal systems are best described and better under stood under chaos theory than through traditional forms of analysis.

How Was It Discov ered?

How Was It Discov ered? Having a computer was enough of a novelty in 1958 to entice many MIT faculty and students to make the trip to Ed Lorenz’s office just to watch the thing work. But excite ment quickly turned to de spair for Lorenz. Lorenz cre ated a set of equations to act as a math emat i cal model of atmo spheric storm movement and behav ior. He noticed that tiny changes in the starting condi tions of the model soon produced enormous changes in the outcome. Tiny starting differ ences always am pli fied over time, rather than damping, or normalizing out. If the actual atmo sphere acted like Lorenz’s models, he had just proved that long-range weather forecast ing was impos si ble since starting condi tions were never known with enough pre cision to prevent chaotic, ampli fied error. It was an unset tling and sinking feeling to trade the excite ment of finding a new re search tool for the despair of proving that your field and work were both inher ently flawed and impossible.

201 202 The Na ture of the At mo sphere

When Ed entered Dartmouth College in 1934, he had long ago made up his mind to be a math ema ti cian. He gradu ated with a bache lor’s de gree in math emat ics in 1938 and en - tered Har vard to con tinue his study of math. With the outbreak of World War II, Lorenz joined the Army Air Corps, who assigned him to attend army mete o rol ogy classes at MIT. He learned to re gard the weather as a com bi na tion of den sity, pres sure, temper ature, three-dimen sional wind ve loci ties, and the atmo sphere’s gaseous, liquid, and solid content. The equations that describe this host of variables define the current weather condi tions. The rates of change in these equa tions de fine the changing weather pattern. What Lorenz was not taught, and only much later discov ered, was that no one knew how to use these nonlin ear dy namic me teo rology equations to actu ally predict weather and that most thought it could not be done. The equations were too complex and required too much initial and boundary data. Lorenz tried to apply the dynamic equa tions to predict the motion of storms. As com- puters were not commonly available in the early 1950s, most of this work was carried out on blackboards and with slide rules and paper and pencil. Each calcu la tion was tediously time-consum ing. Lorenz was never able to reach any meaning ful re sults while hand- cal cu lat ing these equa tions. In 1958 Lorenz obtained that Royal-McBee LGP-30 com puter (about the size of a large desk) to develop his sets of dynamic, nonlin ear model equations. The re sults of those com puter sim u la tions showed that tiny ini tial dif fer ences am pli fied over time, rather than gradu ally nor mal izing out. If the model was right, weather was cha otic and inher ently unpredictable. Several years of atmo spheric testing convinced Lorenz and others in his depart ment that he and his model were correct. The at mo sphere was a cha otic rather than a pre dict able system (such as the sys tem of inter ac tions be tween inor ganic chem icals, or the physi cal pull of gravity). A drive to use a new tool to complete an old project had turned into one of the most profound discov er ies for the science of meteorology. Lorenz will always be known as the person who discov ered the true nature of the atmo - sphere and who thereby discov ered the limits of accu racy of weather fore casting.

Fun Facts: Actor Jeff Goldblum played the role of Ian Malcolm in the Ju ras sic Park mov ies. Malcolm is a mathe ma ti cian who spe cial izes in the study of the chaos theory and refers to himself as a “chaotician.” A central theme of these movies is proving that Malcolm’s chaos theo ries are right.

More to Ex plore

More to Explore Fuller, John. Thor’s Legions. Boston: Ameri can Mete o ro log i cal Soci ety, 1990. Gleick, James. Chaos: Mak ing a New Sci ence. New York: Viking, 1991. Lorenz, Ed. The Es sence of Chaos. Se at tle: Uni ver sity of Wash ing ton Press, 1993. ———. “A Sci en tist by Choice.” In Proceed ings of the Kyoto Prize for 1991. Kyoto, Japan: The Inamori Founda tion, 1991. Parker, Berry. Chaos in the Cos mos. New York: Plenum Press, 1996. Quarks

Quarks QUARKS Year of Dis cov ery: 1962

What Is It? Subatomic parti cles that make up protons and neutrons. Who Dis cov ered It? Murry Gell-Mann

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? First sci en tists iden ti fied plant fi bers, then in di vid ual cells. Then scien tists conceived of atoms and mole cules. In the early twenti eth century, scien tists discov ered electrons and then the ex istence of pro tons and neutrons. In each case, sci entists believed that they had finally discov ered the smallest possi ble parti cle of matter. Each time this be lief proved wrong. The discov ery of quarks (funda men tal parti cles that make up protons and neutrons) in 1962 led science into the bizarre and alien quantum world inside protons and neutrons, a world of mass with no mass and where mass and energy are freely exchanged. This discov ery has taken science one giant step closer to answer ing one of the most basic questions of all: What re ally is mat ter made of? At each new level the an swer and the world grows stranger.

How Was It Discov ered?

How Was It Dis cov ered? As the nineteenth century closed, Marie Curie broke open the atom and proved that it was not the smallest possi ble parti cle of matter. Soon sci entists had iden tified two sub - atomic parti cles: electrons and protons. In 1932 James Chadwick discov ered the neutron. Once again sci entists thought they had uncov ered the smallest particles of all matter. When parti cle accel era tors were invented in the mid-1930s, sci entists could smash neutrons into protons, and protons into heavier nuclei to see what the colli sions would produce. In the 1950s Donald Glaser invented the “bubble chamber.” Subatomic parti cles were accel er ated to near light speed and flung into this low-pressure, hydro gen-gas-filled chamber. When these parti cles struck a proton (a hydro gen nucleus), the proton disin te grated into a host of strange new parti cles. Each of these parti cles left a telltale trail of infin i tesi mally small bubbles as they sped away from the colli sion site. Scien tists could n’t see the parti cles them selves. But they could see the trails of bubbles. Scien tists were both amazed and baffled by the vari ety and number of these tiny tracks on bubble chamber plots (each indi cat ing the tempo rary exis tence of a previ ously unknown par ti cle). They were un able to even guess at what these new sub atomic particles were. Murry Gell-Mann was born in Manhattan in 1929. A true prodigy, he could multi ply large numbers in his head at age three. At seven, he beat twelve-year-olds in spelling bees. By age eight, his in tellec tual abil ity matched that of most college students. Gell-Mann, 203 204 Quarks

however, was bored and restless in school and suffered from acute writer’s block. He rarely finished papers and project descrip tions, even though they were easy for him to complete. Still, he sailed through under grad u ate school at Yale and then drifted through MIT, the Univer sity of Chicago (where he worked for Fermi) and Princeton (where he worked for Oppenheimer). By the age of 24, he had decided to focus on under stand ing the bi zarre parti - cles that showed up on bubble chamber plots. Bubble chamber plots al lowed sci entists to es ti mate the size, elec tri cal charge, di rec tion, and speed of each par ti cle, but not its spe cific identity. By 1958 almost 100 names were in use to iden tify and describe this forest of new particles that had been detected. Gell-Mann decided that he could make sense of these par ti cles if he ap plied a few fun - da men tal con cepts of na ture. He as sumed that na ture was simple and sym met ri cal. He also assumed that, like all other matter and forces in nature, these subproton sized parti cles had to be con ser vative. (Mass, en ergy, and electri cal charge would be conserved—not lost—in all collision reactions.) With these princi ples as his guides, Gell-Mann began to group and to sim plify the reactions that hap pened when a pro ton split apart. He cre ated a new measure that he called strange ness that he took from quantum phys ics. Strangeness mea sured the quan tum state of each par ti cle. Again he as sumed that strange ness would be con served in each reaction. Gell-Mann found that he could build simple patterns of reac tions as par ticles split apart or combined. However, several of these patterns didn’t appear to follow the laws of conser - vation. Then Gell-Mann real ized that he could make all of the reac tions follow simple, con - ser vative laws if protons and neutrons were n’t solid things, but were, in stead, built of three smaller particles. Over the course of two years’ work, Gell-Mann showed that these smaller parti cles had to ex ist in side protons and neutrons. He named them k-works, then kworks for short. Soon af ter ward he read a line by James Joyce that men tioned “three quarks.” Gell-Mann changed the name of his new par ticles to quarks.

Fun Facts: The James Joyce line mentioned above is “Three quarks for Mus ter Mark!” in Finnegan’s Wake. Can you find that quote?

More to Ex plore

More to Explore Apfel, Necia. It’s All Ele men tary: From Atoms to the Quantum World of Quarks, Lep- tons, and Gluons. New York: HarperColllins, 1997. Berger, Melvin. At oms, Mol e cules and Quarks. New York: Penguin Young Readers’ Group, 1996. Bortz, Fred. Quarks. Cherry Hill, NJ: Rosen Publish ing, 2004. Gell-Mann, Murry. The Quark and the Jaguar . New York: Abacus Books, 1995. Kidd, Jerry. Nuclear Power: The Study of Quarks and Sparks. New York: Facts on File, 2006. Schwartz, Da vid. Q Is for Quark: A Science Alpha bet Book. Berke ley, CA: Ten Speed Press, 2001. Qua sars and Pul sars

Quasars and Pulsars QUASARS AND PULSARS Years of Dis covery: 1963 and 1967

What Is It? The dis covery of super-dense, distant objects in space. Who Dis cov ered It? Allan Rex Sandage (quasar) and Antony Hewish and Jocelyn Bell (pulsar)

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Qua sars and pulsars rep re sent a new class of ob jects in space, a new kind of massive, ex traor di narily bright ob ject. Mas sive, ex ceed ingly dense, and pro duc ing pow er ful ra dio and light trans mis sions, quasars and pul sars rad ically expanded and altered sci entists’ view of space and space structures. Quasars are some of the brightest and most distant objects in the universe. Pulsars provide hints of the life path and life expec tancy of stars. Their discov ery led to a greater under - stand ing of the life and death of stars and opened up new fields of study in astron omy, super-dense matter, gravi ta tion, and super-strong magnetic fields.

How Was It Discov ered?

How Was It Discov ered? In the fall of 1960, Ameri can astron o mer Allan Rex Sandage noticed a series of dim ob jects that looked like stars. He cross checked them with a ra dio tele scope to see if they transmit ted radio sig nals as well as dim light. Each of these dim ob jects produced amaz ingly power ful ra dio signals. No known object could do that. Maybe they were n’t really stars—at least not stars like other stars. Sandage called these mystery ob jects quasi-stel lar ra dio sources. Quasi-stellar quickly short ened to qua sar. Sandage stud ied the spec trographic lines of these strange ob jects (lines that identify the chemi cal makeup of a distant star). The lines didn’t match any known chemi cal ele - ments and could not be identi fied. Sandage and Dutch-born Ameri can astron o mer Maarten Schmidt finally real ized that the spectral lines could be iden tified as normal and com mon el ements if they were viewed as spec trograph lines that normally occurred in the ul travi o let range and had been displaced by a tremen dous red shift (Doppler shift) into the visi ble range. (Doppler shifts are changes in the frequency of light or sound caused by the motion of an object.) While that expla na tion solved one mystery, it intro duced another. What could cause such a giant Dopp ler shift? In 1963 they de cided that the only plau sible an swer was dis tance

205 206 Qua sars and Pulsars and that the quasars must be over a billion light years away—the most distant objects ever detected! But now the dim light of the quasars was too bright for a single star at that distance —often 1,000 times as bright as whole galax ies. Sandage and Schmidt proposed that each quasar must really be a dis tant galaxy. How ever, the measured radio signals varied too much (on the order of days and hours) to be a galaxy of sepa rate stars. That indi cated a com- pact mass, not a galaxy. Quasars remained a perplex ing mystery until, in 1967, it was proposed that they were really the mate rial surround ing massive black holes. Quasars instantly became the most interest ing and im portant objects in distant space. That same year (in July 1967) Cambridge Univer sity Astron omy profes sor Antony Hewish completed a 4.5-acre radio antenna field to detect radio frequency transmis sions from the farthest corners of space. This gargan tuan maze of wire would be the most sensi - tive radio fre quency receiver on Earth. The ra dio telescope printed 100 feet of output chart paper each day. Grad u ate assis tant Jocelyn Bell had the job of an alyz ing this chart paper. She com pared the chart’s squig gly lines to the posi tion of known space objects and then compared the known electro mag netic emissions of these bodies to the chart’s squiggles and spikes in order to account for each mark on the chart. Two months after the telescope started up, Bell noticed an unusual, tight-packed pattern of lines that she called a “bit of scruff”—a squiggling pattern she couldn’t explain. She marked it with a question mark and moved on. Four nights later, she saw the same pattern. One month later she found the same pat tern of scruff and recog nized that the antenna was focused on the same small slice of sky. She took the extra time to expand and measure the squiggles. Whatever it was, this radio signal regu larly pulsed every 1 1/3 seconds. No natu ral body in the known universe emitted reg u- lar signals like that. Before Hewish publicly announced their discov ery, Bell found another bit of scruff on chart printouts from a differ ent part of the sky. The pulses of this second signal came 1.2 sec onds apart and at al most the ex act same frequency. Every theo re ti cian at Cambridge was brought in to explain Jocelyn’s scruff. After months of study and cal cula tion the sci ence team concluded that Bell had discov ered super-dense, ro tat ing stars. As tron o mers had math e mat i cally the o rized that when a huge star runs out of nuclear fuel, all matter in the star collapsed inward, creat ing a gigan tic explosion, called a supernova. What remained became a hundred million times denser than ordi nary matter —a neutron star. If the star ro tated, its magnetic and electric fields would broadcast beams of powerful radio waves. From Earth, a rapidly rotat ing neutron star would appear to pulse and so these were named “pulsars.”

Fun Facts: The more dis tant the quasar is, the red der its light appears on Earth. The light from the most dis tant qua sar known takes 13 billion light-years to reach Earth. Thirteen billion light-years is how far away that qua sar was 13 billion years ago when the light we now see first left the star and headed toward where Earth is now. Qua sars are the most distant objects in the universe. More to Explore 207

More to Ex plore

More to Explore Asimov, Isaac. Black Holes, Pulsars, and Quasars . New York: Gareth Stevens, 2003. McGrayne, Sharon. Nobel Prize Women in Science: Their Lives, Struggles, and Mo- men tous Dis cov er ies. New York: Carol Pub lishing Group, A Birch Lane Press Book, 1993. Raymo, Chet. 365 Starry Nights: An Intro duc tion to As tronomy for Ev ery Night of the Year. New York: Simon & Schuster, 1992. Schaaf, Fred. The Am a teur As tron o mer: Ex plo ra tions and In ves ti ga tions. New York: Franklin Watts, 1994. Stille, Darlene R. Ex traor di nary Women Sci en tists. Chicago: Children’s Press, 1995. Com plete Evo lu tion

Com plete Evo lu tion COMPLETE EVOLUTION Year of Dis cov ery: 1967

What Is It? Evo lu tion is driven by sym bi otic merg ers be tween co op er at ing spe cies. Who Dis cov ered It? Lynn Margulis

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Charles Dar win was the first to con ceive that spe cies evolved—changed—over time, and the first to iden tify a driving force for that change—survival of the fittest. Darwin’s the- o ries in stantly be came the bed rock of bi o log i cal think ing and sur vived un chal lenged for a century. Lynn Margulis was the first to discover and prove modi fi ca tion to Darwin’s theory of evolu tion. In so doing, she filled in the one, nagging gap in Darwin’s theory. More than any scien tist since Darwin, she has forced a radi cal revi sion of evolu tion ary thinking. Like Co- perni cus, Gali leo, Newton, and Darwin be fore her, Margulis has uprooted and changed some of science’s most deeply held theorems and assumptions.

How Was It Discov ered?

How Was It Discov ered? Born in 1938, Lynn Margulis was raised on the streets of Chicago. Called preco cious as a child, she en tered the Univer sity of Chicago when only 14 years old. There she stud ied ge net ics and evo lu tion. Since Dar win’s time the field of evo lution has struggled with a prob lem called “varia - tion.” Research ers assumed that varia tion in an indi vid ual’s DNA provided the “trial balloons” that natu ral selec tion kept or discarded. Those muta tions that na ture kept would slowly spread through the entire species. However, a nag ging ques tion could not be an swered: What causes new varia tions in the indi vid u als of a species? Theo ries centered on random er rors that somehow re wrote sections of the DNA genetic code. Even early in her career, it seemed obvi ous to Margulis that this was not what really happened. Margulis saw no hard evi dence to support small, random mu tations driving species evolu tion. Instead she found evi dence for large, sudden jumps—as if evolu tion happened not as a slow, steady creep, but as sudden, dra matic adaptive ad vances. She saw that evolu tion ary change was not nearly so random as others believed. Margulis focused on the concept of sym bi o sis—two or ganisms (or species) liv ing coop er a tively to gether for their mu tual ben e fit. She found many el e men tary ex am ples of two 208 More to Explore 209

spe cies choos ing to live in in ti mate, in ter de pen dent ex is tence. Li chens were com posed of an al gae and a fungus that, living as a sin gle organ ism, survived better than either could alone. Cel lulose-di gest ing bac teria lived in the gut of termites. Neither could survive without the other. Yet together they both thrived. Without a symbi otic merger, this arrangement could never have developed. Margulis found sym bi otic re la tion ships abound ing wher ever she looked. Ex ist ing species sought out new co op er a tive, sym bi otic re la tion ships to im prove their sur viv abil ity. Hu- man corpo rations did it. So did na ture when, for exam ple, a bacte rium (a highly evolved life form) in cor po rated it self into an other ex ist ing spe cies to cre ate a new sym bi otic mu ta tion and the species jumped forward in its capabilities. Margulis studied Earth’s early life forms and discov ered four key symbi o ses that al - lowed the devel op ment of complex life on Earth: (1) a union between a heat-loving archae-bacte rium and a swimming bacte rium (a spiro chete). Some of the origi nal spiro - chete genes were then coopted (2) to produce the orga niz ing cen ters and fil aments that pull genetic mate rial to op po site sides of a cell before it splits. This allowed the creation of com - plex life forms. This new creature engulfed (3) an oxy gen-burn ing bacte rium (once oxy gen be gan to pro lif er ate in the at mo sphere). Fi nally, this swim ming, com plex, ox y gen-pro cess- ing one-celled or gan ism en gulfed (4) a pho to syn the siz ing bac te rium. The re sult of this four-step evolutionary merger was all modern algae and plants! Margulis showed that the cells of plants, ani mals, fungi, and even humans evolved through spe cific se ries of sym biotic mergers that repre sented large, in stant steps forward for the involved species. She published her land mark work in 1967, but biol o gists were skep tical un til it was shown that mito chon dria in all human cells have their own DNA, thus estab lish ing that even hu man cells are the re sult of at least one sym biotic merger. This discov ery spurred a gener a - tion of scien tists who have searched for, found, and studied symbi otic mergers. They have found them everywhere. Nine out of ten plants survive be cause of symbi otic mergers with root fungi that process crucial nutri ents from the soil. Humans and other ani mals have whole colo nies of coop - erat ing bacte ria and other bugs living in our guts to process and digest the food we eat. Without them, we would not sur vive. Without Margulis’s dis covery, Darwin’s theory would have remained incomplete.

Fun Facts: Margulis and her writer/astron o mer husband, Carl Sagan, are the ones who said: “Life did not take over the globe by combat, but by net work ing (co op er a tion), and Dar win’s no tion of evo lu tion driven by the com bat of nat u ral se lec tion is in com plete.”

More to Ex plore

More to Explore Adler, Robert. Sci ence Firsts. New York: John Wiley & Sons, 2002. Brock man, John. Curi ous Minds: How a Child Becomes a Sci entist. New York: Knopf, 2005. Margulis, Lynn. Diver sity of Life: The Five Kingdoms . Hillside, NJ: Enslow Pub lish - ers, 1996. 210 Com plete Evo lu tion

———. Microcosmos: Four Billion Years of Evolu tion from Our Micro bial Ances - tors. Berke ley: Uni ver sity of Cal i for nia Press, 1997. ———. Symbi otic Planet: A New Look at Evolu tion. New York: Basic Books, 1998. ———. What Is Life? Berke ley: Uni ver sity of Cal i for nia Press, 2000. Sapp, Jan. Evo lu tion by As so ci a tion: A His tory of Sym bi o sis. New York: Oxford Uni- versity Press, 1999. Dark Mat ter

Dark Matter DARK MATTER Year of Dis cov ery: 1970

What Is It? Matter in the universe that gives off no light or other detect ible ra di a tion. Who Dis cov ered It? Vera Ru bin

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Cal cula tions of the ex pansion of the universe didn’t work. Calcu la tions of the speed of stars in distant galax ies didn’t match what astron o mers observed. Calcu la tions of the age of the universe (based on the speed of its expan sion) didn’t make sense. Something had to be wrong with the methods used for these calcu la tions. With these major question marks hang - ing over the calcu la tions, no one could depend ably calcu late the his tory of, present mass of, or future of, the uni verse. Much of physics research ground to a halt. Vera Rubin only meant to test a new piece of equipment. What she dis covered was that the ac tual motion of stars and galax ies appeared to prove that Newton’s laws—the most funda men tal princi ples of all of as tronomy—were wrong. In trying to explain the differ ence be tween ob ser va tions and New to nian phys ics, Ru bin dis cov ered dark matter —mat ter that exists but gives off no light or other radi a tion that scien tists could detect. Astron o mers and physi cists now believe that 90 percent of the mass of the universe is dark matter.

How Was It Discov ered?

How Was It Discov ered? In 1970 Vera Rubin worked at the Depart ment of Terres trial Magne tism (DTM) at the Car - negie Insti tute of Washing ton. DTM’s direc tor, astron o mer Kent Ford, had just created a new high-speed, wide-band spectro graph that could complete eight to ten spectro graphs (graphic images on chart paper of some spectrum—in this case of the energy emitted from distant stars at dif - ferent frequen cies along the frequency spectrum) in a single night while exist ing models were lucky to complete one in a day. Vera was itching to see what Ford’s inven tion could do. During the night of March 27, 1970, Rubin focused the DTM telescope on Andromeda, the nearest galaxy to our own. She planned to see whether Andromeda’s millions of stars re ally moved as exist ing theory said they should. When at tached to pow er ful tele scopes, spec tro graphs de tect the pres ence of dif fer ent ele ments in a distant star and display what they detect on chart paper. Ru bin rigged a high-power mi croscope to read the charts cre ated by Ford’s spectrograph. Rubin knew that the marks astron o mers measured on a spectro graph shift a tiny bit higher or lower on the frequency chart paper depend ing on whether the star is moving to- 211 212 Dark Matter

ward Earth or away from it. This frequency shift is called a Doppler shift. The same kind of shift happens with sound waves as a car passes and the sound of its engine seems to change to a lower frequency. The greater that shift, the greater the object’s speed. Rubin wanted to see if she could use Doppler shifts and Kent’s new spectro graph to measure the speed of stars in distant galaxies. She found that the stars near the outer edge of Andromeda moved just as fast as the stars near the galaxy’s center. That wasn’t the way it was supposed to be. Over a period of two months she completed 200 spec trographs. For ev ery galaxy it was the same. The ve loci ties of stars she measured were all wrong. Accord ing to every known law of physics, some of those stars were moving too fast for gravity to hold them in their galax ies, and they should fly off into space. But they didn’t. Rubin was left with two pos sible ex plana tions. Either Newton’s equations were wrong (something the scien tific world would not accept) or the universe contained extra matter no as tron o mer had detected. She chose the sec ond ex pla na tion and named this ex tra mat ter “dark mat ter” since it could not be seen or detected. Rubin calcu lated how much dark matter would be needed and how it would have to be dis tributed through out the uni verse in order to make Newton’s equations correct. She found that 90 percent of the uni verse had to be dark matter. It took the rest of the scien tific commu nity a full decade to grudgingly accept Vera Ru- bin’s results and the real ity that most of the mat ter in the universe could not be seen or detected by any means available to humans. However, Vera Rubin’s work in that summer of 1970 changed every calcu la tion and theory about the structure and ori gins of our universe. It vastly improved astron o mers’ ability to cor rectly calcu late the distri bu tion and mo tion of mat ter. Meanwhile—luck ily— Newton’s laws of motion still survive.

Fun Facts: NASA has tried to take a photo graph of dark matter (something no once can see or directly detect) by com bining X-ray telescope images from the ROSAT satel lite with other satel lite imag ery; the photo shown at http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/dis play/darkmatt er. html is the result. It could be the first photo of dark matter.

More to Ex plore

More to Explore Golway, James. Where Is the Rest of the Uni verse? (video). Los Angeles: KCET, 1991. Kraus, Law rence. The Fifth Es sence: The Search for Dark Matter. New York: Ba sic Books, 1993. ———. The Mystery of Missing Mass in the Universe . New York: Basic Books, 2000. Ru bin, Vera. Bright Galax ies, Dark Matter. New York: Ameri can Insti tute of Physics, 1997. St. Bartusiak, Mar cia. Through a Uni verse Darkly. New York: HarperCollins, 1993. Tucker, Wallace. The Dark Matter . New York: Mor row Books, 1998. Yount, Lisa. Con tem po rary Women Sci en tists. New York: Facts on File, 1994. The Na ture of Dino saurs

The Nature of Dino saurs THE NATURE OF DINOSAURS Year of Dis cov ery: 1976

What Is It? How dino saurs re ally acted, moved, and lived. Who Dis cov ered It? Robert Bakker

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Dino saurs were plodding, cold-blooded mon sters. They were sluggish, dull-gray, and so dumb they weren’t ca pable of de cent parenting. That was the classi cal view of dino saurs through the first half of the twenti eth century. That was how dino saurs were depicted in illus tra tions. That was what ex pert pa le on tol o gists be lieved. Rob ert Bakker shattered those beliefs. Robert Bakker was the first to claim that dino saurs were warm blooded, color ful, and quick, intel li gent, and agile. He also first proposed that birds were descended from dino - saurs. The images we see of dino saurs—from Ju ras sic Park to sci ence mu seum dis - plays—all owe their di no saur concepts to Robert Bakker’s dis cover ies. Robert Bakker completely rewrote the book on dinosaurs.

How Was It Discov ered?

How Was It Discov ered? A great reve la tion swept over Robert Bakker one night during his sopho more year at Yale Uni versity. As he walked through the dark ened mu seum, faint bits of light caught the dino saur skel etons and made them appear to move through the shadowed stillness. It occurred to Robert as he studied the famil iar bones that these creatures had ruled the earth for 165 million years. They could n’t have been stupid, cold-blooded and sluggish. In telli gent mammals were around. They would have taken over unless the dino saurs kept winning because they were fundamentally better. Robert Bakker set out—all alone—to prove that the prevail ing view of dino saurs was completely wrong. Bakker turned to four sources of infor ma tion to de velop his case: compar - ative anatomy (compar ing the size and shape of simi lar parts of differ ent species), lati tu di nal zonation (where the ani mals live), the cumu la tive fossil record (all previ ously collected dino - saur bones and skel etons), and ecology (re lation ship of a species to its envi ron ment). For three years Bakker exhaustively studied the bones of mam mals and found that they, as were dino saur bones, were rich in blood vessels and lacked growth rings—just the oppo site of cold-blooded reptiles. He found that Creta ceous dino saurs thrived in northern Canada where cold-blooded rep tiles could not have survived. Fi nally he studied Afri can and North Ameri can ecosys tems and found that warm-blooded preda tors eat six to eight 213 214 The Nature of Dino saurs

times as much per pound of body weight as do reptile preda tors. By studying the fossil record, Bakker found that the ra tio of pred ators to herbi vores in dino saur ecosys tems matched what would be expected of a warm-blooded ecosystem. Dino saurs had to have been warm-blooded. Their bones, rela tive num bers, and loca - tions proved it. He studied the legs of zoo an imals, compar ing leg structure to how they moved. Did a chicken’s leg bend differ ently than a zebra’s? How did those differ ences re late to the differ - ent activ ity of each an imal? How did form dictate function for each an imal, and how did function dic tate form? What did the shape of a dino saur’s joints and the size of its bones say about how it must have moved and functioned? He tried to account for this mo tion and the implied prob able muscle masses to control and move each bone in his drawings. He compared leg bone size, shape, and density for hundreds of modern ani mals with those of dino saurs. He found that dino saur leg bones closely matched the bone structure of running mammals—not those who sprint for 10 seconds when alarmed, but those who regu - larly run for 20 minutes. Dino saurs were runners. Their structure proved it. That also meant that they were agile. No slug gish, clumsy oaf would be a natu ral run ner. Bakker again turned to the fossil record and found that very few baby and juve nile di - nosaur skele tons had been discov ered. This meant that few died, which in turn meant that parent dino saurs had to have been very success ful at protect ing, shelter ing, and feeding their young. Dino saurs were good parents. The old myths were shat tered. Bakker published his find ings while still a gradu ate student at Harvard. But it took another 20 years of intense data collec tion and analy sis for the tide of belief to turn in Bakker’s direc tion. Even after Bakker’s discov er ies revo lu tion ized sci - ence’s views of dino saurs, he was still viewed with sus picion as an untrust worthy radi cal.

Fun Facts: Giant Bronto sau rus became the most popu lar of all dino saurs in the late nine teenth and early twenti eth centu ries. Its name means “thunder lizard.” By 1970 some scien tists claimed that “Bronto sau rus” should not be used since it re ferred to three differ ent species: Apatosaurus, Brachiosaurus, and Camarasaurus. The argu ment contin - ues, though it’s been 80 million years since any of the three thundered across the earth.

More to Ex plore

More to Explore Bakker, Robert. The Dino saur Here sies . New York: Mor row Books, 1988. ———. “Un earth ing the Ju ras sic.” In Sci ence Year 1995. New York: World Book, 1995. Daintith, John. Bio graph i cal En cy clo pe dia of Sci en tists, Vol ume 1. Phil a del phia: In - sti tute of Phys ics Pub lish ing, 1994. Krishtalka, Leonard. Di no saur Plots. New York: William Morrow, 1999. Of fi cer, Charles. The Great Di no saur Ex tinc tion Con tro versy. Read ing, MA, Addi son Wasley, 1996. Stille, Darlene. “Di no saur Sci en tist.” In Science Year 1992. New York: World Book, 1993. Plan ets Ex ist Around Other Stars

Planets Exist Around Other Stars PLANETS EXIST AROUND OTHER STARS Year of Dis cov ery: 1995

What Is It? Planets—even planets like Earth—exist around other stars. Who Dis cov ered It? Michel Mayor and Didier Queloz

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? One of the great questions for human ity has always been: Are we alone? Science has long asked: Are we the only solar system with planets—and the only one with plan ets that could support life? The discov ery of planets around other stars makes it likely that other plan ets ex ist ca pa ble of sup port ing life. Of great im portance to astron o mers, the discov ery of other so lar systems lets them test their theo ries on the ori gin of plan ets and solar systems. The discov ery of distant planets has funda men tally changed how we perceive our place in the universe.

How Was It Discov ered?

How Was It Discov ered? In the sixth century B.C., Greek sci en tist Anaximander was the first to theo rize that other planets must exist. In 1600 Italian priest and astron o mer Giordano Bruno was burned at the stake by the Cath o lic Church for profess ing the same belief. Ameri can astron o mers were actively searching through giant telescopes for planets orbit ing other stars by late the 1940s. Michel Mayor was born in 1942 and even as a child was fasci nated by stars and astron - omy. With his collab o ra tor, Antoine Duquennoy, he joined the many astron o mers search - ing for small objects in the universe. But Mayor searched not for planets, but for brown dwarfs—cool, dim objects thought to form like stars, but which failed to grow massive enough to support hydro gen fusion and thus never lit up with starry furnace and fire. Too big for plan ets, too small to become stars, brown dwarfs were a galactic oddity. Astron o mers, however, had a problem: telescopes can’t see plan ets and brown dwarfs because they don’t give off light. Instead, astron o mers searched for slight side-to-side wob- bles in the motion of a star caused by the gravi ta tional tug of a large planet (or brown dwarf). Some tried to detect such wobble by carefully measur ing the posi tion of a star over the course of months or years. Others (Mayor included) looked for this wobble by us ing Dopp- 215 216 Planets Exist Around Other Stars

ler shift and mea suring tiny shifts on a spectro graph in the color of the light coming from a star that would be the re sult of changes in the star’s mo tion toward or away from Earth. Follow ing the death of Duquennoy in 1993, Mayor teamed with gradu ate student Didier Queloz and devel oped a new, more sensi tive spectro graph to search for brown dwarfs. Their new spec tro graph was ca pa ble of mea sur ing ve loc ity changes as small as 13 meters per second—about the same as the wobble in our sun’s motion caused by Ju piter’s gravitational tug. But ev eryone as sumed that such massive planets would take years to or bit a star (as they do in our system). Thus the wob ble from a planet’s tug would take years of data to notice. It never occurred to Mayor to use his new spectro graph and a few months’ worth of time on a tele scope to search for a planet. Begin ning in April 1994, using the Haute-Provence Obser va tory in southern France, Mayor and Queloz tested their new spectro graph on 142 nearby stars, hoping to detect a wobble that would in dicate a massive nearby ob ject like a brown dwarf. In Janu ary 1995 one star, 51 Peg (the fifty-first brightest star in the constel la tion Peg asus) caught Queloz’s eye. It wobbled. It wobbled back and forth every 4.2 days. They tested the star’s light to make sure it didn’t pulse. They tested to see if sun spots might create an appar ent wob ble. The tested to see if 51 Peg puffed up and contracted to create the ap pear ance of wobble. Nothing could account for 51 Peg’s wobble ex cept for a siz- able or bit ing object. From the amount of 51 Peg’s wob ble they cal culated the mass of the object and knew it was too small to be a brown dwarf. It had to be a planet! They had discov ered a planet outside our solar system. By 2005, sev eral hundred other planets had been located—gas giants speed ing around Mercury-sized orbits; some rocky plan ets in cozy, not-too-hot-and-not-too-cold orbits; even some drifting free through space without a star to circle. Earth is certainly not alone. Mayor and Queloz were the first to dis cover proof of this spectac u lar reality.

Fun Facts: If only one star in ten has planets (and current knowledge in - di cates that at least that many do), if the av er age star with plan ets has at least three, and if only one in ev ery hundred are rocky planets in life-sus- taining orbits (and re cent discov er ies indi cate that to be the case), then there are at least 300,000 planets capa ble of support ing life in our galaxy alone!

More to Ex plore

More to Explore Adler, Robert. Sci ence Firsts. New York: John Wiley & Sons, 2002. Boss, Alan. Looking for Earths: The Race to Find New Solar Systems. New York: John Wiley & Sons, 1998. Croswell, Ken. Planet Quest: The Epic Discov ery of Alien So lar Systems. New York: Free Press, 2002. More to Explore 217

Gold smith, Don ald. Worlds Unnum bered: The Search for Extrasolar Planets. Sausalito, CA: Univer sity Science Books, 2000. Halpren, Paul. The Quest for Alien Planets: Explor ing Worlds Outside the Solar Sys- tem. New York: Plenum, 1999. Lemonick, Mi chael. Other Worlds: The Search for Life in the Universe. New York: Si - mon & Schuster, 2001. Ac cel er at ing Uni verse

ACCELERATING UNIVERSE ACCELERATING UNIVERSE Year of Dis cov ery: 1998

What Is It? Our universe is not only expand ing; the rate at which it expands is speed ing up, not slowing down as had been as sumed. Who Dis cov ered It? Saul Perlmutter

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? A great debate began after Edwin Hubble discov ered that the universe is expand ing: Is that ex pansion slowing so that it will eventu ally stop and the universe will begin to collapse? Saul Perlmutter discov ered that the expan sion of the universe is actu ally ac cel er at - ing, shatter ing all exist ing scien tific models of the mo tion of the universe. The universe is expand ing faster now than it ever has before. It is tearing itself apart. Gravity is not slowing the expansion as it is supposed to. This discov ery has created a monu mental shift in how sci entists view the universe, its past, and its future. It has affected the calcu la tions of the Big Bang and even scien tists’ view of what makes up the universe. The Journal of Sci ence called this dis covery the 1998 “Breakthrough of the Year.”

How Was It Discov ered?

How Was It Discov ered? Edwin Hubble discov ered that the universe was expand ing in 1926. Scien tists built new models that assumed that the expan sion was slowing down as gravity tugged on stars and gal axies, pulling them back to ward each other. This model seemed logi cal. However, a few, highly techni cal problems existed with the mathe mat ics asso ci ated with this model. Ein stein tried to explain these prob lems by cre- ating something he called the “cosmo log i cal constant”—a force that opposed gravity. But he then re jected the idea as his great est scientific blunder. After receiv ing a Ph.D. in physics in 1986, Saul Perlmutter worked at Lawrence Berke ley Na tional Lab o ra tory and headed the Su per nova Cos mol ogy Pro ject (SCP). This group used the Hubble Space Telescope to find and study distant supernovae (explod ing stars). They chose supernovae because they are the brightest objects in the universe. Type Ia supernovae produce a constant amount of light, and it is be lieved that all Ia supernovae shine at about the same brightness. This made them ideal for Perlmutter’s study. Over the 10-year pe riod from 1987 to 1997, Perlmutter devel oped a technique to identify supernovae in dis tant galax ies and to an alyze the light they pro duce. His team searched tens of thousands of galax ies to find a half dozen type Ia supernovae. 218 More to Explore 219

When Perlmutter found an Ia super nova, he mea sured its brightness to deter mine its dis tance from Earth. (The brighter it is, the closer it is.) Perlmutter also measured the red shift of the super nova’s light. This is a technique based on Doppler shifts. If a star is moving to ward Earth, its light is compressed and its color shifts a little toward blue. If the star is moving away, its light is stretched and the color shifts toward red. The faster the star is moving, the greater its color shift. By measur ing the su pernova’s red shift, Perlmutter could calcu late the star’s ve loc ity away from Earth. Now came the hard part. Other factors could account for a red shift, and Perlmutter had to prove that the red shifts he measured were the result of only the star’s motion away from Earth. Space dust can ab sorb some light and shift its color. Some gal axies have an overall color hue that could distort the color of the light com ing from a super nova. Each of a dozen possi ble sources of error had to be explored, tested, and eliminated. Finally, in early 1998, Perlmutter had collected reli able distance and veloc ity data for a dozen Ia supernovae spread across the heavens. All were moving at tremen dous speeds away from Earth. Perlmutter used math emat ical models to show that these galax ies couldn’t have been travel ing at their current speeds ever since the Big Bang. If they had, they would be much far ther away than they re ally are. The only way Perlmutter’s data could be cor rect was for these gal axies to now be travel ing outward faster than they had in the past. The gal ax ies were speed ing up, not slowing down. The universe had to be expand ing at an ac cel er at ing rate! Perlmutter’s discov ery showed that some new and unknown force (named “dark en - ergy” by Michael Turner in 2000) must be pushing matter (stars, galax ies, etc.) out ward. More recent research us ing new specially designed sat ellites has shown that the universe is filled with this “dark en ergy.” (Some esti mates say that two-thirds of all energy in the universe is dark energy.) Over the next few years this new discov ery will rewrite human theo - ries of the or igin and structure of the universe.

Fun Facts: A new $20 million telescope is being built at the South Pole to study and explain why the universe is accel er at ing, since this discov - ery vio lates all exist ing theo ries about the birth and expan sion of the universe. The tele scope will become op era tional in 2007.

More to Ex plore

More to Explore Adair, Rick. Sci en tific In for ma tion about the Uni verse and the Sci en tific The o ries of the Evolu tion of the Universe: An Anthol ogy of Current Thought. Cherry Hill, NJ: Rosen Central, 2005. Anton, Ted. Bold Science: Seven Scien tists Who Are Changing Our World. New York: W. H. Freeman, 2001. Couper, Heather. DK Space En cy clo pe dia. New York: DK Publish ers, 2001. Gribbin, John. The Birth of Time: How Astron o mers Mea sured the Age of the Uni- verse. New Haven, CT: Yale Univer sity Press, 2001. ———. EYEWITNESS: Time and Space. New York: DK Publish ers, 2000. Kerrod, Robin. The Way the Uni verse Works. New York: DK Publish ers, 2006. Hu man Ge nome

Hu man Ge nome HUMAN GENOME Year of Dis cov ery: 2003

What Is It? A detailed map ping of the entire hu man DNA ge netic code. Who Dis cov ered It? James Wat son and J. Craig Venter

Why Is This One of the 100 Greatest?

Why Is This One of the 100 Great est? Deci pher ing the human genetic code, the human genome, has been called the first great scien tific discov ery of the twenty-first century, the “Holy Grail” of biol ogy. DNA is the blue print for con struct ing, op er at ing, and main tain ing a liv ing or gan ism. It di rects the trans forma tion of a fertil ized egg into a complete and com plex human be ing. De cipher ing that code is the key to under stand ing how cells are instructed to develop and grow, the key to under stand ing the development of life itself. Because the human genome is unimag in ably complex, it seemed impos si ble to deci - pher the three bil lion el ements of this mo lec u lar code. Yet this Her cu lean ef fort has al ready led to med i cal break throughs in ge netic de fects, dis ease cures, and in her ited dis eases. It is the key to future discov er ies about human anatomy and health. Under stand ing this genome vastly increased our appre ci a tion of what makes us unique and what connects us with other living species.

How Was It Discov ered?

How Was It Discov ered? Austrian monk Gregor Mendel discov ered the concept of hered ity in 1865, launching the field of genet ics. In 1953 Francis Crick and James Watson discov ered the double helix shape of the DNA mol e cule that car ried all ge netic instructions. The problem was that there were billions of genetic instruc tions carried on the com - plete human genetic code, or genome. Under stand ing it all seemed a physi cally impos si ble task. Sequenc ing the en tire hu man ge nome was a project 20,000 times big ger and harder than any bi o log i cal project attempted to that time. Charles De Lisi at the U.S. De partment of Energy (DOE) was the first to gain govern - ment funds to begin this monu men tal process, in 1987. By 1990, the DOE had joined with the National In stitutes of Health (NIH) to create a new orga ni zation, the In terna tional Hu - man Genome Sequenc ing Consor tium (IHGSC). James Watson (of DNA discov ery fame) was asked to head the project and was given 15 years to accom plish this monumental task.

220 How Was It Discov ered? 221

At that time, scien tists believed that human DNA contained about 100,000 genes spread along 23 chromo somes locked onto DNA’s double he lix, held together by over 3 billion base pairs of mole cules. Watson’s task was to identify, inter pret, and sequence every gene on ev ery chromo some, as well as every one of those billions of base pairs. Cer tainly, the ability to iden tify and sequence indi vid ual pairs ex isted. Watson’s problem was one of size. Using the exist ing (1990) technol ogy, it would take thousands of years for all exist ing labs to com plete the iden tifi ca tion and sequenc ing of three bil lion pairs. Watson decided to start with large-scale maps of what was known about chromo somes and work down toward the details of indi vid ual pairs. He directed all IHGSC scien tists to work toward creat ing physi cal and linking maps of the 23 chromo somes. These maps would provide an overview of the human genome and would include only those few “snippets” of ac tual gene se quences that were already known. By 1994 this first effort was complete. Watson ordered IHGSC scien tists to map the complete genome of the simplest and best-known life forms on Earth to re fine their technique be fore attempt ing to work on the human ge nome. IHGSC scien tists chose fruit flies (stud ied ex ten sively since 1910), e. coli (the com mon in tes ti nal bac te rium), bread molds, and simple nema todes (tiny oceanic worms). In the mid-1990s, work began on mapping the tens of millions of base pairs in these simple genomes. However, not all biol o gists agreed with this approach. J. Craig Venter (a gene se - quencer at the Insti tutes of Health) believed that scien tists would waste precious years fo- cusing on Wat son’s “big pic ture” and should instead se quence as many spe cific parts of the genome as they could and piece these in divid ual sequences together later. A war began between Watson (repre sent ing the “top down” approach) and Venter (repre sent ing the “bottom up” approach). Ac cusa tions and ugly words erupted from both sides at congres sional hearings, at funding meetings, and in the press. Venter quit his govern ment posi tion and formed his own company to de velop as much of the genome sequence as he could ahead of IHGSC’s effort. In 1998 Venter shocked the world by announc ing that he would use linked supercom put ers to complete his sequenc ing of the en tire hu man ge nome by 2002, three years ahead of IHGSC’s timetable. In early 2000 Presi dent Clinton stepped in to end the war and merged both sides into a unified ge nome effort. In 2003 this merged team re leased their prelim i nary re port, de tail ing the en tire sequence of the human ge nome. In written form, that genome would fill 150,000 printed pages (500 books, each 300 pages long). Surpris ingly, these scien tists found that humans have only 25,000 to 28,000 genes (down from the previ ously be lieved 100,000). A human’s genetic sequence is only a few percent differ ent from that of many other species. Even though the infor ma tion on this genetic sequence is only a few years old, it has already helped med i cal re search ers make ma jor advances on dozens of dis eases and birth de - fects. Its full value will be seen in medi cal break throughs over the next 20 to 50 years.

Fun Facts: If the DNA sequence of the human genome were compiled in books, the equiva lent of 200 volumes the size of a Manhattan telephone book (at 1,000 pages each) would be needed to hold it all. 222 Hu man Ge nome

More to Ex plore

More to Explore Boon, Kevin. Human Ge nome Project: What Does De coding DNA Mean for Us? Berkeley Heights, NJ: Enslow, 2003. Brooks, Martin. Get a Grip on Genet ics. New York: Time-Life Books, 1999. Mar shall, Eliz a beth. The Human Ge nome Project: Cracking the Code Within Us. New York: Scho las tic Li brary, 2001. Sloan, Chris to pher. The Human Story: Our Evolu tion from Prehis toric Ances tors to To day. Wash ing ton, DC. Na tional Geo graphic So ci ety, 2004. Toriello, James. Hu man Ge nome Pro ject. Cherry Hill, NJ: Rosen Publish ing, 2003. Ref er ences

Ref er ences Ref er ences

These book and Internet sources are good general refer ences on scien tific discov ery, on the process of scien tific inves ti ga tion, on the history of scien tific discov er ies, and on im - por tant scientists.

Book Sources Aaseng, Na than. Twen ti eth-Cen tury In ven tors. New York: Facts on File, 1996. Adler, Robert. Sci ence Firsts, New York: John Wiley & Sons, 2002. ———. Med i cal Firsts. New York: John Wiley & Sons, 2004. Anton, Ted. Bold Science: Seven Scien tists Who Are Changing Our World. New York: W. H. Freeman, 2001. Ashby, Ruth. Herstory. New York: Penguin Books, 1995. Asimov, Isaac. Asimov’s Chronol ogy of Science and Dis covery . New York: Harper & Row, 1994. Atkins, Peter, Gali leo’s Finger: The Ten Great Ideas of Science. New York: Random House, 2004. Aubrey, John. Brief Lives, Volumes I and II. New York: Claren don Press, 1998. Badger, Mark. Two-Fisted Sci ence. New York: G. T. Labs, 2001. Berlinski, David. New ton’s Gift. New York: Free Press, 2000. Beshore, George. Science in Ancient China. New York: Franklin Watts, 1996. Boorstin, Daniel. The Discover ers: A History of Man’s Search to Know His World and Him self. New York: Random House, 1997. Brock man, John. Curi ous Minds: How a Child Becomes a Sci entist. New York: Knopf, 2005. Brodie, James. Cre ated Equal: The Lives and Ideas of Black Amer ican Inven tors . New York: William Morrow, 1999. Bryan, Jenny. The History of Health and Medi cine . Florence, KY: Thompson Learn- ing, 1999. Bunch, Bryan. The History of Science and Tech nology. New York: Houghton Mifflin, 2004. Chang, Laura, ed. Sci en tists at Work. New York: McGraw-Hill, 2000.

223 224 Ref er ences

Clark, Donald. En cy clo pe dia of Great In ven tors and Dis cov er ies. London: Marshall Caven dish Books, 1991. Co hen, Ber nard. Rev o lu tions in Sci ence. Cam bridge, MA: Harvard Univer sity Press, 1995. Collins, H., and T. Pinch. What You Should Know About Science. New York: Cam - bridge Uni ver sity, 1998. Conrad, Law rence, et al. The West ern Medi cal Tra dition: 800 BC to 1900 AD. New York: Cambridge Univer sity Press, 1999. Crop per, Wil liam. Great Phys i cists. New York: Ox ford Uni versity Press, 2001. Day, Lance, ed. Bio graph i cal Dic tio nary of the His tory of Tech nol ogy. New York: Routledge, 1996. Di a gram Group. Facts on File Chemis try Handbook . New York: Facts on File, 2000. ———. Facts on File Phys ics Handbook. New York: Facts on File, 2006. Downs, Robert. Landmarks in Science . Englewood, CO: Librar ies Unlim ited, 1993. Dreyer, J. A His tory of Astron omy from Thales to Kepler. New York: Do ver, 1993. Fer gu son, Keith. Measur ing the Universe: The Histor i cal Quest to Quantify Space. New York: Headline Books, 1999. Fox, Ruth. Mile stones in Med i cine. New York: Random House, 1995. Fran cis, Ray mond. The Il lus trated Al ma nac of Sci ence, Tech nol ogy, and In ven tion. New York: Plenum Trade, 1997. Fron tier Press Co. Great Mas ters of Achieve ment in Sci ence and Dis cov ery. Whitefish, MT: Kessinger, 2005. Gal lant, Roy. The Ever-Changing Atom. New York: Benchmark Books, 2000. Garwin, Laura. A Century of Nature: Twenty-One Discov er ies That Changed Science and the World. Chicago: Univer sity of Chicago Press, 2003. Gibbs, C.R. Black Inven tors from Africa to America . Silver Springs, MD: Three Di- men sional, 1999. Gratzer, Wal ter. Eurekas and Euphorias. New York: Ox ford Uni versity Press, 2004. Greenstein, George. Por traits of Dis cov ery: Pro files in Sci en tific Ge nius. New York: John Wiley & Sons, 1997. Gribbin, John. The Scien tists: A History of Science Told through the Lives of Its Great- est In ven tors. New York: Random House, 2002. Hall, Ruppert. A Brief History of Sci ence. Iowa City: Iowa State Press, 1999. Hammond, Allen, ed. A Passion to Know: 20 Pro files in Science. New York: Scribner’s, 1995. Hatt, Christine. Sci en tists and Their Dis cov er ies. New York: Franklin Watts, 2001. Ha ven, Kend all. Amaz ing Amer i can Women. Englewood, CO: Li braries Unlim ited, 1996. Ref er ences 225

———. Mar vels of Sci ence. Englewood, CO: Librar ies Unlim ited, 1994. ———. The 100 Greatest Science Inven tions of All Time. Westport, CT: Li braries Un- lim ited, 2005. ———. That’s Weird! Awe some Sci ence Mys ter ies. Boulder, CO: Fulcrum Re- sources, 2000. ———. Women at the Edge of Discov ery . Englewood, CO: Li braries Unlim ited: 2003. Haven, Kend all, and Donna Clark. The 100 Most Popu lar Scien tists for Young Adults. Westport, CT: Li brar ies Un lim ited, 2001. Hawk ing, Ste ven. A Brief History of Time. New York: Bantam, 1996. Haw ley, John, and Kather ine Holcomb. Foun da tions of Mod ern Cos mol ogy. New York: Ox ford Uni versity Press, 1998. Hayden, Robert. 9 Af ri can Amer i can In ven tors. New York: Twenty-First Cen tury Books, 1992. Heilbron, John. The Oxford Compan ion to the History of Modern Science . New York: Ox ford Uni ver sity Press, 2003. Hooft, G. In Search of the Ulti mate Building Blocks. New York: Cambridge Univer - sity Press, 1997. Huff, Toby. The Rise of Early Modern Science . New York: Cambridge Univer sity Press, 1993. Irwin, Keith. The Romance of Chemis try . New York: Viking Press, 1996. Jones, Al ex an der, ed. Cambridge History of Science: Ancient Science. New York: Cam bridge Uni ver sity Press, 2006. Jungk, R. Brighter Than a Thousand Suns: A Personal History of the Atomic Scien - tists. New York: Harcourt Brace, 1998. Kass-Si mon, Amy. Women of Science: Righting the Record . Bloomington: Indi ana Uni ver sity Press, 1996. Koestler, Arthur. The Sleepwalk ers: A History of Man’s Changing Vision of the Uni - verse. London: Hutch inson & Co., 1999. Levere, Trevor. Trans forming Mat ter : A History of Chemis try from Alchemy to the Buckyball. Bal timore, MD: Johns Hopkins Uni versity Press, 200 Lomask, Milton. In ven tion and Tech nol ogy Great Lives. New York: Charles Scribner’s Sons, 1994. Mad dox, John. What Re mains to Be Discov ered. New York: Free Press, 1998. Mather, John, and John Boslough. The Very First Light: The True Inside Story of the Scien tific Journey Back to the Dawn of the Universe . New York: Basic Books, 1996. McGrayne, Sharon. Nobel Prize Women of Science. New York: Birch Lane Press, 1997. 226 Ref er ences

McNeil, Ian. An En cy clo pe dia of the His tory of Tech nol ogy. New York: Routledge, 1996. Messadie, Ger ald. Great Sci en tific Dis cov er ies. New York: Chambers, 2001. Nader, Helen. Rethink ing the World: Discov ery and Science in the Renais sance. Bloomington: In di ana Uni ver sity Press, 2002. Na tional Geo graphic So ci ety. In ven tors and Dis cov er ies: Chang ing Our World. Wash ing ton, DC: Na tional Geo graphic So ci ety, 1998. Nel son, Clif ford. Dis cov er ies in Sci ence. New York: Harcourt Brace, 1994. North, John. The Norton His tory of Astron omy and Cosmol ogy . New York: Norton, 1995. Pais, Abra ham. The Genius of Science: A Portrait Gallery . New York: Oxford Univer - sity Press, 2000. Palmer, Eric. Philos o phy of Science and History of Science. New York: Xlibris Corp., 2000. Parker, Steve. Gali leo and the Universe . New York: HarperCollins Children’s Books, 1996. Perkowitz, Sidney. Empire of Light: A His tory of Discov ery in Science. New York: Na tional Acad e mies Press, 1998. Philbin, Tom. The 100 Greatest Inven tions of All Time. New York: Cita del Press, 2003. Por ter, The o dore. The Cam bridge His tory of Science. New York: Cambridge Univer - sity Press, 2003. Pull man, Ber nard. The Atom in the His tory of Human Thought. New York: Ox ford Uni ver sity Press, 1999. Pyenson, Lewis, and Susan Pyenson. Servants of Nature, New York: HarperCollins, 1999. Rattanski, P. M. Pi o neers of Sci ence and Dis cov ery. Charleston, WV: Main Line Books, 1997. Schlessinger, Bernard, and June Schlessinger. The Who’s Who of Nobel Prize Winners 1901–1999. New York: Oryx Press, 2001. Shep herd, Linda. Lift ing the Veil: The Femi nine Face of Sci ence. Boston: Shambala, 2000. Sherrow, Vic to ria. Great Sci en tists. New York: Facts on File, 1998. Sil vers, Rob ert. Hidden Histo ries of Science. New York: New York Review of Books, 2003. Singh, Simon. The Science Book: 250 Milestones in the His tory of Science. London: Cassell, 2001. Smith, Roger. The Norton His tory of Human Sci ences. New York. W. W. Norton, 1997. Ref er ences 227

Snedden, Robert. Sci en tists and Dis cov er ies. Portsmouth, NH: Heinemann, 2001. Stille, Darlene. Ex traor di nary Women Sci en tists. Chicago: Children’s Press, 1999. Sturtevant, A. H. A History of Genet ics . Cold Spring Harbor, NY: Cold Spring Harbor Lab o ra tory Press, 2001. Suplee, Curt. Milestones of Sci ence. Wash ing ton, DC: Na tional Geo graphic So ci ety, 2000. Tem ple, Rob ert. The Ge nius of China: 3,000 Years of Science, Dis covery, and Inven - tion. New York: Simon & Schuster, 2000. Veglahn, Nancy. Women Scien tists. New York: Facts on File, 1997. Whitfield, Pe ter. Landmarks in West ern Science. London: British Li brary, 1999. Yenne, Bill. 100 Inven tions That Shaped World History . New York: Bluewood Books, 1993. Yuval, Neeman, and Yoram Kirsh. The Par ti cle Hunt ers. Cam bridge, MA: Harvard Uni ver sity Press, 1999.

Internet Web Site Sources These sites focus on the history of science and discov er ies in general. Conduct your own searches for spe cific sci en tific top ics, fields, or pe ri ods. www.echo.gmu.edu/cen ter www.hssonline.org/ www.depts.wash ing ton.edu/hssexec/ www.bshs.org.uk www2.lib.udel.edu/subj/hsci/internet.htm www.fordham.edu/halsall/sci ence/sciencesbook.html www2.sjsu.edu/elementaryed/ejlts/ar chives/di ver sity/hampton.htm www.aip.org/his tory/web-link.htm www.fas.har vard.edu/~hsdept/ www.mpiwg-berlin.mpg.de www.hps.cam.ac.uk/whipple/ www.mdx.ac.uk/www/study/sshtim.htm hos.prince ton.edu www.astro.uni-bonn.de/~pbrosche/hist_sci/hs_gen eral.html www.mhs.ox.ac.uk/ex hib its/ www.smithsonianeducation.org/ www.hstm.im pe rial.ac.uk/rausingschol.htm www.clas.ufl.edu/us ers/rhatch/pages/10-HisSci/links/in dex.htm hpst.stan ford.edu/ www.li brary.ualberta.ca/sub ject/historyscience/guide/in dex.cfm www.sil.si.edu/Li brar ies/Dibner/in dex.htm www.physlink.com/Ed u ca tion/His tory.cfm www.si.edu/his tory_and_cul ture/his tory_of_sci ence_and_tech nol ogy/ www.mla-hhss.org/histlink.htm

Ap pen dix 1: Dis cov er ies by Scien tific Field

Ap pen dix 1: Dis cov er ies by Sci en tific Field Ap pen dix 1: Dis cov er ies by Sci en tific Field

These tables list the 100 greatest science discov er ies divided into their appro pri ate fields of sci ence so that readers can eas ily iden tify the indi vidual dis cov er ies that re late to the same area. Within each field inven tions are listed chronologically.

Phys i cal Sci ences

Dis cov ery Dis cov er ing Sci en tist Year Page As tron omy Sun-cen tered uni verse Co per ni cus, Nicholaus 1520 5 Plan ets’ true orbits Kep ler, Johannes 1609 11 Other planets have moons Galilei, Ga li leo 1610 13 Distance to the sun Cassini, Giovanni 1672 27 Gal ax ies Herschel, William 1750 36 Wright, Thomas 1750 36 Black hole Schwarzschild, Karl 1916 140 Wheeler, John 1971 141 Ex pand ing uni verse Hub ble, Edwin 1926 150 The Big Bang Gamow, George 1948 185 Qua sar Sandage, Allan 1963 205 Pul sar Bell, Jocelyn 1967 205 Hewish, An tony 1967 205 Dark mat ter Ru bin, Vera 1970 211 Planets around other stars Mayor, Michel 1995 215 Queloz, Didier 1995 215 Uni verse is ac cel er at ing Perlmutter, Saul 1998 218

Chem is try Boyle’s Law Boyle, Robert 1662 19 Ox y gen Priestley, Joseph 1774 43 Elec tro chem i cal bond ing Davy, Humphrey 1806 61 Mol e cules Avogadro, Amedeo 1811 63 Atomic light sig na tures Bun sen, Rob ert 1859 81 Kirchhoff, Rob ert 1859 81

229 230 Ap pen dix 1: Dis cov er ies by Sci en tific Field

Dis cov ery Dis cov er ing Sci en tist Year Page Pe ri odic Ta ble Mendeleyev, Dmitri 1880 90 Ra dio ac tiv ity Cu rie, Ma rie and Pi erre 1901 105 Ra dio ac tive dat ing Boltwood, Bertram 1907 119 Iso topes Soddy, Fred er ick 1913 133

Phys ics Levers and buoyancy Ar chi me des 260 B.C. 3 Law of falling objects Galilei, Ga li leo 1598 9 Air pressure Torricelli, Evangelista 1640 17 Uni ver sal grav i ta tion New ton, Isaac 1666 23 Laws of mo tion New ton, Isaac 1687 31 Na ture of elec tric ity Frank lin, Benjamin 1752 38 Con ser va tion of mat ter Lavoisier, Antoine 1789 47 Nature of heat Rumford, Count 1790 49 In fra red Herschel, Fred er ick 1800 55 Ul tra vi o let Ritter, Johann 1801 55 At oms Dal ton, John 1802 59 Elec tro mag ne tism Oers ted, Hans 1820 65 Cal o rie Joule, James 1843 71 Con ser va tion of en ergy Helmholtz, H. von 1847 73 Dopp ler ef fect Dopp ler, Chris tian 1848 75 Elec tro mag netic ra di a tion Maxwell, James 1864 83 X-rays Roent gen, Wil helm 1895 95 En ergy equa tion Ein stein, Al bert 1905 111 Rel a tiv ity Ein stein, Al bert 1905 114 Su per con duc tiv ity Onnes, Heike 1911 128 Atomic bonding Bohr, Niels 1913 131 Quan tum the ory Born, Max 1925 148 Un cer tainty Prin ci ple Heisenberg, Werner 1927 153 Speed of light Michelson, Albert 1928 155 An ti mat ter Dirac, Paul 1929 160 Neu tron Chadwick, James 1932 163 Strong force Yukawa, Hideki 1937 171 Nu clear fis sion Meitner, Lise 1939 178 Hahn, Otto 1939 178 Semi con duc tor tran sis tor Bardeen, John 1947 183 Def i ni tion of in for ma tion Shan non, Claude 1948 188 Nu clear fu sion Bethe, Hans 1951 192 Spitzer, Lyman 1951 192 Quarks Gell-Mann, Murry 1962 203 Weak force Rubbia, Carlo 1983 171 Ap pen dix 1: Dis cov er ies by Sci en tific Field 231

Earth Sciences

Dis cov ery Dis cov er ing Sci en tist Year Page Gulf Stream Frank lin, Benjamin 1770 40 Humbolt, A. von 1814 41 Ero sion (weath er ing) Hutton, James 1792 51 Ice ages Agassiz, Louis 1837 69 Milankovich, Milutin 1920 70 At mo spheric lay ers de Bort, L. Teisserenc 1902 107 Fault lines Reid, Harry 1911 126 Earth’s core Gutenberg, Beno 1914 136 Con ti nen tal drift Wegener, Al fred 1915 138 Eco sys tem Tansley, Arthur 1935 169 Seafloor spread ing Hess, Harry 1957 199 Chaos theory Lorenz, Ed 1960 201

Life Sciences

Dis cov ery Dis cov er ing Sci en tist Year Page Biology Cells Hooke, Rob ert 1665 21 Fos sils Steno, Nich o las 1669 25 Bac te ria Leeuwenhoek, Anton van 1680 29 Tax on omy sys tem Linnaeus, Carl 1735 33 Pho to syn the sis Ingenhousz, Jan 1779 45 Di no saur fos sils Buck land, Wil liam 1824 67 Mantell, Gid eon 1824 67 Germ the ory Pas teur, Louis 1856 77 Deep-sea life Thomson, Charles 1870 88 Cell di vi sion Flemming, Walther 1882 92 Vi rus Beijerinick, Martinus 1898 101 Ivanovsky, Dmitri 1898 101 Cell structure Claude, Al bert 1933 165 Or i gins of life Miller, Stanley 1952 194 Na ture of di no saurs Bakker, Robert 1976 213 232 Ap pen dix 1: Dis cov er ies by Sci en tific Field

Discovery Dis cov er ing Sci en tist Year Page Evo lu tion and Hu man Anat omy Hu man anat omy Vesalius, Andreas 1543 7 Evo lu tion Dar win, Charles 1858 79 He red ity Men del, Gregor 1865 86 Mi to chon dria Benda, Carl 1898 103 Ge netic mu ta tions Mor gan, Thomas 1909 121 Neurotransmitters Loewi, Otto 1921 144 Walder-Hartz, Hein rich 1921 144 Hu man evo lu tion Dart, Ray mond 1924 146 Coe la canth Smith, J. L. B 1938 176 Jump ing genes McClintock, Barbara 1950 190 DNA Crick, Fran cis 1953 196 Wat son, James 1953 196 Frank lin, Rosalind 1953 197 Com plete evo lu tion Margulis, Lynn 1967 208 Hu man ge nome Venter, Craig 2003 220 Wat son, James 2003 220

Med i cal Sci ence Hu man cir cu la tory sys tem Harvey, William 1628 15 Vac ci na tions Montagu, Lady Mary Wortley 1798 53 Jen ner, Ed ward 1794 53 An es the sia Davy, Humphry 1801 57 Chlo ro form (an es the sia) Simpson, Young 1801 57 Ether (an es the sia) Long, Crawford 1801 58 Blood types Landsteiner, Karl 1897 97 Hor mones Bayliss, William 1902 109 Star ling, Er nest 1902 109 Vi ta mins Hopkins, Fred er ick 1906 117 Eijkman, Christiaan 1906 117 An ti bi ot ics Ehrlich, Paul 1910 124 In su lin Banting, Fred er ick 1921 142 Pen i cil lin Flemming, Al ex an der 1928 158 Genes Bea dle, George 1934 167 Me tab o lism (Krebs Cy cle) Krebs, Hans 1938 174 Blood plasma Drew, Charles 1940 181 Ap pen dix 2: Sci en tists

Ap pen dix 2: Sci en tists Ap pen dix 2: Sci e n tis ts

This table is an alpha beti cal list of the scien tists featured in the dis cussions of the 100 greatest discov er ies. Each is listed with his or her discov ery and the year the discov ery was made.

Name Dis cov ery Year Page Abel, John Hor mones 1898 109 Agassiz, Louis Ice ages 1837 69 Ar chi me des Levers and buoyancy 260 B.C. 3 Avogadro, Amedeo Mol e cules 1811 63 Bakker, Robert Na ture of di no saurs 1976 213 Banting, Fred er ick In su lin 1921 142 Bardeen, John Semi con duc tor tran sis tor 1947 183 Bayliss, William Hor mones 1902 109 Bea dle, George Genes 1934 167 Beijerinick, Martinus Vi rus 1898 101 Bell, Jocelyn Pul sar 1967 205 Benda, Carl Mi to chon dria 1898 103 Bethe, Hans Nu clear fu sion 1939 192 Bohr, Niels Atomic bonding 1913 131 Boltwood, Bertram Ra dio ac tive dat ing 1907 119 Born, Max Quan tum the ory 1925 148 Boyle, Robert Boyle’s law 1662 19 Buck land, Wil liam Di no saur fos sils 1824 67 Bun sen, Rob ert Atomic light sig na tures 1859 81 Cassini, Giovanni Distance to the sun 1672 27 Chadwick, James Neu tron 1932 163 Claude, Al bert Cell structure 1933 165 Co per ni cus, Nicholaus Sun-cen tered uni verse 1520 5 Courtenay-Lati mer, M. Coe la canth 1938 176 Crick, Fran cis DNA 1953 196 Cu rie, Ma rie and Pi erre Ra dio ac tiv ity 1901 105 Dal ton, John At oms 1802 59 Dart, Ray mond Hu man evo lu tion 1924 146 Dar win, Charles Evo lu tion 1858 79 Davy, Humphry An es the sia 1801 57 Davy, Humphry Elec tro chem i cal bond ing 1806 61 de Bort, Leon Teisserenc At mo spheric lay ers 1902 107

233 234 Ap pen dix 2: Sci en tists

Name Dis cov ery Year Page Dirac, Paul An ti mat ter 1929 160 Dopp ler, Chris tian Dopp ler ef fect 1848 75 Drew, Charles Blood plasma 1940 181 Ehrlich, Paul An ti bi ot ics 1910 124 Eijkman, Christiaan Vi ta mins 1906 117 Ein stein, Al bert En ergy equa tion 1905 111 Ein stein, Al bert Rel a tiv ity 1905 114 Galilei, Ga li leo Law of falling objects 1598 9 Galilei, Ga li leo Other planets have moons 1609 11 Gamow, George The Big Bang 1948 185 Gell-Mann, Murry Quarks 1962 203 Gutenberg, Beno Earth’s core 1914 136 Fermi, Enrico Nu clear fis sion 1939 178 Flemming, Al ex an der Pen i cil lin 1928 158 Flemming, Walther Cell di vi sion 1882 92 Frank lin, Benjamin Na ture of elec tric ity 1752 38 Frank lin, Benjamin Gulf Stream 1770 40 Frank lin, Rosalind DNA 1953 197 Hahn, Otto Nu clear fis sion 1939 178 Harvey, William Hu man cir cu la tory sys tem 1628 15 Heisenberg, Werner Un cer tainty Prin ci ple 1927 153 Helmholtz, Hermann von Con ser va tion of en ergy 1847 73 Herschel, Fred er ick In fra red 1800 55 Herschel, William Gal ax ies 1750 36 Hess, Harry Seafloor spread ing 1957 199 Hewish, An tony Pul sar 1967 205 Hodg kin, Dor o thy Pen i cil lin 1942 159 Hooke, Rob ert Cells 1665 21 Hopkins, Fred er ick Vi ta mins 1906 117 Hub ble, Edwin Ex pand ing uni verse 1926 150 Humbolt, Al ex an der von Gulf Stream 1814 41 Hutton, James Ero sion (weath er ing) 1792 51 Ingenhousz, Jan Pho to syn the sis 1779 45 Ivanovsky, Dmitri Vi rus 1898 101 Jen ner, Ed ward Vac ci na tions 1794 53 Joule, James Cal o rie 1843 71 Kep ler, Johannes Plan ets’ true orbits 1609 11 Kirchhoff, Rob ert Atomic light sig na tures 1859 81 Krebs, Hans Me tab o lism (Krebs Cy cle) 1938 174 Landsteiner, Karl Blood types 1897 97 Lavoisier, Antoine Con ser va tion of mat ter 1789 47 Ap pen dix 2: Sci en tists 235

Name Dis cov ery Year Page Lehman, Inge Earth’s core 1938 137 Leeuwenhoek, Anton van Bac te ria 1680 29 Linnaeus, Carl Tax on omy sys tem 1735 33 Long, Crawford Ether (an es the sia) 1801 58 Loewi, Otto Neurotransmitters 1921 144 Lorenz, Ed Chaos theory 1960 201 Mantell, Gid eon Di no saur fos sils 1824 67 Margulis, Lynn Com plete evo lu tion 1967 208 Mayor, Michel Planets around other stars 1995 215 Maxwell, James Elec tro mag netic ra di a tion 1864 83 McClintock, Barbara Jump ing genes 1950 90 Meitner, Lise Nu clear fis sion 1939 178 Men del, Gregor He red ity 1865 86 Mendeleyev, Dmitri Pe ri odic Ta ble 1880 90 Michelson, Albert Speed of light 1928 155 Milankovich, Milutin Ice ages 1920 70 Miller, Stanley Or i gins of life 1952 194 Montagu, Lady Mary Vac ci na tions 1798 53 Mor gan, Thomas Ge netic mu ta tions 1909 121 New ton, Isaac Uni ver sal grav i ta tion 1666 23 New ton, Isaac Laws of mo tion 1687 31 Oers ted, Hans Elec tro mag ne tism 1820 65 Onnes, Heike Su per con duc tiv ity 1911 128 Pas teur, Louis Germ the ory 1856 77 Perlmutter, Saul Uni verse is ac cel er at ing 1998 218 Priestley, Joseph Ox y gen 1774 43 Queloz, Didier Planets around other stars 1995 215 Reid, Harry Fault lines 1911 126 Ritter, Johann Ul tra vi o let` 1801 55 Roent gen, Wil helm X-rays 1895 95 Rubbia, Carlo Weak force 1983 171 Ru bin, Vera Dark mat ter 1970 211 Rumford, Count Na ture of heat 1790 49 Sandage, Allan Qua sar 1963 205 Schwarzschild, Karl Black hole 1916 140 Shan non, Claude Def i ni tion of in for ma tion 1948 188 Sharpey-Schafer, Ed ward Hor mones 1894 109 Simpson, Young Chlo ro form (an es the sia) 1801 57 Smith, J. L. B. Coe la canth 1938 176 Soddy, Fred er ick Iso topes 1913 133 Spitzer, Lyman Nu clear fu sion 1951 193 236 Ap pen dix 2: Sci en tists

Name Dis cov ery Year Page Star ling, Er nest Hor mones 1902 109 Steno, Nich o las Fos sils 1669 25 Takamine, Jokichi Hor mones 1900 109 Tansley, Arthur Eco sys tem 1935 169 Tatum, Edward Genes 1934 167 Thomson, Charles Deep-sea life 1870 88 Torricelli, Evangelista Air pressure 1640 17 Venter, Craig Hu man ge nome 2003 220 Vesalius, Andreas Hu man anat omy 1543 7 Walder-Hartz, Hein rich Neurotransmitters 1888 144 Wat son, James DNA 1953 196 Wat son, James Hu man ge nome 2003 220 Wegener, Al fred Con ti nen tal drift 1915 138 Wheeler, John Black holes 1971 141 Wright, Thomas Gal ax ies 1750 36 Yukawa, Hideki Strong force 1937 171 Ap pen dix 3: The Next 40

Appen dix 3: The Next 40 Appen dix 3: The Next 40

This table is a list of 40 impor tant dis cov eries that al most made the final list of the greatest 100. Each is worthy of consid er ation, honor, and study. Pick one or more of these to re search and describe.

Earth is a sphere Ar is totle 387 B.C. The heavens are not fixed and Brahe 1574 un chang ing The na ture of light Ga li leo, New ton, Young, Ein stein var i ous years Com press ibil ity of gas ses Boyle 1688 Lift/fluid pres sure Bernoulli 1738 Com ets have pre dict able or bits Halley 1758 Hy dro gen Caven dish 1776 Ori gin of the solar system Laplace 1796 Mass of the earth Caven dish 1798 Liquification of gas ses Far a day 1818 Fin ger prints, unique ness of Purkinje 1823 Mag netic in duc tion Far a day 1831 Age of the sun Helmholtz 1853 Sun is a gas Car ring ton 1859 Age of the earth Lyell (first), Holmes (ac cu rate) 1860, 1940 An ti sep tics Lis ter 1863 Plas tics Hyatt 1869 Al ter nat ing cur rent Tesla 1883 Bac te ri ol ogy Koch 1890 Earth’s mag netic field re ver sals Brunhes 1906 Che mo ther apy Ehrlich 1906 Cos mic ra di a tion Hess 1911 Elec tro en ceph a lo gram Berger 1924 adjustrightBrucellosis bac te rium Ev ans 1925 Ex clu sion prin ci ple Pauli 1926 Neu trino Pauli 1926 Gal ax ies emit ra dio waves Jansky 1932 Ar ti fi cial ra dio ac tiv ity Curie and Joliot 1934 Cor ti sone Kend all 1935 Sulfa drugs Domagk 1936 Ra di a tion ther apy Priore 1950 La ser Townes and Gould 1954/1957 237 238 Ap pendix 3: The Next 40

Global warming Many late twen ti eth cen tury First clon ing Gurden 1967 Laetoli foot prints (3.5 mil lion Mary Leakey 1973 years old) ”Lucy” (3.2 million-year-old Don ald John son 1974 skull) Non-oxy gen-based deep sea life Ballard 1977 Di no saur ex tinc tion (K-T Alvarez 1979 as ter oid) Hu man retro virus HIV Gallo and Montagnier 1982 Toumai skull (6 to 7 million years Michel Brunet 2002 old) In dex

In dex In dex

Ab so lute zero tem per a ture An ti mat ter. See also Mat ter superconductivity, 128–29 E = mc2, 112 Ac cel er at ing uni verse importance of, 160 importance of, 218 origins of discovery, 160–61 origins of discovery, 218–19 Apes Ace tyl cho line human evolution, 146 neurotransmitters, 145 Ar chi me des Ach ro matic mi cro scope levers and buoyancy, 3–4 mitochondria, 103 Ar is totle Adren a line, 109 Jupiter’s moons, 13 Agassiz, Louis law of falling objects, 9–10 ice ages, 69–70 laws of motion, 31 Ag glu ti na tion, 99 Ar ter ies Air pressure circulatory system, 15–16 importance of, 17 As trol ogy origins of discovery, 17–18 distance to the sun, 27 Al gae As tron omy. See also Big Bang the ory; Black complete evolution, 209 holes; Ex pand ing uni verse; Gal ax ies; Amino acids. See also Tryptophan Or igins of life; Solar sys tem; Speed origins of life, 194–95 of light; Sun-centered universe vitamins, 118 dark matter, 211–12 An aer o bic pro cess distance to the sun, 27–28 metabolism, 174–75 Doppler Effect, 75–76 Anatomy. See Com par a tive anat omy; Hu man electromagnetic radiation/radio waves, 83 anat omy existence of planets around other stars, An es the sia 215–16 definition of, 57 Infrared (IR) and ultraviolet (UV) light, importance of, 57 55–56 origins of discovery, 57–58 planetary motion, 11–12 An i mals. See also Eco sys tems; Plants quasars and pulsars, 205–6 coelacanth, 176–77 At mo sphere. See also Ice ages; Na ture of the continental drift, 138 at mo sphere; Oceans, ef fects on deep-sea life, 88–89 weather; Ox y gen; Weather order in nature, 33–34 air pressure, 17–18 theory of evolution, 79–80 matter, 47–48 An thro pol ogy origins of life, 194–95 theory of evolution, 79 photosynthesis, 45 An ti bi ot ics At mo spheric lay ers importance of, 124 importance of, 107 origins of discovery, 124–25 origins of discovery, 107–8 penicillin, 158–59 Atomic bonding importance of, 131 origins of discovery, 131–32

239 240 In dex

Atomic en ergy Bayliss, William fusion, 192–93 hormones, 109–10 isotopes, 133–34 Bea dle, George Atomic light signa tures genes, function of, 167–68 importance of, 81 Beijerinick, Martinus origins of discovery, 81–82 viruses, 101–2 Atomic weight Bell, Jocelyn. See also Sandage, Allan Rex isotopes, 133–34 pulsars, 205–6 Periodic Chart of the Elements, 90–91 Benda, Carl At oms. See also Big Bang theory; mitochondria, 103–4 Elec tro chem i cal bond ing; Elec trons; Be ryl lium Ex is tence of cells; Hy dro gen bomb; neutrons, 164 Iso topes; Mol e cules; Neu trons; Nu clear Big Bang theory. See also Ac cel er at ing bomb; Nu clear fis sion; Ra dio ac tiv ity; uni verse Sub atomic par ti cles; Uncertainty expanding universe, 150 Principle importance of, 185 Boyle’s Law, 19 origins of discovery, 185–86 importance of, 59 Bi no mial sys tem, 34 origins of discovery, 59–60 Bio chem i cal ge net ics weak and strong force, 171–72 genes, function of, 167–68 ATP Bi ol ogy. See also Com plete evo lu tion; metabolism, 175 Ex is tence of cells; Mi cro bi ol ogy; Avogadro, Amedeo Mo lec u lar bi ol ogy; Or i gins of life Avogadro’s Number, 63 cell division, 92–93 molecules, 63–64 cell structure, 165–66 chromosomes, function of, 121–22 Bac te ria. See also An ti bi ot ics; Or i gins of life; coelacanth, 176–77 Pen i cil lin; Viruses ecosystems, 169–70 complete evolution, 209 “jumping genes,” 191 germ theory, 77–78 order in nature, 33–34 importance of, 29 theory of evolution, 79–80 origins of discovery, 29–30 Birds Bakker, Robert nature of dinosaurs, 213 nature of dinosaurs, 213–14 “Bit of scruff,” 206 Bal loons Black holes atmospheric layers, 107 importance of, 140 Band width origins of discovery, 140–41 definition of information, 189 quasars and pulsars, 206 Banting, Fred er ick “Black re action,” 103 insulin, 142–43 Blood cells, 29 Bardeen, John Blood plasma semiconductor transistor, 183–84 importance of, 181 Bar ium origins of discovery, 181–82 nuclear fission, 178–79 Blood sugar Ba rom e ter. See also At mo sphere; Weather insulin, 142–43 air pressure, 17 Blood trans fu sions atmospheric layers, 107–8 plasma, 181–82 Bat ter ies Blood types electrochemical bonding, 62 importance of, 97 electricity, 38 origins of discovery, 97–98 “Voltaic Pile,” 62 In dex 241

Bohr, Niels Car bon di ox ide. See also Ox y gen; atomic bonding, 131–32 Pho to syn the sis Boltwood, Bertram electrochemical bonding, 61–62 radioactive dating, 119–20 metabolism, 175 Bond ing. See Atomic bond ing; Elec tro chem i cal Cassini, Giovanni bond ing Cassini gaps, 27 Bone structure distance to the sun, 27–28 nature of dinosaurs, 214 Catastrophism Boolean logic erosion of Earth’s surface, 51 definition of information, 188 Cath ode rays Born, Max electrons, 101–2 quantum theory, 148–49 Cell di vi sion Bot any importance of, 92 order in nature, 33–34 origins of discovery, 92–93 Boyle, Robert Cell struc ture Boyle’s Law, 19–20 importance of, 165 Boyle’s Law origins of discovery, 165–66 importance of, 19 Cells. See Blood cells; Com plete evolu tion; origins of discovery, 19–20 Ex istence of cells; Genes; Brahe, Tycho Mi cro bi ol ogy; Mi to chon dria; planetary motion, 11–12 Neurotransmitters; Viruses Brain func tion Cen tri fuge neurotransmitters, 144–45 cell structure, 166 Brown dwarfs Chadwick, James existence of planets around other stars, neutrons, 163–64 215–16 Chaos theory Bub ble cham ber, 203–4 nature of the atmosphere, 201–2 Buck land, Wil liam Chart of the El e ments. See Pe ri odic Chart of dinosaur fossils, 67–68 the El e ments Bun sen, Rob ert Chem i cal com pounds atomic light signatures, 81–82 antibiotics, 124–25 Bunsen burner, 82 isotopes, 133–34 Buoy ancy. See also Le vers vitamins, 117–18 definition of, 3 Chem i cal mes sen gers. See Hor mones; importance of, 4 Neurotransmitters origins of discovery, 3–4 Chem is try. See also Elec tro chem i cal bond ing; Elec tro chem is try; Cal cu lus, 31–32 Neurotransmitters; Pe ri odic Chart of Ca lo ric, 49–50 the El e ments; Photochemistry Cal o ries atoms, 59–60 as units of energy, 71 Big Bang theory, 186 importance of, 71 Boyle’s Law, 19 origins of discovery, 71–72 isotopes, 133–34 vitamins, 117–18 matter, 47 Can cer re search Che mo ther apy cell structure, 165–66 antibiotics, 124–25 Cap il lar ies, 29 Chlo ro form, 57 Car bon Chro matic ab er ra tion, 103 metabolism, 175 Chromatin, 93 radioactive dating, 120 242 In dex

Chro mo somes Core and mantle. See Earth’s core and cell division, 92–93 man tle cell structure, 166 Corn research function of, 121–23 “jumping genes,” 190–91 heredity, 86 human genome, 221 Cor pus cu lar the ory of mat ter “jumping genes,” 190–91 fossils, 26 Cir cu la tory sys tem Cor ti sone, 110 importance of, 15 “Cosmic egg,” 185 origins of discovery, 15–16 “Cos mo log i cal con stant,” 218 Cit ric acid Coun cil of Car di nals metabolism, 175 Jupiter’s moons, 14 Claude, Albert Court room ev i dence cell structure, 165–66 DNA, 196 Cli mate. See At mo spheric lay ers; Oceans, Crick, Fran cis ef fects on weather DNA, 196–97 Clouds Crookes’ tube atmospheric layers, 107 X-rays, 95–96 Coe la canth Cu rie, Ma rie importance of, 176 radioactivity, 105–6 origins of discovery, 176–77 “Cur va ture of space, the” Com bus tion, 43–44, 49 black holes, 140 Com mu ni ca tion Cy to plasm neurotransmitters, 144–45 mitochondria, 103–4 Com par a tive anat omy nature of dinosaurs, 213 Dal ton, John Com plete evo lu tion atoms, 59–60 importance of, 208 “Dark energy,” 219 origins of discovery, 208–9 Dark matter Com pounds. See Chem i cal com pounds; importance of, 211 In or ganic com pounds origins of discovery, 211–12 Com put ers Dart, Raymond definition of information, 188–89 human evolution, 146–47 human genome, 221 Dar win, Charles. See also Com plete evo lu tion Con duc tiv ity. See Semi con duc tor tran sis tor; dinosaur fossils, 67 Su per con duc tiv ity heredity, 86 Con ser va tion of en ergy human evolution, 146–47 contradictions, 112 theory of evolution, 79–80, 121 importance of, 73 Dat ing. See Ra dio ac tive dat ing origins of discovery, 73–74 Davy, Humphry Con ser va tion of mass anesthesia, 57–58 contradictions, 112 electrochemical bonding, 61–62 Con ti nen tal drift. See also Earth’s core and De cay. See Ra dio ac tive de cay man tle; Plate tec ton ics; Seafloor Decomposers spread ing ecosystems, 170 importance of, 138 Deep-sea life origins of discovery, 138–39 importance of, 88 Co per ni cus, Nicholaus origins of discovery, 88–89 Jupiter’s moons, 13–14 Def i ni tion of in for ma tion planetary motion, 11 importance of, 188 sun-centered universe, 5–6 origins of discovery, 188–89 In dex 243

Democritus Dopp ler Ef fect Boyle’s Law, 19 Doppler shift, 76 Den sity importance of, 75 atmospheric layers, 107–8 origins of discovery, 75–76 Big Bang theory, 185–86 Doppler shift, 76 black holes, 140–41 accelerating universe, 219 buoyancy, 4 dark matter, 212 Earth’s core and mantle, 136–37 existence of planets around other stars, 215–16 nature of the atmosphere, 202 quasars and pulsars, 205 quasars and pulsars, 205–6 Dou ble he lix model De oxy ri bo nu cleic Acid (DNA). See also DNA, 197 Human genome; mDNA; Ori gins of life; human genome, 220–21 Ri bo nu cleic Acid (RNA) Drew, Charles chromosomes, function of, 121 blood plasma, 181–82 complete evolution, 208 genes, function of, 167–68 E = mc2 heredity, 86–87 black holes, 140 importance of, 196 fusion, 192 mitochondria, 103–4 importance of, 111 origins of discovery, 196–97 origins of discovery, 111–12 Depths of the Sea, The, 89 speed of light, 155 De tri tus, 89 Earth’s core and man tle. See also Di a be tes Con ti nen tal drift; Plate tec ton ics; insulin, 142–43 Seafloor spreading Di etary health. See also Nu tri tion importance of, 136 vitamins, 117–18 origins of discovery, 136–37 Dif frac tion pat terns Earth quakes. See Fault lines Earth’s core and mantle, 137 Ecol ogy Di ges tive juices nature of dinosaurs, 213 insulin, 142–43 theory of evolution, 79–80 Dig i tal tech nol ogy. See also Com put ers Eco sys tems definition of information, 188 importance of, 169 Di no saur fos sils. See also Na ture of di no saurs nature of dinosaurs, 213 importance of, 67 order in nature, 33 origins of discovery, 67–68 origins of discovery, 169–70 Dirac, Paul “Ed ding ton’s equa tions,” 160 antimatter, 160–62 Ehrlich, Paul Dis eases. See An ti bi ot ics; Bac te ria; antibiotics, 124–25 De oxy ri bo nu cleic Acid (DNA); Hu man Eijkman, Christiaan ge nome; “Jump ing genes”; Pen i cil lin; vitamins, 117–18 Vac ci na tions; Viruses; Vitamins Ein stein, Al bert Dis sec tions E = mc2, 111–13 circulatory system, 15 theory of relativity, 114–16 human anatomy, 7–8 Elec tri cal cur rents Dis tance to the sun antimatter, 160–61 importance of, 27 neurotransmitters, 144–45 origins of discovery, 27–28 neutrons, 163 DNA. See Deoxyribonucleic Acid (DNA) semiconductor transistor, 183–84 Dopp ler, Chris tian Elec tri cal en ergy Doppler Effect, 75–76 semiconductor transistor, 183–84 superconductivity, 128–29 244 In dex

Elec tri cal fields El e ments. See Pe ri odic Chart of the electromagnetic radiation/radio waves, 84 El e ments; Iso topes; Ra dio ac tive Elec tri cal re sis tance dat ing; Trace elements semiconductor transistor, 183–84 El lip ses. See also Epi-cir cles superconductivity, 128–29 definition of, 12 Elec tric ity. See also Su per con duc tiv ity laws of motion, 31 conservation of energy, 74 planetary motion, 11–12 electromagnetic radiation/radio waves, En do cri nol ogy 83–84 hormones, 109–10 electromagnetism, 65–66 En ergy. See An ti mat ter; Cal o ries; electrons, 101 Con ser va tion of en ergy; “Dark importance of, 38 en ergy;” Fis sion; Fu sion; Ki netic origins of discovery, 38–39 en ergy; Me tab o lism; Nu clear fis sion; Elec tro chem i cal bond ing Solar energy importance of, 61 Energy and matter origins of discovery, 61–62 antimatter, 161 Elec tro chem is try E = mc2, 111–12 infrared (IR) and ultraviolet (UV) light, 56 theory of relativity, 115 metabolism, 175 En zymes Elec trodes, 62 genes, function of, 167–68 Elec tro lytes, 62 metabolism, 175 Elec tro mag netic ra di a tion/ra dio waves Epi-cir cles. See also El lip ses importance of, 83 planetary motion, 11–12 origins of discovery, 83–84 sun-centered universe, 5–6 quasars and pulsars, 206 Epi neph rine, 109 Elec tro mag ne tism Erosion of Earth’s surface electrons, 102 importance of, 51 importance of, 65 origins of discovery, 51–52 origins of discovery, 65–66 Es cape ve loc ity weak and strong force, 171–72 black holes, 141 Elec tron mi cro scope Ether, 58 atoms, 59 Event ho ri zon cell structure, 165–66 black holes, 141 viruses, 97–98 Evo lu tion. See Com plete evo lu tion; Hu man Elec tronic cir cuits evo lu tion; The ory of evo lu tion definition of information, 188 Ex is tence of cells Elec trons. See also Atomic bonding; cell, definition of, 22 Pro ton-elec trons; Pro tons; importance of, 21 Su per con duc tiv ity; Un cer tainty Principle origins of discovery, 21–22 antimatter, 160–61 Exis tence of planets around other stars atoms, 59–60 importance of, 215 Big Bang theory, 186 origins of discovery, 215–16 electrochemical bonding, 61–62 Ex pand ing uni verse importance of, 101 Big Bang theory, 185–86 isotopes, 134 importance of, 150 neutrons, 163 origins of discovery, 150–51 origins of discovery, 101–2 Ex per i ments Upon Veg e ta bles, 46 quantum theory, 148–49 El e men tary par ti cles Fall ing ob jects. See Law of falling objects; antimatter, 161 Laws of motion Uncertainty Principle, 153 In dex 245

Fault lines. See also San Andreas fault Galen importance of, 126 circulatory system, 15 origins of discovery, 126–27 human anatomy, 7–8 Field data Galilei, Ga li leo ice ages, 69 air pressure, 17 Fis sion. See also Fu sion; Nu clear fis sion Jupiter’s moons, 13–14 radioactive dating, 119 law of falling objects, 9–10 Fixed-or der lines laws of motion, 31 chromosomes, function of, 122 sun-centered universe, 6 Flem ing, Al ex an der Gamma rays. See also X-rays penicillin, 158–59 electromagnetic radiation/radio waves, 83 Flemming, Walther infrared (IR) and ultraviolet (UV) light, cell division, 92–94 55 “Fly Room, The,” 121 isotopes, 134 Food Gamow, George metabolism, 174–75 Big Bang theory, 185–86 vitamins, 117–18 Gas. See also Ni trous ox ide; Ox y gen Force. See also Weak and strong force anesthesia, 58 laws of motion, 31–32 atomic light signatures, 81–82 Fos sils. See also Coe la canth; Con ti nen tal drift; Boyle’s Law, 19–20 Di no saur fos sils; Ge ol ogy; Hu man electrochemical bonding, 61 evo lu tion; Na ture of di no saurs; Or i gins matter, 47 of life molecules, 63–64 definition of, 25 nature of the atmosphere, 202 importance of, 25 origins of life, 195 “living fossil,” 176–77 Gei ger coun ter, 120 origins of discovery, 25–26 Gell-Mann, Murry seafloor spreading, 200 quarks, 203–4 Frac tion ation Gen er a tors cell structure, 165–66 electricity, 38 Frank lin, Benjamin Genes. See also “Jump ing genes” electricity, 38–39 chromosomes, function of, 121 oceans, effects on weather, 40–42 function of, 167–68 Fric tion importance of, 167 nature of heat, 49–50 origins of discovery, 167–68 Fun da men tals of Ecol ogy, 170 Ge net ics. See Bio chem i cal ge net ics; Fu sion. See also Fis sion Chro mo somes; Com plete evo lu tion; importance of, 192 Heredity origins of discovery, 192–93 Ge nome. See Hu man ge nome Ge ol ogy, 26, 52. See also Con ti nen tal drift; Gal ax ies Fault lines; Fos sils; Ice ages; accelerating universe, 218–19 Iso topes; Ra dio ac tive dating atomic light signatures, 81–82 Geo phys ics dark matter, 212 Earth’s core and mantle, 136–37 Doppler Effect, 75–76 Germ theory. See also Viruses expanding universe, 150–51 importance of, 77 existence of planets around other stars, 216 origins of discovery, 77–78 importance of, 36 Ger ma nium, 183–84 origins of discovery, 36–37 Gla ciers quasars and pulsars, 206 ice ages, 69–70 weak and strong force, 171–72 246 In dex

Grav i ta tion. See Ac cel er at ing uni verse; Air Hopkins, Fred er ick pres sure; Con ser va tion of en ergy; Law vitamins, 117–18 of falling objects; Laws of motion; Homo sa pi ens, 33 Quasars and pulsars; Theory of Hor mones. See also In su lin rel a tiv ity; Uni ver sal grav i ta tion; Weak importance of, 109 and strong force origins of discovery, 109–10 Grav i ta tional pull Hub ble, Edwin accelerating universe, 218–19 expanding universe, 150–52 black holes, 140–41 Hu man anat omy. See also Cir cu la tory existence of planets around other stars, 215 system; Exis tence of cells; Fos sils Gravitons genes, function of, 168 weak and strong force, 172 importance of, 7 Gulf Stream, 40–41 metabolism, 174–75 Gutenberg, Beno origins of discovery, 7–8 Earth’s core and mantle, 136–37 vitamins, 117–18 Guyots, 199–200 Hu man evo lu tion importance of, 146 Half-life origins of discovery, 146–47 radioactive dating, 119 Hu man ge nome Harvey, Wil liam DNA, 196 circulatory system, 15–16 importance of, 220 Health. See Di etary health origins of discovery, 220–21 Heart Hu man spe cies circulatory system, 15 DNA, 196–97 Heat. See also Na ture of heat; order in nature, 33 Ther mo dy nam ics Hu man oids atomic light signatures, 81–82 human evolution, 147 calories, 71–72 Hu mid ity conservation of energy, 74 atmospheric layers, 107–8 fusion, 192–93 Hutton, James metabolism, 174 erosion of Earth’s surface, 51–52 semiconductor transistor, 183–84 Hy dro gen bomb Heisenberg, Werner fusion, 192–93 Uncertainty Principle, 153–54 He lium. See Liq uid he lium Ice ages He red ity. See also Genes; Human ge nome importance of, 69 cell division, 92–93 origins of discovery, 69–70 importance of, 86 Ig uano don, 68 origins of discovery, 86–87 Im mune sys tem Herschel, Fred er ick antibiotics, 124–25 Infrared (IR) light, 55–56 In fec tions. See An ti bi ot ics; Bac te ria; Herschel, Wil liam Dis eases; Pen i cil lin; Vac ci na tions; galaxies, 36–37 Viruses Hess, Harry In flu enza seafloor spreading, 199–200 penicillin, 159 Hewish, Antony. See also Bell, Jocelyn In for ma tion. See Def i ni tion of in for ma tion pulsars, 205–6 In for ma tion Age Hooke, Robert definition of information, 188 existence of cells, 21–22 In for ma tion streams definition of information, 189 In dex 247

In fra red (IR) and ul tra vi o let (UV) light Lat i tu di nal zonation importance of, 55 nature of dinosaurs, 213 origins of discovery, 55–56 Lavoisier, Antoine Ingenhousz, Jan matter, 47–48 photosynthesis, 45–46 Law of falling objects. See also Plan e tary In graft ing, 53 mo tion; Uni ver sal grav i ta tion In or ganic com pounds importance of, 9 origins of life, 194–95 origins of discovery, 9–10 In su lin Laws of motion. See also Dark matter; importance of, 142 Plan e tary mo tion; Uni ver sal origins of discovery, 142–43 grav i ta tion Iso topes importance of, 31 importance of, 133 origins of discovery, 31–32 origins of discovery, 133–34 Lead. See also Ura nium radioactive dating, 119–20 radioactive dating, 120 Ivanovsky, Dmitri Leeuwenhoek, Anton van viruses, 101–102 bacteria, 29–30 Le vers. See also Buoyancy Jen ner, Ed ward. See also Montagu, Lady Mary definition of, 3 Wortley importance of, 3 vaccinations, 53–54 origins of discovery, 3–4 Joule, James Life. See Or i gins of life calories, 71–72 Light. See also Dark matter; E = mc2; “Jump ing genes” In fra red (IR) and ul tra vi o let (UV) importance of, 190 light; Speed of light origins of discovery, 190–91 accelerating universe, 218–19 Ju pi ter’s moons atomic light signatures, 81 importance of, 13 black holes, 140–41 origins of discovery, 13–14 conservation of energy, 74 deep-sea life, 88–89 Kel vin, Lord electricity, 38 fusion, 192 existence of planets around other stars, superconductivity, 128 215–16 Kep ler, Johannes quasars and pulsars, 205–6 distance to the sun, 27 semiconductor transistor, 183–84 laws of motion, 31 Light, space, and time planetary motion, 11–12 black holes, 140–41 sun-centered universe, 6 E = mc2, 111–12 Ki netic en ergy theory of relativity, 114–15 conservation of energy, 73–74 Light waves Kirchhoff, Gustav Doppler Effect, 75–76 atomic light signatures, 81–82 Light years Krebs, Hans Adolf quasars and pulsars, 206 metabolism, 174–75 speed of light, 155–56 Light ning Lac tic acid electricity, 38–39 metabolism, 174–75 lightning rod, 39 Landsteiner, Karl Linnaeus, Carl blood types, 97–98 order in nature, 33–35 Liq uid he lium superconductivity, 129 248 In dex

Liq uid mer cury importance of, 47 air pressure, 17 laws of motion, 31–32 Boyle’s Law, 20 origins of discovery, 47–48 superconductivity, 129 oxygen, 43 Loewi, Otto photosynthesis, 46 neurotransmitters, 144–45 quarks, 203–4 Log a rithms Maxwell, James Clerk planetary motion, 12 electromagnetic radiation/radio waves, 83–85 Lorenz, Ed Mayor, Michel nature of the atmosphere, 201–2 existence of planets around other stars, Lungs 215–16 circulatory system, 15 McClintock, Barbara “jumping genes,” 190–91 “Magic bullet,” 125 mDNA Magma mitochondria, 104 seafloor spreading, 200 Mea sure ment Mag netic fields accelerating universe, 219 fusion, 193 antimatter, 161 Mag ne tism. See also Elec tro mag netic Big Bang theory, 185–86 ra di a tion/ra dio waves; Elec tro mag ne tism Doppler Effect, 76 conservation of energy, 74 E = mc2, 112 electrons, 101–2 existence of planets around other stars, Mantell, Gideon 215–16 dinosaur fossils, 67–68 fusion, 192–93 Man tle. See Earth’s core and man tle matter, 47–48 Margulis, Lynn speed of light, 155–56 complete evolution, 208–9 Med i cine Ma rine sci ence anesthesia, 57–58 coelacanth, 177 human anatomy, 7–8 Math e mat ics. See also Non lin ear model Megalosaurus, 68 equa tions Meitner, Lise accelerating universe, 218–19 nuclear fission, 178–80 antimatter, 160–61 Men del, Gregor Big Bang theory, 186 heredity, 86–87 definition of information, 188–89 Mendeleyev, Dmitri E = mc2, 111–12 Periodic Chart of the Elements, 90–91 fusion, 192–93 Mer cury. See Liquid mercury nature of the atmosphere, 201–2 Mesons. See also Pi-mesons quantum theory, 148 weak and strong force, 172 superconductivity, 129 Me tab o lism theory of relativity, 114 importance of, 174 Uncertainty Principle, 153–54 origins of discovery, 174–75 Ma trix me chan ics Me te o rol ogy. See At mo sphere; At mo spheric Uncertainty Principle, 153–54 lay ers; Ba rom e ter; Oceans, ef fects on Mat ter. See also Anti mat ter; Dark mat ter; E = weather; Weather mc2; Energy and matter Michelson, Al bert atoms, 59–60 speed of light, 155–56 Big Bang theory, 185–86 Mi cro bi ol ogy conservation of, 47–48 bacteria, 29–30 definition of information, 188–89 mitochondria, 103–4 fusion, 192–93 germ theory, 78 In dex 249

Mi cro or gan isms Mo tion. See also Black holes; Dark mat ter; antibiotics, 124–25 Law of falling objects; Laws of germ theory, 77–78 mo tion; Mo men tum; Un cer tainty Mi cro scopes. See also Ach ro matic mi cro scope; Prin ci ple An ti bi ot ics; Elec tron mi cro scope; accelerating universe, 218–19 Telescopes nature of heat, 50 bacteria, 29–30 nature of the atmosphere, 202 cell division, 92–93 quasars and pulsars, 205–6 existence of cells, 21 seafloor spreading, 199–200 dark matter, 211 Mo tors fossils, 26 electricity, 38 “jumping genes,” 191 electromagnetism, 65 mitochondria, 103 Mus cles quantum theory, 148–49 metabolism, 174–75 viruses, 97–98 Mu ta tions Mi cro scopic or gan isms chromosomes, function of, 121–22 antibiotics, 124 complete evolution, 208–9 germ theory, 77–78 genes, function of, 168 Mi cro waves “jumping genes,” 191 infrared (IR) and ultraviolet (UV) light, 55 Milky Way, 36 Napier, John Miller, Stanley planetary motion, 12 origins of life, 194–95 Nat u ral se lec tion “Mind (or thought) exper i ments” complete evolution, 208–9 Einstein, Albert, 111, 115 theory of evolution, 80 “Missing link,” 147 Natu ral ist’s Voyage on the Beagle, A Mi to chon dria. See also Cell struc ture; Complete theory of evolution, 80 evo lu tion Na ture. See Order in nature importance of, 103 Na ture of di no saurs origins of discovery, 103–4 importance of, 213 Mi to sis. See Cell di vi sion origins of discovery, 213–14 Mold Na ture of heat genes, function of, 168 importance of, 49 penicillin, 159 origins of discovery, 49–50 Mo lec u lar bi ol ogy Nature of the atmo sphere DNA, 196–97 importance of, 201 Mol e cules. See also At oms; Pro tein mol e cules origins of discovery, 201–2 definition of, 64 Neo sal var san DNA, 196–97 antibiotics, 125 importance of, 63 Neu rons, 144–45 origins of discovery, 63–64 Neurospora X-rays, 95 genes, function of, 167 Mo men tum Neurotransmitters conservation of energy, 74 importance of, 144 Montagu, Lady Mary Wortley. See also Jen ner, origins of discovery, 144–45 Ed ward Neu tri nos vaccinations, 53–54 antimatter, 161 Moons. See Ju pi ter’s moons Neutron star, 206 Morgan, T. H. chromosomes, function of, 121–23 250 In dex

Neu trons. See also Elec trons; Pro tons; Quarks Order in nature antimatter, 161 importance of, 33 Big Bang theory, 186 origins of discovery, 33–34 importance of, 163 Organelles isotopes, 134 cell structure, 166 origins of discovery, 163–64 mitochondria, 103 weak and strong force, 172 Or i gin of Spe cies New ton, Isaac theory of evolution, 80 air pressure, 17 Or i gins of life law of falling objects, 9 importance of, 194 laws of motion, 31–32 origins of discovery, 194–95 universal gravitation, 23–24 Orig i nal The ory on New Hy poth e sis of the Ni tro gen cy cle Uni verse, An, 37 ecosystems, 169 Ox i da tion Ni trous ox ide nature of heat, 49 anesthesia, 58 Ox y gen. See also Gas; Pho to syn the sis electrochemical bonding, 61 atmospheric layers, 107 Non lin ear model equa tions importance of, 43 nature of the atmosphere, 202 metabolism, 174–75 Nu clear bomb origins of discovery, 43–44 Big Bang theory, 186 E = mc2, 111–12 Pa le on tol ogy. See also An thro pol ogy; fission, 179 Na ture of di no saurs neutrons, 163 dinosaur fossils, 67 Nu clear en ergy theory of evolution, 79 E = mc2, 111–12 Pan creas fission, 178–79 insulin, 142 fusion, 192–93 Pangaea, 139 quantum theory, 148–49 Par ti cle phys ics. See also El e men tary speed of light, 156 par ti cles; Sub atomic par ti cles Nu clear fis sion electrons, 101–2 importance of, 178 Pas teur, Louis origins of discovery, 178–79 bacteria, 30 Nu cleus. See also Atomic bonding; Cell germ theory, 77–78 struc ture; Cells Pas teur iza tion, 77–78 isotopes, 133–34 Pen i cil lin mitochondria, 103 antibiotics, 124 neutrons, 163–64 importance of, 158 Uncertainty Principle, 153 origins of discovery, 158–59 Nu tri tion Pe ri odic Chart of the El e ments vitamins, 117–18 importance of, 90 isotopes, 133 Oceans, ef fects on weather. See also Deep-sea origins of discovery, 90–91 life Perlmutter, Saul importance of, 40 accelerating universe, 218–19 origins of discovery, 40–41 Phar ma col ogy Oers ted, Hans antibiotics, 124–25 electromagnetism, 65–66 neurotransmitters, 145 Onnes, Heike Kamerlingh Phlogiston, 49 superconductivity, 128–30 Phos phates metabolism, 175 In dex 251

Photochemistry Plate tec ton ics. See also Con ti nen tal drift; atomic light signatures, 82 Seafloor spreading Pho tons fault lines, 126–27 E = mc2, 111 Po lo nium, 105–6 Pho to syn the sis. See also Ox y gen; Plants Pos i trons importance of, 45 antimatter, 161 origins of discovery, 45–46 Po tas sium Phys ics. See also Atomic bonding; E = mc2; electrochemical bonding, 61–62 En ergy and mat ter; Geo phys ics; Par ti cle Priestley, Jo seph phys ics; Quan tum phys ics; Quan tum oxygen, 43–44 theory; Speed of light; Theory of Principia, 32 rel a tiv ity; Un cer tainty Principle Prism antimatter, 160–61 atomic light signatures, 82 atoms, 59–60 Pro tein mol e cules Big Bang theory, 185–86 vitamins, 118 dark matter, 211–12 Pro ton-elec trons electromagnetic radiation/radio waves, neutrons, 163–64 83–84 Pro tons. See also Elec trons; Quarks isotopes, 133–34 antimatter, 160–61 nuclear fission, 178–79 Big Bang theory, 186 radioactivity, 105–6 isotopes, 133–34 superconductivity, 128–29 nuclear fission, 178–79 weak and strong force, 171–72 quantum theory, 148–49 Phys i ol ogy. See An ti bi ot ics; Cir cu la tory Uncertainty Principle, 153 sys tem; Hor mones; Hu man anat omy; weak and strong force, 171–72 Vitamins Pro to zoa, 29 Pi-mesons Ptol emy weak and strong force, 172 Jupiter’s moons, 13 Pis tons law of falling objects, 9 Boyle’s Law, 19–20 Ptolemy’s model, 5–6 Pitch blende, 105 Pul sars. See Quasars and pulsars Plague Pure air. See also Ox y gen vaccinations, 53–54 matter, 47 Plan e tary mo tion. See also Gal ax ies; Law of fall ing objects; Laws of mo tion Quanta importance of, 11 atomic bonding, 132 origins of discovery, 11–12 E = mc2, 111 tables of calculations, 12 Quan tum elec tro dy nam ics Plan ets. See Exis tence of planets around other antimatter, 160 stars Quan tum me chan ics Plants. See also Al gae; An i mals; Eco sys tems; antimatter, 160–61 Pho to syn the sis quantum theory, 148–49 bacteria, 29 Quan tum phys ics complete evolution, 209 antimatter, 160 continental drift, 138 strangeness, 204 deep-sea life, 88–89 weak and strong force, 171 order in nature, 33–34 Quan tum the ory radioactive dating, 119–20 Big Bang theory, 186 theory of evolution, 79–80 importance of, 148 Plasma. See Blood plasma origins of discovery, 148–49 superconductivity, 129 252 In dex

Quarks Rubbia, Carlo importance of, 203 weak force, 171–72 origins of discovery, 203–4 Ru bin, Vera weak and strong force, 172 dark matter, 211–12 Quasars and pulsars Rumford, Count importance of, 205 nature of heat, 49–50 origins of discovery, 205–6 Queloz, Didier San Andreas fault, 127 existence of planets around other stars, Sandage, Allan Rex 215–16 quasars, 205–6 Schwarzschild, Karl Ra di a tion. See Atomic bonding; Big Bang black holes, 140–41 the ory; Dark mat ter; Elec tro mag netic Seafloor spreading ra di a tion/ra dio waves; In fra red (IR) and importance of, 199 ul tra vi o let (UV) light; Solar radiation origins of discovery, 199–200 Ra di a tion sick ness, 105 Secretin, 110 Ra dio ac tive dat ing. See also Iso topes Sed i men ta tion importance of, 119 fossils, 26 origins of discovery, 119–20 Seis mic waves Ra dio ac tive de cay Earth’s core and mantle, 137 nuclear fission, 178 Seis mol ogy. See also Fault lines; Ge ol ogy weak and strong force, 171 Earth’s core and mantle, 136–37 Ra dio ac tiv ity Semi con duc tor tran sis tor importance of, 105 importance of, 183 origins of discovery, 105–6 origins of discovery, 183–84 polonium, 105–6 Sex ual re pro duc tion radium, 105–6 order in nature, 34 splitting of the atom, 105–6 Shadow zone, 136 Ra dio sig nals Shan non, Claude quasars and pulsars, 205–6 definition of information, 188–89 Ra dio waves. See Elec tro mag netic Ship ping ra di a tion/ra dio waves oceans, effects on weather, 41 Ra dium, 105–6 Smith, J. L. B. Recyclers coelacanth, 176–77 ecosystems, 170 Soddy, Fred er ick Reid, Harry isotopes, 133–35 fault lines, 126–27 So dium Rel a tiv ity. See The ory of rel a tiv ity electrochemical bonding, 61–62 Re pro duc tion. See Sex ual re pro duc tion So lar en ergy Ri bo nu cleic Acid (RNA) fusion, 192–93 cell structure, 166 So lar ra di a tion Ri bo somes atomic light signatures, 81–82 cell structure, 166 So lar sys tem. See also Distance to the sun; Ricci, Ostilio Gal ax ies law of falling objects, 10 existence of planets around other stars, Richer, Jean 215–16 distance to the sun, 28 planetary motion, 11–12 Ritter, Johann So nar ultraviolet (UV) light, 56 seafloor spreading, 199–200 Roent gen, Wil helm Sound X-rays, 95–96 conservation of energy, 74 In dex 253

Sound waves radioactivity, 105–6 Doppler Effect, 75–76 weak and strong force, 172 Space. See Light, space, and time Sugar Spectro graphs metabolism, 174–75 dark matter, 211–12 Sun-cen tered uni verse. See also Dis tance to distance to the sun, 27 the sun; Galax ies existence of planets around other stars, 216 importance of, 5 expanding universe, 151 origins of discovery, 5–6 quasars and pulsars, 205 Ptolemy’s model, 5–6 Spectrog ra phy Sun light atomic light signatures, 81 photosynthesis, 46 isotopes, 134 Su per con duc tiv ity quasars and pulsars, 205 importance of, 128 radioactive dating, 120 origins of discovery, 128–29 Speed of light semiconductor transistor, 184 black holes, 141 Supernovae distance to the sun, 27 accelerating universe, 218 E = mc2, 111–12 quasars and pulsars, 206 electromagnetic radiation/radio waves, 84 Sup ple ments. See Vi ta mins importance of, 155 Sym bi o sis origins of discovery, 155–56 complete evolution, 208–9 quarks, 203–4 Syn chro tron Sperm, 29 weak and strong force, 172 Spitzer, Lyman Systema Naturae, 34 fusion, 192–93 Star ling, Ernst Tansley, Arthur hormones, 109–10 ecosystems, 169–70 Stars. See Atomic light signa tures; Black holes; Taung skull Distance to the sun; Doppler Effect; human evolution, 146–47 Exis tence of planets around other stars; Tax on omy. See also Order in nature Ex pand ing uni verse; Gal ax ies; Neu tron definition of, 33 star; Quasars and pul sars; So lar system; Teisserenc de Bort, Leon Philippe Stellarator; Supernovae atmospheric layers, 107–8 Static Tele scopes. See also Mi cro scopes electricity, 38–39 atmospheric layers, 108 Stellarator dark matter, 211–12 fusion, 193 definition of, 14 Steno, Nich o las distance to the sun, 27–28 fossils, 25–26 Doppler Effect, 76 Strange ness existence of planets around other stars, quarks, 204 215–16 Strato sphere expanding universe, 150–51 atmospheric layers, 108 planetary motion, 13 Strong force. See Weak and strong force radio, 205 Sub atomic par ti cles. See also Atomic bonding; Tem per a ture. See also Ab so lute zero tem per a ture Quan tum the ory; Quarks atmospheric layers, 107–8 antimatter, 160–61 Big Bang theory, 186 electrons, 101–2 Earth’s core and mantle, 136–37 isotopes, 133 fusion, 192–93 neutrons, 163 infrared (IR) and ultraviolet (UV) light, 55 254 In dex

Tem per a ture (Cont.) Un cer tainty Prin ci ple nature of heat, 50 importance of, 153 nature of the atmosphere, 202 origins of discovery, 153–54 oceans, effects on weather, 40–41 Uni ver sal grav i ta tion. See also Law of superconductivity, 128–29 fall ing objects; Laws of mo tion The ory of evo lu tion. See also He red ity importance of, 23 chromosomes, function of, 121 origins of discovery, 23–24 importance of, 79 Uni verse. See Ac cel er at ing uni verse; Dark origins of discovery, 79–80 mat ter; Ex is tence of plan ets around The ory of rel a tiv ity other stars; Expand ing universe; black holes, 140 Quasars and pulsars E = mc2, 112 Ura nium. See also Lead importance of, 114 isotopes, 134 origins of discovery, 114–15 radioactive dating, 119 Ther mo dy nam ics radioactivity, 105–6 calories, 71 Urkraft conservation of energy, 73 electromagnetism, 65–66 Ther mom e ter infrared (IR) and ultraviolet (UV) light, atmospheric layers, 107 56 superconductivity, 129 Thomp son, Benjamin. See Rumford, Count Vac ci na tions Thomson, Charles importance of, 53 deep-sea life, 88–89 origins of discovery, 53–54 Thomson, J. J. Vac uum electrons, 101–2 air pressure, 17–18 Tho rium matter, 48 isotopes, 134 Vagus nerve radioactive dating, 119 neurotransmitters, 145 Time. See Light, space, and time Vagusstoff. See Ace tyl cho line Torricelli, Evangelista van Helmholtz, Hermann air pressure, 17–18 conservation of energy, 73–74 Trace el e ments “Vari a tion,” 208 vitamins, 117–18 Veg e ta tion zones Traits. See also Genes ecosystems, 169 chromosomes, function of, 121 Veins heredity, 86–87 circulatory system, 15–16 Trans fer re sis tors Venter, J. Craig semiconductor transistor, 184 human genome, 220–21 Trans fu sions Vesalius, Andreas blood types, 100 human anatomy, 7–8 Tran sis tor. See Semi con duc tor tran sis tor Vi ruses. See also An ti bi ot ics; Bac te ria; Cell Trans verse waves struc ture Earth’s core and mantle, 137 importance of, 97 Tro po sphere origins of discovery, 97–98 atmospheric layers, 108 “Vi tal force” the ory Tryptophan conservation of energy, 73 vitamins, 118 Vi ta mins definition of, 118 Ul tra vi o let (UV) light. See In frared (IR) and importance of, 117 ul tra vi o let (UV) light origins of discovery, 117–18 In dex 255

Vol ume Weight. See also Atomic weight; Mat ter Boyle’s Law, 20 air pressure, 17–18 buoyancy, 4 atoms, 60 gas, 19–20 Boyle’s Law, 20 oceans, effects on weather, 41 law of falling objects, 9–10 levers, 3 Wa ter Wind air pressure, 17 atmospheric layers, 107 Wat son, James Wob ble ef fect DNA, 196–7 existence of planets around other stars, human genome, 220–21 215–16 Weak and strong force Wright, Thomas definitions of, 171–72 galaxies, 36–37 importance of, 171 origins of discovery, 171–72 X-ray crystalography Weap ons ad vance ment penicillin, 159 E = mc2, 112 X-rays. See also Gamma rays isotopes, 133 dark matter, 212 nuclear fission, 178–79 DNA, 196–97 speed of light, 156 electromagnetic radiation/radio waves, 83–84 Weather. See also At mo sphere; Ba rom e ter; genes, function of, 167–68 Oceans, ef fects on weather; Tro po sphere importance of, 95 air pressure, 17–18 infrared (IR) and ultraviolet (UV) light, 55 atmospheric layers, 107–8 origins of discovery, 95–96 forecasting, 201–2 ice ages, 69–70 Yukawa, Hideki nature of the atmosphere, 202 strong force, 171–72 Wegener, Alfred continental drift, 138–39 Zonation. See Lat i tu di nal zonation

About the Author

Kend all Ha ven. The only West Point grad u ate and only se nior ocean og ra pher to be come a pro fes sional sto- ryteller, Haven has performed for four million. He has won numer ous awards for his story writing and his story - telling and has conducted story writing and story tell ing workshops for 40,000 teachers and librar i ans and 200,000 students. Haven has published five audio tapes and twenty-five books, includ ing three award-winning books on story: Write Right and Get It Write on writ ing, and Super Sim ple Sto ry tell ing, on doing, using, and teaching story tell ing. Through this work he has become a na tion ally rec og nized ex pert on the ar chi tec ture of nar ra - tives and on teaching cre ative and expos i tory writing. Ha ven served on the Na tional Sto ry tell ing As so ci a - tion’s Board of Direc tors and founded the Inter na tional Whole Lan guage Um brella’s Sto ry tell ing In ter est Group. He served as co-direc tor of the Sonoma and Bay Area Story tell ing Festi vals, was an advi sor to the Mariposa Story tell ing Fes tival, and is founder of Story tell ing Fes tivals in Las Vegas, Nevada, and Boise, Idaho. He lives with his wife in the rolling Sonoma County grape vine yards in ru ral North ern Cal i for nia.