Essays

DOI: 10.1002/anie.200803876 History of Science Lord Rutherford (1871–1937): The Newton of the Atom and the Winner of the Nobel Prize for , 1908 John Meurig Thomas* atomic · history of science · radiochemistry · Rutherford, Ernest

1. Introduction three towering achievements associated was largely his “boys”—a term which he with his name—the theory of nuclear used affectionately to describe his stu- When , later disintegration (with Frederick Soddy, dents and collaborators—who had de- known as Lord Rutherford of Nelson, 1902–1903), his model of the nuclear veloped radar and other devices of died unexpectedly in 1937, the New atom (1911), and the discovery of the strategic military significance. It was York Times stated: “…It is given to but artificial disintegration of the nucleus his assistants Chadwick and Cockcroft few men to achieve immortality, still less (1919)—the first two, while based on (later Nobel Prize winners each in their to achieve Olympian rank, during their experimental evidence, were theoretical own right) who built the UK Atomic own lifetime. Lord Rutherford achieved concepts. Even more ironic is that Energy Authority. both. In a generation that witnessed one Rutherford was awarded the Nobel of the greatest revolutions in the entire Prize in Chemistry (not Physics) in history of science he was universally 1908. When news of this award reached 2. The Trajectory of Rutherford’s acknowledged as the leading explorer of him he laughingly commented that he Life the vast infinitely complex universe with- had observed many rapid transforma- in the atom, a universe that he was first to tions among radioelements, but none as This section deals first with his place penetrate.” rapid as his transformation from a of birth, New Zealand, then his period And when Sir Mark Oliphant, a into a .[2] as a researcher at Cambridge (1895– Antipodean and student, collea- Distinctions between physics and 1898), followed by his professorships at gue, and friend of Rutherford in Cam- chemistry are often arbitrarily drawn; McGill University, Montreal (1898– bridge, who, along with Paul Harteck, and it is futile pedantically to emphasize 1907) and (1907–1919), discovered tritium, wrote a foreword to them, especially where great scientists and his position as the Cavendish Pro- a definitive work[1] on Rutherford in like Faraday and Rutherford are con- fessor of Physics at Cambridge (1919– 1999 he described him as “the greatest cerned. In this regard the comments 1937). experimental scientist since Faraday”. made by Rutherford in August 1931, Oliphant also recalled that “Max Born, when the centenary of Faradays discov- whose own contributions to theoretical ery of electromagnetic induction was 2.1. New Zealand (1871–1895) physics were formidable, told me that celebrated, are worth repeating:[3] “The Rutherford was the greatest scientist he more we study the work of Faraday, with The New Zealand of the Ruther- had ever known, including even Ein- the perspective of time, the more we are fords youth was an agrarian society that stein.” impressed by his unrivalled genius as an had been settled by Europeans for only Historians of science the world over, experimenter and a natural philosopher. a few generations. Yet they brought to not to mention active scientists them- When we consider the magnitude and the Antipodes their English and Scottish selves, generally argue that Rutherford extent of his discoveries and their influ- values of hard work, thrift, and a respect was the most accomplished experimen- ence on the progress of science and of for education, and endeavored to create tal physicist since Faraday. Yet the case industry, there is no honour too large to the institutions that would reward their can be made (see Section 2.3) that of the pay to the memory of Michael Faraday— pioneering activities. Rutherford absor- one of the greatest scientific discoverers bed these qualities, and throughout his of all time.” life he exhibited the energy and re- Rutherford, like Faraday, took out sourcefulness of his father and the thirst [*] Prof. Sir J. M. Thomas no patents even though he possessed the for knowledge of his mother, a former Department of Materials Science skills and made discoveries, especially teacher.[2] A bright student, he won a early in his career, that would have scholarship to Nelson College (situated Pembroke Street Cambridge, CB2 3QZ (UK) interested businessmen. Rutherford at the tip of the South Island). Another Fax : (+44)1223-334-567 himself did not see his discoveries as competitive scholarship allowed him in E-mail: [email protected] opening the era of atomic energy. But it 1890 to enter Canterbury College in

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Christchurch, where he expanded his horizons culturally and intellectually. After completing his BA degree in 1892 he proceeded to take his MA (in mathematics and mathematical phys- ics), and in 1894 he began his first independent research. But he had fur- ther cause to remain in Christchurch, for his heart was captivated by Mary New- ton, his landladys daughter. (He was to marry her in 1900). His research cen- tered on the magnetization of iron by high-frequency discharge, work which enabled him to devise a sensitive meth- od of detecting radio waves. He had recognized that an already magnetized needle would lose some of the strength, in an alternating magnetic field, making it a suitable detector for wireless signals and a device of potential commercial Figure 1. J. J. Thomson’s research group in the , Cambridge, 1898. Rutherford is fourth from the left in the middle row; to his right is C. T. R. Wilson, of cloud- applicability. He published two papers chamber fame, who won the in 1927. Of him, P. M. S. Blackett, another on this topic in the Transactions of the Cavendish physicist to win the Nobel Prize (1948), said: “Of the great scientists of his age, he was [4] New Zealand Institute. perhaps the most gentle and serene, and the most indifferent to prestige and honours.” The Rutherford applied for an 1851 Ex- polymathic (1872–1946) was also a member of the Cavendish Research group at hibition Scholarship in 1894; the rules that time (bottom row, third from the left, next to J. J. Thomson). had just been changed to allow candi- dates from the British Commonwealth to apply for such prestigious awards. In addition, Cambridge University had al- tion of different gases, and other rele- 2.3. Montreal (1898–1907) so just changed its statutes and now vant characteristics. permitted graduates from other univer- In 1896 radioactivity was discovered By the time Rutherford found his sities to pursue research there. Enrolling by Becquerel, and soon both Marie feet in McGill University, the omens in 1895, Rutherford was the first re- Curie, in Paris, and Rutherford, in Cam- were particularly good. First, the labo- search student under the new regula- bridge, pursued quantitative studies of ratories of the Department of Physics tions. He joined the Cavendish Labora- the phenomenon. The attention of the there were exceptionally well equipped: tory, whose Director was J. J. Thomson worlds scientific community, especially they were arguably the best in North (Figure 1).[5] after Pierre and Marie Curie (and Gus- America at the time. This was because tave Bmont) discovered polonium, was of the munificence of Sir William Mac- now riveted to radioactivity. For the Donald, a rich benefactor who had said 2.2. Cambridge (1895–1898) next four decades Rutherford and his that he wanted McGill to have the colleagues focused on radioactivity resources in physics comparable to Two months after Rutherfords ar- through its connections with atomic those of the Cavendish Laboratory in rival in Cambridge, X-rays were discov- physics, nuclear physics, and nuclear Cambridge. Not only was there the most ered (in November 1895) by Wilhelm chemistry. advanced equipment, even the stores Conrad Rntgen. And since this new In his work on uranium, using ab- had chemicals that hardly a department radiation exerted a marked effect upon sorption experiments (with rays imping- of physics or chemistry anywhere in the the discharge of electricity in gases (a ing on foils of various thicknesses) he world could rival, there being a good topic of great interest to Thomson),[6] observed that one type of radiation was supply of the then very costly radium Rutherford was quick to seize the op- readily stopped, another penetrated fur- bromide, for example. Second, the 21- portunity of collaborating with “J.J”. ther. He named the two types of radia- year-old Frederick Soddy, a former The collaboration yielded a classic pa- tion alpha and beta, because, he ex- student of Aberystwyth in and per in 1896 on the theory of ionization.[7] claimed, he was a simple man and liked Merton College, Oxford, and a brilliant X-rays generate the positive and nega- simple experiments and explanations! experimentalist, had just been appoint- tive ions, which are attracted to electro- A physics professorship at McGill ed lecturer in chemistry at McGill. des, so that he could readily measure University in Montreal fell vacant in Rutherford and Soddy entered into a currents. Work of this kind continued for 1898. Thomsons advice was sought, and most rewarding eighteen-month collab- much of 1896 and 1897, with Rutherford he gave a glowing reference for Ruth- oration from October 1901 to April examining the ions velocities, their erford.[8] 1903, during which time they produced rates of recombination, the electrifica- nine major papers laying the founda-

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tions for the serious study of radio- the earth, a topic to which we return in activity.[9] Sections 3 and 4. The of radioactivity in 1901 It was at McGill University that was profoundly enigmatic. Its discover- Rutherford coined the word “emana- er, Becquerel, interpreted it as a form of tion”. His colleague in the Department long-lived phosphorescence. And the of Electrical Engineering, R. B. Owens, Curies favored the idea that an un- obtained erratic ionization measure- known ethereal radiation pervaded ments until Rutherford traced the cause space, causing a resonance in the heav- to air currents in the room, and recog- iest elements which resulted in the nized that something from thorium was emission of alpha, beta, and gamma rays being blown about. Uncertain if it was a as secondary radiations. Rutherford and gas or a cloud of particles, he called it Soddy felt that radioactivity was an thorium emanation (in 1900), and Euro- atomic phenomenon. Their famous pean soon discovered emana- theory, sometimes called disintegration, tion from radium and actinium. When and sometimes transformation or trans- Sir William MacDonald donated a liq- Figure 2. Sir (1851–1934), mutation, claimed that the atomic pro- uid-air machine to McGill, Rutherford who resigned prematurely from the chair of physics in Manchester on condition that Ruth- cess involved spontaneous chemical and Soddy showed, by condensation erford be invited to take his place. For further changes that produced new substan- experiments, that emanation was a gas. details see Ref. [10]. ces.[9i] Thus, thorium decayed into thor- Great excitement later ensued when this ium X, while thorium emanation (see gas was recognized to belong to that below) decayed sequentially into thor- family of inert gases found by Sir partment (after the Cavendish) in the ium A, B, C, and so forth. Each, they William Ramsay.[6] (Soddy in 1903 UK. He was independently wealthy and asserted, was a different chemical ele- joined Ramsay in the UK where, by an engaging personality;[10] and he left ment. Such views were quite revolu- spectroscopic examination of the ema- his personal assistant, ,[11] to tionary. Was it not the case that atoms nation, they determined it to be ). the laboratory and also endowed it with were indestructible and immutable? Rutherfords magnetic personality a readership in mathematical physics The theory of Rutherford and Soddy, and superb experimental skills, aided (filled later by ). Four men based on experimental work of rabbin- by the chemical virtuosity of Soddy, from alone, and many other ical complexity, had more than a whiff of attracted worldwide attention. Otto overseas workers, came to study with alchemy associated with it; and had not Hahn, who had discovered the radio- Rutherford during his first year in Man- the ghost of alchemy had long been active element thorium, and who, deca- chester.[2] exorcized by 1901? But the graphs of des later, received the Nobel Prize for The Austrian Academy of Sciences, radioactive decay of a parent element the discovery of nuclear fission, joined in an act of magnanimity, sent Ruther- and the rise of a daughter one were Rutherford in 1905–1906. And the re- ford a generous amount of radium irrefutable. The quantitative work of the doubtable Bertram Boltwood, soon to chloride (extracted from the Joachims- 30- and 24-year-olds was of inexpugna- teach at Yale University, collaborated thal uranium mines under its control). ble validity. However, some powerful with Rutherford by mail; they proved This enabled him, with Geiger in partic- voices, notably that of Lord Kelvin, circumstantially that uranium and radi- ular, to focus on the study of alpha were raised against them. He said: “I um were related, thereby linking the two particles. These were, in relative terms, venture to suggest that ethereal waves radioactive families. At McGill also, massive particles and unlike beta par- may supply energy to the radium”. Rutherford was hospitable to women ticles, of atomic dimensions; Rutherford Where did the law of conservation of in his laboratory, Harriet Brooks being a thought they might hold the key to a energy fit into all this? By saying that all notable representative in a period when deeper understanding of the nature of radioactive elements, including urani- gender prejudice remained strong. In matter. With Geiger he built in 1908 a um, ultimately would change into an this respect, Rutherford and Rayleigh long brass tube having an insulated wire inactive end product, Rutherford and exhibited the same degrees of kindness, along the axis connected to an electro- Soddy satisfied this cardinal law of generosity of spirit, and practical com- meter. A particle passing through the nineteenth-century physics. There was mon sense.[6] gas caused ionization, and initiated a energy inside the atom. brief discharge in the gas, and the Another important consequence of resulting pulse of current could be the Rutherford–Soddy collaboration 2.4. Manchester (1907–1919) detected on a meter. (In 1928 Geiger centered on the heating effects of radi- improved this prototype and made it um (and other radioactive elements). In 1907 when Sir Arthur Schuster[10] more sensitive with his co-worker W. The amount of radium present in igne- retired early from the chair at the Mller.) The key result of Rutherford ous and sedimentary rocks is sufficient he stipulated and Geigers work was that alpha par- to diminish the rate of cooling of the that Rutherford should succeed him ticles are doubly charged helium atoms. earth. By noting this fact, Rutherford (Figure 2). Schuster had made his de- These experiments of 1908 con- went on to clarify the estimated age of partment the second best physics de- firmed that each alpha particle caused

9394 www.angewandte.org 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 9392 – 9401 Angewandte Chemie a flash of light to occur when it struck a Line spectra were due to quantized fluorescent screen, such as one com- energy emission or absorption. This posed of zinc sulfide or the mineral was the dawn of a new era, one that willemite. Thus scintillation counting, gained spectacular support shortly already known as a means of recording thereafter from H. G. J. Mosleys work radioactive events, was validated as (alongside Rutherford) on X-ray spec- reliable. It became much more conven- tra, when he made a compelling case for ient than the primitive device that the central importance of the concept of evolved into the famous Geiger counter the atomic number. and more readily usable even than the emptied Rutherfords Geiger–Mller counter. In an ingenious laboratories. He himself devoted much experiment Rutherford arrived at the of his time to the so-called Admiralty value of the basic unit of charge e (even Board of Invention and research on before Millikans famous oil-drop meth- antisubmarine warfare as well as work od). He measured the charge from a on underwater acoustics. In 1919, how- radium sample and divided it by the ever, Rutherford was to publish the number of alpha particles emitted to results of yet another epoch-making obtain the charge of each particle. experiment, again made with alpha Technically skilled in the particles. He showed that when the new field of radioactivity were attracted particles collided with atoms of nitro- to Rutherfords Manchester laboratory. gen, protons and were produced One was Boltwood from Yale who [Eq. (1)]. visited in 1909–1910, another was Kasi- 2 7 1 8 mir Fajans, the Polish-American phys- 4He þ 14N ! 1H þ 17O ð1Þ ical chemist, and the Hungarian, Ger- man-educated Georg von Hevesy,[12] The swift protons produced in this first ever example of “artificial disinte- inventor (with F. A. Paneth) of the Figure 3. a) The scattering of alpha particles technique of isotopic labeling and radio- by the atomic nucleus (from Ref. [1]). b) The gration” (of the normally stable nitro- activation analysis, all of whom contrib- postage stamps (lower left) issued in 1971 by gen nucleus) was so revolutionary and uted to an understanding of the group the Soviet Union coincided with the sixtieth so pregnant with far-reaching implica- displacement laws and the concept of anniversary of Rutherford’s enunciation of the tions, that it clearly needed to be sup- isotopy. (The word isotope was coined nuclear atom. Rutherford’s image also ap- ported by very complete experimental pears in Canadian and New Zealand stamps later by Soddy, who like Heuesy, also evidence, which Rutherford and his shown here. won a Nobel Prize). colleagues duly provided. This work An exercise in Rutherfords catego- was done after he moved to take up ry of “any damn fool experiment” was the Cavendish chair in Cambridge, when that which he assigned to the under- occur the electrostatic attraction or he succeeded his former mentor J. J. graduate Ernest Marsden in 1909. He repulsion must be concentrated in a Thomson. was asked to look for large-angle scat- volume that was minute compared with tering of alpha particles by a thin film of the volume of the entire atom. So, in a gold. To everyones astonishment, Mars- sense, the atom was akin to our solar 2.5. Cambridge (1919–1937) den observed occasional scatterings at system. angles greater than 908 whereupon Gei- It seems that, outside Manchester, Rutherford left Manchester with ger excitedly joined him to complete the this discovery was received without many regrets, for it was the place of investigation. Rutherfords reaction, excitement.[2] But everything changed great achievements and the home of doubtless somewhat exaggerated in its in 1913 when Niels Bohr published his many friends. Of this change Niels Bohr repetitious telling, is famous:[13] “It was famous theory. He had visited Man- later wrote:[14] “I remember on a visit to almost as incredible as if you fired a 15- chester in 1912 and returned as a staff Manchester of hearing Rutherford speak inch shell at a piece of tissue paper and it member (1914–1916). At home in Den- with great pleasure and elation about the came back and hit you.” mark he knitted together radioactivity, prospect of his going to Cambridge, but It took Rutherford well over a year atomic physics, , quantum expressing at the same time a fear that the of considerable cogitation before he theory, and chemistry. Radioactivity or- many duties connected with this central could say that he knew what the atom iginated in the nucleus, while ordinary position in the world of British physics looked like. In 1911 he revealed a new chemical and physical properties were would not leave him those opportunities model, the nuclear atom, which is argu- dependent upon the in orbit. for scientific research which he had ably his greatest achievement. The alpha The orbits, he claimed, were stable, (in understood so well how to utilize in particles were deflected from their paths blatant contradiction to classical elec- Manchester. Everybody knows that this by encounters with single atoms of the trodynamics) and the angular momen- fear was unfounded. The powers of target (Figures 3 and 4). For this to tum of electrons in them was quantized. Rutherford have never manifested them-

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Figure 4. Rutherford’s first rough note on the nuclear theory of atomic structure, written, probably, in the winter of 1910–1911.

selves more strikingly than in his leader- awarded the Nobel Prize for physics in niques for counting alpha particles and ship of the Cavendish Laboratory the 1935.) protons were revolutionised by Wynn- glorious tradition of which he has upheld During the early 1920s Rutherford Williams. … He and Ward developed the in every way.” and Chadwick succeeded in disintegrat- Cavendish linear amplifier which could In 1920, Rutherford suggested the ing several of the lighter elements, but it respond quantitatively to the very small existence of a neutral particle (in his was not known at that time whether the current-pulse produced in a shallow second Bakerian Lecture to the Royal alpha particles escaped the explosion ionization chamber by the passage of a Society) with the properties of a neu- unscathed or combined with the target single fast particle…The amplitude of the tron, to explain the building up of nuclei nucleus before the latter transformed. pulse was proportional to the ionizing of heavy elements. Chadwick, who had P. M. S. Blackett in 1925 used the cloud- power of the particle, so that protons moved from Manchester with Ruther- chamber apparatus developed by could be readily distinguished form al- ford, made several attempts to detect C. T. R. Wilson to photograph the tracks pha-particles… All this revolutionized such particles but initially had no luck. of some 400000 a encounters. Most the rate at which statistically significant Later in 1932 when he bombarded were ordinary elastic collisions but eight results in nuclear physics were obtained.” beryllium with alpha particles, very involved disintegration. Leaving the Rutherford and Chadwick failed to penetrating radiation was produced. point of disintegration were two tracks, disrupt any elements heavier than argon That year Irne and Frdric Joliot- disintegration fragments, proving that and realized that alpha particles from Curie found that this radiation could the alpha particle had been absorbed naturally decaying radioelements, with eject protons with high velocities from into a compound nucleus. their two positive charges, were repelled matter containing . Chadwick During this era in the Cavendish by the large positive charges on the showed that this radiation could be Laboratory, the Welshman Wynn-Wil- nuclei of elements with large atomic explained if the particles had nearly liams, a new recruit of Rutherfords, numbers. Thanks to a visit to the Cav- the same mass as protons but no charge. made great advances in instrumentation endish Laboratory by George Gamow, (It was for this work that Chadwick was (Figure 5). As Oliphant put it:[15] “Tech- who explained that wave mechanics

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his last book “The Newer Alchemy” published in 1937. Insofar as it was possible to do so within the accommodation and resour- ces of the laboratory, Rutherford sought to encourage other important lines of work. Among these was the work of Kapitsa, the colorful Russian physicist (winner of the Nobel Prize for Physics in 1979 for his discovery of superfluidity, and formidable opponent of Stalin) to search for methods of producing high magnetic fields to send the alpha par- ticles in their paths, and Appleton (Nobel Prize winner in 1947) and Rat- cliffe in radio research (and a forerunner of the later work on radio astronomy at the Cavendish). He also backed Kapit- sas project to build a plant for the production of and his work in achieving, for short durations, magnetic fields of over 300 kilogauss. Figure 5. Rutherford’s Cavendish Laboratory photograph, 1926. Seated in the front row are This was done in the early 1930s and was seven Nobel laureates along with the redoubtable G. I. Taylor. C. E. Wynn-Williams is the first made possible by funds from the Mond from the left in the top row. Bequest for magnetic and low-temper- ature work (see Figure 6). Rutherford, predicted the possibility that a projectile This was the first experimental proof like his predecessors Maxwell, Rayleigh, of relatively low energy could tunnel of Einsteins long-famous relationships and Thomson, also undertook work as a through the potential barrier of the E = mc2, a fact which convinced Ruth- Visiting Professor of Experimental nucleus instead of going over it, Ruth- erford (hitherto sceptical of the power Physics in the of Great erfords team ceased to raise the voltage of theoreticians) that quantum and wave Britain in . He lectured fre- beyond a certain high and attainable mechanics were valuable, even if he value. And so accelerated electrons, himself understood them only imper- protons, and alpha particles began to fectly. It also induced him to invest in be used by the Cambridge physicists. A the future in the form of a cyclotron, new breed of research student arose in which was developed by E. O. Lawrence the persons of T. E. Allibone, P. Kapitsa, in Berkeley, California. J. D. Cockcroft, and E. T. S. Walton, Although Rutherford himself was with engineering expertise, and they not directly involved in the Nobel- constructed accelerators capable of Prize-winning work of Chadwick, Cock- hurling protons and electrons with en- croft, and Walton (and later Blackett for ergies of several hundred thousand his beautiful work on cosmic ray show- volts. The Cockcroft–Walton machine[16] ers) he lent tremendous enthusiasm, succeeded in disintegrating lithium academic authority, and moral support atoms by so-called “swift protons”. The to all his neophytes and established lithium disintegrated according to Equa- collaborators. He continued his exper- tion (2). The energy released was de- imental endeavors, however, and, with Oliphant (thanks to a gift of heavy water

1 7 4 made by G. N. Lewis) he formed, on 1H þ 3Li ! 2 2He ð2Þ Figure 6. A striking feature of the old Cavend- bombarding deuterium with deutrons, ish site is the carving of a crocodile on the evidence for the existence of a hydrogen outer wall of the Mond Laboratory. This labo- scribed by Cockcroft and Walton (who isotope of mass 3 and a helium isotope ratory was built in 1933 by the Royal Society shared the Nobel Prize in physics in of mass 3. In all this he felt deeply for Kapitza to continue his work on intense 1951) thus:[16] “The evolution of energy satisfied intellectually: the transmuta- magnetic fields (see text). “The crocodile” on this view is about sixteen million tion of the elements so long and so often was Kapitza’s pet name for Rutherford, either because of his fear of having his head bitten volts per disintegration, agreeing sought and at last achieved was in one off by him, or because his voice could be approximately with that to be expected sense the crowning triumph of his lifes relied to precede his visits, just like the from the decrease of atom mass involved work. He conveyed something of this crocodile’s alarm clock in “Peter Pan” (from in each disintegration.” satisfaction and boundless enthusiasm in the Cavendish Laboratory web site, 2008).

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quently (with copious demonstrations) day temperatures and the temperature The amount of helium in the mineral will from behind the kidney-shaped bench gradient at the surface of the earth as steadily increase with time, and the total that was the spot from where Davy and well as the average conductivity and amount present should be proportional Faraday had made science and its ap- specific heat of the materials of the to the age of the mineral and the amount preciation so fascinating among the earth, it is possible with the aid of of radium contained in it. I have some literati and general public in London Fouriers theorem to deduce the interval crystals of a new mineral, thorianite, (see Figure 7). that has elapsed since the earth was a found a few years ago in Ceylon, which Rutherford published some 180 re- molten mass. But biologists and palae- contains about 12 percent of uranium search papers and five books—the first ontologists were unhappy with Kelvins and about 70 percent of thorium. This being his Silliman Lectures (1905) in estimates. They knew in their bones that mineral on heating evolves a remarkably Yale University entitled “Radioactivi- Kelvin was wrong: fossil and mineralog- large quantity of helium—more than ty”. He was awarded over two dozen ical evidence pointed to an older age. In 10 cc per gram of the mineral. Now it is honorary degrees and was elected to his celebrated The Origin of Species, almost certain that the helium stored up membership of most of the national Charles Darwin wrote: “In all probabil- in this mineral has been produced by the academies of science in the world. King ity a far longer period than 300 million breaking up of the radium, contained in conferred upon him the Or- years has elapsed since the latter part of it since the formation of the mineral. der of Merit in 1925 and he served as the secondary period.” This statement is Assuming the rate of production of president of the Royal Society from in flagrant contradiction to Kelvins helium by radium already mentioned, it 1925 to 1930. He was raised to the estimates. can be calculated with some confidence peerage in 1931 as Baron Rutherford of Since Rutherford and Soddy knew that the mineral thorianite is at least 500 Nelson (a small town in New Zealand). (and had measured) the rate at which million years old, that is, this interval of He served as president of the Academic radioactive isotopes decay, and since time must have elapsed since the forma- Assistance Council from 1933 (which they could readily measure the amount tion of the mineral in the earths crust. involved him in a political issue, since of residual parent radioactive (or accu- This is a minimum estimate, for probably the body was created to help scientists mulated daughter) isotopes, the age of some of the helium has in the course of who fled Nazism[17]). the earth could be determined directly. ages escaped from the mineral… When He died in a nursing hospital in In effect, Rutherford and Soddy had the constants involved in these calcula- Cambridge on October 19, 1937, of uncovered a steadily ticking clock. One tions are accurately determined, I feel complications following an operation determines the age of the earth simply great confidence that this method will for a strangulated hernia. His ashes by measuring either the residual radio- prove of utmost value in determining were placed alongside those of Newton, activity or the amount of accumulated with accuracy the age of the radioactive Kelvin, Darwin, and Sir John Herschel helium in the (radioactive) mineral. But minerals and indirectly of the geologic in Westminster Abbey. Rutherford had also identified an un- strata in which they are formed.” justified (or erroneous) assumption It is noteworthy that all other radio- made by Kelvin in his estimates: namely active clocks used by earth scientists— 3. Rutherford and the Controversy that there was an extra source of heat in potassium/argon, uranium/lead—origi- Concerning the Age of the Earth the earth which delayed the cooling by nate from Rutherfords seminal work. radiation alone. This source is radium. Lord Kelvin (formerly William In a brilliantly argued article entitled Thomson) was an exceptionally gifted Some Cosmical Aspects of Radioactivi- 4. An Incident at the Royal mathematician, physicist, and business- ty,[18] the write-up of a lecture he gave to Institution man. So authoritative were his pro- the Royal Astronomical Society of Can- nouncements, and so frequently was ada in 1907, he showed that there is a Rutherfords work did not, at first, their validity established, that lesser very large quantity of radium and other please Kelvin. There is an amusing story, scientists tended to accept all his calcu- radioactive matter distributed over the told by Rutherford in a letter to his wife, lations and estimates as sacrosanct. surface of the earth, so that this matter is concerning his visit to the Royal Insti- Kelvin had estimated the age of the continuously supplying heat to the tution in 1904.[19] That year, when the 33- earth to be about a hundred million earth. Rutherford showed that: “A year-old Rutherford came to Britain years, though he did publish even lower quantity of radium supplies enough heat from Montreal to deliver the Bakerian estimates. In the last few decades of the to melt more than its weight of ice per Lecture of the Royal Society, the Royal 1800s he was on record as having said: hour. A pound of radium in the course of Institution took the opportunity of in- “Consolidation of the earth took place a year will emit as much heat as that viting him there also. As Rutherford more than 20 million and less than 40 resulting from the combustion of 100 entered its famous theater he spotted million years ago.” pounds of good coal.” the 80-year-old Kelvin in the audience He arrived at such figures by assum- In a startling denouement to his (see Figure 7). This is what Rutherford ing that when the earth was first formed lecture Rutherford says: “Consider, for felt: “I came into the room, which was all the rocks were molten and that they example, a very dense radioactive min- half dark, and presently spotted Lord cooled according to the ineluctable laws eral from which the helium continuously Kelvin in the audience and realised that I of radiation physics. Knowing present- generated by the radium cannot escape. was in for trouble at the last part of my

9398 www.angewandte.org 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2008, 47, 9392 – 9401 Angewandte Chemie speech dealing with the age of the earth, In fact, Rayleigh said that he would where my views conflicted with his. To arrange an English Edwardian weekend my relief Kelvin fell fast asleep but as I party at his (baronial) home (Terling came to the important part, I saw the old Place) and bring together Kelvin and bird sit up, open an eye and cock a Rutherford. This event did indeed take baleful glance at me. Then a sudden place, as the visitors book (now in the inspiration came and I said Lord Kelvin possession of the present Lord and Lady has limited the age of the earth, provided Rayleigh) testifies (Figure 8), from no new source was discovered. That which we see that the Schusters also prophetic utterance referred to what we attended. are now considering tonight, radium! A little after this event, Rutherford Behold! The old boy beamed upon me.” reported to his wife:[19] “Lord Kelvin has The kind of audience that would talked radium most of the day and I have confronted Rutherford when he admire his confidence in talking about a entered the theater at the Royal Insti- subject of which he has taken the trouble tution would have been similar to that to learn so little… He wont listen to my Figure 8. At Terling Place, Lord Rayleigh’s which typically attended Sir James Dew- views on radium, but Strutt (i.e. Lord home in the heart of Essex where he conduct- ars and others Friday Evening Dis- Rayleigh) gives him a year to change his ed many of his experiments, there were fre- courses (Figure 7). Lord Kelvin and mind. In fact they placed a bet to that quent Edwardian weekend parties. It was at Lord Rayleigh, along with other celeb- effect.” one of these in May 1904 that Rayleigh rities (including the Prime Minister of The argument was basically whether brought the young Rutherford and Lord Kelvin together. Reprinted with kind permission of the day, A. J. Balfour, who was Lord the energy emitted by radium was Lord and Lady Rayleigh. Rayleighs brother-in-law), were fre- derived solely from within the atoms quent attendees at such events. internal structure or whether the energy The story is told that, after Ruth- was somehow collected and redistribut- erfords lecture in which he raised the ed by the radioactive atoms from some 5. Some Tributes to Rutherford issue of the age of the earth, Lord “ethereal” source. To Kelvins great Rayleigh mentioned to Lord Kelvin that credit, he publicly abandoned his theory It was said that Rutherford, a unique it would not be long before he (Kelvin) at the British Association meeting later blend of simplicity with greatness, never would accept Rutherfords estimate as that year (1904); and, moreover, he paid made an enemy and never lost a friend. being more nearly correct than his own. up his five-shilling bet! He had a quick sympathy with the oppressed, and he was a friend to the outcast. He lived to be a center of universal affection as well as esteem.[14] He had volcanic energy, intense enthu- siasm, and an immense capacity for work. Rutherford had no cleverness— just greatness. In addition, he had the three precious gifts of the poet—deep insight, powerful imagination, and a profound love of truth.[14] Three specific comments will suffice to illumine this immortal scientist: the words of his collaborator Frederick Soddy, those of Samuel Devons, a stu- dent in the halcyon days of Rutherfords “Cavendish”, and those of Sir James Jeans his friend and admirer. Soddys scientific spark went out after he had discovered the existence of (and invented the word) isotopes[20] in 1913, whereas Rutherfords star was Figure 7. This scene depicts Sir demonstrating the properties of always in the ascendant. Soddy gener- ca. 1904 at the Royal Institution, London. The audience shown here (front row from right to left) ously remembered their revolutionary includes Sir Oliver Lodge, Ludwig Mond, George Matthey, Lord Rayleigh, Sir James Crichton- work in Montral: “My relations with Brown, Sir , the Prime Minister (A. J. Balfour), Sir George Gabriel Stokes, and the then youthful Ernest Rutherford were Lord Lister; Lord Kelvin is also shown, sixth from the center of the bottom left. When Rutherford gave his famous talk on “Radioactivity” in 1904 (see text), his audience would have been similar uniformly cordial and inspiring, and I to this one. Where Dewar stands (holding the thermos flask named in his honor) is where Davy came fully under the influence of his and Faraday also stood in lecture–demonstrations that they gave in the nineteenth century. magnetic energetic and forceful person-

Angew. Chem. Int. Ed. 2008, 47, 9392 – 9401 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.angewandte.org 9399 Essays

ality, which at a later date was to cast a since it could fall to only one man to department was closed from about spell over the whole scientific world. My discover the laws which govern the uni- 6 pm onwards. “Do not stay here in the recollection of him was of an indefatiga- verse. Had he lived in a later age, he laboratory until late, thinking that you ble investigator, guided by an unerring might have said something similar of are working hard. Go home and clear instinct for the relevant and important, Rutherford and the realm of the infinitely your mind and be ready for fresh action and as an unequalled experimentalist small; for Rutherford was the Newton of the following day.” This is what he often seeing amidst all the difficulties, the atomic physics. In some respects he was said. simplest lines of attack… By the time more fortunate than Newton; there was In addition to his numerous admir- our cooperation ended, radioactivity, nothing in Rutherfords life to compare able attributes, Rutherford could pick, which had already become a consider- with the years which Newton spent in a attract, and encourage winners. One has able jigsaw puzzle, had been put together, vain research for the philosophers stone, only to look at the department photo- and my chief impression of those days or with Newtons output of misleading graphs in the Cavendish Laboratory remains of an intense mental exaltation optical theories, or with his bitter quarrels (from 1919 onwards) to realize the truth as the pieces came together and they were with his contemporaries. Rutherford was of that statement. But he did make the fitted by the single theory of atomic ever the happy warrior—happy in his occasional mistake. J. Robert Oppen- disintegration into a convincing whole.” work, happy in his outcome, and happy heimer, U.S. theoretical physicist, for Samuel Devons, formerly (like in its human contacts.” example, although he was a student at Rutherford) of Harvard, he was turned down as a PhD Physics, University of Manchester and student by Rutherford. He was, how- Fellow of Trinity College, Cambridge 6. Epilogue ever, taken on by J. J. Thomson, with was, until his death in 2006, Emeritus whom he did experimental work of little Professor of Physics at Columbia Uni- When I joined the University of significance, before he went off to Gt- versity, New York. He was an under- Cambridge in 1978 and became a mem- tingen where he collaborated most ef- graduate at Cambridge in the mid-1930s, ber of the Royal Society Dining Club in fectively with Max Born. and of that period he recalled:[21] “Edu- 1980, I gradually came into close contact It is interesting to reflect that the cation it seemed, then, to be more a with scientists who had either worked scientists who are described as “the matter of inspiration by example than with Rutherford, or who had observed father of the (U.S.) atom bomb” (Op- instruction by precept. To a student of him in action and had been indirectly penheimer) and “The father of the science, and particularly physics, it was influenced by his personality, principles, (Soviet) atom bomb” (Khariton) were Ernest Rutherford who symbolised and and attitudes. Those who worked with both research students in Rutherfords exemplified this living greatness, and in him, like T. E. Allibone, or with his Cavendish Laboratory, though their ten- the recollection of my undergraduate associates (like D. Shoenberg, who was ures did not overlap.[23] It seems from days it is impossible to separate Ruth- Kapitsas PhD student) never ceased to recently available records of Soviet erford, Cambridge, and the Cavendish express their admiration of him as a science[24] that the annus mirabilis of Laboratory. …Rutherford was not only charismatic leader and inspiring role 1932, when Chadwick discovered the one of Cambridges illustrious Profes- model. Others, like Max Perutz,[22] who neutron and Cockcroft and Walton split sors he was the Professor. … The worked with J. D. Bernal in the Cavend- the atom at the Cavendish Laboratory— Cavendish was Rutherfords domain; ish starting in 1936, talked of the time, and when Lawrence built his cyclotron, his sphere of influence… Benevolent shortly after Rutherfords untimely Anderson identified the positron, and guidance, leadership and intellectual au- death, when his reprints were made Urey discovered deuterium all in the thority flowed from him, and loyalty was available to anyone who wanted to have U.S.—prompted great excitement in returned. One would no more question them at the Cavendish Laboratory. Pe- Leningrad and Moscow. The eminent his influence on those around him than rutz said that, on reading them, he was Soviet physicist, A. I. Ioffe, as a conse- one would that of the sun on the satellite immediately struck by the key principles quence, organized an All-Union confer- planets. Rutherford, the Cavendish Pro- that animated Rutherfords research: ence on the atomic nucleus. A meeting fessor, was the centre of light and warmth 1) a clear vision of what it was, in a took place shortly thereafter attended and life. It was the natural order if things. given investigation, that he was trying to also by eminent foreign speakers includ- Young undergraduate student were way prove; 2) the supreme ability to carry ing Joliot, Dirac, Rasetti, and Weisskopf. out on the periphery of this constellation out the right economical experiment but we could bask in the sunlight just the that yielded that proof; 3) a thorough- I am grateful for stimulating discussions same.” ness of purpose in his research papers with Professors E. A. Davis and A. “In truth,” said Sir James Jeans, which settled all the ambiguous issues. Howie. “most of his investigations were key ones, For Rutherford, the introduction to a each brilliant in its simplicity of concep- paper was the most important part of it. Received: August 6, 2008 tion and far-reaching in its consequen- What is it that you are trying to do, ces.” Then he proceeds, shortly after learn, or convey? Rutherfords death, to say: “Voltaire Perutz and others recalled that [1] J. Campbell, Rutherford: Scientist Su- once said Newton was more fortunate Rutherford discouraged people from preme, AAS Publishers, Christchurch, than any other scientist could ever be, working late in the laboratory. The 1999.

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[2] L. Badash in Oxford Dictionary of Na- administrative matters at the Royal 1919 when he became the Dr. Lees tional Biography, Oxford University Society, succeeding Larmor in 1912 as Professor of Chemistry at the University Press, 2004, 48, 381. its Secretary. of Oxford. Even as early as 1913 he had [3] The Times, London, 31 August, 1931. [11] Hans Wilhelm Geiger was born in said:[19] “It would not be surprising if the [4] a) E. Rutherford, Trans. N. Z. Inst. 1894, Neustadt, Germany, and studied physics elements… were mixtures of several 27, 481; b) E. Rutherford, Trans. N. Z. at the universities of Munich and Erlan- homogenous elements of similar but not Inst. 1894, 28, 182. gen before moving to Manchester. In completely identical atomic weights.” He [5] J. M. Thomas, Angew. Chem. 2006, 118, 1912 he returned to Germany, from then was the first to call such chemically 6951; Angew. Chem. Int. Ed. 2006, 45, until his death holding a series of identical elements with slightly differing 6797. important positions, including that of atomic weights, isotopes. He showed for [6] J. M. Thomas, Angew. Chem. 2004, 116, director of the German Physical Labo- example that radium D and thorium C 6578; Angew. Chem. Int. Ed. 2004, 43, ratory, the Physikalisch Technische were isotopes of lead. Notwithstanding 6418. Reichanstalt in Berlin (1912) and Pro- the award of the 1921 Nobel Prize for [7] J. J. Thomson, E. Rutherford, Philos. fessor of Physics at Kiel (1925). Chemistry for his work on the origins Mag. 1896, 392. [12] Hevesy studied water exchange between and nature of isotopes, Soddy became [8] Thomson later described Rutherford as goldfish and their surroundings and disillusioned with science and his role the best student in research he had ever within the human body; this was the within it. He took to writing exclusively had.[2] first application of stable isotopes in in the fields of economics and sociology. [9] a) E. Rutherford, F. Soddy, Trans. Chem. biology (1934). In contrast to Rutherford, whose re- Soc. 1902, 81, 321; b) E. Rutherford, F. [13] “Forty Years of Physics”: E. Rutherford marks in New York in 1933 where he Soddy, Trans. Chem. Soc. 1902, 81, 837; in Background to Modern Science (Eds.: claimed that anyone who thinks that c) E. Rutherford, F. Soddy, Philos. Mag. J. Needham, W. Pagel), MacMillan, New energy may be extracted from the atom- 1902, 370; d) E. Rutherford, F. Soddy, York, 1938, p. 68. ic nucleus is “talking moonshine”,[19] Philos. Mag. 1902, 569; e) E. Ruther- [14] “Lord Rutherford. 1871–1937”: A. S. Soddy was an ardent believer in nuclear ford, F. Soddy, Proc. Chem. Soc. 1902, Eve, J. Chadwick, Obituary Notices of energy and nuclear power. As early as 219; f) E. Rutherford, F. Soddy, Philos. of the Royal Society, 1938, 2, 1912 he commented[19] that “the still Mag. 1903, 441; g) E. Rutherford, F. 394 – 423. unrecognised energy problem awaits Soddy, Philos. Mag. 1903, 445; h) E. [15] M. Oliphant, Rutherford Recollections the future”. He saw as mans only hope, Rutherford, F. Soddy, Philos. Mag. 1903, of the Cambridge Days, Cambridge atomic energy which “could provide 561; i) E. Rutherford, F. Soddy, Philos. University Press, 1972. anyone who wanted it with a private Mag. 1903, 576. [16] J. D. Cockcroft, E. T. S. Wilson, Nature sun of his own.” [10] Schuster was descended from an old 1932, 129, 242. [21] See the University of Cambridge web Jewish business family and received his [17] He created a post in the Cavendish site (for Physics, the Cavendish, Croc- schooling in and Geneva. He Laboratory for Max Born, who had to odile), 2008. attended college in Manchester then flee from Gttingen, owing to the anti- [22] J. M. Thomas, “M. F. Perutz (1914– went to Heidelberg to study for his semitism of the Nazi regime. 2002); In Memoriam”, Protein Sci. doctorate under Kirchhoff. During [18] E. Rutherford, J. R. Astron. Soc. Can. 2003, 12,1. 1876–1881 he worked with James Clerk 1907, 145. [23] I am grateful to Professor Archie Howie Maxwell at the Cavendish Laboratory, [19] D. Wilson, Rutherford: Simple Genius, for drawing my attention to this fact. Cambridge, and collaborated with Lord MIT Press, Cambridge, 1983. [24] D. Holloway, Stalin and the Bomb, Yale Rayleigh in determining the absolute [20] After working with Rutherford in Mon- University Press, New Haven, 1994, value of the ohm. He moved on to treal and William Ramsay in London, p. 34; The Collected Papers of Lord Manchester University where, inter alia, Soddy took up an appointment at Glas- Rutherford of Nelson (Ed.: J. Chad- he investigated the spectra of gases at gow University. He later moved to the wick), Allen & Unwin, London, 1962– low pressures. After resigning from his chair of chemistry in Aberdeen Univer- 1965 is an invaluable source of relevant professorship he devoted himself to sity in 1914 where he remained until information.

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