University of Central Florida STARS PRISM: Political & Rights Issues & Social Movements 1-1-1946 Atoms, bombs and you Kirtley Fletcher Mather Find similar works at: https://stars.library.ucf.edu/prism University of Central Florida Libraries http://library.ucf.edu This Book is brought to you for free and open access by STARS. It has been accepted for inclusion in PRISM: Political & Rights Issues & Social Movements by an authorized administrator of STARS. For more information, please contact [email protected]. Recommended Citation Mather, Kirtley Fletcher, "Atoms, bombs and you" (1946). PRISM: Political & Rights Issues & Social Movements. 830. https://stars.library.ucf.edu/prism/830 and You KIRTLEY F. MATHER &tony %b and You 16, 1945, uvihtion ONaZd'the threshold of a new age. Only a few persons hew it at the time. They were the htists, ttacSmi- dam, and Amy ~~ who saw the blinding flash of the explosion of the first atomic bomb at the testing station in the desert near La Alamos, New Mexico. Less than a month later, aJl the world had been informed. Hiroshima and Nagasaki were virtual- ly annihilatedfld japan had precipi- tousIy mrrendered to the victorious Allie?. Since then, most of us have been trying to comprehend the meaning of this achievement of modern wience, to appraise its terrifying po- tentialitiea for the future of the hu- man my,to discover what changes it may bring in our own lives and in the Iife of our nation. From the offi- cial reports of the War Department, the mcfully worded resolutions of the several newly organized associa- tions of -scientists, the pronounce- ments of the experts in nuckar phys- ics, and the speeches of the politicians, several supremely important ideas are now dear. Only when those ideas are generally recognized by those respon- sible for the formulation of public opinion can therc be any justifiable hope that this latest achievement of the human intellect wiIi prove a bless- ing rather than a curse to mankind. Shds Greatest Ackmmt Never before has there been auch a dramatic and arresting demomtmtion of the validity of the scientific method for acertaining math and utilizing natural resources. Measured by any criteria that might be applied the project that has been secretly under way since I940 and haa +lminatcd in the production of at least three atomic bombs is the mcmt stupendous achieve- ment in all the amla of research and technology. It rtprcsents the ultimate in both orphition and cooptration, in practid application of ahtract theory, and in the we of scientific methods of observation and =pi- ment. Grave indeed is the daqpthat 6 the general public will be forever con- fident that there is absolutely nothing impossible fur "science" to achieve. As a matter of faa, even the well- trained &entist is probably tempted to think so himself. In a vague sort of way, almost every- one appreciates the fact that atomic energy t something new, but it is doubtful whether many people ade- quately mmprehend its utter novelty. To appreciate what atornic energy really -means, one must have some knowledge of the subdcmxopic structute of matter and the nature of the fundamental units of which the materid universe appears to be con- structed. Wbd Atoms Are Like Almost every high do01 graduate now know that everything around us -whether gas, liquid, or solid, wheth- er animal, vegetable, or mind-is composed of molecules, the tiniest particles into which matter may be subdivided by any ordinary physical means. These molecules are so small that only the very largest of them are big enough to be secn wen under the tremendous enlarging power oE the modern electron rnimpt. But each molecule is comeof still smaller units-the now widely pub lickd atoms. If all the atoms in a molecule are of one kind, we say it is an element; if merent kinds of atotns are organized to make a moIecule, we say it is a compound. Atoms are so small that if you ar- ranged 500,000 of them of average size, aide by side in a line, that Iiue wduld just about $pan the width of a human hair. Yet within each oE those atoms there is an atomic nucleus bav- ing radically diflFetent properties from the rest of the rtructure. Take one bE the larger atoms, such as uranium, ad fl in imagination expand it until its periphery endm a hundred acres; its nucleus would then be about tht size of a baseball. The nucleus of most atoms of hy- d rogen is a fundamental unit called a ' proton. It carries a unit charge of positive electricity and therefore an control a single electron, another fun- damental unit that behaves as though it were nothing but a cnit charge of negative electricity. That single clec- tron occupies all the space within the hydrogm atom outside the nucleus and we say therefore that hydrogen is the element having atomic numbcr one in tlle line-up of elements. The nucleus of an atom of helium is more complicated. It contains two protons and two other fundamental units called neutrons, all held in a dose, strong orgmktiw by the "binding energy" within itsel£, A neutron behaves most of the time just B as though it was a proton and an elec- tron welded inescapably together. That means it has approximately the same mass as a proton-the mass of an electron L so trivial that for all practical purposes it can be neglectd altogether-but is electridly neutraI, the positive charge of the proton h- iag exactly balanced by the negative charge of the electron. Thus the nu- cleus of the helium atom k four times as heavy as the nucleus of the hydro- gen atom, and because it con& two protons it can control two electrons in the space around it. Helium is therefore atomic number two in the line-up, even though its mass number is four. Lithium is number three in the atomic list. Its nucleus contains three protons combined with either three or four neutrons. And so we might con- tinue down the line through carbon, number six, oxvgcn, number eight, to lead, number eighty-two, radium, number eightyeight, and uranium, number ninety-two. In every instance the atomic number indicates how many protons there are in the nucleus and therefore how many electrons are kept under control in the relatively large space inside the atom but out- side the nucleus. And always, with the sole exceptions of hydrogen and one very rare variety of helium, there areatlatasmmyneutroflsapm - tons, all bound together within those infinitesimal nuclei. The mw num- ber is always equal to the sum of the protons and neutrons. Power Before 1942 Since the earth fist began to circle the sun, until December, 1942, all the work of the world had been done by means of power that was either elec- tronic, radiational, or gravitational in nature. Chemical reactions that liber- ate energy, whether thty involve the combustion of coal or oil or the ex- plosion of dynamite or TNT, result from interplay of electxom in the rel- atively large spaces inside atoms but outside atomic nuclei. A11 such reac- tions yield amounts of energy measur- ing only three, six, eight, or, at most, ten electron-volts, the unit now wed for announcing the quantity of energy involved in any transformation of matter. Poww from tbe hods IVncIw December, 1942, was the date just mentioned because it was during tbat month that a uranium "pile" htbe- gan to operate spontaneody by a chain reaction invoIving the release of the binding energy from withiin the _ atomic nucleus. That epmh-making experiment was successfd1y accom- plished in a squash court beneath the west side of the athletic stadium at the University of Chicago, behind an im- penetrable curtain of military secreq. But the experiments and observations that provided the knowledge and but- tressed the theory prerequisite to its success had been known to the atomic phpsitists of all the world prior to the fall of 1939. Wbd B *'Cbkn Re&odt Is Like The story is long and complicated; but here are its highlights. If the ek- ment beryllium (no. 4) is expod to the natural radiation from radium, it wcasiondy releasa a neutron from its nucleus, The neutron moves like a projectile from a gun at a speed that may be anywhere between twenty thousand and a hundred thousand mires per second. If it hits the nucIeus of a uranium atom at just the right velocity, it may cause that nucleus to break into two hpents and at the same time release two to gix or eight other neutrons and a considerable hction of the binding energy that had held all its protons and neutrons together. This is what the physicists call nuclear fission. The binding energy thus released is only the dif- ference between that in the original uranium nucleus and that remaining within the fission kqpents, but its intensity is between 100 and 150 mil- lion elkwon-volts. If two or more of 18 ' he releaed neutrons hit the nuclei of two or three adjacent atoms of uranium at just the right sped, they too may be subjected to nuclear fission and thus the process may spread by chain reaction throughout whatever mass of uranium atoms may be avay- able and a terrific explosion may result. The Role of Urr#uanrn235 But you doubtless noted the long string of "ifs" and "mays" in the pre- ding paragraph. There is a atch behind each of them, and it was not until 1938 and 1939 that the research scientists dealing with nuclear hion succeedd in "breaking" the atomfc "code." There axe two different kinds of udum atoms commonly present in any uranium-baring mineral.