it; The Hydrogen Bomb: In [he lec/mical and strategic discussion of last issue is continued, and a proposal is made for a ?rst step Iowarcl the international control of atomic weapons month l..ouis liidenour pub- lished an article on the hydrogen bomb in this magazine. The dis- cussion is continued in this second arti- cle because of the tremendous impor- tance of the is'sue. liidcnour described the essential parts of the theory of the nuclear reactions in the hydrogen bomb, and also discussed the likely effects of the bomb on our militarv security. 1. agree entirely with his view that the'cre- ation of the ll?l)oinb makes our country more vulnerable rather than more se- cure. It remains for me to discuss two things: 01] the technical side'. i shall try to clarify the many misconceptions that have crept into the discussions of the ll-homb in the daily press. On the po- litical side, I wish to take up the moral issue and the meaning of the bomb in the general framework of our foreign rela- tions. Everybody who talks about atomic energy knows Albert Einsteins equation l'i viz., the ei'iergy release in a nu- clear reaction can be calculated from the decrease in mass. in the fission of the uranini'n nucleus, one tenth of one per cent of the mass is converted into energy; in the fusion of four hydrogen nuclei to form helium, seven tenths of one per cent is so converted. \Vhen these statements are made in newspaper re- ports, it is usually implied that there ought to be some way in which all the mass of a nucleus could be converted into energy, and that we are merely waiting for technical developments to make this practical. Needless to say, this is wrong. Physics is sufficiently far de- by Hans A. Bethe veloped to state that there will never be a way to make a proton or a neutron or any other nucleus simply disappear and convert its entire mass into energy. It is true that there are processes by which various smaller particles?positive and negative electrons and mesons?are an? nihilated, but all these phenomena in- volve at least one particle which does not normally occur in nature and therefore must first be created. and this creation process consumes as much energy as is afterwards liberated. All the nuclear prt.)cesses from which NOTE The author is responsible only for the statements that appear in the text of this article. The illustrations and the captions that accon'ipany them were pre- pared by the editors. The infor- mation contained in the illustra- tions was compiled on the basis of previously published material. energy can he obtained involve the re- arrangement of protons and neutrons in nuclei, the protons and neutrons them- selves remaining intact. l?Iundreds of experin'iental investigations through the last 30 years have taught us how much energy can be liberated in each trans- formation, whether by the fission of heavy nuclei or the fusion of light ones. In the case of fusion, only the combina- tion of the very lightest nuclei can re- lease very large amounts of energy. \Vhen four hydrogen nuclei fuse to form helium, .7 per cent of the mass is trans- formed into energy. But if four helium nuclei were fused into oxygen, the mass would decrease by only .1 per cent; and the fusion of two silicon atoms, if it ever could occur, would release less than .02 per cent of the mass. Thus there is no prospect of using elements of medium atomic weight for the release oif nuclear energy, even in theory. llti main problem in the release of nuclear ei?lergy in those cases that we can consider seriously is not the amount of energy released?this is always large enough?hut whether there is a mecha- nism by which the release can take place at a sufficient rate. This consideration is almost invariably ignored by science re- porters. who seem to be incurahly fas- cinated hv in fusion the rate of reaction is governed by entirely different factors from those in fission. Fission takes place when a nucleus of uranium or plu- tonium captures a neutron. Because the neutron has no electric charge and is not repelled by the temperature has no important influence on the fission re- action; no matter how slow the neutron, it can enter a uranium nucleus and cause fission. in fusion reactions, on the other hand. two nuclei, both with positive elec- tric charges. must come into contact. To overcome their strong mutual electrical repulsion, the nuclei must move at each other with great speed. Ridenour ex- plained how this is achieved in the lab- oratory by giving very high velOcities to a few nuclei. This method is very ineffi- cicnt because it is highly unlikely that one of the fast projectiles will hit a target nucleus before it is slowed by the many collisions with the electrons also present in the atoms of the target. There- fore the energy released by nuclear reac- tions in these laboratory experiments is always much less than the energy in- vested in accelerating the particles. The only known way that energy can be extracted from light nuclei by fusion is by thermonuclear reactions. those which proceed at exceedingly high tem- peratures. The prime example of such re- actions occurs in the interior of stars, where temperatures are of the order of 20 million degrees Centigrade. At this the average energy Of [In atom is still only 1,700 electron volts? much less than the energies given to nu- clear particles in ?atom smashers.? But all the particles present?nuclei and elec- trons?have high kinetic energy, so they are not slowed down by colliding with one another. They will keep their high speeds. Nevertheless, in spite of the high temperature, the nuclear reactions in stars proceed at an extremely slow rate; only one per cent of the hydrogen in the sun is transformed into helium in a bil- lion years. Indeed, it would be catastro- phic for the star if the reaction went much faster. - BLAST EFFECT of present and proposed alomie weapons is projected on a map of New York Cit" the surrounding area. A uranium bomb set elf above SCIENTIFIC AMERICAN omcc in midtown would cause se- vere destruction within a radius of a mile circle) a hydrogen bomb 1,000 times more powerful would re destruction within .10 miles (largo circlt?i . ea "80 SCVC The temperature at the center of a star is kept high and very nearly con- stant by an interplay ol 11 number of physical forces. The radiation produced by nuclear reactions in the interior can escape from the star only with great dil? i?icult?y. it proceeds to the surface not in a straight line but by 11 complicated, zig- zag route, since it is constantly absorbed by atoms and re-emitted in new direc- tions. It is this slow escape of radiation that maintains the high interior tempera- ture, which in turn maintains the ther- 111onuclcar reactions. Only a star large enough to hold its radiations for a long time can produce significant amounts oi energy. The sun's radiation, for example. takes about 10,000 years to escape. A star weighing one tenth as much as the sun would produce so little energy that it would not be visible, and the largest planet jupitcr, is already so small that it could not maintain nuclear reactions at all. [his rules out the possibility that the earth's atmosphere, or the ocean, or the earth's crust, could be set ?on fire? by 11 hydrogen Superbomb 11nd the earth thus be converted into a star. Be- cause of: the small mass of the bomb, it would heat only a small volume of the earth or its atmosphere, and even if nuclear reactions were started. radia- tion would carry away the nuclear energy and the or than circle) its blast eil?ect. fatal burns at dislamfcs up to 41,000 to 5,000 feet. (811111? . A hydrogen bomb would cause fatal burns at distances of 20 miles or more (large circle) tants ol'Cllit'ag1i1 and its?suburbs could thus be wipvd out. much laster than it developed. and the temperature would drop rapidly so that the nuclear reaction would soon slop. ll. t'herrnonuclcar reactions are to be initiated on earth one must take into consider1?1tio11 that any nuclca1 c11c1<1\ 1elc11sed ill be carried a\\111v11apidl\1 in radiation so that it will not be possible to keep the tempen 1t111c high loi a longr time ?lliltf" elo1e it the 1'1c1ction is to pro- ceed at all it must pruou ed quickh Reaction times oi billions ol ar,s like those in the sun, uould nex or lead to an appreciable energy release; we must think rather in terms of 11?1illionlhs of 11 second 011 the other hand on earth we have a choice ol matmials: whereas the stellar reactions can use only the ele? ments that happen to be abundant in stars notabb1 ordinar\1 hydrogen. can choose any elements we like for our thermonuclear reactions. shall ob? viously choose those with the highest reaction rates. The reaction rate depends first of all. and extremely sensitively, on the product of the charges of the reacting nuclei; the smaller this product. the higher the re? action rate. The highest rates will there- fore be obtainable from 11 reaction be? tween two hydrogen nuclei because hv - diogen has the sionallest possible chawc ?one unit. (The plinci p11l 1'101ctions in FLASH EFFECT of a hydrogen bomb :l1000 timvs more powerful than present bombs would be relatively great- The .lI'liroshima bomb caused The inhabi- .JI I9 I . 8+ 1.4 mev 100.000.000.000 years i . . 8 . l'lI "83+ 5mev .5 second 3 H3 H1 l'ltl4 l'lV 20 mev .05 second H2 H2 He3+n 3.2 mev .00003 second mev .00003 second 9 8 6? 0 H2 He?+ 17mev .0000012 second ?39 8 89 "0 He4+ n+n 11 mev :8 THE NUCLEAR involving the three isotopes of hydrogen, H: tdeutcrimn) and fl? Hritinm) illustrate a fundamental consideration in making a hydrogen 'l?hc rcartions are at left, the energy released by each is in center. the little required l'or each is at right. The reactions in- VoIVing the heavier isotopes. of hydrogen proceed at a much faster rate. 20 1 stars are between carbon, of charge six, and hydrogen.) We can choose any oi" the three hydrogen isotopes, of atomic weight One (proton), two (deuteron) or three (triton). These isotopes undergo different types of nuclear reactions, and the reactions occur at different rates. The fusion of two protons is called the proton-proton reaction. It has long been known that this reaction is exceedingly slow. As Robert E. Marshak stated in his ?article, ?The Energy of Stars,? in the January issue of this magazine, the pro- ton-proton reaction takes 100 billion years to occur at the center of the sun. Ridenour pointed out that the situation is quite different for the reactions using only the heavy isotopes of hydrogen: the deuteron and triton. A number of reported measurements by nuclear physicists have shown that the reac- tion rates for this type of fusion are high. A further variable governing the rate of the reaction is the density of the ma- terial. The more atoms there are per unit volume, the higher the probability for nuclear collisions. it is also well known, as Ridenour noted, that the reactions would require enormous temperatures. Whether the temperature necessary to heat heavy hy- drogcn sufficiently to start a thermonu- clear reaction can be achieved on the earth is a major problem in the develop- ment of the l-l-bomb. To find a practical way of initiating I?l-bombs will require much research and considerable time. HAT would be the effects of a hy- drogen bomb? tiidcnour pointed out that its power would be limited only by the amount of heavy hydrogen that could he carried in the bomb. A bomb carried by a submarine, for instance, could be much more powerful than one carried by a plane. Let us assume an lf-l)oml) releasing 1,000 times as much energy as the Hiroshima bomb. The ra- dius of destruction by blast from a bomb increases as the cube root of the increase in the bombs power. At Hiroshima the radius of severe destruction was one mile. So an ll-bomb would cause almost complete destruction of buildings up to a radius of .10 miles. By the blast effect alone a single bomb could obliterate al- most ali of Greater New York or Moscow or London or any of the largest cities of the world. But this is not all; we must also consider the heat effects. Aboiit 30 per cent of the casualties in Hiroshima were Caused by flash burns due to the intense burst of heat radiation from the bomb. Fatal burns were frequent up to distances of 4,000 to 5,000 feet. The radius of heat radiation increases with power at a higher rate than that of blast, namely by the square root of the power instead of the cube root. Thus the li- lmml) would widen the range of fatal heat by a factor of 30; it would burn people to death over a radius of 11p to 2.0 miles or more. It is too easy to put down or read numbers without under- standingt t;hem one must visualize what it would mean if, for instance, Chicago with all its suburbs and most of their i11- habitants were wiped out in a single flash. ln addition to blast and heat radiation there are nuclear radiations. Some of these are instantaneous; they are emitted by the exploding bomb itself and may be absorbed by the bodies of persons in the bombed area. Others are delayed; these come from the radioactive nuclei formed as 11 consequence of the nuclear explosion, and they may be confined to the explosion area or widely dispersed. lhe bombs, both A and II, emit gamma rays and neutrons while they explode. Either of these radiations can enter the body and cause death or radiation sick- ness. It is likely, however, that most of the people who would get a lethal dose of radiation from the l'l-bomb would be killed in any case by flash burn 111' by collapsing or burning buildings. There would also be persistent radio- activity. This is of two kinds: the ?ssion products formed in the bomb itself, and the radioactive atoms formed in the en? by the neutrons emitted from the bomb. Since the l-l-bemb must be triggered by an A?bomb, it will produce at least as many fission products as an A-bomb alone. The neutrons produced by the fusion reactions may greatly i11- crease the radioactive effect. They would be absOrbed by the bomb case, by rocks and other material on the ground, and by the air. The bomb case could be so designed that it would become highly radioactive when disintegrated by the explosion. These radioactive atoms would then be carried by the wind over a large area of the bombed country. The radioactive nuclei formed on the ground would contaminate the center of the bombed area for some time but prob- ably not for verv long because the con- stituents of soil and:3 buildinus do not l111111 many long- lived radioactive nuclei by neutron capture. Neutrons released in the air are finally captured by nitrogen nuclei. which are thereby transformed into radio-active car'? borr .l 4. This isotope, however, has a long years?and therefore its radio: 1ctivitv is relatively weak. Conse? quently even if 111: 111V bombs were ex- ploded, it is not likely that the carbon would become dangerous. T1113 decision to proceed with the de- velopment of hydrogen bombs has been made. I believe that this decision settles only one question and raises 11 hundred in its place. \Vhat will the bomb do to our strategic position'.J \Vill it re- store to 11s the Super rorrtv in armament that 11e possessed before the Russians obtained the A- bomb. \Vill it impro1e our chances of winning the next war if one should come? \Vill it diminish the likelihood that We should see our cities destroyed in that war? \Vill it serve to avert or postpone war itself? How will the world look after a war fought with hydrogen bombs? I believe the most important question is the moral one: C1111 we who have al- ways insisted on 1"11orality and human decency between nations as well as iri- side our own country, introduce this weapon of total annihilation into the world? The usual argument, heard in the frantic week before the President 5 deci- sion 11nd frequently since, is that we are fighting against a country which denies all the human values we cherish, and that any weapon, however terrible, must be used to prevent that country and its creed from dominating the world. lt is argued that it would be better for us to lose our lives than our liberty, and with this view I per's01'1ally agree. But 1 be- lieve this is not the choice facing us here; I believe that in a war fought with hydrogen bombs we would lose not only many lives but all our liberties and hu- man values as well. \Vhoever wishes to use the hydrogen bomb in our conflict with the U.S.S.R., either as a threat or in actual warfare, is adhering to the old fallacy that the ends justify the means. The fallacy is the more obvious because our conflict with the U.S.S.R. is mainly about means. .It is the means that the is using, both in dealing with her own citizens and with other nations, that we abhor; we have little quarrel with the professed aim of providing a 1leCcnt standard of living for all. \-Ve would invalidate our cause if we were to use in our fight means that can only be termed mass slaughter. \Ve believe in personal liberty and human dignity, the value and impor- tanCe of the individual, sincerity and openness in the dealings between men and between nations, prosperitv for all and peace based on 1111111111 trust. All this is in great contrast to the methods 11 hich the Soviet Government uses in pursuing its aims and which it believes necessary in the ?beginning phase? of Cornn'run ism ?which by now has lasted 33 years. Regirnentation of the private lives of all citizens, systematic education in spying upon one?s friends ruthless shifting of populations regardless of their pc1sonal ties and pr'eferc1"11es, inhuman treatment of prisoners in labor camps, suppression 11l free speech, falsification of history in dealing both with their own citizens and with otl"1e1 nations, violation of promises and tr'c1 rtics and the distorted interpret 11? [ions oflered in eXcuse of these viola- tions?these are some of the methods of the U.S.S.R. which are hateful to the people of the \Vest?ern \Vorld. But if we wish to fight against these 111cthods, our methods must be clean. believe in peace based on mutual J. trust. Shall we achieve it by using hy- drogen bombs? Shall we convince the Russians of the value of the individual by killing millions of them? if we fight a war ar'rd win it with l'l-bornbs, what history will remember is not the ideals we were fighting for but the methods we used to accomplish them. meth- ods will be cornp1 ared to the warfare of Genghis Khan. who ruthlessly killed every last inhabitant of Persia. HAT would an all-out war fought with hydrogcr'r bombs mean:J It would mean the obliteration of all large cities and probably of many smaller ones, and the killing of most of their inhabi? tants. After such 11 war, nothing that re- sembled present civilization would 1?nair1. The fight for more surviVal would dominate e1erything. he destruction of the cities might set technologv back 11 hundred years or rum in 11 gener ration even the knowledge of technologv and science might disappear. because there would be no opportunity to practice them. Indeed it is likely that technology and science, having brought such utter misery upon man, would be suspected as works of the devil, and that a new Dark Age would bcein on earth. \Ve know what s1c1l destruction does to the moral values 11f a people. have seen how 1111?111y ahead} (lemor'alized by the Nazis, lost all sense of morality during and after the war the bare necessities of life, food. clothing and shelter were lacking. Dc- 1r1ocracy and human decency were ernp? ty words; there was 1111 reserve strength left for such luxuries. If we have learned any lesson from the aftermath of \Vorld War ll, it is that physical destruction brings moral destruction. have also learned that prosperity is the best shield against communism and dictatorship. and in this knowledge we have poured billions into Eu- rope to restore her economy. This gen- erosity has won us more friends than anything else we have done. But after the next war, if it were fought with atomic and hydrogen bombs, our own country would be as grievously de- stroyed as Europe and the and we could no longer afford such generosi? ty. It would be everyone for himself, and evel'yor'le against the other. It is ironic-1d that the U. S. of all countries should lead in developing such methods of warfare. The 1'11ilit'ary meth- ods adopted by this nation at the outset of the Second \Vorld \Var had the aim of conserving lives as much as possible. Determined not to repeat the slaughter of the First \Vor'ld ?7111', during which hundreds of thousands 11f soldiers were sacrificed in fruitless frontal attacks. the U. S. high command substituted war bv machines for war by unprotected men. But the hydrogen bomb carries 111cc1l1111i? Cal w: 1rf1'11e to ultim: absurdity in 2 dcteating its own aim. Instogad ol' sav- ing lives. it takes many more lives; in place of one soldier who would die in battle, it kills a hundred 11011C11111l)atant civilians. Surely it is time for us to re- consider what our real intentions are. One mav well ask: \th advance such 111 guments 11 ith rel'cunce- to the 11- bomb and not atomic bombs in