The Neutron and the Bomb, page 50
The general reason is that the Americans are, as you know, still apt to be suspicious and alarmed on security grounds and Bohr is, of course, regarded as a British agent. As he is always popping round, some of the Americans naturally wonder what he is really up to.
The special reason is that he has got himself involved with [Justice] Frankfurter who, as you know, having more or less accidently obtained knowledge of T. A., is taking a keen interest in it, much to the embarrassment of most of the people involved on the American side. You can readily understand how the activities of Frankfurter and Bohr together could muddy the waters at a moment when we particularly want to keep them clear.
Apart from Bohr’s voice of conscience, there was a report from six scientists working on the project in Chicago on the social and political implications of the nuclear bomb. This group was led by James Franck,41 who had shared the 1925 Nobel Prize in Physics and who had previously shown the stamp of moral courage when resigning from his Chair at the University of Göttingen in 1933 as a personal protest against Hitler’s Nazi regime. His report regarding the use of the bomb sounded a warning against any action by the US in the present conflict, which might undermine its future standing in the international community and make the international control of nuclear arms more problematic. In particular, the scientists counselled against dropping bombs on Japan without prior warning. The Franck Report surfaced in Washington in June 1945,42 and at the request of the US War Office was considered by a scientific panel comprising Oppenheimer, Fermi, Lawrence and Compton, the head of the Chicago Metallurgical Lab. It was Arthur Compton who had commissioned Franck to write the document only two weeks earlier. At the end of the panel’s deliberations, Oppenheimer drafted a statement43 which effectively dismissed the idea of a preliminary, non-combat use of the bomb: ‘We recognize our obligation to our nation to use the weapons to help save American lives’, he wrote, adding: ‘We can see no acceptable alternative to military use... We can propose no technical demonstration likely to bring an end to the war.’ Oppenheimer’s panel did, however, endorse the Franck Report’s recommendation that the Soviets should be informed before the bomb was dropped on Japan, on the basis that if the secret was shared with them, they would feel less threatened and therefore be less likely to enter a nuclear arms race with the US.
Although the decision would finally rest with the President, Oppenheimer’s panel at least had some indirect influence. President Truman had only learned about the existence of the Manhattan Project following Roosevelt’s death in April. He was briefed both by his Secretary for War, Henry Stimson, and General Groves on the technical aspects of the Project, its military potential, and also the challenge of international control. Truman agreed to Stimson setting up the Interim Committee — a body of civilians which included Bush and Conant — to consider these matters until they came into the public domain after the first bomb was used. The committee, in its short existence, came to be dominated by James Byrnes, who would later become a dominant figure in American nuclear politics as Truman’s Secretary of State. The Interim Committee44 had little real influence on the decision to use the atomic bomb (the notion that it did was derided by Groves as ‘plain bunk’).
Chadwick learned of the Franck Report, probably from Groves, and he was well aware of fundamental concerns that were troubling a few scientists such as Bohr and Rotblat. He was less inclined to disclose information to the Soviets at this stage. Although not overtly political, Chadwick certainly did not share Rotblat’s socialist sympathies, and his close relationship with General Groves had made him acutely aware of the future military threat posed by the Soviets. Philosophically, he believed that there should be international cooperation to avoid potentially catastrophic competition, but he could not see how the necessary safeguards could be enforced and was constitutionally opposed to excessive risk taking in such a dangerous sphere.
In the early summer of 1945, there was still no guarantee that the plutonium bomb would work because of the untested implosion method of detonation, and there was insufficient 235 isotope to manufacture a uranium bomb. These concerns weighed heavily with Chadwick on the question of whether there should be a preliminary demonstration of the bomb before it was used in earnest. In his opinion, there was not ‘enough material to play around with’; more subtly, even if it could be made to work, he was concerned there was no readily identifiable group who could be assembled at will, to whom the bomb could be demonstrated, and who would then be able to ensure that Japan surrendered.45
On 4 July, Chadwick was invited with Halifax, the British Ambassador, to a meeting of the Combined Policy Committee in the Pentagon.42 Groves also attended, but the formal business was conducted between Stimson, for the US, and Field-Marshal Sir Henry ‘Jumbo’ Wilson, for the UK. The prime purpose was to satisfy the conditions of the Quebec Agreement in that the Americans needed to obtain the consent of the British before using the bomb or disclosing its existence. Agreement to use the bomb against Japan was readily given by Field-Marshal Wilson, but there were reservations both on the narrow issue of whether Stalin should be told about the bomb at the forthcoming Potsdam Conference and on the broader question of a public scientific report to be issued once the bomb had been used. It was decided that a sub-committee comprising Bush, Chadwick and Groves should draft guidelines governing the general release of information. Chadwick’s opinion carried no particular weight, although it would be of interest to Groves who had come to have such a high regard for his judgement. The two men would meet several times a week, usually in Groves’ office, and would talk privately for 15 or 30 minutes before others were admitted to the room. Their mutual confidence was now so great that it was natural for Chadwick to confide in him, although the brusque General would still on occasion startle him. Once he sought advice from Groves, when an off-hand remark about the treatment of captured German scientists had been transmitted directly to London as Chadwick’s serious policy suggestion. It appears he had stated that the scientists should be kept apart from the French and the Russians, and sent to the Ruhr Valley to teach. By this time, the likes of Anderson and Akers in London tended to pay attention to any of Chadwick’s opinions. Groves’ response ‘that the German scientists should all be shot as they were undoubtedly as great war criminals as anyone else in Germany’ was ‘not relished by Dr Chadwick’.46
On the same Independence Day that the CPC met in Washington, Peierls47 wrote to Chadwick from Los Alamos. There would be no more evening colloquia until after the Trinity test, he said, ‘since people can hardly be expected to have the detached attitude necessary for that kind of discussion’, such was the level of anticipation. At the last meeting in the series, Hans Bethe had reviewed the theoretical basis for their predictions of the bomb’s efficiency. In Peierls’ view the estimates were reasonable, providing ‘nothing goes wrong with the detonators, that the initiator works, and there is no predetonation’. Although the newly insulated detonator wires seemed much more reliable, and the discrepancies concerning the shock waves from the lenses and the compressibility of the core material were being narrowed, there was still an abundance of reasons for Chadwick to remain sceptical about how all this would work in practice.
While the dramatic events in New Mexico were progressing rapidly to their historic climax, Chadwick wanted to concentrate on them to the exclusion of everything else, and his correspondence shows he was increasingly unwilling or unable to give his mind to other matters. Rotblat wrote to him regularly about the state of the Liverpool department. He was very troubled by the shortage of staff, the status of the honours course, and the future of the research programme, which Chadwick had so carefully nurtured in the late 1930s. The university were contemplating the purchase of a new site for a bigger cyclotron after the war, and desperately wanted Chadwick’s advice. For once, Chadwick did not reply to these enquiries and Rotblat was left in limbo. The lack of communication fed the growing belief that Chadwick would not return to Liverpool after the war.48
Another voice that was uncharacteristically ignored by Chadwick during this period was Mark Oliphant’s. He had returned to Birmingham, with Chadwick’s help, but was still agitated about other British scientists being kept on at Berkeley and not being allowed to return to their universities in Britain, where, in his opinion, they were desperately needed. He saw this as a political ploy on General Groves’ part to keep them tied up, ‘wasting their time on trivialities’. He told Philip Moon49 that he thought he had persuaded Chadwick that this was the true state of affairs, and expected him to arrange their return as quickly as possible. Oliphant confessed to Moon he felt unhappy that he ‘found it necessary to press [Chadwick] so hard.’ Oliphant continued: ‘He has a thankless task to perform, and I know of no-one else who could have carried on through all the vicissitudes, and despite the indignities he has had to suffer.’ Regardless of this, Oliphant felt that ‘our task is now here and our loyalty is to Britain — not to General Groves’. In truth, by this stage, the momentum of the Manhattan Project was irresistible, and Chadwick would have found it impossible to dissociate himself from Groves, even if he had wished to do so. Instead Chadwick46 continued to strive for the placement of British personnel in key positions so that they would gain as much valuable information as possible. He wanted to include at least one British scientist in the base party for the forthcoming Trinity test, in addition to himself. Ernest Titterton had proved himself to be such a master of electronics that he was entrusted with the task of generating the electronic pulse which would fire the plutonium bomb. Although Groves was reluctant to include another English scientist, Oppenheimer had recommended Otto Frisch, who Chadwick did not think would be a good choice because he was too inclined to make unnecessary, last minute, scientific changes. His preference was for Penney, who had been advising on the placement of bunkers and shelters for observers at the test. Penney was also to be responsible for certain critical measurements such as the ignition of structural materials from the radiant heat emitted by the blast.43
The revised date for the Trinity test was Monday, 16 July. A hill called Compañia, 20 miles northwest of ground zero was selected as the viewing point for some of the most senior scientists, including Chadwick. He had been driven there across the Jornada del Muerto with Edwin McMillan, a physicist from Berkeley. To pass the time on the journey, they discussed the question of international control of atomic power and specifically whether the Soviets should be informed about the newest and most devastating weapon in the history of warfare. Chadwick dismissed the notion out of hand: ‘Why should we? They don’t give us anything.’50 At Compañia, they joined McMillan’s boss, Ernest Lawrence, as well as Hans Bethe and Edward Teller.
It has been written that Chadwick came to the Trinity site ‘to see what his neutron was capable of’.51 The most devout of Rutherford’s followers, Chadwick would have instantly recoiled from any suggestion of proprietary rights to the neutron. At the Cavendish, subatomic particles remained the property of God;52 even Rutherford was only the midwife to the birth of the α-particle. Nevertheless, it is true that Chadwick’s discovery of the neutron marked the unintentional first step towards man’s loss of innocence in the field of nuclear weaponry. There had been other crucial but unwitting contributions, most notably the elucidation of nuclear fission, as we have seen. With the outbreak of a conflict which threatened civilization in Europe, leading physical scientists recognized that the Nazi regime could not be allowed to secure a lead in this deadly race and had deliberately set themselves the task of constructing a bomb of unprecedented force. Chadwick had been in the forefront of this effort, first in England, where he tirelessly co-ordinated work at several universities despite all the difficulties in communication imposed by the war; apart from his accustomed role as scientific mentor, he smoothed personal and academic rivalries, and drafted the crucial Maud Report, which convinced not only the British leaders but more importantly those in the United States that a nuclear weapon was feasible in the present war. When the Americans eventually took over the endeavour and turned it into the mightiest military engineering project the world had ever seen, Chadwick stayed at the centre of activities, lending unswerving support to General Groves and in return ensuring a continuing stake for Britain as a nuclear power. Now all these years of relentless strain and responsibility were to be put to the most dramatic test.
The weather was appalling — tropical thunderstorms, lashing rain and high winds. They waited together in the cold, black, desert night. Chadwick, like Groves, was concerned that the weather would mean a postponement in the realization of ‘the boldest and certainly the most expensive experiment in scientific history’.53 Groves, who was under immense pressure to conclude the test while President Truman was with Stalin at the Potsdam Conference, reluctantly put his faith in the meteorologist who predicted the storms would abate at dawn, and ordered the detonation for 5.30 am. Chadwick53 described the birth of the atomic age:
In the faint light before dawn, the last few minutes went slowly by as we prepared ourselves for the critical moment. I sat on the ground holding a piece of dark welder’s glass before my eyes, shielding the sides with my hands. Suddenly I saw an intense pinpoint of light which grew rapidly to a great ball. Looking sideways, I could see that the hills and desert around us were bathed in radiance, as if the sun had been turned on by a switch. The light began to diminish but, peeping round my dark glass, the ball of fire was still blindingly bright... The ball had then turned through orange to red and was surrounded by a purple luminosity. It was connected to the ground by a short grey stem, resembling a mushroom.
Meanwhile, about 100 seconds after the appearance of the pinpoint of light, had come the sound of the explosion, sudden and sharp as if the skies had cracked. This was followed by a long rumbling noise — the echoes thrown back by the surrounding hills — as if huge noisy wagons were running around.
Although I had lived through this moment in my imagination many times during the past few years and everything happened almost as I had pictured it, the reality was shattering. What had begun in a few simple ideas had at last been put to the test of experiment, and the awe-inspiring nature of the outcome quite overwhelmed me.
Now that the test had been successful enough to ensure an effective weapon, Chadwick thought the next logical step was to use it in combat as soon as possible. That is not to say he did not harbour serious doubts about its use. Until the Trinity test he may have retained a quiet, slight, hope that it would not work, although his scientific intellect had long led him to expect it would. Once the Trinity test was over, Chadwick returned to Washington, where for the first time in many months he could attempt to turn his mind to other things. But he found himself shattered by what he had witnessed at Alamogordo, whenever he thought about it; for the first time in his life, he was unable to concentrate at will. He even found himself being indecisive about plans for the Liverpool department, and in a letter written to Rotblat54 on 26 July, he was almost apologetic:
I wish to add that it is very difficult for me to give proper consideration to such matters as these under the present circumstances. I have really very little time to spare for them and no one to discuss them with, and, what is worse, I am now quite out touch with conditions in the laboratory. I am therefore content to leave a great deal, almost everything in fact, to the judgement of Roberts and yourself, etc. This does not mean that I am comparatively uninterested. Far from it. But I am living in a different world from which I cannot easily return.
The world became a truly different place on 6 August, when a single uranium-235 bomb exploded in the morning sky over Hiroshima. Three days later, an adaptation of Chadwick’s signature, polonium-beryllium, device was used to generate neutrons to initiate the fission process in an imploded mass of plutonium; and Nagasaki was devastated. On 10 August, Japan, with her navy and air force already decimated, agreed to terms for surrender, and the war finally ended on 14 August. America had unleashed a weapon of unimaginable terror, her military were cock-a-hoop and already her politicians were plotting to keep the technology the exclusive property of Uncle Sam. Great Britain, which still had imperial pretensions, were quietly determined to produce their own bombs, and unknown to the West, the Russians had already made a start by acquiring vital information from at least two scientists, Fuchs and Nunn May, working on the North American continent.
Even before detailed assessments of the damage caused by the bombs at Hiroshima and Nagasaki were available, Chadwick thought it was a mistake to regard them, as some had suggested, as ‘merely a bigger and better bomb’. In his opinion, the two bombs already went ‘so far beyond any other weapon of destruction as to constitute a menace to civilisation’.55 Despite this chilling judgement, he never recanted the use of the bombs against the Japanese. He believed the decision was justified in an attempt to save the lives of American and Allied servicemen, as well as prisoners of war who would die in their thousands if Japan were slowly strangled by conventional methods of bombardment. On the moral question of tens of thousands of innocent Japanese civilians being killed at a stroke, he saw no difference between their fate and similar numbers who had perished in the fire bombing of Tokyo. Six years of war had irredeemably altered the public tolerance for atrocities and brutality. Chadwick found some grounds for hope in the way the bomb had been born out of this historic global struggle:55
It is, I think, fortunate that this weapon was developed and produced during the war, firstly because its development in time of peace would have occurred more or less concurrently in different countries and competition would thereby have been inevitable, and secondly because the sufferings and havoc of the present war have branded into our minds the merciless nature of war and have made us long for peace as never before.
