The First War of Physics (22 page)

The American entry into the war within a few days of the establishment of the S-1 programme meant that the constraints of the past few years had quickly vanished. Roosevelt stressed the importance of time at the expense of money – the Americans believed they were competing in a race in which the Germans already had a substantial lead.
¹
Given the uncertainties they faced, it was impossible for the S-1 Committee to determine which of the various routes to an atomic bomb was most favourable. The committee determined to pursue them all. ‘To embark on this Napoleonic approach to the problem would require the commitment of perhaps $500,000,000 and quite a mess of machinery’, Conant concluded.

On 17 June Bush proposed to Roosevelt that the US Army Corps of Engineers get involved in the S-1 programme alongside the OSRD, taking responsibility for process development, large-scale engineering design, selection of suitable locations and procurement of materials. Roosevelt approved the proposal.

Anderson vacillated at precisely the wrong time. Bush advised him of the proposed changes to the organisation of the S-l programme in June, but Anderson was not convinced of the value of full Anglo-American collaboration until the end of July, when he drafted a memo to Churchill:

We must, however, face the fact that the pioneer work done in this country is a dwindling asset and that, unless we capitalise it quickly, we shall be rapidly outstripped. We now have a real contribution to make to a ‘merger’. Soon we shall have little or none.

American policy-makers had already concluded that they could manage quite well without British help.

Negotiations to move Halban’s Cambridge team to America had foundered on the issue of security. This team had continued to work on a uranium–heavy water reactor, a project that was now seen as secondary to the main thrust of Tube Alloys. Although it now made sense to everyone involved to consolidate the S-1 and Tube Alloys reactor work at the Met Lab, foreign nationals were prevented from participating in secret American war projects. Bush thought that it might be possible to bend the rules for a team of British nationals, but Halban’s team actually had few British nationals in it. This proved to be an insurmountable problem. In truth, personality clashes, differences of opinion about priorities and the perception that the American work had already moved far ahead were also factors.

It was decided instead to transfer Halban’s team to Canada. The Canadian government eagerly accepted the suggestion, and terms were agreed in late autumn 1942. The work was to be administered by Canada’s National Research Council. Laboratory premises were found in Montreal.

Leftwandering activities

With the experimental projects to develop the material for a bomb under way, Compton had turned his attention to the physics of fast neutron reactions and the implications for bomb design. He had appointed Russian-born physicist Gregory Breit to lead this effort, but Breit quickly became frustrated by what he perceived to be a lack of progress and an intolerable lack of security. He resigned on 18 May 1942 to rejoin a navy project that he had worked on before becoming involved in the S-1 programme.
Compton, who had invited Oppenheimer to work on the project under Breit’s overall supervision, now asked him to lead the work.

Oppenheimer was a remarkable physicist, but a somewhat flawed human being. The son of Jewish immigrants grown wealthy in America, he had a tremendous capacity for learning. At the age of nine, he would challenge a cousin to ask him a question in Latin which he would then answer in Greek. This capacity was not, however, matched by a corresponding level of human empathy. He did not wear his learning lightly. As a young boy he would compensate his physical awkwardness and shyness by showing off. He could be boastful and patronising, and he developed an acid tongue. The impression left with school friends and, subsequently, with scientific colleagues and collaborators ranged from compassion to exasperation.

Oppenheimer was a polymath, with interests not only in science but also in psychotherapy and the arts. At Harvard University he had majored in chemistry, but had also studied Greek, architecture, classical literature and art. On graduating from Harvard he studied under J.J. Thomson at the Cavendish Laboratory in Cambridge, before moving on to Göttingen in Germany. In Göttingen he worked with James Franck and Max Born and met Heisenberg and English physicist Paul Dirac, among many other eminent theoretical physicists passing through during this period.

Compton had first met Oppenheimer in Göttingen in 1927. ‘A specialist in the problems of nuclear physics,’ Compton later wrote, ‘he was one of the very best interpreters of the mathematical theories to those of us who were working more directly with the experiments.’

After gaining his doctorate, Oppenheimer returned to Harvard before moving on to the California Institute of Technology in Pasadena. He put several offers of academic positions on hold for a year while he returned to Europe to continue his postdoctoral studies. He went first to Leiden in Holland to work with Paul Ehrenfest, and then to Zurich in Switzerland to work with Wolfgang Pauli, who had just completed the first part of a joint work with Heisenberg on quantum electrodynamics. He returned to America, and a position at the University of California at Berkeley, in July 1929. Lawrence had been appointed associate professor at Berkeley just a year before.

Oppenheimer was certainly talented, but he was more technician than innovator. He could refine and extend the original ideas of others, but was less able to produce original ideas of his own. On 22 April 1942, Oppenheimer had celebrated his 38th birthday. It was a widely acknowledged fact of scientific life that a physicist’s best work is done when young. Heisenberg had won the Nobel prize for work he had done in his late twenties. Einstein had won the prize for work he had published at the age of 26. Oppenheimer may have been acutely aware that his best work was now behind him. And this had been work that had not been judged worthy of the coveted prize.

Oppenheimer was also politically active. His privileged upbringing may have fostered in him a sense of guilt which was manifested as a heightened social conscience. This does not seem to have been directed towards particular individuals, at least outside his own family, but rather to political ideals and social causes. As he later explained:

I had had a continuing, smouldering fury about the treatment of Jews in Germany. I had relatives there, and was later to help in extricating them and bringing them to [America]. I saw what the Depression was doing to my students. Often they could get no jobs, or jobs which were wholly inadequate. And through them, I began to understand how deeply political and economic events could affect men’s lives.

From the very beginning, what Lawrence referred to as Oppenheimer’s ‘leftwandering activities’ generated suspicion and caused concern over his involvement in the American bomb programme. By his own subsequent admission, in the mid-1930s Oppenheimer had been involved with just about every Communist front organisation in California.

Motivated by his infatuation with, and on-off engagement to, Jean Tatlock, daughter of a professor of literature at Berkeley and a prominent Communist Party activist, he had become involved with fund-raising to support the fight against the growing threat of European fascism. When
his relationship with Tatlock ended, he married Katherine (Kitty) Peuning, a descendant of European royalty. Although Oppenheimer himself never became a card-carrying member of the American Communist Party, his wife Kitty, brother Frank, his close friend Haakon Chevalier and a number of his research team at Berkeley were at one time or another party members.

The FBI had opened a file on Oppenheimer in March 1941, after he was observed the previous December arriving by car for a discussion group meeting at Chevalier’s home. The targets for FBI surveillance on this occasion had been two other activists, but further surveillance connected Oppenheimer with Steve Nelson, also known by the name Steve Mesarosh, a key figure in the Communist Party apparatus in San Francisco’s Bay Area.

Croatian-born Nelson had spent two years at the International Lenin School in Moscow, where he had been taught working-class history, Marxism, and the practicalities of proletarian dictatorship. During this time, he had been sent on clandestine missions to Europe, India and China. Those looking for links between the legitimate (or, at least, tolerated) activities of the American Communist Party and the illegal activities of Soviet intelligence were looking closely at Nelson.

Nelson also knew Kitty Oppenheimer through her second husband, also a Communist, who had died fighting in Spain in 1937. The Oppenheimer and Nelson families met socially on several occasions. Robert was Kitty’s fourth husband.

Oppenheimer was a security nightmare, yet his contributions to the S-1 programme had thus far been extremely valuable. Compton was now asking that he take over responsibility for the work on fast-neutron reactions and the principles of bomb design. Lawrence had insisted that Oppenheimer cease his flirtation with radical left-wing politics, and Oppenheimer had acquiesced (though he was still making financial contributions to left-wing causes as late as April 1942). He had been granted temporary security clearance so that he could work in support of Lawrence and he had completed
a security questionnaire in April which he had answered mostly honestly.
²
However, full security clearance was not immediately forthcoming.

Oppenheimer could not afford to wait. As he began to get to grips with the nature and scale of the task that Compton had now assigned to him, he realised that he needed the best brains in the country to work on the problem. In early July 1942 he gathered together a study group at Berkeley made up of the brightest theoretical physicists he could find. He dubbed them the ‘luminaries’.

Any lead that the Tube Alloys physicists believed they possessed in the areas of fast-neutron reactions and bomb design was about to evaporate.

The luminaries

As the S-1 programme moved forward through the spring of 1942, Teller had little choice but to cool his heels. Szilard, extremely annoyed at Compton’s rather undemocratic decision to consolidate reactor research at Chicago, had nevertheless packed his bags and moved there at the end of January 1942. Wigner completed a study on chain reactions with his group at Princeton before joining the Met Lab in April, where he would work on reactor design.

Of the original Hungarian conspirators, Teller had so far been excluded from the most recent developments. He suspected issues with security clearance: ‘Although Mici and I were both [American] citizens, our families were behind enemy lines.’ But Oppenheimer wanted him on the programme, and overruled whatever security issues were causing problems with Teller’s clearance. Teller joined the Met Lab in early June.

It seemed that nobody had given any thought to what Teller should be doing, so he joined forces with a young physicist from Indiana, Emil Konopinski, who had arrived in Chicago at about the same time. Fermi had earlier suggested that the temperatures generated in an atomic explosion might be sufficient to trigger a thermal reaction between atoms of deuterium, fusing the atoms together and releasing an even more extraordinary quantity of energy in the process. The sun is powered by fusion reactions of this kind.

In this case the trigger was simply the high temperatures – about 400 million degrees Celsius – generated by an atomic explosion. A fusion reaction would not depend on acquiring a critical mass of a rare isotope or a new element unknown in nature, or self-sustaining chain reactions. Such a ‘thermonuclear’ reaction would therefore proceed as long as the temperature was maintained and there was enough deuterium fuel available to burn.

Teller and Konopinski figured they could usefully spend their time proving that this was impossible. They set to work, and discovered that for every objection they could identify, they could also find a potential workaround. They realised that a thermonuclear bomb was, in fact, possible. By the time Oppenheimer called the study group together at Berkeley, they believed they knew how such a bomb could be built.

In addition to Teller and Konopinski, Oppenheimer had also invited German émigré Hans Bethe from Cornell, John H. Van Vleck, Swiss-born Felix Bloch and Oppenheimer’s former student Robert Serber, who had returned to Berkeley from Illinois at Oppenheimer’s request. They met in a couple of attic rooms in Le Conte Hall, an administrative building on the Berkeley campus in which Oppenheimer had an office.

Until this point Bethe had refused to get involved in the programme, for the simple reason that he did not believe a bomb would work. Bethe had obtained his doctorate with Arnold Sommerfeld in Munich and had worked at Cambridge and with Fermi in Rome before taking up a position at the University of Tübingen. Although he had been raised as a Christian, his mother was Jewish and he lost his academic position in 1933. He made his way first to England, where he worked for a time with Peierls, before moving to a professorship at Cornell University in 1935.

On their way from New York to Berkeley, Bethe and his wife stopped off in Chicago to pick up the Tellers. Teller took the opportunity to show Bethe around the Met Lab, and particularly the latest experimental nuclear
reactor that Fermi and his team were assembling in a doubles squash court in the west stands of Stagg Field, part of the University of Chicago. Bethe was amazed, and realised that his reservations might be poorly founded.

At Berkeley, the study group began work on the theory of a fission bomb, starting with the MAUD Committee report and the results of the various groups that had studied the problems under both Breit and Oppenheimer. It quickly became apparent that the fission bomb was a ‘sure thing’, and Serber was left to work out the details with Eldred Nelson and Stan Frankel, postdoctoral research assistants in Oppenheimer’s group. Teller and Konopinski persuaded the rest of the group to work with them on the possibility of a thermonuclear bomb, which during the summer became known as the ‘Super’.