The First War of Physics (52 page)

Heisenberg’s argument, that they hadn’t tried to build a bomb because they didn’t think it could be done within the likely timeframe of the war, was too morally ambiguous for Weizsäcker. The next day, he further elaborated the
Lesart.
‘History will record that the Americans and the English made a bomb,’ he said, ‘and that at the same time the Germans, under the Hitler regime, produced a workable [reactor].
⁵
In other words, the peaceful development of the uranium [reactor] was made in Germany under the Hitler regime, whereas the Americans and the English developed this ghastly weapon of war.’

So, Weizsäcker’s argument went, the Allies had succeeded in making and using an ‘immoral’ weapon. The German physicists had not wanted to do this on moral grounds, but they could have done it if they had really wanted to.

They now became concerned that the reports of their work appearing in the press were inaccurate and, at Rittner’s suggestion, agreed to draft a memorandum to set the record straight. This memorandum, dated 8 August, explained that the Uranverein had never seriously pursued the possibility of a bomb:

At the beginning of the war a group of research workers was formed with instructions to investigate the practical application of [nuclear] energies. Towards the end of 1941 the preliminary scientific work had shown that it would be possible to use the nuclear energies for the production of heat and thereby to drive machinery. On the other hand, it did not appear feasible at the time to produce a bomb with the technical possibilities available in Germany. Therefore the subsequent work was concentrated on the problem of the [reactor] for which, apart from uranium, heavy water is necessary.

The memorandum also sought to establish Hahn’s priority as the discoverer of nuclear fission, playing down Lise Meitner’s role:

The Hahn discovery was checked in many laboratories, particularly in the United States, shortly after publication. Various research workers – Meitner and Frisch were probably the first – pointed out the enormous energies which were released by the fission of uranium. On the other hand, Meitner had left Berlin six months before the discovery and was not concerned herself in the discovery.

No reason was given for Meitner’s departure from Berlin. And Hahn had conveniently forgotten the letters he had exchanged with his much-missed associate.

The memorandum was signed by all ten physicists, though Heisenberg had had to lean on Bagge, Diebner, Korsching, Weizsäcker and Wirtz to get them to sign. Laue signed to endorse the accuracy of the statement, but emphasised that he had played no part in the work described.

A confused explanation

In the days that followed, Heisenberg set about the task of working out how the Allies had done it. He gave a seminar to the group on 14 August. This seminar reveals quite starkly the level of ignorance among the German physicists concerning even some of the most basic principles of atom bomb physics.

By this time Heisenberg had stopped using the approach which had earlier led him to conclude that tons of U-235 would be required, but he was still far from working out a critical mass based on a fast-neutron chain reaction in the way that Frisch and Peierls had done. Whatever methodology had been used to conclude that between ten and 100 kilos of fissile material would be required appeared to have been forgotten. But, although Heisenberg was now at least heading in the right direction, in his seminar he was still unable to distinguish clearly between the physics of a bomb and the physics of a reactor.

In fact, this lack of distinction dogged the seminar right from the beginning, which Heisenberg opened by saying: ‘I should like to consider the U-235 bomb following the methods we have always used for our uranium machine.’ He goes on to say: ‘It then turns out in fact that we can understand all the details of this bomb very well.’ In very general terms, Heisenberg was able to fathom some of the principles of the Little Boy uranium bomb, but by the end of the seminar there appears in fact to have been very little real understanding. The remarks made by Heisenberg’s colleagues only added to the confusion.

As he had sat facing Heisenberg across the table in Heidelberg, Goudsmit had found it all rather sad and ironic. In the early stages of the war the Allied physicists had held their German colleagues in high esteem and feared for what such combined talent could deliver to Hitler’s arsenal. Bohr had come away from his meeting with Heisenberg in Copenhagen in September 1941 with the clear impression that everything was being done in Germany to develop atomic weapons. That fear had led, eventually, to Tube Alloys and the Manhattan Project. And, ultimately, to Hiroshima and Nagasaki.

The stark reality was that the German physicists had made relatively little progress. The programme had never been escalated beyond a somewhat loose association of individual academic research projects, within which the physicists would occasionally squabble over scarce resources. Although they had carried out some limited research and indulged in some speculation, from mid-1942 the physicists at least in Heisenberg’s circle had never really attempted to build a bomb.

However, they
had
attempted to build a working reactor. They had failed, in part because the Allies were relentless in denying them access to sufficient quantities of heavy water for their experiments. But they had also failed in part because they had not been able to work together effectively. While detained in Huy, Heisenberg had argued that the physicists had now been afforded an opportunity to collaborate and pool their information, advancing their work beyond what the Alsos mission had uncovered from the documents that had been confiscated. It was a remarkable admission. Useful collaboration between the disparate groups within the Uranverein had happened only because they had been captured and interned by the Allies.

Then there was the role that Heisenberg himself had played. Bagge and Diebner acknowledged Heisenberg’s influence as they speculated on what would now happen to them after the announcement on 6 August.

‘They won’t let us go back to Germany’, Diebner said. ‘Otherwise the Russians will take us. It is quite obvious what [the Americans] have done, they have just got some system other than ours. If a man like Gerlach had been there earlier, things would have been different.’

Bagge was not so sure. ‘Gerlach is not responsible,’ he said, ‘he took the thing over too late. On the other hand it is quite obvious that Heisenberg was not the right man for it … Heisenberg could not convince anyone that the whole thing depended on the separation of isotopes. The whole separation of isotopes was looked on as a secondary thing. When I think of my own apparatus – it was done against Heisenberg’s wishes.’

Although he had never led the programme, deference to Heisenberg’s authority as Germany’s leading theoretical physicist meant that he remained highly influential throughout the programme and was rarely challenged on his views. He had stubbornly persisted with inferior reactor configurations ‘for the sake of method’. This, combined with his tendency to favour a rather loose approach to problem-solving, his unwillingness to let go of what he perceived to be an elegant theoretical solution, animosity towards Diebner and his experimental approach, and a general lack of experimental or engineering experience, were all ultimately telling.
⁶

It seems that, at least in his own mind, Heisenberg had throughout the war maintained his commitment to the ideal of the ‘apolitical’ scientist, rising above the day-to-day political concerns of ordinary German citizens. In this way he believed he had remained uncontaminated by Nazi ideology. Whether by design or default, this attitude would allow him subsequently to distance himself from the brutal acts that had been perpetrated in the name of that ideology, acts that were now being exposed to a disbelieving world.

This aloofness was transmitted through to his work for the Uranverein. He had remained above it all, largely ambivalent to the work on nuclear problems
⁷
and, in the latter stages of the war, happy to exploit the advantages of the nuclear programme as a means for self-preservation, for himself and for his colleagues. In truth, in the final years of the war Heisenberg had focused more of his attention on his academic research on cosmic rays and on his foreign lecture tours, as an ambassador for German culture.

It was this latter activity that had betrayed him. To his former colleagues in Nazi-occupied Europe, Heisenberg was perceived to be a very willing representative of an oppressive, hateful, evil regime. He was seen as fully engaged in that regime’s strategy of cultural imperialism. His own brand of nationalism, which was no doubt in his own mind very distinct from Nazi ideology, was not so readily distinguished by those he encountered living under the Nazi yoke. He might have thought he had maintained an apolitical stance, but his colleagues saw otherwise.

And this was what Heisenberg had ultimately failed to appreciate. In the end it did not matter what Heisenberg
thought.
What really mattered was what he
did.

The German programme was never escalated to an industrial scale because the physicists believed the bomb to be out of reach. They had not produced a bomb because they believed it to be technically unfeasible,
not
because it was an immoral weapon that should not be made. It was, as Heisenberg himself acknowledged, a
lack
of courage that had prevented the physicists from sticking their necks out and asking for funding for an industrial-scale effort when they were presented with an opportunity to do just this on 4 June 1942.

Nobel prize song

Groves received copies of Rittner’s reports from Farm Hall and read them with great interest, often making notes in the margins. In truth, there was little to be learned except the reasons for the German physicists’ failure. The recorded conversations yielded some insights into the physicists’ thinking, their attitudes and their aspirations for the future, but there were no further secrets to be revealed.

As their captivity at Farm Hall continued into the winter of 1945, the German physicists became increasingly restive. Delays in reaching a decision on their fate and the perceived intransigence of the British authorities sometimes led to heated exchanges between the physicists and their
captors. They threatened to break the terms of their parole, and drafted letters calling for an immediate release and an opportunity to return to Germany so that they could pursue their scientific work.

There was one piece of news that served to lighten the gloom, however. On 16 November the
Daily Telegraph
reported that the 1944 Nobel prize for chemistry had been awarded to Hahn, for his discovery of nuclear fission. The Swedish Academy had no idea where Hahn was.

Although the physicists were initially doubtful that the announcement was genuine, Rittner promised to try to verify the report via London. The physicists nevertheless celebrated in style. Laue made an emotional speech which he ended thus:

But my speech would be grossly incomplete if I did not also come to mention yet another person: your wife. She must have received the news also; what conflicting feelings must be assailing her this evening! But I hope, indeed, that joy will finally predominate with her, the proud joy to be the wife of such a man. Gentlemen! We lift our glasses and drink to the health of Otto and Edith Hahn. Three cheers for them.

Both Laue and Hahn were in tears.

Aside from speeches, the celebrations also included the hastily-written ‘Farmhaller Nobel-prize song’, sung by Diebner and Wirtz, which opened as follows:
⁸

Detained since more than half a year

Sind Hahn und wir in Farm Hall hier.

Und fragt man wer is Shuld daran

So ist die Antwort: Otto Hahn.

For her part, Lise Meitner had fallen victim to selective memory and the jealousy of a scientific rival. She undoubtedly deserved either a share of the chemistry prize with Hahn or award of the physics prize. She received neither. In their 8 August memorandum the German physicists at Farm Hall had already forged another
Lesart.
that nuclear fission had been discovered by a German chemist without the help of physics or of Meitner. The Germans needed a new hero. It was to be Hahn, and Hahn alone.
⁹

At the same time, Manne Siegbahn had blocked the award of the 1945 physics prize to Meitner. It had gone instead to Wolfgang Pauli. From being hideously lauded in the press as the ‘Jewish mother of the bomb’, Meitner was now relegated to a footnote in history as Hahn’s
Mitarbeiter
, or subordinate.

On 3 January 1946 the German physicists were flown to Lübeck and then transported by bus to Alswede, in the British zone of occupation in northern Germany. There they were released, but forbidden from travelling outside the British zone. Exactly six months had elapsed since their arrival at Farm Hall.

Their months of comfortable detention made the shock of a ruined Germany all the more palpable. Laue wrote to his son in Princeton that: ‘The complete suffering of war makes itself felt only now.’ Heisenberg had learned of the death of his mother while at Farm Hall, and he now made an emotional journey to her graveside.

The physicists eventually went their separate ways. Diebner and Harteck went to Hamburg, Gerlach went first to Bonn, then to Munich. Hahn and Heisenberg moved to Göttingen, where Max Planck had sought refuge at the end of the war and which had been designated by the British occupiers as a centre for revival of the fortunes of German science. They were soon joined by Bagge, Korsching, Laue, Weizsäcker and Wirtz. The physicists slowly began to pick up the pieces of their lives, and their science, though they were forbidden from working on nuclear physics.

The first war of physics was finally over.