*Ironically, Heisenberg refused to lend him any of his own uranium stockpile.
*Fritz Strassmann is commemorated at the Holocaust center in Jerusalem, Yad Vashem, as one of the "righteous gentiles" who came to the aid of persecuted Jews.
*Danzig is now Gdansk in Poland.
TWELVE
"HE SAID 'BOMB' IN
NO UNCERTAIN TERMS"
WINSTON CHURCHILL had given the green light to the British atom bomb project at the end of August 1941, but the scale and ambition of the Maud Committee's recommendations worried many of those involved. Building an atomic bomb could cost millions of pounds, and it seemed doubtful whether Britain, suffering sustained and heavy bombing and short of manpower, could construct the necessarily enormous plants in time to affect the outcome of the war. It needed help, and the obvious place to seek it was across the Atlantic.
News of the Maud Committee's work had reached the United States quickly, even before Churchill had given the go-ahead. A copy of the draft report was sent to Lynam Briggs as chairman of the Uranium Committee, but he proved unresponsive. In the summer of 1941 Mark Oliphant, a passionate advocate of complete Anglo-American cooperation, was sent to the United States to discover why nothing had been heard from Briggs. He was "amazed and distressed" to discover that Briggs had simply tossed the report into his safe without showing it to the other members of the committee. Perhaps Briggs thought he was being discreet, or perhaps his action—or lack of it—reflected the reality that not a single member of his committee was truly convinced that uranium fission had military potential.
Oliphant attended a meeting of the Uranium Committee to convince them otherwise. Extremely nearsighted and totally deaf in one ear, he was outwardly an unlikely emissary. However, as Samuel Allison of the University of Chicago recalled, "He said 'bomb' in no uncertain terms. He told us we must concentrate every effort on the bomb and said we had no right to work on power plants or anything but the bomb. The bomb would cost twenty-five million dollars, he said, and Britain didn't have the money or the manpower, so it was up to us." Leo Szilard was so impressed by Oliphant's passion as he toured key laboratories around the States, cajoling his fellow physicists into action, that he later joked that Congress should create a special medal to recognize "distinguished services" by "meddling foreigners."
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A few weeks earlier, in July 1941, a draft copy of the Maud Report had, however, also reached Vannevar Bush, the former dean of engineering at the Massachusetts Institute of Technology who was then the president of the Carnegie Institution. A man of vigor and vision, in June 1940 he had talked President Roosevelt into appointing him head of the new National Defense Research Committee (NDRC) and had swiftly assumed oversight of the Uranium Committee, whose torpor annoyed him. Roosevelt had subsequently appointed him director of the new Office of Scientific Research and Development (OSRD), reporting directly to the president and responsible for the NDRC. Roosevelt had thus made Bush, in effect, the United States's science chief. Even so, Bush found it hard to galvanize the Uranium Committee.
Bush's successor at the NDRC and his overall deputy was James B. Co-nant, an organic chemist and the president of Harvard. A self-confessed Anglophile, Conant was a modest man with an excellent analytical brain who, during the First World War, had worked on the army's gas warfare program. Like Bush, he was critical of the piecemeal way in which fission research was being conducted by universities and private and public institutions across the United States.
As a result of his own concerns, Bush had, in April 1941, requested the National Academy of Sciences—America's scientific elite—to appoint a committee of physicists to review uranium research. However, their two reports, focusing principally on the prospects for generating power from uranium fission, had disappointed him. The creation of violently explosive devices was, they said, a possibility, but too many uncertainties remained for them to make firm recommendations. Some National Academy physicists even thought the whole idea should be "put in wraps" until the war was over.
Ernest Lawrence disagreed. In May 1941 he pointed out that bombs could be made without the complex processes necessary to separate U-235. Unsepa-rated uranium could, he insisted, provide excellent bomb fuel. He reminded the committee of the recent success of two members of his team—Glenn Seaborg and Emilio Segre—in creating, isolating, and analyzing the new element plutonium, which fissioned almost twice as easily as U-235.
Emilio Segre (top) and Glenn Seaborg
Against this background of cautious inertia in some quarters and passionate advocacy in others, Conant and Bush privately put out feelers to Charles Darwin, the director of the British Central Scientific Office in Washington, a former researcher of Rutherford's, and grandson of the famous natural scientist. In a letter of 2 August 1941 to the British government, written by hand because of what he called the "extreme secrecy" of its contents, Darwin reported that Conant and Bush had not only raised the issue of atomic bombs but had also proposed a joint U.S.-U.K. atomic bomb program.
Darwin also revealed that he himself had raised a wider issue: Would any government ever deploy such a weapon in reality? "Are," he wrote, "our Prime Minister and the American President and the respective general staffs willing to sanction the total destruction of Berlin and the country round when, if ever, they are told it could be accomplished at a single blow?" His words echoed both those of Rudolf Peierls and Otto Frisch when they suggested to the British government that the civilian casualties resulting from an atom bomb "may make it unsuitable as a weapon for use by this country" and those of President Roosevelt, who, on the outbreak of war in 1939, had urged belligerents to refrain from "bombardment from the air of civilians or unfortified cities." However, for many on both sides of the Atlantic, a more pressing issue in 1941 was to determine whether an atomic bomb could actually be built.
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When it landed on his desk in July 1941, Vannevar Bush found the draft Maud Report compelling reading. Not only did it give a cogent summary of the underlying science, it defined a concrete program for taking the project forward that chimed with his own desire for action. By the time that, on 3 October, Conant and Bush received an official copy of the Maud Report, they had already decided to show it to the president and urge close collaboration between the United States and Britain. Mark Oliphant had traveled to Berkeley specifically to brief Ernest Lawrence and had spoken to him frankly about both the British work and the German threat. Further energized by these discussions, Lawrence had then gone out of his way to assure Bush and Conant that American experimental results confirmed the British conclusions.
To give themselves even more ammunition, Bush and Conant asked the National Academy of Sciences to carry out a fresh review to validate the British claims that an atomic bomb was feasible. On 9 October, while still awaiting the results of this review, Bush took the Maud Report to Roosevelt. He underlined the British conviction that a bomb with a destructive power equivalent to eighteen hundred tons of TNT could be made with just twenty-five pounds of active material, that the first bombs could be available by the end of 1943, but that achieving this feat, in particular building a plant to separate sufficient quantities of U-235, would require a huge and expensive industrial effort.
Impressed by Bush's advocacy, the president endorsed "complete interchange with Britain on technical matters." He also agreed that Bush could expand current fission research and assured him of sufficient funding from a special source without the need for explicit congressional approval. Anxious to ensure political control of the program and to restrict the scientists to their own sphere, Roosevelt decided to limit consideration of policy to a tiny inner circle. In addition to himself, Bush, and Conant, members were Vice President Henry Wallace; the secretary of war, the white-haired, seventy-seven-year-old Henry Stimson; and the army chief of staff, General George C. Marshall. It became known as the Top Policy Group.
Bush was well pleased with the outcome. Roosevelt had recognized the
imperative of determining the feasibility of an atomic bomb, had agreed to make the necessary resources available, and had sanctioned collaboration with the British. On 11 October 1941 the president offered Britain a partnership deal, writing to Winston Churchill, "It appears desirable that we should soon correspond or converse concerning the subject which is under study by your Maud Committee and by Dr. Bush's organization in this country in order that any extended efforts may be coordinated or even jointly conducted."
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In Germany that autumn the initiative rested with Germany's scientists rather than with their political masters. As Werner Heisenberg later told a British historian, "It was from September 1941 that we saw an open road ahead of us, leading to the atomic bomb." A month earlier, in August 1941, Manfred von Ardenne had suddenly decided to circulate Fritz Houtermans's report "On Triggering a Nuclear Chain Reaction," revealing that atom bomb fuel in the form of plutonium could be made in a reactor. Heisenberg claimed that this had induced a "panic reaction" in him. Not only had this sensitive information been widely revealed among the German scientific community, but it made Heisenberg worry whether scientists abroad had discovered the same information and were, even then, planning massive plants to manufacture plutonium. A letter to a friend revealed Heisenberg's nervous frame of mind. He wrote, "Perhaps we humans will recognize one day that we actually possess the power to destroy the earth completely, that we could very well bring upon ourselves a 'last day' or something closely related to it."
Houtermans's findings, in fact, caused few ripples in Germany, where, in the late summer of 1941 as their troops advanced ever deeper into Russia, most people were convinced of an early and victorious end to the war. However, Heisenberg later claimed, the progress of nuclear research forced him to confront certain moral issues at that time. Should he and others disengage from fission research? Alternatively, should they try to ensure that their efforts focused on nuclear power, not nuclear weapons? In his memoirs Heisenberg wrote, "We all sensed that we had ventured onto highly dangerous ground." He also recalled a conversation with Carl-Friedrich von Weizsacker, during which the two men discussed their worries. According to Heisenberg, "Von Weizsacker said something like 'At present, we don't have to worry about atom bombs, simply because the technical effort seems quite beyond our resources. But this could easily change. That being so, are we right to continue working here? And what may our friends in America be doing? Can they be heading full steam toward the atom bomb?' "
Heisenberg remembered that he tried to put himself into their position, acknowledging that refugee scientists must be firmly convinced that they were "fighting for a just cause" and that "even the good fight invariably involves some bad means." However, he suggested, "is there not a point beyond which [the scientist] cannot go under any circumstances?" "All in all," he concluded, "I think we may take it that even American physicists are not too keen on building atom bombs." But, he added, "they could, of course, be spurred on by the fear that we may be doing so."
It was then, according to Heisenberg, that von Weizsacker suggested a solution to their dilemma: " 'It might be a good thing,' Carl-Friedrich told me, 'if you could discuss the whole subject with Niels in Copenhagen. It would mean a great deal to me if Niels were, for instance, to express the view that we are wrong and that we ought to stop working with uranium.'"
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There had been no direct contact between Heisenberg, von Weizsacker, and Bohr for nearly a year after the occupation of Denmark. Then, in March 1941, von Weizsacker had been invited to Copenhagen to lecture at the newly opened German Cultural Institute—a propaganda organization to promote Germanic "values" among the conquered Danes. There he had met Cecil von Renthe-Fink, the German plenipotentiary in Denmark, a friend of von Weizsacker's high-ranking father in the German foreign office, who left the visitor in no doubt of Bohr's uncompromising attitude toward his country's occupiers. Bohr, he said, would have absolutely nothing to do with the Germans.
Nevertheless, Heisenberg sought a way to engineer a private meeting with Bohr. He later claimed that, without revealing his true purpose, he asked the German Embassy in Copenhagen to organize a visit for him, and officials arranged for him to speak at a lecture series on astrophysics at the German Cultural Institute. The series—a propaganda exercise intended to follow up von Weizsacker's March visit—had, in fact, been in gestation for some months, possibly before Houtermans's discoveries about plutonium, and Heisenberg's participation had already been discussed. It is therefore unclear which came first—Heisenberg's decision that he had to speak to Bohr or the invitation to visit occupied Denmark. What is clear from the records is that the authorities were initially wary of allowing Heisenberg out of the country. Only when the German foreign office, perhaps at von Weizsacker senior's prompting, suggested that allowing him to go to Copenhagen would be a good test of his suitability to lecture at other propaganda events in occupied Europe was permission finally given.
On 14 September 1941, accompanied by von Weizsacker, Heisenberg caught the night train to Copenhagen for a meeting that would damage a twenty-year-long friendship and spawn enduring controversy over what he actually said and why.
· · ·
Denmark's eight thousand Jews were, for the most part, still living unmolested. At this stage in the war, the Germans were treating the Danes with care, anxious not to provoke resistance on their doorstep while their forces were busily—and successfully—engaged elsewhere. Denmark was allowed a degree of automony, and Niels Bohr and his Institute for Theoretical Physics were permitted to function relatively normally. On the surface life went on. However, as one Nazi propagandist observed, "A feeling of quiet rage prevails here, which only comes to the fore when the Danes believe themselves alone and unobserved." If the Germans did observe overt dissidence, they dealt with it mercilessly. Just before Heisenberg arrived in the city, a group of Danish communists and other known opponents of the Nazis had been deported to Germany.
Despite repeated encouragement from Allied agents to escape, Bohr stayed, determined to protect his institute and the people in it. However, as he must have known, his position was precarious. His name had long been in Gestapo files, not just as a prominent scientist who was half-Jewish but because he had spoken out against Nazi ideology. At an international congress on anthropology on the eve of the war, he had denounced prejudice and argued that "different human cultures are complementary to each other." He had spoken feelingly of the "unlimited richness and variety" of human life, at which point the German delegates had walked out.
Bohr refused to attend Heisenberg's lecture. Heisenberg, however, lunched several times at Bohr's institute with Bohr's staff and, according to a postwar account by Bohr's assistant, the Polish emigre Stefan Rozental, appeared to feel little awkwardness about being in occupied Copenhagen. He "spoke with great confidence about the progress of the German offensive in Russia" and stressed "how important it was that Germany should win the war." While regretting the occupation of Western countries like Denmark and Holland, he had no doubt that German rule was "a good development" in eastern Europe "because these countries were not able to govern themselves."
Bohr was, however, clearly prepared to welcome Heisenberg privately as an old friend and as the man his sons thought of as their German uncle. But their reunion inevitably took place against "a background of extreme sorrow and tension for us here in Denmark," as Bohr later wrote. The two met and talked at the institute and may have dined together at Bohr's house, although accounts conflict. They certainly went for a walk, probably to frustrate Gestapo surveillance, and it was then that their critical discussion seems to have taken place. The risks of discovery were too great for either man to commit anything to paper at the time. Any reconstruction of the meeting therefore relies on explanations and interpretations made many years later in a world where the atom bomb had been dropped and the full scope of Nazi atrocities revealed—a world where Heisenberg was anxious to distance himself from the Naz
is, while Bohr's anxiety about the cold-war arms race may have influenced his memories.
Heisenberg's first written account of what happened was in a letter of 1948 to a Dutch friend. He recalled that he had asked Bohr whether a physicist had a moral right to work on problems in atomic physics relevant to the war. Bohr, in turn, had asked Heisenberg whether military applications of atomic power were feasible. When Heisenberg replied that they were, Bohr's apparent response was that a mobilization of physicists on both sides was unavoidable and therefore justified. Heisenberg believed that Bohr thereby dismissed his implicit suggestion that physicists of the world should band together against their governments.
Heisenberg provided a more detailed account of the meeting in a letter to the writer Robert Jungk in the 1950s. Before launching into his version of events in Copenhagen, he summarized the state of German fission research in the autumn of 1941. First, German scientists believed it was possible to build a reactor that could generate energy. Second, although they had not yet solved the problem of separating U-235, they knew that they could produce plutonium, which could, in turn, be used to fuel a bomb. However, this could only be accomplished in "huge reactors" that would have to operate for years. The production of bombs was therefore possible only with "enormous technical resources." Heisenberg believed that this requirement put scientists in a "favourable" position. Had bombs been easy to make, physicists "would have been unable to prevent their manufacture." Instead, they could play a decisive role by deciding what advice to give their governments. They had two choices: to say "that atomic bombs would probably not be available during the course of the war" or to say that "there might be a possibility of carrying out this project if enormous efforts were made." It was against this background that he had gone to Copenhagen to seek out Bohr.
Before the Fallout Page 22
