February 10, 2002
Still a Mystery: Nazi Germany's Atomic Bomb Failure
By PHILIP M. BOFFEY
A SMALL trove of documents released last week throws cold water on the notion that high-minded German scientists tried to slow work on an atomic bomb for the Nazi regime during World War II. But the documents provide no definitive answer to the question of why German physicists, who were among the best in the world, made so little progress on an atomic weapon compared with their counterparts in the United States.
The idea that German scientists worried about the morality of atomic war and tried to head off the development of a bomb was given wide currency in "Copenhagen," Michael Frayn's award-winning play, which focuses on a pivotal meeting in September 1941 between Werner Heisenberg, the scientific head of the German nuclear project, and Niels Bohr, his Danish mentor. Both were Nobel laureates and towering figures in 20th-century physics.
The play is built around the differing recollections of the two men and the ultimate uncertainty of exactly what happened. In it, the Heisenberg character explains that he visited Bohr to warn him, in highly guarded language, that atomic bombs could be built and to feel him out on whether physicists on both sides could agree to stop the work. The Frayn play was greatly influenced by a book that argued that Heisenberg and his colleagues actually sabotaged the German bomb program from within, a view that is accepted by few historians who have looked into the question.
The puzzle as to why the German atomic bomb program stalled has several overlapping explanations. Some of the best German physicists were Jewish and had been driven into exile, where many worked on the American or British atomic bomb programs. Nazi ideology had only scorn for "Jewish physics" and thus undervalued what theoretical physicists could contribute to the war effort. And as saturation bombing ravaged German cities, the Nazi industrial machine increasingly lacked the ability to mount a vast bomb development project to compete with the American Manhattan Project.
Still, it is clear that German physicists, for whatever reason, did fail to push hard enough to reach the goal. Some attribute that to surprising technical errors, like a grotesque overestimate of the amount of fissile material that was needed and a failure to realize that readily available graphite, if highly purified, could be used to moderate the atomic reaction instead of scarce, hard-to-get heavy water. Others blame arrogance and complacency on the part of German physicists who felt that if the job was hard for them, it would be impossible for the Allies. And some believe that there was a genuine reluctance to work on such an awesome weapon, either for moral reasons or for fear of failing and being blamed for a national defeat.
Recordings made surreptitiously of Heisenberg and other German scientists held in captivity after the German surrender show that they were stunned by news that the United States had exploded an atomic bomb over Hiroshima and refused to believe that it had actually been done. Even in these early recordings, one can discern the beginnings of a search for the moral high ground, as one German physicist contrasts the American development of "this ghastly weapon of war" with more peaceful nuclear reactor research under Hitler.
Heisenberg's own version of his meeting with Bohr was set out years after the war in a letter that was excerpted in a book on the atomic bomb projects. He recalled starting his conversation with Bohr by raising a question about whether it was "right" for physicists to work on uranium during the war, given that it could lead to "grave consequences." He also said he had told Bohr that developing atomic weapons would require such a terrific technical effort that one could hope they would not be ready in time. He felt the situation gave physicists leverage to dissuade government officials from even trying to build the bomb.
That letter so angered Bohr that he drafted a number of responses between 1957 and 1962 that were never sent but were released last week by the Bohr family. As Bohr recalled it, Heisenberg left "the firm impression that, under your leadership, everything was being done in Germany to develop atomic weapons." Bohr said that Heisenberg "gave no hint about efforts on the part of German scientists to prevent such a development."
Even with these latest documents, we are still left with conflicting versions from the two participants. Most historians seem inclined to accept Bohr's version as more probable and Heisenberg's as revisionist history, a view that gains credence by looking at Heisenberg in a broader context than just that single meeting.
David Cassidy, a historian at Hofstra University who wrote a biography of Heisenberg, says there is no evidence from any other sources that moral issues were of particular concern to Heisenberg. Indeed, he says, Heisenberg seemed most concerned about using the war to prove the worth of physics to the nation and its rulers. With those motivations in mind, it seems likely that Heisenberg would have made a bomb if he could.
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