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Regarding the WWII Meeting of Bohr & Heisenberg
HarlanC writes: "The NY Times has an article (registration required) discussing the famous meeting between Niels Bohr and Werner Heisenberg in Copenhagen in 1941. The conclusion is that Heisenberg revealed to Bohr the existance of a Nazi atomic program in an attempt to obtain assistance from Bohr. The Times of London article is here (long registration process required)" The play "Copenhagen" was based on a fictionalization of this meeting, it was much better than "Proof", I assure you.
Heisenberg's War: The Secret History of the German Bomb,
Thomas Powers provides lots of interesting detail, citations, background. From reading various sources, I see Heisenberg as badly misjudged and misrepresented. I think he was basically a good guy in a very bad situation and, integrating all the available material, it feels like he basically did the Right Thing, and played a key role in keeping the German nuclear program working in directions other than building a bomb.
-- We all have enough strength to endure the misfortunes of other people. La Rochefoucauld
Shortly after WWII, Werner Heisenberg was held captive by the British government at Farm Hall along with several other top German scientists. The British secretly taped the conversations at Farm Hall, and these tapes were declassified in 1992. (It took prolonged and strenuous efforts by several historians, and members of the Royal Society to persuade the government.) Heisenberg was at Farm Hall when the US dropped the bombs on Japan in August of 1945. When he heard the news, he was astonished that the US had separated sufficient U235 from U238 to obtain critical mass. He was also surprised that the US also made a plutonium based bomb. (The methods used to extract U238 and Pu were made by a chemist working under Enrico Fermi in Chicago. Without the knowledge provided by that chemist, the US would not have had either bomb for perhaps another year.) Since Heisenberg was surprised, we may assume he simply did not know how to get enough weapons grade uranium. Nor could he make enough and separate enough plutonium for a bomb. He had enough uranium to make a small nuclear reactor. Which he did create in a cave in southern Germany. The US army found the cave and removed the materials. The assessment by US scientists was that the reactor was never put to use. Apparently war efforts hindered Heisenberg's attempt to get all the resources he needed. And, towards the end of the war, the effort was abandoned. It is likely that Heisenberg knew he could not make a bomb and persuaded the Nazi government to allow him to make a reactor instead. Whether he had only technical reasons for the change in policy is unknown. He may have had moral reasons for preventing the Nazis from getting a bomb, but there is no public source of information to support that hypothesis. In 1941, he may have wanted to make a bomb, or knew that the Nazis wanted him to make one. In either case, I think he went to Copenhagen to ask/tell/warn Bohr about the Nazi plans. During that evening, he and Neils Bohr went for a walk. Bohr's wife, Margerethe, reported that they both left the house that evening in a good mood. The walk in the dark was short, only a few minutes. Neils Bohr came back quickly, and in a foul mood. Heisenberg followed him back inside. They did not talk about much later that evening. Later in the war, Bohr's family secretly got into a boat at night and left for England, and then America. Heisenberg stayed in England for some time, as a "guest" of the British government. In 1947, he was allowed to visit Bohr, and his British handler went with him. During that meeting, he and Bohr agreed that "we both came to feel that it would be better to stop disturbing the spirits of the past." (From Heisenberg's memoirs.) Bohr and Heisenberg continued their friendship after 1947, and until Bohr died in 1962. Bohr kept that friendship even though most Allied scientists shunned Heisenberg.