Heisenberg’s message to Bohr: Who knows?

Abstract

The discussion about Copenhagen misses a very important point. Werner Heisenberg’s visit to Niels Bohr occurred during a generally forgotten half-year window of time between the German invasion of the Soviet Union and the Japanese attack on Pearl Harbor.The German blitzkrieg into the Soviet Union left an impression, certainly held by Heisenberg, that the Germans would win the war quickly and that the world would conduct business as usual with the victors who had destroyed the evil Communist empire.An objective evaluation of America in 1941 and of what has been learned about the German uranium project supports a very different version of the visit from those presented in the play. We heard this version from Niels Bohr when he came to the Weizmann Institute around 1960.Heisenberg and his colleagues had been completely surprised by the news that an atom bomb had been dropped on Hiroshima. Germany had no serious atom bomb program; the Germans never believed that it was possible. To cover their embarrassment at having missed this possibility, Heisenberg and friends invented the story that they had opposed the bomb project for moral reasons. Bohr was furious at this outright lie, and told Amos de Shalit that Heisenberg’s message in 1941 was “You know that we are going to win this war and we will be building a new high-tech Europe based on the discoveries in quantum physics and nuclear energy. Why don’t you join us?” One can imagine Bohr’s feelings about being asked to participate in the building of Adolf Hitler’s “thousand-year Reich” and Heisenberg’s insensitivity to such feelings. The possibility of an atomic bomb was probably not even discussed, being considered irrelevant at the time.Several years ago I checked the story with my friend Abraham “Bram” Pais whose description of this visit in his biography of Bohr was suspiciously vague. Bram would neither confirm nor deny my story. He said that Bohr had been very angry at Heisenberg and had written him an angry letter. Bram had seen this letter, but was not at liberty to reveal its contents because the Bohr family insisted on its being kept confidential.Most discussions of a possible German atomic bomb project overlook the role played in the US Manhattan Project by an enormous military–industrial complex that did not exist in wartime Germany. That the German project was not in that league is clearly indicated by the memoirs of Nikolaus Riehl, the industrial physicist who directed the German plant producing reactor-grade uranium, was grabbed by the Russians immediately after their entry into Berlin, and was kept for 10 years doing a similar job for the Russians. Riehl had to wait many months to obtain the copper needed to produce a transformer for his uranium production at a time when the large American industrial nuclear plant at Hanford, Washington, was processing tons of reactor-grade uranium to make the plutonium that was used in the bomb dropped on Nagasaki. The Germans did not even have the uranium to make a reactor, let alone a mammoth plant like Hanford.Perhaps historians will soon put the essentially nonexistent German bomb project in its proper place and give a more realistic picture of the Bohr–Heisenberg meeting in 1941.© 2001 American Institute of Physics.