I read with interest Silvan Schweber’s review of My Dear Li: Correspondence 1937–1946 by Werner Heisenberg and Elisabeth Heisenberg, and I noted with sadness Schweber’s passing on 14 May 2017.
I knew Werner Heisenberg quite well, having worked in the Max Planck Institute for Physics under his directorship for two decades, beginning in 1950. I had the opportunity to talk with him about his work during the war. I also frequently met Elisabeth Heisenberg at various events.
Schweber captures well the feelings and thoughts Heisenberg expressed in letters to his wife from 1937 to September 1939. Schweber’s comments on the later letters, however, need some clarifications.
Working on the German atomic bomb was not Heisenberg’s decision. He was drafted in September 1939 to serve with other leading scientists in a group later known as the Uranium Club. Heisenberg was tasked with finding out whether the energy released by nuclear fission could be used for military and civilian purposes. After extensive studies he decided that applications of that type would be possible theoretically but that practical implementation of them would require a huge and lengthy industrial effort.1
As a result, Minister of Armaments Albert Speer terminated the bomb project in 1942 and concentrated all available resources on weapons production. Nevertheless, the German Army Ordnance Office continued military uranium research with its own small group, with which Heisenberg was not involved. He continued to focus on cosmic rays, S-matrix theory, and construction of a small test reactor.
It is true, as Schweber suggested, that Heisenberg identified with his beloved Germany, but he did not identify with the Nazi ideology. He did not join the Nazi Party, and he had many Jewish friends and pupils and maintained friendly relations with his Jewish colleagues. He probably felt a certain admiration for the rapid advances of the German armies in 1939–41. Like many non-Nazi Germans at the time, he did not want Hitler to win the war, but he did not want Germany to lose it.
Schweber takes exception to Heisenberg’s statement to his wife, made after his visit with Niels Bohr, that he had “his assigned part … to defend our system.” But what else could Heisenberg have done when, unavoidably, the circumstances of German occupation of Denmark came up in conversations? He had to assume that his words and actions were carefully observed by the Gestapo. He also had to expect that Bohr might unwittingly disclose what he had said. Any remark showing opposition to or even dissatisfaction with the Nazi system might have had severe consequences.
Heisenberg also had to face the question of whether to leave Germany in 1933 after the Nazis took over. Lise Meitner didn’t leave until 1938, when her Austrian passport no longer protected her from Nazi persecution; she later said she had “committed a great moral wrong” by not leaving earlier. Schweber believed that the same was true of Heisenberg. Indeed, Heisenberg discussed leaving in 1933 or 1934 with Max Planck, president of the Kaiser Wilhelm Society for the Advancement of Sciences. Planck believed that the scientists who were not forced to leave Germany should stay and try to preserve as much as possible of the nation’s culture and former scientific excellence. He compared Nazism to a storm that causes major damage but will pass eventually. All forces would then be needed to rebuild the country, as happened after World War I.
Heisenberg hoped for a similar reconstruction after World War II. However, only he, with his international scientific reputation, attracted foreign students and collaborators. German universities as a whole had lost their pre-1933 excellence because of the expulsion of leading Jewish physicists and Hitler’s contempt for modern “Jewish” physics. The center of excellence in physics had moved to the US.