The recent release of new letters by Niels Bohr's estate has sparked increased interest in the mysterious 1941 meeting in Copenhagen between Bohr and German physicist Werner Heisenberg. Copenhagen, a play currently at the Schubert Theater in Chicago, deals with the uncertainties of the encounter that have puzzled scientists and historians ever since.
Peter Freund, a professor of physics at the U of C, met Heisenberg on several occasions. "I talked some physics with him, but I certainly was not close to him," Freund said.
Heisenberg, a Nobel Laureate in physics, claimed that he knew how to build the atomic bomb and had tried to sabotage its construction. After the end of World War II, Heisenberg was a detainee in England and learned about the U.S. atomic bombing of Hiroshima. According to Freund, Heisenberg then gave a lecture to the other detainees about the construction of an atomic bomb and had all the details correct.
"A few days earlier, in a conversation with Otto Hahn, who discovered nuclear fission, Heisenberg still had the critical mass wrong: tons instead of kilograms," Freund said. "There are two possible explanations of this either Heisenberg rethought the problem in the wake of Hiroshima and got it right, or he knew it all along, in which case he did sabotage the German bomb project. I doubt we will ever know the truth."
It was hoped that the Bohr letters might help solve the mystery. So far, however, the Bohr letters have not been able to answer the questions that surround the meeting. "The letters tell us how Bohr perceived Heisenberg's position and intentions at the time they met in Copenhagen," Freund said. "To what extent Bohr's perceptions have anything to do with Heisenberg's true position and intentions remains as big a mystery as ever."
There had been some concern that the letters, which Bohr wrote but never sent to Heisenberg, might undercut Copenhagen. According to Celise Kalke, the resident dramaturg at Court Theatre, this is not the case. "The letters made the point of the play no one will really know what went on at that meeting," Kalke said.
Playwright Michael Frayn wrote Copenhagen after reading Heisenberg's War by Thomas Powers, a book that concluded that Heisenberg did in fact consciously obstruct the development of the German atomic bomb project. "Frayn was inspired to look at the 1941 encounter and see if it was possible to make a play from it," Kalke said. "The interest in the play started there."
Originally, Bohr's estate had planned to release Bohr's letters in 2012, 50 years after Bohr's death. The popularity of Copenhagen caused Bohr's estate to reconsider, and on February 6, the letters were made available to the general public.
According to Kalke, there are no plans to alter the play due to the release of Bohr's letters. "The play hasn't been affected that much," Kalke said. "The play raises questions rather than answering them."
"In the end, the letters can only strengthen the play," Kalke said. "These letters help the playwright's argument, which is that we cannot control fate."
"I think the ambiguities of the play Copenhagen are at its very core," Freund said. "These ambiguities have not been resolved by the Bohr letters. If anything they have been compounded by them."