Martin Heisenberg, one of Heisenberg’s sons and a leading neurobiologist, says that we should judge his father by the political outcome. The newly published Bohr letters started another round of historical debate. But apparently, Bohr could not distinguish between propaganda and hidden messages: if there were any, they were too well hidden. At the same time, this boasting could be used as a protective shield for his true intentions, at least if we believe Heisenberg. But there could be other, all too human motives as well: a former student, in this case Heisenberg, enjoys boasting in front of his former teacher. In Copenhagen, Bohr found himself in a dangerous position: mistrusted and spied upon. Only three months prior to the Copenhagen meeting, the German Wehrmacht had even invaded the powerful Soviet Union – Hitler’s forces seemed unstoppable. How can we try to make sense of this contradiction today?įirst, we cannot ignore the time and circumstances: Denmark had been occupied by German forces for 18 months, the Netherlands, Belgium and France had been occupied for about the same time. Understandably, this shocked and frightened Bohr. In these letters, Bohr tells a different story: during Heisenberg’s entire visit, he had felt that the younger man was boasting not only about Germany’s upcoming victory, but also about his ability to build an atomic bomb in the near future. As a reaction to this new debate, Bohr’s family published several unsent letters from Bohr to Heisenberg in 2002. This play triggered another round of academic debates on the mysterious meeting in 1941. This mysterious conversation inspired the British playwright Michael Frayn to his play “ Copenhagen”, that was first performed in 1998 in London an premiered on Boradway two years later. In Michael Frayn’s play “Copenhagen”, Margarethe is one of the three main characters. Niels Bohr and his fiancee Margarethe Nørlund in 1910. So if there was indeed a subtle suggestion on Heisenberg’s part that both sides should stop pursuing the development of atomic bombs, then Bohr didn’t understand it. Heisenberg himself concedes that he “tried to keep the conversation at a level of allusions that would not immediately endanger my life” – he would have been accused of high treason at home, had the true content of this conversation become known. According to Heisenberg, Bohr had first been quiet when he talked to him, later he was aghast and left the meeting hurriedly. Niels Bohr has always contradicted Heisenberg’s version of their meeting. He suggests that they should argue with technical and fincancial difficulties – and that an atomic bomb would be an impossible endeavour in the immediate future. In this letter, Heisenberg explains how he wanted to convince nuclear scientists on both warring sides to stall the development of an atomic bomb. Jungk had interviewed leading physicists about their role in the world war, parts of Heisenberg’s letter were published in Jungk’s book “Brighter than a Thousand Suns: A Personal History of the Atomic Scientists”.

For many years, a letter from Heisenberg to the author Robert Jungk ten years later was considered the best source. Department of Energyīut what have these two giants of physics discussed in the Copenhagen park? Historians still have heated debates on this subject 75 years later, because this discussion was not recorded in writing. Werner Heisenberg (left) with Niels Bohr at a Conference in Copenhagen in 1934. Every sentence with political implications, or every secret revealed, could not only harm Bohr but would also be reported back to Berlin and could seriously affect Heisenberg. On this fine September day, they went outside to make spying on their conversation more difficult – Niels Bohr knows that he is spied on, the Nazi authorities mistrust his political attitudes as much as his background, his mother came from a Jewish family. Fifteen years earlier, both had formulated the basics of quantum mechanics together. But now they find themselves on opposing sides: Werner Heisenberg is a leading scientist of Germany’s Uranium project, and Niels Bohr, his fatherly friend and mentor, is facing many difficulties in a Denmark that is occupied by German forces. Both are renowned physicists and Nobel Laureates, and they have also been close friends for many years.

Two men stroll through a park in Copenhagen in September 1941.

Werner heisenberg atomic theory