Why did Werner Heisenberg visit Niels Bohr in Copenhagen in 1941? This three-hander play, first performed at the National Theatre in London, England in 1981, explores this meeting.
It was, of course, the height of the Second World War and both Nazi Germany and the Allies were trying to develop the Atom bomb. Heisenberg was working on nuclear fission in Germany, Bohr, with a mixed Jewish ancestry, was living in Denmark under Nazi occupation (he escaped to Sweden later in the war). Did Heisenberg ask Bohr whether it would be morally wrong for a physicist to create a bomb? When, later, he asked Speer for money to pursue his research he, possibly deliberately, asked for less than he would need.
The meeting was complicated by the fact that Bohr, one of the father's of the quantum atom, had been Heisenberg's mentor in the 1920s when quantum physics was experiencing revolutionary new ideas almost monthly. This was the period when Heisenberg, seeking solitude on a rocky island in Heligoland, invented the matrix-maths solution to quantum mechanics which would later be superseded by Schrodinger's wave mechanics. It was also when Heisenberg announced his Uncertainty Principle and when they together created the Copenhagen Interpretation of quantum mechanics.
The play mostly explores the relationships between the two men, and Bohr's wife Margarethe. Inevitably it involves some quantum physics. I used to teach Physics and I have always struggled to understand quantum mechanics (as did most of the scientists of the time, one of the reasons why the Copenhagen Interpretation was needed to explain what the mathematics and experiments 'meant'). So this play was always going to be difficult. There were times when it managed slightly over-simplified but nevertheless very clear explanations and there were times, for example when mentioning Complementarity, when it seemed to duck the issue entirely.
Here is my understanding of Complementarity. Heisenberg's Uncertainty Principle (better called his Indeterminacy Principle) is a mathematically proved conclusion that some system's (for example an electron) have paired properties (for an electron, its position is paired with its momentum) which are linked in that the more precisely you measure one of these properties the less precisely you are able to measure the other. In the play, Heisenberg explains it thus: “You can never know everything about the whereabouts of a particle, or anything else ... because we can't observe it without introducing some new element into the situation, an atom of water vapour for it to hit, or a piece of light - things which have an energy of their own, and which therefore have an effect on what they hit.” (Heisenberg, Act 2) But the principle is more fundamental, it isn't simply an experimental error that could somehow be circumvented but a property of nature. Nevertheless, the Uncertainty Principle is one aspect of Complementarity. Another is the fact that an electron can behave both as a wave or as a particle ('wave-particle duality') and which behaviour it adopts appears to be determined by the way it is being observed. Thus Complementarity seems to be the idea that there are two versions of truth and both are true although neither can be true at the same time.
Selected quotes:
- “If you don't know how things are today you certainly can't know how they're going to be tomorrow.” (Heisenberg, Act 2)
- “If it's Heisenberg at the centre of the universe, then the one bit of the universe that he can't see is Heisenberg.” (Margarethe, Act 2)
- “If you are doing something you have to concentrate on you can't also be thinking about doing it, and if you’re thinking about doing it then you can't actually be doing it.” (Margarethe, Act 2)
March 2025; 96 pages
Published by Methuen Drama in 1998
