Michael Frayn once said his work was all about how we interpret the world, which plainly exists "only through our consciousness of it."
Nowhere does he examine that idea more profoundly than in Copenhagen, a speculation about nuclear physicist Werner Heisenberg’s visit to his old mentor Niels Bohr in that city in 1941.
Exactly what was said is disputed. Heisenberg is working on the German nuclear programme, and wants to know whether the Allies are also trying to build a bomb. But why?
Espionage seems too crude an explanation. Does he want Bohr to send a message that such a project would be unviable scientifically, so that neither side will pursue it? Or does he want to ensure that if it can be done, the Germans will have the weapon first?
It becomes clear that Heisenberg has held back crucial information from his master, Albert Speer, as a result of which the latter has diverted support elsewhere in the arms development programme. But at the same time, Heisenberg and his team are working furiously on a reactor capable of achieving the necessary critical mass to produce fissile material.
So did he come to seek absolution? The play offers no moral judgement: Heisenberg did not in fact produce a bomb, Bohr did—having escaped from Nazi-controlled Denmark, he worked closely with Oppenheimer at Los Alamos. On the other hand, Heisenberg was working for Hitler, Bohr for the Allies. It is as if one needed quantum ethics as well as quantum mechanics.
There is inevitably a lot of technical detail in the play, that is fascinating even without necessarily requiring understanding, often introduced by way of anecdote.
The play shifts its time frame, sometimes looking backwards toward that 1941 meeting, re-examining the conversation and its consequences from different angles. The cast are all excellent, packaging the science in small, digestible doses, riding a wave of friendship and suspicion, co-operation and rivalry.
Philip Arditti’s Heisenberg comes across as the former brainbox at the front of the class with his hand ever raised, a boy-grown-man with few friends, socially gauche, making the wrong smalltalk, dressed to conform. And yet there seems a pathos by the end in his desire for approval.
Malcolm Sinclair plays the fatherly Bohr, perfectly capturing the conflict between loyalty to friend and to country, admiration for his star pupil and horror at what he might create.
It takes his wife Margrethe, a pitch-perfect Haydn Gwynne, to relate the scientists’ abstract world to a personal level. In this universe of approximations, in which there is no absolute measurement, she points out that the only person the observer cannot see is themselves.
Heisenberg, she says, is like one of his particles—in two positions at the same time. And the reason he has come is a simple one, not exculpation or for secret information or for the sake of humanity. But out of pride. But there are many versions of the past and it seems as good an explanation as any.
The play is directed by Emma Howlett, with a set design by Alex Eales. The first production in London in 1998 featured a large white disc on the floor, which lighting designer James Farncombe acknowledges here with a great luminous O over the stage, like the circumference of an atomic cloud or to symbolise a continuous chain reaction.
Copenhagen continues its tour to Cambridge Arts Theatre and the Rose Theatre Kingston.