Copenhagen - Michael Frayn [48]
If the story is true it might help to explain Goudsmit’s insistence, in the teeth of the evidence from Farm Hall, that Heisenberg couldn’t tell the difference between a reactor and a bomb. It would certainly cast doubt on Heisenberg’s recollection that the entire discussion with Bohr in 1941 took place during the walk, and that Bohr broke off the conversation almost as soon as it was broached. It seems improbable to me that Heisenberg would have risked putting anything down on paper, and if even so he had then I can’t see why he didn’t seize upon it after the war, to support his claim that he had hinted to Bohr at the German research on a bomb. I suppose it’s possible that Bohr made the sketch himself, to illustrate to his colleagues at Los Alamos what he thought Heisenberg was getting at, but the truth of the matter seems to be irretrievable.
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I have had many helping hands with this play, both before it was produced in London and since. Sir John Maddox kindly read the text for me, and so did Professor Balázs L Gyorffy, Professor of Physics at Bristol University, who made a number of corrections and suggestions. I am also indebted to Finn Aaserud, the Director of the Niels Bohr Archive in Copenhagen, and to his colleagues there, for much help and encouragement. Many scientists and other specialists have written to me after seeing the play on the stage. They have mostly been extraordinarily generous and supportive, but some of them have put me right on details of the science, for which I am particularly grateful. They also pointed out two mathematical errors so egregious that the lines in question didn’t make sense from one end to the other—even to me, when I re-read them. All these points have now been addressed, though I’m sure that other mistakes will emerge. So much new material has come to hand, in one way or another, that I have extensively overhauled and extended this Postscript to coincide with the production of the play in New York.
One matter of dispute that I have not been able to resolve completely concerns the part played by Max Born in the introduction of quantum mechanics. The matter was raised (with exemplary temperance) by his son, Gustav Born, who was concerned about the injustice he felt I had done to his father’s memory. I was reluctant to make the play any more complex than it is, but I have since made adjustments both to the play itself and to this Postscript which go at any some way to meeting Professor Born’s case. We are still at odds over one line, though, in which Heisenberg is said to have’invented quantum mechanics’. I am quoting the judgment of other physicists here (including one not especially sympathetic to Heisenberg), but I realise that it is a huge over-simplification, and that it seems to compound the original injustice committed when Heisenberg was awarded the Nobel Prize in 1932 ‘for the creation of quantum mechanics’, while Born had to wait another 22 years to have his part acknowledged in the same way. The trouble is that I have not yet been able to think of another way of putting it briefly enough to work in spoken dialogue.
The American physicist Spencer Weart, in a letter to Finn Aaserud, very cogently pointed out that the calculation of the critical mass was much harder than I’ve made it seem for Heisenberg once Bohr has suggested it to him. ‘Perrin failed to get it and his publication of a ton-size critical mass subtly misled everyone else, then Bohr and Wheeler failed, Kurchatov failed, Chadwick failed, all the other Germans and Russians and French and British and Americans missed it, even the greatest of them all for such problems, Fermi, tried but missed, everyone except Peierls … Physics is hard.’
Some correspondents have also objected to Heisenberg’s line about the physicists who built the Allied bomb, ‘Did a single one of them stop to think, even for one brief moment, about what they were doing?’, on the grounds that it is unjust to Leo Szilard. It’s true that in March