Copenhagen

Margrethe
  But why?

Bohr
  You’re still thinking about it?

Margrethe
  Why did he come to Copenhagen?

Bohr
  Does it matter, my love, now we’re all three of us dead and gone?

Margrethe
  Some questions remain long after their owners have died. Lingering like ghosts. Looking for the answers they never found in life.

Bohr
  Some questions have no answers to find.

Margrethe
  Why did he come? What was he trying to tell you?

Bohr
  He did explain later.

Margrethe
  He explained over and over again. Each time he explained it became more obscure.

Bohr
  It was probably very simple, when you come right down to it: he wanted to have a talk.

Margrethe
  A talk? To the enemy? In the middle of a war?

Bohr
  Margrethe, my love, we were scarcely the enemy.

Margrethe
  It was 1941!

Bohr
  Heisenberg was one of our oldest friends.

Margrethe
  Heisenberg was German. We were Danes. We were under German occupation.

Bohr
  It put us in a difficult position, certainly.

Margrethe
  I’ve never seen you as angry with anyone as you were with Heisenberg that night.

Bohr
  Not to disagree, but I believe I remained
remarkably calm.

Margrethe
  I know when you’re angry.

Bohr
  It was as difficult for him as it was for us.

Margrethe
  So why did he do it? Now no one can be hurt, now no one can be betrayed.

Bohr
  I doubt if he ever really knew himself.

Margrethe
  And he wasn’t a friend. Not after that visit. That was the end of the famous friendship between Niels Bohr and Werner Heisenberg.

Heisenberg
  Now we’re all dead and gone, yes, and there are only two things the world remembers about me. One is the uncertainty principle, and the other is my mysterious visit to Niels Bohr in Copenhagen in 1941. Everyone understands uncertainty. Or thinks he does. No one understands my trip to Copenhagen. Time and time again I’ve explained it. To Bohr himself, and Margrethe. To interrogators and intelligence officers, to journalists and historians. The more I’ve explained, the deeper the uncertainty has become. Well, I shall be happy to make one more attempt. Now we’re all dead and gone. Now no one can be hurt, now no one can be betrayed.

Margrethe
  I never entirely liked him, you know. Perhaps I can say that to you now.

Bohr
  Yes, you did. When he was first here in the twenties? Of course you did. On the beach at Tisvilde with us and the boys? He was one of the family.

Margrethe
  Something alien about him, even then.

Bohr
  So quick and eager.

Margrethe
  Too quick. Too eager.

Bohr
  Those bright watchful eyes.

Margrethe
  Too bright. Too watchful.

Bohr
  Well, he was a very great physicist. I never
changed my mind about that.

Margrethe
  They were all good, all the people who came to Copenhagen to work with you. You had most of the great pioneers in atomic theory here at one time or another.

Bohr
  And the more I look back on it, the more I think Heisenberg was the greatest of them all.

Heisenberg
  So what was Bohr? He was the first of us all, the father of us all. Modern atomic physics began when Bohr realised that quantum theory applied to matter as well as to energy. 1913. Everything we did was based on that great insight of his.

Bohr
  When you think that he first came here to work with me in 1924 …

Heisenberg
  I’d only just finished my doctorate, and Bohr was the most famous atomic physicist in the world.

Bohr
   … and in just over a year he’d invented quantum mechanics.

Margrethe
  It came out of his work with you.

Bohr
  Mostly out of what he’d been doing with Max Born and Pascual Jordan at Göttingen. Another year or so and he’d got uncertainty.

Margrethe
  And you’d done complementarity.

Bohr
  We argued them both out together.

Heisenberg
  We did most of our best work together.

Bohr
  Heisenberg usually led the way.

Heisenberg
  Bohr made sense of it all.

Bohr
  We operated like a business.

Heisenberg
  Chairman and managing director.

Margrethe
  Father and son.

Heisenberg
  A family business.

Margrethe
  Even though we had sons of our own.

Bohr
  And we went on working together long after he ceased to be my assistant.

Heisenberg
  Long after I’d left Copenhagen in 1927 and gone back to Germany. Long after I had a chair and a family of my own.

Margrethe
  Then the Nazis came to power .…

Bohr
  And it got more and more difficult. When the war broke out—impossible. Until that day in 1941.

Margrethe
  When it finished forever.

Bohr
  Yes, why did he do it?

Heisenberg
  September, 1941. For years I had it down in my memory as October.

Margrethe
  September. The end of September.

Bohr
  A curious sort of diary memory is.

Heisenberg
  You open the pages, and all the neat headings and tidy jottings dissolve around you.

Bohr
  You step through the pages into the months and days themselves.

Margrethe
  The past becomes the present inside your head.

Heisenberg
  September, 1941, Copenhagen .… And at once—here I am, getting off the night train from Berlin with my colleague Carl von Weizsäcker. Two plain civilian suits and raincoats among all the field-grey Wehrmacht uniforms arriving with us, all the naval gold braid, all the well-tailored black of the SS. In my bag I have the text of the lecture I’m giving. In my head is another communication that has to be delivered. The lecture is on astrophysics. The text inside my head is a more difficult one.

Bohr
  We obviously can’t go to the lecture.

Margrethe
  Not if he’s giving it at the German Cultural Institute—it’s a Nazi propaganda organisation.

Bohr
  He must know what we feel about that.

Heisenberg
  Weizsäcker has been my John the Baptist, and written to warn Bohr of my arrival.

Margrethe
  He wants to see you?

Bohr
  I assume that’s why he’s come.

Heisenberg
  But how can the actual meeting with Bohr be arranged?

Margrethe
  He must have something remarkably important to say.

Heisenberg
  It has to seem natural. It has to be private.

Margrethe
  You’re not really thinking of inviting him to the house?

Bohr
  That’s obviously what he’s hoping.

Margrethe
  Niels! They’ve occupied our country!

Bohr
  He is not they.

Margrethe
  He’s one of them.

Heisenberg
  First of all there’s an official visit to Bohr’s workplace, the Institute for Theoretical Physics, with an awkward lunch in the old familiar canteen. No chance to talk to Bohr, of course. Is he even present? There’s Rozental … Petersen, I think … Christian Moller, almost certainly .… It’s like being in a dream. You can never quite focus the precise details of the scene around you. At the head of the table—is that Bohr? I turn to look, and it’s Bohr, it’s Rozental, it’s Moller, it’s whoever I appoint to be there .… A difficult occasion, though—I remember that clearly enough.

Bohr
  It was a disaster. He made a very bad impression. Occupation of Denmark unfortunate. Occupation of Poland, however, perfectly acceptable. Germany now certain to win
the war.

Heisenberg
  Our tanks are almost at Moscow. What can stop us? Well, one thing, perhaps. One thing.

Bohr
  He knows he’s being watched, of course. One must remember that. He has to be careful about what he says.

Margrethe
  Or he won’t be allowed to travel abroad again.

Bohr
  My love, the Gestapo planted microphones in his house. He told Goudsmit when he was in America. The SS brought him in for interrogation in the basement at the Prinz-Albrecht-Strasse.

Margrethe
  And then they let him go again.

Heisenberg
  I wonder if they suspect for one moment how painful it was to get permission for this trip. The humiliating appeals to the Party, the demeaning efforts to have strings pulled by our friends in the Foreign Office.

Margrethe
  How did he seem? Is he greatly changed?