Bohr We heard, yes. I’m so sorry.
Heisenberg These things happen. The question is now resolved. Happily resolved. We should all have met in Zürich …
Bohr In September 1939.
Heisenberg And of course, sadly …
Bohr Sadly for us as well.
Margrethe A lot more sadly still for many people.
Heisenberg Yes. Indeed.
Bohr Well, there it is.
Heisenberg What can I say?
Margrethe What can any of us say, in the present circumstances?
Heisenberg No. And your sons?
Margrethe Are well, thank you. Elisabeth? The children?
Heisenberg Very well. They send their love, of course.
Margrethe They so much wanted to see each other, in spite of everything! But now the moment has come they’re so busy avoiding each other’s eye that they can scarcely see each other at all.
Heisenberg I wonder if you realise how much it means to me to be back here in Copenhagen. In this house. I have become rather isolated in these last few years.
Bohr I can imagine.
Margrethe Me he scarcely notices. I watch him discreetly from behind my expression of polite interest as he struggles on.
Heisenberg Have things here been difficult?
Bohr Difficult?
Margrethe Of course. He has to ask. He has to get it out of the way.
Bohr Difficult What can I say? We’ve not so far been treated to the gross abuses that have occurred elsewhere. The race laws have not been enforced.
Margrethe Yet.
Bohr A few months ago they started deporting Communists and other anti-German elements.
Heisenberg But you personally …?
Bohr Have been left strictly alone.
Heisenberg I’ve been anxious about you.
Bohr Kind of you. No call for sleepless nights in Leipzig so far, though.
Margrethe Another silence. He’s done his duty. Now he can begin to steer the conversation round to pleasanter subjects.
Heisenberg Are you still sailing?
Bohr Sailing?
Margrethe Not a good start.
Bohr No, no sailing.
Heisenberg The Sound is …?
Bohr Mined.
Heisenberg Of course.
Margrethe I assume he won’t ask if Niels has been skiing.
Heisenberg You’ve managed to get some skiing?
Bohr Skiing? In Denmark?
Heisenberg In Norway. You used to go to Norway.
Bohr I did, yes.
Heisenberg But since Norway is also … well …
Bohr Also occupied? Yes, that might make it easier. In fact I suppose we could now holiday almost anywhere in Europe.
Heisenberg I’m sorry. I hadn’t thought of it quite in those terms.
Bohr Perhaps I’m being a little oversensitive.
Heisenberg Of course not. I should have thought.
Margrethe He must almost be starting to wish he was back in the Prinz-Albrecht-Strasse.
Heisenberg I don’t suppose you feel you could ever come to Germany …
Margrethe The boy’s an idiot.
Bohr My dear Heisenberg, it would be an easy mistake to make, to think that the citizens of a small nation, of a small nation overrun, wantonly and cruelly overrun, by its more powerful neighbour, don’t have exactly the same feelings of national pride as their conquerors, exactly the same love of their country.
Margrethe Niels, we agreed.
Bohr To talk about physics, yes.
Margrethe Not about politics.
Bohr I’m sorry.
Heisenberg No, no—I was simply going to say that I still have my old ski-hut at Bayrischzell. So if by any chance … at any time … for any reason …
Bohr Perhaps Margrethe would be kind enough to sew a yellow star on my ski-jacket.
Heisenberg Yes. Yes. Stupid of me.
Margrethe Silence again. Those first brief sparks have disappeared, and the ashes have become very cold indeed. So now of course I’m starting to feel almost sorry for him. Sitting here all on his own in the midst of people who hate him, all on his own against the two of us. He looks younger again, like the boy who first came here in 1924. Younger than Christian would have been now. Shy and arrogant and anxious to be loved. Homesick and pleased to be away from home at last. And, yes, it’s sad, because Niels loved him, he was a father to him.
Heisenberg So … what are you working on?
Margrethe And all he can do is press forward.
Bohr Fission, mostly.
Heisenberg I saw a couple of papers in the Physical Review. The velocity-range relations of fission fragments …?
Bohr And something about the interactions of nuclei with deuterons. And you?
Heisenberg Various things.
Margrethe Fission?
Heisenberg I sometimes feel very envious of your cyclotron.
Margrethe Why? Are you working on fission yourself?
Heisenberg There are over thirty in the United States. Whereas in the whole of Germany … Well .… You still get to your country place, at any rate?
Bohr We still go to Tisvilde, yes.
Margrethe In the whole of Germany, you were going to say …
Bohr … there is not one single cyclotron.
Heisenberg So beautiful at this time of year. Tisvilde.
Bohr You haven’t come to borrow the cyclotron, have you? That’s not why you’ve come to Copenhagen?
Heisenberg That’s not why I’ve come to Copenhagen.
Bohr I’m sorry. We mustn’t jump to conclusions.
Heisenberg No, we must none of us jump to conclusions of any sort.
Margrethe We must wait patiently to be told.
Heisenberg It’s not always easy to explain things to the world at large.
Bohr I realise that we must always be conscious of the wider audience our words may have. But the lack of cyclotrons in Germany is surely not a military secret.
Heisenberg I’ve no idea what’s a secret and what isn’t.
Bohr No secret, either, about why there aren’t any. You can’t say it but I can. It’s because the Nazis have systematically undermined theoretical physics. Why? Because so many people working in the field were Jews. And why were so many of them Jews? Because theoretical physics, the sort of physics done by Einstein, by Schrödinger and Pauli, by Born and Sommerfeld, by you and me, was always regarded in Germany as inferior to experimental physics, and the theoretical chairs and lectureships were the only ones that Jews could get.
Margrethe Physics, yes? Physics.
Bohr This is physics.
Margrethe It’s also politics.
Heisenberg The two are sometimes painfully difficult to keep apart.
Bohr So, you saw those two papers. I haven’t seen anything by you recently.
Heisenberg No.
Bohr Not like you. Too much teaching?
Heisenberg I’m not teaching. Not at the moment.
Bohr My dear Heisenberg—they haven’t pushed you out of your chair at Leipzig? That’s not what you’ve come to tell us?
Heisenberg No, I’m still at Leipzig. For part of each week.
Bohr And for the rest of the week?
Heisenberg Elsewhere. The problem is more work, not less.
Bohr I see. Do I?
Heisenberg Are you in touch with any of our friends in England? Born? Chadwick?
Bohr Hebenberg, we’re under German occupation. Germany’s at war with Britain.
Heisenberg I thought you might still have contacts of some sort. Or people in America? We’re not at war with America.
Margrethe Yet.
Heisenberg You’ve heard nothing from Pauli, in Princeton? Goudsmit? Fermi?
Bohr What do you want to know?
Heisenberg I was simply curious … I was thinking about Robert Oppenheimer the other day. I had a great set-to with him in Chicago in 1939.
Bohr About mesons.
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p; Heisenberg Is he still working on mesons?
Bohr I’m quite out of touch.
Margrethe The only foreign visitor we’ve had was from Germany. Your friend Weizsäcker was here in March.
Heisenberg My friend? Your friend, too. I hope. You know he’s come back to Copenhagen with me? He’s very much hoping to see you again.
Margrethe When he came here in March he brought the head of the German Cultural Institute with him.
Heisenberg I’m sorry about that. He did it with the best of intentions. He may not have explained to you that the Institute is run by the Cultural Division of the Foreign Office. We have good friends in the foreign service. Particularly at the Embassy here.
Bohr Of course. I knew his father when he was Ambassador in Copenhagen in the twenties.
Heisenberg It hasn’t changed so much since then, you know, the German foreign service.
Bohr It’s a department of the Nazi government.
Heisenberg Germany is more complex than it may perhaps appear from the outside. The different organs of state have quite different traditions, in spite of all attempts at reform. Particularly the foreign service. Our people in the Embassy here are quite old-fashioned in the way they use their influence. They would certainly be trying to see that distinguished local citizens were able to work undisturbed.
Bohr Are you telling me that I’m being protected by your friends in the Embassy?
Heisenberg What I’m saying, in case Weizsäcker failed to make it clear, is that you would find congenial company there. I know people would be very honoured if you felt able to accept an occasional invitation.
Bohr To cocktail parties at the Germany Embassy? To coffee and cakes with the Nazi plenipotentiary?
Heisenberg To lectures, perhaps. To discussion groups. Social contacts of any sort could be helpful.
Bohr I’m sure they could.
Heisenberg Essential, perhaps, in certain circumstances.
Bohr In what circumstances?
Heisenberg I think we both know.
Bohr Because I’m half-Jewish?
Heisenberg We all at one time or another may need the help of our friends.
Bohr Is this why you’ve come to Copenhagen? To invite me to watch the deportation of my fellow-Danes from a grandstand seat in the windows of the German Embassy?
Heisenberg Bohr, please! Please! What else can I do? How else can I help? It’s an impossibly difficult situation for you, I understand that. It’s also an impossibly difficult one for me.
Bohr Yes. I’m sorry. I’m sure you also have the best of intentions.
Heisenberg Forget what I said. Unless …
Bohr Unless I need to remember it.
Heisenberg In any case it’s not why I’ve come.
Margrethe Perhaps you should simply say what it is you want to say.
Heisenberg What you and I often used to do in the old days was to take an evening stroll.
Bohr Often. Yes. In the old days.
Heisenberg You don’t feel like a stroll this evening, for old times’ sake?
Bohr A little chilly tonight, perhaps, for strolling.
Heisenberg This is so difficult. You remember where we first met?
Bohr Of course. At Göttingen in 1922.
Heisenberg At a lecture festival held in your honour.
Bohr It was a high honour. I was very conscious of it.
Heisenberg You were being honoured for two reasons. Firstly because you were a great physicist …
Bohr Yes, yes.
Heisenberg … and secondly because you were one of the very few people in Europe who were prepared to have dealings with Germany. The war had been over for four years, and we were still lepers. You held out your hand to us. You’ve always inspired love, you know that. Wherever you’ve been, wherever you’ve worked. Here in Denmark. In England, in America. But in Germany we worshipped you. Because you held out your hand to us.
Bohr Germany’s changed.
Heisenberg Yes. Then we were down. And you could be generous.
Margrethe And now you’re up.
Heisenberg And generosity’s harder. But you held out your hand to us then, and we took it.
Bohr Yes No! Not you. As a matter of fact. You bit it.
Heisenberg Bit it?
Bohr Bit my hand! You did! I held it out, in my most statesmanlike and reconciliatory way, and you gave it a very nasty nip.
Heisenberg I did?
Bohr The first time I ever set eyes on you. At one of those lectures I was giving in Göttingen.
Heisenberg What are you talking about?
Bohr You stood up and laid into me.
Heisenberg Oh … I offered a few comments.
Bohr Beautiful summer’s day. The scent of roses drifting in from the gardens. Rows of eminent physicists and mathematicians, all nodding approval of my benevolence and wisdom. Suddenly, up jumps a cheeky young pup and tells me that my mathematics are wrong.
Heisenberg They were wrong.
Bohr How old were you?
Heisenberg Twenty.
Bohr Two years younger than the century.
Heisenberg Not quite.
Bohr December 5th, yes?
Heisenberg 1.93 years younger than the century.
Bohr To be precise.
Heisenberg No—to two places of decimals. To be precise, 1.928 …7 …6 …7 …1 …
Bohr I can always keep track of you, all the same. And the century.
Margrethe And Niels has suddenly decided to love him again, in spite of everything. Why? What happened? Was it the recollection of that summer’s day in Göttingen? Or everything? Or nothing at all? Whatever it was, by the time we’ve sat down to dinner the cold ashes have started into flame once again.
Bohr You were always so combative! It was the same when we played table-tennis at Tisvilde. You looked as if you were trying to kill me.
Heisenberg I wanted to win. Of course I wanted to win. You wanted to win.
Bohr I wanted an agreeable game of table-tennis.
Heisenberg You couldn’t see the expression on your face.
Bohr I could see the expression on yours.
Heisenberg What about those games of poker in the ski-hut at Bayrischzell, then? You once cleaned us all out! You remember that? With a non-existent straight! We’re all mathematicians—we’re all counting the cards—we’re 90 per cent certain he hasn’t got anything. But on he goes, raising us, raising us. This insane confidence. Until our faith in mathematical probability begins to waver, and one by one we all throw in.
Bohr I thought I had a straight! I misread the cards! I bluffed myself!
Margrethe Poor Niels.
Heisenberg Poor Niels? He won! He bankrupted us! You were insanely competitive! He got us all playing poker once with imaginary cards!
Bohr You played chess with Weizsäcker on an imaginary board!
Margrethe Who won?
Bohr Need you ask? At Bayrischzell we’d ski down from the hut to get provisions, and he’d make even that into some kind of race! You remember? When we were there with Weizsäcker and someone? You got out a stop-watch.
Heisenberg It took poor Weizsäcker eighteen minutes.
Bohr You were down there in ten, of course.
Heisenberg Eight.
Bohr I don’t recall how long I took.
Heisenberg Forty-five minutes.
Bohr Thank you.
Margrethe Some rather swift skiing going on here, I think.
Heisenberg Your skiing was like your science. What were you waiting for? Me and Weizsäcker to come back and suggest some slight change of emphasis?
Bohr Probably.
Heisenberg You were doing seventeen drafts of each slalom?
Margrethe And without me there to type them out.
Bohr At least I knew where I was. At the speed you were going you were up against the uncertainty relationship. If you knew where you were when you were down you didn’t know how fast you’d got there. If you knew how fast
you’d been going you didn’t know you were down.
Heisenberg I certainly didn’t stop to think about it.
Bohr Not to criticise, but that’s what might be criticised with some of your science.
Heisenberg I usually got there, all the same.
Bohr You never cared what got destroyed on the way, though. As long as the mathematics worked out you were satisfied.
Heisenberg If something works it works.
Bohr But the question is always, What does the mathematics mean, in plain language? What are the philosophical implications?
Heisenberg I always knew you’d be picking your way step by step down the slope behind me, digging all the capsized meanings and implications out of the snow.
Margrethe The faster you ski the sooner you’re across the cracks and crevasses.
Heisenberg The faster you ski the better you think.
Bohr Not to disagree, but that is most … most interesting.
Heisenberg By which you mean it’s nonsense. But it’s not nonsense. Decisions make themselves when you’re coming downhill at seventy kilometres an hour. Suddenly there’s the edge of nothingness in front of you. Swerve left? Swerve right? Or think about it and die? In your head you swerve both ways …
Margrethe Like that particle.
Heisenberg What particle?
Margrethe The one that you said goes through two different slits at the same time.
Heisenberg Oh, in our old thought-experiment. Yes. Yes!
Margrethe Or Schrödinger’s wretched cat.
Heisenberg That’s alive and dead at the same time.
Margrethe Poor beast.
Bohr My love, it was an imaginary cat.
Margrethe I know.
Bohr Locked away with an imaginary phial of cyanide.
Margrethe I know, I know.
Heisenberg So the particle’s here, the particle’s there …
Bohr The cat’s alive, the cat’s dead …
Margrethe You’ve swerved left, you’ve swerved right …
Heisenberg Until the experiment is over, this is the point, until the sealed chamber is opened, the abyss detoured; and it turns out that the particle has met itself again, the cat’s dead …
Margrethe And you’re alive.
Bohr Not so fast, Heisenberg …
Heisenberg The swerve itself was the decision.
Bohr Not so fast, not so fast!
Heisenberg Isn’t that how you shot Hendrik Casimir dead?
Bohr Hendrik Casimir?
Heisenberg When he was working here at the Institute.
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