Copenhagen (4 page)

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.

Bohr
  I never shot Hendrik Casimir.

Heisenberg
  You told me you did.

Bohr
  It was George Gamow. I shot George Gamow.
You
don’t know—it was long after your time.

Heisenberg
  Bohr, you shot Hendrik Casimir.

Bohr
  Gamow, Gamow. Because he insisted that it was always quicker to act than to react. To make a decision to do something rather than respond to someone else’s doing it.

Heisenberg
  And for that you shot him?

Bohr
  It was him! He went out and bought a pair of pistols! He puts one in his pocket, I put one in mine, and we get on with the day’s work. Hours go by, and we’re arguing ferociously about—I can’t remember—our problems with the nitrogen nucleus, I expect—when suddenly Gamow reaches into his pocket …

Heisenberg
  Cap-pistols.

Bohr
  Cap-pistols, yes. Of course.

Heisenberg
  Margrethe was looking a little worried.

Margrethe
  No—a little surprised. At the turn of events.

Bohr
  Now you remember how quick he was.

Heisenberg
  Casimir?

Bohr
  Gamow.

Heisenberg
  Not as quick as me.

Bohr
  Of course not. But compared with me.

Heisenberg
  A fast neutron. However, or so you’re going to tell me …

Bohr
  However, yes, before his gun is even out of his pocket …

Heisenberg
  You’ve drafted your reply.

Margrethe
  I’ve typed it out.

Heisenberg
  You’ve checked it with Klein.

Margrethe
  I’ve retyped it.

Heisenberg
  You’ve submitted it to Pauli in Hamburg.

Margrethe
  I’ve retyped it again.

Bohr
  Before his gun is even out of his pocket, mine is in my hand.

Heisenberg
  And poor Casimir has been blasted out of existence.

Bohr
  Except that it was Gamow.

Heisenberg
  It was Casimir! He told me!

Bohr
  Yes, well, one of the two.

Heisenberg
  Both of them simultaneously alive and dead in our memories.

Bohr
  Like a pair of Schrödinger cats. Where were we?

Heisenberg
  Skiing. Or music. That’s another thing that decides everything for you. I play the piano and the way seems to open in front of me—all I have to do is follow. That’s how I had my one success with women. At a musical evening at the Bückings in Leipzig—we’ve assembled a piano trio. 1937, just when all my troubles with the … when my troubles are coming to a head. We’re playing the Beethoven G major. We finish the scherzo, and I look up from the piano to see if the others are ready to start the final presto. And in that instant I catch a glimpse of a young woman sitting at the side of the room. Just the briefest glimpse, but of course at once I’ve carried her off to Bayrischzell, we’re engaged, we’re married, etc—the usual hopeless romantic fantasies. Then off we go into the presto, and it’s terrifyingly fast—so fast there’s no time to be afraid. And suddenly everything in the world seems easy. We reach the end and I just carry on ski-ing. Get myself introduced to the young woman—see her home—and, yes, a week later I’ve carried her off to Bayrischzell—another week and we’re engaged—three months and we’re married. All on the sheer momentum of that presto!

Bohr
  You were saying you felt isolated. But you do have a companion, after all.

Heisenberg
  Music?

Bohr
  Elisabeth!

Heisenberg
  Oh. Yes. Though, what with the children,
and so on … I’ve always envied the way you and Margrethe manage to talk about everything. Your work. Your problems. Me, no doubt.

Bohr
  I was formed by nature to be a mathematically curious entity: not one but half of two.

Heisenberg
  Mathematics becomes very odd when you apply it to people. One plus one can add up to so many different sums …

Margrethe
  Silence. What’s he thinking about now? His life? Or ours?

Bohr
  So many things we think about at the same time. Our lives and our physics.

Margrethe
  All the things that come into our heads out of nowhere.

Bohr
  Our private consolations. Our private agonies.

Heisenberg
  Silence. And of course they’re thinking about their children again.

Margrethe
  The same bright things. The same dark things. Back and back they come.

Heisenberg
  Their four children living, and their two children dead.

Margrethe
  Harald. Lying alone in that ward.

Bohr
  She’s thinking about Christian and Harald.

Heisenberg
  The two lost boys. Harald …

Bohr
  All those years alone in that terrible ward.

Heisenberg
  And Christian. The firstborn. The eldest son.

Bohr
  And once again I see those same few moments that I see every day.

Heisenberg
  Those short moments on the boat, when the tiller slams over in the heavy sea, and Christian is falling.

Bohr
  If I hadn’t let him take the helm …

Heisenberg
  Those long moments in the water.

Bohr
  Those endless moments in the water.

Heisenberg
  When he’s struggling towards the lifebuoy.

Bohr
  So near to touching it.

Margrethe
  I’m at Tisvilde. I look up from my work. There’s Niels in the doorway, silently watching me. He turns his head away, and I know at once what’s happened.

Bohr
  So near, so near! So slight a thing!

Heisenberg
  Again and again the tiller slams over. Again and again …

Margrethe
  Niels turns his head away …

Bohr
  Christian reaches for the lifebuoy …

Heisenberg
  But about some things even they never speak.

Bohr
  About some things even we only think.

Margrethe
  Because there’s nothing to be said.

Bohr
  Well … perhaps we
should
be warm enough. You suggested a stroll.

Heisenberg
  In fact the weather is remarkably warm.

Bohr
  We shan’t be long.

Heisenberg
  A week at most.

Bohr
  What—our great hike through Zealand?

Heisenberg
  We went to Elsinore. I often think about what you said there.

Bohr
  You don’t mind, my love? Half-an-hour?

Heisenberg
  An hour, perhaps. No, the whole appearance of Elsinore, you said, was changed by our knowing that Hamlet had lived there. Every dark corner
there reminds us of the darkness inside the human soul …

Margrethe
  So, they’re walking again. He’s done it. And if they’re walking they’re talking. Talking in a rather different way, no doubt—I’ve typed out so much in my time about how differently particles behave when they’re unobserved … I knew Niels would never hold out if they could just get through the first few minutes. If only out of curiosity .… Now they’re started an hour will mean two, of course, perhaps three .… The first thing they ever did was to go for a walk together. At Göttingen, after that lecture. Niels immediately went to look for the presumptuous young man who’d queried his mathematics, and swept him off for a tramp in the country. Walk—talk—make his acquaintance. And when Heisenberg arrived here to work for him, off they go again, on their great tour of Zealand. A lot of this century’s physics they did in the open air. Strolling around the forest paths at Tisvilde. Going down to the beach with the children. Heisenberg holding Christian’s hand. Yes, and every evening in Copenhagen, after dinner, they’d walk round Faelled Park behind the Institute, or out along Langelinie into the harbour. Walk, and talk. Long, long before walls had ears … But this time, in 1941, their walk takes a different course. Ten minutes after they set out … they’re back! I’ve scarcely had the table cleared when there’s Niels in the doorway. I see at once how upset he is—he can’t look me in the eye.

Bohr
  Heisenberg wants to say goodbye. He’s leaving.

Margrethe
  
He
won’t look at me, either.

Heisenberg
  Thank you. A delightful evening. Almost like old times. So kind of you.

Margrethe
  You’ll have some coffee? A glass of something?

Heisenberg
  I have to get back and prepare for my lecture.

Margrethe
  But you’ll come and see us again before you leave?

Bohr
  He has a great deal to do.

Margrethe
  It’s like the worst moments of 1927 all over again, when Niels came back from Norway and first read Heisenberg’s uncertainty paper. Something they both seemed to have forgotten about earlier in the evening, though I hadn’t. Perhaps they’ve both suddenly remembered that time. Only from the look on their faces something even worse has happened.

Heisenberg
  Forgive me if I’ve done or said anything that …

Bohr
  Yes, yes.

Heisenberg
  It meant a great deal to me, being here with you both again. More perhaps than you realise.

Margrethe
  It was a pleasure for us. Our love to Elisabeth.

Bohr
  Of course.

Margrethe
  And the children.

Heisenberg
  Perhaps, when this war is over .… If we’re all spared .… Goodbye.

Margrethe
  Politics?

Bohr
  Physics. He’s not right, though. How can he be right? John Wheeler and I …

Margrethe
  A breath of air as we talk, why not?

Bohr
  A breath of air?

Margrethe
  A turn around the garden. Healthier than staying indoors, perhaps.

Bohr
  Oh. Yes.

Margrethe
  For everyone concerned.

Bohr
  Yes. Thank you .… How can he possibly be right? Wheeler and I went through the whole thing in 1939.

Margrethe
  What did he say?

Bohr
  Nothing. I don’t know. I was too angry to take it in.

Margrethe
  Something about fission?

Bohr
  What happens in fission? You fire a neutron at a uranium nucleus, it splits, and it releases energy.

Margrethe
  A huge amount of energy. Yes?

Bohr
  About enough to move a speck of dust. But it also releases two or three more neutrons. Each of which has the chance of splitting another nucleus.

Margrethe
  So then those two or three split nuclei each release energy in their turn?

Bohr
  And two or three more neutrons.

Heisenberg
  You start a trickle of snow sliding as you ski. The trickle becomes a snowball …

Bohr
  An ever-widening chain of split nuclei forks through the uranium, doubling and quadrupling in millionths of a second from one generation to the next. First two splits, let’s say for simplicity. Then two squared, two cubed, two to the fourth, two to the fifth, two to the sixth …

Heisenberg
  The thunder of the gathering avalanche echoes from all the surrounding mountains …

Bohr
  Until eventually, after, let’s say, eighty generations, 2
⁸⁰
specks of dust have been moved. 2
⁸⁰
is a number with 24 noughts. Enough specks of dust to constitute a city, and all who live in it.