Michael Frayn: Copenhagen

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 …