Authors: Michael Frayn
Heisenberg
Two thousand million people in the world, and the one who has to decide their fate is the only one who’s always hidden from me.
Bohr
You suggested a stroll.
Heisenberg
You remember Elsinore? The darkness inside the human soul …?
Bohr
And out we go. Out under the autumn trees.
Through the blacked-out streets.
Heisenberg
Now there’s no one in the world except Bohr and the invisible other. Who is he, this all-enveloping presence in the darkness?
Margrethe
The flying particle wanders the darkness, no one knows where. It’s here, it’s there, it’s everywhere and nowhere.
Bohr
With careful casualness he begins to ask the question he’s prepared.
Heisenberg
Does one as a physicist have the moral right to work on the practical exploitation of atomic energy?
Margrethe
The great collision.
Bohr
I stop. He stops …
Margrethe
This is how they work.
Heisenberg
He gazes at me, horrified.
Margrethe
Now at last he knows where he is and what he’s doing.
Heisenberg
He turns away.
Margrethe
And even as the moment of collision begins it’s over.
Bohr
Already we’re hurrying back towards the house.
Margrethe
Already they’re both flying away from each other into the darkness again.
Heisenberg
Our conversation’s over.
Bohr
Our great partnership.
Heisenberg
All our friendship.
Margrethe
And everything about him becomes as uncertain as it was before.
Bohr
Unless … yes … a thought-experiment .… Let’s suppose for a moment that I don’t go flying off into the
night. Let’s see what happens if instead I remember the paternal role I’m supposed to play. If I stop, and control my anger, and turn to him. And ask him why.
Heisenberg
Why?
Bohr
Why are you confident that it’s going to be so reassuringly difficult to build a bomb with 235? Is it because you’ve done the calculation?
Heisenberg
The calculation?
Bohr
Of the diffusion in 235. No. It’s because you haven’t calculated it. You haven’t considered calculating it. You hadn’t consciously realised there was a calculation to be made.
Heisenberg
And of course now I
have
realised. In fact it wouldn’t be all that difficult. Let’s see .… The scattering cross-section’s about 6 × 10
−24
, so the mean free path would be … Hold on …
Bohr
And suddenly a very different and very terrible new world begins to take shape …
Margrethe
That was the last and greatest demand that Heisenberg made on his friendship with you. To be understood when he couldn’t understand himself. And that was the last and greatest act of friendship for Heisenberg that you performed in return. To leave him misunderstood.
Heisenberg
Yes. Perhaps I should thank you.
Bohr
Perhaps you should.
Margrethe
Anyway, it was the end of the story.
Bohr
Though perhaps there was also something I should thank
you
for. That summer night in 1943, when I escaped across the Sound in the fishing-boat, and the freighters arrived from Germany …
Margrethe
What’s that to do with Heisenberg?
Bohr
When the ships arrived on the Wednesday there were eight thousand Jews in Denmark to be arrested and
crammed into their holds. On the Friday evening, at the start of the Sabbath, when the SS began their round-up, there was scarcely a Jew to be found.
Margrethe
They’d all been hidden in churches and hospitals, in people’s homes and country cottages.
Bohr
But how was that possible?—Because we’d been tipped off by someone in the German Embassy.
Heisenberg
Georg Duckwitz, their shipping specialist.
Bohr
Your man?
Heisenberg
One of them.
Bohr
He was a remarkable informant. He told us the day before the freighters arrived—the very day that Hitler issued the order. He gave us the exact time that the SS would move.
Margrethe
It was the Resistance who got them out of their hiding-places and smuggled them across the Sound.
Bohr
For a handful of us in one fishing smack to get past the German patrol-boats was remarkable enough. For a whole armada to get past, with the best part of eight thousand people on board, was like the Red Sea parting.
Margrethe
I thought there
were
no German patrol-boats that night?
Bohr
No—the whole squadron had suddenly been reported unseaworthy.
Heisenberg
How they got away with it I can’t imagine.
Bohr
Duckwitz again?
Heisenberg
He also went to Stockholm and asked the Swedish Government to accept everyone.
Bohr
So perhaps I should thank you.
Heisenberg
For what?
Bohr
My life. All our lives.
Heisenberg
Nothing to do with me by that time. I regret to say.
Bohr
But after I’d gone you came back to Copenhagen.
Heisenberg
To make sure that our people didn’t take over the Institute in your absence.
Bohr
I’ve never thanked you for that, either.
Heisenberg
You know they offered me your cyclotron?
Bohr
You could have separated a little 235 with it.
Heisenberg
Meanwhile you were going on from Sweden to Los Alamos.
Bohr
To play my small but helpful part in the deaths of a hundred thousand people.
Margrethe
Niels, you did nothing wrong!
Bohr
Didn’t I?
Heisenberg
Of course not. You were a good man, from first to last, and no one could ever say otherwise. Whereas I …
Bohr
Whereas you, my dear Heisenberg, never managed to contribute to the death of one single solitary person in all your life.
Margrethe
Well, yes.
Heisenberg
Did I?
Margrethe
One. Or so you told us. The poor fellow you guarded overnight, when you were a boy in Munich, while he was waiting to be shot in the morning.
Bohr
All right then, one. One single soul on his conscience, to set against all the others.
Margrethe
But that one single soul was emperor of the universe, no less than each of us. Until the morning came.
Heisenberg
No, when the morning came I persuaded them to let him go.
Bohr
Heisenberg, I have to say—if people are to be measured strictly in terms of observable quantities …
Heisenberg
Then we should need a strange new quantum ethics. There’d be a place in heaven for me. And another one for the SS man I met on my way home from Haigerloch. That was the end of my war. The Allied troops were closing in; there was nothing more we could do. Elisabeth and the children had taken refuge in a village in Bavaria, so I went to see them before I was captured. I had to go by bicycle—there were no trains or road transport by that time—and I had to travel by night and sleep under a hedge by day, because all through the daylight hours the skies were full of Allied planes, scouring the roads for anything that moved. A man on a bicycle would have been the biggest target left in Germany. Three days and three nights I travelled. Out of Württemberg, down through the Swabian Jura and the first foothills of the Alps. Across my ruined homeland. Was this what I’d chosen for it? This endless rubble? This perpetual smoke in the sky? These hungry faces? Was this my doing? And all the desperate people on the roads. The most desperate of all were the SS. Bands of fanatics with nothing left to lose, roaming around shooting deserters out of hand, hanging them from roadside trees. The second night, and suddenly there it is—the terrible familiar black tunic emerging from the twilight in front of me. On his lips as I stop—the one terrible familiar word. ‘Deserter,’ he says. He sounds as exhausted as I am. I give him the travel order I’ve written for myself. But there’s hardly enough light in the sky to read by, and he’s too weary to bother. He begins to open his holster instead. He’s going to shoot me because it’s simply less labour. And suddenly I’m thinking very quickly and clearly—it’s like skiing, or that night on Heligoland, or the one in Faelled Park. What comes into my mind this time is the pack of American cigarettes I’ve got in my pocket. And already it’s in my hand—I’m holding it out to him. The most desperate solution to a problem yet. I wait while he stands there looking at it, trying to make it out, trying to think, his left hand holding my useless piece of
paper, his right on the fastening of the holster. There are two simple words in large print on the pack: Lucky Strike. He closes the holster, and takes the cigarettes instead .… It had worked, it had worked! Like all the other solutions to all the other problems. For twenty cigarettes he let me live. And on I went. Three days and three nights. Past the weeping children, the lost and hungry children, drafted to fight, then abandoned by their commanders. Past the starving slave-labourers walking home to France, to Poland, to Estonia. Through Gammertingen and Biberach and Memmingen. Mindelheim, Kaufbeuren, and Schöngau. Across my beloved homeland. My ruined and dishonoured and beloved homeland.
Bohr
My dear Heisenberg! My dear friend!
Margrethe
Silence. The silence we always in the end return to.
Heisenberg
And of course I know what they’re thinking about.
Margrethe
All those lost children on the road.
Bohr
Heisenberg wandering the world like a lost child himself.
Margrethe
Our own lost children.
Heisenberg
And over goes the tiller once again.
Bohr
So near, so near! So slight a thing!
Margrethe
He stands in the doorway, watching me, then he turns his head away …
Heisenberg
And once again away he goes, into the dark waters.
Bohr
Before we can lay our hands on anything, our life’s over.
Heisenberg
Before we can glimpse who or what we are, we’re gone and laid to dust.
Bohr
Settled among all the dust we raised.
Margrethe
And sooner or later there will come a time when all our children are laid to dust, and all our children’s children.
Bohr
When no more decisions, great or small, are ever made again. When there’s no more uncertainty, because there’s no more knowledge.
Margrethe
And when all our eyes are closed, when even the ghosts have gone, what will be left of our beloved world? Our ruined and dishonoured and beloved world?
Heisenberg
But in the meanwhile, in this most precious meanwhile, there it is. The trees in Faelled Park. Gammertingen and Biberach and Mindelheim. Our children and our children’s children. Preserved, just possibly, by that one short moment in Copenhagen. By some event that will never quite be located or defined. By that final core of uncertainty at the heart of things.
Where a work of fiction features historical characters and historical events it’s reasonable to want to know how much of it is fiction and how much of it is history. So let me make it as clear as I can in regard to this play.
The central event in it is a real one. Heisenberg
did
go to Copenhagen in 1941, and there
was
a meeting with Bohr, in the teeth of all the difficulties encountered by my characters. He almost certainly went to dinner at the Bohrs’ house, and the two men almost certainly went for a walk to escape from any possible microphones, though there is some dispute about even these simple matters. The question of what they actually said to each other has been even more disputed, and where there’s ambiguity in the play about what happened, it’s because there is in the recollection of the participants. Much more sustained speculation still has been devoted to the question of what Heisenberg was hoping to achieve by the meeting. All the alternative and co-existing explications offered in the play, except perhaps the final one, have been aired at various times, in one form or another.
Most anxious of all to establish some agreed version of the meeting was Heisenberg himself. He did indeed go back in 1947 with his British minder, Ronald Fraser, and attempted to find some common ground in the matter with Bohr. But it proved to be too delicate a task, and (according to Heisenberg, at any rate, in his memoirs) ‘we both came to feel that it would be better to stop disturbing the spirits of the past.’ This is where my play departs from the historical record, by supposing that at some later time, when everyone involved had become spirits of the past themselves, they argued the question out further, until they had achieved a little more understanding of what was going on, just as they had so many times when they were alive with the intractable difficulties presented by the internal workings of the atom.