Free Copenhagen by Michael Frayn

you?
    Heisenberg   Yes! Absolutely and totally! I defended it at the Como Conference in 1927! I have adhered to it ever afterwards with religious fervour! You convinced me. I humbly accepted your criticisms.
    Bohr   Not before you’d said some deeply wounding things.
    Heisenberg   Good God, at one point you literally reduced me to tears!
    Bohr   Forgive me, but I diagnosed them as tears of frustration and rage.
    Heisenberg   I was having a tantrum?
    Bohr   I have brought up children of my own.
    Heisenberg   And what about Margrethe? Was she having a tantrum? Klein told me you reduced her to tears after I’d gone, making her type out your endless redraftings of the complementarity paper.
    Bohr   I don’t recall that.
    Margrethe   I do.
    Heisenberg   We had to drag Pauli out of bed in Hamburg once again to come to Copenhagen and negotiate peace.
    Bohr   He succeeded. We ended up with a treaty. Uncertainty and complementarity became the two centraltenets of the Copenhagen Interpretation of Quantum Mechanics.
    Heisenberg   A political compromise, of course, like most treaties.
    Bohr   You see? Somewhere inside you there are still secret reservations.
    Heisenberg   Not at all—it works. That’s what matters. It works, it works, it works!
    Bohr   It works, yes. But it’s more important than that. Because you see what we did in those three years, Heisenberg? Not to exaggerate, but we turned the world inside out! Yes, listen, now it comes, now it comes .… We put man back at the centre of the universe. Throughout history we keep finding ourselves displaced. We keep exiling ourselves to the periphery of things. First we turn ourselves into a mere adjunct of God’s unknowable purposes, tiny figures kneeling in the great cathedral of creation. And no sooner have we recovered ourselves in the Renaissance, no sooner has man become, as Protagoras proclaimed him, the measure of all things, than we’re pushed aside again by the products of our own reasoning! We’re dwarfed again as physicists build the great new cathedrals for us to wonder at—the laws of classical mechanics that predate us from the beginning of eternity, that will survive us to eternity’s end, that exist whether we exist or not. Until we come to the beginning of the twentieth century, and we’re suddenly forced to rise from our knees again.
    Heisenberg   It starts with Einstein.
    Bohr   It starts with Einstein. He shows that measurement—measurement, on which the whole possibility of science depends—measurement is not an impersonal event that occurs with impartial universality. It’s a human act, carried out from a specific point of view in time and space, from the one particular viewpoint of a possible observer. Then, here in Copenhagen in those three years in the mid-twenties we discover that there is no precisely determinableobjective universe. That the universe exists only as a series of approximations. Only within the limits determined by our relationship with it. Only through the understanding lodged inside the human head.
    Margrethe   So this man you’ve put at the centre of the universe—is it you, or is it Heisenberg?
    Bohr   Now, now, my love.
    Margrethe   Yes, but it makes a difference.
    Bohr   Either of us. Both of us. Yourself. All of us.
    Margrethe   If it’s Heisenberg at the centre of the universe, then the one bit of the universe that he can’t see is Heisenberg.
    Heisenberg   So …
    Margrethe   So it’s no good asking him why he came to Copenhagen in 1941. He doesn’t know!
    Heisenberg   I thought for a moment just then I caught a glimpse of it.
    Margrethe   Then you turned to look.
    Heisenberg   And away it went.
    Margrethe   Complementarity again. Yes?
    Bohr   Yes, yes.
    Margrethe   I’ve typed it out often enough. If you’re doing something you have to concentrate on you can’t also be thinking about doing it, and if you’re thinking about doing it then you can’t