Copenhagen - Michael Frayn [23]
Bohr But, Heisenberg, Heisenberg! You also have been deflected! If people can see what’s happened to you, to their piece of light, then they can work out what must have happened to me! The trouble is knowing what’s happened to you! Because to understand how people see you we have to treat you not just as a particle, but as a wave. I have to use not only your particle mechanics, I have to use the Schrödinger wave function.
Heisenberg I know—I put it in a postscript to my paper.
Bohr Everyone remembers the paper—no one remembers the postscript. But the question is fundamental. Particles are things, complete in themselves. Waves are disturbances in something else.
Heisenberg I know. Complementarity. It’s in the postscript.
Bohr They’re either one thing or the other. They can’t be both. We have to choose one way of seeing them or the other. But as soon as we do we can’t know everything about them.
Heisenberg And off he goes into orbit again. Incidentally exemplifying another application of complementarity. Exactly where you go as you ramble around is of course completely determined by your genes and the various physical forces acting on you. But it’s also completely determined by your own entirely inscrutable whims from one moment to the next. So we can’t completely understand your behaviour without seeing it both ways at once, and that’s impossible. Which means that your extraordinary peregrinations are not fully objective aspects of the universe. They exist only partially, through the efforts of me or Margrethe, as our minds shift endlessly back and forth between the two approaches.
Bohr You’ve never absolutely and totally accepted complementarity, have 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 central tenets 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