Sean Carroll

Because when you look to see where's the electron and where's the proton, you're going to see them somewhere.

And the example I gave of electrons and protons being in different boxes, that's just one possible wave function.

That's not necessarily built into the idea of a wave function.

You could have a different wave function which says they're both in the same box, okay?

Or they're both definitely in box A. Like there's all different possible wave functions, but you've opened up a new possibility.

because of entanglement in quantum mechanics, that you don't know which box the electron's in, but you know it's not in the same box as the proton.

Or even better, just to be very, very precise about it, because I know that you people are sticklers and you're listening closely, it is a superposition of both of those possibilities, and there's no such thing in that wave function as where the electron is.

This is a crucial feature of quantum mechanics, that the wave function appears as a real thing.

This is precisely what the Copenhagen interpretation denies, but there's all sorts of good reasons not to deny it, and that's one of the reasons why the more you think about the foundations of quantum mechanics, the less you like the Copenhagen interpretation.

So again, not everyone agrees, but I'm giving my views here, and this is a solo podcast, no guest that I have to put up with, you're just listening to me.

So in my view, the wave function is the real thing, and if that wave function says the electron has some possibility of being in box A and some possibility of being in box B, then there's no such thing as where the electron is, really.

What there is is the wave function, which is a combination, a superposition of all of those possibilities.

OK, so that's quantum mechanics.

I hope that made sense.

There's more to be said about quantum mechanics, but that's the basic ontology, we would say, of the theory, what it says really exists.

We're working for the purposes of this podcast in a realist ontology for the quantum wave function.

We think the wave functions represent reality, OK?

And the Copenhagen interpretation goes on to say you don't measure all of reality when you do a measurement.

You see a version of it, and you can only predict the probability that you see some version of it.

Many worlds, by contrast—and we're not going to get into the worlds aspect of many worlds that much because it's actually not relevant for what we're talking about today.