Sean Carroll

And there's another observer who shares a past with you who is in the other thing that we call the other branch of the wave function.

So that's many worlds.

I didn't even mean to get into many worlds that much.

But the point is that the formalism of many worlds just says there are wave functions and they obey the Schrodinger equation.

Everything else is derived from that.

In the Copenhagen view, you postulate a whole bunch of other things.

You postulate the existence of something called measurement.

the wave function collapses, that there's a probability rule, the Born rule for how often they collapse, all this extra postulates.

And in Everett, you have no extra postulates.

That's good for traditional measures of scientific simplicity.

The fewer postulates, the fewer axioms you have for your theory, the better.

It's bad for the philosophical task of connecting the formalism to reality, right?

Because whatever it is saying is, you know, I just trust the equations.

They're telling me what happens.

And as long as I interpret who I am in the equations correctly, I'm going to fit the data.

But that interpretation of who you are in the wave function is a highly non-trivial thing.

That requires a little bit of work.

So, Everettian quantum mechanics is much more philosophical heavy lifting than Copenhagen or really any other version of quantum mechanics.

Well, it's—sorry, I shouldn't say that.

There's different philosophical heavy lifting in Copenhagen.