Sean Carroll

Ed Sedstuff says, if there were practically infinite universes, would math necessarily be useful in all of them?

Well, it depends on what you mean by useful.

I'm tempted to just say yes, that the math would be useful in all of them.

But of course, many of them, well, sorry, I need to back up because you didn't say all conceivable universes.

You just said a practically infinite number of universes.

So you could absolutely imagine a practically infinite number of universes and still nowhere near all conceivable universes, right?

But if you were thinking about all conceivable universes, many of them would be anthropically disallowed.

That is to say, there's no way for intelligent conscious creatures to exist in these universes.

And if you're skeptical about that, if you think, well, maybe life is really much more robust than you think it is, most possible universes don't have laws of physics.

Or at least they don't have predictability and reliability in any way that we can imagine.

I mean given any –

universe, I can take the universe and I can sort of stop it at one moment of time and then just have complete random nonsense after that moment, right?

There's no reliability of what's going to happen from one moment to another if you don't have these laws of physics that are always obeyed.

That to me is sort of an interesting tension for people who are Humean about the laws of physics, like myself.

People who think that there's no separate ontological existence for laws of physics.

There's just the world that falls into the patterns that it falls into.

And then you can ask why.

Why are the patterns so rigidly enforced?

What is the enforcement mechanism, et cetera?

But anyway, I do think that there wouldn't be observers in most of the possible universes that we can think about.