Sean Carroll

I think this is really a typical physicist, I don't want to think too hard about these tricky questions kind of attitude that says, you have a theory, your theory makes predictions, the predictions came out wrong, your theory is wrong.

And my response to that would be, you know, again, since I think I'm not a typical observer, I'm a person with certain data, at least, you know, apparently, that therefore I do agree with their conclusion.

that I want to exclude cosmologies that are dominated by Boltzmann fluctuations, but I think they're doing it for the wrong reason.

And as often happens, nobody cares when you have that move where you're getting the same answer they did for a slightly different reason.

That's not going to change their worldview very much.

I got it.

Okay, but you have a slightly different take.

You just came out with a new paper on Boltzmann brains.

Do you want to explain what you're thinking about?

I think, yeah, I get it, and I want to follow up.

But first, maybe to clarify something that might be confusing some listeners, because I think a lot of people think the phrase, you're a Boltzmann brain, implies that I should not see the office around me and all these things.

And indeed—

In an eternally fluctuating cosmology, there will be a lot more disembodied brains in empty space than people who see offices or rooms or whatever.

But the point is, I think you're relying on when you say maybe I'm a Boltzmann brain, is that even most of the people who think they're in offices, or who are in offices for that matter, in these cosmologies are still random fluctuations.

They don't have reliable connections to the past.

It's a sad short life, which, you know, cosmically all lives are, but there's still a matter of degree here that we should try to press on.

So good.

So my strategy that I suggested was, look, if I lived in this universe where everything was a random fluctuation or most things were, I would have no reason to believe my thoughts about physics and the state of the universe.

Therefore, I cannot simultaneously think

think that I am a Boltzmann fluctuation, and think I have good reasons for thinking I'm a Boltzmann fluctuation.