Sean Carroll

So I think that you have a fair point if you're worried that people who talk about these things, including myself, sometimes do it sloppily.

They say things without all the caveats attached to every single sentence or every single word in every single sentence.

But I think the meaning is clear.

People are arguing about, you know, what are the ingredients in your most fundamental description of the world?

And those ingredients are your ontology.

It would be very different in quantum mechanics than it would be in classical mechanics, that's for sure.

No, certainly not.

Like, I don't even think that perpetual motion machines are impossible as a matter of logic, right?

They're impossible as a matter of the laws of physics as we currently understand them.

That's true enough.

But the laws of physics, as we currently understand them, might not be right.

So I wouldn't even call that impossible.

I would say it violates the laws of physics.

Cold fusion, as far as we know, doesn't even necessarily violate the laws of physics.

When it first came out, that was like when I first arrived at graduate school, roughly speaking.

So I was at Harvard, and there were people in the physics department, applied physics, astronomy, who were thinking very hard about, you know, could this work?

Could we understand this?

Could we do the math?

understand quantum tunneling and nuclei and things like that.

And they basically all came around and said, no, it doesn't seem to actually work.