Sean Carroll

If our universe continues to expand and has a positive cosmological constant and lasts that way forever, we will enter the de Sitter vacuum state, and that has a non-zero temperature. So we say that Minkowski space, that is to say space-time without a cosmological constant, it has its vacuum state. and its temperature is zero.

If our universe continues to expand and has a positive cosmological constant and lasts that way forever, we will enter the de Sitter vacuum state, and that has a non-zero temperature. So we say that Minkowski space, that is to say space-time without a cosmological constant, it has its vacuum state. and its temperature is zero.

If you have a thermometer there and just let it equilibrate with the vacuum, it will say zero degrees. Whereas in de Sitter space, there's a non-zero temperature. The thermometer you put there comes to equilibrium at a non-zero temperature.

If you have a thermometer there and just let it equilibrate with the vacuum, it will say zero degrees. Whereas in de Sitter space, there's a non-zero temperature. The thermometer you put there comes to equilibrium at a non-zero temperature.

But that temperature is so extraordinarily, incredibly low, the wavelength of a typical photon that is observed, that is being measured, is as big as the universe. So if you're confined to a tiny little region of space, you're never going to detect those photons. To you, it's going to look like empty space. So there is some commonality in all these different notions of vacuum state.

But that temperature is so extraordinarily, incredibly low, the wavelength of a typical photon that is observed, that is being measured, is as big as the universe. So if you're confined to a tiny little region of space, you're never going to detect those photons. To you, it's going to look like empty space. So there is some commonality in all these different notions of vacuum state.

George Candelopoulos says, Can you explain how matter and information are linked in these contexts? You know, I think it's a little bit casual, to be honest. I don't think there's a hard and fast set of rules there. Physicists are just as prone to speaking casually as anyone else, especially when they hope and think that the people around them will get what they are trying to say.

George Candelopoulos says, Can you explain how matter and information are linked in these contexts? You know, I think it's a little bit casual, to be honest. I don't think there's a hard and fast set of rules there. Physicists are just as prone to speaking casually as anyone else, especially when they hope and think that the people around them will get what they are trying to say.

But I do think that part of it is that as we dig more and more deeply into quantum mechanics and quantum gravity and emergent space time and things like that, the fundamental stuff out of which the universe is made is a little bit less tangible than you might have thought. You know, in Newtonian, when Newton wrote the Principia, if you said, what is the universe made of?

But I do think that part of it is that as we dig more and more deeply into quantum mechanics and quantum gravity and emergent space time and things like that, the fundamental stuff out of which the universe is made is a little bit less tangible than you might have thought. You know, in Newtonian, when Newton wrote the Principia, if you said, what is the universe made of?

He would have said, well, some particles, right? He even thought light was particles, corpuscles. But he's mostly thinking of, you know, the Earth is a particle, or at least is made of particles. He didn't know about atoms, but, you know, he could imagine it was made of matter and things like that. And all that stuff existed in space. And it's all things you can see and touch.

He would have said, well, some particles, right? He even thought light was particles, corpuscles. But he's mostly thinking of, you know, the Earth is a particle, or at least is made of particles. He didn't know about atoms, but, you know, he could imagine it was made of matter and things like that. And all that stuff existed in space. And it's all things you can see and touch.

Whereas if, like me, you're trying to show how gravity can emerge from quantum information, well, you can very well ask quantum information about what? But the answer is some abstract, d-dimensional factor of Hilbert space. You know, what help is that? It doesn't seem as material as a particle moving through space. It is, by the way, just as material.

Whereas if, like me, you're trying to show how gravity can emerge from quantum information, well, you can very well ask quantum information about what? But the answer is some abstract, d-dimensional factor of Hilbert space. You know, what help is that? It doesn't seem as material as a particle moving through space. It is, by the way, just as material.

It's just we're learning better what material means. And that's why... At a philosophical level, what used to be called materialism as a philosophy of nature is these days much more likely to be labeled physicalism as a philosophy of nature, because it's a little bit misleading to refer to the ultimate stuff of reality as matter. It's more abstract than that.

It's just we're learning better what material means. And that's why... At a philosophical level, what used to be called materialism as a philosophy of nature is these days much more likely to be labeled physicalism as a philosophy of nature, because it's a little bit misleading to refer to the ultimate stuff of reality as matter. It's more abstract than that.

Not that it's any fundamentally less existent or anything like that, but we're not as familiar with it from our everyday lives. And what matters to us about it is the information that it contains. So physicists tend to talk that way just to go along with what their theories are telling them. Stevie CPW says, do you invest in the stock market?

Not that it's any fundamentally less existent or anything like that, but we're not as familiar with it from our everyday lives. And what matters to us about it is the information that it contains. So physicists tend to talk that way just to go along with what their theories are telling them. Stevie CPW says, do you invest in the stock market?

And if yes, what is your investing strategy or philosophy? Close to no. You know, I probably should. I don't have enough money to be a major player in the stock market. Let's put it that way. I do have some retirement savings from working for many years at universities. And mostly I put those into index funds. That is to say, just follow the S&P 500 or whatever.

And if yes, what is your investing strategy or philosophy? Close to no. You know, I probably should. I don't have enough money to be a major player in the stock market. Let's put it that way. I do have some retirement savings from working for many years at universities. And mostly I put those into index funds. That is to say, just follow the S&P 500 or whatever.