Carlo Rovelli: Free Will Is Real. Physics Can Prove It.

Carlo Rovelli (0:00)

It's not true that things get disordered. In fact, very often in nature, things left alone get ordered. To imagine that to be free, you have to violate the laws of nature is stupid. You, Brian, can be in a superposition. You can be in LA and also in San Francisco. Your head, it's older than your feet.

Brian Keating (0:21)

That was Carlo Rovelli, one of the men who built loop quantum gravity, telling me that the second law doesn't say what I think it does, but he didn't stop there. Over the next hour, he's going to take apart the three things you were told that just ain't so. Ranging from the frost on the window where you may be sitting right now, to the clock on your wall. And the clock is the one that really got me. He blew my mind by telling me that my head is older than my feet. And then he told me why that's the least strange thing he was going to say. So Carlo, let's start with the frost. You're telling me that things left alone can get more ordered? That's not what I was taught. Walk us through that.

Carlo Rovelli (0:54)

First of all, I do think that the thermodynamic arrow is very basic. A lot of phenomena which we connect to the direction of time, for instance. I remember our last conversation. We don't remember our next conversation. We have a picture of Brian young. We don't have a picture of Brian old. We can decide where to go to dinner tomorrow, but we cannot decide where to go to dinner yesterday. There is a profound difference between future and past. I got convinced in the last 10 years, working a lot about that, I've read a lot of paper, that all these differences can all be traced to the thermodynamics arrow of time, to the entropic arrow of time. It's not obvious, but the reason we have memories of the past and not the future has to do with entropy growing. If it wasn't for entropy, there wouldn't be this de-symmetry between. Now, have we fully understood the story? No, I think there are various aspects that we still get confused. There are also, as you say, aspects that we over-simplify badly. Let me give you an example, which is dear to me. We always make this story. Take latte, coffee, and mix, and look, they mix. In fact, take water and vinegar, put some vinegar in water, mix, and they mix.

Now, take water and oil, mix, they separate.

Is this contradicting our entire understanding of the universe? No, it's just things a little bit more complicated than the way they usually said. It's not true that under any definition of order or disorder, things get disordered. In fact, very often in nature, things left alone get ordered, and oil and water separating is one of the many examples of that. If you have a box with balls, you shake, and then you put it there on the table, all the balls go very nicely in order on the bottom.

They order themself. If you look at the beach, the ocean, all the little grains are together and the big stones on another side of the beach. They order by the same. Who ordered them?

If you look at frost, the beautiful ordered structure, who ordered them? A lot of things in nature will get ordered by themselves. The idea that entropy is disorder, careful, under proper definition of order, under proper definition of everything, that most of the things we call order and disorder are not connected to entropy in the way it's usually said. That's one example in which popular science is bad. In fact, maybe scientists are very confused about that themselves. And that's important, right? Because people are surprised because biology came in. The very complexity of biology. Biology is a lot of order. So on the crust of our planet, the Earth, there's all this structure that formed. Okay, people say, oh, this seems to be against entropy. You know why? Entropy grows and create orders just happen all over.

Brian Keating (4:12)

Let's talk about the early universe. You already mentioned the block universe and our mutual distaste of that hypothesis. I don't like that. I want to ask the why question. I really I do want to ask the why question, but I know why questions are not usually answerable. But the universe was somewhat lower entropy, right? It was in a very special configuration.

Does that, in your mind, point to some reason why the arrow of time points in one direction?

Carlo Rovelli (4:38)

Yeah. Yeah, the two are very connected. It's not that one explains the other one, because we need an explanation for either. I think the past low entropy and the arrow of time, second law of thermodynamics, different manners of explaining, of pointing out to the same phenomenon, about which I think there is more to learn.