Sean Carroll

The point about density is interesting because I absolutely would not have guessed that. Maybe, again, my naive physicist thinking is water is more or less constant density, but the pressure can change a lot. But, of course, you're pointing out that the temperature and the salinity change considerably, or change a little bit but have considerable implications, I guess I should say.

The point about density is interesting because I absolutely would not have guessed that. Maybe, again, my naive physicist thinking is water is more or less constant density, but the pressure can change a lot. But, of course, you're pointing out that the temperature and the salinity change considerably, or change a little bit but have considerable implications, I guess I should say.

Is it at least uniform? Is it monotonic? Does it just get colder and more saline as we get deeper and deeper?

Is it at least uniform? Is it monotonic? Does it just get colder and more saline as we get deeper and deeper?

I had not thought of that. I mean, I know that Europa, for example, the moon of Jupiter, has an enormous amount of water hidden underneath ice, but we don't know much about it, much about its structure. So you oceanographers are going to have to figure out the theory of it so that we can predict it before we go there.

I had not thought of that. I mean, I know that Europa, for example, the moon of Jupiter, has an enormous amount of water hidden underneath ice, but we don't know much about it, much about its structure. So you oceanographers are going to have to figure out the theory of it so that we can predict it before we go there.

And OK, so we have these layers. We have stratification based on density. But then, as you say, there are movements, mostly horizontal. In fact, you have a map right at the beginning of the book of what the currents are. It always struck me a little bit that the currents are that well-defined that you can make a map of them. Do they not change that much from day to day? Is it so predictable?

And OK, so we have these layers. We have stratification based on density. But then, as you say, there are movements, mostly horizontal. In fact, you have a map right at the beginning of the book of what the currents are. It always struck me a little bit that the currents are that well-defined that you can make a map of them. Do they not change that much from day to day? Is it so predictable?

Well, yeah.

Well, yeah.

But this sounds very complicated and should make you want to switch to particle physics.

But this sounds very complicated and should make you want to switch to particle physics.

That's true. No, yeah. I mean, Caltech, there was turtles in a little koi pond, but it's not really part of the day-to-day work of the institution. You mentioned this. I'm biting my tongue because I want to get into the various ways which this dynamism happens and we understand it. But

That's true. No, yeah. I mean, Caltech, there was turtles in a little koi pond, but it's not really part of the day-to-day work of the institution. You mentioned this. I'm biting my tongue because I want to get into the various ways which this dynamism happens and we understand it. But

You alluded to a little bit how we learn about it, and I do want to give some airtime to the experimental side of things. How do we know all these wonderful things you're telling us? Is it mostly because we human beings go down there and visit, or do we send robots, or do we just use remote sensing?

You alluded to a little bit how we learn about it, and I do want to give some airtime to the experimental side of things. How do we know all these wonderful things you're telling us? Is it mostly because we human beings go down there and visit, or do we send robots, or do we just use remote sensing?

Yeah.

Yeah.

The point about satellites is a really interesting one because I think people don't appreciate that water in general is just not as transparent as you would like it to be. Before our conversation, I went to Google Maps just to see what it would show me if I looked at the ocean rather than the local streets, etc. And interestingly, they have clearly cheated.

The point about satellites is a really interesting one because I think people don't appreciate that water in general is just not as transparent as you would like it to be. Before our conversation, I went to Google Maps just to see what it would show me if I looked at the ocean rather than the local streets, etc. And interestingly, they have clearly cheated.