So we like to think that we're kind of outdoors people.

And when you do large surveys, for example, NHANES survey, large epidemiologic sample, people are saying, oh, they spend like two, three hours outside every day.

And that sounds all right.

That sounds pretty good.

But when the US does a time use survey, You find out that people spend less than 15 minutes outside every day.

So kind of the retrospective is much rosier than the prospective, what people are actually getting.

So we spend vanishingly little time outside.

Mm-hmm.

Well, that leads right to what I wanted to ask you about, which is two things, why do we sleep and how is it related to our circadian rhythms? And maybe even, maybe you should define for those who haven't thought about circadian rhythms very much, uh, what are they and how do they relate to sleep?

Sure.

So circadian clock, something I didn't hear about until graduate school, so if, if people haven't heard about it, that, that's okay, though, though it is definitely more, more out there right now.

I think these are intrinsic 24-hour rhythms.

Um, I find them particularly appealing.

They, they are endogenous to an organism, and you find them in every single organism that has ever been studied on the planet Earth.

So there's obviously something incredibly important about them if throughout the evolutionary tree you see them.

Yep.

He's a sleep scientist from Stanford University.

And that bright sunshine closer to when you wake up is, in theory, going to strengthen your circadian clock, and this is the clock in your brain that basically helps to synchronize, um, all of your internal organs and all of your functioning to this 24-hour solar cycle that we exist in.

So, you've got all these other clocks in organs, right? You've got a clock in your liver.

You've got a clock in your lungs, in your immune cells.

So say for example, your body has this ability to figure out how many calories you need, but...

When your circadian clock is weaker, it's able to basically less accurately determine this.

There is this connection between your metabolism and expectation of food, when you're eating, how much you're expected to eat, and the circadian clock.

So the, the way that you can see this most easily is lots of data looking at individuals who do shift work.