Dr. Samer Hattar

My pleasure.

So, I mean, you do appreciate the effect of light for vision.

So when you wake up in a beautiful area, beautiful ocean, light is essential.

The sunrise, the sunset.

So that's your conscious perception of light.

But light has a completely different aspect that is independent of conscious vision.

And that's how it regulates many important functions in your body.

I think the best that is well-studied and well-known is your circadian clock.

And the word circadian comes from the word circa, which is approximate, and DN is day.

So it's an approximate day.

Why is it an approximate day?

Because if I put you or any other human being who have a normal circadian clock in a constant conditions,

with no information about feeding time, about sleep time, about what time it is outside, you still have a daily rhythm, but it's not exactly 24 hours.

So it will shift out of the solar day because it's not exactly 24 hours and hence the name circadian.

It shows up at every level that we know we studied.

It shows up at the level of the cell.

It shows up at the level of the tissue.

And it shows up at your behavior.

The most obvious for you is your sleep-wake cycle.

You sleep and you're awake and sleep at the 24-hour rhythms.