Hi, you're about to get smarter in just a few minutes with Curiosity Daily from Curiosity.com.

I'm Cody Gough.

And I'm Ashley Hamer.

Today you learn how GPS clocks work from the engineer who made GPS clocks in the first place, Hugo Fruehoff.

But first you'll learn about how researchers finally figured out why stress can turn your hair gray.

Let's let us find some curiosity.

We've known for a long time that stress can make your hair go gray or white.

Think Barack Obama, George W Bush, or Rogue from X-Men.

Though strictly speaking, stress is not what turnedues, hair white, depending on if you're referring to the comics or the movies, you know what I'm not going to get into it.

Look, man, I saw the movies. It seemed like a very stressful situation she was in.

Okay, that's fair. I guess if you're absorbing Magdito's powers, yeah, yeah, all right, that's fair.

But for a long time, scientists didn't have any idea why stress turned your hair gray.

Well, a huge team of researchers led by Harvard University has just figured it out,

and it involves our old friend, the fight or flight response.

The researcher's first job was to figure out which body system is responsible for

translating stressful situations into gray hair.

Their first thought was that the immune system might be attacking itself.

So they got their hands on some mice without immune cells

and put them under stress.

When those mice turned gray, the researchers knew that wasn't the cause. Then they turned the infamous stress hormone

cortisol. They removed the adrenal glands from a new batch of mice and subjected them to stress.

Again, they went gray. Then they turned to the sympathetic nervous

...