It is May 15th, and you decide that this year you're going to get a suntan,

a glorious, beautiful, tropical sun tan.

So you decide to go out in the backyard to spare the neighbors and other innocent bypassers

and lay out at lunchtime, catch a ray or two.

So you lie on your back for 15 minutes,

flip over on your belly for 15 minutes, then you get up, come in, eat lunch, go back to work.

Now that night, your skin is a little pink. So the next day you just eat lunch, but the following day, you're back

outside for your 15 minutes per side sun bath. You are faithful to your schedule, spending 30 minutes

outside every day that week, because that's the kind of disciplined, determined person you are.

At the end of the week, you have turned a more pleasant shade of brown and, heartened by your

results, resolved to maintain your 30 minutes a day schedule for the rest of the month.

So here is the critical question.

At the end of the month, what color is your skin?

If you ask 100 people this question, 95 of them will tell you that it will be really, really, really dark.

But, in fact, it will be exactly the same color as it was at the end of the first week.

Why would it be any darker?

Your skin adapts to the stress of the sun exposure by becoming dark enough to prevent itself from burning again.

That's why it tans to prevent the burn. It's the only reason it gets dark.

And it adapts exactly and specifically to the stress that burned it.

Your skin does not know that you want it to get darker.

It only knows what the sun told it, and the sun only talked to it for 15 minutes per sight.

It can't get any darker than the 15 minutes makes it get, because the 15 minutes is what it is adapting to. If you just got darker every time

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