A Moment of Science

Moon Tanning?

Can spending enough time under a very bright moon get you tan?

The moon shines over a brightly lit city

Photo: R Motti

Tanning occurs when our skin produces melanin in reaction to the ultraviolet light of the sun.

Could the moon ever cause you to tan? After all, moonlight is reflected sunlight. If direct sunlight can cause you to tan and even burn, then why not reflected sunlight?

Sure, moonlight clearly isn’t as strong as light coming directly from the sun. But, perhaps enough exposure to a radiant moon could cause a very light tan.

Good News

The actual answer, as you may have guessed, is no. You can’t get a tan from the moon, no matter how bright. You see, we tan when our skin produces melanin in reaction to the sun’s ultraviolet light.

Ultraviolet rays are harmful; they can cause skin damage and even cancer. Our skin produces melanin as a defense against ultraviolet rays. Melanin absorbs ultraviolet radiation, thereby protecting the skin’s cells. So the more ultraviolet light, the more melanin our skin will produce.

Ultraviolet Light

The catch is that it takes a certain amount of ultraviolet sunlight to make the skin produce melanin. Sunlight reaching us via the moon just doesn’t have enough ultraviolet oomph to trigger the skin’s defensive shield.

A full moon may look really bright, but the surface of the moon is actually pretty dark. The moon absorbs most of the sunlight that hits it.

Three-Hundred Year Moon Tan

Of course, some of the sun’s reflected ultraviolet light does reach us. Theoretically, prolonged exposure to moonlight could cause some damage.

In this case “prolonged” means hundreds of years of continuous moon bathing. Under normal conditions our skin quickly repairs whatever minimal damage is caused by the light of the silvery moon.

  • aetherwise

    thanks don

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