A Moment of Science

The Color of Dark

Did you ever notice that things get boring at night? I don’t mean your social life, I mean the way the world looks. As the sunlight fades, the colors vanish as well.

This isn’t because colors go away, exactly; it’s because human eyes can’t sense color without a certain amount of light. After all, color is just light of a particular frequency bouncing off an object, and when there’s too little light bouncing around, everything looks gray. But lest we assume that everybody sees the world the way we do, researchers now have good evidence that there are species that can still make out color at night.

Who are these color-gifted critters? Hawkmoths. Almut Kelber from Sweden’s Lund University conducted an experiment that showed this surprising result. Imagine a room with a lot of artificial flowers in it, and the only ones with yummy sugar water in them are yellow or blue. Next, Kelber’s team dimmed the lights to see how far they could go before the moths would start looking at random through the artificial flowers–in other words, before the moths couldn’t tell what was colored and what wasn’t.

Surprisingly, they were able to go all the way down through the dimness of a starry night and still go right to the colored flowers. Darker yellow or lighter blue shades confused them a little, but none of the moths went towards the grey flowers. It’s really an impressive bit of evolution in action. While daylight creatures like you and me are stumbling around and banging into chairs, hawkmoths are choosing just the right shade of midnight blue.

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