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The science behind desert mirages

A mirage seen in central Phoenix. (Source: Royal Norman)
A mirage seen in central Phoenix. (Source: Royal Norman)(Royal Norman)

I’m not sure how old I was when I saw my first mirage.

But I do remember it was on one of our road trips. We saw a lot of America when I was young, from the Statue of Liberty to Mt. Rushmore to Yosemite National Park. We grew up in the Chicago area so that means we were in the car for a long time each summer.

A mirage seen on a highway. (Source: Andy Smarik)
A mirage seen on a highway. (Source: Andy Smarik)(Andy Smarik)

On one of those trips, between counting trucks, playing “Hearts” with my brother and sister and asking if we were going to stay at a motel with a pool, I got fascinated with the mirages ahead of us on the road. Dad explained what they were but I was sure if he went just a little faster, we’d catch up to one of them and it would prove to be water. It just looked SO real. Such were the delusions of my youth.

A mirage seen on Seventh Avenue. (Source: Royal Norman)
A mirage seen on Seventh Avenue. (Source: Royal Norman)(Royal Norman)

Mirages are so common around Arizona I bet we mostly don’t notice them so much. The science behind mirages is interesting, complicated and involves how our brains perceive things. But here’s one of the best descriptions I’ve read from Planet-Science.Com.Mirages happen when the ground is very hot and the air is cool. The hot ground warms a layer of air just above the ground. When the light moves through the cold air and into the layer of hot air it is refracted (bent). A layer of very warm air near the ground refracts the light from the sky nearly into a U-shaped bend. Our brain thinks the light has traveled in a straight line. Our brain doesn’t see the image as bent light from the sky. Instead, our brain thinks the light must have come from something on the ground.” Like I said, Dad. Speed up. We’ll get to that water yet.”

A huge mirage seen with a shuttle at Edwards AFB. (NASA-Ctien)
A huge mirage seen with a shuttle at Edwards AFB. (NASA-Ctien)(NASA-Ctien)