Under the Sun
4:46 pm
Wed August 24, 2011

Green Flashes, Rainbows And Other Atmospheric Mirages

Have you ever seen a green flash? It is said to happen as the sun dips below the horizon, creating an elusive green light that appears in the sky for a fleeting moment and then disappears. Many people believe the green flash is a myth, repeated for the benefit of tourists. Others swear by its existence. So is it real? If so, what causes it? Under the Sun reporter Sammy Mack – a skeptic when it comes to the green flash – headed to Key West to investigate this phenomenon. She began her search for the truth at Mallory Square, where hundreds of locals and tourists gather every night to watch the sunset. She ran into a couple who claimed to have seen several green flashes and had the evidence to prove it on their cell phone. A guy selling conch fritters said he had witnessed the green flash as well, but attributed it to atmospheric science.

And he was right, according to Patrick Meyers, a scientist at the Rosenstiel School of Marine and Atmospheric Studies at the University of Miami in Virginia Key. Patrick says the green flash is a mirage similar to a rainbow. It is caused by refraction, which occurs when light passes through different objects and bends like a prism.

Conditions have to be just right for a green flash to occur. The water must be warmer than the air and the position of the sun in relation to the horizon has to be at a specific point. Odds of meeting these conditions are slim, but Key West is one of your best bets for witnessing this atmospheric phenomenon.