Rare rainbow spotted over Idaho

June 20, 2006


A rare rainbow known as a circumhorizontal arc was spotted over Idaho on June 3rd. The arc isn't a traditional rainbow, but rather caused by light passing through wispy, high-altitude cirrus clouds, and only occurs when the sun is very high in the sky - more than 58 degrees above the horizon. Additionally, the hexagonal ice crystals that make up the cirrus clouds must be shaped like thick plates with their faces parallel to the ground, so that light enters through the vertical face of the ice crystal and leaves from the bottom face; refracting the way light passing through a prism does.

So the next time you see a rainbow curse it for being a failure and not being as special as a circumhorizontal arc. And then express disappointment at how much it sucks at sports.

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