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It Is Offical – Leprechauns Are Lost.

September 18, 2008

Interesting, right?

But this is no fantasy or trick of the light, it is known as a circumzenithal arc. Seen here shimmering in the sky over Cambridge in the afternoon sunshine, it is often mistaken for a rainbow hanging upside down. But unlike a rainbow, the sky has to be clear of rain and low level clouds for it to be seen. Relatively rare in Britain, the arc only appears when sunlight shines at a specific angle through a thin veil of wispy clouds at a height of around 20,000 to 25,000 feet. At this altitude the cirrus clouds are made of ice crystals, the size of grains of salt. Meteorologists say the clouds must be convex to the sun with the ice particles lined up together in the right direction to refract the light. This results in the sunlight bouncing off the ice crystals high in the atmosphere, sending the light rays back up and bending the sunlight like a glass prism into a spectrum of colour.

Pictured: Rare upside-down rainbow spotted in the UK | Mail Online.

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