Friday, 9 November 2012

Hole-Punch Clouds

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You might be familiar with contrails, those wispy strands of clouds made by jet exhaust high in the sky. But you might never have seen a hole-punch cloud. They're very strange clearings in the cloud cover - clear patches of sky, often with a circular shape. Sometimes people report them as UFOs. Some thought airplanes created hole-punch clouds - but just how they did it was unclear.