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Sky lights.


Is this town in Idaho the site of an alien invasion? These" strange light beams aren't extraterrestrial; they are actually a phenomenon caused by cold, moist weather.

The source of the colorful columns, called light pillars, is millions of flat ice crystals hovering in the air nearly parallel to the ground. Light rays shining up from the town's electric lights reflect off the crystals and back down to Earth. "The collection of all those reflections combines to make one bright streak of light," says Joseph Shaw, who studies optics (physical properties of light) at Montana State University.

The effect may look pretty, says Shaw, but it's an indicator of a bigger problem: light pollution, or excess artificial light that can reduce the visibility of the night sky,


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Title Annotation:PHYSICAL/LIGHT
Author:Crane, Cody
Publication:Science World
Article Type:Brief article
Geographic Code:1USA
Date:May 11, 2009
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