Friday, February 20, 2009

Mysterious Light Pillars

From: Kevin@Free Democracy
February 18, 2009--Light pillars scrape the night sky over Victor, Idaho, on January 26. Typically seen in polar regions, the vertical columns of light have been appearing along with frigid temperatures at lower latitudes this winter.
Explanatory diagram for light pillars
Light pillars appear when artificial light (shown in diagram above) or natural light bounces off the facets of flat ice crystals wafting relatively close to the ground. When the light source is close to the ground, the light pillar appears above the floating crystals. When the light comes from the sun or moon, the light pillar can appear beneath them, too, as the light refracts through the crystals. (See a picture of another ice-crystal light phenomenon, a sun dog.)

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