Why does the moon sometimes appear dark red?

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by Evan Stewart

WVEC.com

Posted on March 16, 2010 at 5:42 PM

The moon can appear to be different colors due to the scattering of light by the atmosphere. When the moon is near the horizon, the moonlight has to pass through much more atmosphere than when the moon is directly overhead, since it is passing through at an angle. By the time the moonlight reaches your eyes, most of the shorter waves (green, blue, violet) of visible light have been scattered away by air molecules. You only see the longer wavelength colors of yellow, orange, or red.

Sometimes the moon appears different colors even when it's directly overhead. This occurs when there's a lot of dust, smoke, or pollution in the atmosphere. The size of those particles will determine the type of color you will see. Sometimes the moon will look red, orange...even blue.

The moon often appears dark red in our area when we have SW winds, which can put a lot more dirt particles in the air, producing a red color.

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