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EPISODE
1831: "Blue Sun" observed in southern U.S.
August 13, 2020
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2 min
Ashburn
Virginia
The appearance of a blue sun is triggered by volcanic dust, smoke from forest fires, desert dust, smog and other forms of pollution. Wavelengths of visible light that are blue in color become scattered from the rays of the sun reflected off of smog, smoke, or ash particles. The phenomena are extremely rare because the particles suspended in the air scatter blue wavelengths only when they are of a particular size. Smoke, volcanic ash and smog often provide clouds that are gray in color, setting the perfect backdrop for blue light to scatter off the particles composing the cloud.
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Episodes