Earthbound Rainbow

July 11, 2003

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Provided by: Judy Mosby
Summary authors & editors: Les Cowley

Two things are odd about this "rainbow," it's on the ground, and its colors are weak and widely spaced. It was captured near Lovelock, Nevada at 4.21 p.m. Pacific Daylight Time on May 7, 2003. At that instant, the Sun was 39º high, and this explains the bow's position. Rainbows are circles of about 42º radius centered on a point directly opposite the Sun. Thus the bow's center was 39º below the horizon, and so the top stood up just 3º above it. The colors? Ordinary rainbows are produced by refraction and reflection of light through large raindrops. Much smaller mist droplets at the base of the mountains formed this bow. Light interference effects in the small droplets broaden the bow and dilute the colors to produce a cloud bow, or when the droplets are very small, an almost white fog bow.

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