Crepuscular Rays

July 09, 2001


Provided by: Jim Foster, NASA/GSFC
Summary authors & editors: Jim Foster

On the above photo, taken early last month in northeastern Maryland, faint crepuscular rays (twilight rays) can be seen emanating from the western horizon a few minutes after susnset. Strato-cumulus clouds, just below the horizon, block some of the sunlight, but gaps in the clouds allow sunbeams to partially illuminate the cloud deck overhead. The result is a fan shaped pattern of alternating light snd shadows. Although the rays are actually parallel, they appear to diverge from our perspective - similar to standing on railroad tracks and looking at the tracks convege in the distance. See the Earth Science Picture of the Day for October 13, 2000 (anticrepuscular rays).

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