Atmospheric Phenomena

Rainbows and Other Colorful Phenomena

What is a crepuscular ray?

A less technical name for a crepuscular ray would be a sunbeam, such as can be seen when streams of sunlight emerge from behind a cloud during the twilight hours (“crepuscule” means “twilight”). In the Bible, they may have inspired the story of Jacob’s ladder (Genesis 28:11–19), and so they are often named after that story. Another descriptive phrase for crepuscular rays is “the Sun drawing water” because people once believed that the beams of light were actually formed by water being sucked up into the Sun. Because these rays are seen as clouds are breaking up, folklore rightfully interprets them as a sign that good weather will likely be ahead.

Crepuscular rays stream down like a like light beams during an Antarctic sunset. (photo by Dave Mobley, Jet Propulsion Laboratory, courtesy NOAA)

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