I love to get mail. Last month, Phil Thompson had a question about shafts of light coming from a cloud. Phil wanted to know where the shafts come from and why we don’t see the colours of the rainbow in them.
These brilliant beams of light are often seen extending from clouds early in the morning or late in the day. Some people refer to them as “God’s Rays,” but the phenomenon is properly known as crepuscular rays, since they occur during crepuscular hours.
Rays of light can change direction when they encounter small particles suspended in the atmosphere: this is called scattering. A cloud between you and the sun can block some, but not all of the sun’s light. Where the light peeks through, scattering illuminates its path from the sun to your eyes. This creates beams in the sky.
These beams appear to converge toward the sun, but that’s just an illusion. In fact, the rays are parallel. When you look down a railroad track, the tracks look like they converge off in the distance, but we know they remain parallel.
Crepuscular rays are not multi-coloured like a rainbow because light is being scattered by an object. Rainbows get their colour from light entering and bouncing off a drop of water or rain.
We’ve all see them! Now we know the science behind crepuscular rays. Thank you for asking, Phil!
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Cindy Day is the chief meteorologist for SaltWire Network.
