The other day I received an email from Heather Crocker. She was at her cottage in Malagash, N.S., when she looked up and saw what she described as rays coming up from the water. She was familiar with the rays that streak down from the sun, but this was new to her. She wanted to know what caused the upside-down effect.
Well Heather, both are examples of crepuscular rays.
The beams of sunlight that appear to burst from behind a cumulus cloud or shine down through a hole in the clouds are surprisingly the less common of the two.
When the sun is high in the sky, the shafts of light radiate down towards Earth. They appear when the path of sunlight is made visible by water droplets in the air – too scarce to appear as clouds but plentiful enough to noticeably scatter the light.
Crepuscular rays beaming up from the horizon are more common. They appear as pillars of sunlight, all converging at a single point, streaming upward. They’re most common during twilight hours when the contrasts between light and dark are the most obvious and that’s where they get their name.
If you happen to notice the crepuscular rays, turn around so your back is facing the sun. There, ahead of you, should be the anticrepuscular rays. These rays also converge toward a point but directly opposite the sun. That point is known as the antisolar point.
While these shafts of light appear to be converging toward the sun or the source of light, the rays are in fact almost parallel shafts of sunlight. The apparent convergence is a perspective effect.
The word crepuscular comes from the Latin “crepusculum,” meaning twilight. But I prefer their common name: God’s Fingers.
Cindy Day is the chief meteorologist for SaltWire Network.
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