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Crepuscular Rays – Reprise

11 Jul 2016, 07:01 UTC
Crepuscular Rays – Reprise
(200 words excerpt, click title or image to see full post)

Crepuscular rays are those “beams” of light (and shadow) that can often be seen at sunrise or sunset. It’s a beautiful effect that I’ve posted about before. See: Crepuscular Rays and Crepuscular Rays + Silver Linings. I caught the above display a few weeks ago and decided to share it. As I’ve often said … sometimes Sky Lights is more about pretty pictures.
For a display like this to happen, you obviously need a cloud partially covering the Sun. Irregularities in the shape of the cloud selectively allow or block sunlight creating the pattern of light and dark streaks. You also need some haze, humidity, or dust in the air to make the rays visible. You can’t really “see” light passing by unless there’s something in the air to scatter the light toward your eyes. It’s the same thing that happens with a laser pointer aimed into the sky at night — in really clear air it’s difficult to see the beam. But in “bad” air the beam is easily visible.
The divergence of the rays is an optical illusion caused by perspective. You get the same illusion with parallel train tracks that appear to converge in the distance. Given ...

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