Lesson #30: Crepuscular Rays

Oooh! A visual aid.*

Crepuscular rays are rays of sunshine that seem to originate from a single point. The name comes from the Latin word crepusculum, meaning twilight, as they most often appear at dawn and dusk. In order for crepuscular rays to exist, two things must be present; there must be something present to block out the source of light, such as a tree or clouds and there must be something in the air which scatters the light, such as dust or rain. Crepuscular rays are near parallel, but our own perspective makes them appear to diverge.** Completely unscientifically, they’re also very pretty.

*Please don’t steal my picture. That would make me sad. I would put a watermark on it, but I don’t know how. Any of my tech savvy friends want to help me with that? Oh, and if you’re interested, it was made off the Cliffs of Moher in County Clare, Ireland in July 2009 on a road trip with my old roomie from my undergraduate days.

**For a very scientific explanation, including the physics of perspective, see here (go on, you know you want to). For a very non-scientific explanation, see here.

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