Photograph by Sarah Wise.
We chose this splendid picture from among several equally splendid shots in part because it shows clearly the origin of crepuscular rays – just look at the mountain peaks and valleys, especially on the right. The rays are the result of light scattering by the atmosphere. On the left, you can clearly see atmospheric scattering where one of the rays roughly bisects a cloud. And finally, you can see how every cloud has a silver lining.
Incidentally, I assume that crepuscular rays are the reason Moses has horns in Michelangelo’s sculpture of Moses: ray and horn are the same word in Biblical Hebrew, probably because the ancients simply called crepuscular rays “horns.” It seems likely to me that they envisioned Moses as having had (crepuscular) rays coming out of his head. Again incidentally, you may find other depictions of Moses with horns here. There is nothing new in the author’s premise that the word was mistranslated into Greek.