I was having a discussion with some of my students yesterday about black holes, the speed of light, and astronomy in general, and I thought of something rather interesting that might be helpful in fantasy and sci-fi world building.
Because of the speed of light, and the distances of the sun, moon, and earth from one another, the light we receive from the sun is said to be light that left the sun thousands of years before we actually see it. Now, if you give those times some astrological or astronomical significance (perhaps light carries information that the sun is intentionally sending us, or the light of the sun and stars somehow plays into events that occur whether personally or ecologically), then eclipses are a break in that cycle. Either it is an intentional break in the communication--for protection or for harm--or it is a natural disaster that causes disaster as well as rejuvenation for the world it affects.
This might play into the origin of werewolves or mess up their natural transformation cycle. It might be a complex sort of Morse code from other beings, or it might be static on the radio. And that is just the sun.

The possibilities go on and on.