A blue moon is an additional full moon. Basically, a second full moon in a month. It can also be an extra full moon in a season.
How often does a blue moon occur? Every 2-3 years. The moon isn't actually blue. It can have a blue tint when certain particles from volcanic eruptions or fires are in the air. This is very rare.
There are many superstitions about a full moon:
- It evokes madness
- women are more likely to go into labor
- women are more fertile
- werewolves come out, etc...
At any rate, the moon evokes mystery, magic, and the fantastic. A moonrise is certainly magical. Instead of gold, it chases away the shadows with silver. In reality, the moon is always full. It's a matter of its orbit that lights up more or less of it.
So why does it affect tides? That has to do with its placement in orbit, which corresponds with how much of it is lit up.
I love taking photos of the moon, and I love including it in stories. One of the most memorable stories I've read about the moon was by Arthur C. Clarke: A Fall of Moon Dust. Do you have a favorite myth or story about the moon?