h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I saw a rainbow around the last full moon. It was one of the coolest things I have ever seen. There was a white halo, then all the colors of the rainbow in a circle around the moon.
Probably got all those colors because of pollution....

The beautiful effect you saw is called a halo, rather than a rainbow, because it is made is a different way (though it is every bit was wonderful!)
In a rainbow the light bounces out of waterdrops and comes back toward you, separated into colours. That is why you should look *away* from the sun to see a rainbow.
A halo, on the other hand, is caused by sunlight shining *through* the drops (or more opten ice crystals), somewhat like a crystal chandelier. This makes a ring *around* the moon (or the sun).
The moon actually can make a rainbow like the sun's if conditions are just right (you'd see it looking like a rainbow and similarly located in the direction opposite the source, but usually the moonbow is too faint to see colour).
When the sun has halos there are particularly intense patches on either side, which can look like multiple suns in the sky at once. These lesser companions are called "sun dogs". An artistic friend of mine once made a beautiful picture showing what she imagined of the same effect for the moon, which she imagined as "moon cats"

An excellent source for information on this sort of thing is the lovely book "Light and Color in the Outdoors" by M.G.J. Minnaert.

Of course nothing as as good as keeping your eyes open to the beauty all around us! Salut Daria!

Thanks for the info!