Every once in a while, you may look up toward the sun and see strange bright lights on either side of it. Or perhaps you'll be sitting in an aircraft, looking out the window at its shadow, and see a circle of light, like a halo below (known as glories). Or, if you're really adventurous, maybe you'll even be out on a midnight walk with a full moon lighting your way, and see what appears to be a rainbow encircling the moon.