Many colorful atmospheric phenomena can be seen with the naked eye from the ground - for example, the common rainbow and the lesser-known sundog, which have both been the subject of previous Franklin Facts. There's one phenomenon, however, that can only be seen from a high altitude - such as from an airplane. It's called a "glory," and I witnessed one for the first time in my life last week.

A glory is a small, rainbow-colored circle that forms from the reflection of sunlight off a layer of clouds made of water drops. In the case of the glory, the water drops must be directly opposite the sun, basically where you'd see the shadow of your head. Since clouds don't regularly form so close to the ground, a glory isn't seen very often. But if you're in an airplane, flying above a layer of clouds, the shadow of the airplane on the clouds below marks the point directly opposite the sun. And that's where you can see a glory - a circular ring of colored light surrounding the plane's shadow.

Another way to see a glory is to be high on a mountain, just above a layer of fog or mist. When a climber's shadow on the clouds below is surrounded by a colored halo of light, the glory can take on a downright ghostly appearance. The apparition is called a "Spectre of the Brocken," so-named because of sightings on the Brocken, the highest peak of a mountain range in central Germany.