Patricia Cooper, age 13, of Dayton, Ohio, for her question:

WHAT IS LUMINESCENCE?

Luminescence is the emission of light by means other than heat.

Some butterflies give off a visible glow often called cold light. This is a type of luminescence, as is the glow caused when certain substances are exposed to cathode rays or X rays.

Luminescence that continues only as long as the radiation is applied is called fluorescence. In a fluorescent lamp, invisible ultraviolet rays bombard a phosphor coating to produce light.

Luminescence that lasts after the radiation is removed is called t phosphorescence. Many minerals are phosphorescent. The light given off by a butterfly and certain fungi is called bioluminescence.