Mystery lights is just one of many terms used to refer to various types of lights that to some people seem to appear and disappear for no apparent reason. Some of these lights reportedly wink on and off, but others are said to flit about, hover, or move across the ground, in the sky, beneath the sea, or within caves. Still others seem to follow people about, or otherwise appear to be guided by an intelligent force. Some mystery lights are a faint glow, but one type, known as ball lightning, seems to be a ball of fire and can explode when touched.
Mystery lights that appear high in the atmosphere are often called unidentified flying objects (UFOs) and are thought to be alien spacecraft. Sceptics, however, say that these lights are actually either associated with ordinary aircraft or are attributable to optical illusions. In fact, sceptics believe that most mystery lights are optical illusions. Those few that cannot be explained in this way, they argue, are caused by natural phenomena. For example, they suggest that mystery lights appearing over swamps are caused by gases—produced by decaying plant matter—that ignite after being released into the air.
The Greenhaven Encyclopedia of Paranormal Phenomena – written by Patricia D. Netzley © 2006 Gale, a part of Cengage Learning