Ball lightning is a controversial phenomenon. For centuries, people have reported seeing glowing, electrically charged balls of light in the sky. Scientists, however, remain unable to explain the sightings or even verify that ball lightning exists. Experts disagree on whether even the photos are authentic.
The debatable existence of this nifty form of "unconventional plasma" hasn't stopped it from showing up in literature; it has made appearances in works ranging from The Adventures of Tintin to a Pynchon novel.