Ghostly Fire

"Microlightning" may power strange will-o'-the-wisps

- Rachel Nuwer

SOME CALL THEM WILL-O'-THE-WISPS; others call them ignis fatuus, Latin for "foolish fire." Whatever the name, for centuries people have reported seeing these eerie, faint blue flames hovering over marshes, bogs, and other wetlands.

Various cultures have interpreted the ephemeral aberrations as fairies, ghosts or spirits. Scientists have offered a different explanation: the lights form when methane and other gases from decaying material react with oxygen and briefly ignite, producing a flamelike glow.

But one big mystery remained. Although will-o'-the-wisps are not actual flames and occur at ambient temperatures, they still have to ignite somehow. The source of that ignition has been unknown to research.