Ball Lightning May Be All in Your Head

For hundreds of years eyewitnesses have reported brief encounters with the golf ball- to tennis ball-size orbs of electricity. But scientists have been unable to agree on how and why ball lightning forms, since the phenomenon is rare and very short-lived. (See "Ball Lightning: A Shocking Scientific Mystery.")

Ball lightning is often reported during thunderstorms, and it's known that multiple consecutive lightning strikes can create strong magnetic fields. So Joseph Peer and Alexander Kendl at the University of Innsbruck in Austria wondered whether ball lightning is really a hallucination induced by magnetic stimulation of the brain's visual cortex or the eye's retina.

In previous experiments, other scientists had exposed humans to strong, rapidly changing magnetic fields using a medical machine called a transcranial magnetic stimulator, or TMS. The machine's magnetic fields are powerful enough to induce electric currents in human brain cells without being harmful.

Focusing magnetic fields on the visual cortex of the brain caused the subjects to see luminous discs and lines. When the focus was moved around within the visual cortex, the subjects reported seeing the lights move.

In their paper, which appeared online May 7 on the physics research website arXiv.org, Peer and Kendl argue that magnetic fields made by lightning could have the same effect as TMS machines on nearby humans.

In fact, the pair thinks about half of all ball lightning reports are actually tricks of the mind induced by magnetism.