By Hamish Johnston
Ball lightning is a phenomenon in which a fiery sphere floats through the air near the surface of the Earth, usually during a thunderstorm. Or is it?
Although ball lightning is very rare, researchers have collected thousands of eyewitness observations from around the world, and there are even a few photographs of the fiery apparitions. While some researchers have been able to create glowing orbs in the lab, physicists haven’t really been able to explain why they occur in nature.
Well, maybe that’s because ball lightning exists in the brain of the beholder – at least some of the time.
That’s the conclusion of a report recently posted on the arXiv preprint server by Alexander Kendl and Joseph Peer at the University of Innsbruck. They argue that electromagnetic pulses emitted by lightning discharges could lead to the perception of “magnetophosphenes” by persons nearby.
Magnetophosphenes are luminous shapes that are perceived by people undergoing transcranial magnetic stimulation (TMS) – a technique used to stimulate brain activity using magnetic pulses.
Kendl and Peer have calculated that a person up to 100 m away from long-duration (1–2 s) repetitive lightning discharges would receive about the same dose as a TMS subject.
Although they admit that such lightning events are rare, they claim, “Lightning electromagnetic pulse induced transcranial magnetic stimulation of phosphenes in the visual cortex is concluded to be a plausible interpretation of a large class of reports on luminous perceptions during thunderstorms.”