Ball lightning is a rare atmospheric electrical phenomenon resulting in weird orbs of light that seem to float in the air for much longer than a regular lightning bolt. Scientists have very little data about it or insight into how it's caused, and some even question whether it exists at all. As previously mentioned on BB, a recent study by University of Innsbruck researchers suggests that as many as half of reported cases are actually hallucinations caused by regular lightning overloading the brain with magnetic fields. In their research, Joseph Peer and Alexander Kendl used a transcranial magnetic stimulator to blast the brain's visual cortex. From National Geographic:
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…
The researchers make a convincing argument that some ball lightning reports are spurred by hallucinations, said John Abrahamson, a chemist and ball lightning expert at the University of Canterbury in New Zealand who was not involved in the study.
But "I cannot believe that most of the images reported as ball lightning are due to this brain influence," Abrahamson said in an email.
For one thing, the colors of light seen by the subjects in the experiment were "white, gray, or in unsaturated colors." But ball lightning has been reported in a variety of colors, including orange, green, and blue, Abrahamson said.