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For hundreds of years, people have reported seeing ball lighning, a weird phenomenon that resembles glowing, hovering spheres of electricity sometimes witnessed during lightning storms. But scientists have never been able to explain what causes it or even what it really is. Even though some surveys say that 1 in 150 people have seen ball lightening, photographic evidence is basically nonexistent. There are dozens of theories of how ball lightning could form, including the burning of hot silicon particles produced when a lightning strike vaporizes the ground. When people who claim they have seen ball lightining try to explain what they saw, often they are told, “You must be seeing things!”
Perhaps they are.
A pair of physicists from Austria say that the magnetic fields associated with certain types of lightning strikes are powerful enough to create hallucinations of hovering balls of light in nearby observers, and that these visions would be interpreted as ball lightning.
Alexander Kendl and Joseph Peer from the University of Innsbruck analyzed electromagnetic pulses of repetitive lightning discharges and compared them to the magnetic fields used in clinical transcranial magnetic stimulation (TMS), which is a technique used by neuroscientists to explore the workings of the brain; it is also used for psychiatric treatments. Patients are subjected to a rapidly changing magnetic field that is powerful enough to induce currents in neurons in the brain. Patients will sometimes see hallucinations of luminous shapes in their visual field.
Rare but natural long (1-2 seconds) and repetitive lightning strikes produce electromagnetic pulses similar to what happens during TMS. The researchers calculated the time-varying electromagnetic fields of various types of lightning strikes for observers at various distances from the strike, from 20-100 meters away.
Their results suggest the variable magnetic fields produced by lightning are very similar to TMS, in both magnitude and frequency. Those people undergoing TMS have hallucinations, and see balls of light known as cranial phosphenes.
Kendl and Peer postulated that ball lightning could be hallucinations arising from lightning electromagnetic pulses affecting the brains of close observers.
“As a conservative estimate, roughly 1% of (otherwise unharmed) close lightning experiencers are likely to perceive transcranially induced above-threshold cortical stimuli,” said Peer and Kendl in their paper. They add that these observers need not be outside but could be otherwise safely inside buildings or even sitting in aircraft.
The calculations showed that only lightning strikes consisting of multiple return strokes at the same point over a period of seconds could produce a magnetic field long enough to cause cortical phosphenes. This type would account for around 1-5% of lightning strikes, but very few of these would be seen by an observer 20 to 100 meters away, and of those the researchers estimate seeing the light for seconds would occur only in about one percent of unharmed observers. The observer does not need to be outside, but could be inside an aircraft or building. Kendl and Peer also said an observer would be most likely to classify the experience as ball lightning because of preconceptions.
One of the earliest descriptions of ball lighting comes from way back in 1638 at a church in Widecombe-in-the-Moor, Devon, in England. Four people died and approximately 60 were injured when, during a severe storm, an 8-foot (2.4 m) ball of fire was described as striking and entering the church, nearly destroying it. Large stones from the church walls were hurled into the ground and through large wooden beams. The ball of fire allegedly smashed the pews and many windows, and filled the church with a foul sulfurous odor and dark, thick smoke.
That doesn’t sound like a hallucination, but many question whether the reports are accurate or not. Read some more reports of ball lighting at Wikipedia.
Have you seen ball lightning, or know someone who has?
Sources: PhysOrg, Technology Review Blog