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Mysterious ball lightning may be brain illusion

May 19, 2010
Courtesy of the University of Innsbruck
and World Science staff

Researchers have de­vised a new ex­plana­t­ion for a pos­si­ble cause of ball light­ning, a mys­te­ri­ous phe­nom­e­non in which light­ning ap­par­ently forms in­to a glob­u­lar shape and starts float­ing around.

The na­ture of these seem­ing fire­balls has long been con­tro­ver­sial, with some sci­en­tists at­trib­ut­ing them to op­ti­cal il­lu­sions. The new the­o­ry pro­poses that a mag­net­ic field sur­round­ing long light­ning strikes may pro­duce the im­age of lu­mi­nous shapes, known as phos­phenes, in the brain. 

Re­search­ers have pro­duced fire­balls in the lab­o­ra­to­ry that bore a cer­tain re­sem­blance to ball light­ning. (Pho­to cour­te­sy U. of Inns­bruck)

Jo­sef Peer and Al­ex­an­der Kendl of the Uni­vers­ity of Inns­bruck, Aus­tria, stud­ied the el­ect­ro­mag­net­ic fields as­so­ci­at­ed with dif­fer­ent types of light­ning strikes. El­ec­t­ro­mag­net­ic fields are fields of force sur­round­ing charged ob­jects. These fields in­flu­ence both the both the mo­tions of oth­er, near­by charged ob­jects, and the ori­enta­t­ion of near­by mag­nets.

Peer and Kendl’s cal­cula­t­ions sug­gest the mag­net­ic fields of one type of light­ning show the same prop­er­ties as tran­scra­nial mag­net­ic stimula­t­ion, or TMS, a med­i­cal tech­nique used by psy­chi­a­trists to stim­u­late brain ac­ti­vity. A spe­cif­ic class of long-last­ing, re­pet­i­tive light­ning dis­charges pro­duce the si­m­i­lar ef­fect, ac­cord­ing to the phys­i­cists.

Time-var­y­ing and suf­fi­ciently strong mag­net­ic fields in­duce elec­tri­cal fields in cells of the brain’s vis­u­al cor­tex, the brain ar­ea that pro­cesses sight, they not­ed. This in turn may evoke phos­phenes.

“In the clin­i­cal ap­plica­t­ion of TMS, lu­mi­nous and ap­par­ently real vis­u­al per­cep­tions in var­y­ing shapes and col­ors with­in the vis­u­al field of the pa­tients and test per­sons are re­ported and well ex­am­ined,” said Kendl.

Kendl and Peer, whose find­ings are pub­lished in the jour­nal Phys­ics Let­ters A, cau­tioned that the ball light­ning mys­tery may not be solved yet. 

Ball light­nings are rath­er rare events, and the term “ball light­ning” may ac­tu­ally cov­er a few dif­fer­ent phe­nom­e­na, they not­ed. Var­i­ous the­o­ries for these ex­pe­ri­ences have been sug­gested. Some re­search­ers have pro­duced lu­mi­nous fire balls in the lab­o­r­a­to­ry, which ap­peared some­what like ball light­ning and could ex­plain some of the re­ports but were mostly too short lived.

The Amer­i­can Me­te­or­o­logical So­ci­e­ty Glos­sa­ry of Me­teorol­ogy de­fines ball light­ning as a “bright ball of light ob­served float­ing or mov­ing through the at­mos­phere close to the ground,” about 30-100 cm (12-40 inches) wide, typ­ic­ally “o­r­ange or red­dish... and last­ing for only a few sec­onds be­fore dis­ap­pear­ing, some­times with a loud noise. Most of­ten ball light­ning is seen in the vicin­ity of thun­der­storms or a re­cent light­ning strike, which may sug­gest that ball light­ning is elec­tri­cal in com­po­si­tion or ori­gin.”

Oth­er plau­si­ble ex­plana­t­ions for ball light­ning in­clude dust balls, small mol­ten balls of met­al or St. El­mo’s fire, a type of elec­tri­cal dis­charge from a point­ed ob­ject, ac­cord­ing to Kendl and Peer. How­ev­er, Kendl main­tains that his “phosphene” hy­poth­e­sis is a par­tic­u­larly sim­ple ex­plana­t­ion and could ex­plain the ma­jor­ity of cases.

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Scientists have devised a new explanation for the possible cause of ball lightning, a mysterious phenomenon in which lightning apparently forms into a globular shape and starts floating around. The nature of these seeming fireballs has long been controversial, with some researchers attributing them to optical illusions. The new theory proposes that a magnetic field surrounding long lightning strokes may produce the image of luminous shapes, known as phosphenes, in the brain. Josef Peer and Alexander Kendl of the University of Innsbruck, Austria, studied the electromagnetic fields associated with different types of lightning strikes. Electromagnetic fields are fields of force surrounding charged objects. These fields influence both the both the motions of other, nearby charged objects, and the orientation of nearby magnets. Peer and Kendl’s calculations suggest the magnetic fields of one type of lightning show the same properties as transcranial magnetic stimulation, or TMS, a medical technique used by psychiatrists to stimulate brain activity. A specific class of long-lasting, repetitive lightning discharges produce this similar effect, according to the physicists. Time-varying and sufficiently strong magnetic fields induce electrical fields in cells of the brain’s visual cortex, the brain area that processes sight, they noted. This in turn may evoke phosphenes. “In the clinical application of TMS, luminous and apparently real visual perceptions in varying shapes and colors within the visual field of the patients and test persons are reported and well examined,” said Kendl. Kendl and Peer, whose findings are published in the journal Physics Letters A, cautioned that the ball lightning mystery may not be solved yet. Ball lightnings are rather rare events, and the term “ball lightning” may actually cover a few different phenomena, they noted. Over time, various theories about the nature of these experiences have been suggested. Some researchers have produced luminous fire balls in the laboratory, which appeared somewhat like ball lightning and could explain some of the reports but were mostly too short lived. The American Meteorological Society Glossary of Meterology defines ball lightning as a “bright ball of light observed floating or moving through the atmosphere close to the ground,” about 30-100 cm (12-40 inches) wide, typically “orange or reddish in color, and lasting for only a few seconds before disappearing, sometimes with a loud noise. Most often ball lightning is seen in the vicinity of thunderstorms or a recent lightning strike, which may suggest that ball lightning is electrical in composition or origin.” Other plausible explanations for ball lightning include dust balls, small molten balls of metal or St. Elmo’s fire, a type of electrical discharge from a pointed object, according to Kendl and Peer. However, Kendl maintains that his “phosphene” hypothesis is a particularly simple explanation and could explain the majority of cases.