Ball lightning

Ball lightning is an unexplained phenomenon described as luminescent, spherical objects that vary from pea-sized to several meters in diameter. Though usually associated with thunderstorms, ball lightnings are said to last considerably longer than the split-second flash of a lightning bolt, and are a distinct phenomenon from St. Elmo's fire.
Some 19th-century reports describe balls that eventually explode and leave behind an odor of sulfur. Descriptions of ball lightning appear in a variety of accounts over the centuries and have received attention from scientists. An optical spectrum of what appears to have been a ball-lightning event was published in January 2014 and included a video at high frame rate. Laboratory experiments have produced effects that are visually similar to reports of ball lightning, but how these relate to the supposed phenomenon remains unclear.
Scientists have proposed a number of hypotheses to explain reports of ball lightning over the centuries, but scientific data on ball lightning remains scarce. The presumption of its existence has depended on reported public sightings, which have produced inconsistent findings. Owing to the lack of reproducible data, the existence of ball lightning as a physical phenomenon remains unproven.
Historical accounts.
Ball lightning has been suggested as the possible source of legends that describe luminous balls, such as the mythological Anchimayen from Argentinean and Chilean Mapuche culture.
According to statistical investigations in 1960, ball lightning had been seen by 5% of the population of the Earth. Another study analyzed reports of 10,000 cases.
Great Thunderstorm of Widecombe-in-the-Moor.
One early account reports the Great Thunderstorm at a church in Widecombe-in-the-Moor, Devon, in England, on 21 October 1638. Four people died and approximately 60 were injured when, during a severe storm, an ball of fire was described as striking and entering the church, nearly destroying it. Large stones from the church walls were hurled onto 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 sulphurous odour and dark, thick smoke.
The ball of fire reportedly divided into two segments, one exiting through a window by smashing it open, the other disappearing somewhere inside the church. Because of the fire and sulphur smell, contemporaries explained the ball of fire as "the devil" or as the "flames of hell". Later, some blamed the entire incident on two people who had been playing cards in the pew during the sermon, thereby incurring God's wrath.
The "Catherine and Mary".
In December 1726, a number of British newspapers printed an extract of a letter from John Howell of the sloop "Catherine and Mary":
The "Montague".
One particularly large example was reported "on the authority of Dr. Gregory" in 1749:
Admiral Chambers on board the "Montague", 4 November 1749, was taking an observation just before noon...he observed a large ball of blue fire about distant from them. They immediately lowered their topsails, but it came up so fast upon them, that, before they could raise the main tack, they observed the ball rise almost perpendicularly, and not above from the main chains when it went off with an explosion, as great as if a hundred cannons had been discharged at the same time, leaving behind it a strong sulphurous smell. By this explosion the main top-mast was shattered into pieces and the main mast went down to the keel.
Five men were knocked down and one of them very bruised. Just before the explosion, the ball seemed to be the size of a large mill-stone.
Georg Richmann.
A 1753 report recounts lethal ball lightning when professor Georg Richmann of Saint Petersburg, Russia, constructed a kite-flying apparatus similar to Benjamin Franklin's proposal a year earlier. Richmann was attending a meeting of the Academy of Sciences when he heard thunder and ran home with his engraver to capture the event for posterity. While the experiment was under way, ball lightning appeared, travelled down the string, struck Richmann's forehead and killed him. The ball had left a red spot on Richmann's forehead, his shoes were blown open, and his clothing was singed. His engraver was knocked unconscious. The door-frame of the room was split and the door was torn from its hinges.
HMS "Warren Hastings".
An English journal reported that during an 1809 storm, three "balls of fire" appeared and "attacked" the British ship "HMS Warren Hastings". The crew watched one ball descend, killing a man on deck and setting the main mast on fire. A crewman went out to retrieve the fallen body and was struck by a second ball, which knocked him back and left him with mild burns. A third man was killed by contact with the third ball. Crew members reported a persistent, sickening sulphur smell afterward.
Ebenezer Cobham Brewer.
Ebenezer Cobham Brewer, in his 1864 US edition of "A Guide to the Scientific Knowledge of Things Familiar", discusses "globular lightning". He describes it as slow-moving balls of fire or explosive gas that sometimes fall to the earth or run along the ground during a thunderstorm. He said that the balls sometimes split into smaller balls and may explode "like a cannon".
Wilfrid de Fonvielle.
In his book "Thunder and Lightning", translated into English in 1875, French science-writer Wilfrid de Fonvielle wrote that there had been about 150 reports of globular lightning:
Globular lightning seems to be particularly attracted to metals; thus it will seek the railings of balconies, or else water or gas pipes etc, It has no peculiar tint of its own but will appear of any colour as the case may be ... at Coethen in the Duchy of Anhalt it appeared green. M. Colon, Vice-President of the Geological Society of Paris, saw a ball of lightning descend slowly from the sky along the bark of a poplar tree; as soon as it touched the earth it bounced up again, and disappeared without exploding. On 10th of September 1845 a ball of lightning entered the kitchen of a house in the village of Salagnac in the valley of Correze. This ball rolled across without doing any harm to two women and a young man who were here; but on getting into an adjoining stable it exploded and killed a pig which happened to be shut up there, and which, knowing nothing about the wonders of thunder and lightning, dared to smell it in the most rude and unbecoming manner.
The motion of such balls is far from being very rapid – they have even been observed occasionally to pause in their course, but they are not the less destructive for all that. A ball of lightning which entered the church of Stralsund, on exploding, projected a number of balls which exploded in their turn like shells.
Tsar Nicholas II.
Tsar Nicholas II, the last Emperor of Russia, reported witnessing what he called "a fiery ball" while in the company of his grandfather, Emperor Alexander II: Once my parents were away, and I was at the all-night vigil with my grandfather in the small church in Alexandria. During the service there was a powerful thunderstorm, streaks of lightning flashed one after the other, and it seemed as if the peals of thunder would shake even the church and the whole world to its foundations. Suddenly it became quite dark, a blast of wind from the open door blew out the flame of the candles which were lit in front of the iconostasis, there was a long clap of thunder, louder than before, and I suddenly saw a fiery ball flying from the window straight towards the head of the Emperor. The ball (it was of lightning) whirled around the floor, then passed the chandelier and flew out through the door into the park. My heart froze, I glanced at my grandfather – his face was completely calm. He crossed himself just as calmly as he had when the fiery ball had flown near us, and I felt that it was unseemly and not courageous to be frightened as I was. I felt that one had only to look at what was happening and believe in the mercy of God, as he, my grandfather, did. After the ball had passed through the whole church, and suddenly gone out through the door, I again looked at my grandfather. A faint smile was on his face, and he nodded his head at me. My panic disappeared, and from that time I had no more fear of storms.
Aleister Crowley.
British occultist Aleister Crowley reported witnessing what he referred to as "globular electricity" during a thunderstorm on Lake Pasquaney in New Hampshire, United States, in 1916. He was sheltered in a small cottage when he, in his own words, ...noticed, with what I can only describe as calm amazement, that a dazzling globe of electric fire, apparently between in diameter, was stationary about below and to the right of my right knee. As I looked at it, it exploded with a sharp report quite impossible to confuse with the continuous turmoil of the lightning, thunder and hail, or that of the lashed water and smashed wood which was creating a pandemonium outside the cottage. I felt a very slight shock in the middle of my right hand, which was closer to the globe than any other part of my body.
R. C. Jennison.
Jennison, of the Electronics Laboratory at the University of Kent, described his own observation of ball lightning in an article published in "Nature" in 1969:
I was seated near the front of the passenger cabin of an all-metal airliner (Eastern Airlines Flight EA 539) on a late night flight from New York to Washington. The aircraft encountered an electrical storm during which it was enveloped in a sudden bright and loud electrical discharge (0005 h EST, March 19, 1963). Some seconds after this a glowing sphere a little more than in diameter emerged from the pilot's cabin and passed down the aisle of the aircraft approximately from me, maintaining the same height and course for the whole distance over which it could be observed. 
Characteristics.
Descriptions of ball lightning vary widely. It has been described as moving up and down, sideways or in unpredictable trajectories, hovering and moving with or against the wind; attracted to, unaffected by, or repelled from buildings, people, cars and other objects. Some accounts describe it as moving through solid masses of wood or metal without effect, while others describe it as destructive and melting or burning those substances. Its appearance has also been linked to power lines, altitudes of and higher, and during thunderstorms and calm weather. Ball lightning has been described as transparent, translucent, multicolored, evenly lit, radiating flames, filaments or sparks, with shapes that vary between spheres, ovals, tear-drops, rods, or disks.
Ball lightning is often erroneously identified as St. Elmo's fire. They are separate and distinct phenomena.
The balls have been reported to disperse in many different ways, such as suddenly vanishing, gradually dissipating, being absorbed into an object, "popping," exploding loudly, or even exploding with force, which is sometimes reported as damaging. Accounts also vary on their alleged danger to humans, from lethal to harmless.
A review of the available literature published in 1972 identified the properties of a "typical" ball lightning, whilst cautioning against over-reliance on eye-witness accounts:
Direct measurements of natural ball lightning.
In January 2014, scientists from Northwest Normal University in Lanzhou, China, published the results of recordings made in July 2012 of the optical spectrum of what was thought to be natural ball lightning made by chance during the study of ordinary cloud–ground lightning on the Tibetan Plateau. At a distance of , a total of 1.64 seconds of digital video of the ball lightning and its spectrum was made, from the formation of the ball lightning after the ordinary lightning struck the ground, up to the optical decay of the phenomenon. Additional video was recorded by a high-speed (3000 frames/sec) camera, which captured only the last 0.78 seconds of the event, due to its limited recording capacity. Both cameras were equipped with slitless spectrographs. The researchers detected emission lines of neutral atomic silicon, calcium, iron, nitrogen, and oxygen—in contrast with mainly ionized nitrogen emission lines in the spectrum of the parent lightning. The ball lightning traveled horizontally across the video frame at an average speed equivalent of . It had a diameter of and covered a distance of about within those 1.64 s.
Oscillations in the light intensity and in the oxygen and nitrogen emission at a frequency of 100 hertz, possibly caused by the electromagnetic field of the 50 Hz high-voltage power transmission line in the vicinity, were observed. From the spectrum, the temperature of the ball lightning was assessed as being lower than the temperature of the parent lightning (<15,000 to 30,000 K). The observed data are consistent with vaporization of soil as well as with ball lightning's sensitivity to electric fields.
Laboratory experiments.
Scientists have long attempted to produce ball lightning in laboratory experiments. While some experiments have produced effects that are visually similar to reports of natural ball lightning, it has not yet been determined whether there is any relation.
Nikola Tesla reportedly could artificially produce balls and conducted some demonstrations of his ability, but he was truly interested in higher voltages and powers, and remote transmission of power, so the balls he made were just a curiosity.
The International Committee on Ball Lightning (ICBL) held regular symposia on the subject. A related group uses the generic name "Unconventional Plasmas". The last ICBL symposium was tentatively scheduled for July 2012 in San Marcos, Texas but was cancelled due to a lack of submitted abstracts.
Wave-guided microwaves.
Ohtsuki and Ofuruton described producing "plasma fireballs" by microwave interference within an air-filled cylindrical cavity fed by a rectangular waveguide using a 2.45 GHz, 5 kW (maximum power) microwave oscillator.
Water discharge experiments.
Some scientific groups, including the Max Planck Institute, have reportedly produced a ball lightning-type effect by discharging a high-voltage capacitor in a tank of water.
Home microwave oven experiments.
Many modern experiments involve using a microwave oven to produce small rising glowing balls, often referred to as "plasma balls".
Generally, the experiments are conducted by placing a lit or recently extinguished match or other small object in a microwave oven. The burnt portion of the object flares up into a large ball of fire, while "plasma balls" float near the oven chamber ceiling. Some experiments describe covering the match with an inverted glass jar, which contains both the flame and the balls so that they don't damage the chamber walls. (A glass jar, however, eventually explodes rather than simply causing charred paint or melting metal, as happens to the inside of a microwave.) Experiments by Eli Jerby and Vladimir Dikhtyar in Israel revealed that microwave plasma balls are made up of nanoparticles with an average radius of . The Israeli team demonstrated the phenomenon with copper, salts, water and carbon.
Silicon experiments.
Experiments in 2007 involved shocking silicon wafers with electricity, which vaporizes the silicon and induces oxidation in the vapors. The visual effect can be described as small glowing, sparkling orbs that roll around a surface. Two Brazilian scientists, Antonio Pavão and Gerson Paiva of the Federal University of Pernambuco have reportedly consistently made small long-lasting balls using this method. These experiments stemmed from the theory that ball lightning is actually oxidized silicon vapors "(see vaporized silicon hypothesis, below)".
Proposed scientific explanations.
There is at present no widely accepted explanation for ball lightning. Several hypotheses have been advanced since the phenomenon was brought into the scientific realm by the English physician and electrical researcher William Snow Harris in 1843, and French Academy scientist François Arago in 1855.
Vaporized silicon hypothesis.
This hypothesis suggests that ball lightning consists of vaporized silicon burning through oxidation. Lightning striking Earth's soil could vaporize the silica contained within it, and somehow separate the oxygen from the silicon dioxide, turning it into pure silicon vapor. As it cools, the silicon could condense into a floating aerosol, bound by its charge, glowing due to the heat of silicon recombining with oxygen. An experimental investigation of this effect, published in 2007, reported producing "luminous balls with lifetime in the order of seconds" by evaporating pure silicon with an electric arc. Videos and spectrographs of this experiment have been made available. This hypothesis got significant supportive data in 2014, when the first ever recorded spectra of natural ball lightning were published. The theorized forms of silicon storage in soil include nanoparticles of Si, SiO, and SiC.
Matthew Francis has dubbed this the "dirt clod hypothesis", in which the spectrum of ball lightning shows that it shares chemistry with soil.
Electrically charged solid-core model.
In this model ball lightning is assumed to have a solid, positively charged core. According to this underlying assumption, the core is surrounded by a thin electron layer with a charge nearly equal in magnitude to that of the core. A vacuum exists between the core and the electron layer containing an intense electromagnetic (EM) field, which is reflected and guided by the electron layer. The microwave EM field applies a ponderomotive force (radiation pressure) to the electrons preventing them from falling into the core.
Microwave cavity hypothesis.
Pyotr Kapitsa proposed that ball lightning is a glow discharge driven by microwave radiation that is guided to the ball along lines of ionized air from lightning clouds where it is produced. The ball serves as a resonant microwave cavity, automatically adjusting its radius to the wavelength of the microwave radiation so that resonance is maintained.
The Handel Maser-Soliton theory of ball lightning hypothesizes that the energy source generating the ball lightning is a large (several cubic kilometers) atmospheric maser. The ball lightning appears as a plasma caviton at the antinodal plane of the microwave radiation from the maser.
In 2017, Researchers from Zhejiang University in Hangzhou, China, have proposed that the bright glow of lightning balls is created when microwaves become trapped inside a plasma bubble. At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced when in contact with microwave radiation.
 The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. Microwaves trapped inside the ball continue to generate plasma for a moment to maintain the bright flashes described in observer accounts. The ball eventually fades as the radiation held within the bubble starts to decay and microwaves are discharged from the sphere. The lightning balls can dramatically explode as the structure destabilizes. The theory could explain many of the strange characteristics of ball lightning. For instance, microwaves are able to pass through glass, which helps to explain why balls could be formed indoors.
Soliton hypothesis.
Julio Rubinstein, David Finkelstein, and James R. Powell proposed that ball lightning is a detached St. Elmo's fire (1964–1970). St. Elmo's fire arises when a sharp conductor, such as a ship's mast, amplifies the atmospheric electric field to breakdown. For a globe the amplification factor is 3. A free ball of ionized air can amplify the ambient field this much by its own conductivity. When this maintains the ionization, the ball is then a soliton in the flow of atmospheric electricity.
Powell's kinetic theory calculation found that the ball size is set by the second Townsend coefficient (the mean free path of conduction electrons) near breakdown. Wandering glow discharges are found to occur within certain industrial microwave ovens and continue to glow for several seconds after power is shut off. Arcs drawn from high-power low-voltage microwave generators also are found to exhibit afterglow. Powell measured their spectra, and found that the after-glow comes mostly from metastable NO ions, which are long-lived at low temperatures. It occurred in air and in nitrous oxide, which possess such metastable ions, and not in atmospheres of argon, carbon dioxide, or helium, which do not.
The soliton model of a ball lightning was further developed. It was suggested that a ball lightning is based on spherically symmetric nonlinear oscillations of charged particles in plasma – the analogue of a spatial Langmuir soliton. These oscillations were described in both classical and quantum approaches. It was found that the most intense plasma oscillations occur in the central regions of a ball lightning. It is suggested that bound states of radially oscillating charged particles with oppositely oriented spins – the analogue of Cooper pairs – can appear inside a ball lightning. This phenomenon, in its turn, can lead to a superconducting phase in a ball lightning. The idea of the superconductivity in a ball lightning was considered earlier. The possibility of the existence of a ball lightning with a composite core was also discussed in this model.
Hydrodynamic vortex ring antisymmetry.
One theory that may account for the wide spectrum of observational evidence is the idea of combustion inside the low-velocity region of spherical vortex breakdown of a natural vortex (e.g., the 'Hill's spherical vortex').
Nanobattery hypothesis.
Oleg Meshcheryakov suggests that ball lightning is made of composite nano or submicrometer particles—each particle constituting a battery. A surface discharge shorts these batteries, causing a current that forms the ball. His model is described as an aerosol model that explains all the observable properties and processes of ball lightning.
Buoyant plasma hypothesis.
The declassified Project Condign report concludes that buoyant charged plasma formations similar to ball lightning are formed by novel physical, electrical, and magnetic phenomena, and that these charged plasmas are capable of being transported at enormous speeds under the influence and balance of electrical charges in the atmosphere. These plasmas appear to originate due to more than one set of weather and electrically charged conditions, the scientific rationale for which is incomplete or not fully understood. One suggestion is that meteors breaking up in the atmosphere and forming charged plasmas as opposed to burning completely or impacting as meteorites could explain some instances of the phenomena, in addition to other unknown atmospheric events.
Transcranial magnetic stimulation.
Cooray and Cooray (2008) stated that the features of hallucinations experienced by patients having epileptic seizures in the occipital lobe are similar to the observed features of ball lightning. The study also showed that the rapidly changing magnetic field of a close lightning flash is strong enough to excite the neurons in the brain. This strengthens the possibility of lightning-induced seizure in the occipital lobe of a person close to a lightning strike, establishing the connection between epileptic hallucination mimicking ball lightning and thunderstorms.
More recent research with transcranial magnetic stimulation has been shown to give the same hallucination results in the laboratory (termed magnetophosphenes), and these conditions have been shown to occur in nature near lightning strikes.
This hypothesis fails to explain observed physical damage caused by ball lightning or simultaneous observation by multiple witnesses. (At the very least, observations would differ substantially.)
Theoretical calculations from University of Innsbruck researchers suggest that the magnetic fields involved in certain types of lightning strikes could potentially induce visual hallucinations resembling ball lightning. Such fields, which are found within close distances to a point in which multiple lightning strikes have occurred over a few seconds, can directly cause the neurons in the visual cortex to fire, resulting in magnetophosphenes (magnetically induced visual hallucinations).
Rydberg matter concept.
Manykin et al. have suggested atmospheric Rydberg matter as an explanation of ball lightning phenomena. Rydberg matter is a condensed form of highly excited atoms in many aspects similar to electron-hole droplets in semiconductors. However, in contrast to electron-hole droplets, Rydberg matter has an extended life-time—as long as hours. This condensed excited state of matter is supported by experiments, mainly of a group led by Holmlid. It is similar to a liquid or solid state of matter with extremely low (gas-like) density. Lumps of atmospheric Rydberg matter can result from condensation of highly excited atoms that form by atmospheric electrical phenomena, mainly due to linear lightning. Stimulated decay of Rydberg matter clouds can, however, take the form of an avalanche, and so appear as an explosion.
Vacuum hypothesis.
Nikola Tesla (1899 December) theorized that the balls consist of highly rarefied (but hot) gas.
Other hypotheses.
Several other hypotheses have been proposed to explain ball lightning:
References.
Notes
Further reading