Ball lightning
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Ball lightning is an optical phenomenon, whose physical nature is uncertain, characterized by luminence, a lifetime of several seconds, a compact shape, and a size roughly similar to that of a basketball. It is often associated with thunderstorms. There have been some reports of production of a similar phenomenon in the laboratory, but some still disagree on whether it is a real phenomenon.
Reports
Ball lightning discharges were once thought to be extremely rare occurrences, "At one time BL was thought to be extremely rare, but this was because most BL eyewitnesses feared ridicule and wouldn't come forward. In reality, five percent of the population has seen BL close up." [link] but recent research shows that a few percent of the US population have been witnesses.#redirect Surveys have been taken of eyewitness accounts by at least 3000 people.#redirect
Ball lightning is photographed very rarely, and details of witness accounts can vary widely. Many of the properties observed in ball lightning accounts conflict with each other, and it is very possible that several different phenomena are being incorrectly grouped together. It is also possible that some photos are fakes.
The discharges reportedly appear during thunderstorms, sometimes issuing from a lightning flash, but large numbers of encounters reportedly occur during good weather with no storms within hundreds of miles.
Ball lightning reportedly tends to float (or hover) in the air and take on a ball-like appearance. Its shape has been described as spherical, ovoid, teardrop, or rod-like with one dimension being much larger than the others. The longest dimension reported is between fifteen and forty centimeters. Many are red to yellow in color, sometimes transparent, and some contain radial filaments or sparks. Other colors, such as blue or white occur as well.
Sometimes the discharge is described as being attracted to a certain object, and sometimes as moving randomly. After several seconds the discharge reportedly leaves, disperses, is absorbed into something, or, rarely, vanishes in an explosion.
Ball lightning has been reported in places as diverse as "escorting" World War II bombers, flying alongside their wingtips. During this period, due to the enigmatic nature of this phenomenon, these appearances were referred to as "foo fighters." Other accounts place ball lightning as appearing over a kitchen stove to wandering down the aisle of an airliner. One report described ball lightning engulfing and following a car, causing the electrical supply to overload and fail.[[Citing sources citation needed]]
Historical and fictional accounts
One of the earliest reported, and most destructive, occurrences is said to have taken place during The Great Thunderstorm at Widecombe-in-the-Moor, Devon, in the United Kingdom, on October 21 1638. Four people died and around 60 were injured when what appears to have been ball lightning struck a church.[[Citing sources citation needed]]Another reference to ball lightning appears in a children's book set in the 1800s by Laura Ingalls Wilder. The books are considered historical fiction, but the author always insisted they were descriptive of actual events in her life. In Wilder's description, three seperate balls of lightning appear during a winter blizzard near a cast iron stove in the family's kitchen. They are described as appearing near the stovepipe, then rolling across the floor, only to disappear as the mother chases them with a willow-branch broom.
Notorious British occultist Aleister Crowley also reported witnessing what he referred to as "globular electricity" during a thunderstorm on Lake Pasquaney in New Hampshire in 1916. As related in his Confessions, he was sheltered in a small cottage when he "noticed, with what I can only describe as calm amazement, that a dazzling globe of electric fire, apparently between six and twelve inches in diameter, was stationary about six inches 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."
A famous anecdote from 1753 depicts ball lightning as having violent potential. Professor Georg Richmann, of Saint Petersburg, Russia created a kite flying apparatus similar to that built by Benjamin Franklin a year earlier. He was attending a meeting of the Academy of Sciences, when he heard thunder. The Professor ran home with his engraver to capture the event for posterity. While the experiment was underway, ball lightning appeared, collided with Richmann's head and killed him, leaving a red spot. His shoes were blown open, parts of his clothes singed, the engraver knocked out; the doorframe of the room was split, and the door itself torn off its hinges."Frenchman Thomas Francois D'Alibard used a 50-foot long vertical rod to draw down the "electric fluid" of the lightning in Paris on May 10, 1752. One week later, M. Delor repeated the experiment in Paris, followed in July by an Englishman, John Canton. But one unfortunate physicist did not fare so well. Georg Wilhelm Reichmann attempted to reproduce the experiment, according to Franklin's instructions, standing inside a room. A glowing ball of charge traveled down the string, jumped to his forehead and killed him instantly - providing history with the first documented example of ball lightning in the process." [link]
Laboratory experiments
Many attempts have been made over the years to produce ball lightning in the laboratory, but it is easy to mistake other phenomena for ball lightning. Most prominent among these are glowing spheres produced by high-energy arcs between metal electrodes. Such arcs often expel small droplets of molten metal that are heated to extremely high temperatures. Because of their high heat content, these droplets will continue to glow quite brightly for several seconds after landing on a floor or other surface, and their odd physical characteristics can cause them to roll, still glowing brightly, for some distance after landing. They thus mimic the most common description of ball lightning before cooling down into a small speck of metallic dust. The most familiar instance of these glowing spheres is the "weld spatter" usually seen during arc welding operations. The spheres can also be produced when a switch carrying very large electric currents is operated improperly, or during certain grinding or other machining operations.
Some laboratory experiments claim to produce ball lightning, but there is no consensus that the phenomenon reproduced is related to the natural one. The natural occurrences are, by their nature, difficult to document accurately. Consequently, many scientists continue to dispute the existence of ball lightning as a distinct physical phenomenon. In one such occurrence, Singer reports that staff at the Cavendish Laboratory, Cambridge apparently saw ball lightning, although Brian Pippard, the Head of Department, was skeptical on its reality.
In February 2006, scientists at Tel Aviv University claimed to have produced ball lightning in the lab using a [microwave drill] and ceramic substrate.. More recently (June, 2006) researchers at the Max Planck Institute for Plasma Physics successfully recreated the phenomenon using a relatively simple water tank experiment. The experiment involves two electrodes placed in a small tank of salt water, with one electrode covered by a clay tube. A large current of over 60 amps was then run through the water for 150 milliseconds, vaporizing water inside the clay tube and causing a ball of plasma to appear above the tank for 0.3 seconds. Although the plasma glows brightly it was found to be quite cold, much like a neon tube [Max Planck Institute, Berlin, 7 June 2006].
Analysis
An early attempt to explain ball lightning was recorded by Nikola Tesla in 1904.
Difficult features of the lightning include its persistence and its near-neutral buoyancy in air. A popular hypothesis is that ball lightning is a highly ionized plasma contained by self-generated magnetic fields: a plasmoid.[[Citing sources citation needed]] This hypothesis is not initially credible. If the gas is highly ionized, and if it is near thermodynamic equilibrium, then it must be very hot. Since it must be in pressure equilibrium with the surrounding air, it will be much lighter and hence float up rapidly. Magnetic fields, if present, might provide the plasmoid's coherence, but will not reduce this buoyancy. In addition a hot plasma cannot persist for long, because of recombination and heat conduction.
There may, however, be some novel form of plasma for which the above arguments do not fully apply. For example, a plasma may be composed of negative and positive ions, rather than electrons and positive ions. In that case, the recombination may be rather slow even at ambient temperature. One such theory involves positively charged hydrogen and negatively charged nitrites (NO2–) and nitrates (NO3–). In this theory, the role of the ions as seeds for the condensation of water droplets is important.[[Citing sources citation needed]]
Other suggestions include:
- that some stored chemical energy is slowly being released, providing persistence and thrust.[[Citing sources citation needed]]
- that ball lightning is some form of induction phenomenon, ball lightning having allegedly been witnessed inside metal aircraft.
- that the lightning is a Hill's vortex, like a smoke ring.
- that it is an optical illusion similar to the aftereffect of a photographer's flash directed into a person's eyes.This suggestion would tend to account for the reports of "ball lightning" persisting for various lengths of time, and of appearing to float within a room or other dwelling, etc. The commonly shared modern experience of such flashes directly related to flash-photographs, and present-day research of optical perception and neuro-opthalmology, provides yet another possiblity to add to the many hypotheses that have historically been proposed.[[Citing sources citation needed]]
Esoteric explanations
Ball lighting has been connected to reports of several supernatural phenomena, ranging from will o' the wisps to UFOs. Some people believe the ball lightning phenomena are ghosts or spirits. References can be seen in the will o' the wisp and other spirits that take the guise of orbs of light. Some UFO skeptics have suggested that many apparent close encounters are actually observations of ball lightning. UFO enthusiasts report seeing ball lightning often at crop circle sites and believe them to be some kind of intelligence or come from some kind of intelligence while not denying that it is indeed ball lightning.
Another exotic explanation that has been offered for ball lightning is that it is the passage of microscopic primordial black holes through the Earth's atmosphere. No such tiny black holes have ever been positively detected, and it is uncertain whether they would have the physical properties described by ball lightning if they did in fact exist and in great enough quantity to account for ball lightning reports. This explanation also would not account for their alleged co-occurence with electrical storms.
Quotations
- "...Our conclusion is that these fireballs are primarily RF in origin, and not nuclear phenomena..." - Corum
- "...No theory of ball lightning exists which can account for both the degree of mobility that the ball exhibits and for the fact that it does not rise...." - Talbot
See also
Further reading
References
External links
- — the secret of ball lightning and a new field of science and technology
- and — Various articles, experiments, and information on Ball lightning
- — Alternative "toaster" Microwave Experiments
- Open Directory Project: [Ball Lightning]
- Experimental modelling of ball lightning at [balllightning.narod.ru].
- Step by step guide to building your own ball lightning using a household microwave at [http://jlnlabs.online.fr/plasma/gmr/index.htm].
- Ball Lightning musings by Stephen Goodfellow. Some [collected eye witness accounts] and [an attempted experiment].
- [Great balls of lightning] Israeli scientists create plasma fireballs in an experiment. physicsweb.org
- [Physicists Create Great Balls of Fire] Researchers at the Max Planck Institute for Plasma Physics recreate long lasting ball lightning. newscientist.com
- [Unfriendly Fire] Fortean Times on ball lightning at the military
- [Video of a "floating fireball" from an Israeli experiment] - lasts a fraction of a second
- [Researchers have used underwater electrical discharges to generate luminous plasma clouds resembling ball lightning]
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