Origin : first accounts dated back from Antiquity
Description : A slow-moving ball of light that is occasionally seen at ground level during thunderstorms. It is generally believed that ball lightning is a ball of plasma, and some scientists believe that it is similar to the highly luminous plasma disks that are formed when explosives are detonated. The ball can typically can measure 30 centimetres across.
Time : During thunderstorms
Records : 5 000+
Location : outdoors
Theory : Many theories on ball lightning have been put forward over the years but none can explain all of the characteristics observed. John Gilman of the University of California at Los Angeles suggests that the plasma ball has a very low density - comparable with the density of air - and is made up of Rydberg atoms. These are atoms whose valence electron has been excited into an orbital with a very high quantum number. He calculates that the radius of such an orbital could be as large as a few centimetres, and that the average atom would thus have a very large polarizability. Attractive Van der Waals interactions - which increase as the polarizability of atoms increase - could then be responsible for the cohesion between the atoms. He computes a value for the cohesive energy per atom to be about one hundredth that of a metal.
John Abrahamson, who works on ball lightning at the University of Canterbury in New Zealand, says that Gilman's model is "imaginative" but adds that "it does not seem workable for several reasons". Abrahamson says that the Rydberg model requires each electron to be separated from its nucleus by a distance of several centimetres. "This is a huge distance for atomic orbitals," he told PhysicsWeb. In 2002 Abrahamson and co-worker, James Dinniss, suggested that ball lightning occurs when silicon is oxidized in the atmosphere following a lightning strike
Ball lightnings
Moderators: eye_of_tiger, shalimar123
Reports
Ball lightning discharges were once thought to be extremely rare occurrences, but recent research shows that a few percent of the US population have been witnesses (Uman). 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. The discharges can appear during thunderstorms, sometimes issuing from a lightning flash, but large numbers of encounters occur during good weather with no storms within hundreds of miles. Ball Lightning tends to float (or hover) in the air and take on a ball-like appearance. The shape can be spherical, ovoid, teardrop, or rod-like with one dimension being much larger than the others. The longest dimension observed is between fifteen and forty centimeters. Many are red to yellow in color, sometimes transparent, and some contain radial filaments or sparks.
Sometimes the discharge appears to be attracted to a certain object, and sometimes to move randomly. After several seconds the discharge leaves, disperses, is absorbed into something, or, rarely, vanishes in an explosion.
A 19th Century depiction of ball lightning
Ball lightning has been seen 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.
One of the earliest recorded, and most destructive, occurrences is thought 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.
Another reference to ball lightning appears in Laura Ingalls Wilder's book On the Banks of Plum Creek [Harper Trophy, 1937] in which the lightning appears during a thunderstorm near a cast iron stove in the family's kitchen. It is described as appearing near the stovepipe, then rolling across the floor, only to disappear as the mother chases it 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 ancecdote from 1753 depicts ball lightning as having violent potential. Professor Georg Richmann, of Saint Petersburg, Russia created a kite flying aparatus 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.
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.
Recently scientists at Tel Aviv University have claimed to have produced ball lightning in the lab using a microwave drill and ceramic substrate
Sometimes the discharge appears to be attracted to a certain object, and sometimes to move randomly. After several seconds the discharge leaves, disperses, is absorbed into something, or, rarely, vanishes in an explosion.
A 19th Century depiction of ball lightning
Ball lightning has been seen 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.
One of the earliest recorded, and most destructive, occurrences is thought 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.
Another reference to ball lightning appears in Laura Ingalls Wilder's book On the Banks of Plum Creek [Harper Trophy, 1937] in which the lightning appears during a thunderstorm near a cast iron stove in the family's kitchen. It is described as appearing near the stovepipe, then rolling across the floor, only to disappear as the mother chases it 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 ancecdote from 1753 depicts ball lightning as having violent potential. Professor Georg Richmann, of Saint Petersburg, Russia created a kite flying aparatus 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.
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.
Recently scientists at Tel Aviv University have claimed to have produced ball lightning in the lab using a microwave drill and ceramic substrate
Analysis
For a long time the phenomenon was treated as myth. Surveys have been taken of eyewitness accounts by at least 3000 people, and it has been photographed several times. There is as yet no widely accepted explanation.
Difficult features of the lightning include its persistence and its near-neutral buoyancy in air. There has been no convincing laboratory demonstration of ball lightning, although in February 2006 Israeli scientists announced that they had created a short-lived effect using the same technology found in microwave ovens.
A popular hypothesis is that ball lightning is a highly ionized plasma contained by self-generated magnetic fields: a plasmoid. 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 plays an important role.
Other suggestions include:
that some stored chemical energy is slowly being released, providing persistence and thrust.
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
Difficult features of the lightning include its persistence and its near-neutral buoyancy in air. There has been no convincing laboratory demonstration of ball lightning, although in February 2006 Israeli scientists announced that they had created a short-lived effect using the same technology found in microwave ovens.
A popular hypothesis is that ball lightning is a highly ionized plasma contained by self-generated magnetic fields: a plasmoid. 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 plays an important role.
Other suggestions include:
that some stored chemical energy is slowly being released, providing persistence and thrust.
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
Esoteric explanations
The natural phenomenon of ball lighting has been reportedly the source of some reports of 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's indeed ball lightining.
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