Sourced facts

The same wording as on the topic pages, gathered in one list, each with its source.

Ball lightning, also called globe lightning, is a rare aerial phenomenon in the form of a luminous sphere that is generally several centimetres in diameter. Britannica
It usually occurs near the ground during thunderstorms, in close association with cloud-to-ground lightning. Britannica
It may be red, orange, yellow, white, or blue in colour and is often accompanied by a hissing sound and distinct odour. Britannica
It normally lasts only a few seconds, usually moving about and then vanishing suddenly, either silently or explosively. Britannica
Ball lightning has been reported to cause damage by burning or melting but is usually harmless. Britannica
Its causes and its relation to common lightning are not known. Britannica
Among the suggested explanations are air or gas behaving abnormally, high-density plasma phenomena, an air vortex containing luminous gases, and microwave radiation trapped within a plasma bubble. Britannica
Sometimes bead lightning is mistaken for ball lightning. Britannica
Bead lightning is most apparent when the current in a cloud-to-ground flash persists for an appreciable fraction of a second. In those cases the luminosity also persists and the channel may have regions of enhanced luminosity that resemble a string of beads. Britannica
The Met Office describes ball lightning as an incredibly rare form of lightning in which a persistent and moving luminous white or coloured sphere is seen. Met Office
The Met Office says there are various hypotheses, but the leading one is that the luminous sphere could be a bubble of glowing soil particles which was formed when the lightning strike hit the ground. Met Office
The Met Office also lists pearl-necklace lightning, also termed chain lightning or beaded lightning, in which variations of brightness along the discharge path give rise to a momentary appearance similar to pearls on a string. Met Office
Rocket lightning, in the Met Office list, is a very rare and unexplained form in which the speed of propagation of the lightning strike is slow enough to be perceptible to the eye, normally seen at the top of the thunderclouds. Met Office
The Royal Meteorological Society says it is estimated that only one in a million lightning strikes produces the ball lightning phenomenon. RMetS
Despite that estimate, the same RMetS article says there are more than 10,000 written accounts of the bright, spherical lights in the sky, which linger for seconds longer than a true lightning bolt. RMetS
Ordinary fork lightning, the RMetS article notes, is an atmospheric electrical discharge, typically formed when a negatively charged leader from a cloud is met by a positively charged streamer. RMetS
According to other accounts collected by the RMetS article, ball lightning ranges in size from a golf ball to a small car. RMetS
The same accounts say it can hover in the air, roll along the ground or come crashing through a window, lasts between a few seconds and a couple of minutes, and can simply disappear or violently explode. RMetS
On the evening of Saturday 27 July 2013, after a thunderstorm in Cumbria, Kath Egerton reported a glow of light on the grass about 60 cm in diameter, then a slightly larger bright orangey-yellow light that passed rapidly in front of her, followed by an incredibly loud noise. RMetS
Kath Egerton reported the observation to the Tornado and Storm Research Organisation (TORRO). RMetS
The RMetS article recounts the Great Thunderstorm at a church in Widecombe-in-the-Moor, Devon, on 21 October 1638: four people reportedly died, and approximately 60 were injured, when a 2.4 m ball of fire was described as striking and entering the church. RMetS
On 6 August 1944, according to the same article, a ball of lightning smashed through a closed window in Uppsala, Sweden, leaving a circular hole about 5 cm in diameter, passed through a kitchen, and was recorded by a lightning-strike tracking system at Uppsala University. RMetS
The RMetS article says some scientists have studied ball lightning for decades and still are not sure whether it exists. RMetS
One explanation offered by sceptics, the article says, is that ball lightning is merely a positive after-image left on the eye in the wake of a standard lightning flash. RMetS
The 2013 RMetS article calls the atmospheric maser theory the prevailing physical theory of ball lightning: electrical activity puts large clouds of charged water molecules into an excited state, briefly causing light amplification by stimulated emission of radiation. RMetS
The same article says that before this can be confirmed as the cause, the process must be replicated in a laboratory. RMetS
According to some reports in that article, Nikola Tesla was able to make ball lightning in his lab in Colorado Springs in 1899/1900, but if he did create it, he did not describe his methods in a way that has allowed anyone since to reproduce his work. RMetS
The article says Russian scientists successfully made plasma balls in the lab in 2002. RMetS
A Colorado team led by Dr Mike Lindsay, the article says, made brilliant clouds of plasma emerge from a specially prepared solution and maintained them for nearly half a second. RMetS
Dr Lindsay said, in the article’s wording, “I don’t think what we’ve created is lightning,” and that ball lightning is used almost generically for phenomena not described by normal lightning, bead lightning, St Elmo’s fire or aurora. RMetS
He also said, “And likely it’s not one thing but several things that have similar observables.” RMetS
Abrahamson and Dinniss, in a 2000 Nature letter, write that the “average” ball lightning appears as a sphere with a diameter of 300 mm, a lifetime of about 10 s, and a luminosity similar to a 100-W lamp. Nature 2000
In their wording it floats freely in the air, and ends either in an explosion, or by simply fading from view, and almost invariably occurs during stormy weather. Nature 2000
They write that observations of ball lightning have been reported for centuries, but the origin of this phenomenon remains an enigma, and that several energy sources have been proposed, but none of those models has succeeded in explaining all of the observed characteristics. Nature 2000
Their model is that when normal lightning strikes soil, chemical energy is stored in nanoparticles of Si, SiO or SiC, which are ejected into the air as a filamentary network, and as the particles are slowly oxidized in air the stored energy is released as heat and light. Nature 2000
They investigated this basic process by exposing soil samples to a lightning-like discharge, which produced chain aggregates of nanoparticles: these particles oxidize at a rate appropriate for explaining the lifetime of ball lightning. Nature 2000
In a paper published on 17 January 2014, Jianyong Cen, Ping Yuan and Simin Xue reported that ball lightning was observed with two slitless spectrographs at a distance of 0.9 km. PRL 2014
The ball lightning, they write, is generated by a cloud-to-ground lightning strike, and it moves horizontally during the luminous duration. PRL 2014
Summarising earlier reports, they write that it is usually a sphere or ellipsoid with a diameter between 1 and 100 cm, moving horizontally with speeds of a few meters per second, and that the color can be white, yellow, red, orange, purple, or green. PRL 2014
The event occurred during a thunderstorm at 21:54:59 on 23 July 2012 (Beijing Time), on the Qinghai Plateau of China. PRL 2014
The entire luminous duration of the ball lightning was 1.64 s. PRL 2014
They report that it moves horizontally with an average 2D speed of about 8.6 m/s, and that the actual speed should be faster than the 2D speed if it also moved in the line-of-sight direction. PRL 2014
The colours of purple, orange, white, and red can be seen in turn during the luminous duration: powerful purple white at the beginning, orange at 80 ms, approximately white from 160 to 1100 ms, and red at the dissipating stage after 1120 ms. PRL 2014
The spectral analysis indicates that the radiation from soil elements is present for the entire lifetime of the ball lightning. The emission lines of silicon, iron, and calcium appeared, and silicon, iron, and calcium are the main components of soil. PRL 2014
The authors write that there are reasons to believe that the observed ball lightning was generated by the cloud-to-ground lightning striking to the soil on the ground. PRL 2014
They also write that there may be more than one type of ball lightning and more than one mechanism that explains it, and that their observation is only one event that may not be representative of all ball lightning. PRL 2014
They warn that the apparent diameter is not the real diameter of the ball lightning. This site does not treat the apparent-diameter figures in that paper as the object’s true size. PRL 2014
Alexander Keul, in a 2021 history in History of Geo- and Space Sciences, writes that since François Arago’s Sur le tonnerre (1837), the term ball lightning (Kugelblitz, foudre globulaire) stands for a still unexplained group of metastable luminous phenomena in atmospheric electricity. Keul 2021
In that outline, ball lightning appears seemingly random in time and space, lasts a few seconds, and disappears with traces or without; because of its unpredictable occurrence, most of the collected material remains anecdotal. Keul 2021
Keul quotes Rakov and Uman (2003) characterising ball lightning as “a phenomenon for which there exists numerous witness reports but little, if any, scientific documentation such as photographs, videotapes, or other scientific recordings.” Keul 2021
Keul writes that Rakov and Uman counted almost 5,000 observation reports. Keul 2021
He quotes them further: “There may be more than one type of ball lightning and more than one mechanism by which ball lightning is generated”; “There have been many theories devised to explain ball lightning. None is completely satisfactory”; and “many luminous phenomena created in the laboratory are claimed by their creators to be ball lightning.” Keul 2021
Keul also notes a COST Action proposal by Thottapillil (2005), with 30 European researchers, and the consensus that “the reality of ball lightning is not in doubt.” Keul 2021
A citation classic in ball lightning literature, Keul writes, is the case of Georg Wilhelm Richmann, a Baltic German physicist and member of the St Petersburg Academy of Sciences, who, during work on atmospheric electricity, was electrocuted in 1753. Keul 2021
From an investigation protocol with autopsy results (Anonymous, 1755, pp. 64–68), Keul writes, it is obvious that it was a conventional lightning accident caused by a non-grounded conductor. Keul 2021
However, a popular engraving pictured a lightning ball that hit Richmann. Keul adds that ball lightning acquired a deadly and destructive popular image fed by injuries and damage caused by ordinary cloud-ground strokes. Keul 2021