Ball lightning

Ball lightning
Sign	During a thunderstorm, when lightning strikes.
Type	Severe
Cloud of origin	Cumulonimbus
Effect	Various conflicting reports: hovers in the air, may float through walls or other solid objects without effect or may melt and burn them.

Ball lightning is an unexplained atmospheric electrical phenomenon. The term refers to reports of luminous, spherical objects that vary from pea-sized to several meters in diameter. Though usually associated with thunderstorms, the phenomenon lasts considerably longer than the split-second flash of a lightning bolt. Many early reports claim that the ball eventually explodes, sometimes with fatal consequences, leaving behind the odor of sulfur.

Until the 1960s, most scientists treated reports of ball lightning skeptically, despite numerous accounts from around the world. Laboratory experiments can produce effects that are visually similar to reports of ball lightning, but how these relate to the natural phenomenon remains unclear.

Scientists have proposed many hypotheses about ball lightning over the centuries. Scientific data on natural ball lightning are scarce, owing to its infrequency and unpredictability. The presumption of its existence depends on reported public sightings, and has therefore produced somewhat inconsistent findings. Owing to inconsistencies and to the lack of reliable data, the true nature of ball lightning remains unknown. The first ever 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.

It has been suggested that ball lightning could be the source of the legends that describe luminous balls, such as the mythological Anchimayen from Argentinean and Chilean Mapuche culture.

In a 1960 study, 5% of the population of the Earth reported having witnessed ball lightning. Another study analyzed reports of 10,000 cases.

M. l'abbé de Tressan, in Mythology compared with history: or, the fables of the ancients elucidated from historical records:

… during a storm which endangered the ship Argo, fires were seen to play round the heads of the Tyndarides, and the instant after the storm ceased. From that time, those fires which frequently appear on the surface of the ocean were called the fire of Castor and Pollux. When two were seen at the same time, it announced the return of calm; when only one, it was the presage of a dreadful storm. This species of fire is frequently seen by sailors, and is a species of ignis fatuus. (page 417)

This account, however, shares more commonalities with the St. Elmo's fire phenomenon.

Another early description was reported during 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 8-foot (2.4 m) ball of fire was described as striking and entering the church, having nearly destroyed it. Large stones from the church walls were hurled into 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 sulfurous odour and dark, thick smoke.

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