Mysterious lightning phenomenon recorded in ancient medieval text

British researchers have uncovered what they believe to be the earliest written account in England of a bizarre – and poorly understood – phenomenon known as ‘ball lightning’, chronicled in a medieval text written by a Benedictine monk who lived just under 1000 years ago. 

What is ball lightning?

Usually associated with thunderstorms, ball lightning has been described as a bright spherical object, on average 25 centimetres across but sometimes reaching several metres in diameter.

The phenomenon has mystified humans for centuries, with the previous oldest written account having been found in a 1638 report, which described a ball of fire flying into a church, accompanied by a great peal of thunder.

Scientists don’t really understand what causes ball lightning, and have long been on the hunt for an explanation. One possible answer is that lightning striking the ground vaporises some of the minerals in the soil, which then, floating in the air, react with oxygen and release heat and light to produce an unearthly glow. This explanation seems supported by a 2014 study, which identified trace evidence of silicon, iron and calcium – all abundant in soil – in a flash of ball lightning.

Historical sleuthing uncovers bizarre weather report

Written by the 12th-century Benedictine monk Gervase, the account states that “a marvellous sign descended near London” on 7 June 1195. Gervase described a dense, dark cloud emitting a white substance that grew into a spherical shape, and from which a fiery globe fell towards the river.

The account was uncovered by the unlikely academic pairing of physicist Brian Tanner and historian Giles Gasper, both of Durham University. The team compared Gervase’s text with historic and modern reports of ball lightning and came to the same conclusion: this dramatic event in 1195 was likely the same phenomenon.

“Gervase’s description of a white substance coming out of the dark cloud, falling as a spinning fiery sphere and then having some horizontal motion is very similar to historic and contemporary descriptions of ball lightning,” says Tanner. 

“If Gervase is describing ball lightning, as we believe, then this would be the earliest account of this happening in England that has so far been discovered.”

Gasper says that, from a historian’s perspective, the account is convincing. Gervase recorded the dates and times of solar eclipses remarkably accurately and in vivid detail. 

“The main focus of Gervase’s writings was Christ Church Cathedral Priory in Canterbury,” says Gasper. “But he was also interested in natural phenomena, from celestial events and signs in the sky to floods, famine and earthquakes.”

The findings are published in the Royal Meteorological Society’s journal Weather.