The monastery chronicles of a 12th century Benedictine monk named Gervase, who was assigned to the Christ Church Cathedral Priory in Canterbury, wherein physicist Brian Tanner and historian Giles Gasper came upon a striking description of an apparent manifestation of ball lightning. This is the label given to mysterious shining orbs of light that are reported to sometimes appear in the sky, near the ground, and even indoors just before, during, or after thunderstorms.
According to Professors Tanner and Gaspar, this description of June 7, 1195 AD is by far the oldest mention of ball lightning ever found in a manuscript written in England. In fact, the description by the Benedictine Gervase predates the next-earliest reference by nearly 450 years.
Ball lightning has been one of the most mysterious natural phenomena for the intervening centuries, partly because it is so rare and transient and therefore difficult to investigate. But a fortuitous observation during field experiments in China to study ordinary lightning, reported in Physical Review Letters, has now provided what seems to be the first measurement of the emission spectrum of ball lightning. The data suggest that the glowing ball was composed of elements from soil, consistent with one popular theory.
The spectrum of a cloud-to-ground lightning strike and of the ball lightning it generated. The ball lightning is the white dot at the far left, and its spectrum is the slightly brighter band of colors at the foot of the irregularly shaped main lightning spectrum.
Ball lightning typically appears during thunderstorms as a glow, ranging from the size of a golf ball to several meters across, which floats in the air for between one second and tens of seconds. There are many historical reports of such “fireballs” injuring or even killing people and setting buildings alight, and they have sometimes been given supernatural explanations.
Scientific theories of ball lightning abound, with varying degrees of plausibility. Glowing plasma balls have been created artificially by passing intense microwaves through air or by underwater electrical discharges. But such laboratory experiments may not bear any relation to ball lightning formation in the natural environment—about which very little is known, since there has been almost no solid data.
One popular theory is that ball lightning is caused when lightning striking the ground vaporizes some of the silicate minerals in soil. Carbon in the soil strips the silicates of oxygen through chemical reactions, creating a gas of energetic silicon atoms. These then recombine to form nanoparticles or filaments which, while still floating in air, react with oxygen, releasing heat and emitting the glow. If that’s so, one should expect to see atomic emission lines of silicon and other soil elements in the spectrum.
That is what Ping Yuan and co-workers from Northwest Normal University in Lanzhou, China, now report. They had set up spectrometers on the remote Qinghai Plateau of northwest China to investigate ordinary lightning, which is frequent in this region. During one late-evening thunderstorm in July 2012, they saw ball lightning appear just after a lightning strike about 900 meters from their apparatus and were able to record a spectrum and high-speed video footage of the ball.
The recorded glow was about 5 meters across—the actual size of the ball was much smaller—and it changed from white to reddish during the second or so that it lasted. Although the darkness prevented the researchers from estimating the ball’s altitude, they saw it drift horizontally for about 10 meters and ascend about 3 meters. Yuan says that this is the first time ball lightning has been seen to be created by a cloud-to-ground lightning strike.
The researchers found that the spectrum contained several emission lines from silicon, iron, and calcium—all elements expected to be abundant in soil. One would also expect aluminum to be present, given its abundance in soil minerals. But the researchers couldn’t confirm that, as there are no emission lines of neutral aluminum atoms within the spectral range of their instrument (wavelengths of 400–1000 nanometers). The team also used their video data to plot the ball lightning’s intensity and apparent diameter as they varied in time, down to the millisecond time-scale.
One of the most grounded theories regarding ball lightning, proposed by John Abrahamson and James Dinniss of the University of Canterbury in Cristchurch, New Zealand, is that it's caused by lightning striking soil and turning its chemical contents into a vapor. That vapor is said to then condense into a ball of floating aerosol that glows with the heat of the soil's elements mixing with oxygen. Thanks to the spectrograph readings, this theory, first postulated in 2000, now seems all the more plausible.
The findings are not entirely conclusive regarding the nature of ball lightning and not evidence that Abrahamson's theory is universally applicable. For instance, it does not explain how ball lightning can pass through indoor environments like people's homes or inside the cockpit of a plane, as was the case in an instance of ball lightning that passed through the cockpit of a C-133A cargo plane traveling to Hawaii from California. Nor does it address what causes the bang many say to be typical in the evaporation of the glowing orbs.
Led by CSIRO* scientist John Lowke, the new theory focuses on how ball lightning occurs in houses and inside moving aeroplanes – and how it can pass through glass. His theory also proposes that ball lightning is caused when leftover ions (electric energy), which are very dense, are swept to the ground following a lightning strike.
"A crucial proof of any theory of ball lightning would be if the theory could be used to make ball lightning. This is the first paper which gives a mathematical solution explaining the birth or initiation of ball lighting," says Lowke.
Lowke proposes that ball lightning occurs in houses and within aircraft when a stream of ions accumulates on the outside of a glass window and the resulting electric field on the other side excites air molecules to form a ball discharge. The discharge requires a driving electric field of about a million volts.
"Other theories have suggested ball lightning is created by slowly burning particles of silicon formed in a lightning strike, but this is flawed. One of the ball lightning observations cited in this paper occurred when there was no thunderstorm and was driven by ions from the aircraft radar operated at maximum power during a dense fog."
Lowke used eye-witness accounts of ball lightning by two former US Air Force pilots to verify the theory. Former US Air Force lieutenant Don Smith recalls: "After flying for about 15 minutes, there developed on the randome (radar cover) two horns of Saint Elmo's fire. It looked as if the airplane now had bull's horns...they were glowing with the blue of electricity."
Lowke's paper gives the first mathematical solution explaining the birth or initiation of ball lightning using standard equations for the motion of electrons and ions. He argues it is unique because it not only explains the birth of the ball but also how it can form on glass and appear to pass through glass resulting in globes of light in people's homes or in aircraft and jet fighter and bomber cockpits.
See:
https://physics.aps.org/articles/v7/5
See:
https://www.cnet.com/news/scientists-accidentally-record-ball-lightning-in-nature-for-first-time/
See:
https://www.ancient-origins.net/news-history-archaeology/ball-lightning-0016354
* CSIRO or the Commonwealth Scientific and Industrial Research Organisation is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO maintains more than 50 sites across Australia and in France, Chile and the United States, employing about 5,500 people.
We are Australia’s national science organisation and one of the largest and most diverse scientific research organisations in the world. Our research focuses on the biggest challenges facing the nation. We also manage national research infrastructure and collections. (
https://research.csiro.au)
I have never seen ball lightning, but I have read about its appearances in heavy weather during long bombing missions during WWII in Europe and during the course of my youthful reading. I am pleased that this unique natural phenomena is finally being winkled out into real physics from the mystical past where it will no longer be called "Foo Fighters" and the like.
Hartmann352
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