For centuries, scientists refused to believe that ball lightning existed. They dismissed the persistent reports of these ‘balls of fire’ as mere superstition. Although, as RON HYAMS explains, ball lightning is now recognised by established science, its causes remain unexplained
FLYING TOWARDS Elko, Nevada, USA on a routine mission to refuel B47 bombers in flight on 16 June 1960, a USAF KC-97 tanker aircraft ran into a layer of cloud at 18,000 feet (5500 metres).
The pilot was concentrating on the instrument panel when he was surprised to see a yellow-white ball of light, 18 inches (45 centimetres) in diameter, emerge silently through the windshield. It passed at a fast running pace between his seat and the copilot’s, and travelled down the cabin passageway past the navigator and engineer.
The pilot had been struck by lightning twice on previous flights and knew that an explosion was imminent. His immediate reaction, as an experienced airman, was to concentrate on flying rather than to turn round and watch the ball drift to the back of the aircraft.
After a few seconds of shocked silence, the four men in the flight compartment heard over the intercom the excited voice of the boom operator, who was sitting in the rear of the aircraft. A ball of fire had come rolling through the cargo compartment, danced out over the right wing, and rolled off harmlessly into the night.
This remarkable report concerns ball lightning — one of the many natural phenomena for which science has no explanation. In fact, the properties of ball lightning are so hard to explain that for years scientists doubted its very existence. Their principle was that what can’t be explained can’t exist.
This attitude, unfortunately, is by no means rare among scientists. The fall of meteors to Earth was for many years considered a superstition of ignorant peasants. Indeed, despite many well-documented observations of these fiery bodies, sceptics were at one point so sure of their case that rare meteorite specimens were removed from museum collections and destroyed on the grounds that the stories of meteorites falling from the sky were mere superstition.
The ball lightning controversy has divided the scientific community since the early 19th century, when the first comprehensive reports were prepared on the subject. In 1890 a large number of luminous globes resembling ball lightning appeared in a tornado and were the subject of a meeting of the French Academy of Sciences. The glowing spheres entered houses through the chimneys and bored circular holes in the windows as they departed.
A member of the Academy stood up at the end of the account and commented that the extraordinary properties supposedly attributed to ball lightning should be taken with a liberal pinch of salt, since the observers must have been suffering from optical illusions. In the heated discussion that followed it was agreed that the observations made by uneducated peasants were valueless. At this point the former Emperor of Brazil, a foreign member of the Academy, silenced the meeting by remarking that he himself had actually seen ball lightning!
Even today, many of the reports still have a certain medieval aura of witchcraft and magic about them, which scarcely serves to endear the subject to sceptics. Yet over the centuries literally hundreds of sightings have been made. The evidence for ball lightning now seems irrefutable.
An observation reported in great detail was made by a Russian chemist, M. T. Dmitriev, in 1967. He was camping on the banks of the River Onega in western Russia when there was an intense flash of lightning. A ball of fire appeared, hovering over the water. It was an oval mass of light with a yellow-white core surrounded by layers of dark violet and blue.
Apparently unaffected by the wind, it hovered across the water at a height of about foot (3o centimetres). Dmitriev heard it crackling and hissing as it flew across his head and on to the river bank, where it hung motionless for about 3o seconds.
It left a trail of acrid, bluish smoke as it passed into a group of trees. It bounced like a billiard ball from tree to tree, emitting burst after burst of sparks. After a minute it disappeared from view.
From this and many similar reports it is possible to sketch out the properties ‘typical’ of ball lightning. It usually occurs at the same time as cloud-to-ground lightning. The balls are generally spherical or pear-shaped with somewhat fuzzy edges, and they range from half an inch to a yard (z to ioo centimetres) across. They shine as brightly as a domestic electric lamp; they vary in colour, but are often red, orange or yellow, and they last for anything from a second to over a minute.
The disappearance of a lightning ball may be either silent or accompanied by an explosion. Probably the best known report of a lightning ball causing material damage was reported in 1936 by a correspondent to the Daily Mail. He wrote that during a thunderstorm he saw a large ‘red hot’ ball, subsequently described as the ‘size of an orange’, come down from the sky. It struck the house, cut the telephone wire, burnt the window frame and then buried itself in a tub of water underneath the window. The water boiled for some minutes — but when it was cool enough to search, nothing could be found.
How rare is the phenomenon? In a survey, 400o NASA employees were asked whether they had seen ball lightning. Their answers indicated that it might occur more commonly than had been thought:
A comparison of the frequency of observation of ordinary lightning impact points [with appearances of ball lightning] reveals that ball lightning is not a particularly rare phenomenon. Contrary to widely accepted ideas, the occurrence of ball lightning may be nearly as frequent as that of ordinary cloud-to-ground strokes.
Faced with a phenomenon with such an unusual array of properties, scientists have had an unhappy time searching for a theory to fit the facts. Many scientists have developed elaborate theories to explain away the whole business as an ‘hallucination’ or an `after-image’.
All in the imagination?
The Canadian scientist Edward Argyll claims that ball lightning is merely an optical illusion. He says that when lightning strikes the ground it creates such a bright flash that an observer will see a persistent after-image that can easily be mistaken for ball lightning.
By embracing this theory, Dr Argyll can finally make sense of the extraordinary properties of ball lightning that are the despair of theoreticians who attempt to seek a plausible physical mechanism for it.
Passage through physical surfaces,such as metal screens, is possible for after-images and is reported for lightning balls. After-images last for 2-10 seconds, and most lightning balls are reported to have a duration in the same range.
Unlike lightning balls, after-images generate no sound. But this is no problem for the sceptical scientist: ‘The typical observer finds it easy to imagine “suitable” accompanying sounds.’ But what does Dr Argyll make of cases where the lightning ball leaves physical signs of its presence? He simply rejects the evidence that contradicts his theory: ‘If ball lightning is an optical illusion it would not be unreasonable to categorise these reports as unreliable.’
Yet there can be little doubt that, however imperfect the observations, and in spite of the outlandish behaviour of ball lightning, it does exist. No one will deny the existence of after-images, and most of us have experienced them. But how could they possibly explain fireballs that appear to more than one observer, on the same occasion, to have precisely the same form and to travel” the same path? And how could the after-image theory explain the fact that, although reports come from people who have not previously heard of the existence of ball lightning, all accounts display common features?