Ball Lightning

Dive under your desk and take cover: A wicked orb of ball lightning is banging around your room! Or, maybe it's just a peaceful, quietly hovering ball of warm light. Or, maybe it's a sparking basketball sized globe chasing you across the plains at night. Or, maybe it's a tiny flaming ball that speeds along and suddenly burns itself out. Whatever it is, it's weird, and it seems to be the first explanation many people will reach for when they hear anything about a round light source: Ball lightning. What is it? More importantly, is it anything at all? What does science have to say on the matter?

Not much, evidently. And, at the same time, way too much. For as many theories as there are attempting to explain it, there is no agreed-upon description of what they're trying to explain. There are innumerable eyewitness accounts, and almost nothing in common among them. For all the scientists who maintain that it's real, none of them has an accepted theory or any testable evidence. For those who cling to the understanding that ball lightning is indeed an accepted phenomenon, consider these points:

1. Ball lightning is not reproducible in the lab [microwave oven plasma doesn't count —BD]. All known forms of electrical discharge are.
   
   
2. There is no standard description of what ball lightning looks like or how it behaves. Reports of its color, its size, its speed, its sound, the conditions under which it appears, its behavior, its shape, and its duration are all over the map.
   
   
3. Not a single photograph or video of ball lightning exists that is considered reliable and not otherwise explainable.
   
   
4. Electromagnetic theory makes no prediction that anything like ball lightning need exist. It does predict all known forms of electrical discharge.

No matter how reliable any one given report might be, it is mired in a sea of other contradictory reports, all describing something very different. This means that either most reports are wrong, or everyone's seeing a different phenomenon. Are some of them actually seeing ball lighting? Maybe, but since we don't know which ones, we don't know what kind of characteristics ball lightning might have; and thus even the anecdotal evidence is too widely at variance to support a single explanation.

In 1997, a reader wrote into Scientific American's Ask the Experts column to ask if ball lightning is real. Two experts responded, both giving widely varying descriptions for what it looks like, how it behaves, and where it comes from, but both credulously identifying all such reports as ball lightning. They both had decent sounding hypotheses, though Scientific American referred to them as theories, a status I don't think they've achieved. Both experts, though, displayed what I would consider a red flag. They both speak quite casually using the term "ball lightning" with confidence that it is a real, single phenomenon: Ball lightning has been seen here and here, ball lightning does this or that. In other words, grouping contradictory reports including hoax claims and misidentification of known phenomena all together and explaining them with another unknown, behind which there's no accepted theory.

The first expert, Paul Handel at the University of Missouri at St. Louis, is a long-standing proponent of the hypothesis that ball lightning is a manifestation of a maser caused by regular lightning striking within a standing wave of UHF or microwave radiation. In 1975 he developed what he calls "Maser-Soliton Theory" to describe this. From his description in the Scientific American column:

...The maser is generated by a population inversion induced in the rotational energy levels of the water molecules by the short field pulse associated with streak lightning. The large volume of air that is affected by the strike makes it difficult for photons to escape before they cause 'microwave amplification by stimulated emission of radiation'... Unless the volume of air is very large or else is enclosed in a conducting cavity, ...collisions between the molecules will consume all the energy of the population inversion. If the volume is large, the maser can generate a localized electrical field or soliton that gives rise to the observed ball lightning. Such a discharge has not yet been created in the laboratory, however.

If you find yourself asking "What the heck is he talking about?" you're not alone. As very few scientists outside of some Russian colleagues of Handel's have written about his "Maser-Soliton Theory", it's fair to say that it appears he has yet to convince any significant number of scientists of its validity. The requirement that there happen to be a standing wave of electromagnetic radiation (of unknown origin) when the lightning decides to strike is one reason.

Handel is not the only one pointing at microwaves, though. The Internet is full of instructions for creating ball lightning in your microwave oven, none of which I recommend that you attempt. Placing carbon veil or fine steel wool in a microwave oven will create a glowing plasma that will damage the roof of your oven unless contained within pyrex. Burning a candle flame with carbon pencil rods or carbon charred toothpicks will produce a similar effect. But referring to these kitchen experiments as "ball lightning" is a bit of a strain. First, the plasma created is not shaped like a ball. Second, being extremely hot (dangerously hot), it rises upward, which is a behavior rarely seen in ball lightning reports. Third, it requires a high-powered microwave oven doing its thing, which probably explains why Paul Handel's "Maser-Soliton Theory"has not produced observable effects in nature.

The second expert who offered his thoughts in Scientific American was John Lowke at Australia's Institute of Industrial Technologies. He proposed the mechanism to be the rapid discharge of electrical energy from a lightning bolt that has struck the ground. As the electrical charge disperses through the ground, it creates a plasma similar to the more familiar corona discharge of St. Elmo's Fire. He proposed that the movement of the ball would be determined by the speed at which the charge moves through the ground, which could explain why some reports state the ball lightning moved against the direction of the wind. But once again, nobody has ever been able to produce this effect artificially, and Lowke acknowledged that "There is no generally accepted theory of ball lightning."

The corona discharge hypothesis is the most interesting, as St. Elmo's Fire is a well understood and well established phenomenon with a sound underlying theory. It's the same thing that makes a fluorescent light glow. When there's a big difference between the electrical charge in the ground and the atmosphere, electrons flow from one to the other. They do this most efficiently out the tips of sharp conductive points; masts on a ship being the most familiar example. Given a strong enough field off this tip, the air is turned into a plasma that fluoresces. St. Elmo's Fire is blue or purple in air. If our atmosphere was neon, it would be reddish orange, and so on for all the other colors that fluorescent tubes come in.

But St. Elmo's Fire has an obvious power source: The powerful flow of electrons coming from the conductive point. Ball lightning, while descriptions of its color are often similar to that of St. Elmo's Fire, has no apparent power source. This might make the microwave hypothesis more attractive, but we have no theory that would explain the concentration of the effect in a sphere, and no theory to explain why there might happen to be a standing microwave. Making light requires energy. Any valid theory of ball lightning has to include the power source for all that light.

No discussion of ball lightning, or any other electrical phenomenon for that matter, is complete with the obligatory mention of the patron saint of eccentric electrical theorists, Nikola Tesla. The popular rumor you always hear is that Tesla was able to produce ball lightning at will in his lab. Regarding what he called "electric fireballs," Tesla reported in 1904 in the journal Electrical World and Engineer "I have succeeded in determining the mode of their formation and producing them artificially." Sadly for the world of science, Tesla's own claims on this matter were never evidenced and have never had any reliable corroboration. There's one oft-repeated quote attributed to Tesla, which seems to be a proposed explanation for fireballs he observed and hoped to recreate:

...It became apparent that the fireballs resulted from the interaction of two frequencies.... This condition acts as a trigger which may cause the total energy of the powerful longer wave to be discharged in a infinitesimally small interval of time... and is released into surrounding space with inconceivable violence. It is but a step, from the learning how a high frequency current can explosively discharge a lower frequency current, to using the principle to design a system in which these explosions can be produced by intent.

Separately, in his Colorado Springs Notes, Tesla attributed ball lightning to resistively heated particles in the air. Just as a light bulb's filament produces heat and light from electrical resistance, so might a carbon particle in the air if exposed to high current. It's a fine speculation, but such a fireball would rise and flame out rapidly (like the plasma created in a microwave), it would not hold a ball shape and hover; even if it did, it would require an extraordinary power source and the presence of carbon particles floating about. That's inconsistent with most ball lightning reports, as are explosions of "inconceivable violence". So really none of what Tesla reported bears much similarity to the ball lightning reports that we commonly hear.

So then, in summary, what about this popular trend of suggesting ball lightning as an explanation for a strange report of a hovering ball of light? It's a little hard to justify. As ball lightning has no established properties, it cannot be argued to be a probable match for any given report. It is fair to say that it's likely that one or more unknown phenomena exist that have triggered eyewitness accounts of hovering balls of light, but there's insufficient theory to support assigning these accounts a positive identification of ball lightning. Indeed, as ball lightning can only honestly be described as an unknown, it would be illogical to use it as an explanation for any report.

By Brian Dunning
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