Imagine -- or perhaps you've experienced something like this for real -- you've taken shelter at a picnic table under cover with thunderstorms roaring nearby. All of a sudden you notice a ball of light appear out of nowhere floating toward you. As the ball enters the shelter, you're amazed to hear it sizzling like a burning branch but feel no heat. It appears to float undisturbed through and then out the shelter where it bounces across the ground before disappearing.
You scratch your head and wonder -- was this an illusion, a natural phenomenon, or perhaps a probe from an alien mother ship circling the Earth? If you are an oldies-but-goodies fan (or just an oldie like myself), maybe your first thought is the refrain from Jerry Lee Lewis's 1957 hit song, Great Balls of Fire: "I say goodness gracious great balls of fire...oooeee, oooee".
What you might have witnessed is ball lightning, a luminous orange or reddish spherically shaped object, which averages about 6 to 20 inches in diameter and lasts a few seconds to a few minutes before disappearing (much longer than a split-second lightning bolt).
Well documented reports of ball lightning date back to the Middle Ages, including descriptions of it passing through solid objects such as windows and walls without dissipating. However, physical evidence for its existence and behavior has been ambiguous at best.
A new report from the UK's Royal Society gathers many previously unpublished sightings of ball lightning. One describes how a luminous ball left a hole the size of a basketball in a screen door as it entered a house and then found its way to the basement. In another, a glowing blob bounced on a Russian teacher's head more than 20 times before vanishing. In one famous sighting in March 1963, a glowing sphere floated down the aisle of an Eastern Airlines aircraft that had been struck by lightning.
Perhaps most bizarrely, shortly after takeoff of an Ilyushin-18 flying over the Black Sea, a "fireball" appearing on the fuselage in front of the crew's cockpit reemerged several seconds later in the passenger's lounge and slowly flew about the heads of the stunned passengers. The object left the plane noiselessly from the tail section. Upon landing, holes were discovered in the fuselage fore and aft.
Believers vs. non-believers
Reports such as these have long been dismissed as a product of fanciful imaginations, folklore, and hoaxers not unlike dismissive attitudes towards UFO sightings. However, with around 10,000 sightings over the past few decades and, more significantly, plausible physical explanations and recent laboratory recreations of something resembling ball lightning, most, but not all scientists seem convinced that it is a real, naturally occurring phenomenon.
Nevertheless, the exact physical mechanisms responsible for its occurrence are largely unknown. Since natural ball lightning appears to occur only in the vicinity of thunderstorms and lightning, its origin and composition is most likely electrical in nature. Beyond that, as described by an article in New Scientist, explaining it has "proven to be bafflingly, frustratingly, mind-bendingly difficult" (as are most scientifically challenging issues -- think climate change, for example). One major problem is that there's no agreement on what it is one is trying to explain. There are innumerable eyewitness accounts, and almost nothing in common among them.
Laboratory experiments (such as this one and this one) might shed some light on the nature of ball lightning. However, although some experiments have produced effects that are visually similar to reports of ball lightning, it is presently unknown whether these are actually related to any naturally occurring phenomenon.
Among the many plausible explanations, one leading theory suggests that ball lightning forms when a lightning strike vaporizes silica in soil. The silicon vapor condenses into a fine dust that is bound together by electrical charges into a floating ball, which would oxidize and glow. Another suggests that ball lightning is a highly ionized blob of plasma held together by its own magnetic fields. The bottom line is that no single theory tells the whole story. Rather, ball lightning likely reflects a set of different processes.
Not all scientists are totally convinced that ball lightning is a real, physical phenomenon. The headline of a recent article in New Scientist proclaims: "Ball lightning may be an illusion." The argument is that fluctuations in magnetic fields from nearby lightning bolts could "trick" the brain into "seeing" glowing objects. The claim, which I'm not yet ready to accept, is that magnetically induced hallucinations account for about half of all ball lightning sightings.
Have you ever seen ball lightning, real or imagined? Let's hear about your experience.