BALL lightning still defies explanation, according to a series of reports to
be published next month by Britain鈥檚 Royal Society. To explain the bizarre
phenomenon may take the combined wisdom of more than 10 fields of science, from
maser physics to inorganic chemistry, they conclude.
Eyewitnesses have seen the glowing spheres known as ball lightning float
through the air for up to a minute, usually when thunderstorms are nearby. These
reports have often been dismissed as fantasy, but with around 10,000 sightings
over the past few decades, scientists are now convinced the effect is real.
Next month鈥檚 issue of the Royal Society鈥檚 Philosophical Transactions A
brings together many previously unpublished sightings of ball lightning.
In one, a luminous ball left a hole the size of a basketball in a screen door as
it entered a house in Oregon, then navigated down to the basement and wrecked an
old mangle. In another, an 80-centimetre glowing blob bounced on a Russian
teacher鈥檚 head more than 20 times before vanishing.
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But explaining the reports is tricky. Ball lightning can shine as brightly as
a 100-watt light bulb, but has no obvious power supply. It doesn鈥檛 radiate heat,
yet it can melt glass when it floats into windows.
A leading theory suggests that ball lightning forms when a lightning strike
vaporises and decomposes silica in the soil. The silicon vapour condenses into a
floating ball of fine dust held together by electrical charges, which would
oxidise and glow. Another possibility is that air ionised by lightning could
bind with water to create a hot ball of plasma with a cool water-and-ion coat
(New 杏吧原创, 8 April 2000, p 22).
But it鈥檚 likely that none of the current theories tells the whole story. Ball
lightning is probably the product of a family of different processes. Lab
simulations of these processes can make mini ball lightning, but it鈥檚 far
smaller than natural versions and doesn鈥檛 live nearly as long.
鈥淚t鈥檚 important to try and understand these things,鈥� says David Turner, a
retired physical chemist in Maryland who has studied ball lightning for a
decade. He thinks similar processes might explain spontaneous human combustion
and the movement of objects by 鈥減oltergeists鈥�.