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Ball Lightning
BY MARIA TRIMARCHI
Lightning is static electricity but on a
scale your socks could never produce: It's three times hotter than the surface
of the sun and could power a 100-watt bulb for
more than three months [source: National Lightning Safety Institute].
Lightning has
long fascinated people, motivating them to create myths about its origin and
inspiring legendary experiments with electricity.
While we're
all familiar with lightning, it's estimated that between one in 30 and one in
150 people around the world believe they have seen balls of lightning hovering
over the ground, floating through walls and even killing people [source: National Geographic].
Stories of
these glowing spheres go as far back as the Middle Ages, maybe even as far back
as the Ancient Greeks.
However, a
recorded case didn't occur until the 18th century when Georg Richmann, a
pioneer in research on electricity, was killed by what's believed to have been
ball lightning.
Perhaps one of
the most famous ball lightning sightings was by a young Czar Nicholas, grandson
to Czar Alexander II, who witnessed a flaming orb during a church service in
the 19th century.
But even
sightings by tsars left people skeptical.
Were these
balls actually lightning? Perhaps otherworldly phenomena?
The skepticism
began to wane in 1963 when a group of scientists flying from New York to
Washington, D.C., witnessed a blazing orb drift down the aisle and disappear
through the rear of the plane.
Looking to
explain what they saw, research began.
Do fiery balls
that melt glass, hover over the ground and float through walls really exist?
Let's find out
more about the phenomenon of ball lightning and the possible explanations for
it.
Explanations and Theories of Ball
Lightning
Ball lightning appears as glowing orbs that
seem to occur during thunderstorms, usually following a lightning strike.
These floating
fireballs shine as brightly as a 100-watt lightbulb;
can be white, yellow, orange, red or blue in color and are typically about the
size of a small grapefruit, although sightings suggest they can range in size
from golf ball to beach ball.
Emanating from
the fireball are little tendrils that seem to jerk the ball around as if it was
under the power of a spastic puppeteer.
They move
slowly and erratically and are followed by smoke trails that form spirals
around them. And after a moment, they disappear.
There's no
scientific explanation for balls of lightning, although there are several
proposed theories.
Throughout
history, speculations about the cause of ball lightning have ranged from the
existence of standing waves of electromagnetic radiation to plasma clouds and
from short-circuiting power lines to St. Elmo's Fire.
The more
unusual explanations suggested mini black holes created during the big bang
or a possible alien presence.
While no
theory has yet to explain ball lightning, a promising theory focuses on silicon.
The most
popular current theory, proposed by John Abrahamson at the University of
Canterbury in Christchurch, New Zealand, suggests that ball lightning is
the result of a chemical reaction of silicon particles burning in the air.
When lightning
strikes the ground, silicon that occurs naturally in soil combines with oxygen
and carbon and turns into pure silicon vapor.
As the vapor
cools, the silicon condenses into a fine dust. The particles in this fine dust
are attracted to each other by the electrical charge created by the
lightning strike, binding together into a ball.
The glow and
heat come from the chemical energy created as the silicon recombines with
oxygen in the air. And once the silicon has burned out, the ball lightning
disappears.
This theory
also suggests materials other than silicon -- such as aluminum and iron metals
-- may also cause the orbs, and that any atmospheric discharge, not necessarily
lightning, may explain why ball lightning has been sighted near power poles,
electrical fitters, and even active faults.
Scientists are
taking this hypothesis into their labs.
Researchers
Antônio Pavão and Gerson Paiva of the Federal University of Pernambuco in
Brazil have been working with the silicon hypothesis and believe they have
verified the theory with silicon substrate and a high-voltage arc.
They applied
140 amps of electricity to silicon substrate, which vaporized the substrate and
sometimes produced golf ball-sized fireballs.
Eli Jerby and
Vladimir Dikhtyar, of Tel Aviv University in Israel, successfully (and
accidentally) recreated ball lightning with a device they call a
"microwave drill."
This microwave
drill is made from a 600-watt magnetron taken from a conventional kitchen
microwave oven and a powerful microwave beam capable of penetrating solid
objects.
The tip of the
drill -- a pointed rod -- aims the beam at a solid substance (silicon, glass,
alumina were among the materials tried) and creates a hot spot in the solid.
When the drill
is pulled away from the hot spot, the drag produces a fireball resembling ball
lightning.
How ball
lightning seems to float through walls, however, is still up for debate.
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