48 | New Scientist | 24 October 2020
used lightning detection systems to map the
world’s most active lightning hotspots. She
says that something as dim as ball lightning,
which is often reported to glow about as
brightly as a 100 watt incandescent bulb,
wouldn’t be picked up by satellites or the
various land-based lightning detection
systems. To record ball lightning, she says,
“it would have to be happening right in front
of your camera”.
Even without direct evidence to go on,
Martin Uman at the University of Florida
believes there is something to the
phenomenon. Uman has spent nearly the
entirety of his 50-year career studying
lightning and has collected or reviewed
hundreds of encounters with glowing
spheres much like Aiello’s. A blue ball
glancing off a student’s finger, a white ball
rolling down the centre of a military tanker
aircraft, a yellow ball hovering above an
engineer’s desktop computer. “There are a
number of published papers where ball
lightning was inside of a commercial airplane
and all the passengers saw it as it floated
down the aisle,” says Uman.Antimatter meteorites
While the details of any one account of ball
lightning sound incredible, Uman thinks the
accumulation of thousands of similar reports
over the course of hundreds of years points
to a genuine phenomenon with no sound
scientific explanation.
Dozens of mind-bending suggestions
have been published to explain ball lightning,
ranging from mini black holes to meteorites
made of antimatter, but it is more likely that
something simpler is involved. Uman
suspects that ball lightning is an after-effect
of the electric discharge from standard
lightning strikes, which could occasionally
kick off strange chemical reactions capable
of producing a glowing sphere.
If lightning hit a patch of ground rich
in silica and carbon, for example, some
researchers believe it could form a cloud of
pure silicon nanoparticles, emitting light and
heat as it oxidised. Any such explanation that EDUARD
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PHOTO^ LIBRARY“ The experiments
guided lightning
through dozens
of materials
including
saltwater,
metals, and
even bat guano”
depends on hot gases comes with problems
of its own. Namely, ball lightning is
consistently reported to hover in place,
glide horizontally and move against the
wind – none of which a hot gas should do.
“The field doesn’t need more theories,”
says Karl Stephan, an electrical engineer
at Texas State University. “The field needs
experiments and observations that are
instrumented well enough to get more
observational data.” That’s why Stephan has
been pursuing ball lightning experimentally
for nearly two decades, testing plenty of
hypotheses that rely on an electric discharge.
In one experiment, Stephan tested an
idea that some researchers claim as the
ultimate explanation of ball lightning.
Short-lived balls of hot, ionised gas, called
Gatchina plasmoids, can be produced
when high-voltage electricity is discharged
near the surface of salty water. Stephan was
able to steer these plasmas horizontally, but
they disappeared in a fraction of a second
while, like all hot gases, noticeably rising.
“You take a still picture of it – it looks a
whole lot like what people describe ball
lightning to be,” says Stephan. “But I don’t
think that’s the whole explanation or even
most of the explanation.”
Uman has also conducted experiments
aimed at producing ball lightning via electric
discharge. By firing small rockets with
trailing wires into active thunderstorms, he
has triggered hundreds of lightning bolts
that can then be directed through carefully
designed equipment. In a single summer, he
guided lightning through dozens of different
materials including pools of saltwater,
various metals and even bat guano in the
hope of creating ball lightning. Although
he and his team were able to create a few
spherical sparks – albeit ones that were far
too short-lived to be ball lightning – and the
same kind of rising plasmas Stephan and
others have made, they resolutely failed to
produce the phenomenon they were after.
Other ball lightning theorists rely less
on lightning bolts themselves. Robert
Cameron at the University of Strathclyde,
UK, thinks ball lightning might be caused byBall lightning reportedly
resembles a sphere of
plasma. But plasma
shouldn’t hover on the spot,
as ball lightning seems to do