The balls have been reported to melt glass windows, burn objects, and even kill people—notably the 18th-century electricity researcher Georg Richmann.
Many theories have been proposed to explain the phenomenon.
John Abrahamson and James Dinniss, of the University of Canterbury in Christchurch, New Zealand, first proposed the ball-lightning theory that lies behind Pavão's research.
The pair suggested that when lightning strikes a surface, like the Earth's silica-rich soil, a vapor is formed. This silicon vapor may condense into particles that combine with oxygen in the air to slowly burn with the chemical energy of oxidation.
Pavão and Paiva have spent two years testing the theory with a simple experiment.
They used electrodes to shock silicon wafers with enough electricity to create a silicon vapor.
Most of the artificial orbs lasted two to five seconds, but at least one has survived as long as eight seconds—approximating natural ball lightning and far exceeding previous efforts to create the phenomenon in the lab.
Ball lightning expert Graham K. Hubler, a physicist at the U.S. Naval Research Laboratory in Washington, D.C, called the work "very promising."
"The eight seconds is extraordinary and bodes well for a possible explanation for many ball-lightning events," he said.
Abrahamson, the New Zealand scientist, agrees.
"Their balls are of sufficient duration and size to enter the mainstream of ball lightning seen in nature," Abrahamson said.
"Also the balls have sufficient properties similar to those in nature to be convincing ball lightning."
Other Sources of the Phenomenon?
Abrahamson added that other materials besides silicon could also form ball lightning, though none of them have been successfully tested.
"Our theory includes many materials, such as aluminum and iron metals, which appear to be the sources of some balls seen in nature," he said.
Some sightings of ball lightning have occurred in or around airplanes, Abrahamson explained, which suggests that aluminum in the aircraft may have caused the phenomenon.
If these materials can produce ball lightning, he said, the phenomenon may occur after lightning strikes power poles, electrical fittings, roof materials, and other objects.
(Download a lightning wallpaper photo.)
In fact, Abrahamson suggested, conventional lightning may not be the only energy source for the curious orbs.
"It could be smaller atmospheric discharges or even friction heating from earthquakes—balls have been seen coming from an active fault," he said.
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
|
SOURCES AND RELATED WEB SITES
|
