Ball Lightning Explained
|Ball Lightning Explained
|Feb. 3, 2000 -- Ball lightning -- rare but dazzling spheres of bouncing
|light -- may form with a poof when lightning strikes the Earth, say
|scientists who propose a new theory to explain the phenomenon�s origins.
|Ranging in size from a golf ball to a soccer ball, ball lightning has been
|reported during thunderstorms since the Middle Ages. As bright as a
|lightbulb, an average ball lightning glows blue-white for about 10 seconds,
|but can last up to a minute before exploding or disintegrating. Some hiss
|like discharging power lines.
|Scientists estimate one out of a hundred people has seen one, although many
|witnesses face disbelief.
|"They are for sure real," says Graham Hubler, a physicist at the Naval
|Research Laboratory, who once saw ball lightning. "But they are so far out
|of your experience, you don�t know what you�ve seen."
|One reason ball lightning is so mysterious is that scientists have been
|unable to produce it in the laboratory. Until now, they assumed the orbs
|formed out of thin air.
|But John Abrahamson of the University of Canterbury in New Zealand has a
|more earthly explanation: When lightning strikes certain types of soils,
|silicon in the earth vaporizes "like a smoker�s puff," then condenses into
|tiny solid wires.
|A thousand times thinner than a human hair, these wires then coalesce into
|charged, ball-shaped network that glows when infiltrated by oxygen in the
|air, according to the theory presented in this week�s journal Nature.
|One glowing sphere entered a woman�s house and hovered above her table�s
|"She could see within the ball lightning these chains, web-like structures
|radially forming and reforming. This is very close to the theory that I�ve
|put forward," says Abrahamson.
|His explanation far surpasses previous theories, according to Hubler. "I
|believe his is the first model ever put forward that can explain nearly all
|the features of ball lightning."
|The new theory is also testable. Abrahamson has found silicon in the soil
|where lightning has struck. And lab experiments have produced tiny silicon
|wires. He thinks they�ll successfully make a ball of lightning in the next
|Efforts to understand these "ephemeral cotton-candy kind of things" still
|suffer from lack of visible evidence, Hubler says, urging any readers who
|have captured ball lightning on film to contact the researchers.
|By Emily Sohn, Discovery News Brief