What Happens When Lightning Strikes?

Dwyer and his colleagues set up sensors near the launch tower to see if they could capture high-energy radiation generated by lightning. It didn't take long to get results.

The lightning did indeed produce high-energy radiation, either a powerful burst of X-rays, or possibly a single gamma ray, but the scientists don't know yet which. New sensors are being built to tackle that problem this summer.

Of course, that will still leave the question of why a bolt of lightning should produce these intense, though short-lived, bursts of radiation.

Power-Packed Electrons

The most likely explanation, Dwyer says, is that contrary to theory, the electric field that accompanies lightning is far more powerful than had been thought. It may be so powerful, in fact, that electrons are accelerated to nearly the speed of light, thus creating high-energy radiation whenever they strike an air molecule.

Whatever the explanation, "there's something going on here that we don't understand, and we obviously need to figure it out," Dwyer says.

Meanwhile, in Arizona, researchers didn't need a rocket to figure out what was going on during their dazzling electrical storms. Two video cameras were put on top of a five-story building on the Tucson campus of the University of Arizona and recorded 386 lighting flashes. The recordings were made during the summer of 1997, but the results have only recently been announced in the Journal of Geophysical Research.

By analyzing the tapes, the scientists found that 136 of the 386 thunderbolts, or 35 percent, struck in two or more places.

Krider and Valine figure that means someone on the ground has a lot better chance of getting struck by lightning because one bolt can get him or her in two, or even more, locations.

Experts had thought that if you were two to three miles away from a previous flash, you were probably safe. But that has been changed to six to eight miles because the research shows lightning can strike twice, thus widening the danger zone.

It might seem odd that it's taken so long to figure that out, but as Dwyer says, lightning happens so quickly that "it's all over in a flash."

At this point, it's not entirely clear where his research is leading. It's basic research, and in the end there may not be any practical applications. The X-rays, or gamma rays, that his sensors have detected aren't what will kill you if you get hit by lighting. They're over in a few milliseconds, so compared to the enormous electric charge and intense heat carried by lightning, they may prove insignificant.

But maybe not.

"There's a lot of fundamental science questions that we are trying to answer here," he says. "Maybe some day there will be some applications that come out of it."

At the least, the research should enhance our understanding of one of the most dramatic events in nature.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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