MANY LIGHTNING INJURIES AREN'T FROM DIRECT HITS BUT FROM GROUND SHOCKS, WHEN ELECTRICITY RUNS THROUGH THE EARTH AND INTO THE BODY
Blinding and explosive—here and gone in two-tenths of a second—lightning "is the hottest natural force on the face of the earth," says Martin Uman, one of the world's preeminent lightning researchers. "Nuclear energy can be hotter, but that's artificial." Uman's program at the University of Florida is one of six that DARPA, the pure-research arm of the Department of Defense, has funded to better understand exactly how lightning originates. That remains one of the true mysteries of science.
If the precise genesis of lightning is not known (it initially involves the friction of millions of ice crystals in clouds), Uman and his ilk have established that lightning comes in many forms and has a variety of strengths, from a weak 100-ampere flicker to a 1,000-amp streamer to a cloud-to-ground stroke that reaches 300,000 amps and 50,000° Fahrenheit—five times hotter than the surface of the sun.
The National Weather Service estimates that lightning kills 55 people in the U.S. per year, many of them boaters, golfers and farmers. And many, like the climbers on the Grand Teton last year, don't experience a direct hit, but rather ground shocks: electricity running over or through the earth. Even so, Uman says, more than half of those who endure a direct strike survive.
"The reason is that the energy flashes over their skin," he explains. "Whether you live or not depends on whether it enters the body, and how much electricity goes through the heart—if it stops the heart."
With the possible exception of Floridians, Americans tend to be ill-informed about the dangers of lightning. The rule of thumb many of us learned as children—counting "one-one-thousand" for each second between the flash and the sound of thunder to determine how many miles away the lightning is—is off by a factor of five. John Gookin, who has studied outdoor lightning risk management for the National Outdoor Leadership School, based in Lander, Wyo., says every five seconds is the equivalent of one mile. One second between a flash and thunderclap means that the lightning could have hit less than a quarter-mile away.