Lightning strike and SCUBA diving


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Posted by Stan Heston on March 20, 2004 at 12:41:31:

I found this interesting tidbit this morning while perusing the 'Net...it is the 3rd question from the top.

http://fitness.msn.com/articles/feeds/?dept=outdoors&article=od_os_030804_inhaledabug

If you can't get to the link, the information is posted below:

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The Wild File
Answers to the weird, the wonderful, and the downright wacky
By Brad Wetzler

Q) If lightning strikes the water while I'm scuba diving, how far away do I need to be to avoid getting hit? Chris Wojcik, Point Pleasant, New Jersey

A) SINCE H2O IS a shockingly good conductor of electricity, it's wise to stay completely dry during an electrical storm. But if circumstances demand otherwise, you're better off scuba diving than, say, swimming, boating, or practicing your belly flop off the high dive. According to a law of physics commonly known as the skin effect, most of the electricity in lightning travels on the surface of an object-be it a copper wire, a metal mast, or a bay off the coast of Belize-as opposed to within it. Some of the lightning's zap will penetrate the water, perhaps ten feet directly below the strike, but otherwise the charge spreads out along the surface, dissipating by various degrees (depending on things like salinity and pollution levels) as it radiates from the point of contact. Since it takes only a few amps to fry a human's circuits and a bolt of lightning is about 25,000 amps, snorkelers and swimmers need to be at least 1,500 feet away from the point of impact to have a decent shot at survival. Scuba divers, as long as they're not surfacing at the strike zone, will be spared entirely.

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