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If you get caught in the middle of a big, open field during a lightning storm, which
of the following uniforms would be most likely to keep you safe? A thick wetsuit; a superman
costume; a medieval coat of armor; or a birthday suit?
If you answered "medieval coat of armor," you might be a little crazy--but you'd also
be right. You'd be crazy, of course, because lightning is much more likely to strike metal
than to strike rubber, fabric, or bare skin. The reason is that lightning bolts are just
long streams of fast-flowing electrons looking for the easiest path from point A to point
B, and no everyday material provides an easier path than metal.
So why would a material that lures lightning bolts keep you safe during a thunderstorm?
Ironically, for the exact same reason it attracts the the lightning in the first place: metal
is a great conductor of electricity. Electrons glide so easily over metals that they barely
penetrate into the surface. And if an electrical current happens to be moving over a hollow
metal container, like a can or a box or even a welded coat of armor, the current won't
reach the inside of the container.
Physicists call this kind of container a Faraday cage . Or, in the case of the steel-woven
clothing worn by linemen working on high-voltage wires, a Faraday suit.  In fact, your car
is an everyday example of a Faraday cage, which is why--despite what you may have heard
about rubber tires--it's actually the closed metal body surrounding you that keeps you
safe. It channels lightning around, rather than through you.
Of course, if you're away from your car and get caught in an open field during a storm,
chances are slim that you'll have a medieval coat of armor or high voltage line-suit handy.
In that case, whether you're naked or in costume, your body unfortunately happens to be a better
electrical conductor than both air and soil, so it provides a great shortcut for traveling
current. Stand upright, and you're the fastest route for a descending lightning bolt. Lie
down, and you're the best path for current racing along the ground from a nearby strike.
So the best thing to do is crouch low and keep your feet close together. Crouching low
is obvious. But similarly important, when your feet are right next to each other, your
legs don't make for much of a shortcut for the current to get from A to B. And even if
they are the best path for the lightning, when your feet are the only thing touching
the ground, then the current will most likely travel up one leg and down the other, missing
critical organs like your heart--something these cows couldn't avoid.
But, actually, the real best thing to do is avoid lightning altogether--armor or no armor--and
head indoors when you spot a storm on the horizon.
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How to Survive a Lightning Strike

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李顯章 2014 年 7 月 31 日 に公開
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