Speaker 1: Welcome to brain Stuff from how stuff works dot com
Speaker 1: where smart Happens. Hi, I'm Marshall Brain with today's question,
Speaker 1: how can you figure out how far away lightning struck?
Speaker 1: If you can see the bolt of lightning actually strike
Speaker 1: the ground, or if you can see a flash from
Speaker 1: a bolt of lightning, you can calculate how far away
Speaker 1: it's struck by timing the arrival of the thunder. Let
Speaker 1: me show you how to do this with miles first,
Speaker 1: and then we'll do it in kilometers. The sound of
Speaker 1: thunder travels through the air at the speed of sound. Officially,
Speaker 1: the speed of sound is about feet per second, so
Speaker 1: sound travels one mile in roughly five seconds. When you
Speaker 1: see the flash of a lightning bolt, you can start
Speaker 1: counting seconds and then divide by five to see how
Speaker 1: far away the lightning struck. For example, if it takes
Speaker 1: ten seconds for the thunder to roll in, you divide
Speaker 1: by five and you know that the lightning struck about
Speaker 1: two miles away. Now let's do it in metric Officially,
Speaker 1: this either sound is about three meters per second, so
Speaker 1: sound travels one kilometer in roughly three seconds. When you
Speaker 1: see the flash of a lightning bolt, you can start
Speaker 1: counting seconds and then divide by three to see how
Speaker 1: far away the lightning struck. If it takes ten seconds
Speaker 1: for the thunder to roll in, you can divide by
Speaker 1: three and you know that lightning struck about three kilometers away.
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