00:05You're stuck in a thunderstorm and you need to figure out how long you have to take cover.
00:09The last thing you want to do is math.
00:11But here's an easy way to calculate how far away you are from lightning strikes.
00:16When you see a flash of lightning, count the number of seconds that pass between that flash and the crack of thunder that follows it.
00:25Got that number?
00:26Now, divide it by five.
00:29The resulting number will tell you how many miles away you are from where the lightning just struck.
00:35So let's say you see a jagged burst of light and it takes five seconds before you hear the boom.
00:41That means the lightning struck one mile away from you.
00:45A ten-second gap means the lightning is two miles away.
00:48This math could keep you safe.
00:51The National Weather Service recommends that you take cover if that time between the flash and the boom is 30 seconds, which means the lightning is six miles away.
01:01There's science behind that calculation.
01:04But it's a little complicated.
01:07Light travels 186,291 miles per second, while sound travels just 1,088 feet per second, depending on air temperature.
01:17The gist is that light travels much quicker than sound.
01:21So, you see the light from the lightning basically in real time.
01:25The sound from the thunder, however, travels much slower.
01:29That's why you can get a distance by knowing how long it took the sound from the thunder to reach your ears.
