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Lightning

Photograph of lightning Yes! Lightning heats the air and causes shock waves. These in turn cause sonic booms—but you probably know them better as thunder!

Lightning and thunder happen at the same time. But you see lightning before you hear thunder because light, which travels a million times faster than sound, arrives almost instantly. Sound, on the other hand, takes about five seconds to travel one mile. You can measure how far away lightning is by counting the number of seconds between seeing the flash and hearing the thunder. For example, if you count ten seconds between the lightning and the thunder, the lightning is about 2 miles away.

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Photo: David O. Stillings/The Lightning Stalker.

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