How far away is the storm? The flash-to-bang method can help.

When lightning is made by a storm the rapid heating and expansion of the air create the thunderclap. But because sound travels slower than light, there's a gap between seeing the lightning and hearing the thunder it produced. Using Distance = speed x time, by counting the seconds from seeing the lightning you can easily estimate how far away it is.

Conveniently, the speed of sound in air is about 330 metres/second. So depending on your unit preference:

every 3s you wait the thunder travels about 1 km

every 5s you wait the thunder travels about 1 mile

Give it a try at a safe distance from your next lightning storm.

Also see: thunderclap or rumble, thunder clouds, dirty thunderstorm

Flash-to-bang method

If you’ve ever been close enough to lightning when it strikes you may be familiar with the startling high frequency thunderclap or crack it makes. But the high frequency soundwaves of the clap are attenuated by their travel through the air away from the source so that from a kilometre or so away all you hear is the growling of the thunder rumbling away as it clatters and rebounds off everywhere it hits.

I learned about this from Randall Munroe’s fun book How to: Absurd scientific advice for common real-world problems.

Thunderclap or rumble

Caused by ash and rock interacting inside a cloud instead of ice particles. As you can imagine you can get this with volcanoes which can be pretty spectacular. Here’s more about how lightning forms inside a thunder cloud, the regular kind.

Dirty thunderstorm

Thunder clouds are so impressive. Lightning forms due to air currents in the cloud as warm moist air rises up quickly. All the collisions between particles cause different charges to develop between the top and the bottom of the cloud. When that gets large enough, kapow!

Also see: thunderclap or rumble, dirty thunderstorms.

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