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I got this photo during our visit to White Sands, and used the sound of the thunder with the Flash/Bang method to determine that the bolt was about two miles away. How does lightning produce thunder?

Answer:

The boom of thunder is the result of expanding air. Anytime air expands rapidly, we hear a loud sound. This is true for a popped balloon, a firecracker, a gun shot, and many other bangs and booms.

As the lightning bolt passes through the air, it heats the air to as much as 60,000° F, in a fraction of a second. When air is heated, it expands, and when it is heated rapidly, it expands rapidly. The expanding air pushes on the air around it, causing a wave of compression to move outwards. When that wave hits your ear drum, the ear drum is vibrated, and you hear the sound of thunder.

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