Answer card
What makes thunder?
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What we know
- True: Lightning heats the air it passes through: “The temperature of the air in the lightning channel may reach as high as 50,000 degrees Fahrenheit, 5 times hotter than the surface of the sun.” National Weather Service — Understanding Lightning: Thunder
- True: The hot air expands very fast and then cools and shrinks. “This rapid expansion and contraction creates the sound wave that we hear as thunder.” National Weather Service — Understanding Lightning: Thunder
- True: “If you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you’ll get the distance in miles to the lightning.” (Divide by 3 for kilometres.) National Weather Service — Understanding Lightning: Thunder
- True: “If the thunder sounds more like a rumble, the lightning was at least several miles away.” National Weather Service — Understanding Lightning: Thunder
What we made simpler
The 50,000 °F is the top of a range: other weather scientists give lower figures for some flashes. Counting seconds gives an estimate, because sound travels at different speeds in warm and cold air.
Still open
Exactly how lightning starts inside a cloud is still being studied.
Next why
Why do we see the lightning before we hear the thunder?
WaveForge — Sound Basics →Try it
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