Science
How does thunder work?
Thunder works as the sound of lightning: a bolt heats the air around it so fast that the air explosively expands, creating a shockwave we hear as a boom. Because light travels faster than sound, you see the flash before you hear the thunder.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how thunder works.
Step by step
- 1Lightning superheats the air to tens of thousands of degrees in an instant.
- 2The air expands explosively, creating a shockwave.
- 3That shockwave becomes the sound of thunder.
- 4Light reaches you almost instantly; sound takes about 3 seconds per kilometer.
- 5Counting the gap tells you roughly how far the lightning struck.
Frequently asked questions
- What causes thunder?
- A lightning bolt heats the surrounding air so suddenly that it expands explosively, producing a shockwave we hear as thunder.
- Why do you see lightning before hearing thunder?
- Light travels nearly a million times faster than sound, so the flash reaches you almost instantly while the boom lags behind.
- How can you tell how far away lightning is?
- Count the seconds between the flash and the thunder; sound travels about a kilometer every three seconds (a mile every five).