What Causes ‘Thunder’ After a Flash of Light?

Lightning is super fast, but thunder is slower. When lightning strikes the sky, it lights up everything around you almost instantly, that's why you see it first. But the sound from the lightning takes longer to reach your ears because sound moves much more slowly than light does. So even though the lightning happens at the same time, you hear the thunder a little later.

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Examples

  1. You see lightning, then a few seconds later you hear thunder.
  2. A storm is far away, so it takes longer for the thunder to reach your ears.
  3. Sometimes thunder sounds like a loud boom or even multiple booms.

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