What Causes ‘Thunder’ and Why Does It Happen After Lightning?

Lightning happens first, but we hear thunder later because sound travels slower than light. Imagine you're watching a movie: the actor speaks, and then a few seconds later, the sound of their voice comes through the speakers. That’s how it feels when lightning strikes, we see it flash instantly, but the thunder takes time to reach our ears.

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Examples

A flash of lightning happens first in the sky, then a few seconds later you hear thunder rumbling from far away.
Thunder is like a delayed echo, it comes after lightning because sound takes time to travel through the air.
You see lightning strike a tree near the lake, and moments later, the thunder shakes your windows.

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Categories: Science · lightning· thunder· sound waves· weather science· acoustics