Why does thunder happen after lightning?
Quick Answer
Light travels much faster than sound, so you see the flash before you hear the boom. The lightning also superheats air, creating a shock wave that we hear as thunder.
The Full Story
Lightning produces an intensely bright flash almost instantly, but the sound from the same event travels far more slowly through air. Light moves at about 300,000 km/s, while sound in air moves at roughly 343 m/s at room temperature. The lightning channel also heats the surrounding air to tens of thousands of degrees Celsius, causing it to expand explosively and generate a pressure wave. That wave is what reaches your ears as thunder. By counting the seconds between flash and sound, you can estimate how far away the strike occurred.
Key Facts
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