十万个为什么·科学阅读30篇（1）

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为什么先见闪电后闻雷声？

Lightning and thunder happen at almost the same instant during a storm, but we see light before hearing sound.
Light travels at 300,000 kilometers per second, while sound crawls at just 343 meters per second in air.
That huge speed difference means light reaches our eyes nearly instantly, even from several kilometers away.
Sound takes about three seconds to travel one kilometer, so counting seconds helps estimate storm distance.
A flash followed by a five-second delay means lightning struck roughly 1.7 kilometers away.
Sometimes thunder sounds like a sharp crack—this occurs when the bolt is very close and the sound hasn’t spread yet.
Rolling thunder happens when sound waves bounce off hills, buildings, and different layers of the atmosphere.
Studying lightning paths helps meteorologists improve early-warning systems for severe weather events.