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Why do you see lightening before you hear thunder?
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GPT-5 mini
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Lightning and thunder happen at the same time, but you see the lightning before you hear the thunder because light travels vastly faster than sound. Light moves at about 300,000,000 m/s, so the flash reaches you almost instantaneously; sound (thunder) only travels ~343 m/s, so it can take several seconds to reach you from a few kilometers away.
Quick rule of thumb: count the seconds between the flash and the thunder and divide by 3 to get the distance in kilometers (or divide by 5 for miles). If the lightning is very far away, the sound may become too weak to hear at all (this is often called “heat lightning” when you see flashes but no thunder).
Nearby strikes make a sharp crack (a shock wave from rapid heating); distant strikes sound like a low rumble because the different parts of the shock arrive spread out in time.
Quick rule of thumb: count the seconds between the flash and the thunder and divide by 3 to get the distance in kilometers (or divide by 5 for miles). If the lightning is very far away, the sound may become too weak to hear at all (this is often called “heat lightning” when you see flashes but no thunder).
Nearby strikes make a sharp crack (a shock wave from rapid heating); distant strikes sound like a low rumble because the different parts of the shock arrive spread out in time.
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