Thunder and Lightning ```Name: Wildman Jackson Status: Other Age: N/A Location: N/A Country: N/A Date: N/A ``` Question: I have heard that when you hear thunder, you can count seconds, and every seven seconds represents a mile in distance of the storm from yourself. Is this an accurate measurement? Has anyone actually calculated how to tell how far a lightning bolt has struck from himself by counting seconds? Replies: If you assume that the lightning and thunder occur at the same instant, then you can calculate distance by measuring the time that it takes to hear the thunder. Just multiply time that it takes by the velocity of sound in air and you will get the distance that the sound has traveled. (the velocity of sound in dry air at 25 C is equal to 346.29 m/sec. However the velocity will vary with humidity and temperature). Bon computite. Woodford This is true because of the laws of physics. The speed of light is so fast that you see the lightning flash instantly (it only takes sunlight 8 minutes to travel all the way to Earth). But sound moves much slower. We know the speed of sound (see last reply) so speed x time = distance. Sound travels 1 mile in about five seconds and one kilometer in three seconds. "Heat lightning" is lightning from a thunderstorm that is so far away that the sound never reaches your ears. Mark Fernau Click here to return to the Environmental Science

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