Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne 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

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory