Silent thunder bends up
I see lightning but often don't hear thunder. Why is there no thunder?
Arno R., Albuquerque, New Mexico
You hear no thunder, if you are more than fifteen miles away, because the sound bends upward and misses you. Also thunderstorms
are chaotic maelstroms that disorganize and dissipate sound waves before the thunder sound can reach you.
 The sound wave bends up about 15 miles from the lightning and the man hears
no thunder, but the closer woman jumps in fright.
Sound waves bend when parts of the wave fronts travel at different speeds. This happens when the sound travels through air of different
temperatures or in uneven winds. Thunderstorms tower up to fifteen miles high and reach through a gradient of winds and temperatures.
The speed of sound is faster in warmer air. Usually air is warmer near the
ground and therefore sound travels faster there. Consider just one sound wave.
The part near the warmer ground outruns the part higher in the cooler sky and
the wave bends up.
Uneven winds also bend sound waves like uneven temperature does. Uneven temperatures and winds work together to rob you the sound of thunder.
(Answered by April Holladay, science correspondent, January 30, 2002)
Further Reading:
Hewitt, Paul, Conceptual Physics, Little, Brown, and Company, Boston (1998)
Walker, Jearl, The Flying Circus of Physics, John Wily & Sons, New York (1977)
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