longitudinal waves

Waves: Moving Without Going Anywhere

drorzel | August 19, 2010

At the tail end of Tuesday's post about wind and temperature, I asked a "vaguely related fun bonus question:" If the air molecules that surround us are moving at 500 m/s anyway, why isn't the speed of sound more like 500 m/s than 300 m/s? This is another one that people are sometimes surprised by. The answer is simply that in a sound wave, the air molecules don't really go anywhere. When something creates a sound-- say a foolish dog barking at a perfectly harmless jogger going by outside, to choose an example completely at random-- there isn't any actual thing that travels from the noisy dog…