Speed Of Sound

Figures from Wikipedia http://en.wikipedia.org/wiki/Speed_of_sound -

• amended to include feet/sec (fps)

 Altitude                           Temperature     m/s  km/h   fps  mph  knots

 Sea level                           15 ºC (59 ºF)  340  1225  1116  761  661

 11,000 m - 20,000 m
 (Cruising altitude of commercial   -57 ºC (-70 ºF) 295  1062   968  660  573
 jets, and first supersonic flight)

 29,000 m (Flight of X-43A)         -48 ºC (-53 ºF) 301  1083   987  673  585

Mach number is the ratio of the object's speed to the speed of sound in air (medium).

Feet per second? Pah! Join the 21st century, why don't you. :) (Incidentally, is there a real need for this page here? WikiIsNotaDictionary...)

No idea. Oddly, I found very few sites where this information was concisely and cleanly presented. I did find, interestingly, that the speed of the Earth's rotation at my latitude is approximately the speed of sound, which explains the unrelenting sonic boom where I live. Or it could just be the music from the kids down the street. So ... a bullet fired at the SpeedOfSound from my house against the Earth's rotation (due West) would essentially be standing still really fast.