Changes

The sound produced as a result of aircraft traveling at or above Mach 1.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>

The sound produced as a result of aircraft traveling at or above Mach 1<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> or indeed, when any object breaks the [[sound barrier]]. It used to be thought that the cracking noise of a [[whip]] was due to leather striking leather but, after using high speed [[photography]] to study the motion of the whip, it was discovered that the crack is actually the tip of the whip breaking the sound barrier.

==References==

==References==

<references/>

<references/>