| − | Any speed that is faster than the speed of sound in the substance of interest.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref>
| + | <big><big><big><big><big><big><big><big><big><big><big>Icewed<!-- -->ge</big></big></big></big></big></big></big></big></big></big></big> |