Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
Mach (crater) Mach (crater) Mach is a large lunar impact crater of the class known as a walled plain. It is located on the far side of the Moon and cannot be viewed directly from the Earth. Nearby craters of note include Joule to the northeast, Mitra attached to the western outer rim, and Henyey to the southwest. This is a prominent but eroded formation with multiple craters along the rim and interior. The crater Harvey breaks across the eastern rim, and its outer rampart spills across the interior floor of Mach. The overall shape of Mach resembles a pear, with a