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 Five of his father's motor company). In the 1993 American remake, the design was completely changed. Its name probably derives from the fact that speeds above Mach 5 are known as hypersonic. However, the Mach Five cannot reach Mach speeds. The name is also a pun in two languages: the word for "five" in Japanese is "go". However, the "go" used for the car's name is a suffix attached to the names of ships, etc. Thus, the car is known in the Japanese version as simply the "Mach". Actual race cars that closely resemble the Mach Five are the 1966 Japanese