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 a Šebestová students and incorrigible urchins Horáček and Pažout, are the main antagonists of the series. Mach a Šebestová Mach a Šebestová (in English: Mach and Šebestová or Max and Sally) is a Czech cartoon series. It was created by writer Miloš Macourek, director Jaroslav Doubrava, and animator Adolf Born. The animated characters were voiced by Petr Nárožný. The story follows the adventures of two third-year pupils and a torn off telephone receiver. The first series of 13 episodes was broadcast on Czechoslovak Television in 1982. Mach a Šebestová is one of the most popular series made for children's television programme Večerníček.