Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
Mach a Šebestová 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. The cartoon was adapted for the film "Mach, Šebestová a kouzelné sluchátko" (Max, Sally