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
Ernst Mach one another, by triggering edge-detection in the human visual system. More clearly than anyone before or since Mach made the distinction between what he called "physiological" (specifically visual) and "geometrical" spaces. Mach's views on mediating structures inspired B. F. Skinner's strongly inductive position, which paralleled Mach's in the field of psychology. In homage his name was given to: Ernst Mach Ernst Waldfried Josef Wenzel Mach (; ; 18 February 1838 – 19 February 1916) was an Austrian physicist and philosopher, noted for his contributions to physics such as study of shock waves. The ratio of one's speed to that of