Mach, Ernst
Mach, Ernst (1838-1916), an Austrian physicist and philosopher. He made important studies of projectiles moving at supersonic speeds. The ratio between the speed of a flying object and the speed of sound in the surrounding air is called the Mach number in his honor. (An object at Mach 1 is traveling at the speed of sound, at Mach 2 twice the speed of sound, etc. This speed decreases as the temperature of the air decreases.)
Mach tried to free science from all metaphysical concepts, influencing such philosophers as William James and Bertrand Rusell.
Mach was born in Moravia, now a part of the Czech Republic. He received his Ph.D. from the University of Vienna in 1860. Mach was professor of physics at the University of Graz, 1864-67; at the University of Prague, 1867-95; and at Vienna, 1895-1901. He wrote The Science of Mechanics (1883) and The Analysis of Sensations (1886).