Moravian scientist who was strongly influenced by Fechner, the physicist-turned-philosopher who unsuccessfully tried to found the science of "psychophysics". The basis of Mach's natural philosophy was that all knowledge is a matter of sensations, so that what people call "laws of nature" are only summaries of experience provided by their own fallible senses. The ratio of a body's speed to the speed of sound is known as the Mach number.