Ernst Waldfried Josef Wenzel Mach (February 18, 1838 – February 19, 1916) was a foremost proponent of positivism, a founder of the new discipline of philosophy of science, and an historian of science. He also made significant theoretical and experimental contributions to acoustics, interferometry, optics, physiology and psychology. His critique of Newtonian mechanics and advocacy of relationalism as a philosophy of space and time was an important influence on Einstein in his quest for a relativistic theory of gravity. He was a supporter of the energeticists, led by Georg Helm and Wilhelm Ostwald, according to whom energy rather than atoms was to provide the ultimate substratum of matter, but he also advocated an extreme form of phenomenalism according to which physical sciences should be expressed directly in terms of relations among sensations.
In his book Science of Mechanics (1883) Mach critically examined Newton’s arguments for the existence of absolute motion and its purported ground in absolute space. Although he never stated the principle explicitly, he made clear the view, subsequently called Mach’s principle, that centrifugal effects experienced by rotating bodies may be traced to the relative motion of such bodies relative to remote bodies – if necessary, the fixed stars. He also sought for operational definitions for other Newtonian concepts, notably mass.
Mach was born in Brno-Chrlice, Moravia. He was educated at Kremsier and at the University of Vienna. In 1867 he was appointed Professor of Experimental Physics at the Charles University, Prague, but in 1895 he returned to Vienna to take up the newly-created chair in ‘the history and philosophy of the inductive sciences’, the chair subsequently held by Ludwig Boltzmann and Moritz Schlick, from which he retired in 1901. He remained opposed to atomism until his death, long after conclusive evidence for it had emerged with the work of Einstein and Perrin on Brownian motion.