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Mach, Ernst

speed science professor mach’s

[mahkh] (1838–1916) Austrian theoretical physicist: fundamentally reappraised the philosophy of science; ‘the father of logical positivism’.

Mach was mainly educated at home until age 15, but later studied at Vienna. There he became interested in the psychology of perception as well as in physics. An appointment as professor of mathematics at Graz followed (1864), and he later moved to Prague (1867) as professor of experimental physics and to Vienna in 1895 as a professor of philosophy. A slight stroke in 1897 caused partial paralysis and he had to retire from the university in 1901. Thereafter for 12 years he was a member of the upper chamber of the Austrian parliament.

The theme of Mach’s work was his belief that science, partly for historical reasons, contained abstract and untestable models and concepts, and that science should discard anything that was not observable. Mach argued that all information about the world comes through sensations, and that the world consists of data; that which may not be sensed is meaningless. A historical view of science also convinced Mach that discoveries are made in many ways, not particularly related to the scientific method, and that accidents and intuition play a role. Mach influenced the authors of quantum mechanics, particularly the ‘Copenhagen’ school of , and the theory sharply distinguishes between observable quantities and the abstract mathematical wavefunction from which it is derived and which has a higher information content. Mach and his book Mechanics (1863) greatly influenced . What is now known as Mach’s principle states that a body has no inertial mass in a universe in which no other mass or bodies are present, as inertia depends on the relationship of one body to another. Einstein’s efforts to put this on a sound footing led to his theory of relativity. This result was not to Mach’s liking and he rejected it.

Mach also did some experimental work, and investigated vision, hearing, optics and wave phenomena. In 1887 he published photographs of projectiles in flight showing the accompanying shock waves; he found that at the speed of sound the flow of a gas changes character. In supersonic flow, the Mach angle is that between the direction of motion of a body and the shock wave. In 1929 the Mach number was named as the ratio of the projectile speed to the speed of sound in the same medium. At Mach 1, speed is sonic; below Mach 1, it is subsonic; above Mach 1, it is supersonic.

Machiavelli, Niccolò (1469–1527) - BIOGRAPHY, CRITICAL RECEPTION [next] [back] Macewen, Sir William

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