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Ernst Mach

Ernst Mach (February 18, 1838 - February 19, 1916) was an Austrian physicist and philosopher.

Ernst Mach was born in Chrlice (now part of Brno), Czech Republic. He was educated at home until the age of 14, then went briefly to gymnasium before entering the University of Vienna at 17. There he studied mathematics, physics and philosophy, and received a doctorate in physics in 1860. His early work was focused on Doppler effect in optics and acoustics. In 1864 he took a job as professor of mathematics in Graz, in 1866 he was also appointed as a professor of physics. During that period Mach became interested also in physiology of sensory perception. In 1867 Mach was took the chair of a professor of experimental physics at Charles University, Prague.

Most of his studies in the field of experimental physics were devoted to interference, diffraction, polarization and refraction of light in different media under external influences. These studies were soon followed by his important explorations in the field of supersonic velocity. Mach's paper on this subject was published in 1877 and correctly describes the sound effects observed during the supersonic motion of a projectile. Mach deduced and experimentally confirmed the existence of a shock wave which has the form of a cone with the projectile at the apex. The ratio of the speed of projectile to the speed of sound v/c is now called the Mach number. It plays a crucial role in aerodynamics and hydrodynamics.

In the area of sensory perception, he is best known for an optical illusion called the Mach band.

Mach returned to the University of Vienna as professor of inductive philosophy in 1895, but he suffered a stroke two years later and retired from active research in 1901, when he was appointed to the Austrian parliament. He continued to lecture and publish in retirement. Mach died on 19 February 1916 in Haar, Germany.

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