Ernst Mach, Austrian physicist and philosopher, c 1910.
© Science Museum / Science & Society Picture Library
Photogravure after a photograph by Charles Scolik. Mach (1838-1916) was born in Turas, Austria and attended Vienna University, later becoming profesor of mathematics at Graz University (1864-67), and of physics at Prague (1867-95) and Vienna Universities (1895-1901). He contributed to the development of several branches of physics including optics, mechanics and wave dynamics. His name has been given to the unit of velocity which expreses the speed of matter relative to the speed of sound at a certain temperature (Mach number), and to the angle of a shock wave to the direction of motion (Mach angle). In 1901 he was made a member of the Austrian House of Peers. From a collection of portraits of scientists published by Photographische Gesellschaft, Berlin, c 1910.