Ernst Mach of experimental physics concentrated on the interference, diffraction, polarization and refraction of light in different media under external influences. From there followed important explorations in the field of supersonic fluid mechanics. Mach and physicist-photographer Peter Salcher presented their paper on this subject in 1887; it correctly describes the sound effects observed during the supersonic motion of a projectile. They deduced and experimentally confirmed the existence of a shock wave of conical shape, with the projectile at the apex. The ratio of the speed of a fluid to the local speed of sound "v"/"v" is now called the Mach number. It
Mach (crater) Mach (crater) Mach is a large lunar impact crater of the class known as a walled plain. It is located on the far side of the Moon and cannot be viewed directly from the Earth. Nearby craters of note include Joule to the northeast, Mitra attached to the western outer rim, and Henyey to the southwest. This is a prominent but eroded formation with multiple craters along the rim and interior. The crater Harvey breaks across the eastern rim, and its outer rampart spills across the interior floor of Mach. The overall shape of Mach resembles a pear, with a