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
GNU Mach GNU Mach GNU Mach is an implementation of the Mach microkernel. It is the default microkernel in the GNU Hurd. GNU Mach runs on IA-32 machines. GNU Mach is maintained by developers on the GNU project. It is distributed under the terms of the GNU General Public License (GPL). Early versions of the Hurd were developed on top of CMU's Mach 3.0. In 1994, CMU stopped working on Mach, and the GNU Project switched to the University of Utah's Mach 4. The kernel known as "GNU Mach" was derived from Mach 4 once Utah stopped development. The first ChangeLog entry