emh@bonnie.UUCP (Edward M. Hummel) (06/26/85)
>Ernst Mach was an Austrian physicist who died in 1916. I have heard of >"the Mach Principle" or "Mach's Principle" in science fiction stories, >and it seems to have something to do with FTL travel. I don't know >exactly what that is all about, but I suspect is is some >pre-relativistic notion that isn't too relevant anymore. (I'd be >delighted to find differently... anybody out there know any more about >"Mach's Principle"?) > >Ernst had nothing to do with "mach number", which is speed measured in >speed-of-sound units (a somewhat rubber measuring unit, it has always >seemed to me). I think mach is a corruption of "mark", but I beg to be >corrected if I'm wrong. >-- >Wayne Throop at Data General, RTP, NC Ernst Mach was a one of the most infuential thinkers of his time. His books on mechanics and optics were (and still are) great classics. Mach's most lasting contributions are philisophical in nature. He was a firm believer that scientists must be able to empirically prove their theories. Mach would only accept proofs that were very rigid, with the postulates verified by direct observation. He attacked the "kinetic theory of gases", since there were no observations of the "invisible molecules". To the day he died he did not believe that atoms were real. He also had problems with Newton's notion of absolute space, filled with fields that caused "actions at a distance". "Mach's principle" is essentailly philosophical in nature. It is best understood by considering the motion of a particle in empty space. Mach believed that geometrical and inertial properties are meaningless in empty space. Motion can not be measured and has no importance. To make physical sense out of particle dynamics it is necessary to have the universe with its mass distribution. Alternatively, particle dynamics is determined by the mass distribution of the universe and not by some property of absolute space. BTW, this implies that "constants" of nature should vary throughout the universe. Mach's book on mechanics was read by Einstein at an early age, and had a great impact. Perhaps it helped Einstein to take the non-Newtonian view of mechanics and space that is necessary in relativity. Special relativity starts with the rejection of "absolute motion". Mach's view that physical theories needed proof in observed phenomenon (ultra-phenomenology) was the subject of much debate during the early years of quantum theory. The so-called "Mach-Ostwald School" felt that theories which relied on hidden occurences were metaphysics. And metaphysics (as we all know?!) is bad. Mach's contributions to optics, philosophy, political theory, and psychology are mostly forgotten. His experiments with objects moving at ultra-sonic velocities led to the coining of the "Mach number" in his honor (after his death). --------------------------------- Ed Hummel ...!clyde!bonnie!emh Go ahead! Show me a quark. Make my day.