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Mach's principle

Mach's principle is a suggestion put forward by the German philosopher Ernst Mach in 1893 according to which the inertial effects of mass are not an innate property of a body, but instead are the result of the effect of all the other matter in the universe. In other words, it postulates that the local behavior of matter is influenced by the global properties of the universe. More specifically, Mach's principle claims that it is not absolute acceleration, but the acceleration relative to the center of mass of the universe, which determine the inertial properties of matter. If a body is accelerated with respect to the total mass of the universe, it experiences "forces" such as centrifugal and centripetal force. Mach's principle, however, does not offer an explanation of how the matter in the rest of the universe influences the inertial properties of of the body.

Mach's Principle was brought to widespread attention by Albert Einstein, and undoubtedly played some role as Einstein formulated his general theory of relativity (GR). However, the principle is now known to be incompatible with GR.

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