Equivalence principle Guide, Meaning , Facts, Information and Description
Einstein's principle of equivalence states that the (local) effects of a gravitational field are identical in all respects to the effect of uniform acceleration. It is a central principle in the theory of general relativity.This version subsumes and explains the more limited version, which is the equivalence of graviational and inertial mass. The following measurements attempted to detect a difference between gravitational and inertial mass:
| Researcher | Method | Result |
| Isaac Newton | measure the period of pendulums of different mass but identical length | no measurable difference |
| Friedrich Wilhelm Bessel | measure the period of pendulums of different mass but identical length | no measurable difference |
| Roland von Eotvos | measure the torsion on a wire, suspending a balance beam, between two nearly identical masses under the acceleration of gravity and the rotation of the Earth | difference is less than 1 part in a billion |
These measurements were part of the basis by which Ernst Mach in the nineteenth century, in Vienna, explicitly stated that we cannot distinguish the local effects of a gravitational field (say, due to the Earth) from the effect of any other acceleration (measured say, from the star Polaris).
This principle, enunciated by Albert Einstein, 1907 as the equivalence of gravitational and inertial mass, is a central tenet of his theory of general relativity.
Some immediate consequences of this are
- that light rays will appear bent in a gravitational field. The Einstein field equation predicts, for example, that a light ray will deflect toward the sun by 1.75 arc-seconds.
- and that time will move slower in a gravitational well.
See also
Steven Weinberg Gravitation and Cosmology ISBN 0-471-92567-5, pp. 188-190 (for bending of light in a gravitational field), 342-348 (for time dilation during gravitational collapse).This is an Article on Equivalence principle. Page Contains Information, Facts Details or Explanation Guide About Equivalence principle