equivalence principle

equivalence principle

Fundamental principle of physics that in its weak form states that gravitational (see gravitation) and inertial (see inertia) masses are the same. Albert Einstein's stronger version states that gravitation and acceleration are indistinguishable. It implies that the effect of gravity is removed in a suitably accelerated reference frame, such as an elevator with its cable cut, in which a person would experience free fall.

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equivalence principle [i′kwiv·ə·ləns ‚prin·sə·pəl]

(relativity)

In general relativity, the principle that the observable local effects of a gravitational field are indistinguishable from those arising from acceleration of the frame of reference. Also known as Einstein's equivalency principle; principle of equivalence.