equivalenceperiaate

Equivalence principle, sometimes encountered in texts as equivalenceperiaate, is a foundational idea in gravitational physics. At its core, it states that local experiments cannot distinguish between uniform acceleration and a gravitational field, implying a deep link between inertia and gravity. A related formulation expresses the equality of inertial mass and gravitational mass, so objects fall with the same acceleration regardless of their composition in a given gravitational field.

There are several closely related statements. The Weak Equivalence Principle (WEP) asserts the universality of free fall: all bodies fall identically in a given gravitational field when non-gravitational forces are negligible. The Einstein Equivalence Principle (EEP) strengthens this by adding Local Lorentz Invariance and Local Position Invariance, leading to the idea that the outcome of any local non-gravitational experiment is independent of where and when it is performed or the velocity of the freely falling frame. The Strong Equivalence Principle (SEP) extends these ideas to include gravitational self-energy and the behavior of gravitating systems themselves.

Historically, the principle guided Einstein's development of general relativity, where gravity is described as the curvature of spacetime and freely falling objects follow geodesics. In practice, the equivalence principle underpins the metric description of gravity and the interpretation of gravitational phenomena.

Experimental tests have repeatedly confirmed the principle to very high precision. Eötvös-type experiments and lunar laser ranging test WEP on different scales. The MICROSCOPE space mission provided stringent limits on WEP violations. Tests of gravitational redshift, light deflection, and time delay corroborate EEP predictions and the geometric view of gravity.

Beyond general relativity, the equivalence principle remains a touchstone for theories of gravity and possible extensions. Some quantum gravity approaches explore potential small violations, making ongoing high-precision experiments important for fundamental physics.