What is the equivalence principle in physics?
Quick Answer
The equivalence principle says that locally, the effects of gravity are indistinguishable from acceleration. It is a cornerstone of Einstein’s theory of general relativity.
The Full Story
The equivalence principle is the idea that being in a closed elevator in free fall feels the same as being weightless in deep space, at least locally. Einstein used this insight to develop general relativity, which treats gravity as the curvature of spacetime rather than a conventional force. The principle also predicts that all objects fall with the same acceleration in a vacuum if air resistance is absent. Galileo’s famous experiments and later precision tests, including those using torsion balances and satellites, have confirmed it to extraordinary accuracy. It remains one of the most important concepts in modern gravitational physics.
Key Facts
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