Einstein’s Equivalence Principle

Einstein’s Equivalence Principle states that locally, the effects of gravity are indistinguishable from acceleration. In other words, if you're in a sealed, windowless room, you couldn’t tell whether a force you feel is due to gravity or your room accelerating upward. This means gravity and acceleration are fundamentally linked, leading to the idea that gravity is curvature of spacetime. This principle is foundational to Einstein’s theory of General Relativity, describing how gravity works not as a force but as objects following curved paths in a four-dimensional fabric of spacetime.