Einstein-Podolsky-Rosen Argument

The Einstein-Podolsky-Rosen (EPR) argument questions whether quantum mechanics provides a complete description of reality. They considered a pair of particles linked so that measuring one instantly reveals the state of the other, no matter the distance. This "spooky action" suggested either information travels faster than light, conflicting with relativity, or quantum mechanics is incomplete. They argued that there must be hidden variables—unseen factors determining outcomes—that quantum theory doesn't account for. Their work sparked debates about the nature of reality, locality, and whether a more complete theory underlies quantum mechanics.