EPR thought experiment

The EPR paradox, proposed by Einstein, Podolsky, and Rosen in 1935, questioned the completeness of quantum mechanics. They argued that if quantum mechanics is correct, it must be incomplete because it doesn't fully describe reality.12

The paradox centers on entangled particles, like electrons, which remain correlated even when separated by vast distances. If you measure a property of one particle, you can instantly know the corresponding property of the other, regardless of the distance between them. This suggests that either the particles have predetermined properties (hidden variables) or that there's a non-local connection, violating the principle that nothing can travel faster than light. Experiments have shown that Bell's inequality is violated, supporting the idea of nonlocality in quantum mechanics.312