Experiments in which entangled particles are measured whilst they are separated by considerable distance have demonstrated beyond all reasonable doubt that quantum behaviour is not limited by the speed of light. The effect of measuring one particle is exhibited by the particle with which it is entangled long before light has had time to travel between them. Experiments have demonstrated that the communication is as good as instantaneous, even when the particles are 400 kilometres apart.
Given that non-locality is a fact, General Relativity cannot be completely true. However, scientists have no idea as to the physical mechanism by means of which the particles communicate. Quantum Mechanics says that they must, and experiments demonstrate that they do, but nobody has a clue as to how. How do particles which are separated by large distances manage to affect each other?