Einstein-Podolsky-Rosen paradox: quantum mechanics says that once 2 particles have been near each other, they continue to instantaneously affect each other no matter how widely they may be separated (thus, quantum mechanics requires synchronicity!). Einstein posited "hidden variables", but this was disproved in 1982. Quantum uncertainty predicts correlation that makes it look as if the 2 particles are communicating by telepathy, since the particles act in harmony even though they cannot exchange signals fast enough to causally organize their harmony.