In 1935, Einstein, Podolsky and Rosen constructed a thought experiment, which showed that either the quantum wave function does not provide a complete description of physical reality or measuring one particle from a quantum entangled pair instantaneously affects the second particle regardless of how far apart the two entangled particles are. In 1964, John S. Bell resolved this conundrum by proving that no completion of quantum physics with local hidden variables can ever reproduce all of the predictions of quantum mechanics. Thus, Bell's theorem allowed quantum non-locality to be tested and confirmed in actual physical experiments.