EPR has been a thorn in the side of Quantum Mechanics since Einstein's team devised the thought experiment. An atom emits two photons in diametrical directions. One photon spins CW. The other spins CCW. When the first photon is compelled to reverse its spin, the other one instantly reverses its spin as well.
The Quantum mathematicians have come up with ridiculous explanations for EPR over the years, including hidden variables, many worlds, and particles that come from the future.
