# Can time dilation occur between entangled particles?

If two particles are entangled, with one moving near the speed of light relative to the other, would observing one tell us something about the other in the other's future or past?

• In the classical EPR experiment we have two photons moving even at the speed of light relative to each other, in the opposite directions. So measuring the momentum of one tells us the momentum of the other. – Conifold Jun 21 '17 at 1:44