I apologise in advance for my rather minimal knowledge of physics. Please assume that anything I write below is just my current understanding, and may very well be incorrect... Elementary particles decay into other elementary particles. When a a subatomic particle decays into a pair of other particles, entanglement occurs. According to special relativity, a particle accelerated to near light-speed will experience time much more slowly than a particle that is not accelerated. Let's say I have a pair of entangled particles that were generated at the same time by the decay of another particle. Let's call them X and Y. Will X and Y decay at the same time? If so, what then happens if I accelerate Y to near light speed? From the point of view of a stationary observer, do X and Y... (a) Decay at the same time (relative to the stationary observer)? (b) Last for the same length of time relative to their own inertial frame, so that Y decays after X? If (b) is true, then does that allow us to predict exactly when Y will decay? Are there suitable particles that would allow this to be done experimentally?