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Entanglement and time dilation

  1. Feb 22, 2016 #1
    In entanglement, two electrons have the same spins measured at the same time. But how is same time defined, in light of special relativity's time dilation?
    Doesn't this mean that, from another frame of reference, they will not be simultaneous. That means, that person in point A, knows in advance, what will be the spin in the future point B. Isn't this prediction of the future?

    In which reference frame is the measurement simultaneous?
    Last edited: Feb 22, 2016
  2. jcsd
  3. Feb 22, 2016 #2


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    Staff: Mentor

    That's not quite right. Entanglement means that if we measure the spin of one electron, we will know what would result from a spin measurement of the other electron, if and when such a measurement is performed.

    There is no requirement that the two measurements be simultaneous, and indeed it is irrelevant which one is done first. We do teh measurements in either order and when we're done we compare them and find the correlation.
  4. Feb 22, 2016 #3


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    That such could occur was actually a key premise of the 1935 EPR paper. See their discussion of "element of reality". If you want to see the paper, check out 1. from the following:

  5. Feb 22, 2016 #4
    thank you for your answers
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