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A Question On Entanglement

  1. May 26, 2011 #1
    I watched a recent documentry regarding the recent time travel experiments using two devices. A basic explanation:

    Device A sends a photon which device B recieves, device B however recieves the message before Device A sends it.

    My question regarding this is:

    If device B recieves the photon before the message is sent, then what happens if you switch off Device A during the period between Device B recieving the message and Device A sending it?

    If device B still actually recieves the message, but device A is unable to send it then could we be looking at a parrallel universe sending the message in the first place?

    Indeed, could this be an experiment for testing for a parallel universe. For if device A is unable to send the message (it is switched off), then how on earth can device B recieve it?

    Thanks for your thoughts.
    Last edited: May 26, 2011
  2. jcsd
  3. May 26, 2011 #2
    Yes, the "multiverse" suggests that at each "multiple choice" situation the universe splits into as many new universes as needed for all possibilities to occur. I think the multiverse concept if needed only if you insist that time exists as it appears to us, always going forward, like a water stream.

    If you accept that the future and the past exist "simultaneously," constantly evolving but NOT necessarily with time, then maybe the mulitverse is no longer necessary. It's our perception of time that is the problem.

    For example, everyone talks about "the present" as if it were something that actually exists, which it doesn't. How long is "the present?" A second? A nanosecond? Plank's constant? Or none of the above?

    The very basis of Newtonian physics lies in predictability, IMO. The predictability goes in both forward and backwards in time, also called determinism.

    Einstein literally spent decades trying to think up experiments that would prove QM was incomplete because he couldn't accept a Universe that was NOT determinate. He couldn't do it.

    It's certainly possible that QM is beyond the ability of humans to understand even in small part, yet some physicists far smarter than me suggest that we actually create the universe by being observer/participants.
  4. May 26, 2011 #3


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    There are no cases in which a photon is detected before it is created. There are situations in which photons become entangled after they are detected. However, no information is transmitted from the future to the past in this case. See middle of page 5:

  5. May 26, 2011 #4
    Actually the notion that a photon is "created" is incorrect. The universe started out with a certain amount of energy and that energy is continuously changing form. That's why Feynman diagrams are useful imagery tools.

    A photon which is "detected" no longer exists, if you accept the notion that time always flows forward, which is debatable.

    On the subatomic level, if you do an experiment meant to detect wave-like properties you detect wave-like properties. If you do an experiment meant to detect particle-like properties you detect particle-like properties. It shouldn't come as a surprise that if you do an experiment to detect "entanglement" properties you do indeed detect entanglement properties.

    Every time a question is answered in physics, IMO, the nature of reality becomes even more weird.
  6. May 26, 2011 #5


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    By the way, welcome to PhysicsForums!
  7. May 26, 2011 #6
    Thank you, I love physics.
    It's fun of delicious paradoxes that are fun to argue about.
  8. May 26, 2011 #7


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    So fun you gotta say it twice!:wink:
  9. May 27, 2011 #8
    Ya got me on that one.
    I gotta check my grammar more carefully.
    I mangled that one rather badly.
    The first "fun" should have been "full."
    Unfortunately, my brain speed exceeds my typing speed.
  10. May 27, 2011 #9
    I do love that tho.. Alpha->Omega=(Alpha/Omega/Alpha/...).
  11. May 27, 2011 #10


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    Just a little Freudian slip... shows how fun it really is.
  12. May 27, 2011 #11
    Good one. :rofl:
    My Psych prof once wrote Frued on the blackboard.
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