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EPR had a simple but powerful definition

  1. Feb 3, 2010 #1
    I have a new-b question. From Dr. Chinese's page I get this quote

    "EPR had a simple but powerful definition of what they called an "element of reality": IF an observable property of a system could be predicted with absolute certainty (100%) without disturbing that system, THEN it must correspond with an element of reality."

    My understanding is that it is impossible to measure any property without causing some amount of disturbance. At the macro scale the disturbance is small and the measure accuracy can be high. At the micro scale the disturbance is percentage wise higher and the accuracy is limited.

    Do I understand the nature of measurement wrongly?
    Last edited: Feb 3, 2010
  2. jcsd
  3. Feb 4, 2010 #2


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    Re: Epr

    Well, according to QM: the accuracy is not limited (in principle) but the nature of the "disturbance" is fundamental. The EPR question then becomes... "what IF you could predict an observable with certainty?" Would that then indicate you have seen an element of reality? Because they certainly believed such was the case, and thought they had the example to prove it.

    However you choose to construe EPR, they did not have the tools available we do today. Entanglement is routinely created in the lab, and experiments show that the "elements of reality" do not work as envisioned.
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