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Regarding the observer effect.

  1. Sep 23, 2009 #1
    I got a question. Is this excerpt from wikipedia correct?

    http://en.wikipedia.org/wiki/Observer_effect_(physics [Broken])

    Does that mean there is no observer effect when acts of observation and measurement are defined in quantum terms?

    Does anyone have sources that augment or dispute this excerpt?

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 23, 2009 #2


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    A measurement is an interaction between the system and its environment (which includes the measurement device), so the state of the system can obviously be changed by the measurement.

    So this "observer effect" (as defined by the article) is clearly present in QM, but no one uses that term. I don't remember seeing it in any of the QM books I've read.

    It's true that the measurement device obeys the rules of QM, but in realistic situations, the interactions between the device and its environment will ensure that the "pointer" (the component that indicates the result of the measurement) behaves in a way that's indistinguishable from classical behavior. In fact, if it behaved in any other way, we wouldn't consider it a measurement.
  4. Sep 23, 2009 #3
    I see. So the excerpt isn't necessarily wrong? In other words, is it open to interpretation.
  5. Sep 23, 2009 #4

    D H

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    The excerpt is not particularly well written and puts the emphasis on the wrong syLLAble. IMO, the paragraph on the uncertainty principle should have been first and foremost. The lay misinterpretation of the uncertainty principle is that it is the observer effect. This interpretation misses the mark in that the uncertainty principle talks about the uncertainty in a canonical pair of variables. http://en.wikipedia.org/wiki/Uncertainty_principle" [Broken] says it much better (emphasis mine):
    Last edited by a moderator: May 4, 2017
  6. Sep 23, 2009 #5
    Does that mean the term, the observer effect is used? I understand that the phenomena exists, but I haven't seen many academic sources using the term. However I've heard the term used in journals outside QM, though.
  7. Sep 23, 2009 #6


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    No, it it not used at all as far as I know.
    Although presumably you could across is it or something similar if you were reading academic paper that deals with the "philosophy" of QM and modern physics (and I don't mean interpretations but really philosophy), but that is not really physics (or science).
  8. Sep 23, 2009 #7
    Interpretations are really philosophy. "Observer effect" isn't a technical philosophical term I've ever come across before though.

    For examples of academic philosophy on QM see any of the papers on http://www.princeton.edu/~hhalvors/papers/.
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