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Thread: What is a quantum observer?

  1. #31
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    Quote Originally Posted by damian1727 View Post
    huh?
    The question was about the observer. If you aren't there, then it doesn't mean it doesn't happen. There is no wave to collapse just by your god-like observation of it.

    If the cat is in the box.. it is alive or dead.... period...whether you look or not.

  2. #32
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    Quote Originally Posted by EvilEye View Post
    But we aren't the final arbiters of reality either.
    Sure we are. "Reality" is our word, after all. There is nothing you and I can discuss that we are not the "final arbiters" of.

    Scientifically... True Reality is what happens regardless of what we think. Our own reality is created and destroyed by experience.
    But science is ours, so scientifically, true reality is whatever we define it to be. A useful definition will require that we not be tyrants, however, I'll grant you that.

  3. #33
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    (Title)
    Somebody who observes quantums, duh! ;-)
    The greatest journey of all time, for all to see
    Every mission makes our dreams reality
    And our destiny begins with you and me
    Through all space and time, the achievement of mankind
    As we sail the sea of discovery, on heroes’ wings we fly!

  4. #34
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    Quote Originally Posted by Ken G View Post
    Sure we are. "Reality" is our word, after all. There is nothing you and I can discuss that we are not the "final arbiters" of.

    But science is ours, so scientifically, true reality is whatever we define it to be. A useful definition will require that we not be tyrants, however, I'll grant you that.
    That is philosophy too.

    Does the world end when I die?

    Ask George Washington.

  5. #35
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    Quote Originally Posted by EvilEye View Post
    That is philosophy too.
    Actually, it isn't. It's just applying the definitions of the words.
    Does the world end when I die?
    That's irrelevant, we are not talking about you, we are talking about science and reality. And yes, human science would end if all humans and all traces of our writings on science die, as would whatever have been all our concepts of what reality is. If you are asking about real reality, rather than our concept of reality, then you are talking nonsense, because the only thing we can have a conversation about is our concept of reality-- and that's not philosophy, it's fact.

    I think what you are actually saying is that our concept of reality is connected with our ability to imagine something that exists outside of our imagining it. This model of reality works great, passes most of the tests we give it, and will be gone with us-- unless some nonhuman intelligence is also using it (which they likely are).

  6. #36
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    Quote Originally Posted by Ken G View Post
    Actually, it isn't. It's just applying the definitions of the words.
    That's irrelevant, we are not talking about you, we are talking about science and reality. And yes, human science would end if all humans and all traces of our writings on science die, as would whatever have been all our concepts of what reality is. If you are asking about real reality, rather than our concept of reality, then you are talking nonsense, because the only thing we can have a conversation about is our concept of reality-- and that's not philosophy, it's fact.

    I think what you are actually saying is that our concept of reality is connected with our ability to imagine something that exists outside of our imagining it. This model of reality works great, passes most of the tests we give it, and will be gone with us-- unless some nonhuman intelligence is also using it (which they likely are).


    I'm sorry. But I have a problem with injecting myself into reality.

    **** happens whether I am there or not.

  7. #37
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    he's got it on camera....

  8. #38
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    Quote Originally Posted by EvilEye View Post
    I'm sorry. But I have a problem with injecting myself into reality.

    **** happens whether I am there or not.
    That is certainly the standard for our model of reality, to within certain "probability" related nuances.

  9. #39
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    in the double slit experiment tho very DIFFERENT **** happens if you are not there....

    ie you get an interference pattern and the photons seem to go thro both slits..

    even if you measure AFTER the slits it effects what the photon does at the slit...

    as for the cat (even tho i think dechonherence explains why it is one or the other)
    it is not something that can just be easily swept under the carpet as obvious..

  10. #40
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    electrons never ''jump'' energy levels whilst observed.....a watched kettle really does never boil...


    lol

  11. #41
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    Then the original question should be what happens to an obsrever of quantum physics.

    Because the quatum world doesn't work the same way at our scale.

    I will never, by chance, fall up out of bed.

  12. #42
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    or at least it very unlikely

  13. #43
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    Down Under, we fall up out of bed all the time.

  14. #44
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    oof... my typing was horrible up there.

    Sorry.

  15. #45
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    don t worry mine is always awful i cant speel atall

  16. #46
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    Quote Originally Posted by EvilEye View Post
    That is philosophy too.
    Here's what wikipedia has to say about reality:

    In the strict sense of philosophy, there are levels or gradation to the nature and conception of reality. These levels include, from the most subjective to the most rigorous: phenomenological reality, truth, fact, and axiom.
    Imagination, on the other hand, is part of how we make sense of what we perceive:

    Imagination is the ability to form mental images, or the ability to spontaneously generate images within one's own mind. It helps provide meaning to experience and understanding to knowledge; it is a fundamental facility through which people make sense of the world
    ...it also plays a key role in the learning process.

  17. #47
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    Quote Originally Posted by damian1727 View Post
    in the double slit experiment tho very DIFFERENT **** happens if you are not there....
    This is a common misconception about quantum mechanics. But if you look at the theory, the predictions depend only on the experimental setup, and are obtained entirely in a scheme that does not require my presence in the equations-- it only needs to me to see if I was right.
    ie you get an interference pattern and the photons seem to go thro both slits..
    That is controlled by the experimental setup, not my presence.
    even if you measure AFTER the slits it effects what the photon does at the slit...
    That statement may or may not be correct depending on how certain key words are intepreted, but taken at face value it sounds like a common misconception about "delayed choice quantum erasure". Half the articles I see on that topic make steam come out of my ears, because I know they are feeding that false impression. Nothing that an experimental setup does later can alter the correct prediction of a prior outcome. It is only our interpretation of when things happen that tends to be faulty-- our intuition about causality, not causality itself.
    as for the cat (even tho i think dechonherence explains why it is one or the other)
    it is not something that can just be easily swept under the carpet as obvious..
    Certainly there is nothing obvious about it. But the role of the observer in quantum mechanics is way oversold-- the real issue is the role of the observer in all of science. Science is manifestly an intellectual organization of the interaction between an observer and his/her environment, and that is as true in Newtonian mechanics as in quantum physics. It is only the people who mistake their science for "what is really happening" that run into philosophical conundrums, and not surprisingly-- logically, the use of a false premise will tend to do that.

  18. #48
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    That statement may or may not be correct depending on how certain key words are intepreted, but taken at face value it sounds like a common misconception about "delayed choice quantum erasure". Half the articles I see on that topic make steam come out of my ears, because I know they are feeding that false impression. Nothing that an experimental setup does later can alter the correct prediction of a prior outcome. It is only our interpretation of when things happen that tends to be faulty-- our intuition about causality, not causality itself.
    Quote:



    could you explain a bit?

    as i understand it if you know the path the pattern goes....

    if you measure after the slits ie know the path the pattern goes...seeming to suggest that the photon took one slit or the other....tho it does hit the detector after...

    i get very confused with all those mirrors...

    please dont misunderstand me i am not into this whole observer thing and completly agree that it depends on the experimental set up...

    tho why the 2 different results exist?

    i must also admit to not being smart enough to have a problem with the role of observers in science...i'll leaver that to philosophers....nmp

  19. #49
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  20. #50
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    Quote Originally Posted by damian1727 View Post
    as i understand it if you know the path the pattern goes....
    Correct.
    tho why the 2 different results exist?
    It's all about interference. Basically, the things that happen receive contribution from all the ways they can happen, and the different ways don't add normally, they don't simply accumulate they interfere. Your knowledge of the situation can allow you to rule out certain contributions, thereby destroying the interference. The interaction is physical, so occurs even if you don't use the information, that's where the setup comes in. But there's no need for any backward causality in time, and efforts to include it usually are more ungainly than the classical notions they attempt to resuscitate.

  21. #51
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    mmm

    thanks

  22. #52
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    Question The Observer changes the outcome

    From what I have read, at the quantum level, the smaller particles (I use this term loosely) when observed (ie electrons) are affected by the interaction of the particles used (ie photons) so that the whole experiment is pretty much stuffed from the very beginning. As the electrons, in theory, will act differently when not "watched" then when they are observed. Also, hasn't it been theorised that the more you confine your region of observation the more energetic the particles become which again changes the whole outcome.

    Therefore, doesn't the observer change the outcome?

  23. #53
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    Quote Originally Posted by Clegrand View Post
    From what I have read, at the quantum level, the smaller particles (I use this term loosely) when observed (ie electrons) are affected by the interaction of the particles used (ie photons) so that the whole experiment is pretty much stuffed from the very beginning. As the electrons, in theory, will act differently when not "watched" then when they are observed. Also, hasn't it been theorised that the more you confine your region of observation the more energetic the particles become which again changes the whole outcome.

    Therefore, doesn't the observer change the outcome?
    For some reason this whole idea reminds me of the Gary Larson (Far Side) comic, where the cows are all standing around smoking cigarettes, until a car comes over the hill, and they all drop down and start eating grass.

  24. #54
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    Wink

    LOL
    Nah, a better analogy is the movie Cats and Dogs where they are actually special agents that just act like regular cats and dogs when a poor unsuspecting human comes by

  25. #55
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    Quote Originally Posted by Clegrand View Post
    From what I have read, at the quantum level, the smaller particles (I use this term loosely) when observed (ie electrons) are affected by the interaction of the particles used (ie photons) so that the whole experiment is pretty much stuffed from the very beginning.
    This is true, but it is often said in very misleading ways. The whole point of a measurement is to bring a quantum system into contact with something we already understand, and that always means a system we can rely on to behave classically. So we are intentionally mucking with the quantum system when we measure it, it's not surprising at all. It is like translating a poem from a language we don't understand to one we do-- and then being surprised the translation has a somewhat different impact than the original.
    As the electrons, in theory, will act differently when not "watched" then when they are observed.
    We have no idea how electrons behave when "not watched", what we do is figure out what they do by watching them. We have no language to even discuss what they do if we can't watch them-- the watching can be (and often is) hypothetical, but the very language we use presumes said "watching". That's where a lot of people get hung up on "tree falling in the woods" issues, but the interesting issues persist even if you imagine a hypothetical observer. What language will you use to describe such a hypothetical interaction, other than the same language you use for the "real" one?
    Also, hasn't it been theorised that the more you confine your region of observation the more energetic the particles become which again changes the whole outcome.
    Yes, that's the "Heisenberg uncertainty principle" and is well established. What is not well established is how to interpret this effect.
    Therefore, doesn't the observer change the outcome?
    I would not so much say the observer "changes" the outcome, as the observer defines the outcome. Observation is a very purposeful classical intervention into quantum behavior, there are no observations that are counterexamples. I believe this is more or less what Bohr called "complementarity" between quantum and classical realms.

  26. #56
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    Quote Originally Posted by EvilEye View Post
    For some reason this whole idea reminds me of the Gary Larson (Far Side) comic, where the cows are all standing around smoking cigarettes, until a car comes over the hill, and they all drop down and start eating grass.
    I believe that's the lighter side of the "principle of complementarity" in a nutshell!

  27. #57
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    Quote Originally Posted by Ken G View Post
    I believe that's the lighter side of the "principle of complementarity" in a nutshell!
    Just for the un-schooled -
    complementarity principle
    From: The Columbia Encyclopedia, Sixth Edition | Date: 2007
    The Columbia Encyclopedia, Sixth Edition

    complementarity principle physical principle enunciated by Niels Bohr in 1928 stating that certain physical concepts are complementary. If two concepts are complementary, an experiment that clearly illustrates one concept will obscure the other complementary one. For example, an experiment that illustrates the particle properties of light will not show any of the wave properties of light. This principle also implies that only certain kinds of information can be gained in a particular experiment. Some other information that is equally important cannot be measured simultaneously and is lost.

    Bibliography: See W. Heisenberg, The Physical Principles of the Quantum Theory (1930, repr. 1949); N. Bohr, Atomic Physics and Human Knowledge (1958); B. L. Cline, Men Who Made a New Physics: Physicists and the Quantum Theory (1987).

  28. #58
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    Thanks for your refinement of my previous posting Ken G and Evil Eye,

    I particularly liked the "observer defines the outcome" point that Ken G made.

    One wonder's that when the notions of today are "translated" as Ken G's poetry, by future scientists, will they also have a misleading impact?

  29. #59
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    Quote Originally Posted by Clegrand View Post
    One wonder's that when the notions of today are "translated" as Ken G's poetry, by future scientists, will they also have a misleading impact?
    I suppose that depends on if our science has reached a level that is qualitatively different from the science of the ancients that we sometimes dismiss as naive and lacking in modern sophistication. I don't know, but frankly I wouldn't be surprised if science a thousand years from now wrinkles its nose at us in a very similar way. To some degree, I'd like to believe that-- but not as much as I'd like to be a fly on that wall.

  30. #60
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    Lot's of words are being bandied around on the question of what a quantum obserever is. There's a simple answer that some of the contributors to this thread have offered, but they're mixed in with a lot of distracting and somewhat misguided efforts. I'll offer my own, which I believe has merit because it's as basic as possible. It's also concise, dispensing with a lot of distracting details:

    In quantum mechanics, the positions of material objects are represented by mathematical expressions called "wave functons." A wave function has a numerical value at every point in the region of space in which the object has any chance of being found. That valueis a measure of the probability that an observation will find the object at that point. That region of space is called the "configuration space" for that object. The quantum observer is the hypothetical person who looks for the object.

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