Observers

Discussion in 'Physics & Math' started by arfa brane, Apr 18, 2017.

  1. exchemist Valued Senior Member

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    Well no, from the context of my remarks, it should be reasonably clear that the prevalent modern view of QM is that "observation", in the sense of perception by a conscious observer, does not affect reality. What is often called "observation" in QM, e.g. when speaking of the collapse of the wave function and so forth, is really interaction with a measuring system of some kind. This is independent of whether or not a conscious observer is aware of the measurement or not.

    It is true, as you say, that all observation involves interaction. However the converse does not follow. Many interactions go unobserved, after all.
     
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  3. birch Valued Senior Member

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    It cant be just a measuring system. Sure interactions can go unobserved but just the fact you can observe with your eyes is a physical interaction with photons. This is affecting matter, however slight, because had you not observed, technically there would have been a different or unchanged state. It is like saying the room you are in is the same whether you are in or out of it. On the quantum level that is not true and even on the macro as even your very presence has altered the arrangement of matter not visible to the naked eye. You are filling up that space, for one.
     
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  5. exchemist Valued Senior Member

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    All you are saying is that there are interactions involving a conscious observer, and there are interactions without one. My point is that the QM model of reality treats both identically.
     
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  7. QuarkHead Remedial Math Student Valued Senior Member

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    Well, leaving aside the contentious idea there is such a thing as "reality", I agree.

    exchemist's training will have informed him that a quantum state is given by a state vector, which, when acted on by an operator yields a spectrum (a "bunch") of eigenvalues, each of which represents a measurement outcome for the quantum state in question.

    The way these eigenvalues are determined is immaterial
     
  8. exchemist Valued Senior Member

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    Well yes, but it does seem to me that science is trying to model physical reality, even if we all suspect it may be impossible to model it exactly accurately. If we do not think there is a reality to model, what do we think we are doing?
     
  9. DaveC426913 Valued Senior Member

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    Lots of things changed. That's what "go on" means.

    The bowl of water next to my bed is now slightly lower than 8 hours ago; there is more dust on the sill, the sun rose, etc.
     

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