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I Does light exist between events?

  1. Jan 3, 2018 #1
    Does light exist between events? [mod: unapproved source]

    The above perspective will resolve a lot of paradoxes in QM. Is the above view viable or is it untenable?

    Are there any evidence to show that photons exist in flight? Are there any evidence of photon trajectories?
     
    Last edited by a moderator: Jan 3, 2018
  2. jcsd
  3. Jan 3, 2018 #2

    vanhees71

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    This is an empty question. You cannot prove the existence of anything without looking at it, and detecting light is an event (i.e., an observable fact). Of course, there is ample theoretical evidence for the fact that light (electromagnetic waves with typical wavelenths in the range our eyes are sensitive too, i.e., about 400-800nm) is there even if it's not detected. The reason are the conservation laws. For light that's energy, momentum, and angular momentum. According to QED, the best theory we have about the behavior of electromagnetic waves and their interaction with electrically charged matter, all these quantities are conserved, and that's why it's strong evidence that there is something, namely the electromagnetic wave, even if it's not interacting with a detector and observed by us. From a strictly empirical perspective, that's however no proof, but since QED is so good in describing everything observable it's hard to imagine that it's too wrong about what's not observable.
     
  4. Jan 3, 2018 #3
    @bremsstrahlung your source does not meet our guidelines. Please provide one that does or this thread will be closed.
     
  5. Jan 3, 2018 #4

    DrChinese

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    As Greg mentions, the reference is unsuitable. As to the assertion that the reference resolves any paradoxes in QM, that is quite a stretch. I would call it hand waving (and that is being kind).

    The fact is: it is already generally accepted that trying to describe the activity of photons when NOT being observed is problematic. There are experiments around that concept already. Also: our PF member A. Neumaier has pointed out that the photon lacks a position operator:

    http://www.mat.univie.ac.at/~neum/physfaq/topics/position.html

    So your speculation on the point is misplaced. What is relevant is the ability to explain what is likely to be seen in various experiments. In a powerful demonstration that photons do in fact represent discrete packets:

    http://people.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf

    If you would like to read up on the usage of the word "photon" and how that fits into QT, along with some investigation into light's unobservable properties:

    http://aporia.byu.edu/pdfs/manchak-arguments_concerning_photon_concepts.pdf
     
    Last edited by a moderator: Jan 4, 2018
  6. Jan 3, 2018 #5

    Vanadium 50

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    This problem has nothing to do with photons per se. "What can we say is happening when we are not watching it" is a question that is more philosophical than scientific, and it's a sterile philosophy. It may well be that the potato chips in the bag turn into tiny dancing pink unicorns when they are on the shelf, provided nobody is looking at them (or otherwise measuring things). Nobody can prove it's happening. Nobody can prove it's not. But it's hardly good science.
     
  7. Jan 3, 2018 #6

    vanhees71

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    My potato chips have no chance to turn into anything else than some mash in my stomach. That's an empirical fact!
     
  8. Jan 3, 2018 #7
    I think a lot of good responses have been given so we will close this speculation out.
     
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