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B The reality of photons (real vs virtual etc)

  1. Jun 11, 2018 #1
    I mean there is this division between virtual (in static situations) and real photons as the quanta of the EM field, but aren't all photons essentially "virtual" in the sense that they are purely made up by us in order to explain why we see discrete impacts of specific energy for a given EM field on a given target etc?

    What I want to ask by this is that for the elementary particles like electrons and protons/neutrons we can "see" them in more ways (cloud chambers etc) than we can see photons and for photons I assume we really don't have any real mechanism to "see" their existence at all apart from noticing the changes that happen when certain energy/frequency EM field is present within an area?

    PS. I do realize virtual photons are just an expression to describe situation of a static EM field versus normal photons that describe a dynamic EM field which can transfer energy.

    Would it be fair to say that excluding the fact that it is all around us and we have learned the working principle of the EM field, it's basics or whatever makes it up in the first place is just as much of a mystery to us as dark matter or dark energy?
    Yet we don't say "dark EM field" but we say dark matter, but we do know some things about dark matter don't we? So in a sense we also know some things about the EM field and some others we simply can't know, where is the line between calling something solved and calling something "dark" given the fact that in physics many times certain aspects work the way they do without us having a real physical way of understanding the reasons behind that?
  2. jcsd
  3. Jun 11, 2018 #2
    Hi girts,
    I'd say a definite no to that. Dark matter and dark energy are currently far more mysterious concepts than the EM field.
    To our current knowledge the EM field is one of the fundamental fields, that is, it is not made up of anything else.
    Not much that is certain. We think dark matter may exist, so we are looking for it.
    There is no fine line, "dark" is just a word.
    Physics is not about reasons. Physics is about models that can make predictions.
  4. Jun 11, 2018 #3


    Staff: Mentor

    No, that is only real photons. Virtual photons are not for that.

    Not even remotely fair. Our current understanding of EM is complete within the modern domain of experimental inquiry. There is no know EM phenomenon or observation that we cannot predict or explain quantitatively with our current models. Thus, we understand EM completely in this domain.
  5. Jun 11, 2018 #4


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    Staff: Mentor

    How could we "see" neutrons in a cloud chamber? They're not charged.

    In fact, photons are easier to "see" than many other particles whose reality you happily accept - photographic film records their impact quite nicely.
  6. Jun 11, 2018 #5
    Seeing photons do you mean high frequency ones like gamma radiation destroying a film like those in the early live recordings from the Chernobyl nuclear reactor explosion back in 1986?

    I do remember seeing those bright little flashes on the video which i assume are gamma impacts right?
  7. Jun 11, 2018 #6


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    Science Advisor
    Gold Member

    well that and I suspect @Nugatory was referring to normal photographic film that capture photons quite well
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