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A Moving Photon Source

  1. Feb 26, 2013 #1
    I have an idea for an experiment to see how the distribution of photons changes when they are emitted from a moving photon source.

    This is a continuation of an earlier discussion here with added information and more questions.

    "What happens to a photon wave packet when half out of a moving device?”
    https://www.physicsforums.com/showthread.php?p=4095957#post4095957

    For a stationary source the distribution pattern of photons might be something like a bell curve. For a source in motion, normalize the location of the photons to the direction of the source, adjusting for the speed of light. Will the bell curve get wider due only to experimental error? Or will the source motion have a widening effect on the distribution of photons?

    The experiment could be done by spinning a fluorescent molecule with lasers.

    Motion in the direction of the photon travel would be expected to cause red shift or blue shift, but that's not what I’m interested in since that is well known. The direction of motion I’m interested in is other than that, a "sideways" or perhaps "radial" motion.

    I am particularly interested in how quantum uncertainties affect the direction of photons relative to the source as the source moves, so the photon pattern is not as easy to predict as if the source was stationary.

    How might theoretical gaps between relativity and quantum mechanics affect the outcome of this experiment, if at all.

    I am not a trained physicist and am asking for people to help with this if interested. I would like to get an experiment like this done and would welcome any ideas on how I can make this happen.
     
    Last edited: Feb 26, 2013
  2. jcsd
  3. Feb 26, 2013 #2
    Interesting, not sure if you will get important results but it would be a great learning experience. I suggest reading up on quantum dots as photon emitters, you can couple phonon modes in the crystal to the dot to cause excitations and emission. It seems complicated and wordy but I think quantum dots would be a relatively simple system to analyse as long as you have a knowledge of wave mechanics. You will also need some kind of imager to detect photons, ccds come to mind.
     
  4. Feb 26, 2013 #3

    ZapperZ

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    There is nothing unknown here.

    In synchrotron light sources, one often use a series of undulators or wigglers to cause relativistic bunches of electrons to wiggle and thus, generate light. This is identical to having a light source moving relativistically. The physics of this is extremely well-known, including the radiation pattern emitted both longitudinally and transversely. In fact, the same principle is at work in free-electron lasers.

    Zz.
     
  5. Feb 27, 2013 #4
    I don’t think it’s the same. A wiggler emits light at a point of a magnetic deflection, not a very fast moving position as I would like to investigate. The electrons that produce the light are EM and not molecular. Do you measure velocity and angular position of an electron moving at relativistic speeds in relation to same of its emission of a single photon wave packet in a synchrotron or is the light measured as coming from the area of deflection?
     
    Last edited: Feb 27, 2013
  6. Feb 27, 2013 #5

    ZapperZ

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    Say what?

    What you are describing is the deflecting magnet that causes the electron beam path to bend! This is NOT what I have described and this is not what the wiggler/undulator does!

    If I'm in the frame of reference of the electron (and this is often done when solving the dynamics of this problem), all I see is bunches of electrons oscillating up and down and up and down, as if it is at the end of a mass-spring system. Period! (no pun intended) This is NOT the synchrotron radiation.

    More importantly, you never addressed the fact that this type of a description is contained in classical E&M.

    Zz.
     
  7. Feb 27, 2013 #6
    It has already been a great learning experience and informative replies like yours encourage me to do more, thanks.
     
  8. Feb 27, 2013 #7
    Sorry to have to quote wiki but a wiggler and deflecting magnet work in the same way and as I described.
    http://en.wikipedia.org/wiki/Wiggler_(synchrotron)

    http://www.synchrotron.org.au/index.php/synchrotron-science/how-is-synchrotron-light-created

    And I said the same.
    I want to measure the velocity, position in space and angle of the device that emits the photon wave packet, while it moves. Can you do that with an electron? Doesn't that break the uncertainty principle?
     
    Last edited: Feb 27, 2013
  9. Feb 27, 2013 #8

    ZapperZ

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    I'm sorry, but I really don't have time to deal with what you read on Wikipedia, especially when you don't really understand what you read.

    My issue with this is with your original post:

    The problem here is that you refuse to learn about classical E&M. Instead, you already jumped ahead, without knowing the physics involved, about "theoretical gaps between relativity and quantum mechanics".

    Please note that we welcome people who wish to learn physics. However, our PF Rules are very clear about speculative posts. When you do not understand the basic physics, but continue to build upon that shaky knowledge something else, that is considered to be speculation.

    Zz.
     
  10. Feb 27, 2013 #9

    Dale

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    Photons emitted from moving sources are well studied. See http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html , especially section 3.3

    This is called "transverse Doppler". See section 4.

    They wouldn't. The "theoretical gaps" are between GR and QM. What you have described involves only electromagnetism where there is no gap, not gravity.
     
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