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How does an electromagnetic wave propagate in space?

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  1. Aug 11, 2013 #1
    I am a biochemist and so my physics knowledge is limited.
    But for a long time I have been wondering on how exactly the electromagnetic field associated with a single photon propagates in space.

    I understand (using a cartesian image of the electric and magnetic field change) the oscillating nature of the electric and magnetic fields associated with a single photon as it propagates in a given direction and how the frequency of the oscillation of the value of those fields are associated with (or determine) the energy of that photon.

    What I have trouble understanding, or visualizing is: what is (the substratum) that is changing as the electromagnetic disturbance propagates in space? Is it an underlying electromagnetic field that permeates the entire universe, and that is disturbed by the amount of energy associated with the moving electromagnetic wave?

    If not, then how does the disturbance (wave) propagate in space?
     
  2. jcsd
  3. Aug 11, 2013 #2

    SteamKing

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    EM waves are not disturbances in some medium, like water waves are. Michelson and Morley showed that light does not propagate through some hypothetical 'lumeniferous aether' back in 1887.

    The $64000 question in physics since Newton is what is the nature of light, and later on, this question was extended to EM waves as well. It is well-known that light sometimes exhibited characteristics of being composed of particles, while at other times it seemed to exhibit purely wave-like behavior.

    Quantum Mechanics provided a new basis for understanding why light exhibits its curious dual nature.
    For more details, see this article: http://en.wikipedia.org/wiki/Electromagnetic_radiation

    It is not a simple subject, and much work is still being done in this field.
     
  4. Aug 11, 2013 #3
    "EM waves are not disturbances in some medium, like water waves are. Michelson and Morley showed that light does not propagate through some hypothetical 'lumeniferous aether' back in 1887."

    The MM results are still being debated, and Einstein certainly talked of the Aether.
    <invalid reference>

    From what I have seen of the designs of many space based instruments such as Hubble, they are really wavefront sensors using the Shack-Hartmann science originally used for the star tracker cameras in the ICBMs. That information was classified for a long time, then became available to Goddard who developed it for the space based astronomy instruments. That technology was made available in 2011 to be licensed for commercial use, and we are now seeing that technology appearing in a number of areas, one of them being ARKYD
    http://www.kickstarter.com/projects/1458134548/arkyd-a-space-telescope-for-everyone-0
    and another, ILO-X.
    http://www.engadget.com/2013/05/28/iloa-details-its-ilo-x-lunar-telescope/
    Based on these developments I think we have to conclude that the vacuum needs to be considered a non-linear medium, and the transmission of 'light' through such a medium being by way of spatial solitons.
    Goddard: Can you see it now?
    http://techtransfer.gsfc.nasa.gov/wavefront/
     
    Last edited by a moderator: Aug 11, 2013
  5. Aug 11, 2013 #4
    Dear SteamKing,

    I do know of the conclusion from the Michaelson Morley experiment supporting the non existance of "aether" as it was being postulated.

    Similarly I understand the particle/wave duality. In my mind (wave/particle nature of photons) they are nothing but the manifestation in specific experimental settings of the same phenomenon, albeit characterisitics that were being interpreted as supporting a particle nature (photovoltaic effect) or wave (diffraction).

    Although not a physicist, and even less can I claim to fully getting the nuances of Quantum Mechanics, but even some of the "particle"-like interpretation appear in my mind possible to explain/interpret in light of wave theory, no? For example, wouldn't an explanation of the photovoltaic/photoelectric effect, be compatible with a concept of interaction of an electromagnetic wave of appropriate characterisitics with the wave function associated with electrons of an atom of an appropriate material, and by raising the energy levels of the former being able to increase the probability of one electron, or more, escaping the nuclear attraction and creating an electricity flow (or being ejected)?

    But I digress :smile:

    It still leaves me dissatisfied with my understanding (or ability to visualize) how energy of a single photon propagates in space/time.

    The concept of particle/wave may assist in my mind at describing mathematically what happens but does not appear to explain how it happens.

    What are current theories that attempt at explaining how does this take place?

    Cheers,
     
  6. Aug 11, 2013 #5

    Drakkith

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    No. The particle-like property of an EM wave is necessary to explain why they interact with matter in quanta. The classical behavior of a wave is NOT compatible with quantized energy transfer. In a classical wave, energy transfer is continuous, not quantized.

    Personally I don't look at it as single photons propagating out. I imagine a normal EM wave propagating outwards that has energy equal to a single photon.

    I don't see how you can come to that conclusion. The particle-wave duality perfectly fits within Quantum Mechanics and enables us to describe how nature works to unparalleled precision.
     
  7. Aug 11, 2013 #6

    SteamKing

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    Quotes by Solon:
    "EM waves are not disturbances in some medium, like water waves are. Michelson and Morley showed that light does not propagate through some hypothetical 'lumeniferous aether' back in 1887."

    "The MM results are still being debated, and Einstein certainly talked of the Aether."

    The M-M experiment and subsequent experiments throughout the TwenCen have all showed consistent results: there is no variation in the speed of light. M-M may still be debated by drunks in a bar, but the physics community seems settled that the 'aether' doesn't exist, and Special Relativity does not pre-suppose its existence. While Einstein may have talked about the 'Aether', his work certainly didn't rely on its existence. We may talk about Leprechauns and the Tooth Fairy, but that doesn't make them real.
     
    Last edited by a moderator: Aug 11, 2013
  8. Aug 11, 2013 #7

    Bobbywhy

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    Will you please help me locate at the above nasa website any mention of the

    1. "vacuum needs to be considered a non-linear medium" and
    2. "the transmission of 'light' through such a medium being by way of spatial solitons."

    I was unable to find either one. Thank you.
     
  9. Aug 11, 2013 #8
    "Will you please help me locate at the above nasa website any mention of the

    1. "vacuum needs to be considered a non-linear medium" and
    2. "the transmission of 'light' through such a medium being by way of spatial solitons."

    I was unable to find either one. Thank you."

    Hi Bobbywhy,
    NASA did not say those things, I did.
     
  10. Aug 11, 2013 #9

    phinds

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    Hell of trick, old Goddard designing space-based astronomy instruments, what with him having died in 1945 and all.

    The rest of your post seems to exhibit about the same degree of knowledge of physics.
     
  11. Aug 11, 2013 #10

    Bobbywhy

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    Since you’ve said that “the vacuum needs to be considered a non-linear medium” and "the transmission of 'light' through such a medium being by way of spatial solitons” are your own ideas, I ask you for the reference textbook or peer-reviewed scientific literature that contain these conjectures. Thank you.

    By clicking on the tab marked “Site Info” you will find the page called
    “Physics Forums Global Guidelines”. There please find these two guidelines:

    A. Discussion Guidelines prohibit “Personal theories or speculations that go beyond or counter to generally-accepted science”.

    B. “Generally, discussion topics should be traceable to standard textbooks or to peer-reviewed scientific literature.”
     
  12. Aug 12, 2013 #11
    The idea of a self-induced soliton wave-guide is not mine, there is lots of information on the subject available. For it to happen in space, then the vaccuum would need to be a non-linear medium. From what I understand of the space based instruments, the way they work is by detecting the wavefronts of these soliton 'beams'. The vacuum as a non-linear medium has been proposed, but the theory is somewhat complex, and perhaps could be shot down by a PF-er?
    "Spin space: the vacuum as a nonlinear medium".
    http://www.researchgate.net/publication/45858933_Spin_Singularities_Clifford_Kaleidoscopes_and_Particle_Masses [Broken]
     
    Last edited by a moderator: May 6, 2017
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