Does light always travel at lightspeed?

Discussion in 'Physics & Math' started by proycon, Apr 8, 2002.

  1. AlexG Like nailing Jello to a tree Valued Senior Member

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    This is totally ridiculous. Photons have no magnetic field, and have no electric current.

    Stick to UFOs. You can make up any bullshit there.
     
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  3. max7331 Registered Member

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    Why? Well I suppose my intention was to be humble to the awesomeness of Physics and the fact I have never studied the subject in school. I was also considering the fact that I could have been missing something both important and simple, and I was trying to avoid the atypical condescending remarks people feel they need to add in order to feel superior. Even though my initial question was literally my first post on sciforums I have spent a considerable amount of time reading on them.
     
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  5. max7331 Registered Member

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    also I did not say I know nothing about physics, I believe I said little.
     
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  7. max7331 Registered Member

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    I completely understand.... I don't know what else to say, so thank you.
     
  8. origin Heading towards oblivion Valued Senior Member

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    Your question was completely legitimate. The overwhelming majority of the people on this site appreciate questions and an interest in learning science. Prof.layman is what we call a crank. He, like you, has not studied physics. Unlike you, he is delusional and believes that inspite of not having studied any physics that he somehow knows more physics than college professors and scientists. You can completely ignore his posts. More than likely he will eventually be asked to stop posting in the real science sections anyway.

    Keep asking questions and keep learning.

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  9. KilljoyKlown Whatever Valued Senior Member

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    Let me qualify your statements a bit. A photon always travels at the speed of light from the instant it is emitted from point A until it's absorbed at point B. When photons travel through a transparent substance such as glass it only appears to slow down, because each time it gets absorbed by the electron shell of an atom and then re-admitted takes time. The number of times that photon will inter act with the atoms of any transparent substance will be constant. Therefore a particular type of glass will always have the same refractive index and we will always be able to time how long it will take light to travel through a given thickness of it. But the actual photons themselves will always travel at light speed.
     
  10. Prof.Layman totally internally reflected Registered Senior Member

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    I think that sounds like a really good explaination of it. But, IDK if you could say the same about any transparent substance. Some could be more dull on the surface than others, or have a better crystalline structure. In other words, any transparent substance wouldn't be perfectly clear. Some transparent substances clearly wouldn't have light come out as the same color as that went in it, it could have a color tint for instance, like a ruby.
     
  11. KilljoyKlown Whatever Valued Senior Member

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    Yes, but I fail to see the point you are trying to make. Each transparent substance will have it's own characteristics and even the clearest substance will completely absorb some of the photons without re-admitting them. After all the deeper you go in the ocean the darker it gets and many transparent substances absorb some frequencies of light while letting others pass through, hence the various colors you mentioned. None of that will change the fact that each photon always travels at the speed of light from point A to point B however long or short those distances may be.
     
  12. Prof.Layman totally internally reflected Registered Senior Member

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    The point is that even though a substance is transparent that the frequency can be changed by the valance electrons of other atoms. Say if you conducted an experiment, it may take longer for light to travel through a ruby than a diamond. You couldn't use one standered that described every transparent substance. IDK if it actually takes light longer to travel through a ruby than a diamond, but it could prove to be an interesting experiment.

    It could answer the question, does the photon actually get absorbed and re-admitted, or is it just a result of it being created by vibrations in the electromagnetic field itself? A ruby, makes red light that is at a longer wavelength, it would then travel inside of a larger valence shell. A diamond, for some reason doesn't affect the properties of light because of its valence shells. It could be absorbed and then re-admitted at the same wavelength. So maybe it would be better to use some other precious gem that is not a diamond. They frequency of the electrons in the valence shells are not having an effect on the light going through the material. But you would think that if they had the same exact internal structure but then changed light to two different wavelengths, then a relation could be found there.

    Is the difference of time traveling through a medium caused by a change in the frequency, or a change in the wavelength? Or does it even really matter? IDK the only reason I bring it up is because I have read that they are vibrations in the electromagnetic field, but then two photons can be created from the Higgs Boson, that is a vibration in the Higgs Field.

    The Higgs Field is what gives particles mass, and it is not said to be caused by the electromagnetic field or connected with it in any way.
     
  13. origin Heading towards oblivion Valued Senior Member

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    More of your ramblings and confusion. You can use one standard to describe a transparent substance - it is called refractive index. The refractive index is defined as RI = c/v, where v is the velocity of light through the substance. There is no need to do an experiment (do you really think you are the first one to think of this) light travels slower through diamond than a ruby.

    Good god, do at least a few minutes of research, maybe it would stop you from posting this nonsense.
     
  14. KilljoyKlown Whatever Valued Senior Member

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    The transparent medium does not change the frequency of any photons. The photons are absorbed but in the case of a ruby only the red frequencies are re-admitted. Again the speed a photon takes to travel through any substance is determined by how many interactions the photon has during a given distance through the transparent medium. The more stops it makes the longer it will take to travel through that medium. When an electron absorbs a photon and then re-admits it, it's almost instantaneous, however it is slower than no interaction at all.
     
  15. Prof.Layman totally internally reflected Registered Senior Member

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    I was thinking more along the lines of the Yang-Mills model of quantum field theory, I tend to take the position of Wolfgang Pauli. The quantum field theory of Yang-Mills assumes that the photon is massless. But, say for instance there there is no unknown particle being generated by the Higgs-like boson, that then creates two photons, then the photon could have a very small mass, a small interaction with the Higgs Field. It could then mean that photons are actually created by the Higgs Field and not the electromagnetic field alone. This intermediate particle not actually existing could make every crank theorist dreams come true, so to speak. So then I wonder if the interactions here like you say are not instantaneous, but are actually determined by the virtual particles involved in the interaction. That maybe it is Higg-like because it doesn't fit with quantum field theory, or more exactly Yang-Mills theory. These virtual particles may just be interacting differently with the Higgs Fields. So then they would take different amounts of times to be absorbed and like you say re-admitted. Maybe these virtual particles are real, and the Higgs Boson is trying to tell us that.
     
  16. Pete It's not rocket surgery Registered Senior Member

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    I don't think this tells the full story. You seem to be treating photons as purely particle-like.
     
  17. Prof.Layman totally internally reflected Registered Senior Member

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    I have been trying to treat them as a vibration of the electromagnetic field. The Higgs boson is a vibration of the Higgs Field, I don't see how a disruption in the Higgs Field could then act like a vibration of the electromganetic field. So then if you say that the Higgs Boson is not a disruption in the electromagnetic field, then how could you say that photons are only created by a disrutption in the electromagnetic field?

    They had to introduce an unknown particle that comes from the Higgs Boson that could then decay into two photons. They don't know what this particle is, and it is only said to be there because Feynman Diagrams would not allow them to come from something that isn't a part of the electromagnetic field. It is said to be there because of conservation of decay of particles. If this particle didn't actually exist, then two photons could come from a disruption of the Higgs Field and not the electromagnetic field.
     
  18. KilljoyKlown Whatever Valued Senior Member

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    I agree with you but the example I used does provide some easy concepts to understand. Many of the people that browse this forum don't have a strong math or physics background and I always aim to satisfy their curiosity in a way I find easy to understand. Hopefully I'm doing okay in that department.

    Prof.Layman

    When you try to tie Higgs Boson to photons, can you please cite or post some links that support your comments. When it comes to the Higgs I need more education before I can take a position on what you said. The Yang-Mills link you posted was almost all math that was over my head, so if you post links about Higgs theories, could you find more text as opposed to pages of complex math?

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  19. brucep Valued Senior Member

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    It is a good non mathematical quantum explanation for the photons path through a medium. The absorption of the photon is modeled as a localized point particle.
     
  20. Prof.Layman totally internally reflected Registered Senior Member

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    I was reading, "The Paticle at the End of the Universe : How the hunt for the Higgs Boson leads us to the edge of a new world" By Sean Carroll, Ph.D. The title is kind of misleading, but I think it tries to answer a lot of good questions that I have had trouble understanding in the past. There are other particles it can decay into, the two photons is just one of those things. It doesn't happen a lot but it says that it is most reliable product of the Higgs Boson, or something to that extent.
     
  21. Prof.Layman totally internally reflected Registered Senior Member

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    In the book, it says that a photon is actually created by vibrations in the electromagnetic field, but then it goes on to say that photons are created from the Higgs-like boson and the Higgs-like boson is a vibration in the Higgs Field. So then I fell from grace and went back to crank land once again. I don't understand how this interpretation could be applied to the Higgs-like Boson that was found. It has kind of lead me to think that if this new particle does exist, that it could be key to the unification of the other three forces and gravity. That is the only way I can think that a vibration in the Higgs Field could then cause a vibration in the electromagnetic field.
     
  22. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    I will go out on a limb and say that light can display either duality state at any time, based on the event being observed; both states always being potentially available.

    Logically, as it is traversing space, it seems light must display its wave-like state. I say that on the basis of how it is said to propagate with transverse electric and magnetic fields advancing along as a transverse wave. If I am right by saying that, and I can stand to be corrected, then it is the wavelength of the light that determines if it will be absorbed or not.

    Once the wavelength is acceptable, the absorption initiates the incorporation of the light energy in quanta to the absorbing electron, and is available for readmission because the absorption has elevated the level of excitement of an electron. The readmission occurs when that electron drops back to the pre-excited state. This phase of the progress of the light through the medium displays the particle nature of light by adding a precise amount of energy to the electron during the period between absorption and emission; it is no longer light as such, but is energy quanta added to the energy of the electron, or is that an over simplification?

    If the light is incoherent, consisting of many wavelengths, then I think the explanation of how it travels through a medium like glass would depend on the wavelength, so I interpret Killjoy's explanation to be about a specific wavelength or set of wavelengths that can be absorbed. The light that is not of the proper wave length to be absorbed is what my question concerns. Does that unabsorbed light traverse the medium without interruption and therefore pass through faster than the light that is absorbed and re-emitted?
     
  23. Prof.Layman totally internally reflected Registered Senior Member

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    Like orgin pointed out to me earlier, light takes longer to travel through a diamond than a ruby. If he is right, then the answer would be no. But I don't think it is so much an issue with it being absorbed or not, I think the valence shells just are not as picky about what wavelengths of light they will or will not accept. There is just more valence shells to choose from so to speak, or they are not confined to only absorb and emmit only one single wavelength. But, I am not too sure about this area of it really. I don't think diamonds just let the wavelengths of light off the hook so they are not involved in this process. Only some substances are more picky about what wavelengths they let through.

    Maybe it is that white light is a combination of all wavelengths, so then the virtual particles in the electrons have to travel slower by reacting more with the Higgs Field, but who knows really, it seems like it could be anybodies guess.
     

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