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Speed of Light Remains Constant

  1. Dec 18, 2003 #1
    Despite some recent studies that indicate the speed of light may have been slowing down, NASA has announced results of examination of light from two nearby galaxies showing that the speed of light is as special relativity describes it.
    Specifically, they looked at Mkn 421 and Mkn 501, both of which have massive black holes spewing gamma radiation. The gamma photons collide with infrared photons and annihilate each other. If the speed of light were not constant, the photons from the galaxies would not have enough energy to cancel out the infrared ones.

    There has been some investigation into whether or not the quantum foam would impeded the speed of light. It also brings into question some models of a theory of everything involving extra dimensions. The results indicate that the energy levels of these dimensions can't be as powerful as some of the models claim them to be.

    Speed of light not slowing, NASA study says

    and for additional information

    Hubble Pictures Too Crisp, Challenging Theories of Time and Space

    These observations are also interesting because they support the idea of continuous space-time as opposed to discrete, quantized space-time. The information is useful in combatting apologetics which claim traversal of an infinite set of temporal moments is impossible, i.e. therefore there must be a First Cause. Not that the contrary can't already be demonstrated using convergent series, but it helps to show that the continuum appears to exist in reality.
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  3. Dec 18, 2003 #2


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    Good post, I am going to move this to Relativity. There are several posting over there that need to see this.
  4. Dec 18, 2003 #3


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    Here's one of them:

    Contributions welcome!
  5. Dec 19, 2003 #4


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    so is this most profound observation going to change
    theorists minds about quantum gravity or the existence
    of planck units or strings and multiple dimentions?
    i doubt it, i expect many pages of endless calculations
    to show why light can escape any perturbance from
    the quantum effect, and the theories will remain
    afloat untill all the patches are exhausted.
    Last edited: Dec 19, 2003
  6. Dec 19, 2003 #5


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    If you google on Stecker and arXiv, you'll see that he's active in the field of high energy astronomy, particularly cosmic (gamma) rays.

    I've only skimmed a couple of the papers, but found this review to be quite interesting:

    It isn't immediately obvious which of the papers in arXiv is the one referred to in the space.com article that Jeebus has a link to, but it would be an interesting read too.
    IMHO, it's just another piece of good research which constrains some models a bit more; part of the on-going effort. A long way to go yet I expect before we're at even the stage we were with neutrinos two decades ago.
  7. Dec 19, 2003 #6


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    Found it!
    "Constraints on Lorentz Invariance Violating Quantum Gravity and Large Extra Dimensions Models using High Energy Gamma Ray Observations"

    Comments from people who read this paper are most welcome.
  8. Dec 19, 2003 #7


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    this seems like a good paper and Stecker seems very on top of it.
    Notice what he says on page 6:

    "In many of these models Lorentz invariance is predicted to be violated at high energy. This results in interesting modifications of particle physics that are accesible to observational tests using TeV gamma-ray telescopes and cosmic ray detectors.

    An example of such a model is a quantum gravity model with a
    preferred inertial frame given by the cosmological rest frame of the cosmic microwave background radiation (For an extensive discussion, see the review given in Ref. [23].)"

    I assume what he means by "violating Lorentz invariance"
    is having a preferred frame, and what he is constraining (if they have not already been completely eliminated!) are the models in which there is a preferred frame.

    To be sure about this, it might be helpful to consult the "review given in Ref. [23]" which Stecker offers as providing "an extensive discussion".
    Particularly pages 18 and 19 in that reference: section 4 "The near term experimental situation"

    Here is the Ref. [23] link. Any comments?
    Last edited: Dec 19, 2003
  9. Dec 19, 2003 #8
    Doesn’t this study just mean that the speed of light today is the same basic speed as it was half a billion years ago? I doesn’t mean that the relative speed of light never varies when it moves from one object to another. When passing near the sun, a beam of light slows down when viewed from the earth and measured by an atomic clock at the earth. This was explained in Einstein’s 1911 gravitational redshift theory.
  10. Dec 20, 2003 #9
    Re: Re: Speed of Light Remains Constant

    I dont know much about Einstein's 1911 Gravitational Redshift Theory, so that might account for the reason why I dont fully understand "a beam of light slows down when viewed from earth". I thought Special Relativity described how the speed of light remained constant regardless of your intertial frame (i.e. Its not possible to observe the speed of light "slowing down").

    Edit to add: Nevermind, I found the information you were referring to on another thread :)
    Last edited: Dec 20, 2003
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