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Can alternate radiation model explain redshift?

  1. May 31, 2012 #1
    What radiation model is used for understanding the cosmological redgarbage? It seems that neither a planar wave nor a point source would represent what we think we are really observing when looking at distant galaxies or exploding stars. Could the observed redshift be a property of the radiation field itself?
  2. jcsd
  3. May 31, 2012 #2
    I'm assuming the question you're asking is if the red-shift increase as distance from Earth increases can be explained via a theory other than expansion.

    There have been multiple attempts at these theories (I've often heard them called 'tired light' theories, a.k.a. the light gets tired from going a long distance and the wavelength increases), but none have been successful at explaining and predicting phenomena, and the expanding universe model is widely successful and supported, so is the common view.
  4. May 31, 2012 #3
    That didn't really answer my question but thanks anyway
  5. May 31, 2012 #4
    No, it could not. We know the redshift must be due to expansion because of the observed lengthening of the duration of supernovae. If some alternate, non-expansionary hypothesis were true, we would expect to see only redshifted light from these supernovae. However, because the universe is expanding, the farther away a particular supernova, the longer it's duration, as the train of photons is 'stretched' so that they span a larger distance, and so we see the supernova occurring over a longer duration.
    Last edited: May 31, 2012
  6. May 31, 2012 #5

    George Jones

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    The same effect that Mark M noted causes a decrease in the rate at which we see photons leave an object, so there is a dimming effect (beyond that associated with distance alone) that goes hand-in-hand with a cosmological redshift caused by expansion, and we actually observe this dimming-redshift correspondence. Any alternative explanation for redshift has to account for this precise redshift-dimming correspondence.
    Last edited: May 31, 2012
  7. May 31, 2012 #6
    I,m not sure what exactly we are referring to here.
    A well known dimming effect relating to the expanding universe(the Tolman effect) deals with the reduction in photon flux received in a larger universe(here and now) from a universe that was smaller at an earlier proper time relative to here and now.
    This dimming is very substantial.We are more in the range of a fourth power inverse law than the square law casual inspection of a static universe would anticipate.
    Thusly a type 1a supernova classed as a "standard candle" is not a standard candle at all,it is a modified adjustment dealing with an expected photon flux that critically depends on the expansion model chosen.
    For mid range red shift the deviation of flux from inverse sqare can be an order of magnitude,for high red shift objects,many orders of magnitude.
    My understanding leaves me unable to relate the stretching of photons to this aspect of calculating luminosity which from this perspective merely deals with the number of photons.
    By the way, De Sitter Space modifications to Einstein's version of General Relativity were(as I recall)conjointly worked on by Einstein and De Sitter as hybrid options.
    Whether or not De Sitter modified universe fills the bill,it certainly offers alternative red shift ideas.
  8. May 31, 2012 #7
    I suppose the stretching and dimming could be an inherent property of the redshift phenomena, regardless of root cause, but a successful theory would have to show that as you said.
  9. May 31, 2012 #8
    After about fifty years of arguing, then answer is


    See the wikipedia pages on "tired light".
  10. Jun 1, 2012 #9
    It's not clear what you are asking since people have discussed the standard explanation for redshift and the evidence that rules out Tired Light but you said:
    The simple answer to your question is that the model of the light we see is mostly thermal emission, like that from the surface of the Sun, which is close to black body for individual stars but integrated over whole galaxies. Of course there are also spectral lines, both emission and absorbtion mixed in which are the best way to measure redshift.

    If neither the previous answers nor mine address your question, can you make it any clearer?
  11. Jun 1, 2012 #10
    It seems unlikely to me that light could arrive, after billions of years, with all of its directional information intact. By design, the telescopes are filtering out all but the direction-specific wavelengths. Has anyone discussed that on top of inverse square loss there could be another loss affecting our ability to know which direction the light is coming from?
  12. Jun 1, 2012 #11
    If the direction changed, distant point sources would be spread or blurred, People have looked for that but it is not seen, we observe points sources. Note this is one of the arguments against Tired Light because Compton Scattering which is occassionally suggested as a mechanism by cranks alters both the energy and momentum of a photon. If that mechanism caused redshift, it would also spread distant sources. As has been said before though, there are several other observations that rule out Tired Light and indeed even Zwicky who first raised the possibility noted in the same paper that Compton Scattering could not work.
  13. Jun 1, 2012 #12
    We can forget Compton scattering for the time being - fine with me. But distant sources are in fact spread out, as evidenced by the Tolman surface brightness test.
  14. Jun 1, 2012 #13


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    Perhaps if you explain your understanding of the Tolman surface brightness test, we may be able to explain why you have mistaken it as relevant to this discussion.
  15. Jun 1, 2012 #14
    Supposedly in a static universe the appearant area of a distant object and the radiation intensity will both decrease with the square of the distance, yielding a surface brightness that should be independent of distance. Consequently, the fact that the surface brightness is a function of redshift has been used against the tired light theory.
    It is not clear to me why that is a valid argument against an alternative to expansion.
  16. Jun 1, 2012 #15
    What you said means an object will appear half as bright from twice as far away, the effects don't cancel out like you said.
  17. Jun 1, 2012 #16
    No I didn't say that. Perhaps someone else can explain why the Tolman surface brightness test results have been shown to support expansion.
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