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I New possible explanation for Hubble redshift

  1. Jul 3, 2017 #1

    hilbert2

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    I just saw this news article on the home page of the university I'm working in:

    http://www.aalto.fi/en/current/news/2017-06-30/

    It seems to be about a study that can potentially explain the redshift of distant stars with a mechanism that's related to the interaction of photons with the interstellar medium and doesn't require an expanding universe:

    How plausible does this seem to you people? Is there any evidence in addition to the redshift of stars for an expanding universe? Cosmic background radiation seems to be quoted as one. Of course, in GR a constant average density universe is unstable, so the only alternative would be that our universe is getting smaller (if we assume GR is correct), and these results are too preliminary to make any conclusions from.
     
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  3. Jul 3, 2017 #2
    I read something about large voids have a higher redshift. Would this be a contradiction?

    Does the interaction effect all wavelengths in the same way?
     
  4. Jul 3, 2017 #3

    PeterDonis

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    I don't see any link to an actual paper. That's always a red flag for me.

    As far as whether this could explain the observed redshifts of distant galaxies, it is basically a "tired light" hypothesis (light loses energy as it travels), which has already been ruled out by observation:

    http://www.astro.ucla.edu/~wright/tiredlit.htm
     
  5. Jul 3, 2017 #4
  6. Jul 3, 2017 #5

    PeterDonis

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    Ah, I missed that. This paper does not appear to discuss the claimed application to cosmology, though.
     
  7. Jul 3, 2017 #6

    hilbert2

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  8. Jul 3, 2017 #7
    Scroll down. There are more paragraphs below the image. A section titled "Potential interstellar applications of the discovery".

    Does the new paper challenge the first of the "three problems" listed in your link? And a corollary could the redshift measurement have slight errors caused by interaction with inter galactic gas?
     
  9. Jul 3, 2017 #8

    hilbert2

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    He probably meant the actual peer reviewed paper, not the news article.
     
  10. Jul 4, 2017 #9
    It seems like a tiring light hypothesis to me.
    Like earlier such proposals though, no explanation is offered for what might be tiring light.
    Photons just wear out doesn't make sense {to me}
     
  11. Jul 4, 2017 #10

    PeterDonis

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    Yes. The peer-reviewed paper is the acceptable source as far as PF discussion is concerned. The news article is not.
     
  12. Jul 5, 2017 #11

    kimbyd

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    Utterly implausible.

    This is a theoretical paper that doesn't seem to do any detailed analysis of how their scenario matches with observation. My bet is that we'll get a couple of response papers within a few weeks which demonstrate that current cosmological evidence completely rules out this scenario.

    That's assuming the broader cosmology community picks it up at all. Since it was actually published in a mainline journal, my bet is that at least a couple of teams will feel the need to respond. But we'll see. There is a chance it will just be ignored because it's so far out there.
     
  13. Jul 5, 2017 #12

    kimbyd

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    To expand upon this a little bit, here are some potential avenues for further investigation:
    1. Without looking at the paper in-depth, it likely provides a distance/redshift equation. It is very likely that current estimates of distance vs. redshift already rule out this paper, especially if data over a large range of redshifts are examined. This would be relatively easy to do, and could be done quickly by people familiar with this kind of data analysis. My bet is that the furthest supernovae would not fit whatever relation they could come up with.
    2. How would the CMB be explained with this model? How would it be emitted in the first place? Why would it take on its current temperature? How would the pattern of anisotropies on the CMB be explained? The currently-accepted answers to all of these questions are intimately tied to the expansion of the universe being real. If the expansion were a fiction, then alternative explanations would have to be devised, which wouldn't remotely be easy. I wouldn't give the model even the slightest consideration unless the authors produced a convincing explanation for how the CMB could be produced, and that it was able to fit the CMB data in detail, not just with back-of-the-envelope calculations. This would be a very challenging task, but one that the proponents of the model would need to clear in order to be taken seriously.
     
  14. Jul 5, 2017 #13
    As has been pointed out in the previous few comments, the paper itself doesn't mention redshift. It comes up only as a tease toward the end of the university "article" (really a press release) linked to by the OP.
     
    Last edited: Jul 6, 2017
  15. Jul 6, 2017 #14

    hilbert2

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    I'm not sure why they decided in the press release to make a comment about something that's so far from their own field of study, and what kind of non-public discussion there has been with actual cosmologists. Doesn't the explanation of the observed expansion rate of the universe require assumptions about dark energy and matter densities that can't be observed by any independent means? If that's so, then I think there must be some room for alternative theories.

    There seem to have been some simulations that have used cosmological models to predict the anisotropy patterns of CMB. If the universe were to already be in a contraction phase after expanding for trillions of years or so, I guess it would already be close enough to "heat death" to not have any interesting chemical reactions, necessary for life, going on. Do you people think that the CMB anisotropy pattern would still be present in that situation?
     
  16. Jul 6, 2017 #15

    kimbyd

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    Not strictly, no. The nearby distance/redshift relationship points towards expansion without any need to reference dark matter or dark energy. With regard to the CMB, the fact that the CMB exists at all is intimately tied to the existence of expansion.

    Once you look at the detailed evidence, it becomes clear that we need dark matter and dark energy to fit the available data.

    This isn't a valid way of looking at the problem.

    The fact of the matter is that there is a wide variety of diverse observational evidence in favor of the current standard model of cosmology. Anything new that is proposed must, if it is to be taken seriously, also match all of that diverse observational evidence. That's not easy to do. Most theorists do this by taking the standard model, and only tweaking it slightly so that most observations are unaffected. This model is different: it's a complete overhaul. Such a complete overhaul, by its very nature, requires tremendous amounts of work to show that it fits all of the available evidence.

    I don't understand what you're trying to ask here, or what it has to do with this topic.
     
  17. Jul 6, 2017 #16

    PeterDonis

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    Not ones that have already been ruled out by observation. As I pointed out in post #3, the hypothesis in the paper is basically "tired light", and we already know models of this type do not match observations.
     
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