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Red shift of light

  1. May 21, 2013 #1
    I have long been curious as to the Big Bang. Our cosmology is based on Hubble's observation of the red-shift and its interpretation, and our observations are made to fit the interpretation of an expanding universe. What if simply the frequency of electromagnetic radiation decays (lengthens) with age? Has anyone, ever, considered this possibility and modelled how it would affect our interpretations of our universe?
    Last edited: May 21, 2013
  2. jcsd
  3. May 21, 2013 #2


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  4. May 21, 2013 #3
    No; one would use the argument that anything blue-shifted was approaching us at a rate exceeding that of the "ageing" of light. The two interpretations are not mutally exclusive.

    My main interest is to find out if anyone has argued along the lines I have suggested.

    Thanks for your reply
  5. May 21, 2013 #4


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    By the way, I think this is a quite strange way to put it. Our observations supports (are consistent with) an expanding Universe. They're not made to fit it.
  6. May 21, 2013 #5


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    Welcome to PF!
    Redshift is observed in other contexts so there are mathematical relations already established between speed and redshift. If there is a completely different mechanism that causes it and no way to independently verify it, how could we possibly know how such a model would look?

    I can put a finer point on it though: Redshift=speed is measured in other contexts, redshift=distance isn't, but we have other ways of measuring distance than redshift, so the correlation between the two is not just guesswork.
  7. May 21, 2013 #6


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    Ok. I can't come to think of anyone at the moment.
  8. May 21, 2013 #7
    Thanks for your reply. My consideration was red-shift=age, as it were, which boils down also to distance, and given the supposed age of the universe would be extremely difficult to measure and particularly so as it does not seem to have been considered as a possibilty.

    No doubt we can measure distance by means other than red-shift, but in doing so we are also measuring age. But how do we measure rate of separation, which is what expansion of the universe is all about, if we don't use red-shift?
  9. May 22, 2013 #8
    This article will help.

    Also my signature has several links to related material. The cosmology101 link will take you to a site I'm developing. There are two articles there. Lineweaver and Davies.
    Also the cosmos/lightcone links will link you to a lightcone calculator its handy to see the expansion history of the universe.
    Anyways here is the article I mentioned.

  10. May 22, 2013 #9


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    What you are describing, "radiation decays (lengthens) with age" was proposed by others a long time ago. It's called the "Tired Light" hypothesis. It has been shown to be mistaken.

    "Tired light models invoke a gradual energy loss by photons as they travel through the cosmos to produce the redshift-distance law."

  11. May 22, 2013 #10
    "Originally proposed early in the development of general relativity in order to allow a static universe solution it was subsequently abandoned when the universe was found to be expanding" (re cosmological constant).

    This phrase needs correction. Hubble observed red-hift proportional to distance. Assumption;yhe frequency of light does not change with age. Interpretation; therefore the more the red-shifted an object, the greater its rate of separation from Hubble.Thus the universe was interpreted to be expanding and the interpretation became the paradigm. Thereofore later observations become interpreted according to the paradigm, as commonly has happened throughout history.

    I am addressing the assumption that the frequency of light does not change with age. 1) How do we prove this, one way or the other? 2) Has anyone tried modelling a universe in which the frequency of light does change with age?
  12. May 22, 2013 #11
    Just picked up Bobbywhy's reply. Thank you. I will follow this link; I was unaware of this "tired light" model.
  13. May 22, 2013 #12


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