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Cosmological redshift interpretation

  1. Apr 24, 2013 #1
    Can the cosmological redshift be interpreted as atomic frequencies increasing by the scale factor as the Universe expands?

    This explanation seems closer to the truth than the popular idea that a photon's wavelength somehow expands while it travels to us from a distant galaxy. Metric expansion only occurs with proper distances (between events at the same cosmological time).

    I think people take the standard derivation of the cosmological redshift to imply that the photon's oscillation period increases with the scale factor. But this again is equivalent to assuming its wavelength increases.
    Last edited: Apr 24, 2013
  2. jcsd
  3. Apr 24, 2013 #2


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    The wavelength of atoms is invariant relative to the size of everything solid, and the frequency is invariant relative to all other local timescales. You need quite a strange re-definition of length and time to get increasing frequencies for atoms here on earth.
  4. Apr 24, 2013 #3
    The atomic frequencies are based on the transition energies between atomic energy levels. You need to explain how these energy levels could be changing. It would probably involve variation in the fine structure constant over time.
  5. Apr 24, 2013 #4


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    If fundamental masses varied as in a mass field theory such as that of Fred Hoyle's attempt to explain the CMB in a Steady State Universe http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1975ApJ...196..661H&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf [Broken], then cosmological red shift would be interpreted not as a loss of energy of the photon but as an increase in the mass of the apparatus measuring it.

    In a conformal transformation one metric transforms into a physically equivalent alternative according to

    [itex]g_{μν} → \tilde{g}_{μν} =\Omega^2 g_{μν}[/itex]

    and mass is conformally transformed according to

    [itex]m(x^{μ}) = \Omega \tilde{m}_{0}[/itex]

    Just a thought....
    Last edited by a moderator: May 6, 2017
  6. Apr 24, 2013 #5


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    And yes, in a conformal transformation theory where fundamental masses vary, length and time are redefined.

    The radius of an atom (Bohr radius) is inversely proportional to its mass and the frequency of atomic transitions is determined by the Rydberg constant which is proportional to mass.

    Thus as mass increases steel rulers would shrink and atomic clocks would speed up.

    In such a conformal transformation an expanding universe with fixed masses and regular clocks could be reinterpreted by a static universe with shrinking rulers and clocks that 'speeded up'. CMB photons would be of fixed frequency and wavelength and the Big Bang would be projected back into the infinite past.

    Just a thought....
    Last edited: Apr 25, 2013
  7. Apr 24, 2013 #6
    The question posed by Johne has a simple answer - No, this is not what is going on at all!

    But I don't blame him for asking it. The notion of an expanding universe driven by 'dark energy' sticks in my throat and I am rather motivated to come up with an alternative theory. And sometimes the motivation bypasses rigor.

    I have recently come across an old article in the New Scientist (http://www.newscientist.com/article/dn7167-giant-spacetime-ripples-may-cause-cosmic-expansion.html). The title is self explanatory and I would not recomend the article particularly as I found it fanciful and also lacking in rigor.

    But it does touch on what I think is the right idea - that we see the universe as expanding because the spacetime we are in the trough of a (very large) gravitational wave.

    Spacetime contracts under gravity and so will expand if the gravitation is removed. I know that the accepted wisdom of the big bang theory is that space just expands (either by dark energy or just expands anyway) and that the big bang was not a black hole singularity that somehow exploded. But where is the proof? This surely is conjecture.

    Of course it would be conjecture to say that the big bang was an exploding singularity and indeed there are a great many problems with this theory which I shall not go into here. It would at least produce the right results though using known spacetime behaviour under gravity rather than the pure conjecture of dark energy. Those inside the light cone of an exploding singularity would be in a collapsing gravitational field (notwithstanding local variations) and would see recession increasing with distance.
  8. Apr 25, 2013 #7


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    This would be equivalent to the statement that atoms have been shrinking. And yes, you can re-interpret your definition of length to do this sort of thing. But then you end up with the global properties of the universe being important for understanding the local behavior of atoms.
  9. Apr 25, 2013 #8
    If by 'global properties' you mean phyiscal constants then of course these underly the behaviour of atoms. But if you were in contracted space you would be unaware of it. Your atoms would all appear the same size and all the physical constants would measure the same. The energy transitions would be the same also leading to the same spectural lines. Light coming to you from a less contracted source would look the same because at all points time dilation cancels out the length contraction. For something to seen as red or blue shifted it must be either moving relative to you or in a different gravitational potential or both.
  10. Apr 25, 2013 #9


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    Actually, I was more talking about the expansion history, and specifically how the global matter density impacts how atomic sizes change over time. A model which holds the average distance between galaxies constant but allows atoms to shrink is perfectly viable, but it has a weird connection between the expansion history and atomic sizes. This makes the model potentially-misleading, and also probably cumbersome to work with for anything dealing with atomic behavior.
  11. Apr 25, 2013 #10
    I am always disinclined to accept any notion of physical constants changing over time. It violates my sense that physical laws operate the same everywhere, always did and always will. Yes this is a point of faith but ultimately every theory rests on at least one point of faith. The application of rigor though, never goes amis. And it is always usefull to apply Occam's Razor. Why introduce an entity into an equation when it brings no benefit? I can't see any point to changing atomic sizes. There is no evidence to support this idea and although I can't think of any way to catagorically disprove it, it's introduction just kicks the can down the road and interpretation of the accelerating red shift remains equally perplexing if not more so!

    What I would say though is that you are not the only person who has forgotten to shave with Occam. I would strongly suggest all those out there looking for dark energy are making the same mistake.
  12. Apr 25, 2013 #11


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    Well, if it makes you feel any better, it's always possible to reformulate things into time-invariant laws.
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