Photon frequency loss over time?

  1. rcgldr

    rcgldr 7,577
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    I remember reading an article many years ago that there was a theory that part of the red-shift we observe from far away galaxy's could be do to a time (or distance) related reduction in frequency of light, in addition to the "doppler" effect. Has this theory ever re-surfaced again (it may have been 10 or more years ago that I read this article)?
     
  2. jcsd
  3. Chronos

    Chronos 10,136
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    Jeff, what do you imagine those photons give up their energy to? Eventually they must glow, don't you think?
     
  4. rcgldr

    rcgldr 7,577
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    Possibly, but I'm pretty sure that there was an inference that it was more than just space stretching or speed that contributed to red shift. Maybe it was related to dark matter or something similar between an observered galaxy and the earth.

    It wasn't clear, but I assume the strecthing of the space in universe is due to the decrease in graviational fields as objects move away from each other?
     
  5. Do you mean the tired light theory as first proposed by fritz Zwicky (1927?).
    Photons lose energy as they travel and since E = hf the frequency reduces and wavelength increasesd. They are redshifted.
    He put it down to gravitational effects.
     
  6. rcgldr

    rcgldr 7,577
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    That's probably what I read, athough I'm not quite old enough to have remembered it went first published. Has this theory been abandonded now?
     
  7. SpaceTiger

    SpaceTiger 2,977
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    Tired light theory hasn't been taken seriously by the mainstream for quite some time. It was a viable alternative for several decades after it was proposed (20s), but the CMB and other cosmological tests have since put it very firmly to sleep.
     
  8. Let me put this another way! Instead of just quoting ‘cosmological tests’ it would help if you stated what they are.
    As far as I know, we have the Tolman surface brightness test and supernovae time dilation. Any more?
    The Tolman surface brightness test was always 'iffy' as it relied on models on how galaxies aged. On nearby galaxies it showed that expanding models were probably nearer the truth than static models. But this was on nearby galaxies (three in the same cluster?)
    However the HUDF came along and now the tolman test comes out very firmly in favour of a static universe.
    That leaves us with ‘time dilation.’ Supernovae light curves’ are stretched which agrees with the expanding theory whilst quasar light curves are not stretched – which agrees with the static universe. Since this is the same phenomenon, until such time as anyone can come with a theory that unifies these effects then the jury must remain out.
    CMB? Didn’t you tell me that the axis of evil is still there on the latest data?
    If the clumps are aligned about our solar system and galactic plane then even that has a problem. Furthermore, the horizon problem in the CMB is only solved by inflation and that has no experimental verification whatsoever!
    So we can neglect cosmological tests and the CMB to rule out a static universe – unless you know of any other?
     
  9. SpaceTiger

    SpaceTiger 2,977
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    The abundances of light elements, the cosmic microwave background, the formation of large scale structure, star formation rate vs. redshift, the Soltan argument, evolution of morphology with redshift, supernova time dilation, GRB time dilation, and much more, I'm sure. The CMB, abundances, and large scale structure all constitute multiple tests of BB predictions.


    Eric Lerner is a well-known crank. Those results come about from one of the effects I mentioned above -- the evolution of star formation with redshift. High-z galaxies are nothing like low-z ones, so as you've suggested, the test is not very useful. It may have some value at low redshifts and where galaxies haven't evolved much, but it's still not a very strong test.


    The "axis of evil" is a sign of possible contamination in the data at low multipoles. The vast majority of the information in the CMB lies at high multipoles, where the standard model fits the data to very high precision. The CMB is a very dramatic test of mainstream theory -- it comes as no surprise to me that most of the laymen advocating steady state models don't understand the WMAP results.


    Wrong again. Inflation is actually doing quite well lately. The universe has continued to be consistent with flat, now to a precision of a few percent. Furthermore, the fluctuations in both the CMB and large scale structure (see the "genus" test) have been shown to be gaussian, another prediction of inflation. Finally, the WMAP measurements indicate a spectral slope just slightly deviant from unity, just as predicted by inflation.
     
  10. Nereid

    Nereid 4,014
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    I suspect this is not well known among PF readers; could anyone provide both a succinct summary of what it is? Also, when was it first published? And how widely has it been used (in cosmology)?
     
  11. it would be nice if an actual physicist or student would have metioned that the question is scientifically invalid- since photons have no tau- thus they can't do anything 'over time' to begin with-
     
  12. Garth

    Garth 3,513
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    A good point.

    Observed cosmological red shift is to do with the way the photon is being observed, compared with how it was emitted.

    A photon is emitted by one atom and absorbed by another much later in the universe's history. Cosmological curvature results in a time dilation between the two, but should not that time dilation affect the mass of the atom as well as the frequency of the photon? i.e. if there is a de Broglie frequency associated with the atom's rest mass.

    Just a thought.

    Garth
     
  13. SpaceTiger

    SpaceTiger 2,977
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    They can certainly change as a function of coordinate time, which is usually what people mean by "time" in cosmology.
     
  14. Eh Up!
    Space tiger tells us that
    Garth says
    A contradiction I fear!
    Which means that neither knows what they are talking about?
     
  15. Garth

    Garth 3,513
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    Not at all.

    Cosmological curvatue is space-time curvature, the present mainstream model is concordant with a spatially flat, or near flat universe.

    The isotropic and homogeneous space-like foliations appear to have a flat geometry even though they are embedded in a 4D space-time that has curvature.

    This curvature is represented by the scale function R(t) as well as the (space) curvature constant k.

    I hope this helps.

    You might well be right - "cosmologists are often in error but never in doubt"

    But I will let SpaceTiger speak for himself. :smile:

    Garth
     
    Last edited: Jun 2, 2006
  16. SpaceTiger

    SpaceTiger 2,977
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    The Soltan argument basically compares the present day mass density of black holes to the integrated luminosity density of quasars. The idea is that supermassive black holes are expected to grow by mass accretion -- a process that radiates energy that we see in the form of active galactic nuclei. If we add up the total radiated energy from AGN over the history of the universe, we can infer how much mass was accreted. If our ideas about AGNe and cosmology are correct, this inferred accreted mass density ought to be comparable to the mass density of black holes. In general, the luminosity and mass accretion rate are related by

    [tex]L=\epsilon \dot{M}c^2[/tex]

    The efficiency, [itex]\epsilon[/itex], is not known in general, but has characteristic values of order 0.1 in most black hole accretion theories. The Soltan argument can be used in several ways -- for example, to infer the efficiency of accretion. In the present context, it can be used to support the expansion paradigm. Using a reasonable value for the efficiency, the present-day mass density of black holes is comparable (to within an OOM) to the inferred accreted mass density:

    Observational Constraints on the Growth of Massive Black Holes
     
  17. SpaceTiger

    SpaceTiger 2,977
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    To the contrary, Garth knows quite a bit about GR. I won't insult you and suggest that you didn't know that the universe had been measured to be flat, but when two ideas seem to contradict one another, it's always wise to consider the possibility that you might yourself be misunderstanding something about them.
     
  18. So, is it flat or is it curved?
     
  19. Garth

    Garth 3,513
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    The consensus of opinion is the WMAP data is consistent with spatially flat universe. Such a spatially flat 3D hyper-surface would be embedded in a 4D curved space-time.

    The curvature of space-time is revealed by working out all the components of the Riemannian tensor with the Robertson-Walker metric in which k = 0, they are not all zero. It is this 4D space-time curvature that describes the gravitational field.

    The peculiar thing about the GR cosmological solution is when all the Riemannian components are zero, in the empty universe case, then the 3D space hyper-surface is not flat but hyperbolic and expanding linearly.

    My caveat on that consensus opinion is, as the WMAP data is angular in nature and conformal transformations preserve angles, it is also consistent with a spatially conformally flat universe.

    Garth
     
    Last edited: Jun 3, 2006
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