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The trobule with Arp

  1. Nov 7, 2007 #1


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    The topic of Arp's cosmology came up in another thread, which died aborning due to it not meeting PF guidelines. I would like to remedy that by introducing a more serious thread which will avoid the guideline issues.

    My information about Arp comes from the peer reviewed paper


    This states in part:

    So I would make the following observations, based on this paper - but since I'm not intimately familiar with Arp's cosmology, I would appreciate input if I'm missing or misrepresenting anything as far as the "mainstream" position goes.

    1) Arp's evidence could best be characterized as suggestive, as opposed to "conclusive". Other scientists have looked seriously at his idea that the red-shift of quasars could be due to high peculiar velocities (i.e. velocity relative to the CMB frame), but this idea hasn't panned out due to a lack of corroborating evidence. The current theory (AFAIK) is that quasars are black holes at the center of galaxies. (I'd post references for this if I had them to hand to hand, but I don't.)

    2) Arp himself doesn't (AFAIK) have any quarrel with the big bang theory, and is not proposing any sort of "tired light" theory. The red shift just cannot be explained by tired light (see for instance Ned Wright's page on tired light which quotes the appropriate references). It has to be explained by velocity in order for high-redshift supernovae explosions to occur in "slow motion" (over longer times) than low-redshift supernovae explosions.
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  3. Nov 7, 2007 #2


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    Arp does not believe that quasar redshifts arise from peculiar motions. If that were true, either we should see 50:50 redshifted:blueshifted quasars (which we don't) or the Earth would have to reside in the most privileged place in the universe to see all quasars rushing away from us (which we should reject out-of hand).

    Arp et al believe that quasars are ejected from galactic cores and that they undergo evolution in some quality that causes redshifting. The redshift evolves from high to low as the quasar evolves into a galaxy. In other words (in his view) the redshift of cosmological bodies (including AGN and galaxies) results from a combination of the Hubble flow (standard redshift/distance relationship), peculiar motions, and some intrinsic redshift (mechanism as yet unknown). I hope I have stated his position as fairly as possible - he is a very nice person and I would not want to misrepresent his views.
  4. Nov 7, 2007 #3


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    OK, that's funkier than I thought. If the red shift is not due to doppler shift, does Arp have a paper that describes the origin of the red shift, and is it peer-reviewed?
    Last edited: Nov 7, 2007
  5. Nov 7, 2007 #4


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    Yes, it is funkier. If Arp et al are correct, there are unmodeled contributions to redshift that cause us to find apparently-interacting astronomical bodies (galaxies, quasars, HII regions, etc) that are at different redshifts. Such an unmodeled source of intrinsic redshift could make standard cosmology very difficult, since distances could not be estimated cleanly with the Hubble relationship and a rule-of-thumb span of expected peculiar velocities. Note: The paper you cited in the OP fundamentally misstates Arp's views on redshift, though this is not an uncommon event.

    Arp and Jayant Narlikar speculated that newly-ejected matter (quasar, for instance) evolves in redshift, and in a peer-reviewed paper they set forth a hypothesis of variable quasar mass in a flat cosmology. Their initial paper on this concept is here.


    I do not endorse this concept of variable mass - I'm just showing that Arp et al have made a stab at theoretical support for the concept of intrinsic redshift.
  6. Nov 8, 2007 #5
    Yes indeed.The red shift cannot be explained by "tired light", just as you mention here and for reasons that Ned Wright explains in some detail. I also hold no brief for Halton Arp's views, but I do have a niggle.

    Here it is. You are choosing the wrong words in saying that
    . Rindler (section 9.6 of his relativity text) points out that
    And I remember that Narlikar also emphasizes that red shift is not to confused with the classical Doppler effect -- i.e.with a classical velocity effect --- because it is pure GR.

    But Rindler was, I think, also wrong in referring to red shift as an "expansion" effect. It and slow-motion supernovae explosions both involve similarly ephemeral cosmological time intervals. They are GR phenomenona that are, like others, misleading (albeit convenient) to label with words that have familiar meanings. GR is not a mundane familiar description of nature that invites such labelling for its phenomena.

    These phenomena arise simply because the ratio of the coefficients of space and time differentials in the R-W metric varies with time. They do not tell us which, if either or both, of the coefficients so varies.

    Since the whole of modern cosmology involves settling on "expansion", I don't think this is a trivial niggle
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