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Is cosmology in constant trouble?

  1. Sep 13, 2004 #1

    Chronos

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    This should stir up some lively discussion.

    http://arxiv.org/abs/astro-ph/0405630

    CAUTION: Not suitable for audiences who habitually memorize all the tables in the back of the textbook.
     
  2. jcsd
  3. Sep 14, 2004 #2
    Interesting article! Perhaps cosmology is constantly changing? :)
     
  4. Sep 14, 2004 #3

    Garth

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    When we start varying fundamental constants we have to be very careful how we continue to define units of our measurement. We become like "Alice through the looking glass."
     
  5. Sep 14, 2004 #4

    turbo

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    An excellent overview of the state of cosmology! Great paper!

    Cosmology is always in trouble, but the trouble is not caused by the people searching for answers. It is caused by the people who cling to "consistent" models that are inaccurate. This is the real trouble. There is a really naive attitude (common to all bureaucracies, BTW) that our current model of the universe is essentially complete and accurate, and only needs a bit of tweaking here and there. (inflation, dark energy, dark matter...more to come as future observations diverge w/ theory...). Newton, Kepler, and Copernicus all improved on the work of others, as did Einstein. If Kepler were alive today, and could study the work of Newton and Einstein, don't you think he'd have anything to offer? We need an intellect of that magnitude now - with a spirit that won't be cowed by the traditionalists who wrap themselves in Einstein's achievements and refuse to admit that there might be a more accurate alternative to GR.
     
  6. Sep 14, 2004 #5

    marcus

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    I havent read the paper yet, just looked at the abstract. he says he focuses on changing ALPHA

    how do you picture alpha's significance?
    I am trying to imagine a movie of a hydrogen atom as it changes as a result of alpha increasing or decreasing (a kind of "time lapse" photo over billions of years of slowly changing alpha)

    if alpha were increasing would the light from a hydrogen atom gradually get bluer or would it get redder?

    maybe someone has already visualized this and can say, or has wondered about it. and the article that Chronos linked may spell this out.

    here is the abstract:
    "I briefly present some current theoretical motivations for time or space variations of the fundamental constants of nature and review current key observational results. I focus on the fine-structure constant, and particularly on measurements using quasars and the cosmic microwave background. I also compare various observational results to the simplest model-building expectations."
     
  7. Sep 14, 2004 #6

    marcus

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    the dude seems to be reputable. he is from Cambridge
    and his papers go back a ways. I will check a little more.

    if we believe him (which it seems like we might) the he says
    that he has checked and alpha has not changed very much since
    z = 1000 (the orgin of the Background)
    and also he claims to have checked back as far as z = 1010
    and also found that alpha has not changed since then by
    more than a few parts per thousand!

    this is impressive constancy! he goes back to BBN (big bang nucleosynthesis) and alpha has scarcely changed------he bounds the change within a percent either way!

    this is his equation (12) and (13) which cite references to papers by him and co-authors

    24. C.J.A.P. Martins et al., Phys. Rev. D66, 023505 (2002).

    25. C.J.A.P. Martins et al., Phys. Lett. B585, 29 (2004).

    I will see if I can find a preprint for the most recent.

    this is his reference 25. in online preprint form:
    http://arxiv.org/abs/astro-ph/0302295

    here is his reference 24. in case anyone wants to go back that far
    (2002, he has bounded the variation in alpha more tightly since then)
    http://arxiv.org/abs/astro-ph/0203149
     
    Last edited: Sep 14, 2004
  8. Sep 14, 2004 #7

    Chronos

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    Well done, Marcus. You caught the gist of it.
     
  9. Sep 17, 2004 #8

    Nereid

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    I'm mildly surprised that turbo-1 and Garth didn't quote the third and second (respectively) 'key developments required', towards the end of the paper.

    Being cheeky, perhaps it's because Martins' paper is concrete proof that the New Scientist open letter on cosmology contains significant misrepresentations?

    And of course, we certainly need a lot more theoreticians, to clarify the 'deep theoretical issues' :biggrin:
     
  10. Sep 17, 2004 #9

    turbo

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    Quoting "key developments two and three" of his paper would have been hauling coal to Newcastle. As you well know, I have made the point on a number of occasions that gravity may behave differently (to put it mildly) on large scales than is currently predicted in standard cosmology AND that the quantum gravity folks may have to break the equivalence principle to develop a dynamic model for the mechanism through which gravity and inertia arise. I have been reading papers and searching out possible mechanisms for this behavior (including gradients in the ZPE fields, which I think holds promise). Similar statements on my behalf have resulted in your "suggesting" to the Mentors that the threads be immediately shoved off to Theory Development. Such ideas are common amongst people trying to unify the most important theories in physics, but there are certain folks who apparently are very disturbed by them. :uhh:

    Distateful as it may be to some conservative cosmologists, there might be "constants" in our physics that are variable, especially in extreme situations, like domains populated with huge masses or very high energies. I wish I had stayed in engineering instead of moving on to liberal arts - these are exciting times for theoretical physics.
     
    Last edited: Sep 17, 2004
  11. Sep 18, 2004 #10

    Garth

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    Apart from the fact that Martins' (and Barrow's) papers are an example of heterodox theory, exactly what misrepresentations does the open letter contain?
    - Garth
     
  12. Sep 19, 2004 #11

    Nereid

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    "In no other field of physics would this continual recourse to new hypothetical objects be accepted as a way of bridging the gap between theory and observation." Perhaps some time taken to study the history of particle physics in the 20th century would be time well spent.

    "What is more, the big bang theory can boast of no quantitative predictions that have subsequently been validated by observation." I note that Chronos addressed this, and other misrepresentations, earlier.

    And Martins' paper, if an example of heterodox theory, provides rich counter-examples to the New Scientist letter's claim that "Today, virtually all financial and experimental resources in cosmology are devoted to big bang studies." For example, studies into the small-scale behaviour of gravity are being funded; look at the long list of alpha experiments and observations - are you (as a signatory) claiming that these were all carried out without any funding?
     
  13. Sep 19, 2004 #12

    Nereid

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    So, if Martins' paper's three key developments are:
    "First, one would like to have a post-Planck, CMB polarisation-dedicated satellite experiment." (presumably such a satellite would be welcomed by all cosmologists, no matter what their party affiliations?)

    "Second, one needs further, more stringent local tests of Einstein’s Equivalence Principle." (and Martins goes on to describe several experiments whose funding is at various stages of approval)

    "Third, one needs tests of the behaviour of gravity. Because it is so much weaker than the other forces of nature, it is quite hard to test the behaviour of gravity, and surprisingly little is known about it on many interesting scales. There has been a recent surge of interest in laboratory tests on small scales (and further improvements are expected shortly), but experiments that can test it on very large (cosmological) scales are still terra incognita. This is relevant because in theories with additional spacetime dimensions gravity is non-standard on large enough and/or small enough scales. Furthermore, a non-standard large-scale behaviour could also be an alternative to the presence of dark energy (a topic of much recent interest, but beyond the scope of this article)."

    why not mention that a) there is considerable interest in doing experiments and making observations which are of relevance to non-standard cosmological models? b) several such experiments and observations are, in fact, already planned and more are in the pipeline for funding?
    Is this not a rather good description of an ideal candidate thread for Theory Development? I notice that recently the PF Mentors and admins have changed the policies, and a great many threads in TD are now locked. Personally I would welcome some TD threads which could be examples of what TD is supposed (IMHO) to be about.
    I'm sure there are some conservative cosmologists; I'm equally sure there are some iconoclast, curious, broad-minded {insert your favourite antonym for 'conservative' here} ones. Many in the latter group probably have a strong interest in finding some really cool new things. However, I would hope that they all - conservative and non-conservative - will continue to insist on doing good science.
     
  14. Sep 19, 2004 #13

    turbo

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    Regarding funding: the relevance of planned projects to non-standard cosmological models is frequently quite incidental. For instance, Garth is looking forward to the data that will come from GPB, but that project was not launched to test his theory. In fact, some GR adherents have opined that the GPB money would have been better spent elsewhere because its confirmation of GR is a foregone conclusion. You haven't missed those comments, have you? GLAST will not be launced to test Fotini Markopoulou Kalamara's conjecture that the high-frequency gamma rays might be slowed by their interaction with the fabric of space-time. She has studied the project and has determined that the data might make her model falsifiable. Good science on a budget.

    Certainly not! If you search the literature on gravitation, you will find many references that suggest breaking the equivalence principle at some scale, and you will find that physicists as far back as 40 years ago (Andrei Sakharov) have been looking at interaction with ZPE fields as a possible source of gravitation/inertia. If those subjects cannot be raised in this forum without risk of banishment to TD, we are in some serious trouble. People working with these concepts are trying to extend the applicability of GR and explain the fundamental mechanism behind gravity. That work is fundamental and valuable, not heretical.

    Agreed!
     
  15. Sep 19, 2004 #14

    Garth

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    Of course science progresses by theoreticians introducing hypothetical postulates/objects/particles, or whatever. However, normally they are treated as hypothetical until proven otherwise. By contrast in cosmology the hypothetical Inflation, DM & DE are already treated as hard science. For example, one of my papers was rejected for publication by Classical and Quantum Gravity, and the referee gave, amongst other reasons, "recent large-scale astrophysical observations unequivocally showed that the our Universe is expanding, and that this expansion is accelerated, and that we really have dark matter and dark energy in the Universe."

    So that is that then - we haven't discovered a Higg's particle, we haven't discovered DM in the laboratory and we have no idea what DE might be; but they cannot be questioned. It is for these reasons that I signed that statement.

    GR predicted expansion or contraction (not acceleration) but makes no prediction of density, SCC does. Inflation did make the prediction of scale invariant CMB anisotropies, but other theories do so as well, and whereas the CMB data can be made to fit, with the addition DM and DE, it does not predict the low frequency end of the angular power spectrum.
    In individual universities groups of theoreticians are beavering away at all sorts of hypothetical theories and approaches. They are being paid or funded for basic blue-sky research by their institutions. Experiments are being funded to look for small deviations from GR but there is a problem in getting specific funding for a heterodox approach that falls outside a fairly small box. Some signatories were signing from their frustration and therefore others may think they have overstepped the mark - but it does depend on where you draw the mark.
    - Garth
     
  16. Sep 20, 2004 #15

    Nereid

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    And I say, let's see some clear, definitive work done to analyse the TB (maybe even PB by now) of data that is already in the public domain, to show consistency with a previously published prediction (or three) from an alternative approach. Preferably one which was not predicted by standard cosmological models.

    It could be that none of the alternatives makes predictions that are significantly different than those from standard models, at least wrt what's already in the TB of observational data. If so, then those pushing an alternative will have to wait a while (or significantly improve their sales and marketing skills).
    Personally, I'd like to see TD become a forum for discussing just such work as Sakharov's; instead of banishment, it should be seen as 'the right thing to do' (of course, maybe we should also move the 'Strings&Branes&LQG' section to TD too! :wink: - that'd be just fine with me).
     
  17. Sep 20, 2004 #16

    Garth

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    Nereid, Apart for the cosmological parameters, for which it is a concordance, freely coasting, model without Inflation, DM or DE; and all the standard tests to date where it yields identical predictions to GR; SCC predicts:-
    1. A Pioneer anomalous sunwards acceleration equal to cH - caused by a time slip between ephemeris time and atomic clock time.
    [see Ostermann, P. : 2002, arXiv:gr-qc/0212004. Relativity Theory and a
    Real Pioneer Effect]
    2. A spinning up of rotating bodies such as the Earth when compared to the period of an orbit such as the Moon at a rate equal to H. This has indeed been observed and reported in a review by Leslie Morrison and Richard Stephenson from the analysis of the length of the day from ancient eclipse records. They report that in addition to the tidal contribution there is a long-term component acting to decrease the length of the day, which equals:
    DT/day/cy = −6 x 10^−4 sec/day/cy, which is exactly equal to a Hubble's constant of 67 km/sec/Mpsc.
    [Morrison, L. & Stephenson, F.R.:1998, Astronomy & Geophysics Vol. 39
    October. The Sands of Time and the Earth’s Rotation
    Stephenson, F.R.:2003, Astronomy & Geophysics Vol. 44 April. Historical
    eclipses and Earth’s rotation.]

    As we know SCC predicts a geodetic precession from GPB of 5.5 not 6.6 arcsec/yr., together with a limit to the maximum Casimir force dependent on curvature and the fact that photons 'fall at 3/2 the rate of particles.
    These are published predictions that await testing Therefore the theory is falsifiable.
    As for GR as I have already posted on this thread we have the following problems:
    1. Inflation - no Higgs boson
    2. Dark Matter - undetected in laboratory experiments after three decades of intense research.
    3. Dark Energy - ditto.
    4. No large angle fluctuations in the CMB WMAP data, is the universe flat and infinite or finite?
    5. False vacuum fine-tuned to one part in 10^(102).
    6. Densities of Dark matter, energy and baryons all approximately equal (to within an order of magnitude)
    7. The small value of the false vacuum energy is unstable to quantum corrections - if interpreted as a small positive cosmological constant then it is incompatible with String theory.
    8. Galaxy mass profiles predicted by the standard theory have too pronounced a cusp at small angles and a too steep galaxy luminosity function.

    I fail to see what the problem is in suggesting that approaches other than GR ought to be taken more seriously.
    Garth
     
    Last edited: Sep 20, 2004
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