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WMAP has conclusively proven an expanding universe.

  1. Jul 3, 2004 #1

    Chronos

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    WMAP has conclusively proven an expanding universe. anyone care argue?
     
  2. jcsd
  3. Jul 3, 2004 #2

    turbo

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    That's probably a little strong.

    It's my understanding that some variants of the inflationary model of the Big Bang are invalidated by the WMAP findings, while some others fit the observations well enough to remain viable.

    There are a lot of ways to skin that "universal expansion" cat, and even if COBE and WMAP had shown the CMBR to be absolutely smooth, there would have been some factions of the Big Bang cosmologists dancing and clapping their hands.
     
  4. Jul 3, 2004 #3

    marcus

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    turbo gave a savy answer so I agree some with that

    also I would put it this way:

    nothing is ever conclusively proven
    people build models and check them against observation
    and they can always be modified, refined, merged with other models etc.

    the overarching fact of cosmology is that General Relativity
    is the model of spacetime geometry and gravity that works
    and it has just gotten more and more credible in the years since 1915
    and there is no serious competition (at least until recently)
    and the GR model predicts that the scale-factor increases with time

    and things like observing redshifts and WMAP and COBE etc are just fitting in additional detail, and confirming and showing consistency

    wmap data does not "prove" unless you have the model first, to fit the wmap data into

    if you have the model then you already know that the U is expanding (unless it is contracting, which doesnt seem likely)

    if you want to defeat the idea that the U is expanding then the first thing you have to do is say Einstein was wrong in 1915 and GR is wrong
    and since it is the prevailing model of how gravity works
    you have to come up with an alternative model of gravity
    then people must devise tests for that model of gravity that show it is better

    so if you want to destroy the idea of U expanding you must destroy GR
    and replace it with a model that is better at predicting the little effects that people measure in order to test GR

    because it is GR (not some particular satellite observatory like wmap)
    which predicts either expansion or contraction (which does not seem to be happening)
     
  5. Jul 3, 2004 #4
    IN terms of the singularity, a certain assumption is made? If the universe has always existed, would this not defeat any questions in relation to such a beginning? It does not debate the expansitory nature as irrelevant.

    It sort of throws in the question of whether or not Colliding branes might have some value in that discussion, since it is recogized that this singularity can be very cyclical. We have not even defined it's beginnnings or the finality of the blackhole here.

    Again focus is on the universe as always existing and not arrived at fom some singuarity would have been a observation that might speak to the expansitory mode as well as the ability within that universe to demonstrate new opportunities for more universes to come.

    If such overall dynamics are visualized in "progression" Gamma ray detection is worth moving forward this idea in localities of this universe?

    Does this speak directly to the originator of this thread?
     
  6. Jul 3, 2004 #5

    turbo

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    Marcus, regarding gravity and GR.

    It can be argued that we don't understand gravity well enough yet to model familiar objects like spiral galaxies without resorting to some tricks. It is well-demonstrated that the observable components of spiral galaxies do not conform to the expected rotational norms. We would expect very high rotational velocities near the core of the galaxy, decreasing smoothly with increasing radius. Instead, rotational velocity increases very sharply near the core of the galaxy, then flattens out, so the galactic arms appear to be rotating as if they were fixed on a solid disk.

    To explain this anomalous rotation within the GR framework, cosmologists have postulated the existence of a huge cloud of dark matter around every such galaxy (perhaps 9-10 times as much mass as the visible part of the galaxy). Not only is the amount of necessary dark matter very large, it must be distributed in a manner that is not consistent with the distribution of the visible matter. This is a very large assumption. Conventional cosmologists allow this huge fudge factor to stand because it is necessary to protect the integrity of GR - a very sacred thing to the status quo. Explaining away anomalous observations with unproven (perhaps unprovable) assumptions is bad science, though. As Stevie Wonder says "When you believe in things that you don't understand, you will suffer."
     
    Last edited: Jul 3, 2004
  7. Jul 3, 2004 #6
    This came Friday
    http://arxiv.org/abs/astro-ph/0407027
    Bayesian Power Spectrum Analysis of the First-Year WMAP data
    Authors: I.J. O'Dwyer, H.K. Eriksen, B.D. Wandelt, J.B. Jewell, D.L. Larson, K. M. Gorski, A.J. Banday, S. Levin, P.B. Lilje
    Comments: 5 pages. 4 figures. To be submitted to ApJL. For additional information and data see this http URL

    We present the first Bayesian analysis of the WMAP first year data using a Gibbs sampling technique. We use two independent, parallel supercomputer codes to sample from the posterior density of the power spectrum given WMAP data from the Q, V and W bands. In addition, we sample from the power spectrum posterior using data from all eight channels in these bands. The analysis results in a full probabilistic description of the information the WMAP data set contains about the power spectrum and the all-sky map of the cosmic microwave background anisotropies. In this letter we present the marginalized likelihoods P(C_l|d) at each l and compare them with previous power spectrum estimates. We find good agreement with the previously published WMAP spectrum. Additionally, our method provides us with the complete probability distribution for each C_l so we are able to provide a detailed assessment of the errors, including any non-Gaussianities of the power spectrum likelihood. This allows us to examine some areas of interest in the power spectrum such as the power at low multipole l. We also present a simple way for comparing model predictions at the lowest l to the analysis combining the WMAP Q, V and W band data.


    and this Thursday
    http://arxiv.org/abs/astro-ph/0406670
    Inflation After WMAP
    Authors: William H. Kinney (Univ. at Buffalo, SUNY)
    Comments: 8 pages, 4 figures. To appear in the proceedings of the XXXIXth Rencontres de Moriond "Exploring the Universe"

    I examine the status of inflationary cosmology in light of the first-year data from the WMAP satellite, focusing on the simplest models of inflation: those driven by a single scalar field. The WMAP observation of the Cosmic Microwave Background is the first unified, self-consistent data set capable of putting meaningful constraints on the inflationary parameter space. WMAP provides significant support for the inflationary paradigm in general, and single-field slow-roll inflation models provide a good fit to existing observational constraints
     
  8. Jul 4, 2004 #7

    Chronos

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    Marcus is correct. Expansion is not 'conclusively proven'. WMAP merely affirms the GR model predicts and, once again, matches observations. I am curious, however, how WMAP results conflict with BBT. I thought quantum fluctuations in the CBR were expected, not contraindicated.
     
  9. Jul 5, 2004 #8

    Nereid

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    It's sure infuriating that this DM can't be characterised better than some of its bulk properties!

    However, for those who don't like the whole DM idea, it must surely also be infuriating that the DM shows up in so many different kinds of observations, and they all give approx the same estimates of its mass, density, distribution, etc (to within the observational errors, which aren't all that tight) ... which just happen to match what the cosmologists need for their models to match WMAP (etc). OK, this isn't really how it works, but where are the alternative, non-DM models which account for even a large subset of the good observations? MOND, do I hear you say?? Not even Milgrom would claim its applicability is quite limited (and clearly fails several observational tests). :wink:
     
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