Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A message from bBeyond the red horizon? or just more epicycles?

  1. Jun 7, 2008 #1
    The BBC are reporting today that "A team of physicists has claimed that our view of the early Universe may contain the signature of a time before the Big Bang." This report traces back to a Arxiv article by Erickcek, Kamionkowski, and Carroll of Stanford in which it is stated that:

    "There is an anomaly in the CMB: measurements from the Wilkinson Microwave Anisotropy Probe (WMAP) ... indicate that the temperature-fluctuation amplitude is larger, by roughly 10% in one hemisphere than in the other. This power asymmetry occurs at the 99% C. L., and it cannot be attributed to any known astrophysical foreground or experimental artifact. This asymmetry has gone largely unnoticed".

    They go on to explaining this anomaly (that had been previously swept under some carpet?) by postulating a "superhorizon sinusoidal perturbation to (a) curvaton field" postulated by [URL="arXiv:hep-ph/0110096]Moroi and Takahashi [/URL] among others, that contributes to inflation. It's the superhorizon part that seems to have generated the signature mentioned by the BBC.

    Being in a curmudgeonly mood, I'm curious as to whether the cosmologial community have any comments on this development. Do they?
     
    Last edited: Jun 7, 2008
  2. jcsd
  3. Jun 7, 2008 #2

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    The net fluctuation is too near the resolution limit of WMAP to be conclusive - especially considering the data was calibrated to filter out foreground noise. This is always an imprecise process that stretches the error bar. The Planck mission should further clarigy matters. Scientists are tempted to speculate in the face of unrefined data, which is entirely understandable. Being lucky is usually better than being good.
     
  4. Jun 9, 2008 #3

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Sean Carroll give some background in his blog entry, The Lopsided Universe.
     
  5. Jun 10, 2008 #4
    Thanks, George, for this interesting link.

    Comparing the claim by Erickec et al. that:

    "This power asymmetry occurs at the 99% C. L., and it cannot be attributed to any known astrophysical foreground or experimental artifact"

    with Chronos' appropriate remark that:

    "The net fluctuation is too near the resolution limit of WMAP to be conclusive - especially considering the data was calibrated to filter out foreground noise. This is always an imprecise process that stretches the error bar. "

    leads me to conclude that Mark Twain was right when he wrote:

    "There are liars, damned liars and statisticians" !
     
  6. Jun 10, 2008 #5

    Wallace

    User Avatar
    Science Advisor

    Check the link George Jones posted to Sean Carroll's blog about this. It explains the statistics of this in a straightforward way.
     
  7. Jun 11, 2008 #6

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    Statistics rely upon assumptions. Sean Carroll makes too many bold assertions, IMO.
     
  8. Jun 11, 2008 #7
    When you think of what astronomers have actually done, perhaps so. First, the CMB was a stretch to detect at all; radiation from a source at 2.7K is not the most obvious thing in the universe. Then, secondly, accurately establishing the BB nature of this faint source's spectrum (COBE) is standing ovation stuff. And thirdly, showing that the source subtends 4pi steradians uniformly, to one part in 10^4, is an extra tour de force. As for establishing the angular power spectrum of temperature fluctuations below this level; well, fourthly, the collective persistence that has prevailed among WMAP analysers must be unprecedented.

    No wonder that the 10% perturbation discussed by Carroll, now a phenomenon at the 1 in 10^5 level from a faint source, is testing limits of analysis. But I still believe Mark Twain had the right take on statistical analysis.

    Nevertheless, I suppose there is no reason why the universe, perhaps in a pre-inflationary state, should not have extended past what is now our observable universe. Maybe there really are sea-serpents out there!
     
  9. Jun 12, 2008 #8

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    I did not intend to be argumentative, especially with Wallace - a professional. I merely wished to point out the LCDM model has no serious rivals.
     
  10. Jun 16, 2008 #9
    Maybe by lowering the frequency of the detector we can see what happened before the phase shift that we call the background radiation. I believe I read that someone is building a detector in the TV band. Has anyone any thoughts on that? Also if the big bang expanded at faster than light wouldn't at some point we reach a wall? I'm new to this physics help forum and I'm retired and no one I know wants to talk about cosmology. So please give me your thoughts.
     
  11. Jun 18, 2008 #10
    Hi,

    Imagine a universe a bit like ours, but with a finite total mass and a definable centre. Say the enclosing volume of the total mass is larger than the visable volume but not infinite, at the given epoch and that the uinverse is expanding. Such a universe would look infinite and unbounded and any observer, even one near the "physical edge" would appear to be at the centre of such a universe, due to a conspiracy of effects due to gravitational and kinematic time dilation, abberation etc. However, depending on the density of the universe, there would be some small anisotropies for any observer not exactly at the centre because the "conspiracy of effects" is not perfect. Could that be what is being observed here? Could it be that we have actually managed to detect our non central position in a finite universe? Just a thought :)
     
  12. Jun 18, 2008 #11

    Wallace

    User Avatar
    Science Advisor

    You would see this particular effect in the situation you describe. There is no large angle temperature anisotropy involved, rather the small small anisotropies are a greater amplitude (by a small amount) on one side than the other. I don't see how the situation you describe would give a gradient in fluctuation amplitude as you go out from the hypothetical centre of the Universe. I can see how this idea makes sense if there was a dipole temperature anisotropy, but not what is seen here.
     
  13. Jun 18, 2008 #12
    Key-- that is a deep thought but I've figured out that we are all at the center of the universe and would be no matter were we are located. If there is a reason for the 15% hotter hemosphere in the background radiation but it could be that the faster than light expansion didn't come to a symetrical stop due to fluctuations. This 4D bottle we are in is hard to visualize and I see the no center but if you are right it would really screw up my head to Visualize a universe were we are off center. I think we need more info.

    milt
     
  14. Jun 18, 2008 #13
    Just a small correction as it is Caltech not Stanford.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?