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Tugs from Beyond the Observable Universe

  1. Jun 20, 2012 #1
    Dark Flow: Tugs from Beyond the Observable Universe?
    Is this true ? If true then what lies Beyond the Observable Universe ?
  2. jcsd
  3. Jun 20, 2012 #2


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    Text is excerpt from:

    Astrophysicist Ned Wright posted an online response to the study arguing that its methods are flawed.[6] The authors of the "dark flow" study released a statement in return, refuting three of Wright's five arguments and identifying the remaining two as a typo and a technicality that do not affect the measurements and their interpretation.[7]

    A more recent statistical work done by Ryan Keisler[8] claims to rule out the possibility that the dark flow is a physical phenomenon because Kashlinsky et al. do not consider primary CMB anisotropies as important as they are.

    NASA's Goddard Space Center considered that this could be the effect of a sibling universe or a region of space-time fundamentally different from the observable universe. Data on more than 1,000 galaxy clusters have been measured, including some as distant as 3 billion light-years. Alexander Kashlinsky claims these measurements show the universe's steady flow is clearly not a statistical fluke. Kashlinsky said: "At this point we don't have enough information to see what it is, or to constrain it. We can only say with certainty that somewhere very far away the world is very different than what we see locally. Whether it's 'another universe' or a different fabric of space-time we don't know."[9]

    The existence and the velocity of dark flow will probably stay disputed until the new accurate cosmic microwave background radiation data by the European Space Agency's Planck satellite are available in 2012.[10]
  4. Jun 21, 2012 #3


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    Beyond the more detailed critique of Ned Wright here, I'll take a somewhat higher-level view.

    Kashlinsky et. al. attempt to use WMAP to detect what is known as the "kinetic SZ effect" to determine the motions of nearby galaxies. This is a prospect that is almost utterly doomed to failure. WMAP simply isn't built to measure the SZ effect, let alone the far more difficult to measure kinetic SZ effect. There just isn't any way to get a significant kinetic SZ effect signal from WMAP.

    Edit: Oh, and I'd also like to mention that for this particular measurement, Planck won't help. The statistical treatment is just bad. CMB statistics are a thorny problem that are somewhat difficult to get right. And failure to take into account the correlations of the CMB from place to place in the sky is just an utterly wrong thing to do.
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