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Someone flow about dark flow.

  1. Feb 8, 2012 #1
    Here, Here, and for you forum nazi's Here. :p (just to point out thats a smiley with a tongue out, indicating im joking, lmfao) (last one is a peer reviewed paper originally submitted to "The Astrophysical Journal Letters")

    Now with the formalities out of the way, the good stuff. What would this mean to our standard cosmology model, the big bang and all that? Would this really be considered another body outside the universe exerting gravity on the stuff in ours?How credible is this claim?(it was the popular explanation I have seen while browsing search results) Or would it be a killing blow to the big bang?(I know nothing said would be a sure thing but I would like to hear some thoughts from some experts about what they think it would mean and maybe what their colleagues think as well)

    Now, if there is some newer studies debunking these results then please inform me, tho I have not found anything conclusively denying the findings. Also, if I may ask that everyone give their personal opinion on what this, or other strong evidence could mean for the big bang theory. I personally feel that with my very limited knowledge, I find the big bang theory to not be the most comfortably correct idea. Now when I say limited, I mean it; my own opinion means next to nothing to me at this point :p I have heard a wide range of professionals speak their gripes about the BB theory during my studies, but none offered an alternative. So to speed this question along, What other well supported theories that offer solutions to the problems of the BB theory are there? What is your personal belief on the Big Bang and on these new dark flow findings. What are the beliefs of the majority of professionals in this field of cosmology?

    Just to avoid any problems, I am asking alot of questions here. Not making any over speculative claims. Please allow someone the chance to correct any misconceptions I have and answer any of the questions I have asked before you decide to delete the topic. Thank you! :)
  2. jcsd
  3. Feb 8, 2012 #2
  4. Feb 8, 2012 #3


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    Why? It's the best fit for all current observations. Keep in mind that there are MANY people who are uncomfortable with the BBT don't actually know what it's about. Every single alternative theory I've seen is far more speculative. What about it do you find uncomfortable?

    What kind of professionals? If they haven't studies the theory much, then what do they know about it?
  5. Feb 8, 2012 #4


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    The links talk about a mass concentration beyond the observable universe, not from outside the universe. The observable universe is just that part of the universe for which light has had time to reach us since the Big Bang, it does not represent what we would consider the entire universe. So in essence, they mean something still part of the universe, just not something that we could, in principle, see.
  6. Feb 8, 2012 #5
    Thats even more interesting, thanks for clarifying.

    As for the BBT, I guess you already answered one of my questions when you said all other theories are even more speculative. But what are those?
  7. Feb 9, 2012 #6


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    In the paper you quoted for "forum nazis" (I don't know what that means) the authors conclude that the peculiar velocities measured are

    "Conventionally, the entire peculiar velocity field is assumed to be driven by the peculiar gravitational potential."

    This conclusion may not be correct; the velocities may be due to something else.
  8. Feb 9, 2012 #7
    inside joke kinda. I had alot of topics deleted for asking questions that were to speculative.

    And can you explain more, what else could it be from>
  9. Feb 9, 2012 #8
    Any new hypothesis or theory that seriously challenges a previously well established one is initially resisted. If it doesn't fit then ways to make the new data fit are sought. If it still doesn't fit then ways to disprove it are sought. The problem with the Black Flow is exactly that. It tends to disrupt the idea that the galaxies were not all moving in one uniform direction. If indeed the new idea were to be accepted then that would necessitate a readjustment of all extrapolations to the unseen universe as well as a new understanding of Big Bang in order to account for this peculiar motion. Here are two relevant articles.

    Last edited: Feb 9, 2012
  10. Feb 9, 2012 #9


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    “THE ERROR BUDGET OF THE DARK FLOW MEASUREMENT” paper is a discussion about the measurement of the CMB for peculiar velocities using the cumulative Sunyaev–Zeldovich (SZ) effect. While it is useful for understanding how the “dark flow” has been discovered and measured, it does not contain any hints of what’s causing that flow.

    The second link, http://iopscience.iop.org/0004- [Broken]. is broken.

    The third link is nearly two years old, and is just speculation.

    As for the OP, it remains to be answered.
    Last edited by a moderator: May 5, 2017
  11. Feb 9, 2012 #10
    I deleted that first link.

    The second link I just fixed but cannot guarantee it isn't too old for your taste. But thanks for pointing that out.

    You are right, the third link deals mostly with speculation. However it is on topic and fascinating nevertheless. IMHO

    As for the question, some questions posted here have no definitive answers and can only be theoretically or hypothetically discussed or both sides of the issue considered since no scientific consensus has as yet been reached or else is in the process of being reached.

    I fixed the link. Thanks for pointing it out.. 
    Last edited by a moderator: May 5, 2017
  12. Feb 10, 2012 #11
    Hello. I'm new to this forum, and I've been reading lots of interesting stuff under the Cosmology Heading, which is where my main interest lies. I also chanced upon this thread under the Astrophysics Heading, and I've read about the Dark Flow Theory when it first came out, elsewhere. Quite interesting all this is, especially the Dark Flow idea.
    I would like to thank Janus for putting into words a concept that I've struggled with for years. Now I understand that our observable universe lies within the Greater Universe, and the Greater Universe can indeed be infinite. I now realize that it could be possible for other universes such as our own observable universe to exist, each possibly separated by untold mega or giga-parsecs in the Greater Universe. If other universes such as our own(or not like our own!) indeed exist, then does it seem not too far-fetched that those other universes could make their presence known to us by the mass they have, long long before we could ever see them?
    If galaxies can merge into other galaxies and create all sorts of different shapes and sizes of galaxies afterwards, over very long periods of time, then I wonder if it could be possible for our observable, or home universe, to merge in the very far future with another universe which might be a home universe to other intelligent beings.
    If such a merger was possible, that would be quite an interesting event, if we could even be aware of it happening. Now, if anything I just pondered about here is full of errors, please point those out for me, please. I really want to get a handle on these ideas, to wrap my mind around them. Thank you!
  13. Feb 10, 2012 #12


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    Here is a paper that disputes the Kashlinski, et al paper:

    The Statistical Significance of the "Dark Flow"
    Authors: Ryan Keisler
    (Submitted on 22 Oct 2009)

    We revisit the statistical significance of the "dark flow" presented in Kashlinsky et al. (2009). We do not find a statistically significant detection of a bulk flow. Instead we find that CMB correlations between the 8 WMAP channels used in this analysis decrease the inferred significance of the detection to 0.7\sigma.

    We have revisited the analysis presented in Kashlinsky et al. (2008, 2009) which reports a significant detection of a bulk flow of _700 galaxy clusters out to z ' 0:1
    by means of the kSZ effect. We have demonstrated that the estimates for the kSZ signal are highly correlated between the different WMAP channels used in this analysis and that this correlation is caused by primary CMB anisotropy. We have simulated the errors on the kSZ measurement while taking into account these CMB correlations and find that there is not a significant detection of a kSZ signal or bulk flow.
  14. Feb 10, 2012 #13


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    This seems completely reasonable to me. WMAP is only barely sensitive enough to detect the primary SZ effect, and the kSZ effect is much, much smaller. I find it positively silly to think that Kashlinsky et al. could think that they were actually seeing the kSZ signal in WMAP, instead of just the primary CMB anisotropies.
  15. Feb 10, 2012 #14
    My limited itelligence prevented me from understanding what that paper means bobby. Can someone explain?
  16. Feb 10, 2012 #15


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    One way of looking at it is that they did some simulations of the CMB, then repeated the analysis by Kashlinsky et. al. that detected the dark flow, except this time on the simulated CMB sky. What they found is that in their simulations, which had no dark flow at all, they saw the exact same kind of measurement of a "dark flow" that Kashlinsky et. al. found.

    So basically this just means that the "dark flow" is a result of failing to properly understand the errors in the CMB itself. It has nothing to do with anything actually moving, just normal differences in temperature in the CMB sky.
  17. Feb 10, 2012 #16


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    Oh, fellupahill! Please, never degrade your intelligence level. Plenty of very intelligent folks learn lots of things in their areas of study. Just as a neurosurgeon could not fix my sonar set, I could not operate on someone’s brain.

    For those who want to know what basic technique is used to measure peculiar velocities of galaxy clusters using the CMBR via the “kSV” effect:

    This is more background information from 1995, showing the feasibility of measuring peculiar velocities using the kSZ effect: “Using the kinematic Sunyaev-Zeldovich effect to determine the peculiar velocities of clusters of galaxies”
    Authors: Martin G. Haehnelt, Max Tegmark
    http://arxiv/abs/9507077 [Broken]

    Here is a recent paper that confirms a peculiar velocity and gives two impacts on cosmology: “The dark flow induced small scale kinetic Sunyaev Zel'dovich effect”
    Author: Pengjie Zhang (SHAO)
    (Submitted on 7 Apr 2010 (v1), last revised 6 Jul 2010 (this version, v2))

    We have pointed out the existence of the dark flow induced small scale kinetic SZ effect and estimated its amplitude. As a potentially non-negligible component of CMB temperature fluctuations, it impacts cosmology in at least two ways.

    • It enables a useful independent check on existing dark flow measurements (Kashlinsky et al. 2008, 2009; Atrio-Barandela et al. 2010; Kashlinsky et al. 2010). The direction-weighted CMB-LSS cross correlation measurement proposed in this paper should be able to detect a dark flow with an amplitude of & 500 km/s at & 3_ level for WMAP+2MASS. Planck+2MASS can improve the detection threshold to 200 km/s. Given this sensitivity, it will allow for a strong test of the existence of the dark flow.

    • A dark flow of the reported amplitude ~10^3 km/s can significantly bias the ISW measurement through the CMBLSS cross correlation, if the survey area is sufficiently close to the direction of the dark flow or the opposite of it. Hence
    it can significantly bias the dark energy constraint based on the ISW interpretation. Existing data shall be reinterpreted to avoid such bias.
    Last edited by a moderator: May 5, 2017
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