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Thread: Homogeneous and Isotropic?

  1. #1
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    Homogeneous and Isotropic?

    The Cosmological Principle asserts that the universe is relatively homogeneous, and isotropic at large scales. For about a decade, Lior Shamir, has analyzed large data,sets of galaxy surveys, using the same algorithms, the same computers, the same telescopes, and striving to use data cuts that eliminate possible overlapping images, to determine the relative abundance of clockwise and counterclockwise spins of the galaxies seen. He defines an asymmetry in the population as the difference of the two populations, divided by the sum of them.
    He found in his earlier survey of the Northern hemisphere, a significant difference in both the direction that he looked ( anisotropic) , and the distance at which he looked ( redshift).
    A number of scientists raised questions about the methodology, and he wrote a paper on the computational reasoning, answering them. ( below).
    Now he has completed a matching survey of the Southern Hemisphere, analyzing 807,808 galaxies in the final data set, with the same algorithms, and computer systems as before, over about 9 months of time, from the Southern galaxy surveys, and finds once again, a distinct asymmetry, significant at 4.66 sigma, except I'm airror image to the Northern result, and with an axis close to the well known CMB cold spot. Despite meticulous, exhaustive considerations of possible sources of error, the result seems to hold up, and offers a new perspective for the community to theorize.
    Paper to the Publications of the Astronomical Society of Australia...see for Southern Hemisphere
    https://arXiv.org/abs/2106.07118

    First paper on Northern Hemisphere, SEE:
    https://arxiv.org/abs/2007.16116

    paper on analysis techniques, SEE:

    https://arxiv.org/abs/2101.04068
    Last edited by trinitree88; 2021-Jun-16 at 04:02 AM. Reason: paper link, typo

  2. #2
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    I think the scale we're looking at is too small to really judge homogeneity. Our Observable Universe is a dust mote compared to what's outside our tiny bubble. Things might smooth out when you zoom out. Or not, of course.

    As for isotropy, we're learning now that symmetry is not guaranteed on the quantum level; why should it be on the cosmological level? Matter wouldn't exist if perfect symmetry were the rule.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  3. #3
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    Quote Originally Posted by trinitree88 View Post
    The Cosmological Principle asserts that the universe is relatively homogeneous, and isotropic at large scales. For about a decade, Lior Shamir, has analyzed large data,sets of galaxy surveys, using the same algorithms, the same computers, the same telescopes, and striving to use data cuts that eliminate possible overlapping images, to determine the relative abundance of clockwise and counterclockwise spins of the galaxies seen. He defines an asymmetry in the population as the difference of the two populations, divided by the sum of them.
    He found in his earlier survey of the Northern hemisphere, a significant difference in both the direction that he looked ( anisotropic) , and the distance at which he looked ( redshift).
    A number of scientists raised questions about the methodology, and he wrote a paper on the computational reasoning, answering them. ( below).
    Now he has completed a matching survey of the Southern Hemisphere, analyzing 807,808 galaxies in the final data set, with the same algorithms, and computer systems as before, over about 9 months of time, from the Southern galaxy surveys, and finds once again, a distinct asymmetry, significant at 4.66 sigma, except I'm airror image to the Northern result, and with an axis close to the well known CMB cold spot. Despite meticulous, exhaustive considerations of possible sources of error, the result seems to hold up, and offers a new perspective for the community to theorize.
    Paper to the Publications of the Astronomical Society of Australia...see for Southern Hemisphere
    https://arXiv.org/abs/2106.07118

    First paper on Northern Hemisphere, SEE:
    https://arxiv.org/abs/2007.16116

    paper on analysis techniques, SEE:

    https://arxiv.org/abs/2101.04068
    That is rather tantalising. So if I understood correctly , the net observed spin is opposite in the southern hemisphere relative to the Northern. These relative to the axis CMB “cold spot”” .I think I need a diagram.

    At one level it is kind of nice that the asymmetries cancel, or tend to, an overall spin would have to be there at the big bang. And some clockwise some anticlockwise would be expected from random interactions, again about equal for a fair cosmos, but separated out is going to take some explaining.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Profloater. Agreed. It will take some careful theorizing, and of course, need to be double-checked as more surveys come in. It would be very interesting if the JWST confirms the effect in the infrared, once it is up, and yielding datasets. pete

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    Caveat - this was from a quick read. If I were to provide these as review comments I'd spend an evening or so with each paper, not ten minutes!

    The biggest double check needs to be on the Ganalyser tool. I flipped through the author's own assessment of it and there are some gaps in what has been tested. The error analysis also doesn't seem to properly cover the misclassification issue. If you took the naive misclassifcation result (which was on a nicely conditioned dataset) and applied it to the populations then the difference is within the uncertainty of the tool. There is also an assumption that the misslcassifications and indeterminate results are symmetric and not biased which I didn't see a strong proof of. It is not a bad assumption but it is an important one to check.

    Overall it is interesting but the tools used need serious peer review and the analytical method needs to be checked more fully (and more robustly - there were a lot of assumptions about the underlying distributions of the data that were reasonable but for a claim like this need double checking).

    Lastly there needs to be more smart averaging rather than simple binning. If there is a filament bias then the results need to be averaged at this scale to restore homogeneity and isotropy.

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