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Thread: "Wide binaries" to test for MOND

  1. #1
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    "Wide binaries" to test for MOND

    I noticed this recent paper in arxiv.org Astrophysics new submissions: Detailed numerical implementation of the wide binary test. That sounded like a pretty straightforward test to determine whether MOND correctly describes gravity in the very low gravitational regime.

    Looking into this a little more, I noticed this 2012 paper ("Wide binaries as a critical test of classical gravity") that claims to have performed the necessary measurements for some number of wide binaries, and the paper claims "Our results are suggestive of a breakdown of Kepler’s third law beyond aa 0 scales, in accordance with generic predictions of modified gravity theories..."

    If the orbits and other necessary measurements were made in this 2012 paper, why do the authors only say that their results are "suggestive" that MOND is correct? Did they not have a large enough sample of wide binaries? Or what? (I only have access to the abstract.) I wonder what happened to this line of research. Surely any definite finding would be pretty important!
    Everyone is entitled to his own opinion, but not his own facts.

  2. #2
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    The full arxiv version of the paper is here.
    I've only skimmed it, but the authors' reservations appear to be based on wide error bars and the possibility of alternative Newtonian explanations.

    Grant Hutchison
    Science Denier and Government Sponsored Propagandist. Here to help.
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  3. #3
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    The Cheshire EFE

    The 2012 WBT was the first one done with data available at the time. Latter, GAIA became available. One of the early concerns raised was with regard to projection effects. From an artificial sample of purely Newtonian binaries when viewed from some projection showed MOND characteristics:

    The geometric challenge of testing gravity with wide
    binaries

    https://arxiv.org/abs/1810.13397

    Latter Hernandez et al revisited the WBT using GAIA data as well in 2019 and 2021 with a larger sample featuring a number of data cuts that included projection effects and continued to see the MOND signal:

    Challenging a Newtonian prediction through Gaia wide binaries

    https://arxiv.org/abs/1810.08696


    Internal kinematics of GAIA eDR3 wide binaries.
    https://arxiv.org/abs/2107.14797

    Two observations were made. For CDM to form a mini halo about a binary that reached sufficient distance separation to account for the anomaly(no anomaly observed within the distance hence no need for a mini halo in these instances) the sum of all these halos would cause an overweight CDM problem not to mention how CDM “knows” when to form a halo for some binaries and not others.
    The other intriguing observation is that the signal appears to be free of the EFE like isolated galaxies. How is it suppressed or screened?

    For some, the external field effect of the Milky Way galaxy should on the order of a_0 leading to a slightly more Newtonian signal, an effective G, instead of the clear MOND in isolation signal seen by Hernandez et al.:
    Testing Modified Gravity Theories via Wide Binaries and
    GAIA
    https://arxiv.org/abs/1711.10867

    A new line on the wide binary test of gravity
    https://arxiv.org/abs/1902.01857

    Earlier, Chae et al looked for the EFE and found a high sigma signal that could be a “smoking gun” for MOND or similar theories as it is thought to violate SEP. 2 control galaxies far from others show flat rotation curves out to large distances, expected of MOND in isolation. Other galaxies in a more crowded environment show rotation curves that fall off on the outskirts which is a signature of the EFE:

    Testing the Strong Equivalence Principle: Detection of the External Field Effect in Rotationally Supported Galaxies
    https://arxiv.org/abs/2009.11525

    Yesterday, two papers came out with respect to SEP violation by the EFE. Another one by Chae et al:
    Testing the Strong Equivalence Principle. II. Relating the External Field Effect in Galaxy Rotation Curves to the Large-Scale Structure of the Universe
    https://arxiv.org/abs/2109.04745
    They see a 13 sigma signal which offers support to the “smoking gun” possibility

    However this other paper could not find support for the EFE:

    Probing the radial acceleration relation and the strong equivalence
    principle with the Coma cluster ultra-diffuse galaxies

    https://arxiv.org/abs/2109.04487
    The UDGs measure to retain rotation curves that remain flat like MOND in isolation even though they are thought to be in the well of the COMA cluster. The discussion is begun here as to what might cause the absence of the EFE looking to offshoots like EMOND among other ideas.

    This list is not comprehensive. It shows that research is ongoing that, as usual, raises more questions.

  4. #4
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    From galactic bars to the Hubble tension − weighing up the astrophysical evidence for

    arXiv:2110.06936

    Indranil Banik, Hongsheng Zhao

    Manik and Zhao conclude MOND is a better fit to the data than GR:

    Quote Originally Posted by Manik and Zhao
    Our overall assessment considers both the extent to which the data agree with each theory and how much flexibility each has when accommodating the data, with the gold standard being a clear a priori prediction not informed by the data in question. We also consider some future tests. Our conclusion is that MOND is favoured by a wealth of data across a huge range of astrophysical scales, ranging from the kpc scales of galactic bars to the Gpc scale of the local supervoid and the Hubble tension, which is alleviated in MOND through enhanced cosmic variance.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  5. #5
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    Retardation Effects in Gravitation

    Retardation Effects in Gravitation
    Asher Yahalom

    https://arxiv.org/pdf/1507.02897.pdf

    This paper caught my eye, and Yahalom has expanded this paper to a series of papers about his explanation of MOND/Dark Matter

    As I understand his thesis (with an unfortunate name); he contends that a galaxy is always increasing in mass due to the absorption of the intergalactic medium; and therefore the current viral mass calculations do not properly integrate the loss of intergalactic density (through absorption) relative to the core density of galaxies because of the relativistic time lag over the history of the galaxy.

    As always any new theory needs to both explain existing observations, and provide new tests, or incorporate new analysis of existing data that have either been overlooked or neglected.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

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