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No dark matter

  1. Sep 24, 2014 #1

    wolram

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    http://arxiv.org/pdf/1409.6302.p [Broken]

    It is argued in this paper that Dark Matter does not exist, what do you think.
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Sep 24, 2014 #2

    BiGyElLoWhAt

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  4. Sep 24, 2014 #3

    wolram

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    Lessons from the Local Group (and beyond) on dark matter
    Pavel Kroupa (Bonn)
    Comments: 13 pages, 2 figures, invited presentation, accepted for publication in Seychelles conference on galaxy evolution, "Lessons from the Local Group", ed. K. C. Freeman, B. G. Elmegreen, D. L. Block, and M. Woolway (Dordrecht: Springer), in press, 2014
    Subjects: Astrophysics of Galaxies (astro-ph.GA)
    (Abridged) The existence of exotic dark matter particles outside the standard model of particle physics constitutes a central hypothesis of the current standard model of cosmology (SMoC). Using a wide range of observational data I outline why this hypothesis cannot be correct for the real Universe. Assuming the SMoC to hold, (i) the two types of dwarf galaxies, the primordial dwarfs with dark matter and the tidal dwarf galaxies without dark matter, ought to present clear observational differences. But there is no observational evidence for two separate families of dwarfs, neither in terms of their location relative to the baryonic Tully-Fisher relation nor in terms of their radius--mass relation. And, the arrangements in rotating disk-of-satellites, in particular around the Milky Way and Andromeda, has been found to be only consistent with most if not all dwarf satellite galaxies being tidal dwarf galaxies. The highly symmetric structure of the entire Local Group too is inconsistent with its galaxies stemming from a stochastic merger-driven hierarchical buildup over cosmic time. (ii) Dynamical friction on the expansive and massive dark matter halos is not evident in the data. Taking the various lines of evidence together, the hypothesis that dynamically relevant exotic dark matter exists needs to be firmly rejected
    Lessons from the Local Group (and beyond) on dark matter
    Pavel Kroupa (Bodwarfs with dark matter and the tidal dwarf galaxies without dark matter, ought to present clear observational differences. But there is no observational evidence for two separate families of dwarfs, neither in terms of their location relative to the baryonic Tully-Fisher relation nor in terms of their radius--mass relation. And, the arrangements in rotating disk-of-satellites, in particular around the Milky Way and Andromeda, has been found to be only consistent with most if not all dwarf satellite galaxies being tidal dwarf galaxies. The highly symmetric structure of the entire Local Group too is inconsistent with its galaxies stemming from a stochastic merger-driven hierarchical buildup over cosmic time. (ii) Dynamical friction on the expansive and massive dark matter halos is not evident in the data. Taking the various lines of evidence together, the hypothesis that dynamically relevant exotic dark matter exists needs to be firmly rejected
     
    Last edited: Sep 24, 2014
  5. Sep 24, 2014 #4

    wolram

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  6. Sep 24, 2014 #5

    wolram

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    http://www.thedailybeast.com/articl...ark-matter-from-space-station-experiment.html

    Nothing from satellite yet either.

    The experiment, which has been collecting particles for several years, has foundsomething interesting: an elevated number of positrons, the antimatter counterpart of electrons. However, fascinating as it is, AMS-02 isn’t seeing what we’d expect if dark matter was the culprit. While we can’t yet rule out the possibility that dark matter is responsible, what evidence there is seems just as likely to point to another source.
     
  7. Sep 24, 2014 #6

    Orodruin

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    From what I can tell from searching around a bit the author is a fairly strong supporter of MOND and arguments between MOND and dark matter proponents can some times get a bit heated. Just as several astrophysical explanations could be possible for the dark matter "signals" that have been popping up over the years, it guess it could be possible that we do not yet understand the astrophysics to the required level - although I am speculating here as it is not my area of expertise. It should be noted that there are also several observations that seem to support dark matter over MOND (the typical example you would hear is galaxy collisions such as the bullet cluster).

    In the end, if there is dark matter and it is interacting so weakly that we will never see it in the laboratory - we might never know. Certainly the "standard" SUSY WIMP paradigm is starting to look less and less appealing in my opinion.
     
  8. Sep 24, 2014 #7

    wolram

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    This author may well be a proponent of MOND but lets pick out one or two of his observations that can be disproved.
     
  9. Sep 24, 2014 #8
    Dark matter and aether theories: A recurring theme in science.

    In the 19th century the idea of an all pervasive medium to allow the light propagation in empty space: the aether was fully embraced by the scientific community( see Wikipedia article ), this idea was so accepted that very complicated and costly experiments were conducted to show direct evidence of its existence, for example the famous experiment of Michelson-Morley.

    But Einstein’s relativity theory of 1905 showed that this idea was really superfluous and indeed if you thing about the supposedly properties of this substance you will realize in hindsight that its properties were really fantastic, but that was an idea fully accepted.

    Now here we are in the 21th century and a new fantastic substance have been inserted in mainstream science: dark matter, this is just a fantastic substance, and its introduction have all the hallmarks that lead to the introduction of the aether idea: it is being introduced to “save” the current accepted theoretical framework from the inconvenient situation of the existence of observational facts that can not be explained without its introduction.

    We have found some “anomalies” in the space geometry and then we are “inferring” the existence of an all pervasive mysterious substance to explain it. What about thinking that our ideas about space-time are accurate up to a certain space-time scale, but when we are dealing with very large distances and time our approximations need to be re-calibrated?
     
  10. Sep 24, 2014 #9

    bapowell

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    Observations are not disproved. What falsifiable predictions does his theory make? Are they unique to MOND? If observations do not falsify MOND, does it enjoy the same degree of corroboration as dark matter? As a model, is MOND more or less complex than dark matter?
     
  11. Sep 24, 2014 #10

    Chronos

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    I was very entertained by Milgroms MOND explanations for the bullet cluster [http://www.astro.umd.edu/~ssm/mond/moti_bullet.html] [Broken] that required some 'unseen' [i.e., dark] matter. I don't believe I've heard the MOND explanation for BAO evidence of dark matter, but, expect it too would be entertaining.
     
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  12. Sep 24, 2014 #11

    Vanadium 50

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    See Skordis, Mota, Ferreira and Boehm "Large Scale Structure in Bekenstein's Theory of Relativistic Modified Newtonian Dynamics" where they point out that the TeVeS and LCDM cosmologies look the same with respect to structure. Each theory has one free parameter (mean density of dark matter and relative strength of the scalar term) and it turns out that the mathematical structure of the theory has the same mathematical form for these two effects. So of course the predictions are the same. Oh, and Skordis et al. published before the WMAP data.

    The Bullet Cluster is a problem for MOND and likely a problem for TeVeS as well. However, it's also a problem for LCDM. It's moving too fast - see Angus and McGaugh, MNRAS, 383, 417. There's also the "anti-bullet cluster", Abell 520. Here the mass coincides with the gas, not the galaxies.

    bapowell, one prediction of MOND is the Tully-Fisher relation. Another is stability of spiral disks in LSBGs - this falls out of MOND, but has to be put in each galaxy by hand in LCDM.

    That said, I don't believe MOND is telling us anything about gravity. It's probably telling us something about galactic formation and evolution, much as the Drude model told us something about metals. However, much of the argument against it is unscientific snark. On the merits, it's an ugly ugly model that does about as well - perhaps slightly better than - LCDM.
     
  13. Sep 24, 2014 #12

    Drakkith

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    What makes you think we aren't considering this? There are several working explanations attempting to reconcile observations with theory. Some involve modifying our current gravitational laws, while others theorize the existence of an unseen type of matter. None of these work perfectly yet, but new data is being collected all the time and work is steadily proceeding in figuring out this mystery.
     
  14. Sep 25, 2014 #13

    CKH

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    MOND may well be falsified as a theory of gravity, however it's telling us that the behavior of spiral galaxies can be predicted in detail based only on the distribution of baryonic (normal) matter. In fact irregularities in rotation curves are predicted by measuring irregularities in the distribution of normal matter.

    This discovery seriously challenges the theory of DM halos. Falsifying MOND in another context such as clusters or cosmology does not change the fact that spiral galaxies (across a few orders of magnitude in mass) can be empirically understood with MOND while ignoring both the amount and distribution of the theorized DM which is said to comprise 80% of galactic mass.
     
  15. Sep 25, 2014 #14

    Chronos

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    MOND-ophiliacs, like Kroupa, lack compelling explanations for too much observational evidence. DM, however clumsy, is at least as good as MOND in most cases, and the only one even viable in some cases - like BAO and the bullet cluster. Theory does not trump observational evidence.
     
  16. Sep 25, 2014 #15

    cristo

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    I don't think this is a problem anymore. There was a recent(ish) paper [Lage & Farra, ApJ 787 (2014) 144] looking at simulations of the bullet cluster. They found that there was "no need for unconventional physics or extreme infall velocities".
     
  17. Sep 26, 2014 #16

    CKH

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    You are demonstrating precisely what I stated:
    DM-ophilliacs falsify MOND (which may well be false as a theory of gravity) using your arguments. However, that does not change the striking predictability of rotation curves obtained through MOND's formula based only on baryonic matter distribution. MOND demonstrates that perturbations in rotation curves can be predicted directly from the observed (asymmetric) distribution of baryonic matter alone. That is a matter of observation, not theory.

    Falsifying MOND in other contexts is a ploy. I've seen it widely used by DM-ophilliacs to dodge this issue. Another strategy I've seen is cherry picking rare galaxies where MOND does seem to work in order refute MOND and ignore its more general success. DM theorist are going to have a very hard time indeed using DM halos to explain the success of this formula in rotation curves and in the Tully-Fisher relation. In essence they will have to get DM to closely conspire with baryonic matter.

    Kroupa may have drunk too deeply of the demon rum MOND. But, his observation-based arguments that contradict the domination of non-baryonic DM halos in galaxies are sound (IMO), but ignored by the mainstream often with the excuse that MOND is not a perfect theory of gravity. That is not Kroupa's main point, nor is it Stacy McGaugh's main point which he has repeatedly stated in papers.


    .
     
  18. Sep 26, 2014 #17

    cristo

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    This isn't really a matter of 'predictability' - MOND was invented purely to match the galaxy rotation curves that were observed. If MOND were written down before these observations and *then* predicted the observed rotation curves then that would be something different (you know, like DM predicts the cosmic web as observed with SDSS, or predicts the CMB anisotropies).
     
  19. Sep 27, 2014 #18

    Chronos

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    No one ever said MOND is not a fit. That's why it gained popularity in the first place. Observational evidence over the last half century has, however, increasingly favored DM. MOND simply doesn't work in too many cases to be taken seriously.
     
  20. Sep 27, 2014 #19
    Switching the words MOND an DM in this paragraph makes no difference.
     
  21. Sep 27, 2014 #20

    Chronos

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    Please cite examples where MOND works and DM does not. I've already cited at least two cases where DM works and MOND does not. While there have, at least, been some attempts to shoe horn MOND into the Bullet cluster, I've not seen an account for how MOND fits into BAO, or primordial nucleosynthesis. DM, however, does a sterling job on both counts - e.g., http://www.astro.ucla.edu/~wright/BAO-cosmology.html,
     
    Last edited: Sep 27, 2014
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