Dark Matter: A debate – afterwards while on safari

27 November 2010 by Pavel Kroupa, posted in General

Fleeing  the  European continent to go back to Australia on safari for some satellite-galaxy hunting in Canberra with my friend Dr. Helmut Jerjen, I had a little time on my Quantas  flight and in Singapore and Perth to reflect upon the debate, and I note the following:

Simon White gave an excellent presentation of the impressive agreement of standard cosmology, i.e. the LCDM model, showing some of the available data on large scales and the cosmic background radiation map (his slides are available on his website).  Somebody in the audience during or after the debate was over, mentioned an interesting observation  (unfortunately I do not recall who this was):

In order to get Einstein's theory of general relativity to fit the data one needs to postulate unknown physics, namely inflation, dark  matter, dark energy.

(This I had indeed stressed in my presentation, therewith putting the LCDM success story implied by Simon on a different if not dis-satisfying footing.)

But, the unknown person continued:

Can one then, after introducing these unknowns to make the theory fit, argue that the LCDM model is correct because it fits the data? Is this not a circular argument?

Perhaps the LCDM model finds support in that various different lines of argument lead to similar values for the numbers which define the precise model. But,  Mr. Unknown has raised a point central to how science advances:

Rather than demonstrating how excellently LCDM does on large scales, a cleaner argument that the LCDM model describes physical reality is as follows:

Accept that the LCDM model is adjusted to fit the data on large scales. Once it is fixed, it can be used to make predictions in a different regime. This different regime is on scales smaller than 8 Mpc, where the model makes very precise predictions how the cold dark matter must be distributed for it to be a valid description of nature and where we have truly exquisite observational data.  This distribution is seen in the form of galaxies and how they cluster. And this is where the observational data, unfortunately, are in highly significant conflict with the model such that they exclude the LCDM model. This holds true despite the often invoked uncertainties and complexities in dealing with the physics of normal matter (for example, observations clearly tell us that galaxies are simple objects obeying simple scaling laws such that true physics describing their structure must be simple as stressed by Disney et la., 2008, Nature).

For example, in the debate after the two presentations, Simon White attempted to address the small scale problem by showing an excellent fit of the LCDM model to one of our satellite galaxies, namely Fornax. Fornax is far away, at 140 kpc, so far in fact, that it must be in dynamical equilibrium.  Dynamical equilibrium means that the stars are orbiting within the galaxy such that the whole galaxy is not changing its appearance. Thus, when a star moves to the right, another one moves to the left such that they compensate each other statistically.  So getting a good description of it with the LCDM model would indeed, as Simon White stresses, be a great success.

However, this is wrong, and it was surprising that Simon White did not note this. Indeed it is also surprising that I did not jump at this logical inconsistency, perhaps because it was such a self-evident failure that I dared not point this out in fear of causing an unpleasant situation. The LCDM fit is unphysical because Fornax has a complex inner structure: As is evident on slide 49 of my presentation, Fornax has a twisted and dislocated inner structure, such that it simply cannot be in dynamical equilibrium. Dynamical equilibrium is, however, one of the fundamentally important assumptions that go into modeling the data via the LCDM model. In the LCDM model, any complex structure would disappear on a short time-scale of about a hundred million years, as I indeed had put much emphasis on during my presentation. That is, the appearance of the little galaxy would be changing significantly on this astronomically short time-scale. Simon White must have missed this point, or simply ignored it.

Unfortunately, Simon did not address all the other failures I had put up, nor did I return to them during the debate - well, they had been stated in my presentation already. But, given the astrophysical literature, it is evident that there are no remedies to save the LCDM model, given its current ingredients.

Now, one attempt to advance from here is to add an additional  Dark Unknown, a Dark Force which acts only between cold dark matter particles, as discussed by Peebles & Nusser (2010, Nature), or an additional Dark Force which acts only between dark matter and normal matter, as discussed by  Kroupa et al. (2010, Astron. & Astrophys). These speculative forces, about which we know absolutely nothing, are none of the other three already known forces (electromagnetic, weak and strong) nor Einsteinian gravity.

Therefore, the failure of LCDM on scales smaller than 8 Mpc is due to it being wrong. Note here that it is wrong even if one adds the above dark forces, since with these forces the LCDM model becomes a different one with different properties on large scales. This is where MOND or another alternative (e.g. MOG) comes in. MOND is not a dark force, but merely a simple modification of either gravity or inertial mass, depending on its interpretation.

It is remarkable how brilliantly MOND has been performing since its conception in 1983 by Mordehai Milgrom. In fact, in his most recent paper, Milgrom ("MD or DM? Modified dynamics at low accelerations vs dark matter", 2010, Proceedings of Science) writes in his abstract:

Some of the complaints leveled at MOND are: (i) "MOND was designed to fit rotation curves; so no wonder it is so successful in predicting them". This is both incorrect and quibbling: The first ever MOND rotation curve analysis was undertaken more then four years after the advent of MOND. And, even if MOND, epitomized by a very simple formula, could have been designed to predict hundreds of rotation curves, it would still be a great achievement. (ii) "MOND outperforms CDM only on small, galactic scales, where formation physics is anyhow very messy, but falls behind in accounting for `simpler', large-scale phenomena". Quite contrarily, all the salient MOND predictions on galactic scales follow as unavoidable, simple, and immediate corollaries of the theory - independent of any messy formation scenario - just as Kepler's laws, obeyed by all planetary systems, follow from an underlying theory, not from complex formation scenarios. To think, as dark-matter advocates say they do, that the universal MOND regularities exhibited by galaxies will one day be shown to somehow follow from complex formation processes, is, to my mind, a delusion. What is left for MOND to explain on large scales is a little in comparison, and has to await a full fledged relativistic MOND theory. (iii) "The `bullet cluster' shows that MOND still requires some matter that is dark". Yes, it has long been known that MOND does not fully remove the mass discrepancy in the cores of galaxy clusters. Some additional still-dark matter is needed. But this need not be THE "dark matter"; a small amount of the still-missing baryons, in some dark form (dead stars? cold gas clouds?), or perhaps (sterile?) neutrinos, could fit the bill.

Finally it serves to be useful to note the following statement from the paper by Peebles & Nusser ("Nearby galaxies as pointers to a better theory of cosmic evolution", 2010, Nature, p.568):

The variety of problems we have considered in the interpretation of the present baseline motivates serious consideration of adjustments of the fundamental theory.

Prof. Jim Peebles at Princeton University is one of the leading cosmologists who had actively worked in developing the LCDM model.

Concluding:

The 18th November was very special. Not only because we had such a debate in Germany, which is otherwise overall well on-track with the LCDM model with most major professorships having been filled with its adherents. More importanly, the generally well educated public in Germany is interested, and for me having so many cameras around was a new experience which clearly had an effect on how the scientific debate proceeded. I would like to sincerely thank Prof. Gerhardt Hensler from Vienna, Prof. Robert Sanders from Groningen and Prof. Tom Shanks from Durham for following my call to join-in with the debate. Prof. Hensler is an expert on star-formation and gas-dynamical processes in galaxies. Prof. Sanders is an expert on gravitational dynamics and the astrophyics of galaxies. Prof. Shanks is an expert on observtional cosmology andextragalactic astronomy. The presence at the debate of my long-term supporting colleague Prof. Klaas S. de Boer from Bonn was also central. Their expertise was essential during the debate, and their active participation also demonstrates that here are a substanial number of  scientists who see major problems with the LCDM model, such that, with adequate funding support, significant progress in cosmology can be hoped for. 

by Pavel Kroupa and Marcel Pawlowski (27.11.2010): "Dark Matter: a debate - afterwards  while on safari" in "The Dark Matter Crisis - the rise and fall of a cosmological hypothesis" on SciLogs. Written in Perth. See the overview of topics in  The Dark Matter Crisis.


6 Responses to “Dark Matter: A debate – afterwards while on safari”

  1. Jin He Reply | Permalink

    Arxiv rejects me even at the General Physics category:

    So, I go to Vixra:
    http://vixra.org/abs/1011.0057

    Arxiv moderators' email:

    arXiv:submit/0149438 Removed
    "Don Beyer [www-admin]"

    Your submission has been removed upon a notice from our moderators, who determined it inappropriate for arXiv. Please send to a conventional journal instead for the requisite feedback.

    If you disagree with this determination, please do not resubmit the submission to any archive until you first explain the reason to moderation@arxiv.org and receive a positive response.

    Please direct all questions and concerns regarding moderation to the moderation@arxiv.org address. More information about our moderation policies can be found at:

    http://arxiv.org/help/moderation

    --
    arXiv admin

    The Arxiv gets money from taxpayers but doing something blocking truth!!

    However, my paper can be verified by high shcool students!!

    3 Do-It-Yourself Notes for Layman

    Rational structure is a simple concept and it admits a complete solution taking the form of algebraic equation, i.e., the instinct equation (17). Every layman can try a galaxy image to convince himself or herself that rational structure is true.

  2. Peter Fred Reply | Permalink

    It's a flat rotation curves crisis, not a dark matter crisis

    Why bother trying to show that the dark matter idea does not work. It is just another lame idea that usually comes up when there is crisis in physics or astronomy. The MOND idea is just about as lame. When a venerated theory is threatened by observations, it is not time to think of some superficial idea that will make everybody feel good about all those years they spent studying a theory that may prove useless as the Ptolemaic theory with those intricate assortment of epicycles and equants.

    The Genesis account of creation could not adequately deal with the origin and variety of the species problem that surfaced in the 1800's. Darwin came up with the idea of natural selection. After spending 20 years of fleshing it out, this idea eventually proved useful in dealing with the situation.

    The motion of the planets were not easily comprehended by the venerated idea of geocentrism. The amateur, Copernicus, distanced himself from the followers of Aristotle and Ptolemy and came up with the simple and plausible idea of heliocentrism. When he published after 30 years trying to make the idea work, this idea eventually took was accepted.

    The failure to find the aether forced upon the world the difficult-to- comprehend idea of time dilation. This idea, like heliocentrism and natural selection, forced the theorists to abandon the vary foundations upon which their old theory was based and which they were recognized and funded authorities on.

    If these three revolutionary ideas are examined, it can be seen that they are almost obvious and almost no-brainers. Einstein said around 1925 "Subtle is the lord, malicious he is not". True to this statement, there seems to be a simple, almost-obvious idea that may solve the problem of flat rotation curves and the problem of cosmic acceleration. Simply put idea is:

    "It is not with their mass that stars accomplish gravitational attraction. Rather, it with their light leaving their mass that they accomplish gravitational attraction."

    Because of the simplicity and plausibility of this idea, I have spent 30 trying to flesh it out. To see my paper and five experiments click on my name above. There I present four experiments where a test mass is placed above a 1000 W heat source and below a heat sink composed of ice. After the heat source heats the test masses for 4-6 minutes, the observed increase of weight of the test masses turns out to be 1.9%, 8.9%, 9.6% and 16% respectively! These experiments represent a "serious anomaly" and someone should try to replicate them as was done with the supernova results which then forced most of us to accept the unexpected idea of cosmic acceleration. Instead, what I will get from those who look at my paper is Einsteinian "thought experiments" as why the observed weight increases of the test masses could not be right. Show me experiments that indicate that they are not right.

    The astronomers and cosmologists that have devoted their careers to the crisis caused by the flat rotation curves and cosmic acceleration have developed considerable skills and observational capacity pursuing this endeavor. But why employ these skills and techniques trying to disprove a lame, poorly-conceived idea. These skill should devoted to an idea where a little thinking has gone into its conception and a number of years gone into its theoretical development.

    Incidentally, see the graph in Figure 6 in my paper which shows the close coincidence in time between the "dimming of the universe" and the onset of cosmic acceleration. My idea of "attractive radiation" was only conceived to deal with the flat rotation curves. It was never conceived to deal with cosmic acceleration which came about in 1998. Can MOND provide an explanation for cosmic acceleration? Can dark matter provide and explanation for it?

  3. Pavel Kroupa Reply | Permalink

    comment to Jin He

    Working in the field of modern astrophysics, as in all other natural sciences, requires many years of hard training and usually also involves set-backs such as not having one's own paper accepted for publication because its content is not deemed, by the more experienced researchers, as being appropriate or as adding sufficiently new science. This needs to be accepted and also respected, and the author needs to learn from such experience. It is indeed sometimes a fine balance between deciding which written-up work is deemed appropriate for a journal, and sometimes excellent research gets rejected because it does not fit into the current paradigm. These are the tragic cases, but usually such work can get published by (1) respecting the referee's comments and (2) making an effort to address the comments and (3) trying to argue better, asking for other referees if necessary and pointing out the issues to the editor. And if all fails, then there are other journals to try. Considering the written-up work by Jin He, one needs to first of all ask the question what feedback the local colleagues in the same institute would have. Jin He might then be able understand better the issues at hand, and perhaps improve the manuscript to be more acceptable in the scientific arena. I do not have the time to go into depth, but the beginning of the abstract for example is not a way a scientific research paper is written, so this would already be a start. In summary: the rejection of Jin He's manuscript does not necessarily fall into the same category as the problems we are discussing concerning publication of research papers that provide evidence against current consent thinking.

  4. Peter Fred Reply | Permalink

    Is gravity mediated by thermodynamics or heat transfer

    This idea of Verlinde that gravity is a consequence of the laws of thermodynamics is all the rage now. His paper is now one of the top most cited papers with 127 citations according to Spires.

    If dark matter is a failed idea, how are we going to account for the flat rotation curves. Do you think Verlinde's complicated ideas about thermodynamics is going to do it?

    Light bending puts extra light at the edges of galaxies making the light in these regions tend to fall off as 1/r rather than as 1/r^2. If light is gravitationally attractive as my five experiments demonstrate, then we have a simple straightforward way of accounting for the flat rotation curves.

    Our highly-educated, esteemed scientist have every right to ignore my five experiments and my heat-based gravity theory because everyone knows through the radiation pressure studies that radiation is repulsive and not attractive. It could not be attractive could it? If it were what the empirical, ubiquitous Tully-Fisher relation (L=k*V^4)is all about.
    http://vixra.org/abs/0907.0018

  5. anand srivastava Reply | Permalink

    Kepler's laws, obeyed by all planetary systems, follow from an underlying theory, not from complex formation scenarios.

    This is really the crux. I don't care about the MOND as a theory. But as an empirical formula it rocks. I stopped considering Newtonian gravity to be viable, when I learnt about it in 2002.

    There has to be an underlying reason for it. There is no way Dark Matter can follow the bright matter to bring out MOND.

    I have been looking at different approaches which provide an explanation for it. First it was Mannheim's Conformal Gravity. It looked beautiful, but it broke down on Light deflection.

    Not being a physicist I could never understand MOG. It does not look very natural to me. It could be the papers don't explain it very well in layman terms.

    Nothing since then had come out which looked like a possibility. Now people are deriving MOND from Verlinde's theory, using Hubble's constant. That makes it very interesting. Some have even attempted to explain Pioneer's anomaly.

    I believe that the theory's basic premise should be as simple to understand as Relativity was. Mannheim's was the same, he just used a different tensor, nothing much different.

    Verlinde's theory is very simple on a conceptual basis, and there doesn't seem anything wrong with it. Entropy could be the most basic of all elements in our universe. Everything may come out of it.

  6. David Brown Reply | Permalink

    Has Professor Milgrom underestimated the M-theorists?

    According to Professor Milgrom, "What is left for MOND to explain on a large scale is a little in comparison, and has to await a full fledged relativistic MOND theory." I claim that the Rañada-Milgrom effect shall soon revolutionize cosmology, but perhaps all my thinking on cosmology is incorrect. Let us entertain 4 questions: Is MOND a corollary of some form of M-theory? Is it reasonable to start from scratch and try to replace M-theory? Has Professor Milgrom underestimated the ideas of such M-theorists as Witten, Seiberg, and Maldacena — are those three at the Institute of Advanced Study by mistaken appointments? Has Professor Milgrom "shot himself in the foot" by not linking his theory to M-theory?

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