Another reaction to the Dark Matter Debate

8 December 2010 by Pavel Kroupa, posted in General

During the past months there was quite some activity in the German media on the issue of cosmology and the existence of dark matter. Starting with our German paper "The standard cosmological model being tested" (German: Das kosmologische Standardmodell auf dem Pruefstand"), which appeared in the August issue of  Spektrum der Wissenschaft,  some of the leading experts are beginning to re-position themselves, it seems.

In a major German article about himself "Perhaps we are seeking a phantom" (in German: "Vielleicht laufen wir einem Phantom nach"), which appeared in the October issue of Spektrum der Wissenschaft, Prof. Dr. Volker Springel from Heidelberg states that it is quite possible ("Gut möglich") that the current standard model of cosmology is false.

Also, in an interview with the German TV station 3sat/scobel on "MOND - Modified Newtoian Dynamics: A new theory to close gaps" (translated from German: "MOND - Modifizierte Newtonsche Dynamik: Eine neue Theorie, die Lücken schließen soll", on Nov. 25th), Prof. Dr. Matthias Steinmetz from Potsdam also states that, on the long term, we will need a new theory.

Dr. Frederic V. Hessman from the University of Göttingen, upon seeing this blog on The Dark Matter Crisis, wrote a few very interesting comments, some of which we can post here:

 

Dec. 2nd, 2010:

Today is our chance to participate in the "Dark Matter Awareness Week", for which I volunteered to present the standard talk (after all, one is allowed to add one's own comments). Fortunately, I found out about your blog, the "Great Debate" and the DM TV show in time to help put everything in perspective for the audience (but too late to have been in Bonn in person for the debatte - too bad!).

You mention in your blog that Simon presented the standard arguments showing that LambdaCDM is so successful at explaining large-scale structure. I hardly consider the fact that LambdaCDM is utterly unable to explain the lack of 2-point correlations in the WMAP fine-structure as a sign of strength: both the predicted amplitude and the form are different from the observations (Copi et al. 2009, MNRAS 399, 295) and at small scales the amplitude has the wrong sign. Getting the power-spectrum right is not nearly as sensitive a test (TeVeS and dozens of other theories can get that right): I could probably send you a phase-scrambled picture of a cat and a garbage truck with the same power-spectrum but wouldn't want to say that cats are garbage trucks. There are, of course, many other weak points that you probably included
in your talk during the debate (the podcast isn't yet available, I believe), but I don't understand why people think rough agreement is such a strong argument. As soon as real structure forms, things get more complicated, but LambdaCDM can't even get this most basic test right.

And also, after PK asked him whether his statements may be placed on The Dark Matter Crisis (which e affirmed):

I've been studying the DM literature - from the very beginning - intensely for the last 5 years or so (initially as a relief from my technical MONET telescope work - programming controllers can be pretty boring) and am startled by the sociological effects and un-explored loose ends (Sander's book just scratches the surface).

We should suggest that the Heidelberg AG Tagung ("Surveys and Simulations - the Real and the Virtual Universe") include a day of "Great Debates". We can also organize a splinter meeting, which I would call "The Real and the Virtual Universe - The Importance of Knowing the Difference between the Two".

And further more in a third e-mail on the same day after viewing the debate on podcast:

I didn't hear any surprises from Simon. You should have complained at least about the following points:

- At the very beginning, he says that DM can't be "normal matter". This is the standard line but the line of evidence, in fact, has lots of holes which are largely ignored. E.g. no one has shown that the Pfenniger et al. 1994 and Pfenniger & Combes 1994 model of cold H_2 clouds is wrong (and PLEASE don't try to invoke Toomre's Q-factor - that's the "cows are perfect spheres" argument -see Revaz et al. 2009).

- Everyone always shows the "internal linear combination" (ILC) map from WMAP, even though WMAP admits this cannot possibly be the right map: one can't correct for diverse CMB foregrounds by simply linearly combining one's data maps, the spectra of the foreground sources (much less their full identification) is simply too complex.

- The WMAP power spectrum shown cleverly left out the low-l points, where LambdaCDM totally fails. He didn't want to talk about the alignment of the low-order modes with the ecliptic plane for sure.

- Simon praises the "30-sigma measurements" of the cosmological parameters. These are not measurements, these are model parameter fits. I can fit the WMAP powerspectrum with another 8-parameter model (a polynomial) and probably get 15-sigma fits but who cares? The one biggest problem with the CCM (=Concordance Cosmological Model) is that people now confuse models with data, reality with theory. The cosmic "acceleration" isn't measured using Type Ia SN, it's the result of a (primitive) cosmological model fit to the real data (redshift and distance) so that a different model would result in a different "measurement". Measurements are not interpretations except in a fundamentally different philosophical sense, not really relevant to this question.

- Bullet Cluster et al. : Simon admits that there is only a factor or ~5 left to explain cluster dynamics (using galaxies, intracluster gas alone). Note that the Bullet Cluster analysis did not actually include the CDM halos of the galaxies in their tabulation! They would fly apart if the CDM halos were gone (or at least be very different beasts). Simon once published a paper saying that sedimentation of galaxies rules out DM in galaxies alone, but clusters are too young and there is probably too much mass in gas and neutrinos for this argument to be relevant.

On your talk:

- Even you said that the "visible matter is declining" in the outer parts of spiral galaxies: this is the typical optical bias, since lots of galaxies show an increase in the amount of HI in those regions where the stars are fading.

- I love your quotes about CCM sociology (is your talk available)!

The talk "Cold/Warm Dark Matter is ruled out" is avalable here. Simon White's talk can be downloaded from his website.

The reader might enjoy this link: The Blind Men and the Garden

 

by Pavel Kroupa and Marcel Pawlowski (08.12.2010): "Another reaction to the Dark Matter Debate" in "The Dark Matter Crisis - the rise and fall of a cosmological hypothesis" on SciLogs. See the overview of topics in  The Dark Matter Crisis.


One Response to “Another reaction to the Dark Matter Debate”

  1. Christopher Lee Reply | Permalink

    Dark Matter is unproven:

    The 'Big Bang' took time; at first it was more explosive, hence the farther away an object in the universe is from us, the higher it's acceleration, but as the Big Bang weakened, the subsequent velocities of objects closer to us were slower. If Space does not expand, but simply is, then there is no space-fabric to eventually tear apart. Dark matter remains theoretical. There are alternative Theories to explain varying rates of acceleration, but they are not being studied as thoroughly because they are not as sexy as exotic 'Dark Matter'

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