Is it?
http://arxiv.org/abs/astro-ph/0702146 " The Bullet Cluster 1E0657-558
evidence shows Modified Gravity in the absence of Dark Matter,
J. R. Brownstein, J. W. Moffat, Mon.Not.Roy.Astron.Soc. 382 (2007) 29-47"
http://www.blackwell-synergy.com/do...2966.2007.12403.x?cookieSet=1&journalCode=mnr "The collision velocity of the bullet cluster in conventional and modified dynamics, G. W. Angus and S. S. McGaugh, SUPA, School of Physics and Astronomy, Monthly Notices of the Royal Astronomical Society, Volume 383 Issue 2 Page 417-423, January 2008 ... snip ... "We consider the orbit of the bullet cluster 1E 0657?56 in both cold dark matter (CDM) and Modified Newtonian Dynamics (MOND) using accurate mass models appropriate to each case in order to ascertain the maximum plausible collision velocity.
Impact velocities consistent with the shock velocity (~4700 km s^^-1) occur naturally in MOND. CDM can generate collision velocities of at most ~3800 km s^^-1, and is only consistent with the data, provided that the shock velocity has been substantially enhanced by hydrodynamical effects."
http://arxiv.org/abs/0706.1279 "The wedding of modified dynamics and non-exotic dark matter in galaxy clusters, B. FAMAEY, G. W. ANGUS, G. GENTILE, H. Y. SHAN, H. S. ZHAO, 2007 ... snip ... We summarize the status of Modified Newtonian Dynamics (MOND) in galaxy clusters. The observed acceleration is typically larger than the acceleration threshold of MOND in the central regions, implying that some dark matter is necessary to explain the mass discrepancy there.
A plausible resolution of this issue is that the unseen mass in MOND is in the form of ordinary neutrinos with masses just below the experimentally detectable limit. In particular, we show that the lensing mass reconstructions of the rich clusters 1E0657-56 (the bullet cluster) and Cl0024+17 (the ring) do not pose a new challenge to this scenario."
http://allesoversterrenkunde.nl/con...efault&uid=default&ID=721&ww=1&view_records=1 "At a distance of 2.4 billion light years in the constellation of Orion, Abell 520 also consists of two colliding clusters. However, according to a team led by Andisheh Mahdavi and Henk Hoekstra of the University of Victoria, British Columbia,
the dark matter in Abell 520 doesn’t appear to be tied to the galaxies. Instead, the lensing observations – carried out with the 3.6-meter Canada-France-Hawaii Telescope on Mauna Kea in Hawaii – indicate that huge amounts of dark matter are concentrated in the core of the colliding pair, where most of the hot gas is found but few galaxies are seen. As the team writes in their October 20 Astrophysical Journal paper,
this dissociation between dark matter and galaxies "cannot be easily explained within the current…dark matter paradigm." "It’s a remarkable result," says cosmologist David Spergel of Princeton University. "A conservative explanation would be that not all dark matter concentrations are efficient in the formation of stars and galaxies.
The alternative is that dark matter interacts with itself in response to an unknown, fifth force of Nature, which only involves dark matter." Under the influence of such an attractive force, two clouds of dark matter could no longer pass through each other unimpeded but would eventually be dragged like the hot cluster gas, ending up in the common center of gravity of the colliding clusters.
Robert Sanders of the University of Groningen in the Netherlands says there’s a third solution to the problem: modified Newtonian dynamics (MOND). Invented in the early 1980’s by Mordehai Milgrom of the Weizman Institute in Rehovot, Israel, MOND proposes that the observed signatures of dark matter really result from a different behavior of the force of gravity. In particular gravity in low-acceleration regions (like the outskirts of galaxies) would weaken linearly with distance, not exponentially.
Even in a MOND universe, some dark matter has to exist, but it could consist of "normal" particles, such as neutrinos, instead of mysterious, undetected stuff. Sanders says he and Milgrom are writing a paper on how MOND can accommodate the cluster observations. "These new results—if they are real—could be an outstanding success for MOND," he says."
http://arxiv.org/pdf/astro-ph/0611777 "An Introduction to Gravitational Lensing in TeVeS, HongSheng Zhao, 2006, Bekenstein’s (2004) TeVeS theory has added an interesting twist to the search for dark matter and dark energy, modifying the landscape of gravity-related astronomy day by day.
Built bottom-up rather than top-down as most gravity theories, TeVeS-like theories are healthily rooted on empirical facts, hence immediately passing sanity checks on galaxy rotation curves, solar system constraints, even bullet cluster of galaxies and cosmology with the help of 2eV neutrinos. ... snip ... TeVeS is an exception. It holds the promise of explaining both dark matter and cosmological constant by relaxing the SEP (strong equivalence principle) only in untested weak gravity envionments like in galaxies, but respecting the SEP to high accuracy in the solar system. ... snip ...
Angus et al. (2006) found that the lensing peaks of the Bullet Cluster could be explained by adding neutrinos in a TeVeS-like modified gravity ... snip ... TeVeS is found to be • OK with solar system (Bekenstein & Maguijo 2006) • OK with Milky Way and Bulge Microlensing (no cusp problem, Famaey & Binney 2006) •
Excellent description of spiral rotation curves (Mc-Gaugh 2005, Famaey et al. 2006) • OK with elliptical galaxies lenses (Zhao, Bacon, Taylor, Horne 2006) • OK with galaxy clusters if with neutrinos (Angus, Shan, Zhao, Famaey, 2006), • TeVeS universe can accelerate (Zhao 2006, astro-ph/0610056) • Structures and CMB can form from linear perturbations (Dodelson & Liguori 2006 ... snip ... • TeVeS is not grossly inconsistent with observations of lensing apart from a few outliers associated with galaxy clusters where massive neutrinos would contribute to the deflection of the light, • CMB anisotropy are predictable (Skordis et al. 2005), • structure formation in non-linear potential can in principle be followed by N-body codes (Ciotti et al. 2006)"
http://arxiv.org/abs/0706.3048 " A Dark Core in Abell 520, A. Mahdavi, H. Hoekstra, A. Babul, D. Balam, P. Capak, 2007, The rich cluster Abell 520 (z=0.201) exhibits truly extreme and puzzling multi-wavelength characteristics. It may best be described as a "cosmic train wreck." ... snip ...
Although a displacement between the X-ray gas and the galaxy/dark matter distributions may be expected in a merger, a mass peak without galaxies cannot be easily explained within the current collisionless dark matter paradigm."
http://209.85.173.104/search?q=cach..."+"not+dark+matter"&hl=en&ct=clnk&cd=13&gl=us , arxiv.org/pdf/astro-ph/0610298, "A New Force in the Dark Sector?, Glennys R. Farrar and Rachel A. Rosen, Center for Cosmology and Particle Physics, Department of Physics, New York University, 2007, We study the kinematics of dark matter using the massive cluster of galaxies 1E0657-56. ... snip ...
If the discrepancy we find here between predicted and observed dynamics of the bullet subcluster is substantiated by refined observations and analysis, and confirmed in other systems, it would imply the existence of a long-range, non-gravitational force within the dark sector."
Oh no ... now it's not just dark matter and dark energy, but dark forces! 
http://space.newscientist.com/article/dn13280-galaxy-without-dark-matter-puzzles-astronomers.html "
Galaxy without dark matter puzzles astronomers, February 2008 ... snip ... According to their combined mathematical model, ordinary luminous stars and gas can indeed account for all the mass in NGC 4736. ... snip ... "If this paper is correct, then this galaxy contains very little or no dark matter," says astrophysicist Jürg Diemand of the University of California, Santa Cruz, US, who is not a member of the team. "That is surprising." ... snip ... "
It is unclear how one would form a galaxy without a dark halo, or how one could remove the halo without destroying the galaxy," says Diemand. "A galaxy without dark matter really does not fit into our current understanding of cosmology and galaxy formation." Nor can galaxies with declining rotation curves be easily explained by MOND, says McGaugh. So for now, it seems that some of our missing mass is missing."
And I've already mentioned what plasma cosmologists have to say about the Bullet Cluster. But here it is again. The dark matter explanation is based on a calculation full of assumptions. For one, it assumes that redshift always equates to distance. But mainstream astrophysicists seem to have no way of explaining the extremely large number of extremely unlikely "coincidences" with respect to the location of high red shift objects and low red shift objects ... so they just ignore them. Likewise, they can't explain "coincidences" with respect ot the relative position of objects and axes of rotation in the Local Group (of which the Bullet Cluster is a part)? The dark matter explanation also assumes the clusters are colliding.
Halton Arp, on the other hand, says quasars are not necessarily distant objects but may, in many cases, be relatively nearby objects created and ejected from older galaxies according to the equations in Narlikar's variable mass cosmology. He says BL Lac objects evolve from quasars. He says that instead of colliding, the cluster is actually in the process of forming from a BL Lac object. Arp says the Bullet Cluster is exhibiting the expected features of such an event. It has the redshift typical of BL Lac objects (z = 0.3). That redshift is one of the quantized redshift states in the theory he espouses. BL Lac objects emit x-rays. And Arp observes that other galaxy clusters do too. A collision isn't necessary to explain the X-rays. And as far as lensing is concerned, Arp says arcs are a natural phenomenon in clusters of galaxies. In the mainstream theory, high redshifts in these arcs is a must if they are to be gravitationally lensed distant background objects. However, Arp has shown that nearby Abell galaxy clusters also exhibit arcs and have such low mass that it is impossible for them to act as a gravitational lens. Plus, some of the arcs are radial ... not tangential. Furthermore, the Bullet Cluster fits neatly into his explanation of the Local Group and the relationship of its objects to one another. All without the need for dark matter. Arp's is true observationally based cosmology ... not one relying on gnomes and ignoring inconvenient observations.
Frankly, enigma, I think most readers would be better served investigating each of the links at
http://www.thunderbolts.info/tpod/00subjectx.htm than meekly accepting the gnomes that you and the rest of the dark matteroligists have offered to explain away the observations. The universe they posit is far more interesting, beautiful and compelling than yours.
