Fred Cooperstock and Steven Tieu of Northeastern University and the University of Victoria respectively have a paper on arXiv which apparently shows that using general relativity with corrections for non-linear effects and other such things I do not understand results in a VERY good fit for the explanation of why galaxies rotate the way they do and thus removes any need for non-baryonic "dark matter" haloes around the galaxy! If it is a valid result and is verified it will be a really major discovery. Even CERN is now carrying a blurb about the paper.

Article at space.com too:

http://www.space.com/scienceastronomy/0510...ark_matter.html

WOW! If confirmed is a real revolution for cosmology and astrophysics...
However, "the new idea does not yet explain how large clusters of galaxies bind together", Cooperstock says.
So the largest scale dark matter evidence seems confirmed.

hmmmmm....

interesting.

This would ultimately explain dark matter as being just a kind of "perspective effect" and not actual mass.


But this goes against other searches which provided density maps of galaxy clusters (using optical distortion of the background galaxies). These searches indicate a heavy content in dark matter, for the overal cluster and for the individual galaxies too.

What I think is that little by little the parts of the puzzle will fall in place. Very cold cosmologic neutrinos may fill a part of the gap. Burned out stars another. Relativistic correction another. Until we find a clear bilan of the galaxies mass.

Also if the density of the universe is lesser than expected, this could lead to abandon the idea of a "dark energy" which drives the today inflation of the universe.

By the way if somebody could explain me what means the expression "dark energy"? Energy has no color, as far as I know.

'Dark energy' are a term sometime used for the cosmological constant, one idea proposed by Albert Einstein and which have had a renaissance in recent years. The idea of the cosmological constant had a comeback after astronomers measured the light from novas used as 'standard candles' to get distance and the velocity (redshift) for the galaxies they were part of.
The study (actually more than one) yielded the result that the galaxies in the universe appeared to increase their speed as the universe continues to expand, and one theory are that this was caused by 'dark energy' the term meaning that its unseen.

The word on the street says that:
The theory fails when modelling the galactic rotation speeds of dwarf galaxies.
The theory fails to agree with observations near the galactic centre.
The theory derives the galactic density from the rotation curves- they should be doing it the other way around.
The small number of bright galaxies they chose have high inclination angles.
The theory fails to address why galaxy clusters are held together.

Singular disk of matter in the Cooperstock and Tieu galaxy model
Authors: Mikolaj Korzynski

Recently a new model of galactic gravitational field, based on ordinary General Relativity, has been proposed by Cooperstock and Tieu in which no exotic dark matter is needed to fit the observed rotation curve to a reasonable ordinary matter distribution. We argue that in this model the gravitational field is generated not only by the galaxy matter, but by a thin, singular disk as well.
The model should therefore be considered unphysical.

http://arxiv.org/PS_cache/astro-ph/pdf/0508/0508377.pdf (PDF)

If there is a "thin disk" which bears some mass, it is still "dark matter" in a form or another. The fact it is two-dimentionnal in place of three dimentionnal only adds new mystery, as nothing known can explain a two-dimetionnal mass.