chandra - dark matter

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by rush</i>
<br />How modified theory of gravities are taking such observations into account?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">The study makes a very basic (and common) confusion between gravitational potential effects (such as lensing) and gravitational force effects (such as orbital motion). "Dark matter" is indicated by the behavior of the force law, not by potential distribution. In MM, for example, many lensing effects are refraction in quasar jets and not gravitational in nature at all.

Specifically, the plasma in this pair of clusters would be expected to produce a fairly constant gravitational potential, which yields a zero gravitational force. So it cannot produce much if any lensing because of lack of variation. Galaxies, by contrast, have potential gradients that indicate gravitational forces acting in the usual way, explainable by MOND, MM, and most "dark matter" alternatives. They behave as in any outher single cluster.

The fact that the galaxies produce lensing and the plasma does not is not significant, and the claims in the paper are false. In any fair refereeing process, this paper would never have been published. -|Tom|-

Tom, do you know any recent peer-reviewed paper that confronts the claims in that paper?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by rush</i>
<br />do you know any recent peer-reviewed paper that confronts the claims in that paper?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">No. But is would take a while for one to appear. And prefessional courtesy implies that a wrong paper will be ignored rather than corrected, provided it is doing no harm. (Few scientists are interested in cleaning up the journals. It would be a thankless and never-ending task.) And from a BB perspective, that paper is doing no harm. -|Tom|-

(Phys.org) -- Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

from: phys.org/news/2012-04-dark-theories-mysterious-lack-sun.html

I read that article the other day. It's amazing how much people will do to discover non-existing stuff. I guess there is no way to change this kind of research without overturning current beliefs somehow.