mainframe
A recent survey of our part of the Milky Way failed to find any of the elusive dark matter posited to account for a presumed 83% matter shortfall needed to explain why galaxies don’t fly apart.

In the absence of dark matter it would seem that a productive avenue for explanation might be to reconsider the Gravitational Metric vis-a-vis the Visual Metric. That is to say, while the distance from the center to the arms of a galaxy may appear to be n miles or light years across, its gravitational distance might be entirely different.

This could come about in a number of ways. One way that suggests itself is to posit a granular universe composed of infinitely small units or grains. Gravitational distance would then be a function of the granular density - ie. the greater the density the further away the gravitational distance. Thus, planets, galactic spirals, black hole companions etc. would all have a “virtual gravitational orbit” determined by the number of gravitational units d between it and its sun, center or black hole.

Near a large body the radius of the virtual orbit would be greater than the radius of the visual orbit thus imparting to the object a greater rotational speed due to the conservation of angular momentum. For near Earth systems the difference between the visual and virtual orbits might be slight, but over large distances this difference might be considerable.
The radius of the virtual orbit would be given by nd where n is the number of gravitational units d. nd - r = Dr the difference between the radius of the virtual orbit and the radius of visual orbit. Dr should relate naturally to the curvature of space as well as giving a measure of the density of the gravitational units (nd/r = r). Where the gravitational and visual radii agree, r = 1.

The angular momentum L of a mass m moving in a circular orbit with linear speed v is given by: L =2pmr2/v.
Substituting nd for r the angular momentum of the virtual orbit is: L =2pm(nd)2/v. Since L is conserved and r is less than nd it follows that the angular velocity must increase which is precisely the observation that has led to positing the existence of dark matter.

By sampling enough anomalous galaxies and black hole satellites it should be possible to ascertain their virtual orbits and derive some measure of the size of these gravitational units and their relationship to h, c and G.

flyingbuttressman
QUOTE (mainframe+Jun 4 2012, 02:16 PM)
A recent survey of our part of the Milky Way failed to find any of the elusive dark matter posited to account for a presumed 83% matter shortfall needed to explain why galaxies don’t fly apart.

Source?
mainframe
Science News May 19, 2012
flyingbuttressman
QUOTE (mainframe+Jun 4 2012, 03:18 PM)
Science News May 19, 2012

Magazine? Online? Author?
mainframe
From the European Southern Observatory Internet Announcement

"... This research was presented in a paper, “Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood”, by Moni-Bidin et al. to appear in The Astrophysical Journal.

The team is composed of C. Moni Bidin (Departamento de Astronomía, Universidad de Concepción, Chile), G. Carraro (European Southern Observatory, Santiago, Chile), R. A. Méndez (Departamento de Astronomía, Universidad de Chile, Santiago, Chile) and R. Smith (Departamento de Astronomía, Universidad de Concepción, Chile)."

Check their site at eso.org
AlexG
I've seen a paper on arxiv which critiqued that study, stating that the stellar velocities that were estimated were very low, and when the same calculation were done using the correct velocities, it confirmed the presence of even more dark matter than was originally estimated.

Ah, here it is... http://arxiv.org/abs/1205.4033

QUOTE
An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic mid-plane by Moni Bidin et al. (2012) has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the invalid assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights; the correct assumption---that is, the one supported by data---is that the circular speed is independent of radius in the mid-plane
mainframe
You're correct but the idea is directed toward MOND (Modified Newtonian Dynamics) which does not need dark energy to explain galactic rotation. MOND, while not glamorous has a good track record.
rpenner
MOND has no track record in cosmology or galaxy clusters, however.

Thus even if MOND is true, dark matter exists.

The more parsimonious model is GR + dark matter + dark energy.
brucep
QUOTE (rpenner+Jun 6 2012, 08:09 PM)
MOND has no track record in cosmology or galaxy clusters, however.

Thus even if MOND is true, dark matter exists.

The more parsimonious model is GR + dark matter + dark energy.

MOND is in the 'round file'.

A direct empirical proof of the existence of dark matter
http://arxiv.org/abs/astro-ph/0608407
200 citations for this paper.

Plus the argument for the WMAP model.

The folks who don't read the literature are afraid of what it might say about their 'bubble universe'.
pmb
QUOTE (mainframe+Jun 4 2012, 06:16 PM)
A recent survey of our part of the Milky Way failed to find any of the elusive dark matter posited to account for a presumed 83% ..

Claims like this, when posted without backup information, should be dismissed out of hand. So, what proof do you have that such a survey occured and that its results were interpreted as you have?
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