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Dark matter. Nobody knows what it is, but it's thought to make up a quarter of the universe. If that's so, theory predicts that thousands of dark matter clumps should surround the Milky Way, each holding a small satellite galaxy.
“But if we actually look out and try to find galaxies corresponding to these clumps, we only see about 10 to 20 of them there. This is a huge mismatch.” James Bullock of U.C. Irvine at a dark matter conference last week at the Space Telescope Science Institute in Baltimore.
To complicate matters, the biggest dark matter clumps are the best candidates to contain satellite galaxies. And they just don't have any. “The weird thing that we're finding is if we actually go out and measure the masses of the satellites that we can see, little satellite galaxies, dwarf galaxies that we can see, if we measure those masses, those masses are actually smaller than a good number of the dark matter clumps that we predict should be there.” [Michael Boylan-Kolchin, James Bullock and Manoj Kaplinghat, "Too Big to Fail? The Puzzling Darkness of Massive Milky Way Subhalos"]
It's not clear why some dark matter clumps won't form galaxies despite their ample size. Bullock and company have a name for those galaxy-free clumps: “We were calling them massive failures.” Here’s wishing the search for a reason is a success.
—John Matson
[The above text is an exact transcript of this podcast.]
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10 Comments
Add CommentSo, the predictions of the referenced dark matter hypotheses are not confirmed by observation. Might not some scientists then reasonably question the viability of these dark matter hypotheses?
Reply | Report Abuse | Link to thisReminds me of another branch of science that is reluctant to accept contra evidence. We shall see in good time.
Reply | Report Abuse | Link to thisI agree completely. As a physicist, I'm amazed at the reluctance to give up the concept of "dark matter". At best, there is only indirect evidence not that "dark matter" exists but that something is missing in our understanding of galaxy rotation. "Dark matter" is conjectured, but our definition of it is completely what it is not, not what it is. Sounds more and more like science fiction to me, especially with yet more evidence that fails to find any real confirmation of "dark matter". I can't help but wonder if the reason is related to grants that current scientists are already funded for are specifically to find "dark matter". The sooner we examine in earnest alternate theories the better as far as I'm concerned. Can't wait to see the next new non-conformation data :)
Reply | Report Abuse | Link to thisI also agree that research funding is a critical factor, especially when all the research published since around 1980 that presumes the existence of dark matter is considered...
Reply | Report Abuse | Link to thisFYI - for a general overview of some newer alternative interpretation of observations, please see:
"Mass Distribution Characteristics Invalidate the Galaxy Rotation Problem",
http://www.sciencewithoutfiction.com/uploads/Mass_Distribution-_Galaxy_Rotation_Problem.pdf
For more formal technical and scientific research reports of galactic gravitational evaluation methods, please see:
"Rotating thin-disk galaxies through the eyes of Newton",
http://www.arxiv.org/abs/1007.3778
also,
"Is Dark Matter Present in NGC 4736? An Iterative Spectral Method for Finding Mass Distribution in Spiral Galaxies",
http://www.iopscience.iop.org/0004-637X/679/1/373/
A larger body of works can be found in their references.
The dark matter theory has taken on a religious tone with adherents using the total lack of any evidence as "proof" that their faith will one day be rewarded. It is the old "the book of revelations clearly says that 1,000 years will pass and then armageddon and it has been 2,000 years so revelations must be literaly true" kind of thinking. Indeed, what else would we expect from people that just can't admit their math is bad?
Reply | Report Abuse | Link to thisDark matter is OUT, think of MOND.
Reply | Report Abuse | Link to thislater (2004) is was ameliorated by Jacob Bekenstein, and is also known as TeVeS (Tensor/Vector/Scalar).
Gravity is scale abundant.
keep on thinking
Wilhelmus
In my humble opinion, MOND is merely analytical compensation for the improper representation of mass distribution in gravitational evaluations of exceedingly complex composite masses - the analytical equivalent to the compensatory mass intended by dark matter. They are both merely 'fudge' factors intended to moderate error. The simplistic laws of Planetary Motion are simply not applicable to galaxies - there is no need to force the simple centralized mass Keplerian rotational curve onto the distributed mass of galaxies.
Reply | Report Abuse | Link to thisYou are so right JT,
Reply | Report Abuse | Link to thiseverything is a "WHAT IF" solution of our minds, but it is good to break our heads on questions that we meet, and the further we go the more questions we will meet and the "WHAT IF" solutions will evolve.
keep on thinking
Wilhelmus
Thanks very much - very well put!
Reply | Report Abuse | Link to thisJim
The rotational curve of our own galaxy has been extended by more that double its prior distance through accurate distance and radial velocity measurements for hundreds of (ordinary matter) galactic halo objects. Please see:
Reply | Report Abuse | Link to thisBattaglia et al,(2005),"The radial velocity dispersion profile of the Galactic halo: Constraining the density profile of the dark halo of the Milky Way", http://www.arxiv.org/abs/astro-ph/0506102v2
Most critically, this study establishes that the rotational velocities of these discrete halo objects, including satellite galaxies, globular clusters and old stars orbiting beyond the galactic disc DO diminish as a function of their distance from the galactic center in general compliance with the Keplerian rotational curve.
Based on these observations, the referenced study established constraints for the location and density of any dark matter halos enveloping the Milky Way, since the velocities of these objects would not be diminishing if there was any dark matter present near their orbits.
However, more importantly, these observations also establish that the laws of planetary motion can be applied to discrete objects of mass that, in effect, independently orbit a dominating common central mass AND that they do not apply to compound, large scale self gravitating orbital masses such as spiral galaxies' discs.
This evidence strongly indicates that the initial requirement imposed on galactic discs, that their internal rotational velocities diminish as a function of their distance from the galactic center, was invalid. As a result, the requirement for undetected galactic mass provided by dark matter is invalid!
I only hope this simple reality can be soon recognized by the community of astrophysics...