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Models of mass distribution show rotation curves calculated entirely according to Newtonoian formula that match observation. This should be included in the article. A uniform spherical distribution model shows a rotation curve that slopes steeply up from center. A uniform disk model shows a rotation curve that slopes less steeply. A disk with a bulge of increased mass in the middle model shows the rotation curve noted in the article. Rising steeply in the bulge like the uniform spherical distribution then flat in the disk. An all mass in the middle model like the solar system shows a rotation curve that slopes down as the "predicted" line in the diagram.
Since these models predict rotation curves that match observations in all cases they should be included. These models also predict luminant and opaque matter distributions that match observation.
98.164.89.190 ( talk) 13:49, 24 May 2012 (UTC)
The equation
that claims to relate the mass density distribution to the rotation curve is not correct --- or it least it does not follow from Kepler's third law without some ascribing some unusual meaning to the "radial density profile". Asssuming spherical symmetry (is this reasonable?) a correct equation relating to the velocity curve is surely
I'd change the equation, but I'm not sure how the change would affect the rest of the section, which is confusing enough as it stands.
Mike Stone ( talk) 15:13, 19 March 2013 (UTC)
I can only underline that Eq. (??) is wrong. I think the derivation of the correct formula is simple enough to be stated in the Wikipedia. It can be done in the first semester in the usual physics curriculum at universities.
The first important feature of Newtonian gravity, which is sufficient for this purpose, is that the gravitational force on a body moving in an extended radially symmetric (around a center) mass distribution that consitutes the gravitational field is given by
where is Newton's gravitation constant, is the mass of the body, is the position vector relative to the center of the mass distribution, and is the total mass contained in a sphere around the center, i.e.,
To get the rotation curve, we make the simplifying assumption that the body runs on a circular orbit. Then you equate the centripetal force, necessary to keep the body on this orbit with the gravitational force, which gives
From (3) and (2) we find the relation of the velocity profle to the density distribution as
Vanhees71 ( talk) 08:57, 19 December 2013 (UTC)
One thing that I have never seen is an explanation of the galactic rotation curve that also explicitly takes into account the theory that the spiral arms are not in fact coherent but are a construct of the elliptical orbits of the stars that make them up, as explained by Image:Spiral galaxy arms diagram.png. The implication of this is that a star in a spiral arm is near the aphelion end of the ellipse, and so is going more slowly than a star on a circular orbit at that distance would be. If the ellipses themselves are turning and giving the illusion of the spiral arms rotating evenly, then the discrepancy could disappear. It seems unlikely that this has been overlooked, but I'd be interested to see a discusson that includes this aspect. — PhilHibbs | talk 18:41, 23 Feb 2005 (UTC)
The vertical axis of the graph really should be "Speed". I know that "Velocity" sounds more scientific, but velocity is a vector and that's not being represented on the graph, but only the magnitude, and the magnitude component of velocity is "speed". -- Ch'marr 15:29, 10 October 2005 (UTC) (the pedant)
Actually it would be correct to call it angular velocity, since that's what it is. 132.229.87.144 12:51, 4 August 2007 (UTC)
I've read in the past, either in "Light at the Edge of the Universe" or perhaps "The Whole Shebang" (I can't remember which) that the amount of matter required to explain the galaxy rotation curve effect was significantly less than the amount of matter required to explain the flat curvature of the universe in the FLRW metric. I should, I suppose, find the exact quote.
For the galaxy rotation curve, it was estimated that approximately 90% of the matter of the universe had to be "dark" which to me seems no great stretch of the imagination, just considering free hydrogen in a more-or-less smooth distribution. In the region of planets, of course, you wouldn't find it, because it's been swept away by the condensed masses. But the rings of Saturn (and the asteroid belt) are suggestive of a large amount of such sweeping. Anyway, a smooth region of gas would be consistent with the smoothness of the Cosmic Background. Consider that all the galaxies could be just condensations in a universe with an almost crystalline pattern of hydrogen gas, held apart by an almost perfectly symmetrical initial big bang. Galaxies could be whirlpools in a sea of hydrogen instead of a vacuum, as is usually assumed.
While nonbaryonic dark matter seems to exist, it seems to appear mainly in the course of violent explosions, with a very short half-life, and in insufficient quantities to create the Galaxy Rotation Curve result.
Corrections welcome. JDoolin 00:45, 22 August 2006 (UTC)
I reverted this contribution because it represents a rather extreme minority theory for an explanation of dark matter. If and when this idea receives more notice within the community we can begin to include it, but it will probably find itself at dark matter rather than here.
ScienceApologist ( talk) 18:22, 11 January 2008 (UTC)
I totally agree! It seems that it is very doubtful that in the end Dark Matter will still be considered, and to include something that has never been proven is wrong! Yes, it is a topic for 'Dark Matter', because that is where this unidentifiable stuff is being discussed.
Further, we MUST make up out minds what 'Dark Matter' is. This topic says that 84.5% of the mass in the universe is made of 'Dark Matter', where the words 'Dark Matter' have an attached URL. Clicking on this takes us to a page that says the mass is made up of some 26.8% of Dark Matter. The 86.4% represents the sum of both the Dark Matter and the Dark Energy. This implies that the authors are either stupid or totally disorganised. I would suggest that it is totally removed from this topic and discussed in the 'Dark Matter' page. At most, this page could just have half a sentence mentioning the total uncertainty in this area.
GilR 23:52, 19 April 2015 (UTC)
Dear ScienceApologist
I don't know how to contact you. So I wrote a mail here. Thank you for your efforts. But BEC or Scalar field dark matter model (SFDM) of halos is not an extremly minority theory. Actually, this model is a main alternative to standard cold dark matter model and the most successful model in explaing the rotation curves.It has many different names such as fuzzy, fluid, repulsive, scalar field, boson halo and so on.(Please see a review article in Science [1].)This model solves many problems of cold dark model (CDM) such as cuspy halo and missing satellite. There are already hundres of journal paper published about this idea and also many works saying the model predicts the observed rotation curves of galaxies and dwarf galaxies very well.(Please see review [2] page 21 and [3,4,5]) No other dark matter model have succeeded at this level in explaining the curves. Note that SFDM also behaves as CDM at the scale larger than galaxy, so it also explain large scale strures as much as CDM. Thus, I think, for balance, this model deserve space at least as much as the modified gravity theories which seems to be even not accepted by majority of physics community currently. As far as I understand, the philosophy of wikipedia is that users themselves make contents and the others review and edit the contents. Many experts in this field is already reading and editing this subject.(I am one of them) So, if my statements are wrong, missing something, or the model is an extremly minority which does not deserve publication, they will soon edit it. So please let the experts do it. [1] "New Light on Dark Matter" Jeremiah P. Ostriker and Paul Steinhardt Science 20 June 2003: Vol. 300. no. 5627, pp. 1909 - 1913 [2] "TOPICAL REVIEW: General relativistic boson stars" Franz E Schunck and Eckehard W Mielke arXiv:0801.0307v1 [astro-ph] [3] "Is dark matter a BEC or scalar field?"Jae-Weon Lee arXiv:0801.1442v1 [astro-ph] [4] "Mini-review on Scalar Field Dark Matter" L. Arturo Ure˜na–L´opez [5] "Scalar Field Dark Matter: head-on interaction between two structures" Phys.Rev. D74 (2006) 103002
Retrieved from " http://en.wikipedia.org/wiki/Talk:Galaxy_rotation_curve"
—Preceding unsigned comment added by Scikid ( talk • contribs) 07:12, 12 January 2008
It may be an over-simplification to assume a radial accelaration towards the centre of mass. From the viewpoint of a star near the rim of the galaxy, the concentration of mass in the spiral arms will act as a significant gravitational attractor, in comparison with the more distant central bulge.
Envisaging the space as a deformed stretched membrane, the outer reaches of the galaxy will look like a corrugation of valleys and ridges corresponding to the arms and voids respectively. A test mass would roll forwards down one of these valleys and spiral in towards the centre of mass. The acceleration would therefore have a forward as well as an inward component, speeding up the rotation of the outer parts and helping to preserve the structure of the spiral arms.
This would explain at least part of the observed phenomenon without modifying Newton or positing dark matter.
Brian O'Donnell (
talk)
15:47, 29 July 2008 (UTC)
How much of the anomalous rotation curve can be ascribed to gravitational attraction between stars and the long relativistic jets that the central supermassive black hole has been emitting for billions of years? It seems likely that some of the flattening of the rotation curve should be due to the long axial jets, which should extend far beyond the halo and beyond the radius ascribed to a spherical distribution of cold dark matter. I don't know how much mass is ejected into jets for either an active galactic nucleus or an old galaxy but their mass should affect stars at large enough distance from the galactic center. Perhaps the radius of the galactic bulge is a clue to the mass of the jets?
WalterU ( talk) 11:17, 25 June 2009 (UTC)
This should be added to the alternatives theory. Cooperstock is a decades-long researcher in GR with a long and fine publication record, and his contributions to this subject, insofar as they are a direct attack on this problem, should be pointed out. Antimatter33 ( talk) 14:23, 5 September 2009 (UTC)
Analysis of globular clusters shows similar anomalous behavior in the radial velocity distribution of cluster members. Since dark matter cannot account for these, while the work of Cooperstock, in principle, can (effect of non-linearity in GR, cluster members not test particles), this should also be pointed out in the "alternatives" section. Antimatter33 ( talk) 14:23, 5 September 2009 (UTC)
Someone significantly smarter than myself needs to explain how gravitational lens measurements can distinguish between a) alternative gravity theories, and b) dark matter. The statement is made that it does, but it feels like the article is truncated.
Though the fact doesn't surprise me, I can't see why gravitational lens predictions would differ between the two kinds of rotation anomaly]y explanations. -- TechnoFaye Kane 12:00, 13 December 2009 (UTC)
IMHO, the graph is embarrassing; Newtonion gravitation is known to be wrong, so why base ANYTHING on it? The argument that relativistic effects don't matter is IMHO BS, because there is a supermassive black hole in the center of the galaxy, and orbital speed of stars observed in outer reaches of other galaxies show that there is a fixed relation between the mass of the galactic supermassive hole and orbital speed of stars. That is, THE HOLE CONTROLS THE ENTIRE CURVE. So this is NOT evidence for dark matter, it is epicycles. —Preceding unsigned comment added by 128.231.213.25 ( talk • contribs)
Vera Rubin is present as a "See also" link and the first two entries in the bibliography. Should she be moved into the text itself? Her own article seems to suggest she most certainly should be. —Preceding unsigned comment added by 67.161.160.57 ( talk) 10:55, 14 November 2010 (UTC)
all this talk of dark matter and trying to explain abnormalities in the way the universe rotates and the way light is seen is retarded. Stop trying to find out what is wrong with the equations u all ready have and make up some new ones. Creating a fictional material to explain that u fucked up is childish. (dark matter my ass).
Signed, Keaton McMahon, 92234
I concur. Dark matter isn't really understood, and as a way of explaining that which is not understood it is a very limiting choice. Vera Rubin's discovery about the stars moving around the galaxy at the same speed was astonishing and brilliant. Wallpapering over a crucial discovery because it didn't fit with Newtonian physics was short-sighted to say the least. This was on par with the scientists that scoffed at the notion that something invisible could cause sickness - germs. Germs weren't accepted for a long time either. Scientists invented "dark energy" to ensure that her discovery fit within the old box of Newtonian beliefs, and have been struggling to explain that which they invented ever since.
I predict that one day there will be scientists who have an open mind. Not the scientists of the old paradigm, but the children of today that grow up and refuse to accept the limitations of the old paradigm. They'll dig deeper into this and discover that Vera Rubin was actually pointing the way to a new law of physics, a pull and push force in the galaxy. There'll come a point when the belief of a black hole at the centre of the galaxy is proven false as well. The classical comment runs along the lines of statements such as, "The only compelling explanation is that there is a supermassive black hole lurking there." That's right, when you actually look for EVIDENCE that there's a black hole at the Centre of the galaxy, the best you get is a "compelling explanation."
I've raised this point because what is at the Centre of the galaxy is DIRECTLY related to the speed of the stars moving around the galaxy. And I can assure you, it's not a black hole, and the invented concept of Dark Energy does NOT explain things either.
Right now, we're looking out at the galaxy with a monocular view - we see from the Earth. I predict that when we have the ability to look in stereo, from two different points, into the galaxy we'll see some astonishing patterns in the galaxy that will shatter this invention called, Dark Energy.
And do you want to know what's funny? No scientist can prove me wrong on what I've just written. At best, they can share the conclusions they've falsely drawn. Why? Because Dark Energy was a concept invented to protect a prized belief. Newtonian physics can explain the mechanics of the solar system, but NOT the galaxy.
I'm on record. I'm willing to wait to be proven right. But regardless, I've provided as much evidence as scientists of today have about dark matter.
Signed, Carmien Owen — Preceding unsigned comment added by Carmien Owen ( talk • contribs) 05:11, 10 July 2017 (UTC)
Just one question: The diagram in the article does not have units for velocity, so it is unclear to me if this is angular (revolutions per time) or linear (distance per time) speed. And the text offers no clues for me… A physics buff probably takes one look and knows, but I have no idea. 217.237.90.57 ( talk) 16:27, 30 December 2011 (UTC)
The Y axis of the graph shows linear velocity, measured in km/s; in fact, it's true that in this case it should be called Speed, instead of Velocity, as velocity is a vector, and therefore, a sign (positive or negative) should be used in order to express the whole measurement: notice that we are working with absolute values of velocity, that is, the magnitude component of the vector, as we just want to see how it changes deppending on the absolute value of the distance (which initially was a vector -displacement-, but now we just use its magnitude component, so it's scalar -distance-). If we plotted an angular speed Vs distance graph, we would see that the line would remain constant in the part that previously was a 'growing' line (where linear speed increased at a constant ratio), and it would tend to decrease in the part in which linear speed remains constant (horizontal line in the original graph). Hope it's helpful. Pichiniqui ( talk) 00:55, 8 January 2012 (UTC)
I'm removing this tag. I went over the article a few months ago and there have been only minor changes since then. So, although I'm not an expert, it seems no expert is coming along to the rescue and the article is good enough not to cause problems. Also there was no section added here in talk explaining why the tag was needed in the first place. If you put the "needs attention from an expert on the subject" tag back, please also discuss here why you think it needs attention. Aarghdvaark ( talk) 03:04, 16 April 2012 (UTC)
The original wording in this section and my first change are given here [4]. The original is clearly wrong since there has been no observation of the distribution of dark matter. A small edit war then ensued about whether the wording should be "the simulations assume" (me) or "the simulations show" ( User:Junjunone [5], with finally an article cited by Junjunone, presumably in support of his view. I have skimmed the article and I don't understand why Junjunone cited it? The last sentences in the conclusion are "The hypothesis that the inclusion of baryons would resolve the discrepancy between theory and observation have been shown to be wrong. Worse, the disagreement actually grows larger if one utilises strong feedback physics schemes that can reproduce the observed stellar fractions in these systems". There is more of course, but I think I'm justified on the basis of this cited paper on stating that "State-of-the-art cosmological and galaxy formation simulations of dark matter with normal baryonic matter included do not resolve the discrepancy between theory and observation". Aarghdvaark ( talk) 14:42, 14 September 2012 (UTC)
Junjunone has taken this further. This is the timeline of his actions on 17 Sep 2012:
Those are the pages I'm aware of. Suggest to keep everything in one place that further discussion on content only be at Wikipedia talk:WikiProject Astronomy#Need a dark matter.2Fbaryonic matter simulations expert? Aarghdvaark ( talk) 03:35, 18 September 2012 (UTC)
After reading the rather confused commentary here, I am of the opinion that the problem is one of WP:DUE. In particular, Stacy McGaugh's reasonable pointing out that MOND works well for galaxy rotation curves should be discussed in this article, but we currently devote a bit too much to it in relation to what the literature shows. The Tully-Fisher relation has no scatter and MOND reproduces some interesting bumps and wiggles that are not as easily accounted for in the halo fitting picture, but that's, for better or worse, only a small part of the galaxy rotation curve story. We have little discussion here on how these plots are actually made, how the data is gathered, and what the standard way of fitting dark matter profiles is. I think that if this was added to the article with some paring back of the WP:BALL issues associated with McGaugh's work, we could resolve much of this. I am willing to begin writing this revision soon. Junjunone ( talk) 03:13, 24 September 2012 (UTC)
It would be a good idea to have actual data and modeling for this article like this image. We need to find one that is free for use. I could create new images, but it would be good if I didn't have to spend my time on that. Junjunone ( talk) 14:30, 1 October 2012 (UTC)
The article that is missing here may be this one: http://adsabs.harvard.edu/full/1978ApJ...225L.107R
Extended rotation curves of high-luminosity spiral galaxies. IV - Systematic dynamical properties, SA through SC by Rubin, V. C.; Thonnard, N.; Ford, W. K., Jr. 78.42.234.105 ( talk) 10:13, 26 February 2014 (UTC) buonshi
The concept of Salucci's group that there exists one universal rotation curve is not acknowledged by any group except their own, really. There are a few MONDians who cite their papers, but other than that there doesn't seem to be outside notice of the ideas. Therefore usable content should be merged here. jps ( talk) 18:13, 29 October 2014 (UTC)
I don't see anyone proposing anything but me. I've merged the content that is most clearly citable to external reviewers. Can we just proceed with the merge? jps ( talk) 13:11, 2 November 2014 (UTC)
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Hi. I'd like to query your deletion of my paper. It was published in a good peer reviewed journal, so it fulfils wikipedia's stated reliability criterion and to delete it without reason makes a mockery of the correct peer review process. Since it predicts galaxy rotation as well as dark matter and MoND, but does it without any tuning, it should be mentioned on this page. 81.156.122.132 ( talk) 16:05, 6 March 2015 (UTC) — Preceding unsigned comment added by 81.156.122.132 ( talk) 15:59, 6 March 2015 (UTC)
I would like to plant a flag based on a new narrative. I realize it won't be accepted immediately, so I am not proposing article changes now, but I think if this idea gains support and is not rejected on a scientific basis, then changes wil be warranted.
If galactic supermassive black holes decompose ingested matter and energy into fundamental electrinos and positrinos (-/+ 1/3 charge), and emit them as graviton plasma, possibly via the high energy jets, it could inform galactic rotatation curves in two ways without resorting to dark matter.
1. The conversion of matter and energy into electrinos and positrinos which are emitted/jetted as graviton plasma, means that the black hole is losing mass. By the standard equations, this will gradually increase the orbit radius of stars and other galactic matter.
2. The emitted/jetted gravitons create more of what physicists currently call spacetime. The outflow of gravitons also gently moves galactic matter to increased orbital radii.
Lastly, and I'm not sure exactly how this would play out, but gravitons decay into energy and matter-energy. Depending on the decay rate of the emitted/jetted gravitons, this could change galaxy dynamics.
Thank you for your consideration of these new ideas. Please respond to the hypothesis scientifically.
J Mark Morris ( talk) 17:29, 29 December 2018 (UTC)
Undoer' seems to think modern cosmology is devoid of the scientific method, that General Relativity requires no falsification condition.
If this is the case, modern cosmology belongs in the religious portal, not the science.
The falsification condition of General Relativity was the Galaxy Rotational Problem, it is necessary to mention this or GR is unfalsifiable pseudo-science. A hypothesis such as dark matter or black hole, with the expressed purpose of salvaging GR, is the classic definition of goal-post moving. — Preceding unsigned comment added by 120.28.231.216 ( talk) 08:19, 16 January 2019 (UTC)
WP:NOTFORUM. Additions to articles require reliable sources: do you have any? - Parejkoj ( talk) 18:11, 16 January 2019 (UTC)
Hello all, I removed some of the template messages on this page because the one saying this page needed expert attention seems to be outdated, if anything, because a lot of the equations on this page are currently accepted. Additionally, the lead does actually summarize the article, and the concept in general. Thanks!
Sam-2727 ( talk) 23:39, 23 February 2019 (UTC)
" Comparison of rotating disc galaxies in the present day (left) and the distant Universe (right).[21] The rotational dynamics of galaxies are well characterized by their position on the Tully–Fisher relation, which shows that for spiral galaxies the //asymptotic// rotational velocity is uniquely related to their total luminosity. "
Shouldn't it say asymptotic here? 23:50, 4 June 2021 (UTC)~