Talk:Galaxy rotation curve

message: 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)
replies: text: The equation is correct (eg equation 3.20 on p. 100 of the Sparke & Gallagher 2000 textbook). What's confusing is that the Wikipedia article expresses the equation as \rho(r) = M / (4/3 \pi r^3); rho is the average density within a sphere of radius r, not the local density at radius r. More commonly (including in Sparke & Gallagher), this equation is expressed using M(<r), the mass enclosed within a radius r. However, it is the mass enclosed, expressed either M(<r) or rho as in the current version of the Wikipedia article, which is relevant for Kepler's law. The local mass density is not relevant. —Alex (ASHill | talk | contribs) 03:37, 20 December 2013 (UTC)
thread_title: Mass Distribution Models

message: ===Elliptical orbits===
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)
replies: text: Not true.  If it were angular velocity then it wouldn't be flat at large radii: v(r)~constant, but \omega(r)=v(r)/r\propto1/r.  And angular velocity is also a vector, although the distinction isn't important for a rotating disk. Cosmo0  —Preceding signed but undated comment was added at 18:41, 20 September 2007 (UTC)
thread_title:  Refactored from Archived Discussion 

message: 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)
thread_title: Elliptical orbits

message: 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)
replies: text: Not true.  If it were angular velocity then it wouldn't be flat at large radii: v(r)~constant, but \omega(r)=v(r)/r\propto1/r.  And angular velocity is also a vector, although the distinction isn't important for a rotating disk. Cosmo0  —Preceding signed but undated comment was added at 18:41, 20 September 2007 (UTC)
thread_title:  Velocity vs Speed 

message: 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)
thread_title:  Mysterious vs. Mundane Dark Matter 

message: 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)
thread_title: Reverted contributions

message: 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 
:Just to chime in with my view: it may not be an extreme minority theory but it is, at the moment, not well established as a serious alternative to CDM (despite your exaggerated account of it's successes).  In any case, as ScienceApologist says, the article on dark matter is the correct place for outlining different theories on the nature of dark matter.  From the point of view of galaxy rotation curves, the main debate is over whether dark matter is neccessary at all, although a single sentence pointing out that different kinds of dark matter predict slightly different rotation curves may be appropriate here. Cosmo0 (talk) 13:06, 12 January 2008 (UTC)
thread_title:  BEC or Scalar field dark matter model (SFDM) of halos is not an extrem minority theory 

message: 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)
replies: text: I've just discovered an explanation of the above with some arithmetic at .Brian O'Donnell (talk) 07:22, 30 July 2008 (UTC)
replies: text: What you say is perfectly true, but I don't quite see what your point is.  This is a well known fact, even if we often neglect it in practice when considering the average motions of stars in a galaxy.  It has no bearing on the need for dark matter - if that's what you're implying - since it doesn't contribute anything to the average rotation curve. Cosmo0 (talk) 14:23, 30 July 2008 (UTC)
replies: text: The problem here seems to be getting enough mass at the outer reaches of the galaxy. But what if the spaces between the arms were actually empty voids and all the mass was concentrated in the spirals? I.e. just as it appears in a telescope. The arms would have to be semi-stable structures, e.g. vortices, and gravity would act in a line of thrust along the axis of each arm. A test mass released at the end of an arm would curve along it into the centre instead of a direct straight line. A body in orbit would be accelerated forwards as well as inwards and would keep up with the arm to a greater extent than in a uniform disc. The need for dark matter would therefore be reduced or even eliminated for spiral galaxies.Brian O'Donnell (talk) 13:15, 5 August 2008 (UTC)

text:  If it is assumed that the mass distribution in the galaxy is uniform then a Newtonian solution is not possible. More subtly, if the idea of a centre of mass is assumed to be accurate enough within the galaxy, the same effect ensues. Between galaxies, the centre of mass approach is a good approximation but it is less accurate for less uniform mass distributions and for distances closer to the centre.If it is proposed that the arms are real, local effects have to be considered if they are to be stable. They would collapse into themselves along their axes unless the component stars were orbitting around each axis. Ata reciprocal simple harmonic motion is proposed but isn't this a kind of flattened ellipse? The website goes on to explain gravitational attraction to the arms as well as to the centre.I am not trying to rubbish the general idea of new physics, merely to point out that a solution using the old physics is plausible in this case.Brian O'Donnell (talk) 20:26, 16 August 2008 (UTC)
thread_title:  Direction of acceleration 

message: 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)
thread_title:  Galactic Jets 

message: 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)
thread_title:  Work of Cooperstock and Tieu 

message: 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)
replies: text: If that is true the article is wrong! From the article: "It [dark matter] has been uniquely successful in ... explaining the dynamics of groups and clusters of galaxies". Aarghdvaark (talk) 06:19, 31 January 2012 (UTC)
thread_title:  Radial Velocity Profiles in Globular Clusters 

message: 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)
thread_title:  The relevance of gravitational lensing needs to be explained 

message: 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)
replies: text: done Aarghdvaark (talk) 01:53, 1 February 2012 (UTC)
thread_title:  Rubin's inclusion in the main article text 

message: 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)
thread_title:  Just wondering if anyone had thought to take in account that space has could have mass and repulsive forces. 

message: 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)
replies: text: hopefully clarified with edit "represented by a graph that plots the orbital speed (in km/s) of the stars". Aarghdvaark (talk) 02:02, 1 February 2012 (UTC)
thread_title:  Velocity: Angular or Linear? 

message: 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)
thread_title:  "needs attention from an expert on the subject" heading 

message: 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)
thread_title: Citation needed

message: 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)
replies: text: A few reasons. First, we certainly don't include every result from the peer-reviewed literature. So while the source certainly meets the reliability criteria, that doesn't mean we have to include it. Second, per WP:FRINGE, we don't generally include results that haven't gained some standing in the literature. That paper, from 2012, has two citations, both of which are by the author (so no third-party citations). Citation counts are in no way a definitive measure of the importance of the result, but that supports my view that it's not considered a "significant-minority" idea, which is the kind of result WP:FRINGE says we should include. Third, Wikipedia's conflict of interest guideline makes it somewhat questionable to add your own result. (It's certainly ok per the reliability guidelines, as you say, but still a bit questionable to add your own paper -- I certainly avoid adding my own results. But thank you for clarifying that it is your work that you're adding.) Lastly, I think the wording as written was way to technical for an encyclopedia audience. I have no idea what the sentence means (and I'm an astronomer, so in principle much better-versed in this than the average reader). "Unruh radiation" is undefined, the meaning of "tuning parameter" is unclear, etc. My last objection could certainly be addressed, and the third point could be addressed if someone else added it, but the first two require, at the least, time and wider acceptance evidenced in reliable sources. —Alex (ASHill | talk | contribs) 16:31, 6 March 2015 (UTC)
replies: text: Thanks Alex for your well-reasoned reply. I tend to judge solely by agreement with the data & simplicity & not by community response, but I understand wp has a different slant on it. I do think my paper should be mentioned here, so hopefully time'll bring a citation. Best wishes 81.156.122.132 (talk) 17:33, 6 March 2015 (UTC)
replies: text: When I'm writing a paper, I certainly try to judge by agreement with the data and simplicity, but Wikipedia is in no place to judge that. Since we obviously shouldn't include every peer-reviewed result, community response in the literature is the best proxy we have. —Alex (ASHill | talk | contribs) 18:06, 6 March 2015 (UTC)
thread_title: Inertia and Unruh radiation paper

message: 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)
thread_title:  Hypothesis based on the conjectured graviton particle 

message: 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)
replies: text:  WP is no forum for general discussion, we give overview of what sources say. Your edit was POV and revert by the editor was justified. ThanksAhmadLX (talk) 10:54, 16 January 2019 (UTC)
replies: text:  unsigned has a point that applies to many of narratives of GR and QM. It needs to be made clear where theory does not match experiments and the linkage to other theories that adjust or tune for the discrepancy. For example, if science were to find that a graviton plasma permeates the universe it would cause major demolition, recasting, and reframing to many narratives and theories. J Mark Morris (talk) 15:55, 16 January 2019 (UTC)
thread_title:  Adherence to the Scientific Method 

message: 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)
thread_title:  Changing template message 

message: "
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)
thread_title:  Further investigations