text:
Talk:Galaxy rotation curve

Mass Distribution Models
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

$$ \rho(r) = \frac{3 v(r)^2}{4 \pi G r^2}\quad (??) $$

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 $$ \rho(r)$$ to the velocity curve  is surely

$$ v^2(R) = \frac{4\pi G_N}{R} \int_0^R r^2 \rho(r) dr $$

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

$$ \vec{F}=-\frac{G_N m M(r)}{r^2} \frac{\vec{r}}{r}, \qquad (1) $$

where $$G_N$$ is Newton's gravitation constant, $$m$$ is the mass of the body, $$\vec{r}$$ is the position vector relative to the center of the mass distribution, and $$M(r)$$ is the total mass contained in a sphere around the center, i.e.,

$$ M(r)=4 \pi \int_{0}^{r} \mathrm{d} r' r'^2 \rho(r'). \qquad (2) $$

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

$$ \frac{m v^2(r)}{r}=\frac{G_N m M(r)}{r^2} \; \Rightarrow \; v(r)=\sqrt{\frac{G_N M(r)}{r}}. \qquad (3) $$

From (3) and (2) we find the relation of the velocity profle to the density distribution as

$$ M(r)=\frac{r v^2(r)}{G_N} \; \Rightarrow \; \rho(r)=\frac{M'(r)}{4 \pi r^2}=\frac{1}{4 \pi G_N r^2} \frac{\mathrm{d}}{\mathrm{d} r} [r v^2(r)]. $$ Vanhees71 (talk) 08:57, 19 December 2013 (UTC)
 * 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)

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)

Velocity vs Speed
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)

 * 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$$\propto$$1/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)

Mysterious vs. Mundane Dark Matter
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)

Reverted contributions

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)

BEC or Scalar field dark matter model (SFDM) of halos is not an extrem minority theory
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)

Direction of acceleration
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)

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)
 * I've just discovered an explanation of the above with some arithmetic at .Brian O'Donnell (talk) 07:22, 30 July 2008 (UTC)
 * 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)
 * 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)
 * 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.

Galactic Jets
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)

Work of Cooperstock and Tieu
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)

Radial Velocity Profiles in Globular Clusters
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)
 * 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)

The relevance of gravitational lensing needs to be explained
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. -- Techno Faye Kane 12:00, 13 December 2009 (UTC)

Newtonian gravitation is wrong
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)

 * Well, there are a couple of things you can do here. If you have a reliable source that backs up your assertion that the galaxy rotation curve can be explained by relativistic corrections and "epicycles" then you can include it in the article. If, on the other hand, you believe you have a unique explanation for the galaxy rotation curve that has not yet been discovered by mainsteam science then write a paper, get it published in a peer-reviewed journal and then include it in the article. Gandalf61 (talk) 10:04, 25 March 2010 (UTC)

 * The bigger point is that this problem being based in Newtonian gravitation is a non-starter. How is it a problem when we know the tools being used are wrong?
 * In the current article is this:
 * > A model of galaxy based on a general relativity metric was also proposed, showing that the rotation curves for the Milky Way, NGC 3031, NGC 3198 and NGC 7331 are consistent with the mass density distributions of the visible matter, avoiding the need for a massive halo of exotic dark matter.
 * > According to a 2020 analysis of the data produced by the Gaia spacecraft, it would seem possible to explain at least the Milky Way's rotation curve without requiring any dark matter if instead of a Newtonian approximation the entire set of equations of general relativity is adopted.[44]
 * > In March 2021, Gerson Otto Ludwig published a model based on general relativity that explains galaxy rotation curves with gravitoelectromagnetism.[45]
 * So is there even a problem or are we all stuck debating dark matter because the wrong tools were used in the first place?
 * 50.35.113.183 (talk) 19:25, 17 May 2023 (UTC)

Rubin's inclusion in the main article text
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)

 * done Aarghdvaark (talk) 01:53, 1 February 2012 (UTC)

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

Velocity: Angular or Linear?

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)

 * 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)

"needs attention from an expert on the subject" heading
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)

Further investigation
The original wording in this section and my first change are given here. 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, 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)

 * It appears that Aarghdvaark is not capable of understanding the papers beings cited. A standard treatment in simulations is to add baryons to dark matter. In these scenarios, the baryons follow the dark matter because gravity works that way. The cited paper shows that this happens and then asks the question whether feedback from baryonic processes can affect the dark matter and they get a negative as the answer. The simple fact is that this is just an example of one of the hundreds of papers written that show that baryons follow the dark matter. There are no assumptions and it is a bit strange that one would change the wording of the sentence to refer to a completely separate issue. Junjunone (talk) 16:00, 15 September 2012 (UTC)

 * Don't be so patronizing. It is obvious that normal matter will follow dark matter since the assumption is that dark matter is subject to gravity and that there is approximately five times as much exotic dark matter as normal matter. Have you really just used the paper by Duffy et al to try and justify the seemingly simple and innocuous looking sentence that "state-of-the-art ... simulations ... show that baryonic matter traces dark matter structures" ? But this sentence is wrong:
 * the presumed distribution of dark matter is in a Dark matter halo around a galaxy, and obviously this is not how baryonic matter is distributed - so baryonic matter clearly does not trace dark matter structures.
 * the sentence is too emphatic as it could easily be read as implying dark matter structures had been observed, when no one has seen any dark matter structure outside of a simulation.
 * the point under discussion is not that baryonic matter "traces" or follows dark matter, but why the baryonic matter tail wags the dark matter dog - why is the amount of dark matter the right amount to make the galaxy rotation curve appear to depend on the baryonic matter, as per the well-established Tully-Fisher relation?

 * I took it that rather than trying to support the facile truism that baryonic matter and dark matter are both affected by gravity, you had cited Duffy et al's paper to support a statement something like "state-of-the-art ... simulations ... show that the amount of dark matter is dependent on the amount of baryonic matter" or the other way round - either of which which would go some way to explaining the Tully-Fisher relation. The paper is well written and is a summary of a large number of simulations. They investigate the back-reaction of baryons on the dark matter halo density profile - i.e. is the amount of dark matter dependent on the amount of baryonic matter, or can the tail wag the dog. Their conclusions were:
 * "in the inner ten per cent of the virial radius the models are only successful if we allow their parameters to vary with baryonic physics, halo mass and redshift, thereby removing all predictive power" (my emphasis). What they mean is the models only show the correct result if the input parameters are adjusted to give the correct result. Or to put it another way, there is no theory to show any direct relation between the amount of dark matter and the amount of baryonic matter up to 10% of the virial radius.
 * "On larger scales the profiles from dark matter only profiles consistently provide better fits", and "The most significant effects occur in galaxies at high redshift, where there is a strong anti-correlation between the baryon fraction in the halo centre and the inner slope of both the total and the dark matter density profiles" (my emphasis). i.e. there was a hypothesis which sought to explain how the amount of dark matter could depend on the amount of baryonic matter - only that hypothesis has been shown to be utterly wrong because it actually made things worse.
 * As I said the paper is well written and the conclusions are clear - state of the art simulations demonstrate there is no dark matter theory which can currently explain the Tully-Fisher relation. Aarghdvaark (talk) 04:41, 17 September 2012 (UTC)

 * There is something seriously wrong with your reading comprehension. I will ask to find out what the procedure is for disciplining someone who either misrepresents sources or cannot understand very simple points of clarification. Junjunone (talk) 17:22, 17 September 2012 (UTC)
 * Junjunone, Please avoid personal attacks against other editors. Comment on content, not personality.  Thanks.  Ebikeguy (talk) 01:30, 18 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? Aarghdvaark (talk) 03:35, 18 September 2012 (UTC)
 * 17:27 asks question at Teahouse/Questions
 * 17:34 asks for me to be topic banned Administrators' noticeboard/Archive239
 * 18:26 asks for an expert at Wikipedia talk:WikiProject Astronomy
 * 18:35 has gone all the way to the top User talk:Jimbo Wales/Archive 115
 * That doesn't make sense, why would we move the discussion about the article off this page? The ANI thread and Jimbo thread have nothing directly to do with this discussion. IRWolfie- (talk) 00:01, 19 September 2012 (UTC)
 * OK keep it here. Aarghdvaark (talk) 22:42, 19 September 2012 (UTC)

 * You said "There has been no observation of the distribution of dark matter": : "Direct measurement of a dark-matter ‘filament’ confirms its existence in a galaxy supercluster." It sounds like the basis of much of your reasoning above, and for the removal is original research. IRWolfie- (talk) 23:16, 18 September 2012 (UTC)
 * I'm not sure I see the relevance of your reference here. The article is about galactic rotation curves, and hence is concerned with the dark matter distribution within galaxies. I read Aarghdvaark's statement as saying that there has been no observation of the dark matter distribution on these scales (i.e. on scales of tens of kiloparsecs). The Nature news article you link to is concerned with an observation of dark matter on the scale of a supercluster of galaxies, and tells us something about how dark matter is distributed between galaxy clusters, on a scale of greater than a megaparsec, but not about how it's distributed on smaller scales. Scog (talk) 13:19, 19 September 2012 (UTC)
 * Hi IRWolfie. Did you actually read this reference you cite above or just go on the headline: "Direct measurement of a dark-matter ‘filament’ confirms its existence in a galaxy supercluster"? Because it says there "Mark Bautz ... notes that astrophysicists do not know precisely how visible matter follows the paths laid out by dark matter", which is exactly the point I was making. Incidentally, I would also disagree with the claim of direct measurement of dark matter, because what they actually did was "the team calculated that no more than 9% of the filament's mass could be made up of hot gas. The team's computer simulations suggest that roughly another 10% of the mass could be due to visible stars and galaxies. The bulk, therefore, must be dark matter, says Dietrich". That's not direct observation, that's using simulations to predict what is happening in some observations. Sloppy writing in Nature - sigh Aarghdvaark (talk) 00:27, 20 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)

 * Junjunone. The statement you have put back in: "though state-of-the-art cosmological and galaxy formation simulations of dark matter with normal baryonic matter included show that baryonic matter traces dark matter structures" is at the very least misleading, e.g. see above for the cite from IRWolfie- that "astrophysicists do not know precisely how visible matter follows the paths laid out by dark matter". As I said before, since ordinary matter and dark matter are both affected by gravity they will tend to clump in the same place - that's a no-brainer. So either your sentence is trivial if you meant that, or wrong if you meant that dark matter determines precisely where ordinary matter ends up. Instead of asking for me to be banned for not understanding you, try and argue your case and explain what you meant to say. Aarghdvaark (talk) 03:56, 29 September 2012 (UTC)

 * There is something you're missing, but I'm not sure what it is. Either your opinion of what is trivial is not trivial to me, or your view of what "precisely" means is beyond what any source we have or what any statement being made is trying to say. In any case, I do not see this as being meaningful once this page is rewritten since the discussion of McGaugh's points will be diminished to the level that they are considered in reference to this subject. Junjunone (talk) 01:52, 30 September 2012 (UTC)

 * When challenged about what you have written, you are supposed to explain in more detail what you mean by what you write. Not just say it is the readers fault if they cannot understand you. You have actually done nothing apart from repeat your original sentence all through this and avoided any attempt to explain yourself, see above for a typical example - that is not constructive argument. Aarghdvaark (talk) 14:08, 1 October 2012 (UTC)
 * I don't understand what your challenge means and I welcome your clarification. I believe it is based primarily on something you are not understanding properly, but I am not sure exactly where your misconception lies from what you are writing as there are two distinct possibilities I outlined. I agree that this argument is not constructive, which is why I think you should not continue here as your comments are mostly distractions from the job of retooling the article. Junjunone (talk) 14:30, 1 October 2012 (UTC)
 * A good start would be to write what you are trying to say in a different way, here, on the talk page. Aarghdvaark (talk) 22:33, 1 October 2012 (UTC)
 * I think that's what I'm doing. Junjunone (talk) 11:59, 2 October 2012 (UTC)

Images
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)

 * Regarding the below image used at the top of the article:
 * [[File:GalacticRotation2.svg]]
 * The embedded comment in the wikitext at the top of the article asks where the image came from. Visually, it appears that the creator of the .svg may have based it on the image here:  http://astrodidyouknow.blogspot.com/2011/07/proof-that-dark-matter-exists.html.  As for additional images, you can find some at the Harvard citation under the image, or by a search for "spiral galaxy rotation curves" on Arxiv.org.  I'll be referencing a couple of those papers in an upcoming article.  Cheers, Al'Beroya (talk) 09:46, 11 July 2014 (UTC)

 * The article could be improved by including a Newton/Kepler image of rotation curve like this (from here) as comparison, illustrating the mass distribution difference between solar scale and galaxy scale. As the article says, "In contrast, the orbital velocities of planets in planetary systems and moons orbiting planets decline with distance" TGCP (talk) 13:35, 19 April 2019 (UTC)

Citation needed
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

Universal rotation curve merge
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)

 * this is not true it is is a lie The Universal Rotation Curve, the existence of a function of the galaxy radius (in units of the disk length scale, $$R_D$$) and of galaxy magnitude (e.g.$$M_I$$ ) which reproduces the rotation curve of any object (of known $$M_I$$ and $$R_D$$). This concept, was first put at page 450 by Rubin et al  1982ApJ...261..439,  is implicit in Rubin et al. (1985) was pioneered in and then set in and . many others hanity ve contributed These papers have received more than 3000 citations . Jps is taking a solitary battle against me , protected by the immunity of the anonimity
 * Paolosalucci (talk) 21:16, 29 October 2014 (UTC)
 * You're the one with a WP:COI, so it's especially important to treat others with respect as it is up to them to determine how to address this, not you.
 * The sources and context you've provided is extremely helpful. Nice to see something published in the past decade. --Ronz (talk) 23:28, 29 October 2014 (UTC)
 * The above mentions page 450 of as supporting the URC model of Salucci et al. Having just read that page, I don't see it.  Would you please clarify?  Leegrc (talk) 12:08, 30 October 2014 (UTC)

 * Oppose The proposing editor started an AfD that was closed as keep, "seems that there are sufficient sources to meet GNG" less than two weeks ago. This merge proposal does not seem productive. Paradoctor (talk) 10:35, 30 October 2014 (UTC)
 * Please WP:FOC. We're now discussing the concerns in more detail than in the AfD. Given the sources offered so far, a merge may be the best way forward. --Ronz (talk) 20:05, 30 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)
 * Go ahead with the merge, as Paradoctor has withdrawn from the topic. --Ronz (talk) 16:31, 2 November 2014 (UTC)

Inertia and Unruh radiation paper
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)
 * 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)
 * 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)
 * 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)

Hypothesis based on the conjectured graviton particle
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)

Adherence to the Scientific Method
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 is no forum for general discussion, we give overview of what sources say. Your edit was POV and revert by the editor was justified. Thanks  AhmadLX  ( talk ) 10:54, 16 January 2019 (UTC)
 * 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)

WP:NOTFORUM. Additions to articles require reliable sources: do you have any? - Parejkoj (talk) 18:11, 16 January 2019 (UTC)

Changing template 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)

Further investigations
" 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)~

title: Talk:Galaxy rotation curve


text:
List of unsolved problems in physics

The following is a list of notable unsolved problems grouped into broad areas of physics.

Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

There are still some questions beyond the Standard Model of physics, such as the strong CP problem, neutrino mass, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself—the Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions (for example within known spacetime singularities like the Big Bang and the centres of black holes beyond the event horizon).

General physics

 * Theory of everything: Is there a singular, all-encompassing, coherent theoretical framework of physics that fully explains and links together all physical aspects of the universe?
 * Dimensionless physical constants: At the present time, the values of various dimensionless physical constants cannot be calculated; they can be determined only by physical measurement. What is the minimum number of dimensionless physical constants from which all other dimensionless physical constants can be derived? Are dimensional physical constants necessary at all?

Quantum gravity

 * Quantum gravity: Can quantum mechanics and general relativity be realized as a fully consistent theory (perhaps as a quantum field theory)? Is spacetime fundamentally continuous or discrete? Would a consistent theory involve a force mediated by a hypothetical graviton, or be a product of a discrete structure of spacetime itself (as in loop quantum gravity)? Are there deviations from the predictions of general relativity at very small or very large scales or in other extreme circumstances that flow from a quantum gravity mechanism?
 * Black holes, black hole information paradox, and black hole radiation: Do black holes produce thermal radiation, as expected on theoretical grounds? Does this radiation contain information about their inner structure, as suggested by gauge–gravity duality, or not, as implied by Hawking's original calculation? If not, and black holes can evaporate away, what happens to the information stored in them (since quantum mechanics does not provide for the destruction of information)? Or does the radiation stop at some point, leaving black hole remnants? Is there another way to probe their internal structure somehow, if such a structure even exists?
 * The cosmic censorship hypothesis and the chronology protection conjecture: Can singularities not hidden behind an event horizon, known as "naked singularities", arise from realistic initial conditions, or is it possible to prove some version of the "cosmic censorship hypothesis" of Roger Penrose which proposes that this is impossible? Similarly, will the closed timelike curves which arise in some solutions to the equations of general relativity (and which imply the possibility of backwards time travel) be ruled out by a theory of quantum gravity which unites general relativity with quantum mechanics, as suggested by the "chronology protection conjecture" of Stephen Hawking?
 * Holographic principle: Is it true that quantum gravity admits a lower-dimensional description that does not contain gravity? A well-understood example of holography is the AdS/CFT correspondence in string theory. Similarly, can quantum gravity in a de Sitter space be understood using dS/CFT correspondence? Can the AdS/CFT correspondence be vastly generalized to the gauge–gravity duality for arbitrary asymptotic spacetime backgrounds? Are there other theories of quantum gravity other than string theory that admit a holographic description?
 * Quantum spacetime or the emergence of spacetime: Is the nature of spacetime at the Planck scale very different from the continuous classical dynamical spacetime that exists in General relativity? In loop quantum gravity, the spacetime is postulated to be discrete from the beginning. In string theory, although originally spacetime was considered just like in General relativity (with the only difference being supersymmetry), recent research building upon the Ryu–Takayanagi conjecture has taught that spacetime in string theory is emergent by using quantum information theoretic concepts such as entanglement entropy in the AdS/CFT correspondence. However, how exactly the familiar classical spacetime emerges within string theory or the AdS/CFT correspondence is still not well understood.
 * Problem of time: In quantum mechanics, time is a classical background parameter, and the flow of time is universal and absolute. In general relativity, time is one component of four-dimensional spacetime, and the flow of time changes depending on the curvature of spacetime and the spacetime trajectory of the observer. How can these two concepts of time be reconciled?

Quantum physics

 * Yang–Mills theory: Given an arbitrary compact gauge group, does a non-trivial quantum Yang–Mills theory with a finite mass gap exist? (This problem is also listed as one of the Millennium Prize Problems in mathematics.)
 * Quantum field theory (this is a generalization of the previous problem): Is it possible to construct, in a mathematically rigorous way, a quantum field theory in 4-dimensional spacetime that includes interactions and does not resort to perturbative methods?

Cosmology and general relativity

 * Axis of evil: Some large features of the microwave sky at distances of over 13 billion light years appear to be aligned with both the motion and orientation of the solar system. Is this due to systematic errors in processing, contamination of results by local effects, an unexplained violation of the Copernican principle and thus the concordance model, or are these features simply statistically insignificant?
 * Fine-tuned universe: The values of the fundamental physical constants are in a narrow range necessary to support carbon-based life. Is this because there are an infinite number of other universes with different constants, or are our universe's constants the result of chance, or some other factor or process? (See also the anthropic principle.)
 * Cosmic inflation: Is the theory of cosmic inflation in the very early universe correct, and, if so, what are the details of this epoch? What is the hypothetical inflaton [sic] scalar field that gave rise to this cosmic inflation? If inflation happened at one point, is it self-sustaining through inflation of quantum-mechanical fluctuations, and thus ongoing in some extremely distant place?
 * Horizon problem: Why is the distant universe so homogeneous when the Big Bang theory seems to predict larger measurable anisotropies of the night sky than those observed? Cosmological inflation is generally accepted as the solution, but are other possible explanations such as a variable speed of light more appropriate?
 * Origin and future of the universe: How did the conditions for anything to exist arise? Is the universe heading towards a Big Freeze, a Big Rip, a Big Crunch, or a Big Bounce?
 * Size of universe: The diameter of the observable universe is about 93 billion light-years, but what is the size of the whole universe? Is the universe infinite?
 * Baryon asymmetry: Why is there far more matter than antimatter in the observable universe? (This may be solved due to the apparent asymmetry in neutrino-antineutrino oscillations.)
 * Cosmological principle: Is the universe homogeneous and isotropic at large enough scales, as claimed by the cosmological principle and assumed by all models that use the Friedmann–Lemaître–Robertson–Walker metric, including the current version of the ΛCDM model, or is the universe inhomogeneous or anisotropic? Is the CMB dipole purely kinematic, or does it signal anisotropy of the universe, resulting in the breakdown of the FLRW metric and the cosmological principle? Is the Hubble tension evidence that the cosmological principle is false? Even if the cosmological principle is correct, is the Friedmann–Lemaître–Robertson–Walker metric the right metric to use for our universe? Are the observations usually interpreted as the accelerating expansion of the universe rightly interpreted, or are they instead evidence that the cosmological principle is false?
 * Copernican principle: Are cosmological observations made from Earth representative of observations from the average position in the universe?
 * Cosmological constant problem: Why does the zero-point energy of the vacuum not cause a large cosmological constant? What cancels it out?

 * Dark matter: What is the identity of dark matter? Is it a particle? If so, is it a WIMP, axion, the lightest superpartner (LSP), or some other particle? Or, do the phenomena attributed to dark matter point not to some form of matter but actually to an extension of gravity?
 * Dark energy: What is the cause of the observed accelerating expansion of the universe (the de Sitter phase)? Are the observations rightly interpreted as the accelerating expansion of the universe, or are they evidence that the cosmological principle is false? Why is the energy density of the dark energy component of the same magnitude as the density of matter at present when the two evolve quite differently over time; could it be simply that we are observing at exactly the right time? Is dark energy a pure cosmological constant or are models of quintessence such as phantom energy applicable?
 * Dark flow: Is a non-spherically symmetric gravitational pull from outside the observable universe responsible for some of the observed motion of large objects such as galactic clusters in the universe?
 * Shape of the universe: What is the 3-manifold of comoving space, i.e., of a comoving spatial section of the universe, informally called the "shape" of the universe? Neither the curvature nor the topology is presently known, though the curvature is known to be "close" to zero on observable scales. The cosmic inflation hypothesis suggests that the shape of the universe may be unmeasurable, but, since 2003, Jean-Pierre Luminet, et al., and other groups have suggested that the shape of the universe may be the Poincaré dodecahedral space. Is the shape unmeasurable; the Poincaré space; or another 3-manifold?
 * Extra dimensions: Does nature have more than four spacetime dimensions? If so, what is their size? Are dimensions a fundamental property of the universe or an emergent result of other physical laws? Can we experimentally observe evidence of higher spatial dimensions?

High-energy/particle physics

 * Hierarchy problem: Why is gravity such a weak force? It becomes strong for particles only at the Planck scale, around GeV, much above the electroweak scale (100 GeV, the energy scale dominating physics at low energies); why are these scales so different from each other? What prevents quantities at the electroweak scale, such as the Higgs boson mass, from getting quantum corrections on the order of the Planck scale? Is the solution supersymmetry, extra dimensions, or just anthropic fine-tuning?
 * Magnetic monopoles: Did particles that carry "magnetic charge" exist in some past, higher-energy epoch? If so, do any remain today? (Paul Dirac showed the existence of some types of magnetic monopoles would explain charge quantization.)
 * Neutron lifetime puzzle: While the neutron lifetime has been studied for decades, there currently exists a lack of consilience on its exact value, due to different results from two experimental methods ("bottle" versus "beam").
 * Proton decay and spin crisis: Is the proton fundamentally stable? Or does it decay with a finite lifetime as predicted by some extensions to the standard model? How do the quarks and gluons carry the spin of protons?
 * Grand Unification: Are the electromagnetic and nuclear forces different aspects of a Grand Unified Theory? If so, what symmetry governs this force and its behaviours?
 * Supersymmetry: Is spacetime supersymmetry realized at TeV scale? If so, what is the mechanism of supersymmetry breaking? Does supersymmetry stabilize the electroweak scale, preventing high quantum corrections? Does the lightest supersymmetric particle (LSP) comprise dark matter?
 * Color confinement: The quantum chromodynamics (QCD) color confinement conjecture is that color-charged particles (such as quarks and gluons) cannot be separated from their parent hadron without producing new hadrons. Is it possible to provide an analytic proof of color confinement in any non-abelian gauge theory?

 * The QCD vacuum: Many of the equations in non-perturbative QCD are currently unsolved. These energies are the energies sufficient for the formation and description of atomic nuclei. How thus does low energy /non-pertubative QCD give rise to the formation of complex nuclei and nuclear constituents?
 * Generations of matter: Why are there three generations of quarks and leptons? Is there a theory that can explain the masses of particular quarks and leptons in particular generations from first principles (a theory of Yukawa couplings)?
 * Neutrino mass: What is the mass of neutrinos, whether they follow Dirac or Majorana statistics? Is the mass hierarchy normal or inverted? Is the CP violating phase equal to 0?
 * Reactor antineutrino anomaly: There is an anomaly in the existing body of data regarding the antineutrino flux from nuclear reactors around the world. Measured values of this flux appears to be only 94% of the value expected from theory. It is unknown whether this is due to unknown physics (such as sterile neutrinos), experimental error in the measurements, or errors in the theoretical flux calculations.
 * Strong CP problem and axions: Why is the strong nuclear interaction invariant to parity and charge conjugation? Is Peccei–Quinn theory the solution to this problem? Could axions be the main component of dark matter?
 * Anomalous magnetic dipole moment: Why is the experimentally measured value of the muon's anomalous magnetic dipole moment ("muon $g$ − 2") significantly different from the theoretically predicted value of that physical constant?
 * Proton radius puzzle: What is the electric charge radius of the proton? How does it differ from a gluonic charge?
 * Pentaquarks and other exotic hadrons: What combinations of quarks are possible? Why were pentaquarks so difficult to discover? Are they a tightly bound system of five elementary particles, or a more weakly-bound pairing of a baryon and a meson?
 * Mu problem: A problem in supersymmetric theories, concerned with understanding the reasons for parameter values of the theory.
 * Koide formula: An aspect of the problem of particle generations. The sum of the masses of the three charged leptons, divided by the square of the sum of the roots of these masses, to within one standard deviation of observations, is $$. It is unknown how such a simple value comes about, and why it is the exact arithmetic average of the possible extreme values of $g$ (equal masses) and 1 (one mass dominates).
 * Strange Matter: Does Strange Matter exist? Is it stable? Can they form Strange Stars? Is strange matter stable at 0 pressure (i.e in the vacuum)?
 * Glueballs: Do they exist in nature?
 * The gallium anomaly: The measurements of the charged-current capture rate of neutrinos on Ga from strong radioactive sources have yielded results below those expected, based on the known strength of the principal transition supplemented by theory.

Astronomy and astrophysics

 * Solar cycle: How does the Sun generate its periodically reversing large-scale magnetic field? How do other solar-like stars generate their magnetic fields, and what are the similarities and differences between stellar activity cycles and that of the Sun? What caused the Maunder Minimum and other grand minima, and how does the solar cycle recover from a minima state?
 * Coronal heating problem: Why is the Sun's corona (atmosphere layer) so much hotter than the Sun's surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models?
 * Astrophysical jet: Why do only certain accretion discs surrounding certain astronomical objects emit relativistic jets along their polar axes? Why are there quasi-periodic oscillations in many accretion discs? Why does the period of these oscillations scale as the inverse of the mass of the central object? Why are there sometimes overtones, and why do these appear at different frequency ratios in different objects?
 * Diffuse interstellar bands: What is responsible for the numerous interstellar absorption lines detected in astronomical spectra? Are they molecular in origin, and if so which molecules are responsible for them? How do they form?
 * Supermassive black holes: What is the origin of the M–sigma relation between supermassive black hole mass and galaxy velocity dispersion? How did the most distant quasars grow their supermassive black holes up to 10$1⁄3$ solar masses so early in the history of the universe?
 * Kuiper cliff: Why does the number of objects in the Solar System's Kuiper belt fall off rapidly and unexpectedly beyond a radius of 50 astronomical units?
 * Flyby anomaly: Why is the observed energy of satellites flying by planetary bodies sometimes different by a minute amount from the value predicted by theory?
 * Galaxy rotation problem: Is dark matter responsible for differences in observed and theoretical speed of stars revolving around the centre of galaxies, or is it something else? GalacticRotation2.svg
 * Supernovae: What is the exact mechanism by which an implosion of a dying star becomes an explosion?
 * p-nuclei: What astrophysical process is responsible for the nucleogenesis of these rare isotopes?
 * Ultra-high-energy cosmic ray: Why is it that some cosmic rays appear to possess energies that are impossibly high, given that there are no sufficiently energetic cosmic ray sources near the Earth? Why is it that (apparently) some cosmic rays emitted by distant sources have energies above the Greisen–Zatsepin–Kuzmin limit?
 * Rotation rate of Saturn: Why does the magnetosphere of Saturn exhibit a (slowly changing) periodicity close to that at which the planet's clouds rotate? What is the true rotation rate of Saturn's deep interior?
 * Origin of magnetar magnetic field: What is the origin of magnetar magnetic field?
 * Large-scale anisotropy: Is the universe at very large scales anisotropic, making the cosmological principle an invalid assumption? The number count and intensity dipole anisotropy in radio, NRAO VLA Sky Survey (NVSS) catalogue is inconsistent with the local motion as derived from cosmic microwave background and indicate an intrinsic dipole anisotropy. The same NVSS radio data also shows an intrinsic dipole in polarization density and degree of polarization in the same direction as in number count and intensity. There are several other observations revealing large-scale anisotropy. The optical polarization from quasars shows polarization alignment over a very large scale of Gpc.   The cosmic-microwave-background data shows several features of anisotropy,    which are not consistent with the Big Bang model.
 * Age–metallicity relation in the Galactic disk: Is there a universal age–metallicity relation (AMR) in the Galactic disk (both "thin" and "thick" parts of the disk)? Although in the local (primarily thin) disk of the Milky Way there is no evidence of a strong AMR, a sample of 229 nearby "thick" disk stars has been used to investigate the existence of an age–metallicity relation in the Galactic thick disk, and indicate that there is an age–metallicity relation present in the thick disk. Stellar ages from asteroseismology confirm the lack of any strong age–metallicity relation in the Galactic disc.
 * The lithium problem: Why is there a discrepancy between the amount of lithium-7 predicted to be produced in Big Bang nucleosynthesis and the amount observed in very old stars?
 * Ultraluminous X-ray sources (ULXs): What powers X-ray sources that are not associated with active galactic nuclei but exceed the Eddington limit of a neutron star or stellar black hole? Are they due to intermediate-mass black holes? Some ULXs are periodic, suggesting non-isotropic emission from a neutron star. Does this apply to all ULXs? How could such a system form and remain stable?
 * Fast radio bursts (FRBs): What causes these transient radio pulses from distant galaxies, lasting only a few milliseconds each? Why do some FRBs repeat at unpredictable intervals, but most do not? Dozens of models have been proposed, but none have been widely accepted.

Nuclear physics

 * Quantum chromodynamics: What are the phases of strongly interacting matter, and what roles do they play in the evolution of the cosmos? What is the detailed partonic structure of the nucleons? What does QCD predict for the properties of strongly interacting matter? What determines the key features of QCD, and what is their relation to the nature of gravity and spacetime? Does QCD truly lack CP violations?
 * Quark–gluon plasma: Where is the onset of deconfinement: 1) as a function of temperature and chemical potentials? 2) as a function of relativistic heavy-ion collision energy and system size? What is the mechanism of energy and baryon-number stopping leading to creation of quark-gluon plasma in relativistic heavy-ion collisions? Why is sudden hadronization and the statistical-hadronization model a near-to-perfect description of hadron production from quark–gluon plasma? Is quark flavor conserved in quark–gluon plasma? Are strangeness and charm in chemical equilibrium in quark–gluon plasma? Does strangeness in quark–gluon plasma flow at the same speed as up and down quark flavours? Why does deconfined matter show ideal flow?
 * Specific models of quark–gluon plasma formation: Do gluons saturate when their occupation number is large? Do gluons form a dense system called colour glass condensate? What are the signatures and evidences for the Balitsky–Fadin–Kuarev–Lipatov, Balitsky–Kovchegov, Catani–Ciafaloni–Fiorani–Marchesini evolution equations?
 * Nuclei and nuclear astrophysics: Why is there a lack of convergence in estimates of the mean lifetime of a free neutron based on two separate—and increasingly precise—experimental methods? What is the nature of the nuclear force that binds protons and neutrons into stable nuclei and rare isotopes? What is the explanation for the EMC effect? What is the nature of exotic excitations in nuclei at the frontiers of stability and their role in stellar processes? What is the nature of neutron stars and dense nuclear matter? What is the origin of the elements in the cosmos? What are the nuclear reactions that drive stars and stellar explosions? What is the heaviest possible chemical element?

Fluid dynamics

 * Under what conditions do smooth solutions exist for the Navier–Stokes equations, which are the equations that describe the flow of a viscous fluid? This problem, for an incompressible fluid in three dimensions, is also one of the Millennium Prize Problems in mathematics.
 * Turbulent flow: Is it possible to make a theoretical model to describe the statistics of a turbulent flow (in particular, its internal structures)?
 * Granular convection: why does a granular material subjected to shaking or vibration exhibit circulation patterns similar to types of fluid convection? Why do the largest particles end up on the surface of a granular material containing a mixture of variously sized objects when subjected to a vibration/shaking?

Condensed matter physics

 * Bose–Einstein condensation: How do we rigorously prove the existence of Bose–Einstein condensates for general interacting systems?
 * High-temperature superconductors: What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvins? Is it possible to make a material that is a superconductor at room temperature and atmospheric pressure?
 * Amorphous solids: What is the nature of the glass transition between a fluid or regular solid and a glassy phase? What are the physical processes giving rise to the general properties of glasses and the glass transition?
 * Universality of low-temperature amorphous solids: why is the small dimensionless ratio of the phonon wavelength to its mean free path nearly the same for a very large family of disordered solids? This small ratio is observed for very large range of phonon frequencies.
 * Cryogenic electron emission: Why does the electron emission in the absence of light increase as the temperature of a photomultiplier is decreased?
 * Sonoluminescence: What causes the emission of short bursts of light from imploding bubbles in a liquid when excited by sound?
 * Topological order: Is topological order stable at non-zero temperature? Equivalently, is it possible to have three-dimensional self-correcting quantum memory?
 * Gauge block wringing: What mechanism allows gauge blocks to be wrung together?
 * Fractional Hall effect: What mechanism explains the existence of the u = 5/2 state in the fractional quantum Hall effect? Does it describe quasiparticles with non-Abelian fractional statistics?
 * Liquid crystals: Can the nematic to smectic (A) phase transition in liquid crystal states be characterized as a universal phase transition?
 * Semiconductor nanocrystals: What is the cause of the nonparabolicity of the energy-size dependence for the lowest optical absorption transition of quantum dots?
 * Metal whiskering: In electrical devices, some metallic surfaces may spontaneously grow fine metallic whiskers, which can lead to equipment failures. While compressive mechanical stress is known to encourage whisker formation, the growth mechanism has yet to be determined.
 * Superfluid transition in helium-4: Explain the discrepancy between the experimental and theoretical  determinations of the heat capacity critical exponent $α$.
 * Scharnhorst effect: Can light signals travel slightly faster than c between two closely spaced conducting plates, exploiting the Casimir effect?

Quantum computing and quantum information

 * Threshold problem: Can we go beyond the noisy intermediate-scale quantum era? Can quantum computers reach fault tolerance? Is it possible to have enough qubit scalability to implement quantum error correction? What is the most promising candidate platforms to physically implement qubits?
 * Topological qubits: Topological quantum computers are promising but can they be built? Can we demonstrate Majorana zero modes conclusively?
 * Temperature: Can quantum computing be performed at non-cryogenic temperatures? Can we build room temperature quantum computers?
 * Complexity classes problems: What is the relation of BQP and BPP? What is the relation between BQP and NP? Can computation in plausible physical theories (quantum algorithms) go beyond BQP?
 * Post-quantum cryptography: Can we prove that some cryptographic protocols are safe against quantum computers?
 * Quantum capacity: The capacity of a quantum channel is in general not known.

Plasma physics

 * Plasma physics and fusion power: Fusion energy may potentially provide power from an abundant resource (e.g. hydrogen) without the type of radioactive waste that fission energy currently produces. However, can ionized gases (plasma) be confined long enough and at a high enough temperature to create fusion power? What is the physical origin of H-mode?
 * The injection problem: Fermi acceleration is thought to be the primary mechanism that accelerates astrophysical particles to high energy. However, it is unclear what mechanism causes those particles to initially have energies high enough for Fermi acceleration to work on them.
 * Alfvénic turbulence: In the solar wind and the turbulence in solar flares, coronal mass ejections, and magnetospheric substorms are major unsolved problems in space plasma physics.

Biophysics

 * Stochasticity and robustness to noise in gene expression: How do genes govern our body, withstanding different external pressures and internal stochasticity? Certain models exist for genetic processes, but we are far from understanding the whole picture, in particular in development where gene expression must be tightly regulated.
 * Quantitative study of the immune system: What are the quantitative properties of immune responses? What are the basic building blocks of immune system networks?
 * Homochirality: What is the origin of the preponderance of specific enantiomers in biochemical systems?
 * Magnetoreception: How do animals (e.g. migratory birds) sense the Earth's magnetic field?
 * Protein structure prediction: How is the three-dimensional structure of proteins determined by the one-dimensional amino acid sequence? How can proteins fold on microsecond to second timescales when the number of possible conformations is astronomical and conformational transitions occur on the picosecond to microsecond timescale? Can algorithms be written to predict a protein's three-dimensional structure from its sequence? Do the native structures of most naturally occurring proteins coincide with the global minimum of the free energy in conformational space? Or are most native conformations thermodynamically unstable, but kinetically trapped in metastable states? What keeps the high density of proteins present inside cells from precipitating?
 * Quantum biology: Can coherence be maintained in biological systems at timeframes long enough to be functionally important? Are there non-trivial aspects of biology or biochemistry that can only be explained by the persistence of coherence as a mechanism?

Foundations of physics

 * Interpretation of quantum mechanics: How does the quantum description of reality, which includes elements such as the superposition of states and wavefunction collapse or quantum decoherence, give rise to the reality we perceive? Another way of stating this question regards the measurement problem: What constitutes a "measurement" which apparently causes the wave function to collapse into a definite state? Unlike classical physical processes, some quantum mechanical processes (such as quantum teleportation arising from quantum entanglement) cannot be simultaneously "local", "causal", and "real", but it is not obvious which of these properties must be sacrificed, or if an attempt to describe quantum mechanical processes in these senses is a category error such that a proper understanding of quantum mechanics would render the question meaningless. Can the many worlds interpretation resolve it?
 * Arrow of time (e.g. entropy's arrow of time): Why does time have a direction? Why did the universe have such low entropy in the past, and time correlates with the universal (but not local) increase in entropy, from the past and to the future, according to the second law of thermodynamics? Why are CP violations observed in certain weak force decays, but not elsewhere? Are CP violations somehow a product of the second law of thermodynamics, or are they a separate arrow of time? Are there exceptions to the principle of causality? Is there a single possible past? Is the present moment physically distinct from the past and future, or is it merely an emergent property of consciousness? What links the quantum arrow of time to the thermodynamic arrow?
 * Locality: Are there non-local phenomena in quantum physics? If they exist, are non-local phenomena limited to the entanglement revealed in the violations of the Bell inequalities, or can information and conserved quantities also move in a non-local way? Under what circumstances are non-local phenomena observed? What does the existence or absence of non-local phenomena imply about the fundamental structure of spacetime? How does this elucidate the proper interpretation of the fundamental nature of quantum physics?
 * Quantum mind: Do quantum mechanical phenomena, such as entanglement and superposition, play an important part in the brain's function and can it explain critical aspects of consciousness?

General physics/quantum physics

 * Perform a loophole-free Bell test experiment (1970 –2015): In October 2015, scientists from the Kavli Institute of Nanoscience reported that the failure of the local hidden-variable hypothesis is supported at the 96% confidence level based on a "loophole-free Bell test" study. These results were confirmed by two studies with statistical significance over 5 standard deviations which were published in December 2015.
 * Create Bose–Einstein condensate (1924 –1995): Composite bosons in the form of dilute atomic vapours were cooled to quantum degeneracy using the techniques of laser cooling and evaporative cooling.

Cosmology and general relativity

 * Existence of gravitational waves (1916–2016): On 11 February 2016, the Advanced LIGO team announced that they had directly detected gravitational waves from a pair of black holes merging,  which was also the first detection of a stellar binary black hole.
 * Numerical solution for binary black hole (1960s–2005): The numerical solution of the two body problem in general relativity was achieved after four decades of research. Three groups devised the breakthrough techniques in 2005 (annus mirabilis of numerical relativity).
 * Cosmic age problem (1920s–1990s): The estimated age of the universe was around 3 to 8 billion years younger than estimates of the ages of the oldest stars in the Milky Way. Better estimates for the distances to the stars, and the recognition of the accelerating expansion of the universe, reconciled the age estimates.

High-energy physics/particle physics

 * Existence of pentaquarks (1964–2015): In July 2015, the LHCb collaboration at CERN identified pentaquarks in the Λ$10$→J/ψK$0 b$p channel, which represents the decay of the bottom lambda baryon (Λ$−$) into a J/ψ meson (J/ψ), a kaon (K$0 b$) and a proton (p). The results showed that sometimes, instead of decaying directly into mesons and baryons, the Λ$−$ decayed via intermediate pentaquark states. The two states, named P$0 b$(4380) and P$+ c$(4450), had individual statistical significances of 9 σ and 12 σ, respectively, and a combined significance of 15 σ—enough to claim a formal discovery. The two pentaquark states were both observed decaying strongly to J/ψp, hence must have a valence quark content of two up quarks, a down quark, a charm quark, and an anti-charm quark (up quarkup quarkdown quarkcharm quarkcharm antiquark), making them charmonium-pentaquarks.
 * Existence of quark-gluon plasma, a new phase of matter was discovered and confirmed in experiments at CERN-SPS (2000), BNL-RHIC (2005) and CERN-LHC (2010).
 * Higgs boson and electroweak symmetry breaking (1963 –2012): The mechanism responsible for breaking the electroweak gauge symmetry, giving mass to the W and Z bosons, was solved with the discovery of the Higgs boson of the Standard Model, with the expected couplings to the weak bosons. No evidence of a strong dynamics solution, as proposed by technicolor, has been observed.
 * Origin of mass of most elementary particles: Solved with the discovery of the Higgs boson, which implies the existence of the Higgs field giving mass to these particles.

Astronomy and astrophysics

 * Origin of short gamma-ray burst (1993 –2017): From binary neutron stars merger, produce a kilonova explosion and short gamma-ray burst GRB 170817A was detected in both electromagnetic waves and gravitational wave GW170817.
 * Missing baryon problem (1998 –2017): proclaimed solved in October 2017, with the missing baryons located in hot intergalactic gas.
 * Long-duration gamma-ray bursts (1993 –2003): Long-duration bursts are associated with the deaths of massive stars in a specific kind of supernova-like event commonly referred to as a collapsar. However, there are also long-duration GRBs that show evidence against an associated supernova, such as the Swift event GRB 060614.
 * Solar neutrino problem (1968 –2001): Solved by a new understanding of neutrino physics, requiring a modification of the Standard Model of particle physics—specifically, neutrino oscillation.
 * Saturn's core spin was determined from its gravitational field.

Nuclear physics

 * Hagedorn temperature recognized as phase transformation temperature between hadronic confined phase and deconfined phase of matter.

Rapidly solved problems

 * Existence of time crystals (2012–2016): The idea of a quantized time crystal was first theorized in 2012 by Frank Wilczek. In 2016, Khemani et al. and Else et al. independently of each other suggested that periodically driven quantum spin systems could show similar behaviour. Also in 2016, Norman Yao at Berkeley and colleagues proposed a different way to create discrete time crystals in spin systems. This was then used by two teams, a group led by Christopher Monroe at the University of Maryland and a group led by Mikhail Lukin at Harvard University, who were both able to show evidence for time crystals in the laboratory setting, showing that for short times the systems exhibited the dynamics similar to the predicted one.
 * Photon underproduction crisis (2014–2015): This problem was resolved by Khaire and Srianand. They show that a factor 2 to 5 times large metagalactic photoionization rate can be easily obtained using updated quasar and galaxy observations. Recent observations of quasars indicate that the quasar contribution to ultraviolet photons is a factor of 2 larger than previous estimates. The revised galaxy contribution is a factor of 3 larger. These together solve the crisis.
 * Hipparcos anomaly (1997 –2012): The High Precision Parallax Collecting Satellite (Hipparcos) measured the parallax of the Pleiades and determined a distance of 385 light years. This was significantly different from other measurements made by means of actual to apparent brightness measurement or absolute magnitude. The anomaly was due to the use of a weighted mean when there is a correlation between distances and distance errors for stars in clusters. It is resolved by using an unweighted mean. There is no systematic bias in the Hipparcos data when it comes to star clusters.
 * Faster-than-light neutrino anomaly (2011–2012): In 2011, the OPERA experiment mistakenly observed neutrinos appearing to travel faster than light. On 12 July 2012 OPERA updated their paper after discovering an error in their previous flight time measurement. They found agreement of neutrino speed with the speed of light.
 * Pioneer anomaly (1980–2012): There was a deviation in the predicted accelerations of the Pioneer 10 and 11 spacecraft as they left the Solar System. It is believed that this is a result of previously unaccounted-for thermal recoil force.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: List of unsolved problems in physics