Talk:Dark matter/Archive 6

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"In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly seen with telescopes."

"It is common when discussing the Invisible Pink Unicorn to point out that because she is invisible, no one can prove that she does not exist (or indeed that she is not pink)."

Dark Matter has a great deal in common with

The

Read the section of the article that summarizes the observational evidence for the existence of dark matter. This is unlike the absence of evidence for unicorns, UFOs and Bigfoot. Furthermore, it's silly to try to lump together the scientists who believe in dark matter with people who believe in unicorns, UFOs or Bigfoot. And by the way, dark matter is not dark energy; dark matter was not invented to explain the (accelerating) expansion of the universe. (Or, to be more precise, to explain the recent observations of the red shift of distant supernovae for which accelerating expansion is the mainstream interpretation.) The phlogiston analogy is much better since phlogiston was a scientific attempt to explain observations. Just as phlogiston theory was rejected after the development of a theory more consistent with observations, dark matter may someday be rejected too, since much of science (unlike religion) attempts to prove that theories are wrong. SEppley (talk) 16:22, 19 February 2012 (UTC)

I'm hoping someone will add a section to the article to explain the shape that's been estimated for a galaxy's dark matter halo: roughly spherical, and slightly larger than the galaxy. That shape differs from the shape formed by a galaxy's stars: disk, ellipse, etc. As I understand it, the evolution into disks and ellipses can be explained by computer simulations involving gravitational attraction and net angular momentum. Do there exist computer simulations that explain the evolution of dark matter into a roughly spherical structure? Does the spherical shape imply a galaxy's dark matter collectively has little or no net angular momentum? If so, what keeps the spherical structure from collapsing due to gravitational attraction? I would suspect it avoids collapse thanks to kinetic energy; in other words, that each dark matter particle travels in a comet-like orbit around the galactic center (with occasional orbital perturbations when they pass near massive objects). But could some repulsive force be what prevents collapse?

In the M-brane or "multiverse" alternative, in which dark matter is actually ordinary matter that resides in what might be called nearby parallel universes that can only interact with our universe gravitationally, how is the roughly spherical shape explained? By a multitude of parallel disk-shaped galaxies that have similar locations of their centers but random axes of rotation? SEppley (talk) 14:49, 19 February 2012 (UTC)

Hi SEppley,

Your excellent questions might be better addressed in an online physics forum. This talk page, and all article talk pages, are intended to be about content of the article. While suggesting specific additional content can lead to an improved article, talk pages are not the appropriate place for general inquiries about additional content. In brief reply, the shape of dark matter halos remains an active area of research, and rather little is known about the formation and maintenance of halo shape. The current state of knowledge is (in my opinion) too speculative to warrant inclusion in an encyclopedic entry. See

Navarro-Frenk-White profile

and references therein to read more about this topic.

Cheers, Jj1236 (talk) 22:02, 20 February 2012 (UTC)

I've made very intelligent changes to wikipedia in the past but they've been taken down so I can only suggest the change at this point because making the change will only waste my time and whoever changes it back without thinking. The opening paragraph states "neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly seen with telescopes." I believe this is error... It's not an error in fact but rather an error in wording according to Hubble telescope readings. Dark Matter "distorts light" before it reaches earth. I believe a scatter of light is a distortion. Claiming that it doesn't scatter light leads one to believe that it is only theoretical and cannot be measured. Can we change this article so it more reflects an accurate statement about how it alters light? This general article should be helpful. http://www.sciencenews.org/view/generic/id/338987/title/Galactic_smashup_leaves_dark_matter_debris — Preceding unsigned comment added by Cyberclops (talk • contribs) 00:10, 7 March 2012 (UTC)

• Certainly gravitational microlensing is a distortion of line-of-sight light. Npmay (talk) 02:45, 7 March 2012 (UTC)
• Dark matter affects light through gravity, yes. I'll try to re-word that to make it more clear. Waleswatcher (talk) 04:45, 7 March 2012 (UTC)

A more accurate phrasing would be "dark matter does not interact via the electromagnetic force". In the interests of making the article more accessible, the lede spells out what that means (does not absorb or scatter light via photon/dark matter interactions), rather than leaving it at "does not interact via EM or have charge under EM".

As this is your first edit to the dark matter article, the edits were presumably made elsewhere. --Christopher Thomas (talk) 04:48, 7 March 2012 (UTC)

The articles on Cold dark matter, Warm dark matter, and Hot dark matter are stubs which duplicate content in this article. I'm wondering if they should be merged into this article. --Chetvorno^TALK 15:44, 29 March 2012 (UTC)

Probably. Mixed dark matter is another one. 71.215.74.243 (talk) 22:03, 2 April 2012 (UTC)

An old model of the univers applied in a new form indicates that there are over 200 dark matter particals of half the number of diferent masses. it also gave a starting point in calculating the diferent masses.the model also gives a number of interesting definitions for other things — Preceding unsigned comment added by 81.141.114.141 (talk) 19:31, 7 May 2012 (UTC)

Unless it has been published in respected science journals, I'm afraid it's too early to include it in Wikipedia.

WP:RS describes the type of reference material that Wikipedia articles are based on. --Christopher Thomas (talk

) 00:16, 8 May 2012 (UTC)

LSG gravity replaces Dark Matter. MOG, a variation of General Relativity fits data better than any other theory. MOG replaces Dark Matter. You may find the theory (LSG) in a paper "Time and its Properties". The formula for LSG is C*Ng, where Ng is Neutonian gravity and C a multiplier which is a function of distance and perpendicular velocity to the line of sight plus other lesser factors. C's values are 10 - 8 between the centers of galaxies and greater, 2.25 - 1.75 betweeen the certer of a galaxy and any star and between 1.0 and 1.05 between a star and any near by body. C is an inverse function to the magnitude of the cross velocity. This than explains, with C going from 1 to 10, the following. I. Our solar system where everything is C = 1 because the cross velocities are too great, except comets and the spacecraft (Pioneer Anomaly). II. The velocities of stars in spiral galaxies, C = 2. III. This explains 1) warped spiral galaxies, all. 2) The arms , but mostly the bars in Barred Galaxies. IV. The force between galaxies where C = 9. Here in all cases the extra force above Neutonian is only from the center of galaxies, not any where as Dark Matter. — Preceding unsigned comment added by 68.59.150.181 (talk) on 12:56, 26 May 2012 (UTC)

A clear reference required section. Mtpaley (talk) 23:10, 27 May 2012 (UTC)

"plus other lesser factors" - give us some details. I want to calculate the effects of this theory on planetary orbits. Mtpaley (talk) 23:14, 27 May 2012 (UTC)

Per

Years ago i wrote in here about my theories on dark matter and galactic anomalies. No one took me seriously unfortunately, maybe it was my massive run on sentence...either way its absolutely apparent that dark matter is the core of singularities. It plays a special relationship with dark energy as dark energy is the gravitational pull of singularities. Something very interesting to think about is the nature of absolute zero in all of this. Absolute zero proves the existence of the big bang theory as the only way to obtain a temperature of absolute zero is by removing all matter from an area, thereby making that areas gravitational pull zero. You must understand the nature of light is its attraction to gravity and it being a form of energy radiates heat thereby igniting the fundamentals of nature. — Preceding unsigned comment added by Uberbunk0439 (talk • contribs) 06:00, 18 June 2012 (UTC)

Per

WP:N). --Christopher Thomas (talk

) 06:12, 18 June 2012 (UTC)

The article currently gives priority to Jan Oort for discovering dark matter in 1932. This is problematic at the least. Oort's results were thrown off by including thick-disk K giant stars in his perpendicular velocity sample. (See, for example, [1]). It's now understood that there is little if any evidence for dark matter in the galactic disk. We don't usually give primary credit for a discovery that's understood later to be incorrect. Indeed, the article mentioned Zwicky as the first discoverer of dark matter until Oort was added in Feb. 2012 by User:Aarghdvaark ([2] and subsequent edits). Oort played a significant role in developing the idea of dark matter, but his "discovery" was spurious. --Amble (talk) 10:17, 3 July 2012 (UTC)

Thanks for checking on this. I wasn't sure of the details of the history, so I didn't say anything. If want to revert to the previous version, or significantly rework that part, I'll back you up. - Parejkoj (talk) 14:43, 3 July 2012 (UTC)

Ok - I'm not arguing for or against the concept of dark matter. However my understanding is that it is a theory. Granted it's the most commonly accepted theory at this point in time, but it remains a theory does it not? However the article seems significantly biased towards the assumption that the theory is a proven fact ... for example:

"Dark matter came to the attention of astrophysicists due to" (first sentence, second para) which implies that astrophysicists 'found' something rather than observed phenomena and theorized an explanation. Even more so "Though a fourth category had been considered early on, called mixed dark matter, it was quickly eliminated (from the 1990s) since the discovery of dark energy."

I believe that dark energy is another theory, not a proven fact, so it hasn't been discovered ... it's been hypothesized.

I can't do it - I'm not knowledgeable enough in this ... but I really think this article needs to be examined for NPOV by someone who's fully up to speed and can differentiate between most accepted theory and proven fact. 124.168.69.148 (talk) 11:41, 18 April 2012 (UTC)

I think this could be debated, but since it is the only plausible theory to explain observations by far, and has a decent amount of observational evidence, I would fall on the side of keeping it the way it is. Dark energy is another matter, however, I'd suggest taking it up on Talk:Dark energy. -RunningOnBrains^(talk) 17:58, 18 April 2012 (UTC)

Also, you are making a distinction between "most-accepted theory" and "proven fact", when, in reality, no "fact" is ever "proven" in science. Every experiment and observation gathers more evidence until it becomes exceedingly unlikely that all previous experiments have been in error, and all other explanations become less and less likely. Surely, some "facts" can be derived from first principles, like the laws of gravitation and such, but that relies on you accepting those laws. You'd be a fool not to, but we will never get a certified letter from the universe saying "This theory is 100% correct". -RunningOnBrains^(talk) 18:03, 18 April 2012 (UTC)

I think we shouldn't discuss scientific theories here, unless as a means to improve the articles. There's nothing such as "proven facts" in science, the scientific counterpart is very well attested theories. That's the optimum. Rursus dixit. (^mbork³!) 05:08, 19 April 2012 (UTC)

Sorry, forgot I wasn't at the

Science Reference Desk for a bit. -RunningOnBrains^(talk

) 15:23, 19 April 2012 (UTC)

This person is absolutely correct. I too am looking at the wording thinking for one part how I failed to understand that dark matter was not an observable phenomenon or even hypothesised to be an observable phenomenon. On the other hand, then, I am reading through and phrases like that, "first came to the attention," and I just want to rip the whole thing up and look for patterns in it. I am not one for poetic literature, but I'm all in for literacy. If anyone is writing this article and wants to impart the knowledge usefully upon the unlearned person, this is what you should look at just as closely or moreso than your galactic halos. ~ R.T.G 16:46, 15 May 2012 (UTC)

In the very first sentence it establishes that the existence of dark matter is a hypothesis, "...dark matter is a type of matter hypothesized to account for a large part of the total mass in the universe". Because this is established, we can now infer: "Dark matter came to the attention of astrophysicists due to discrepancies between the mass of large astronomical objects determined from their gravitational effects, and mass calculated from the "luminous matter" they contain" "Discrepancies between the mass of large astronomical objects and the mass calculated from the 'luminous matter' they contain came to the attention of astrophysicists, and they hypothesised the existence of 'dark matter'..." I realise I've not done a very good job of explaining my point. But what I'm trying to say is, the article doesn't imply that the theory on dark matter is proven, it already explicitly stated that it is a hypothesise. I would assume if someone is reading this article they would be intelligent enough to remember that it's only hypothetical, or does one expect too much? — Preceding unsigned comment added by 90.209.165.17 (talk) 03:17, 16 June 2012 (UTC)

Part of the problem is that this article is woefully lacking in citations. It makes statements like "The full calculations are quite technical, but an approximate dividing line is that "warm" dark matter particles became non-relativistic when the universe was approximately 1 year old and 1 millionth of its present size; the horizon size was then 2 light-years, which would expand to 2 million light years today (if there were no structure formation). ...and then backs that up with NOTHING. No citations at all. No other field of study could get away with this, but apparently astrophysicists do. They should look for more respectable work. 24.165.102.99 (talk) 15:00, 5 July 2012 (UTC)Ubiquitousnewt

I agree with you on the section you pointed out. It needs some heavy editing, as well as citations. However, I don't see any deep connection to the state of the field. This article, like other Wikipedia articles, is edited by volunteers rather than by a paid corps of professional astrophysicists. --Amble (talk) 16:20, 5 July 2012 (UTC)

Is Dark Matter the third type of matter, with matter and anti-matter being the first two? How does Dark Matter interact with matter and anti-matter? What is it composed out of (ex. particles)? P.S. I'm only in Grade 9, k? Not an expert at this stuff yet... — Preceding unsigned comment added by 96.52.41.208 (talk) 03:27, 5 July 2012 (UTC)

The short answer is, "dark matter" is a different type of matter, but still matter. It presumably has its own antimatter counterpart (though some dark matter candidates are their own antiparticle). It does not interact directly with matter or antimatter under most conditions. The best guess at present is that it's a new type of particle (as described in the article).

Further questions about this should go to the

science reference desk page, as this talk page is for discussing changes people want to make to the article, not for discussing dark matter itself. The reference desk should be able to help you with anything else you want to know about the subject. --Christopher Thomas (talk

) 05:32, 5 July 2012 (UTC)

Here a "Serious Blow to Dark Matter Theories" (Journalist inflated), that examines a discrepancy between the Dark Matter expectations on star dynamics and the conditions in the neighborhood of the Sun (out to 13,000 ly away). Rursus dixit. (^mbork³!) 04:57, 19 April 2012 (UTC)

News article

Why is there no mentioning on the dark matter page of the fact that very recently (the last 1-6 months!), the very existence of dark matter has been called into question. The statement that dark matter is 'generally accepted by the scientific community' is no longer valid. — Preceding

The study behind these news articles seems to be Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood, a study of the dynamics of about 400 mstars in the neighbourhood of the Sun by a team of Chilean astronomers. It may merit a brief note in the body of the article, but is not significant enough to be mentioned in the lead. Gandalf61 (talk) 11:33, 6 May 2012 (UTC)

The above study has been disputed by Bovy and Tremaine who claim that one of the key assumptions in the reference above is not applicable in a realistic Galaxy model. Bovy and Tremaine's re-analysis is consistent with conventional estimates of the local dark matter density, ~ 0.3 GeV /cm^3 . Wjs64 (talk) 22:50, 19 July 2012 (UTC)

People do not actually know anything about dark matter and in the interests of academic development and Wikipedias guidelines this should be made quite clear in this article. Currently it as been written to suggest that dark matter is a blob in the sky we've been watching and do not yet understand. That is deceptive. We do not understand it, but that is because we do not know anything about it. There were discrepancies in the calculations of gravity and motion similar to a denser universe. The exact increase in density was calculated. That's as far as they've got so far. I've made a small edit to the lead section and it could probably be written better but the approach needs to be taken. Dark matter is a total unkown hypothesis, not something you can say your telescopes are missing. You could say your microscopes are missing it too. I hope this makes sense... ~ R.T.G 16:27, 15 May 2012 (UTC)

I could say I haven't heard it on a microphone either... it's just a relevant to anything else about dark matter. It shouldn't really be overly suggested that it is anything more than a discrepancy in the the calculation of gravity in the universe. I mean, when it says that dark matter is not known to emit or absorb light, it's more informative to say, dark matter is not known, and though efforts have been made to detect its absorbtion or emission of light, nothing relevant has been found. Is this unfair? ~ R.T.G 16:35, 15 May 2012 (UTC)

First, it's simply not correct to say that "people do not actually know anything about dark matter" or "dark matter is a total unknown hypothesis." We have a number of observable data from different eras and length scales (the facts) and we understand those facts in the light of what we know about physics (the theory). The article describes the observable evidence we do have, the understanding we can draw from it, and the many open questions. If it said as you say "we do not know anything about it", it would be as wrong as if the article on Julius Caesar said that we don't know anything about him because none of us has met him in person. Secondly: you say that "it [h]as been written to suggest that dark matter is a blob in the sky we've been watching and do not yet understand." I'm having a hard time finding what in the article might suggest this. As I read it, it very clearly says the opposite: "[...] and so cannot be seen directly with telescopes." Could you be more specific? --Amble (talk) 19:36, 15 May 2012 (UTC)

From the article: "As important as dark matter is thought to be in the cosmos, direct evidence of its existence and a concrete understanding of its nature have remained elusive." No kidding. Dark matter is dark and can't be detected by any instruments known to science, as far as I know. So how do we know it exists? It was inferred by Zwicky when he concluded "that there must be some non-visible form of matter which would provide enough of the mass and gravity to hold the cluster together." Honestly, it sounds to me like cosmologists have reached a point where they might as well be discussing how many angels can stand on the head of a pin. Johnnyc (talk) 21:29, 15 May 2012 (UTC)

You quote a sentence from the article. It seems to be correct, well supported, and written appropriately. Is there something you propose to change? As for cosmologists, they have to make do with the facts we have. That's what makes science hard. --Amble (talk) 00:29, 16 May 2012 (UTC)

It seems that dark matter is a category of spatial disturbance, to which any indeterminable cause is assigned. What it is in substance cannot be described with any certainty. It's not a finding. The article says some similar things, but without any implications. It implies the reverse many more times. Is it better to change that or to wait until the majority of studies go out of their way to imply it first? I don't think they will, but I still think it's important in the description. ~ R.T.G 23:45, 20 May 2012 (UTC)

The purpose of this Wikipedia article is to report what literature meeting

WP:RS), point to sources and explain how. More extended discussion or debate belongs on a science forum. --Christopher Thomas (talk

) 00:27, 21 May 2012 (UTC)

RTG, could you point out specifically where you think the article says or implies something that's not correct? --Amble (talk) 04:02, 21 May 2012 (UTC)

• "dark matter neither emits nor absorbs light." Well, there is no way to tell, and I can't see why that point shouldn't be made at the beginning where it counts. On another article if an editor said, well it really can't be anything else people can think of, you'd fob them off, especially if people could think of other things.
• "seen directly with telescopes" People search for it with telescopes. It's a little different from not being able to see it. There's no point of me to come up with another theory, it just isn't tangible and particularly the word "directly".
• "came to the attention of," No.
• "observations have indicated the presence of dark matter," No... They have indicated an indeterminate presence. Hypotheses indicate the presence of dark matter. That may seem like a long way around, but isn't it deduction in a large part? Then there is not enough weight to that fact and here is an opportunity.
• "According to consensus,"
• "a new, not yet characterised" I'll not rattle on about these last two except to say that if the approach was considered as I, and I think some others occasionally, are trying to suggest these statements might be worded a little differently.

It's not a challenge of the theories I am trying, it's all very interesting I think, but it's not portrayed very carefully in some respect in the lead and the overview. Here are some quotes from the article which I think are under water, "Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics." ""Cold" dark matter is dark matter composed of [electromag stuff]... ...This is currently the area of greatest interest for dark matter research," "Possibilities range from large objects like MACHOs (such as black holes[67]) or RAMBOs, to new particles like WIMPs and axions. Possibilities involving normal baryonic matter include brown dwarfs or perhaps small, dense chunks of heavy elements." and to reword another sentence, "There is no concrete understanding of dark matter," and so on. It's not a matter of giving exposure to unregarded theories, more about exposure to the mysterious and wide ranging nature of the subject. ~ R.T.G 12:54, 21 May 2012 (UTC)

You've got a long list there, and frankly I can't understand what you are objecting to with any of them. I'll just take the first:"dark matter neither emits nor absorbs light." Well, there is no way to tell - of course there is a way to tell. If dark matter did either, it would be detected with telescopes. Waleswatcher (talk) 18:42, 21 May 2012 (UTC)

• • Point: There's something big up there swishing all the gravity around, but what else it is or does, such as absorbing and emitting light, nobody actually knows. They take an assumption and work from there. An assumption is relevant information. It is in fact key and in that respect should be clear point by point in, at least, the lead and probably the overview as well. It should not be impossible.
  • I don't propose to disagree with that particular assumption, the radiation, not on the article anyway, but only to make it more apparent where we don't know, that we don't know, that an assumption has been made. Personally, it's nonsensical to assume absolutely that no raditation interactions can occur in dark or any other kind of matter. You'd be an eejit if you were trying to find some in that case wouldn't you?
  • If you don't point out the assumptions that a theory is relying on, why should I know there were assumptions to begin with? Should I be firmly aware of the assumptions to understand? Anyway, it wouldn't do to go through the whole article piece by piece noting every little thing as unproven, but it would do in the lead to point out how unproven and changing the theories of dark matter are. Recently it was decided that most of the dark matter supposed to be in the Milky Way would in fact now be baryonic, detectable, matter. There is a major principle of uncertainty and it's not a misinformative aspect. I'm just yakking on about it now but I've conveyed nothing I guess I am doing it wrong. ~ R.T.G 22:34, 21 May 2012 (UTC)

Again, I'm not sure what you're trying to say. You're right that dark matter could interact very weakly with light, but no one assumes otherwise - they just use the data to constrain how strong the interactions (emission and absorption and scattering) can possibly be, and the data shows they have to be very, very weak. As for what we don't know for sure, we don't know anything for sure. We don't know electrons exist. That's the essence of science - all you can do is formulate hypotheses and test them against data. If they hold up, it doesn't mean they're right, but at least they passed some tests. Getting back to this article - why don't you pick one specific passage you object to, and propose alternate language of your own? Remember, wiki articles need to be neutral and reliably sourced. Waleswatcher (talk) 14:55, 22 May 2012 (UTC)

From

energy potential. Theories regarding dark matter are of particuar interest in the study of astronomy, cosmology, and particle physics." Something like that? And a bit more then of course. ~ R.T.G

20:42, 22 May 2012 (UTC)

You seem to be objecting to content on a different page (Dark matter (disambiguation)). THis talk page isn't the right place to discuss that. Can you find something in this article you object to, and if so, can you suggest a change? Waleswatcher (talk) 01:36, 23 May 2012 (UTC)

I am suggesting that the passage from there, is more suitable for the page here... and so on. ~ R.T.G 08:29, 23 May 2012 (UTC)

I am suggesting to start changing the lead area on this page with that stuff there. ~ R.T.G 08:31, 23 May 2012 (UTC)

What is it about the lead of this article that you don't like? It states in the first sentence that DM is a "currently unknown type of matter hypothesized to account for a large part of the total mass in the universe." Perhaps not ideal phrasing, but it makes it clear that it isn't know what DM is, or even if it exists. The phrase "theoretical matter" in your proposed wording doesn't make sense - presumably you mean "hypothesized", but that's already in the current wording. Waleswatcher (talk) 13:34, 23 May 2012 (UTC)

I made some minor changes to the first paragraph of the lead, and added a sentence: Instead, its existence and properties are inferred from its gravitational effects on visible matter, radiation, and the large scale structure of the universe. Waleswatcher (talk) 13:44, 23 May 2012 (UTC)

I could go on to say about the emitting light quote, if it were fair to say that dark matter is detectable by studying celestial gravity, then dark matter can only be detected using a telescope rather than cannot, etc, blah :). ~ R.T.G 20:48, 22 May 2012 (UTC)

Calling dark matter "theoretical matter" would be inaccurate. Dark matter is driven by observation, not theory. Specific candidates, such as axions and neutralinos, may be theoretically motivated, as is the Higgs boson. --Amble (talk) 14:55, 23 May 2012 (UTC)

• One problem is the stuff is badly-named. If it doesn't interact with electromagnetic radiation, it's not so much dark as transparent. As transparent as Harry Potter with his magic cape on. Imagine a lens made of material you cannot see. The other problem is that the word "matter" which isn't even defined for regular "matter." Mass is a scientific word, but matter is not a scientific word, even if you leave out the "dark" part.

  So, anyway, there's this "stuff." We presume it's not massless like photons. Perhaps it has rest mass, like neutrinos. Evidently it has more rest mass than neutrinos, or else it wouldn't act as it does (if it was very low mass and coupled with the Big Bang, it would be so fast as to have escaped galaxies completely, but instead it seems to be stuck by the gravity of them; yet how has it "cooled" with no interaction to cool it? Evidently only from the space-expansion of the Big Bang, like the cosmic microwave background). Anyway, it's (as we said) apparently transparent, and worse still, you couldn't "feel" it even if you stuck your hand in it ("feeling" something, means your hand has an electromagnetic interaction with it). Particles of it should go through you, like neutrinos. So, it's at least as "ghostly" as neutrinos, and maybe even ghostlier, if it doesn't undergo weak interactions. It's barely there. We don't have words for that kind of thing. Dark is wrong, as it has a connotation of absorption, instead of transparency. Matter is wrong also, if you mean anything like normal matter. The problem is that this stuff is so odd that we're short of language. SBHarris 02:59, 24 May 2012 (UTC)

Sbharris: some interesting points, it is indeed "transparent" but the term "dark matter" is widely accepted and the article has to reflect this. The general term "Matter" is slightly context-specific, but usually refers to fermions or composites thereof (protons, neutrons etc) with rest mass. Massless photons are never called "matter"; massive bosons e.g. the W, Z and Higgs boson are a grey area: they do have rest mass, but don't obey number conservation laws like fermions, so usually don't count as "matter". (An aside: the mass of a proton or neutron is a lot larger than the summed masses of its three quarks, due to binding energy: but protons and neutrons are definitely "matter", and this binding energy definitely gravitates, so the definition of matter is slightly fuzzy at a deep level.)

We know that nearly all dark matter must be non-relativistic to be bound in galaxy/cluster structures, therefore it has rest mass, and it's almost certainly fermions to obey conservation laws, hence it is "matter-like" though not any Standard Model particle.

As to how it "cooled"... yes it is the expansion of the universe; massive non-interacting particles lose momentum inversely proportional to the universe's expansion factor, in the same way as microwave background photons lose energy. This is sometimes called "Hubble drag"; it is not a real "drag", but due to the fact that a moving particle "overtakes" stuff which was previously expanding away from it. I'll try and add some of this in at some point. Wjs64 (talk) 22:37, 19 July 2012 (UTC)

"A blind analysis of 224.6 live days × 34 kg exposure has yielded no evidence for dark matter interactions.... The PL analysis yields a p-value of ≥ 5% for all WIMP masses for the background-only hypothesis indicating that there is no excess due to a dark matter signal.... The new XENON100 result continues to challenge the interpretation of the DAMA, CoGeNT, and CRESST-II results as being due to scalar WIMP-nucleon interactions."[19] Npmay (talk) 19:28, 30 July 2012 (UTC)

"for PBHs with mass from 10² M⊙ to 10⁸ M⊙... The ionization of IGM due to PBHs with such density parameters does not affect the global reionization history of the universe since reionization from each PBH only covers a tiny patch of the universe. Unlike reionization from first stars, therefore, such reionization has little impact on CMB temperature anisotropies. Accordingly the PBH density parameter constrained from WMAP data, that is Ω_PBH < 10⁻⁷ (Ricotti et al. 2008), is several order of magnitude larger than the value we obtained above. In other words, we can conclude that 21 cm fluctuation observations have a potential to probe the PBH abundance which is impossible to access by CMB observations."[20] (emphasis added.) 207.224.43.139 (talk) 03:46, 31 July 2012 (UTC)

My issue is with the "housekeeping flag": that the article is "too technical" for the general audience. As an undergrad physics major this was exactly the sort of content I was looking for. A bit over my head (okay a good bit) but not too much for me to get a grasp of it, especially if I read it carefully, followed the references and did additional reading. To make the article or subject accessible to the general reader, without removing technical content, would require a book of several hundred pages. My understanding is that is not the purpose of Wikipedia (maybe WikiBooks). I don't think there is a way to do that? You cannot reduce some concepts at the edge of our understanding to something the general reader can easily grasp, without simplifying by removing information and technical content.

Perhaps what you need is a new general article that glosses over almost all of the detail, with the technical information in this article as a sub-article or series of sub-articles (but then you are starting to write a book). So basic question is where to draw the line?

- Mark 69.120.77.51 (talk) 08:36, 6 August 2012 (UTC)

The Article should at least explain, early on in the introduction and in broad, non-too-technical terms, why Dark matter is not thought to just be rogue planets, interstellar asteroids etc. (which also mostly escape detection.)--Cancun771 (talk) 13:28, 15 August 2012 (UTC)

"... instead of the relationship between observable light and stellar mass being universal, it varies between different types of galaxies — with some older galaxies having three times the mass suggested by the light they give off..."

"'The question of how you should turn light from a galaxy into a prediction of its mass has been hotly debated but up until now nobody has been able to kill off the idea that there's a simple and universal way to convert observed light into mass,' said Dr Cappellari. 'We now think we've done that by eliminating the 'fuzziness' in models caused by dark matter. It's exciting because it reveals how much more there is to discover about how galaxies, and the early Universe itself, evolved."

"The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised. It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast."

http://www.ox.ac.uk/media/news_releases_for_journalists/120425.html http://www.sciencedaily.com/releases/2012/05/120501211411.htm

Quoted from the same article, one is the university source, the other is a notable science website. There are dozens more available through a quick search.

Basically, they've proven that there is absolutely no predictable relationship between luminosity and mass, and they contend "dark matter" is most likely just "matter" that we can't see from Earth. — Preceding unsigned comment added by 71.60.33.136 (talk) 12:07, 19 September 2012 (UTC)

You say "they've proven that there is absolutely no predictable relationship between luminosity and mass". I don't see where that comes from - the study seems to conclude that the relationship is more complex than was previously assumed, not that there is no relationship at all. I also can't see anything in these references that supports your assertion that the study concludes that dark matter is mostly baryonic. Gandalf61 (talk) 12:52, 19 September 2012 (UTC)

I'll second Gandalf61's comment. They've adjusted the old model for estimating galaxy mass - a straight luminosity-to-mass ratio - and made a more complex model where different classes of galaxy have different luminosity-to-mass ratio. That has nothing to do with dark matter - and the vast majority of mass in all of these galaxies is still dark matter (dark matter is about 90% of galactic mass, and the updated estimates change by at most a factor of 3).

The noteworthy elements from this work were a) an improved understanding of how luminosity relates to galaxy type (obvious in hindsight; galaxies with more star formation for a given mass will have more bright but short-lived stars), and b) improved techniques for measuring the mass and mass distribution within galaxies (by measuring the velocity distributions of stars at different locations within the galaxies, if I understand correctly).

Per Gandalf61, these releases say nothing at all about the nature of dark matter and very little about its distribution, so it's puzzling that you'd cite them as support for your position. --Christopher Thomas (talk) 20:36, 19 September 2012 (UTC)

I think it's fair to say that the theory is generally accepted, but this article lays it out like dark matter is in the same kind of "generally accepted" as relativity and evolution.

I am reading articles every now and then about some observations failing to go hand in hand with predictions in regards to dark matter. But this article reads as if dark matter theory is a fait accompli, we are just awaiting confirmation on the particle. — Preceding unsigned comment added by 217.76.196.150 (talk) 06:41, 25 October 2012 (UTC)

Nothing can be done about this I think. The fact that "dark-X" is just a recent and unsubstantiated metonymy for unexplained observations is just lost on the authors of this stuff, they've blown past that to virtual careers in the stuff. To be cheerful about it, reflect that ultimately science does produce truth and phlogistications on aether like stuff are subsequently the source of much mirth. 72.228.190.243 (talk) 10:43, 25 January 2013 (UTC)

Also it's false to say that there's a theory of dark-whatever, a lot of speculation and conjecture doesn't add up to a coherent theory. 72.228.190.243 (talk) 08:18, 29 January 2013 (UTC)

WP:NOTFORUM Dark matter is a well grounded component of current cosmological theory, with a solid mathematical basis, and successful predictions to its name. If you would like to contribute something to the article with reliable, published sources, please do so. - Parejkoj (talk

) 17:27, 29 January 2013 (UTC)

With the caveat that the precise identity of the dark matter is still unknown, it's existence has been accepted in the mainstream for three-plus decades or so. I've added a reference for that fact. 188.26.163.111 (talk) 23:22, 31 January 2013 (UTC)

Dark Matter is a mathematical assumption to several unexplained phenomenon we saw in deep space. It's like seeing a elephant trunk through a thicket and we assume there's an elephant behind it even though we don't see the elephant. 161.142.139.55 (talk) 03:46, 17 May 2013 (UTC)

"Dark matter is estimated to constitute 84% of the matter in the universe and 23% of the mass-energy."

I checked the source which this phrase links to and there is nothing about the differentiation between matter and mass-energy. Dark matter is said to constitute 23% of matter. So I think this phrase is inaccurate and needs to be fixed or else one should choose a different scientific source for it.Louigi Verona (talk) 12:17, 17 December 2012 (UTC)

I'll change it to energy density. As for the source, it's fine. Waleswatcher (talk) 21:02, 17 December 2012 (UTC)

'Mass-energy' simply refers to using mass–energy equivalence to compare the two. Energy density is technically fine as a term as well although it may obscure the point a bit more for the casual reader. 'Total energy' (of the universe) is probably a better choice, because that's what these percentages represent. There's nothing wrong with the conversion and comparison, by the way. It's commonly done in this context, e.g. in Ostriker & Steinhardt's review in Science, which is as reliable as it gets in this field. 188.26.163.111 (talk) 23:26, 31 January 2013 (UTC)

All in all for public and nonspecialist this wikipage is confusing, because it miss some details, that are not known to nonspeacialist: 1. Are there any dark matter/energy near black holes? Thank's for clarifying, that black holes are not dark matter. Also can black holes suck in dark matter? 2. Is there any dark matter/energy at all near material objects, like stars, planets and so on? If no - what is the minimal distance from them? There should be something about them common - so far I have never heard, that dark matter/energy is detected together with plain matter at least in reachable distance, but it is out there somewhere...

— Preceding unsigned comment added by 92.22.24.181 (talk) 03:38, 13 June 2013 (UTC)

" the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Thus, dark matter is estimated to constitute 84.5% of the total matter in the universe.".

So, how many percent does dark matter constitute? 26.8 or 84.5? --Ysangkok (talk) 16:33, 1 June 2013 (UTC)

Both. Dark matter is 26.8 % if you include dark energy, and 84.5 % (which is 26.8 / (4.9 + 26.8)) if you leave out dark energy. Gandalf61 (talk) 16:58, 1 June 2013 (UTC)

It is still confusing. I believe that the sentence needs to be reworked. I also picked throughit and had to question the validity of the percentages, and I'm still not satisfied. :) Damotclese (talk) 16:21, 29 July 2013 (UTC)

There is the phrase ...replacing the laws established by Newton and Einstein. I don't believe that is entirely accurate, the proposed alternate suggestions would modify Newtonian and Einsteinian laws, not replace them. Einstein did not replace Newton, he modified Newton, thus if the current Newtonian and Einsteinian laws were needed updating, it is more accurate to use the word "modifying," not "replacing." Anyone agree? Disagree? I just hate seeing text claiming that Einstein "replaced" or "destroyed" Newton, that's not true. Damotclese (talk)

I agree. This is a important distinction. I would go so far as to say 'extended' the laws of physics. Mtpaley (talk) 19:24, 29 July 2013 (UTC)

I tweaked the sentence to remove "replace". I don't think "extended" is supported by sources or necessary. —Alex (ASHill | talk | contribs) 20:25, 29 July 2013 (UTC)

68.188.203.251 (talk) 12:23, 5 July 2013 (UTC) Excerpt: MOND stands in contrast to the more widely accepted theory of dark matter. Dark matter theory suggests that each galaxy contains a halo of an as yet unidentified type of matter that provides an overall mass distribution different from the observed distribution of normal matter. This dark matter accounts for the uniform rotation velocity data without modifying Newton's law of gravity. This very clear and simple explanation should be the lead sentence in the first paragraph. DARK MATTER THEORY SUGGESTS..........

MOND is essentially a

FRINGE hypothesis which doesn't merit a prominent mention in the lede of the dark matter article. MOND is covered in plenty of detail in the body of the dark matter article. —Alex (ASHill | talk | contribs

) 20:29, 29 July 2013 (UTC)

Is there any connection between Dark Matter and the Higgs Field, as it is the Higgs Boson that is supposed to confer mass, and it was the gravitational effect of Dark Matter (implying a "missing mass") that led to the proposition of the theory of Dark matter. John D. Croft (talk) 11:10, 12 September 2013 (UTC)

Presumably, yes. The Higgs Field is currently presumed to be responsible for generation of all mass terms for "matter". However, this "matter" is experimentally understood primarily in terms of baryonic matter that we are familiar with, following reasonably well understood weak and strong interactions. As there are currently no assured answers for the composition of dark matter, we don't know for certain these laws are directly applicable, however, this seems to fit the preponderance of evidence, and many models, such as described in this article, attempt to describe dark matter in terms of the known interactions, which would imply mass is generated by very similar or identical means. So, in short, the Higgs field would likely underlie the physics of dark matter, unless dark matter turns out to be much stranger than current theories hypothesize. 70.247.175.236 (talk) 14:47, 29 December 2013 (UTC)

+

Is there a reason why this article fails to mention magnetic monopoles as dark matter candidates? 70.247.175.236 (talk) 14:47, 29 December 2013 (UTC)

It seem really lacking that Wikipedia doesn't have an article focusing on the oft-quoted numbers used in this article, for one about the "composition of the universe". I may have simply overlooked something. Is there such an article, and if so, can it be linked in? 70.247.175.236 (talk) 20:27, 29 December 2013 (UTC)

After a lot of time reading the DM article, I never saw answers to some questions I think would be common. I'll list them here as suggestions for additional discussion in the article to improve it.

Does dark matter possess angular momentum and what is the evidence of this? Or if not, why wouldn't it? The galactic halo of dark matter seems to suggest it does not. Wouldn't dark matter accumulating around a galactic center bring with it angular momentum? Does the spherical DM halo mean the DM particles do not collide with one another? Is each DM particle in an elliptical as opposed to spherical orbit around the galactic center?

Dark matter is mostly non-baryonic. Is this suggesting that it may be composed of bosons rather than fermions? Would the lack of evidence for interaction between DM particles suggest it might be bosonic?

Besides gravity, it was mentioned that the weak force is thought to be the only other force by which DM interacts. But the article made no mention of the effect the weak force might have on DM behavior or observations.

Can DM particles collide with one another? It was mentioned that the Bullet Cluster observations suggest either weak or no interactions. If none, does this mean that multiple particles could be in the same place at the same time?

Might two DM particles be able to orbit one another at very close distances where they have significant mutual gravitational interaction? What might the orbital radius be if so? Sub-atomic? Could such systems be a part of DM?

Can DM collapse into DM black holes? Can it fall into a black hole, and if so, is it like regular matter in that it can't escape? Would there be any observable differences between black holes formed mostly of conventional matter vs from DM?

Experiments on earth looking for DM particles were mentioned. Is it virtually certain that DM particles are present all around us, or do some hypothesized forms of DM exclude that possibility?

Does the lack of an obvious DM particle candidate in modern particle physics theory present a major problem to that theory?

Tedtoal (talk) 10:18, 11 February 2014 (UTC)

Einstein's relativity at small scales is the equilibrium among inner componental spin oscillation, and external motion of a relativistic group of particles.

Einstein's relativity at huge scales is the equilibrium among star rotation, and external motion of stars.

Because of all the galatic disk has a common overall spacetime perspective, smaller items (stars) of the glacactic disk cannot change their external speed but the only part of the relativistic equilibrium they can, and that is star rotational speed.

[Veiler Sword's theory 11:40 11/4/2014 o very old but standard theory, proven by NASA in the past with data they never collected officially, the data are there shoutoung at us - WAKE UP- MY NOBEL PLEASE!!!!] — Preceding unsigned comment added by 2.84.205.100 (talk) 20:52, 11 April 2014 (UTC)

Mordechai Milgrom's MOND paper stems from 1993, not 1983 (1983 is mentioned twice in that paragraph).83.136.73.85 (talk) 12:55, 19 May 2014 (UTC)

1983 is correct. See for example the bibliography here: [21]. Why do you say 1993? --Amble (talk) 19:15, 19 May 2014 (UTC)

Here is some fargoing idea about the universe. Why couldn't negative mass particles exist. It is unlike anti-matter, which still has positive mass.

Based on general relativity (that already allows for negative energy states; the gravitational field is supposedly negative energy) the properties of negative mass particles would be: - negative mass matter self repells (in the newtonian sense, where gravitational mass = intertial mass, the force would be still attractive but the acceleration would be in the opposite direction of the force!) - positive mass matter self attrackts (standard physics)

But combinations of negative mass and positive mass matter would react strangely: positive mass matter is repelled by negative mass matter, but negative mass matter accelerates (force is repulsive but acceleration is now opposite to the force!) towards the posite mass matter.

Imagine the universe forms in the big bang both positive mass matter and negative mass matter. Positive mass matter clumps together like in the standard big bang model, but the negative mass matter distributes and spreads out, but then later interacts with the positive mass due to gravity and clumps together (while still self repelling) around galaxies, not inside them.

Theoretical models show that in this way the rotation anomoly of galaxies can be explained.

See this paper: http://www.fqxi.org/data/essay-contest-files/Choi_FQXINegativemassisstab.pdf

Robheus (talk) 10:00, 2 June 2014 (UTC)

First bullet currently reads:

"The theory of Big Bang nucleosynthesis, which very accurately predicts the observed abundance of the chemical elements,[12] predicts that baryonic matter accounts for around 4–5 percent of critical density of the Universe. In contrast, evidence from large-scale structure and other observations indicates that the total matter density is substantially higher than this."

The 2nd sentence is unclear: can't tell what it's trying to contrast and what "this" is referring to at the end. The first sentence references baryonic matter as a "percentage of critical density", while the 2nd sentence seems to be considering "total matter density", so if the 2nd sentence is trying to compare and contrast different values for these two different measures, then it seems an apples-to-oranges comparison.

I'm not informed enough in how to fix this nor do I understand what point(s) the original author intended, but any such efforts to improve are appreciated. I certainly appreciate the hard work many have put toward this page in the last few months! — Preceding unsigned comment added by 98.100.23.77 (talk) 13:11, 26 June 2014 (UTC)

I specified that the total matter density is about 30% of the critical density. —Alex (ASHill | talk | contribs) 13:49, 26 June 2014 (UTC)

OK, but now the relevance of making this comparison is not clear in relating it back to the amount of baryonic matter in existence. I suggest a completely different paragraph to discuss critical density and how it relates to total matter density. Alternatively, please clarify in the article why the difference between the critical density and total matter density is important in understanding the amount of baryonic matter, but only if you can prove that "total matter density is about 30% of the critical density" is a fact - I don't think it is, especially since NASA believes that WMAP determined that they were equal, per http://wmap.gsfc.nasa.gov/universe/uni_matter.html — Preceding unsigned comment added by 98.100.23.77 (talk) 20:07, 2014 July 8 (UTC)

The critical density and total matter energy density are observed to be the same. (They don't necessarily have to be, but they are.) From your source: "WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 0.5% margin of error)." And your source lists atoms as 4.6% of the total density and dark matter as 24% for a total matter density of 28.6%, which is about 30% of the total matter/energy density (or, equivalently, the critical density). Is your suggestion that the (jargon) term "critical density" should be defined? I see your point, but can't see an obvious way to do it cleanly in that paragraph. And the linked article is pretty straightforward, I think. But suggestions welcome. —Alex (ASHill | talk | contribs) 23:56, 8 July 2014 (UTC)

If you look at the laws of physics and balance. Dark energy doesn't enter into the balance of product and comesumtion of mass but indeed it is universal the energy excites all laws of physics something we've ever seen its capability and capacity is clearly seen not by the eye, but surely universal it could go through particles of mass and matter , and alter a change in particles like a d.n.a. strand that it is invisible but go through human flesh and alter its organism this particle or energy could be the god energy ,privilege energy I call it why I have done some research on how the human brain works this energy clearly creates the necessary neurology behavior to create thought like a sencer particle that's why we have dreams when we're asleep. Dark energy clearly under minds all physics and how can we use it for our wellbeing. — Preceding unsigned comment added by 68.207.112.124 (talk) 05:37, 3 August 2014 (UTC)

To undesratnd Dark Matter by Suchard's theory it is first necessary to look at another long denied effect "electro-gravity" and understand why it defied detection. Electro-gravitaty according to E. Suchard's theory ^[1] is based on charge separation and is NOT the usual Biefeld-Brown ionocraft/lifter because a pico-farad capacitor, of any shape under 50000 volts, is not capable of maintaining enough charges to manifest measurable results of real electro-gravity in vacuum. The predicted effect depends on the electric field divergence and therefore on charge densities and on their integration but not directly on the electric field as in conventional ionocrafts. Equation (30) in Suchard's paper has a divergence component, that according to interpretation (6) possibly without the 2 in the denominator, offers a way to achieve electro-gravity via the non-inertial term -2Div(U)P(Myu)P(Nu)/Z in (30) where P(Myu)P(Nu)/Z deviates from the local notion of conservation laws and reminds of Dennis Sciama's Inertial Induction Cite error: The <ref> tag has too many names (see the help page)., Cite error: The <ref> tag has too many names (see the help page). though the full theory is with a complex probabilistic time field that results in a more complex equation. The resulting postulated gravitational field resembles an electric dipole and offers elevation on the expense of the trajectories of far bodies of mass quite the same way ebb and tide take energy from the Earth rotation and moon's trajectory. According to that assumption, the divergence term coincides with electric charges and therefore can explain the Dark Matter effect by a negligible excess of intra-galactic negative charges if the constant of electro gravity is 1/8PiK. K is the constant of gravity and Pi=3.1415... and positive charges if the constant is 1/K. The conservation law (31) with zero charge Div(U)=0 is the ordinary local conservation. Matter fields in Suchard's theory prohibit inertial motion, i.e. matter is expressible by an acceleration field as an antisymmetric matrix that rotates the velocity vector of any particle that can measure proper time and results in it's acceleration in the field. The anti-symmetric matrix is a member of the Lie Algebra of SU(4) and it describes rotation and scaling without the need for Clifford Algebras. This acceleration field does not affect photons and does not directly change the space-time curvature. It takes a very strong electric field of about 1 Mega Volts over 1mm to expose an acceleration of 8cm/Sec^2 of even uncharged particles in an electric field. The non-inertial acceleration, though dependent on mass, is not gravity despite the dependence on mass. Gravity itself results from the divergence of a curvature vector that coincides with the electric field. In the classical limit, the non-inertial acceleration is opposite in direction to the gravity that results from the electric charges. The constant that describes the relation between the square norm of a curvature vector and energy, decides which "force" will be dominant. If it is more than 1/4PiK then the gravity that emanates from electric charges is stronger than the acceleration field which is opposite in direction. If it is less than 1/PiK then the acceleration field that prohibits geodesic motion, is stronger. Written covariantly, an acceleration field is an antisymmetric matrix and not a 4-vector. Electrons have an attracting acceleration field and a repulsive gravitational field and positrons have a repulsive acceleration field and an attractive gravitational field. Matter itself results from coupling between an event wave function and a field of time - not a coordinate of time !!! Matter is described in an appendix in Suchard's paper, "Event Theory", as a non-zero curvature vector and a series of wave functions, each representing an event which by Sam Vaknin's theory is an actual transfer of the time itself. Suchard's paper complements a previous research from 1982 by Sam Vaknin on a Chronon field amendment to Dirac's equation ^[2][3]