Talk:Dark matter/Archive 6
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Dark Matter and Invisible Pink Unicorns
"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 Phlogiston. Phlogiston was invented to account for the missing mass after burning or oxidization. Dark Matter was invented to account for the Universe not expanding at the expected rate.
The Higgs field is yet another device used by the religion of Quantum Physics cosmology to explain ignorance with Ad ignorantium arguments. These are for atheists who drink deep from Russell's teapot and believe in UFOs or Bigfoot, but refuse to believe in an intelligently ordered Universe. They have no problem with the Infinite monkey theorem for producing literary masterpieces.
You can believe an infinite number of tornadoes in an infinite number of junkyards can produce a Boeing 787, but the probability is low. We live in an Observable Universe that is, however, finite in age and mass. The number of possible molecules to produce the most simple of lifeforms is greater than the if you used all the matter in the OBSERVABLE universe once a second to create the models for the 15 billion years of existence you could create all the non-life versions without producing a single living tissue. Those who have the religious faith to believe in life existing by random probability are far more religious than I am.
Arguing about whether Dark Matter acts as a liquid is like arguing about the number of angels on a pinhead. It is religion; not science.
John Lloyd Scharf 02:16, 16 January 2012 (UTC)
- 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)
How does a galaxy's dark matter halo maintain its roughly spherical shape?
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)
Dark Matter and its affect on light.
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".
Gravitational lensing (not gravitational microlensing; that's for small, compact objects) does indeed allow concentrations of dark matter to affect the path of light, but all forms of matter do that, and it's already discussed in the "observational evidence" section. Any change to the lede would have to a) avoid giving the impression that it interacts with light in any other manner, and b) avoid giving the impression that gravitational lensing is the most important or most obvious way of inferring that dark matter is present (it isn't; galaxy rotation curves are the easiest way to notice something's there, and astrophysical arguments about structure formation and nucleosynthesis in the early universe are among the more important arguments).
With regards to "making intelligent changes" that others take down, please make sure you understand why they were taken down. For science articles, WP:V, WP:RS, WP:NOR, and WP:UNDUE are the most common reasons for changes being reverted (in no particular order). When an editor reverts a change, they usually leave a note in the "edit summary" (the line next to the edit in the article history) that says why they reverted it.
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)
Merge Hot, Warm and Cold dark matter here?
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. --ChetvornoTALK 15:44, 29 March 2012 (UTC)
- Probably. Mixed dark matter is another one. 71.215.74.243 (talk) 22:03, 2 April 2012 (UTC)
multiple partical dark matter
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 Line of sight gravity
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 WP:RS and WP:NOR, the only material that should be included in this article is material published in venues that are considered reliable sources (per this subsection of WP:RS). The term "line of sight gravity" appears in scientific literature, but means something completely different that what you appear to be using it for (it refers to doppler data from space probes indicating acceleration due to gravity along the line of sight to the probe). The term "MOG" is used in scientific literature for "Modified Gravity", and does not refer to any single specific theory. Modified gravity is already discussed in the article. --Christopher Thomas (talk) 23:45, 27 May 2012 (UTC)
Obviously dark matter is the matter residing in singularities
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:NOR and WP:RS, Wikipedia is not the place to present your own new ideas about dark matter. The article is supposed to reflect ideas that have been presented in peer-reviewed scientific literature (per WP:SCHOLARSHIP) or that have otherwise made enough of a splash to satisfy the notability guidelines (WP:N). --Christopher Thomas (talk) 06:12, 18 June 2012 (UTC)
Jan Oort's "discovery" of dark matter
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)
Assumption of correctness
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)
- 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)
- 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)
Third Matter?
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)
Dark matter and black holes
- The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.
Draft table
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I welcome edits directly to the draft above from anyone who would like to add material from peer reviewed sources. If, however, you wish to delete material or make additions which are not supported by peer reviewed sources, please copy the table and make another one below. Thank you. 67.6.175.184 (talk) 21:20, 9 February 2012 (UTC)
Here's a review by three experts http://arxiv.org/pdf/0907.1912v1.pdf . Kamionkowski is a leading expert in cosmology, a long-time professor at Caltech that recently moved to Johns Hopkins, and obviously a reliable source (the other two as well, but he's the most eminent). The review doesn't even so much as mention black holes. Due weight? Zero, according to that. Another review: http://arxiv.org/pdf/hep-ph/0404175v2.pdf The authors are well-established experts in the field. Silk is at Cambridge or Oxford, I forget, and is one of the dons of the field. It mentions MACHOs once, in passing, and never mentions black holes as a dark matter candidate. Due weight? Zero, according to that. Another review: http://arxiv.org/pdf/astro-ph/0301505v2.pdf again by an established expert. MACHOs are mentioned, with about 1/3 of a page devoted to them. He says they are directly ruled out by microlensing experiments as being less than 25% of DM at 95% confidence. That was 2003, the constraints have since gotten much stronger, as Carr et al show. Another review, this time in Nature, perhaps the premier science journal: http://www.nature.com/nature/journal/v468/n7322/pdf/nature09509.pdf It never mentions either MACHOs or black holes. It says clearly that WIMPs are the favored candidate, and then lists other possibilities (which don't include MACHOs or black holes). Lastly, one more review. http://downloads.hindawi.com/journals/aa/2011/968283.pdf Direct quote: "MACHOs can only account for a very small percentage of the nonluminous mass in our galaxy, revealing that most dark matter cannot be strongly concentrated or exist in the form of baryonic astrophysical objects. Although microlensing surveys rule out baryonic objects like brown dwarfs, black holes, and neutron stars in our galactic halo, can other forms of baryonic matter make up the bulk of dark matter? The answer, surprisingly, is no..." I found all of those via google, as the first few hits for a search on reviews of dark matter. I didn't in any way pre-select them or filter them. They make it blindingly obvious that MACHOs of any kind, and black holes in particular, are not taken seriously by the field as a dark matter candidate. By wiki's policy of due weight, black holes can therefore receive at most a passing mention, and only to say that they are believed to be ruled out (ref Carr 2011 for instance). Waleswatcher (talk) 23:33, 9 February 2012 (UTC)
I think it would help the article if it included a second table (or perhaps a new section) that summarizes for all known gravitationally attracting particles, objects and energies (protons, neutrons, electrons, photons, large black holes, etc.) why they cannot comprise dark matter, for those that have been rejected as candidates. SEppley (talk) 15:07, 19 February 2012 (UTC)
I believe the controversy here is due to a strong disagreement about the extent to which microlensing studies have ruled out compact objects as dark matter. From my preliminary study, the belief that "our available statistics is still too small to draw definite conclusions on the dark matter content in the form of compact halo objects" (from http://arxiv.org/pdf/1001.2388v1.pdf) is currently the prevailing view, meaning that black holes of any mass are again allowed as viable dark matter possibilities. I'm very interested in others' understanding of this situation, as I've only recently started reading on it. Npmay (talk) 07:24, 6 March 2012 (UTC)
Iocco et al (2011) has a fascinating discussion of avoiding various inconsistencies such as cuspy halos. It rules out adiabatic compression and shows that the expected ranges of density and galactic interior slopes are consistent with baryonic dark matter. Novati (2012) conclusively rules out compact objects under 0.l solar mass, isn't sure about 0.1-1.0 solar masses, and frustratingly doesn't say a thing about larger masses before abruptly concluding that more data is necessary. Npmay (talk) 06:12, 8 March 2012 (UTC) | |||||||||||||||||||||||||||||||||||||||||||
Do gravitational microlensing studies rule out compact objects as dark matter?
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Recently I noticed that there is quite a controversy about the composition of dark matter (see Talk:Dark matter#Draft table for instance) and while looking in to it, I found that there is some disagreement about the extent to which gravitational microlensing studies have ruled out compact objects as dark matter. I noticed that [16] specifically says that small numbers of microlensing events observed by the many searches "does not allow us to draw definite conclusions on the content of compact halo objects" as dark matter. That paper cites [17] which is by authors famous for mapping dark matter in the universe. It has this to say:
Those seem like relatively narrow ranges, but my question is about conclusions regarding mass ranges which are open-ended upwards. If dark matter was composed of objects which were, say, 100,000 M⊙ on average, wouldn't that result in far fewer microlensing events -- because there would be so many fewer total MACHOs -- than could have ever expected to be observed in those studies? What is the reasoning involved in ruling out any compact objects larger on average than a couple dozen solar masses with any of these studies? Npmay (talk) 20:54, 6 March 2012 (UTC)
For black hole MACHOs, Carr et. al. is a good start. For baryonic MACHOs, the strongest constraints come from light element abundances etc. that rule out baryonic dark matter of any type. Waleswatcher (talk) 16:42, 7 March 2012 (UTC)
As for supermassive black holes in galactic centers, there are two theories. 1) Many individual mass concentrations (or density fluctuations, if you like) in the very first formations of clouds eventually becoming galaxies resulted in rather massive, however stellar-size primordial black holes, which collided while the galaxy was still in its formation. 2) After the big bang (or rather in the course of it), a significant amount of dark matter (theory according to supersymmetry, sparticles) formed in the first instances of the creation of the first particles (before protons and neutrons were formed) and joined to form both supermassive black holes as well as the first ever structure filaments of the universe. There is a string-theoretical description of black holes, named "fuzzballs". When you look down the article and look at the sources, there are four lectures on the subject by Samir Mathur (held at CERN), the third being the calculation of a stellar black hole, the fourth an extrapolation of these findings to the big bang and the likely development of the universe in string-terms. Hope this helps! 87.184.27.249 (talk) 13:37, 9 March 2012 (UTC)
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Evidence for intermediate mass black holes
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http://arxiv.org/pdf/0910.1152v1.pdf -- Frampton and Ludwick's 2009 basic 100,000 solar mass peak calculation for primordial IMBHs. http://www.sciencedirect.com/science/article/pii/S0920563210001003 -- Frampton's 2010 explanation of why 100,000 solar mass dark matter IMBHs are consistent with the orbits of wide binaries, microlensing, and galactic disk stability. (WIMPs still struggle with the cuspy halos, not to mention dwarf galaxies.) http://iopscience.iop.org/2041-8205/720/1/L67/pdf/2041-8205_720_1_L67.pdf -- Lacki and Beacom's 2010 "Almost All Or Almost Nothing" paper indicating that most all of the WIMPs would have fallen into black holes if there are more than a very small number of them. http://arxiv.org/pdf/1205.4012v1.pdf a very new paper explaining the conditions under which primordial black holes are allowed by nucleosynthesis element ratios; basically if inflation didn't happen at a constant rate. http://arxiv.org/pdf/1204.3619v2.pdf another very recent paper showing "new pathways to PBH dark matter candidacy" using reduced dimensional analyses. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2006.10801.x/abstract -- Lodato and Natarajan's 2006 theory of supermassive black hole formation which someone cited in opposition to the existence of IMBHs, but which actually describes the production of 100,000 solar mass black holes. http://arxiv.org/pdf/1205.6467v1.pdf -- this brand new paper suggests that supermassive black holes' early quasar behavior kept the other black holes from being able to grow. 71.212.249.178 (talk) 08:30, 10 July 2012 (UTC)
Can you please be more specific about what you believe has been misrepresented? 71.212.249.178 (talk) 21:44, 14 July 2012 (UTC)
Please see also http://arxiv.org/pdf/astro-ph/0407285v1.pdf, http://arxiv.org/pdf/astro-ph/0602388.pdf, http://arxiv.org/pdf/1008.5147v2.pdf, and http://arxiv.org/pdf/1203.4100.pdf 71.212.249.178 (talk) 15:27, 11 July 2012 (UTC) |
Stellar motion discrepancy
One "Serious blow" link
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 unsigned comment added by ParksTrailer (talk • contribs) 13:59, 5 May 2012 (UTC)
I introduced a statement the other day with links to several news articles referring to a study done that cast very many doubts on the very existence of Dark Matter, which was immediately removed from DM's wiki page. Now that I ask specifically why this is going on, and there are no posts, not a single person has anything to say about it? That response is very inappropriate. I posted on the Dark Matter page only after coming to the understanding that this 100% theoretical substance does not have the same respect from the scientific community. I propose someone jump in here and start a real discussion or my entry be inputted again to the wiki page; without either response one can only assume some rather biased editors. EzPz (talk) 17:43, 5 May 2012 (UTC)
- 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)
Inference of knowledge
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 says about dark matter. Right now, most of that literature says "expected to be a form of subatomic particle", with minority opinions saying that it may reflect modified gravity laws or something else. These minority views are already noted in the article, with space appropriate to their weight (per WP:UNDUE). The evidence for particle nature (which admittedly isn't iron-clad) is given in the article, and reflects what the sources say (short version: microlensing maps of it say it acts like an almost-perfect fluid in galactic collisions, and big bang nucleosynthesis calculations say pretty much the same amount has to exist in the form of a non-interacting particle for element ratios to work out properly). Debating the merits of each position is beyond the scope of Wikipedia, per the notice at the top of this page. If you feel that the article does not accurately reflect its cited sources (or other sources 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 Dark matter (disambiguation), "Dark matter is matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects." I'd change it to say, "Dark matter is theoretical matter..." and I think that would make a much clearer start to the article. Ensuring links to cosmology and astronomy are still up there shouldn't be too difficult. "Theories regarding dark matter are of particuar interest in the study of astronomy, cosmology, and particle physics." Thus, "Dark matter is theoretical matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects. Theories regarding dark matter are of particuar interest in the study of astronomy, cosmology, and particle physics." But, I am sort of iffy about "..whose presence can be inferred..." as it is not a who, and might try instead, "Dark matter is theoretical matter that is undetectable by its emitted radiation, but is generally believed to account for large unexpected gravitational effects on the galactic and intergalactic scale. Due to the subjects hypothetical nature, particular theories are occasionally changed or rejected, but dark matter is generally considered to constitute 84% of the total mass in the universe and 23% of total 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)
- From Dark matter (disambiguation), "Dark matter is matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects." I'd change it to say, "Dark matter is theoretical matter..." and I think that would make a much clearer start to the article. Ensuring links to cosmology and astronomy are still up there shouldn't be too difficult. "Theories regarding dark matter are of particuar interest in the study of astronomy, cosmology, and particle physics." Thus, "Dark matter is theoretical matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects. Theories regarding dark matter are of particuar interest in the study of astronomy, cosmology, and particle physics." But, I am sort of iffy about "..whose presence can be inferred..." as it is not a who, and might try instead, "Dark matter is theoretical matter that is undetectable by its emitted radiation, but is generally believed to account for large unexpected gravitational effects on the galactic and intergalactic scale. Due to the subjects hypothetical nature, particular theories are occasionally changed or rejected, but dark matter is generally considered to constitute 84% of the total mass in the universe and 23% of total 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)
- 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)
XENON100 results negative after 225 days
"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 ΩPBH < 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)
I don't think the article is "too technical"
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)
Dark matter is very different from current theory, and vast majority may be baryonic.
"... 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)
acceptance
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)
- 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)
Convenient Explaination
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)
What is mass-energy?
"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)
Confusing percentages
" 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)
Replacing Newton And Einstein?
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)
Simple description of Dark Matter on Wiki Mond missing here
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)
Dark Matter and the Higgs Field
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)
+
Magnetic Monopoles
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)
Questions about the nature of dark matter
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?
Time Equilibrium at Larger Scales
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)
Correction
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)
Dark matter modelled at the basis of (hypothetical) negative mass particles
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
First bullet under Baryonic and nonbaryonic dark matter doesn't make sense
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)
- 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)
facts or fiction
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)
Electro-Gravity via Chronon field as the reason for Dark Matter
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]
References
- ^ Suchard, Eytan (June 2014), "Electro-gravitational Technology via Chronon Field", Physical Science International Journal, p. 1158, doi:10.9734/PSIJ/2014/11129
- ^ California Miramar University, available on Microfiche in UMI and from the Library of Congress http://catalog2.loc.gov/vwebv/holdingsInfo?searchId=115001&recPointer=0&recCount=25&searchType=1&bibId=3810279
- ^ Vaknin S Time Asymmetry Re-Visited
- above text added by user talk:Eytan il 22:24 17/9/2014.
- I am not convinced that we can use any of this in the article, as when I do a search for the topic, it does not seem to be widely discussed by other writers. Graeme Bartlett (talk) 23:10, 17 September 2014 (UTC)
Non baryonic dark matter must be invisible, and with no EM interaction, can't be touched or felt. There are no lumps of it and no chemistry of it.
Though the article makes clear that a little dark matter might be baryonic and thus made of atoms, the lede also says clearly, and the rest of the paper confirms, that most dark matter cannot be baryonic (else it would screw up Big Bang element ratios), and thus cannot be made of atoms, but instead must be made of some new undiscovered electrically neutral particle.
Matter made of some new neutral particle and NOT atoms, is not otherwise "simply matter that is not reactant to light" (as the lede says). That's a heck of a big "simply!" What does not "reactant" to light, really mean? It means it is utterly transparent, not just "dark"-- but the lede doesn't say this (it should). In addition, the neutral particles feel gravity and (maybe) the weak force, but if they do not feel the EM force, they are not only transparent, but they cannot be felt or touched. Since feeling and touching are EM interactions. Also so is chemistry, and thus there is no dark matter chemistry. There are (thus) no lumps of dark matter, as without EM interaction the particles have no way to stick to each other or to anything else (except gravitationally). It follows that dark matter is quite ghostly-- not only invisible but also physically insubstantial. A non-gravitational portion of it could go right through you and you'd never know it. It's insubstantial as the sterile neutrinos some people think it might be. But even if not, it must act like neutrinos, and we all know how hard THEY are to detect. Millions of them go through every square cm of us every second, and we never notice.
So, the lede should say all this. The largest part of dark matter is thought to be transparent, not made of atoms, has no chemistry, is particulate with no lumps, is not touchable, and is completely insubstantial. It is not "ponderable" at our scale, where we do not feel gravity (or the weak force). It also doesn't feel the strong force, so it isn't like insubstantial neutrons that still kill you from radiation. We don't see or feel neutrons or neutrinos, and dark matter is like them. I don't think there's anything controversial about any of this. No astronomer suggests that we hunt for dark matter like hunting for Harry Potter under his cloak of invisibility-- by stumbling around until we bark our knee on a lump of it, than pick it up with tongs and put it in a labeled bottle. But as the lede is now written, there's absolutely nothing in it to suggest why we couldn't do just that. Thus, the lack of EM interaction for most dark matter is asserted, but even though the EM interaction is how we see, feel, and touch, nothing in the lede tells us the certain implications of no strong interaction or EM interaction in physics or real life, which is that particles become neutrino-like. Which you cannot see, touch, or interact with, in any normal way. Would you mind if I fixed this? SBHarris 00:24, 23 September 2014 (UTC)
Unseen vs. unseeable
From a historical point of view, there must have been a transition from "dark matter" meaning matter that we haven't seen (because it isn't very bright / our telescopes are not sufficiently sensitive) to matter that cannot be seen (in the electromagnetic sense) to matter that does not feel the strong force. If there are names or dates associated with these transitions could we add them to the article? Leegrc (talk) 11:20, 10 October 2014 (UTC)
Douglas A. Pinnow, Ph.D.
I have no affiliation with Douglas A. Pinnow, but he provides some important data in his article. He states numerous sources such as universities have detected dark matter deep below the earth and are getting figures around 9 GeV. The Wikipedia article mentions these experiments and the universities, but fails to mention their published results. Could you guys take a look at his article and see if the data in his article could be added to the Wikipedia article on dark matter? Hopefully someone will be able to find where the universities have published their results. His article is titled "Dark Matter Physics. Physicists are Getting Closer to Solving the Puzzle of Dark Matter", and published on October 21, 2013 by Douglas A. Pinnow, Ph.D. 72.25.65.244 (talk) 17:52, 7 December 2014 (UTC)
- Here's a link to the article. http://www.darkmatterphysics.info/ 72.25.65.244 (talk) 19:28, 7 December 2014 (UTC)
Evidence for Dark Matter
Two articles, in case they are useful to the authors: http://physicsworld.com/cws/article/news/2015/feb/10/dark-matter-seen-in-the-milky-ways-core http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3237.html — Preceding unsigned comment added by Jcardazzi (talk • contribs) 00:39, 13 February 2015 (UTC)
Consensus
To @Tetra quark, Isambard Kingdom, and Ashill: Since I respect and appreciate you all for the work you do on wikipedia, is there a way I can help to foster teamwork and collaboration among you guys? Or do you prefer to continue to revert each others edits? It's about a word and a link. There are pros and cons for both versions. So why not find a compromise by mutual concession? It hurts to see capable editors wasting their energy and to become hostile. Cheers -- Rfassbind -talk 00:25, 7 February 2015 (UTC)
- Moving to the talk page re the first two sentences of the article: It seems to me that "cosmos" is an imprecise and potentially-confusing term in the sentence "The existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation and the large-scale structure of the Universe." I don't think using the word "universe" twice in two sentences is a big issue writing-wise. I might avoid it if there were a way to do so that maintains the precision, but I think that Universe is very much the right word in both sentences. —Alex (ASHill | talk | contribs) 00:42, 7 February 2015 (UTC)
- Writing isn't easy. But one thing I sense, here, is that introducing word variety simply for the sake of word variety was resulting in possible, albeit subtle, curiosity for the reader. Why say "cosmos" when what was being discussed was the "universe"? To some, the words are not quite synonymous. Not that I intend to debate the distinction, but for some "cosmos" means a sort of functioning mechanical reality, in contrast to "chaos", while "universe" tends to mean everything. Of course, astronomers might have a variety of opinion on these things, but why invite attention to the words themselves, when "dark matter" in the "universe" is the subject at hand? Isambard Kingdom (talk) 01:54, 7 February 2015 (UTC)
- Gosh, the reader will understand that it means universe, as it's pretty obvious Tetra quark (talk) 22:24, 7 February 2015 (UTC)
- I disagree. "Cosmos" has a much more colorful connotation, in my opinion and experience, and thus potentially changes the meaning for readers. "Universe" is clear, concise, and most accurate. —Alex (ASHill | talk | contribs) 22:44, 7 February 2015 (UTC)
- Gosh, the reader will understand that it means universe, as it's pretty obvious Tetra quark (talk) 22:24, 7 February 2015 (UTC)
OK, I see Isambard Kingdom and Ashill are firm in their conviction that the word "Universe" has to be preferred over "cosmos". I think that opinion has to be respected. What puzzles me, however, is that none of you argued for keeping the disputed link large-scale structure, which I also mentioned above. Seems Isambard Kingdom and Ashill don't disagree so much about this open question. Could we agree to remove that link as Tetra quark suggested? -- Cheers, Rfassbind -talk 23:10, 7 February 2015 (UTC)
- They disagreed with the use of cosmos just for the sake of disagreeing Tetra quark (talk) 23:50, 7 February 2015 (UTC)
- That is patently untrue (and I'd ask you for the courtesy of not speaking for me). I simply don't think that cosmos is the right word in this context for the reasons articulated by Isambard Kingdom and myself.
- I don't think there's any disagreement about the link to large-scale structure; my guess is that Tetra quark removed that link by mistake in undoing a reversion from cosmos to Universe using Twinkle. In subsequent reversions, the link has stayed. Correct me if I'm wrong. —Alex (ASHill | talk | contribs) 01:43, 8 February 2015 (UTC)
- I agree with Ashill. "Universe" is appropriate word. Links are not the issue. Isambard Kingdom (talk) 07:50, 8 February 2015 (UTC)
- I agree with Ashill. "universe" is appropriate word. Links are not the issue. Arianewiki1 (talk) 22:16, 13 February 2015 (UTC)
Introducing word variety for the sake of variety (i.e. because it appears less dull) is poor professional writing because it detracts from the content. --JorisvS (talk) 11:05, 10 February 2015 (UTC)
Oort and Zwicky
In the introduction, the work of Oort and Zwicky is described as "based upon flawed or inadequate evidence". I think that that is misleading. In those cases, if most of the dark matter later turned out to be undetected baryonic matter, so what? Is it flawed because it's not WIMPs?Michael9422 (talk) 22:07, 7 March 2015 (UTC)
- And is it the work of Oort that is flawed, or the work of both Oort and Zwicky? It's not really clear what is meant here. Also, the claim that the work is flawed needs to be substantiated. Aarghdvaark (talk) 08:06, 13 March 2015 (UTC)
Misleading illustration
Re: the illustration in Galaxy_rotation_curves consisting of two plots of velocity of the individual stars of a typical spiral galaxy against their distance from the galactic centre: one (A) for expected values, and the other (B) for observed values. We are told that the discrepancy is what leads astronomers to conclude that there must be dark matter distributed around the galaxy.
I can understand this argument if the main feature of the two plots, (A) and (B), was that they differ. However, looking at curve (B), the main feature appears to be that the curve is almost perfectly straight, and almost perfectly horizontal. This means that, in addition to there being dark matter present, there must (coincidentally) be some perfectly balanced amount: not too little, that the curve dips one way, and not too much, so that it dips the other way.
This would be indicative of there being some more precise mechanism at work, there, not merely the need to add dark matter.
I have raised this question on Quora (indeed, much of the above text is copy-pasted from there), and the conclusion appears to be that the straightness and horizontalness of the curve is a simplification, and not a true artefact of the observational data.
Would it be possible to clear up this misleading impression from the illustration? (I pose this as a question since, unfortunately, I have neither the means to provide a revised illustration, nor access to the observation data to justify it. Thanks in advance, therefore, to anyone who can address this. TheAMmollusc (talk) 11:58, 19 March 2015 (UTC)
- How about the image at galaxy rotation curve, Image:M33 rotation curve HI.gif, which uses actual data? —Alex (Ashill | talk | contribs) 13:31, 19 March 2015 (UTC)
- I'll further note that, in fact, the rotation curve of large spirals (M33 is relatively small) like the Milky Way are remarkably close to flat. See, eg, the rotation curves here, which are based on real data -- note the compressed vertical axis scale in the Clemens (1985) figure, which makes the curve appear less flat than it is. The uncertainties are pretty large far out in the halo (beyond most of the light/stars), but the data are consistent with a flat line (and very much inconsistent with the exponential fall-off expected once you're outside the stars in the absence of dark matter). So a flat line is more or less as good a guess as any, even though the uncertainties are large enough to not require any fine tuning. —Alex (Ashill | talk | contribs) 13:39, 19 March 2015 (UTC)
- Very good. I particularly like the illustrations on the njit page, which at least shows the lumpiness of the curve (and hence of the inferred concentration). To my mind, the horizontalness of the curve still raises questions (perhaps not so suggestive of MOND, but a strange coincidence nonetheless), but from my point of view, an illustration of this kind would be better than the one that is currently in the article. Thanks for all your efforts on this. TheAMmollusc (talk) 06:32, 20 March 2015 (UTC)
External Links
The external link "A nice animation about dark matter" directs to <http://astroparticle.aspera-eu.org/index.php?option=com_content&task=view&id=113&Itemid=108>, which however requires a username and password—which most Wikipedia users will not have. Please, either remove or replace with an accessible URL. Tristan (talk) — Preceding undated comment added 03:01, 4 June 2015 (UTC)
- Indeed, it is no longer viewable. Removed the link. Thanks. --Amble (talk) 05:04, 4 June 2015 (UTC)
an old mistake
Spacetime analysis can be based on chromodynamic analysis [inside the "particle event horizon" noise theory expressed by discrete mathematics].
The mathematical field is called "Probabilistically Vectorized Combinatorics".
By expressing "noise theory" via "Probabilistically Vectorized Combinatorics", inside [inside means chromodynamic events within the event horizon of fundamental particles] each fundamental particle, chromodynamic noise itself, forces the particle to exist.
That chromodynamic noise, is constituted by [according to "Probabilistically Vectorized Combinatorics" - oscillational theories are equivalent "if thoroughly defined", "probabilistically vectorized combinatoric theory of noize" is simply a different mathematical language to express the same events - conclusions from each theory can be mathematically translated to evolve the other theory] relativistically (or holographically - interlinked nodes on a sphere surface).
"Probabilistically Vectorized Combinatorics" demands time to be quantized (like movie frames), and "noise" to be consisted by vectorized dots. Τhese vector-points have neither dimensions nor volume. "Probabilistically vectorized" means, that each "dot" has a probabilistic range of virtual arrows, pointing at the "mean (average) lower potential virtual point" and at the next quantum time-frame, that virtual point becomes actual (real).
There are two types of "points". Virtal points and actual. Actual points have a non homogeneous probabilistic vector cloud (point-wavefunction), virtual points on the other hand have a homogeneous probabilistic vector cloud. (we have to use homogeneous functions vs non-homogeneous equations to express probabilistic vestor clouds - "point-wavefunctions") Each actual point always "appears" at a virtual point position. "Non-point positions" are totaly empty areas.
Only "virtual points" can "expand via entropic diffusion" (entropic diffusion is to divide the same amount of energy to more vector-point units, but the overall vectorized sum is the same) to "non-point positions". [dark energy causation]
Only "actual points" can "kill virtual points via compaction" (energy is maintained, the vectorized sum is the same, only now space has shrunk). [dark matter causation] — Preceding unsigned comment added by 2.84.216.225 (talk) 05:16, 30 June 2015 (UTC)
laim of 9 dark matter concentrations
Regarding claim of 9 dark matter concentrations Question: Do we need such updates, just a few days old, in an encyclopedia? I think yes per WP guidelines, and updates made in this article and others. It is not age of the information, but I think the value. The information is sourced. Thank you, --Jcardazzi (talk) 17:10, 3 July 2015 (UTC) jcardazzi
- At best, this information was misplaced: it's weak lensing, not indirect detection. I have moved it to the correct heading. The text is still somewhat lacking since it emphasizes the press release date (not particularly relevant) and doesn't indicate how this is notable relative to previous weak lensing observations of dark matter concentration. --Amble (talk) 09:14, 4 July 2015 (UTC)
Sig figs in dark matter fraction
The article gives the amount of dark matter as a fraction of total matter using a simple calculation: 26.8/(4.9 + 26.8)=0.845=84.5%. The numbers going into this calculation are all known to a precision on the order of 1% (as for example in the Planck results paper used as a source). An anonymous editor using several IP addresses has repeatedly changed this to 0.8454=84.54%, adding a meaningless additional digit of false precision. As it is, the first digit beyond the decimal point in the current 84.5% figure is not terribly significant. A number of editors have reverted this change, but the anonymous editor continues to make the same change without giving any convincing argument. I would like to establish that we have a consensus to leave the calculation with three digits as 26.8/(4.9 + 26.8)=0.845=84.5%, and therefore the addition of any additional digits can be freely reverted. --Amble (talk) 01:35, 8 December 2015 (UTC)
- Generally speaking, digital precision ("quantization") is determined by need. If there is a specific need to report with lots of digits, then they should be reported, otherwise, consistency of precision is preferred. Why does the IP want the additional digit? Does it add anything to the article? It doesn't seem so. Isambard Kingdom (talk) 02:04, 8 December 2015 (UTC)
- The extra digits aren't only unneeded, in this case they're meaningless, since we don't actually know these numbers to any better than ~1% relative precision. --Amble (talk) 02:43, 8 December 2015 (UTC)
- OPPOSE I woundn't say it's unneeded. The other 3 figures used in the article were given by source whereas this one is done by, as Amble has mentioned above, a simple manual calculation. In my opinion, for a significant component that makes up nearly 27% of the Universe, 0.04% would be too large to round down (or round up if the figure were 0.05%). 26.8/(4.9 + 26.8)=0.8454=84.54% looks like an ideal figure here. Obviously, we need more scientific advances to get a more precise figure in the future, but for the time being, this is as close as we can get. 101.186.193.161 (talk) 07:13, 15 December 2015 (UTC)
- "0.04% would be too large to round down" Why do you think so? Given the errors we don't even know whether these 0.04% even exists. Gap9551 (talk) 17:01, 15 December 2015 (UTC)
- OPPOSE I woundn't say it's unneeded. The other 3 figures used in the article were given by source whereas this one is done by, as Amble has mentioned above, a simple manual calculation. In my opinion, for a significant component that makes up nearly 27% of the Universe, 0.04% would be too large to round down (or round up if the figure were 0.05%). 26.8/(4.9 + 26.8)=0.8454=84.54% looks like an ideal figure here. Obviously, we need more scientific advances to get a more precise figure in the future, but for the time being, this is as close as we can get. 101.186.193.161 (talk) 07:13, 15 December 2015 (UTC)
- The extra digits aren't only unneeded, in this case they're meaningless, since we don't actually know these numbers to any better than ~1% relative precision. --Amble (talk) 02:43, 8 December 2015 (UTC)
- Adding a 4th significant digit is wrong, following the basic multiplication/division rules in Significance arithmetic. 4.9 + 26.8 = 31.7 by the addition rule. 26.8/31.7 = 0.845 by the division rule. Gap9551 (talk) 16:56, 15 December 2015 (UTC)
- By the way, from source [2] I find [22], and in the abstract the matter density is 0.308 +/- 0.012 rather than 0.317, what am I missing here? If the original figures are known to about 1%, then maybe they should be mentioned with errors, and the 85.4 figure should probably be listed as 85% in that case. Gap9551 (talk) 16:59, 15 December 2015 (UTC)
revert, discuss...
@Gareth Griffith-Jones: Hi! Thanks for the notice that you reverted my WP:BOLD edit to Dark matter#Baryonic and nonbaryonic dark matter. But it was described simply as "not consutructive".
It definitely was a good-faith edit. Reading the section, I found the discussion of baryonic dark matter buried in the middle, so I tried to rearrange the existing material in what seemed like a more useful presentation order, as explained in the edit comment. That matches the section heading (baryonic first), historical development, and the question I went to the section to answer which I think is a shared by many others: how do we know it's gotta be this weird stuff that we need the particle physicists' help to find?
The answer is that when Fritz Zwicky wrote about "dark matter" in 1932 he was thinking about atoms; astronomers were "dragged kicking and screaming" to the non-baryonic conclusion by the strength of the evidence.
The links to Occam's razor and streetlight effect were somewhat frivolous, but the latter seemed so appropriate I couldn't resist. It was in lieu of a longer discussion that I didn't want to clutter things up with about the fact that astronomers have long intellectual recognized that their observations are biased because they "look where the light is best", and the joke was perfect.
I realize the default revert message is so long it's hard to add any sort of meaningful edit comment, but some attempt to explain would be appreciated; a revert is pretty much by definition controversial.
I honestly thought it improved the section. You, apparently, did not. May we discuss this to find something that we both thinks improves it? Otherwise, I'm stuck making random edits trying to figure out what will get reverted and what won't.
Thanks! 71.41.210.146 (talk) 20:25, 18 January 2016 (UTC)
P.S. Here's a nice history of dark matter thinking. Class notes, but shows lot of seminal historical papers. 71.41.210.146 (talk) 20:38, 18 January 2016 (UTC)
- I have undone my revision 700439391. In view of your passionate post here on this article's Talk page, I bow to your opinion on the subject.
If you want to be taken seriously, I do urge you to register because whilst editing with Dynamic Host Configuration Protocol—a non-static IP—you have a constantly changing IP address and are unable to conduct continued discussions on User/Article Talk pages. Cheers! — | Gareth Griffith-Jones |The WelshBuzzard| — 08:57, 19 January 2016 (UTC)
- I wasn't trying to overwhelm you with passion, only start a discussion about reasons. Presenting my reasons for making the edit was simply a way to start.
- As for your other point... Special:Diff/225732386 71.41.210.146 (talk) 17:40, 19 January 2016 (UTC)
absence of a review
Given the hypothetical nature of this field, is there a peer-reviewed literature review, produced by a credentialed scientist in this area (not input from the forest of cosmological nutjobs) that distills the opposing viewpoints that are on the table in serious debates? This is typically done by some elderly, accomplished physicist, with proven command of the theory and nothing to fear. I see a couple reviews in the bio, but these appear to be from ambitious groups specializing in the assumption of the predominant dark matter hypothesis. Wikibearwithme (talk) 19:10, 18 January 2016 (UTC)
- Are either of these two Physics Reports the sort of thing you're looking for? I'm not familiar with the authors or an expert in the field, but Physics Reports is a reputable journal and each of these reviews has accumulated a healthy 500--1000 citations in less than five years. They're where I would start learning about generic "opposing viewpoints". --David Schaich Talk/Cont 03:28, 29 January 2016 (UTC)
Copyedit
Per tag, I copyedited. The tag only referred to a section, but as per my practice, I hit the whole thing pretty hard. It's about 15% shorter now. Feedback encouraged! Comments:
- Removed a lot of excess contextualization.
- Used acronyms and reduced immediate redundancies.
- Big remaining concern: The organization is very poor. Historical matters are spread throughout the text. The same points are made repeatedly in multiple sections. I propose a complete reorg to correct things. Essentially history goes in History. Each point is made once. The several types of evidence each get a major subsection and are treated in full there. Etc. Please let me know what you think. Lfstevens (talk) 04:57, 1 February 2016 (UTC)
All done. Expert needs to check it all. Plus, I couldn't make sense of Major edit requires checking. Also, see Dark Matter#Velocity dispersions of galaxies, which makes no sense as written. Cheers! Lfstevens (talk) 20:18, 7 February 2016 (UTC)
Hello. I'm aware that this article might need an expert, but I decided to remove the tag you added because it looks like spam. Cheers 187.107.0.247 (talk) 17:09, 13 February 2016 (UTC)
- Looks like spam? Lfstevens (talk) 05:20, 14 February 2016 (UTC)
FRB 150418
The Fast radio burst FRB 150418 was published today; the full text article can be accessed free through the BBC News link at: [23]. It is interesting that astronomer Phil Plait explains that this event was also a means for indirect detection of dark missing matter: [24]. I am not knowledgeable in physics, so I leave this on your desk. Cheers, BatteryIncluded (talk) 03:35, 25 February 2016 (UTC)
- Dispersion in the signal is probably caused by free electrons. These are "dark" in the sense of not emitting light. But are part of normal matter. Graeme Bartlett (talk) 10:19, 25 February 2016 (UTC)
- I put this at the end of the subsection titled "Baryonic matter" since that sort of ordinary matter is what was measured using the fast radio burst.Anythingyouwant (talk) 10:27, 25 February 2016 (UTC)
- Sorry, I strike out "dark" matter above, the publication meant missing (normal) matter. My mistake. Cheers, BatteryIncluded (talk) 16:45, 25 February 2016 (UTC)
- No problem, that point was tricky, and your strikeout is correct. Cheers.Anythingyouwant (talk) 16:57, 25 February 2016 (UTC)
- Sorry, I strike out "dark" matter above, the publication meant missing (normal) matter. My mistake. Cheers, BatteryIncluded (talk) 16:45, 25 February 2016 (UTC)
- I put this at the end of the subsection titled "Baryonic matter" since that sort of ordinary matter is what was measured using the fast radio burst.Anythingyouwant (talk) 10:27, 25 February 2016 (UTC)
A note
Good morning,
Please excuse my English. I have a note regarding the term "Dark matter" or "Dark energy". Why not to use a term "Technically unmeasurable matter and energy". With best regards, Vaclav Kolarcik Václav Kolarčík (talk) 07:14, 22 February 2016 (UTC)
- Dark matter and dark energy are measurable, so that would be a lousy term. Roger (talk) 18:53, 24 February 2016 (UTC)
I would like to apologize. I meant directly unmeasurable. — Preceding unsigned comment added by Václav Kolarčík (talk • contribs) 08:24, 26 February 2016 (UTC)
Could you please delete this item ("A note") regarding the Dark (unvisible prevalent) matter from the talk page. I am new to Wikipedia and I realized, that it is not the right place for this type of discussion. Thank you. With regards, V.K. vakol (talk) 07:39, 29 February 2016 (UTC)
- Don't worry. It's a small section and it will be archived after a while. Happy editing! --Amble (talk) 16:34, 1 March 2016 (UTC)
Lorentz correction of virtual endofeynmanian particles (usually bosons)
Inside a galaxy many interaction occur among particles, virtual or actual. The final products if relativistically compared may travel faster or slower than the speed of light. Due to special relativity no particle is allowed - not even mistakenly due to a slightly different frame of reference - to be perceived as moving faster than light, because background noise of the fields inside galaxies, force both the event and the beholder to be perceived as one entity, and that endogalactic convection field forces overall cohesion. The interaction constants (coupling constants), the overall energy and the light-speed limit inside a galaxy force some "Boost matrix corrections", thus some non expressed speed gets transformed into inertia in order energy is maintained. The galactic connection field doesn't allow interaction products be perceived as superluminal (faster than the speed of light) by endogalactic observers (well statistically, because it is a probabilistic phenomenon) thus the non expressed speed, gives rise to slightly heavier or more energetic virtual endofeynmanian (inside Feynman diagrams) particles. The result is an excess of spatial endogalactic inertia. — Preceding unsigned comment added by 2A02:587:4100:8500:7491:FE0C:214C:8550 (talk) 02:46, 21 April 2016 (UTC)
A really misleading article
OK, it's studded with references that make it seem iron-clad. But there's a huge difference between hypothetical and observed. The galaxy collision examples are classic. What's seen is gas, followed by empty space, followed by matter (actually, a reanalysis found no empty space usually exists, so the effect may be a 3D artifact.) The empty space, is where dark matter is supposed to end up in a collision. Even if true, empty space is not a direct observation. All that has been seen, if there is too much separation between gas and matter, is an unexplained gravitational effect.
Forget WIMPS, XENON100 and LUX were killer blows. Dark matter faces a crisis. People like Christoph Weniger, who at one time claimed he detected hints of dark matter, now say they were wrong.
It's not that matter isn't causing the gravity that must exist to exist. It's that dark matter is less and less likely to be a good model for it. Claims that "most astronomers" believe in dark matter lack references.
Brian Coyle — Preceding unsigned comment added by 208.80.117.214 (talk) 08:47, 15 May 2016 (UTC)