Talk:Dark matter/Archive 2

message: Well, i'm not an astrophysicist either (so i don't consider myself adept enough to contribute to this article directly), but recently i heard about an effect known as 'Silk damping', which is said to be a very strong evidence for the existence of dark matter. It says that radiation in the early universe was too strong for baryonic matter to lump, and whenever some baryonic particles aggregated, the electromagnetic radiation, which was just everywhere, tore them apart again. Therefore, compaction of baryonic matter was only possible when the universe was about 380.000 years old, at the time when radiation decoupled from matter and the universe became 'transparent'. We have a souvenir photo of this point of time, which is known as the cosmic microwave background and it shows density fluctuations, which can only be explained by matter which must have aggregated much earlier, and which must not have interacted with radiation at all, or it would'nt have been able to lump because of the radiation. I'm not able to describe this process in a scientifically accurate way (nor am i a native English speaker), but maybe someone else knows more about Silk damping and is able to add it as evidence to the article (?) --82.141.54.30 07:33, 13 December 2005 (UTC)
thread_title: Silk damping

message: I have fixed a mistake in the article which is unfortunately widespread.
Dark energy is accounted for the universe acceleration 
whereas dark matter is accounted for the prevention of galaxies disintegration.
--Tomer Ish Shalom 02:26, 9 Jun 2005 (UTC)
thread_title:  galaxy disintegration? 

message: What exactly is Jaan Einasto supposed to have done?  This page and the article under his name call him "one of the discoverers of dark matter," but there are no more details.  According to the article under his name, Einasto has been active in physics long after the dark matter problem was discovered, so it doesn't really make sense as it is.  If this claim is true in some sense, it requires some elucidation. -- Reuben 04:00, 20 Jun 2005 (UTC)
thread_title:  Jaan Einasto 

message: Almost all the popular culture references need toi be removed.  They are about matter which is dark, not about dark matter. Ken Arromdee 02:06, 22 August 2005 (UTC)
replies: text: Even if one finds the section 'Popular culture' appropriate, it should be moved elsewhere, because it is becomming too large compared to the main DM article. A new article should be written and one should give one link to that article from here. Count Iblis 11:56, 22 August 2005 (UTC)
thread_title:  Popular culture 

message: Yes, I would like to see more in this section, including an explanation of Cooperstock and Tieu and what the problems are with their theory, sicne I haven't really been able to find that information reliably elsewhere.  I have also read some (unreliable sources which say that electromagnetic forces on plasma may explain galaxtic rotation.  See here which is where I first saw that idea.  I don't know about it's validity, but I think the alternative explanations section needs to be expanded in general. -NMB
: The page you link argues with most of modern physics, for often trivially fallacious reasons.  Like the relativistic addition of velocities "obviously doesn't apply for material objects".  I am rather disinclined to set a precedent of writing down, and then arguing with, every silly little thing they say.  As for why Cooperstock and Tieu are wrong, the abstract of the one paper disagreeing with them says it pretty well:
:Recently a new model of galactic gravitational field, based on ordinary General Relativity, has been proposed by Cooperstock and Tieu in which no exotic dark matter is needed to fit the observed rotation curve to a reasonable ordinary matter distribution. We argue that in this model the gravitational field is generated not only by the galaxy matter, but by a thin, singular disk as well. The model should therefore be considered unphysical.
:What that means is, their model had a disk of zero-thickness and non-zero mass that was producing the rotation curves, and they didn't realize it.  I guess that's worth half a sentence, which I'll add now. 
: My point is, we should certainly include plausible alternative explanations, but not ones which aren't. -- SCZenz 19:34, 15 October 2005 (UTC)
replies: text:  Hi SCZenz! If you have time then perhaps you can put some stuff in from this article and this one. These ideas seem to be less problematic than the Cooperstock/Tieu stuff. Count Iblis 01:13, 16 October 2005 (UTC)
replies: text:  Cooperstock and Tieu now have a new preprint out. The paper included a modified solution that no longer requires the singular disc. 
In alternative proposals, I think there is something missing about scalar-tensor theories. There are many of them so at least the name should be pronounced in the text. And some of them are interesting, especially, since they are popular for explaining inflation and since Higgs fields (which are scalar fields) couple in a gravitation-like manner to the particles that get mass through them (Dehnen, Frommert: Int.J. of Th. Phys. 29(4):361 (1990), 30(7):985 (1991)). --141.70.111.178 15:20, 29 October 2005 (UTC)
thread_title:  Alternative Explanations 

message: Count Iblis deleted the following:
The role of electrical and magnetic interactions may explain missing mass. Electromagnetism can impart force between masses up to 10 to the power of 39 greater than that of gravity, over vast distances. Gravitational effects would be overwhelmed. See Plasma cosmology.
with the comment Plasma cosmology is not serious science. But conventional cosmology has a big problem: We know there are large coherent magnetic fields by observing spectral line splitting: Inference: There are large coherent charge flows occuring: Inference: There are large electric currents in space. We have laboratory experiments showing plasma naturally forms current-carrying filaments. We know 99% of the visible universe is plasma. And we know electrical forces are far more powerful than gravitational forces. eg in a proton-proton interaction the repulsive force is approx 10 to the power of 37 times greater than the gravitational attraction. So why is conventional cosmology so focussed on gravitational interactions? Why isn't there space here for even *mentioning* Plasma Cosmology? How can such censorship be scientifically justified?
: Your comment has several parts that need to be responded to individually.  I'll try to separate the points out for clarity.
:1. Please sign your comments.  It's easier to come to a consensus that way, and it can be a useful token of good faith.
:2. It's fair enough to ask Count Iblis to justify his edit on the discussion page (that is, right here).  If you haven't already, I suggest you put a note on his talk page - not an argument, just a polite request that he explain his edit.  It's likely that some reference to plasma cosmology would be acceptable.
:3. Arguing for or against the correctness of a scientific idea in Wikipedia discussion pages doesn't tend to be very productive.  Although some individual participants may be very knowledgeable, it's not for Wikipedia to decide whether plasma cosmology has anything to it or not.  To say it another way, a Wikipedia article is not science, even one that's about science.  The content of the article is justified encyclopedically, not scientifically - Wikipedia doesn't follow the scientific method.
:4. Using the word "censorship" can only be inflammatory.  It won't help get the article to a state you can be happy with.
:--Reuben 04:25, 19 December 2005 (UTC)
replies: text: Basically, per Wikipedia:No original research and Wikipedia:Reputable sources, we only use scientific information from cited, peer-reviewed journals or other reputable sources.  Does that help explain it? -- SCZenz 04:29, 19 December 2005 (UTC)
replies: text:  Sure, that's part of what I was trying to express.  (The original formatting in my comment may have left it unclear who wrote what; I've tried to fix that). --Reuben 04:38, 19 December 2005 (UTC)
thread_title:  Plasma physics edits 

message: That image in "Alternative explanations" is too small for the text to be readable, ugly, and does not provide any information to supplement the text of the article. I suggest removing it. -- CYD
: I'm inclined to concur.  Any objections? -- SCZenz 18:13, 29 October 2005 (UTC)
replies: text: I agree. This looks more like an advertisement for isracast than useful information. It would be nice to replace this by an overview of dark matter candidates containing links to wikipages. Also Dark matter in popular culture should be moved to a different location.Count Iblis 21:22, 29 October 2005 (UTC)
thread_title:  Image necessary? 

message: Concerning this passage in the beginning "If dark matter does exist, it vastly outmasses the "visible" part of the universe [1]. Only about 4% of the total mass in the universe (as inferred from gravitational effects) can be accounted for. About 23% is thought to be composed of dark matter. The remaining 73% is thought to consist of dark energy, an even stranger component, distributed diffusely in space, that probably cannot be thought of as ordinary particles."
First off, "the remaining 73%" does not make sense because it is 77% that remains.  If the number 73 is correct, then it should not be designated as "the remaining".  If the number 77 is correct then it should be changed to this.
And also, what is meant by "Only about 4%...can be accounted for."?  Only 4% can be accounted for by what exactly?  I assume this means that only 4% can be accounted for by "visible matter"..but this is not clear.
*Your second point is right, that sentence should be clarified; I'll fix it now.  Your first point is wrong: 4% for visible, 23% for dark matter, and 73% for whatever-it-is, adds up to 100%. -- SCZenz 22:21, 13 November 2005 (UTC)
thread_title:  Lack of clarity 

message: The Cooperstock and Tieu papers are great and fascinating to people following the field, but seeing as how we're updating the page every week or so as one side launches a challenge on the other, perhaps it is not yet "encyclopedic" knowledge. Why not just clip it from the article until the community decides whether the work is important and correct? -- Xerxes 16:35, 27 December 2005 (UTC)
replies: text: Hi Xerxes, my preference would be to replace that paragraph by one or two sentences, saying that Cooperstock and Tieu have formulated a model that seems to predict a thin disk of (possibly exotic) matter at the symmetry plane of the galaxy.Count Iblis 16:54, 27 December 2005 (UTC)
replies: text: Actually, C&T make some very compelling arguments that the alleged disk of matter is simply a mathematical curiosity, with no physical significance. The singularity arises from their use of the absolute value function on the z coordinate, which works everywhere else, but produces a discontinuity with the derivatives at z=0. I'd prefer a statement about the disputed nature of the C&T model, but leave out specific criticisms, especially those that require a fairly detailed understanding of the C&T model to understand.70.168.137.34 03:28, 18 July 2006 (UTC)
thread_title:  Cooperstock and Tieu 

message: Is it possible that there exists some type of anti-Dark matter that balances the effect of Dark matter on the universe? If there isn't, could it be created? --Guthrie 20:42, 5 January 2006 (UTC)
replies: text: I'm not a scientist, but I'm sure the honest answer is: show me some dark matter first, and then we'll know more about its properties. Art LaPella 21:13, 5 January 2006 (UTC)

text: Matter and antimatter behave identically with respect to gravity, since there is a strong symmetry (CPT) that insists that antiparticles have exactly the same mass as particles. So anti-(dark matter) could not be distinguished from dark matter observationally (via lensing or rotation curves or whatever). -- Xerxes 21:57, 5 January 2006 (UTC)

text: It depends on what the dark matter actually is.  Some dark matter candidates have distinct antiparticles, and some don't (like neutralinos).  However, if they do exist, they would not balance out the effect of the dark matter; the particles and antiparticles would interact with gravity in the same way, like Xerxes said.  In fact, we only know about dark matter through its gravitational effects, so if anything did cancel out those effects, we would not know it was there!  You might be thinking of something like dark energy.  It doesn't cancel out the effects of dark matter that we see in galaxies or galaxy clusters, but it does dominate the dynamics of the universe on the largest scales, making it expand faster and faster.  This acceleration is the opposite of what you would see if the universe contained only matter (including dark matter).  You can find out more in the dark energy article. --Reuben 04:44, 6 January 2006 (UTC)

text: It's possible that dark matter is a third party when compared to the relationship between matter and anti-matter, and may be the only type of matter that won't experiance anhillation.--Dansanman 06:26, 3 February 2006 (UTC)
thread_title:  anti-Dark matter? 

message: I think that maybe something in this sense could be added. Paul Marmet proposes that molecular hydrogen could fit the role of mysterious dark matter, as it is the most common element in the universe, and also, is more stable in the molecular form than as a atom, but also harder to detect. Here is a text for people more knowledgeable and better writers than me to analyse and eventually add something to the article:
*Discovery of H2, in Space Explains Dark Matter and Redshift
--Extremophile 00:54, 11 May 2006 (UTC)
replies: text: Please don't.  This is fringe stuff.  The link is to an article from 21st Century Science and Technology, which is Lyndon LaRouche's magazine of fringe science.  If you read this and Marmet's other articles, you can eventually trace everything back to Marmet's rejection of GR and SR on philosophical grounds. --Reuben 01:38, 11 May 2006 (UTC)
replies: text: I would not do anything myself, but I would find interesting and even desirable, despite of being fringe stuff. Much of actual mainstream was once fringe. Wikipedia has things that, at least in my opinion, are far less encyclopedic than fringe science, such as whole categories about pokemon and articles such as "towel". And since these fringes are not just plain crackpots like that timecube guy, I think that at least some brief mentioning/linking to main articles would be interesting. --Extremophile 20:17, 11 May 2006 (UTC)

text: "When light passes through normal molecular gases, such as oxygen, nitrogen, and others, radiation excites the resulting electric dipole in the molecule, and some energy is scattered or absorbed. However, in the case of molecular hydrogen, there is no dipole moment, so that no radiation can be absorbed or emitted. "*Discovery of H2, in Space Explains Dark Matter and Redshift  This is not accurate. Hydrogen molecules DO radiate in their rovibrational states, but they must be heated to temperatures of about 100 K.  But interstellar space is usually colder than this, so thats why they are not seen to radiate much.  Even so, electromagnetic radiation from the visible portion of the spectrum up to higher energies is enough to dissociate hydrogen molecules, so thats why hydrogen in its molecular form only exists in large quantities in dark clouds.  These clouds are rare and not very massive, so hydrogen molecules cannot account for the missing mass.  The universe contains much more atomic hydrogen, which is easily detectable and has been accounted for.  01:55, 11 May 2006 (UTC)
thread_title:  molecular hydrogen hypothesis 

message: Is it real or is it vandalism? I couldn't find it on Google or Google Scholar, but maybe it's misspelled. Art LaPella 01:44, 11 May 2006 (UTC)
replies: text: I think the editor was confused.  From the heavy water reference, it sounds like he might be thinking of SNO.  The name is similar to COUPP, which is a really cool WIMP detection project using bubble chambers.  So maybe it's the result of confusion between COUPP and SNO. --Reuben 01:51, 11 May 2006 (UTC)
thread_title: COOUP project

message: Somebody knowledgeable should include the findings by Wim de Boer and his team - they found traces of Dark Matter Annihilation in the data of the EGRET (telescope).
http://www.edpsciences.org/articles/aa/abs/2005/46/aa3726-05/aa3726-05.html
--217.236.226.31 08:40, 12 May 2006 (UTC)
replies: text: Certainly an exciting claim, but their model seems pretty dodgy. See, for example, criticisms in Is the dark matter interpretation of the EGRET gamma excess compatible with antiproton measurements?. There is no need to include every recent extraordinary claim without substantial proof in Wikipedia; let history sort things out for a bit. -- Xerxes 16:21, 12 May 2006 (UTC)
thread_title: EGRET data

message: The page was in need of some cleanup/rewrite, and so I took it upon myself. I think that the "alternative explanation" part needs to be paired down especially since MOND is somewhat fringe. It doesn't need to be removed, just contextualized. We also need some more references, but I think this page has improved substantially. --ScienceApologist 12:09, 19 May 2006 (UTC)
replies: text: Nice edits.  This page had been drifting for a while, and your cleanup has done a lot to bring it back into line.  Perhaps it would be good to think about how to organize dark matter articles overall: as it is, the same topic is often covered several times in different articles, without any consistent scheme.  There are a lot of different ways to divide the topic: hot vs. cold, theory vs. experiment, direct vs. indirect detection, baryonic vs. nonbaryonic, by candidate, by experiment... --Reuben 18:09, 20 May 2006 (UTC)
thread_title: Dark matter rewrite

message: Isn't dark matter inferred from several anomalous astronomical observation, in which case it may explain them, but to suggest that "Dark matter explains them" is a truth which I don't think has yet been met? --Iantresman 17:35, 28 May 2006 (UTC)
replies: text: Dark matter is a catch-all term that refers to the explanations for concomitant observations listed in the article just as much as it refers to the particles themselves. Even if dark matter turns out to be epicyclic in nature (and there's pretty good evidence that this probably isn't the case), it still will be able to explain the observations. --ScienceApologist 19:30, 28 May 2006 (UTC)
replies: text:  I think that Iantresman means that we don't know for sure that dark matter exists and that any explanations based on it (even if it is not epicyclic in nature) could turn out to be incorrect. This is a matter of language. You could say that dark matter does explain certain phenomena even if in reality dark matter has nothing to do with them. The fact that a ceetain theory explains certain phenomena doesn't rule out other theories explaining these phenomena. Count Iblis 21:57, 28 May 2006 (UTC)
replies: text: The fact that a ceetain theory explains certain phenomena doesn't rule out other theories explaining these phenomena. --> Precisely correct, which is why the wording needs to stay as written that dark matter explains phenomena. It doesn't preclude other explanations! --ScienceApologist 22:01, 28 May 2006 (UTC)
replies: text: So although it may not be relevent to this article, by writting, for example, that "interacting parallel Birekland currents explains anomalous galaxy rotation curves without the need for dark matter", because it doesn't rule out other theories, is a fair wording? --Iantresman 00:48, 29 May 2006 (UTC)
replies: text: Almost. The issue would be in what precisely "interacting parallel Birekland currents" means. Since these phenomena exist independent of galaxy rotation curves, it would be a requisite to explain a detailed observational argument for their existence (what the evidence is, why they haven't been observed directly, etc.) If an article that discussed such things contained these descriptions and if it is clear that the "interacting parallel Birkeland currents" in question refer directly to this postulate, then the wording would be fine. If you are interested in writing such a piece, I'm more than happy to help you. --ScienceApologist 03:16, 29 May 2006 (UTC)
thread_title: Dark matter explains several anomalous astronomical observations

message: Regarding Alternative theories, can I suggest a one or two line introduction which perhaps categorises them type (if that's appropriate), or chronologically, as they all appear to run together. Unfortunately I do not enough knowledge of all the alternative theories to do this myself. --Iantresman 17:40, 28 May 2006 (UTC)
replies: text: We do need to clean up this section. Take a crack at it, sure. --ScienceApologist 19:30, 28 May 2006 (UTC)
thread_title: Alternative theories

message: how come this article takes a completly non-theistic aproach to explaining the forces that guide the universe? wouldn't it be better to show at least some more diverse alternative theories than this?--F.O.E. 13:38, 31 May 2006 (UTC)
replies: text: This particular article is not really about force, and the Wiki article on force is about that force which can be measured qualitatively. However, you may find that the article on  Force (disambiguation) is more relevant. --Iantresman 13:44, 31 May 2006 (UTC)
thread_title:  more alternative theories