Talk:Dark matter

Dark Matter is a new current event!

http://www.newscientistspace.com/article/dn9809-cosmic-smashup-provides-proof-of-dark-matter.html

Ring of Dark Matter

As far as I know, the community is rather certain that this ominous ring is an artifact, based on bad data analysis, namely circular correlations of noise. This assumption is also supported by the fact, that the group's description of their work in their paper was very fishy and partly self-contradicting. Therefore, I suggest to delete this part in the article.
--René 21:50, 17 October 2007 (CET)

Dark Matter, in Prospective

Although I am not a student of astronomy or physics, is the theory of Dark Matter mostly attributed to this pattern?: Our moon, as all natural satellites, rotates around a planet; the planet rotates around it's parent star; A star rotates around it's parent galaxy's super-massive black hole; Galaxies, which travel, are caused by an unknown force, perhaps it is the dark matter that causes galaxies to movie? Or is it simply the gravity by it's neighboring galaxies that cause the movement? Or Both? I ask this simply because the article does not delve into this. Mdriver1981 (talk) 12:06, 19 September 2008 (UTC)

When on the topic of black holes, does that article, or perhaps the article about Micro black hole have any relevance for this article? —Preceding unsigned comment added by RBM 72 (talk • contribs) 00:11, 16 December 2008 (UTC)

Merger of Nonbaryonic dark matter

• Merge. Nonbaryonic dark matter lacks context and is does not merit its own article.

Agreed. SwordSmurf (talk) 12:32, 8 November 2008 (UTC)

Agreed as well. The Nonbaryonic Dark Matter article has nothing that this article does not already contain. Not sure if that means the merger has been executed already, because Nonbaryonic Dark Matter still exists as a separate article. Verkhovensky (talk) 18:51, 11 December 2008 (UTC)

Agree, support merge as per above. AC+79 3888 00:44, 30 December 2008 (UTC)

Disagree. There is a separate article for baryonic dark matter, so there should also be one for nonbaryonic dark matter. UMinnAstro (talk) 21:29, 3 January 2009 (UTC)

Disagree Nonbaryonic dark matter is a notable topic in itself and well-suited for its own article. It can be mentioned in this article, but further details about it would be invited if it had its own article. Themfromspace (talk) 16:07, 23 January 2009 (UTC)

Agree with merge. That baryonic dark matter has its own article (which it still does at the moment) does not entail that nonbaryonic dark matter should. Nonbaryonic dark matter is the 'important' kind of dark matter, and is frequently what is actually meant in casual uses of the more general term. It is what this article should be (and is) mostly about. False vacuum (talk) 22:37, 3 February 2009 (UTC)

Discussion superseded by new actions: The contents of the Nonbaryonic dark matter article have been integrated into this one (after being improved somewhat), and the redundant article has been proposed for deletion. False vacuum (talk) 00:26, 4 February 2009 (UTC)

Error in 1st pagargraph

In the second sentence it states "According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy account for the vast majority of the mass in the observable universe."

In fact the presence of Dark matter was first inferred from Zwicky's studies of the rotation of the Milky Way Galaxy, which showed the centre of the Milky Way rotated as if it were a solid, and that this could not be explained if visible sources of matter comprised the major composition of the Milky Way Galaxy. This needs correction. John D. Croft (talk) 13:12, 8 November 2008 (UTC)

You're mistaken on several points. Zwicky studied galaxy clusters, notably the Coma cluster, and not individual galaxies. Much later, it was shown that the Andromeda galaxy has a rotation curve with constant velocity at large radius. This was convincingly demonstrated by Vera Rubin using her own observations and those of other astronomers. Note that rotation as a solid body would have velocity proportional to radius, which is not what's observed. Finally, the rotation curve of the Milky Way galaxy has been especially difficult to determine, since our view is obstructed in parts, and because the radius includes extra uncertainties from the conversion from geocentric to galactocentric coordinates. --Amble (talk) 20:36, 10 November 2008 (UTC)

The rotation curve of the Miky Way is very precisely measured, and is the better measured rotation curve of any galaxy, but it is hard to measure it any better than that for the reasons Amble mentios above. —Preceding unsigned comment added by 58.240.157.37 (talk • contribs) 15:23, 30 November 2008

The velocity measurements for the Milky Way may be precise, but we have better rotation curves for other galaxies. You need both v and r to make a rotation curve v(r). We can measure v well for objects in the Milky Way, but r is difficult, since it folds in the uncertainty in the distance of Earth from the galactic center. For other galaxies, this is not a problem. See for instance astro-ph/0603143: "Surprisingly, the two nearest massive galaxies, the Milky Way (MW) and M31 (at an adopted distance of 780 kpc from McConnachie et al. 2005), have very poorly defined RCs. Our position inside the Milky Way’s disk makes it very difficult to interpret the HI outside the solar radius [...]" --Amble (talk) 01:45, 1 December 2008 (UTC)

warp in the disk of the Milky Way

The text: would explain the previously mysterious warp in the disk of the Milky Way by the interaction of the Large and Small Magellanic Clouds and the predicted 20 fold increase in mass of the Milky Way taking into account dark matter. is unclear to me. Does it mean that the "interaction of the Large and Small Magellanic Clouds" also accounts for "the predicted 20 fold increase in mass "? Or is the part of the sentence after "and the" constitute a partially formulated additional idea? Brews ohare (talk) 16:45, 8 December 2008 (UTC)

Dark chemistry ?

If dark matter exists, we must suppose the existence of a dark chemistry. It is likely that in the future, there may be an article on such a hypothetical chemistry. 69.157.229.14 (talk)

Dark matter in the Earth?

What is known about dark matter within the Earth? Some upper limit must have been determined on the amount - if nothing else, it doesn't pile up past the mundane surface or else the space program would have been in trouble. ;) I suppose only cold dark matter is eligible to stay in such a confined space? Wnt (talk) 00:44, 17 December 2008 (UTC)

Shape of galactic dark matter

Sometimes I've seen illustrations that seem to suggest that a planar, rapidly revolving spiral galaxy would have a nearly spherical cloud of dark matter surrounding it. Is that so, or does the dark matter have a distribution reflecting an equivalent angular momentum? Wnt (talk) 00:44, 17 December 2008 (UTC)

I'm no Scientist

But using Occam's Razor, isn't it much more likely that the "Virial Theorem" was just flawed? If I'm reading this right, when scientists applied their theorums and formulas to the real world they found that they weren't getting the results they thought they would, so rather than review their long accepted theories, they invented an invisible omnipresent entity to explain how the world works. Ironic, coming from scientists. 69.3.84.236 (talk) 14:52, 5 January 2009 (UTC)

This and the above are probably deletable forum chatter, but I should say that the point is that people didn't understand why a theory didn't seem to add up. If you come up with a theory that seems to explain many things and then it doesn't work on others, you have to fix it - you have to figure out what's wrong and by how much. So decade after decade people figured out what the theory said had to be there, how to measure it - all the while not having any "faith" that it really existed - and then finally deciding that there was some consistent evidence to support it existing after all. Really, science is full of invisible entities deduced by indirect means - atoms, germs, radiation, magnetic fields, (formerly) the rotation of the earth and such - and people have had to go through all this every single time. Wnt (talk) 16:30, 8 January 2009 (UTC)

Introduction should mention alternatives

Dark matter is not universally accepted as even being something that exists. There is a section about alternative explanations in the article. But the introduction makes no mention of this. The possibility that dark matter does not exist should be mentioned in the introduction - this is a key attribute of dark matter.