Talk:Dark matter

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 the 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)

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) 23:17, 31 January 2013 (UTC)