Talk:Quasar/Archive for 2013

How To Reconcile Age of Universe vs. Quasar Distance?

The article states that one quasar's distance as measured in 2011 was some 29 billion light years. But there is no mention of how this is reconciled with the currently posited age of the universe which is a mere 13.5 billion years. Tmangray (talk) 20:09, 13 January 2013 (UTC)

See the article on Proper Distance, which is linked just before that statement. - Parejkoj (talk) 18:14, 14 January 2013 (UTC)

I'm afraid that doesn't explain it at all. Either the explanation is inadequate, or there exists a real discrepancy. Tmangray (talk) 18:31, 14 January 2013 (UTC)

You might be confusing age with size. For more of an explanation, see Observable universe.--Larry (talk) 04:58, 15 January 2013 (UTC)

Sorry about that, the link in the article is titled Proper Distance, but it is a link to Comoving Distance, as it should be (the discussion of proper distance is better in the comoving distance article... go figure!). This has come up several times before, but this article is correct: the proper distance to a z=7 quasar is ~29 Gly. The distance is larger in ly than the age of the Universe in years, because the Universe has expanded since the light originally left the object. I suppose we should have some comment to that effect in the article? - Parejkoj (talk) 17:41, 15 January 2013 (UTC)

That doesn't make sense. Even if it would have expanded at light speed, the distance should be maximum 2×13.77 ≈ 27.5 billion light years. Or is the universe expanding faster than speed of light? 82.141.95.124 (talk) 10:35, 21 January 2013 (UTC)

Yes, some objects are effectively moving away from us faster than the speed of light: that's the beauty (and confusion!) of general relativity. The "motion" in this case is the expansion of space itself (e.g., an increasing metric), not what you normally think of as "motion". The "edge" of the universe (redshift infinity) is ~46 billion light years away in comoving coordinates. There is more discussion about this at Metric Expansion of Space, which I will link from the contentious section of this article, since this keeps coming up. - Parejkoj (talk) 15:51, 21 January 2013 (UTC)

Time dilation

Is there a specific reason that this isn't in the article?

http://mnras.oxfordjournals.org/content/405/3/1940

http://arxiv.org/abs/1004.1824

http://iopscience.iop.org/1538-4357/553/2/L97/fulltext/

Paradoctor (talk) 19:09, 14 October 2013 (UTC)

Yes: (a) the article can't describe everything that everyone has ever observed about quasars, and (b) there's no consensus that it's correct. Mhardcastle (talk) 07:42, 15 October 2013 (UTC)

(a) We are an encyclopedia, and this is research published in reputable peer-reviewed scientific journals.

(b) Lack of scientific consensus is not a reason for exclusion. Furthermore, to establish lack of consensus in this matter, we need either sources saying so outright, or papers attacking Hawkins' position. I'm not aware of either, maybe you can help me out here? Paradoctor (talk) 08:34, 15 October 2013 (UTC)

(a) Literally thousands of articles about quasars are published in peer-reviewed journals every year. We can't include everything that all of them say.

(b) Lack of consensus is a reason for excluding material in an article which necessarily has to summarize a huge literature. For arguments against Hawkins' work see e.g. Baganoff & Malkan (1995) ApJ 444 L13. Mhardcastle (talk) 19:46, 18 October 2013 (UTC)