Talk:Comoving and proper distances

message: Shouldn't "the Universe" be capitalized when it refers to our Universe? David W. Hogg 00:59, 24 September 2005 (UTC)
thread_title: Universe or universe"

message: Can someone translate this to Simple English?
: Yes, PLEASE!  This article is even more unfathomable than most scientific ones in Wikipedia.  And that's saying something.
::"General relativity is also a local theory, but it is used to constrain the local properties of a Riemannian manifold, which itself is global. In the context of general relativity, the assumption of Weyl's postulate is that a favoured reference frame in space-time can be decided."
:Gawd almighty.
:: Don't know if it's any better now, but I tried :-). I also tried to correct a boatload of technical errors.  BTW, the above example was just pure techno-babble (in my opinion). Pervect 04:23, 21 August 2006 (UTC)
thread_title: Speak Simple English!!!

message: This article could still use attention by an expert, but, couldn't any article?
My perception of the "expert tag" is that it should be applied to articles with technical issues, such as articles written by enthusiastic amateurs that need revision for factual accuracy.
This article previously had that exact problem. I think that I have now eliminated most of the factual problems with it, though there is certainly a lot that could be done to expand and refine the article.  Most of the formulas are presented without motivation or derivation, for instance.
Pervect 21:00, 21 August 2006 (UTC)
replies: text: Oh wait, it shouldn't be that hard to compare them.  I've reminded myself of the "compare selected versions" feature.Kmarinas86 05:03, 30 August 2006 (UTC)
thread_title:  Expert tag philosophy 

message: The discussion/formula  on distances is not entirely correct... and so probably confusing to some non-expert readers.
I think the suggestion that there should be some kind of notions of distance in cosmology page is a good one.  The situation with the distance measures pages is kind of confused and disorganized, I think.  There is now a page on Distance measures (cosmology) and a redirection from notions of distance in cosmology.
Hopefully this means that each of the pages on individual distance measures can now focus on the distance measure themselves (for example, should the comoving distance page really be defining the other measures and giving formulae for the proper motion distance?) and the Distance measures (cosmology) page can describe the overall idea and the relations between measures.  
Specifically, I think a bunch of the material in the "other distances used in cosmology" might be better suited to the new page, since it discusses things beyond the scope of the title of this article.  Does this sound good? Wesino 10:16, 22 November 2006 (UTC)
replies: text: I noticed that the whole article was tagged with a "merge" into Distance measures (cosmology).  In my opinion this might be a bit much -- certainly comoving distance is important enough to have its own page?  I think that the comparison with other distance measures, though, should go on the distance measures page.  Any other opinions? Wesino 00:32, 6 December 2006 (UTC)
thread_title:  Notions of Distance in Cosmology page 

message: \chi = \int_{t_e}^{t} { c \; \mbox{d} t' \over a(t')}
Should there not be a "with respect to t" "dt" at the end of that? Like this:
 \chi = \int_{t_e}^{t} {c \; \mbox{d} t' \over a(t')} \; dt ?
Stuart Morrow 19:03, 26 February 2007 (UTC)
replies: text: I think it's with respect to  \; dt'Wolfmankurd 21:59, 8 May 2007 (UTC)
thread_title:  Equation 

message: What do the te and t refer to? The integration is performed along a path of constant cosmological time, so they can't refer to cosmological time (unless all distances are identically zero, which makes for a useless definition). —The preceding unsigned comment was added by 155.148.10.80 (talk) 19:56, 25 April 2007 (UTC)
thread_title:  More on Distance Equation 

message: In the integral defining the comoving distance, what does c denote? It appears in the equation without any explanation. Is it the speed of light? -99.242.17.45 (talk)  —Preceding undated comment added 03:06, 24 January 2010 (UTC)
thread_title:  Question Re Distance Equation 

message: I've added a layman-accessible summary to the lede. Among other things, we get questions about what "comoving distance" is every couple of months at quasar, with complaints that this article isn't helpful for describing that. The lede should fix that.
I realize that the description is approximate. This is intentional, for the sake of simplicity, and noted in the lede.
Per the other threads on this talk page, it's possible that my edit (and the quasar article) should use the term "proper distance" instead of "comoving distance". I don't have sufficient expertise to settle that question in the above thread; I suggest bringing it to the attention of the people at WT:AST to get it resolved (and to propagate corrections to other articles if changes are needed). --Christopher Thomas (talk) 21:03, 17 July 2010 (UTC)
thread_title:  Layman summary added to lede 

message: \chi =
\begin{cases}
\sinh^{-1} r , & \text{if } k=-1 \ \text{(a negatively curved ‘hyperbolic’ universe)} \\
r ,                  & \text{if } k=0 \ \text{(a spatially flat universe)}  \\
\sin^{-1} r ,   & \text{if } k=1 \ \text{(a positively curved ‘spherical’ universe)}
\end{cases}
1) I think that sin/h^-1 is better expressed as arcsin/h.
2) arcsin/h() does not accept metric argument values; arcsin(1 meter) is meaningless.
I assume that the intended expressions would rather be R×arcsinh(r/R) and  R×arcsin(r/R), respectively.
Hilmer B (talk) 21:02, 6 November 2016 (UTC)
replies: text: In the coordinate system being used here, r is normalized by the curvature of the manifold and therefore dimensionless – this is exactly what you have typed, but in the article's equations r = r'/R  where r' is the dimensionful radial coordinate. I think a better indication of this would be useful in the article, though. Dylancromer (talk) 17:19, 26 September 2017 (UTC)
thread_title:  Equation requiring a clean-up: 

message: — Preceding unsigned comment added by 2A02:2149:8769:F400:A82C:4E97:EBEE:1488 (talk) 14:12, 27 February 2018 (UTC)
thread_title:  Please translate the page