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This article may be too technical for most readers to understand.(September 2010) |
This business of the Hubble factor still decreasing needs some explanation. What I came to realize is that a, as the scale factor, determines whether there is an acceleration or not. Beynod that, the Hubble factor will decrease even with q=0 since as the universe gets bigger the galaxies moving away at a given rate get farther away. Hence the decrease. That the Hubble factor is still decreasing indicates that this is not a rapid expansion. In any case, some explanation of this is needed in the article. -- EMS | Talk 04:04, 12 August 2006 (UTC)
Your first point completely baffles me. Have you looked the article itself, where the Hubble parameter is defined and wikilinked? What more of an explanation are you after? -- Michael C. Price talk 18:21, 12 August 2006 (UTC)
Regarding the second point, that can only be explained by presenting the equations, which show that the sign of q and the sign of are independent.
Regarding the third point, I have no idea of its significance.
If you find my explanation confused them please expand it. But statements in the literature that the cosmic expansion is accelerating do beg the question of how this can be compatible with H still decreasing. This is what I have tried to address in this article.-- Michael C. Price talk 18:45, 12 August 2006 (UTC)
I gave rewriting the page a shot to make it a little clearer. Essentially, once you have defined q – which isn't used that much any more, I think – the page has served its function, and anything else is icing. It will never be an extensive article, like dark energy. – Joke 03:05, 14 August 2006 (UTC)
For editors coming from the redirect at accelerating universe, there is no clue in this article as to why they have been redirected here. This version of accelerating universe at least contained some explanation of what observations were driving the theory. This article, in contrast, is poorly written and even talks about "recent measurements of dark energy". Dark energy hasn't been measured at all. It's dark, after all. What have been measured are supernovae and the microwave background. This article requires some serious attention and correction in order to make it useful for readers who have come here because they have wanted to know about an accelerating universe. Uncle G 16:11, 15 November 2006 (UTC)
.-- Michael C. Price talk 13:10, 16 November 2006 (UTC)
Made the suggested changes. Also pointed cosmic acceleration at accelerating universe. -- Michael C. Price talk 21:53, 16 November 2006 (UTC)
Why is the parameter not mentioned on related pages such as Friedmann equations or Ultimate fate of the universe. Is it not a relevant parameter in cosmology anymore? It is still mentioned on the page for Hubble's law though.
Also, the units don't match up in . Looking at the version on Friedmann equations: (which confusingly uses the mass density rather than the energy density), it looks like the equation on this page is missing a factor of 1/c^2:
Also, where is the Λ term? Why is it also not included too? AndreRD ( talk) 17:41, 9 September 2015 (UTC)
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
This article may be too technical for most readers to understand.(September 2010) |
This business of the Hubble factor still decreasing needs some explanation. What I came to realize is that a, as the scale factor, determines whether there is an acceleration or not. Beynod that, the Hubble factor will decrease even with q=0 since as the universe gets bigger the galaxies moving away at a given rate get farther away. Hence the decrease. That the Hubble factor is still decreasing indicates that this is not a rapid expansion. In any case, some explanation of this is needed in the article. -- EMS | Talk 04:04, 12 August 2006 (UTC)
Your first point completely baffles me. Have you looked the article itself, where the Hubble parameter is defined and wikilinked? What more of an explanation are you after? -- Michael C. Price talk 18:21, 12 August 2006 (UTC)
Regarding the second point, that can only be explained by presenting the equations, which show that the sign of q and the sign of are independent.
Regarding the third point, I have no idea of its significance.
If you find my explanation confused them please expand it. But statements in the literature that the cosmic expansion is accelerating do beg the question of how this can be compatible with H still decreasing. This is what I have tried to address in this article.-- Michael C. Price talk 18:45, 12 August 2006 (UTC)
I gave rewriting the page a shot to make it a little clearer. Essentially, once you have defined q – which isn't used that much any more, I think – the page has served its function, and anything else is icing. It will never be an extensive article, like dark energy. – Joke 03:05, 14 August 2006 (UTC)
For editors coming from the redirect at accelerating universe, there is no clue in this article as to why they have been redirected here. This version of accelerating universe at least contained some explanation of what observations were driving the theory. This article, in contrast, is poorly written and even talks about "recent measurements of dark energy". Dark energy hasn't been measured at all. It's dark, after all. What have been measured are supernovae and the microwave background. This article requires some serious attention and correction in order to make it useful for readers who have come here because they have wanted to know about an accelerating universe. Uncle G 16:11, 15 November 2006 (UTC)
.-- Michael C. Price talk 13:10, 16 November 2006 (UTC)
Made the suggested changes. Also pointed cosmic acceleration at accelerating universe. -- Michael C. Price talk 21:53, 16 November 2006 (UTC)
Why is the parameter not mentioned on related pages such as Friedmann equations or Ultimate fate of the universe. Is it not a relevant parameter in cosmology anymore? It is still mentioned on the page for Hubble's law though.
Also, the units don't match up in . Looking at the version on Friedmann equations: (which confusingly uses the mass density rather than the energy density), it looks like the equation on this page is missing a factor of 1/c^2:
Also, where is the Λ term? Why is it also not included too? AndreRD ( talk) 17:41, 9 September 2015 (UTC)