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Talk:Hubble's law

Former good article Hubble's law was one of the Natural sciences good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones
Date Process Result
January 22, 2006 Good article nominee Listed
September 5, 2009 Good article reassessment Delisted
Current status: Delisted good article
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Doppler/redshiftEdit

This article defines the Hubble law in terms of Doppler shift, but it properly ought to be redshift or cosmological redshift. While cosmological redshifts and Doppler redshifts are observationally indistinguishable, they have very different causes. Thinking of it in terms of Doppler effect leads to problems. For instance, Doppler shifts greater than the speed of light are not possible, but cosmological redshifts greater than the speed of light are.

74.142.32.130 (talk) 11:47, 5 January 2016 (UTC) Danny Faulkner

In the "combining redshifts" section, it states that it's not actually a Doppler shift, but I can see how just reading the lead may be confusing. Primefac (talk) 15:31, 5 January 2016 (UTC)

Hubble acceleration scaleEdit

I've seen in various astrophysical papers[1][2] mention of the "Hubble acceleration scale" a0 = cH06.59×10−10 m/s2. I'm guessing this is the gravitational acceleration requires to bind objects together against Hubble expansion, but all the sources I can find are rather technical and don't have a good WP-level explanation of the significance of the number.

It sould definitely be nice to have a subsection on this value. Has anyone got a simple explanation? 71.41.210.146 (talk) 23:36, 11 November 2016 (UTC)

How did Hubble determine distances?Edit

I can't see where this is mentioned here or in the linked articles. — Preceding unsigned comment added by Keith McClary (talkcontribs) 05:19, 2 December 2016 (UTC)

Keith McClary, see Hubble's_law#Cepheid_variable_stars_outside_of_the_Milky_Way. Primefac (talk) 12:46, 2 December 2016 (UTC)

Correction of Hubble law by German astronom Walter BaadeEdit

The observations of German astronom Walter Baade led him to define distinct "populations" for stars (Population I and Population II). The same observations led him to discover that there are two types of Cepheid variable stars. Using this discovery he recalculated the size of the known universe, doubling the previous calculation made by Hubble in 1929.[1][2][3] He announced this finding to considerable astonishment at the 1952 meeting of the International Astronomical Union in Rome.

--AustEngla (talk) 00:25, 11 December 2017 (UTC)

  1. ^ Baade W (1944) The resolution of Messier 32, NGC 205, and the central region of the Andromeda nebula. ApJ 100 137-146
  2. ^ Baade W (1956) The period-luminosity relation of the Cepheids. PASP 68 5-16
  3. ^ Allen, Nick. "Section 2: The Great Debate and the Great Mistake: Shapley, Hubble, Baade". The Cepheid Distance Scale: A History. Retrieved 19 November 2011. 
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