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Talk:Hubble's law

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.
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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.

Is it possible to have the value of the constant in a different form?Edit

On science shows like 'Cosmos' etc, when they say "if the nucleus was the size of a marble, the stadium size would be the electrons cloud" type of thing? Just a bit more graspable than a megaparsec. The best I got so far was something like, space expands (approximately) 1mm for every 75 million kilometers, per hour? If I did that right. For us laypeople :) just a thought thanks (talk) 11:07, 12 April 2018 (UTC)

How to find the Hubble constant, the easy way.Edit

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

The furthest we can see (in theory) is 13.8 billion light years, the Universe being that old.

Divide that up into megaparsec sections (of 3.26 million light years) and that comes to just over 4,233 sections.

At the furthest point, redshift is light speed as in 298,051 kms per second.

Divide 298,051 by just over 4,223 and you get 70.409 kms per second per megaparsec, the Hubble constant for expansion ( (talk) 15:39, 18 August 2018 (UTC))

Are you suggesting that this is an easy way others missed? That'll give one an average over the history of the universe if you already know the age, but working backwards from the age of the universe doesn't contribute anything new, as the age itself was determined partly from the methods you may think you're shortcutting. H has also varied over time, so using the relationship between the age and the apparent recession of the CMB is actually complicated by the need integrate the function over the period. The speed of light (c) is actually 299,792 km/s and redshift (z) is a measure of wavelength; perhaps you're talking about the the fact that for a z of 1100, the recession velocity is 0.9999983501099652 * c, but that's still 299791.963375, so I'm confused as to where your "298,051" figure is from. —Undomelin (talk) 22:46, 17 September 2018 (UTC)
There is now a very simple way to calculate Hubble’s Constant, by inputting to an equation, the numerical value of Pi and the speed of light (C) from Maxwell’s equations, and the value of a parsec. NO space probe measurements (with their inevitable small measuring / interpretation errors) are now required. Hubble’s Constant is ‘fixed’ at 70.98047 PRECISELY. This maths method removes the errors / tolerances that is always a part of attempting to measuring something as ‘elusive’ as Hubble’s Constant. This has very deep implications for theoretical cosmology.
The equation to easily and precisely 'fix' Hubble's Constant is 2 X a meg parsec X light speed (C). This total is then divided by Pi to the power of 21. This gives 70.98047 kilometres per sec per meg parsec. Its reciprocal is 13.778 BLY's.
This is known as ‘The Principle of Astrogeometry'. David. David Michael Hine (talk) 17:39, 19 September 2018 (UTC)
This is numerology and is physically meaningless. Headbomb {t · c · p · b} 17:50, 19 September 2018 (UTC)
So by your 'weird reasoning, Maxwell's equations and Relativity must also be 'numerology'? David Michael Hine (talk) 17:54, 19 September 2018 (UTC)
Please indent your talk page messages as outlined in wp:THREAD and wp:INDENT — See Help:Using talk pages. Thanks.
It doesn't really matter. If you have reliable sources (see wp:Reliable sources and wp:Secondary sources) where this is discussed, we might take something onboard in the article. Otherwise we cannot even discuss this here, and this discussion is off-topic. This talk page is for discussions about the article, not about the subject — see wp:Talk page guidelines. - DVdm (talk) 18:05, 19 September 2018 (UTC)
Both relativity and maxwell's equations have sound theoretical and experimental support. The above is just mashing numbers together until you get something close to the value. Headbomb {t · c · p · b} 18:08, 19 September 2018 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Hubble constant discrepancyEdit

I feel like there's enough material now about the discrepancy in measurements of the Hubble constant (CMB vs. astrophysics measurements) to have an independent article on it. Banedon (talk) 02:11, 24 September 2018 (UTC)

Agreed. The independent article, however, should also point to the fact that the Hubble diagram is mostly misinterpreted. To show the alleged proportionality of speed v and distance d (v1/d1 = v2/d2 = v3/d3 = H = constant) at least two measurement points of one and the same galaxy would be required. But the diagram shows only single measurement points of many different galaxies. These are scattered between the axes of the diagram, showing no order at all. The red middle line drawn in the diagram (by whom?) has no rational meaning whatsoever. It is not possible to deduce a constant H = v/d from the diagram. Ed Dellian2003:D2:9719:3088:2162:ED6F:B25B:D535 (talk) 16:30, 25 September 2018 (UTC)
The validity of Hubble's law isn't in dispute, only the precise value of the Hubble constant is. I don't think your comment is relevant. Also why would you need two measurements per galaxy? A single measurement, or multiple measurements of different galaxies at the same distance, is enough. Banedon (talk) 21:10, 25 September 2018 (UTC)
Since Hubble's asserted "constant", that is, the v/d of galaxies, is not really constant according to measurement, Hubble's law, which requires H to be constant, is of course at stake. This is why astronomers are desperated about the discrepancy in measurements of H. - Why two measurements per galaxy to see if h/d is constant? Because you need two measurement points at different times to see whether or not the quantity h/d changes in time, that is, whether or not the measurement points all the time will lie on the same straight line from the zero point to the measurement points. Only this outcome would indicate that h/d is constant. The "red line" added to Hubble's diagram tries to make the reader believe in such an outcome, but falsely. - Why do you speak of "multiple measurements of different galaxies at the same distance"? Would the distances of galaxies be the same - what would be the consequence? Actually the distances are different, of course, so it makes no sense to speak of "galaxies at the same distance". Ed Dellian 2003:D2:9719:3088:2162:ED6F:B25B:D535 (talk) 05:45, 26 September 2018 (UTC)
Hi Ed, your objections are off-topic here, as this is not the place to discuss the subject of the article. Here we can talk about the format and the structure of the article, and on adding/changing/renaming content, provided it is based on reliable sources. We cannot discuss (aspects of) the content here, based on our own opinions — see wp:Talk page guidelines. You can always ask at the wp:Reference desk/Science. For the origin of the (blue) line in the diagram of the section Hubble's law#Interpretation, see article Correlation. - DVdm (talk) 06:39, 26 September 2018 (UTC)
Thank you for this information. Please note that I do not discuss something "based on my opinions". It is not "my opinion" but a basic truth of mathematics that it is absolutely not possible to deduce a "law" from correlations of measurements of velocity and time, v/d, of different objects (this is corroborated by the article "Correlation"!). It is also a basic truth of mathematics that a v/d proportionality is simply impossible, since it would state that velocity increases instantaneously with space, which is not true: Everybody knows that velocity increases only in proportion to time. As a consequence, its proportion to distance is not linear v/d but a proportion of v to the square root of distance d. It is also not my opinion but a well-known fact that measurements of H since Hubble's time have always produced different values. Why did Hubble get an "age of the universe" of only 2 billions? Because he calculated it based on the data of quite "near" galaxies. Why do we get 14 billions today? Because we are using the data of the most distant galaxies which were not observable in Hubble's time. This fact demonstrates that the value of H depends not only on time but also on distance, so that H is certainly not a constant. You will know that the final conclusion is generally admitted, and even initially here! So I believe that the public should be informed not only about the fact of "discrepancy in measurements of Hubble's constant" but also about the consequences of H being a variable according to these discrepancies. Ed Dellian87.188.202.42 (talk) 14:23, 26 September 2018 (UTC)
Wikipedia is not here to inform the public of what you think is wrong with Hubble's constant. Wikipedia is here to report the current state of affairs in science, based on the established literature. Without a proper wp:reliable source your remarks and questions are off-topic here. I have put a second level warning at User talk: - DVdm (talk) 14:40, 26 September 2018 (UTC)
  1. "Since Hubble's asserted "constant", that is, the v/d of galaxies, is not really constant according to measurement, Hubble's law, which requires H to be constant, is of course at stake."
    Hubble's law does not require that H remains constant. This is clearly explained in the lead and elsewhere in the article.
  2. "This is why astronomers are desperated[sic] about the discrepancy in measurements of H."
    Astronomers aren't 'desperate' on this, there is no crisis about the validity of Hubble's law. The interest is because discrepancies are things of inherent interests to scientists, and understand the cause of the discrepancy and how to resolve it furthers knowledge and understanding of the world. The different methods make different assumptions, and knowing which assumptions need to be modified / which are invalid is of great interest.
Headbomb {t · c · p · b} 14:36, 26 September 2018 (UTC)
I have been discussing the matter with various experts. You are the first to assert that Hubble's law "does not require that H remains constant". O. k. That's your belief. It has nothing to do with science. Ed Dellian2003:D2:9719:3087:C027:F949:12FA:FD91 (talk) 17:07, 26 September 2018 (UTC)
Then I question the so-called 'experts' you've been talking to, because this is something covered in any introduction to astronomy/astrophysics class out there. Headbomb {t · c · p · b} 17:11, 26 September 2018 (UTC)

Back on topic, I don't see that the discrepancy merits more than a section in this article. I don't see the case that this is something so massively important that it needs more than that to adequately summarize and cover. Headbomb {t · c · p · b} 17:18, 26 September 2018 (UTC)

The discrepancy is quite big though, by several sigma. Whatever is causing it is a major headache for cosmologists, especially since this is a discrepancy in one of the most important parameters in Lambda-CDM. We have articles on other unsolved problems in physics, a similar one could be created for this. Banedon (talk) 07:29, 27 September 2018 (UTC)
Return to "Hubble's law" page.