Talk:Hubble's law

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

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 92.23.182.12 (talk) 11:07, 12 April 2018 (UTC)

How to find the Hubble constant, the easy way.

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.

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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 (185.181.236.222 (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 discrepancy

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:87.188.202.42. - 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)

Do we rename article to Hubble-Lemaitre law?

We're getting into something of an edit war over the first sentence as of time of writing. Do we rename the article to Hubble-Lemaitre law? If so, we should not just amend the first sentence, we should move the article entirely. Banedon (talk) 23:24, 31 October 2018 (UTC)

No, per WP:COMMONNAME. That the IAU recommends to call the Hubble's law the Hubble–Lemaitre law, does not change what most people call it, or what it's best known as, and also overlooks the fact that people are free to ignore or follow the recommendation. Headbomb {t · c · p · b} 01:28, 1 November 2018 (UTC)

I just did a symbolic revert, should be banned for a few hours at least, to be in on this great semi-official recognition by the International Astronomical Union that the cosmology that describes the expanding universe was published and accredited to Georges Lemaitre two years before Hubble published. Finally. I'm biased on this, or else I'd put up the RM, but please, someone go ahead and RM the Hubble-Lemaitre law, so it could be discussed fully. Thanks. Randy Kryn (talk) 02:59, 1 November 2018 (UTC)

I'd hold off on the rename until it comes into common usage. Right now it most definitely is not. Praemonitus (talk) 03:16, 1 November 2018 (UTC)

Reverted WP:POINT-y revert by Randy Kryn back to the long-standing, massively dominant WP:COMMONNAME of the phenomenon. The IAU does not decide how physical laws are named. Headbomb {t · c · p · b} 03:16, 1 November 2018 (UTC)

That's what an RM would discuss, how soon after an inside-baseball rename should a Wikipedia article title be changed. Corporations do it all the time, and although the IAU isn't the sole factor to take into consideration it should carry its due weight (as when Pluto was knocked off its high horse as a planet). Should be an interesting discussion at some point. It may end up that the common name stays as the title but that the duo name be entered first as the first mention, followed by the common name, as the preferred option by several editors suggests. Randy Kryn (talk) 03:26, 1 November 2018 (UTC)

The difference with a corporation is that a corporation controls its own name, and a name change usually happens after an acquisition, merger, or rebranding. A physical law belongs to no one, and the current reflects that, despite Lemaitre having a claim of precedence to the law, Hubble was the one that convinced the world. Snell's law isn't renamed the Sahl's law for the same reason, Snell was the one that convinced the world. Headbomb {t · c · p · b} 14:54, 1 November 2018 (UTC)

Wait to see if this becomes common usage in astronomical literature. I expect that will happen, as astronomers do tend to follow (most) IAU recommendations, but it's not a foregone conclusion. WP:NAMECHANGES is designed for names of people, but seems to work just as well in this situation. Right now we should just list it as an alternative name. Maybe reassess in a year. Modest Genius ^talk 11:26, 1 November 2018 (UTC)

Astronomers tend to follow IAU recommendations where it is convenient. There are examples where such recommendations have simply been impractical. In 1989, the IAU has decided that the unit erg should no longer be used in scientific publications. I don't know any astrophysicist who cared about that recommendation.[1] Renerpho (talk) 04:34, 3 November 2018 (UTC)

Requested move 1 November 2018

Hubble's law → Hubble–Lemaître law – 78% of professional astronomers voted in support of renaming the law. JeanLucMargot (talk) 13:54, 1 November 2018 (UTC)

• No, per WP:COMMONNAME. The IAU does not have the authority to decide what physical laws are called, and until the world accepts their recommendation, neither should Wikipedia. Headbomb {t · c · p · b} 14:39, 1 November 2018 (UTC)
• Yes, per the recommendation of the IAU and the overwhelming support by the relevant community. - DVdm (talk) 17:10, 1 November 2018 (UTC)
• Yes per nom and DVdm (IAU and relevant community). Randy Kryn (talk) 17:16, 1 November 2018 (UTC)

References

• No —but possibly later when others actually start using the name a lot. At the moment "Hubble's law" seems to be used 1000 times more often, according to ghits. And the "Hubble–Lemaître law" is only reporting the name change vote and not actually using it yet. Graeme Bartlett (talk) 22:19, 1 November 2018 (UTC)
• Lean yes since it's the IAU and it represents the consensus of most astronomers. Similarly when the IAU redefined Pluto as a dwarf planet in 2006 we didn't adopt a wait-and-see-if-it-becomes-common stance. However I don't feel strongly either way. It's just a name, and it's obvious what is being referred to regardless of whether it's called Hubble's law or Hubble-Lemaitre law. Banedon (talk) 23:50, 1 November 2018 (UTC)
• Yes, per IAU recommendation. De wafelenbak (talk) 10:15, 2 November 2018 (UTC)
• Yes, per IAU recommendation. The Cosmology section of the International Astronomical Union (IAU) overwhelmingly voted in favor of the change. Following this vote, the IAU brought it to all members and they approved it by 78%. As such, the change has the support of both the very specialists and the overall community of professional astronomers. Most people still refer to it by the old name and they will do so for several years to come, but this is because of the inertia that names have in society. In my opinion wikipedia's role on scientific subjects is to provide accurate information of the views of the science community. — Preceding unsigned comment added by Thanassiskatsiyannis (talk • contribs) 14:12, 2 November 2018 (UTC)
• Oppose for now. The IAU's recommendation is important, but I would say that it is still Wikipedia's place to follow common usage rather than try to change that usage. If referring to it as the "Hubble–Lemaître law" gains wide usage following the IAU's recommendation, then we should change our title, but I think that changing it right away is premature. Dragons flight (talk) 15:39, 2 November 2018 (UTC)
• Oppose per WP:COMMONNAME. A comparison of ghits shows the overwhelming preponderance of usage is the current form. When that changes, we can move the article. Wikipedia serves everybody, not just the IAU. Praemonitus (talk) 15:42, 2 November 2018 (UTC)

• Of course the common name is the present title, and that won't change for awhile, especially if going by ghits. But long-term significance is more important here, and the proposed title fits that criteria. Randy Kryn (talk) 15:46, 2 November 2018 (UTC)

• Actually no, this is an encyclopedia of knowledge not a trend setter. It's here to document what is known, not to be a WP:CRYSTALBALL. Not every decision by an official board gets widely adopted. Until that happens, there's no reason to be premature. Praemonitus (talk) 16:02, 2 November 2018 (UTC)
• "Long-term significance is more important". You appear to be assuming the IAU's recommendation will actually come into wide usage and gain significance. That seems likely, but it is hardly a sure thing. I can think of examples in both geology and biology where leading bodies made naming recommendations only to abandon them some years later when it became clear that few people were actually following the stated preference. Hence, I think we should wait to see if the new usage is actually widely adopted. Dragons flight (talk) 15:58, 2 November 2018 (UTC)

• "That seems likely, but it is hardly a sure thing." It does not even seem likely to me. Astronomers tend to follow IAU recommendations where it is convenient. There are examples where such recommendations have simply been impractical. In 1989, the IAU has decided that the unit erg should no longer be used in scientific publications. I don't know any astrophysicist who cared about that recommendation.[2][3] Renerpho (talk) 04:42, 3 November 2018 (UTC)

• How many astrophysicists do you know? No astrophysicist I know still uses ergs (SI units have long taken over). Banedon (talk) 04:59, 3 November 2018 (UTC)

Speaking as an astronomer: everyone working in AGN/quasar physics. erg/s/cm^2/Hz is a *very* common unit of flux. - Parejkoj (talk) 15:58, 3 November 2018 (UTC)

Of course it depends on the field... But a Google search for Astronomer's telegram erg will provide you with an arbitrary number of examples; some of them [4] in recent IAU publications. Renerpho (talk) 14:56, 4 November 2018 (UTC)

• Oppose, per WP:COMMONNAME, and the fact that the IAU has no mandate to name physical laws.[5] The IAU resolution is a recommendation, nothing else, and it remains to be seen if it will catch on. Renerpho (talk) 18:49, 2 November 2018 (UTC)
• Wait, see my reasoning in the section above. Why was a new discussion started when one was already underway? Modest Genius ^talk 20:21, 2 November 2018 (UTC)
  • This section is a formal move request which brings outside eyes to the topic of renaming per WP:Requested moves process. -- Netoholic @ 21:03, 2 November 2018 (UTC)
• Oppose per WP:COMMONNAME and others above. Seems to be WP:TOOSOON. -- Netoholic @ 21:03, 2 November 2018 (UTC)
• Oppose per WP:COMMONNAME. Rreagan007 (talk) 01:09, 4 November 2018 (UTC)
• Yes. The majority of professional astronomers voted in support of renaming the law.