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On rationalised and reduced Planck units

The article seems to imply that the only difference between standard Planck units and "alternative" Planck units is that the base unit of mass is divided by a factor of √(4π) for rationalised Planck units, and by a factor of √(8π) for reduced Planck units, with any other, consequent difference (e.g. between the standard vs. alternative Planck units for force and energy) being exclusively a result of this difference in the base unit of mass (e.g. = ×÷² and = ײ÷², so = /√(4π), = /√(8π), etc). However, if you run the numbers as a system of equations where the other four equations (c₀ = 1 /, ε₀ = 1 ²²/³, ħ = 1 ²/ and k_B = 1 ²/²) remain constant and only one equation changes (from standard G = 1 ³/² to rationalised G = 1/(4π) ³/² or reduced G = 1/(8π) ³/²), you find that, while indeed the end value for the base unit of mass is divided by √(4π) or √(8π) as the article claims, the end value for the base unit of temperature is also divided by the same factors, while the end values for the base units of length and time are in turn multiplied by them, which causes a chain shift in the derived units one could not predict by simply replacing the mass unit (e.g. while the units for speed and energy vary as would be expected, the unit for acceleration is also divided by a factor of √(4π) or √(8π), so the unit of force is consequently divided by a full 4π or 8π instead). Isn't it the case that perhaps the article should explicitly mention that? E.g. instead of just saying that, in the reduced Planck unit system, the base unit of mass is divided by √(8π), wouldn't it be better if it said that, in the reduced Planck unit system, the base units of mass and temperature are divided by √(8π), while the base units of length and time are multiplied by √(8π)? 186.223.215.50 (talk) 02:29, 11 May 2022 (UTC)

Meaning of Planck mass/energy

I'm just listening to Leonard Susskind's lectures and he says the planck mass is equal to the mass of the smallest possible black hole. I suppose he should know what he is talking about, but I'm not an expert in the field, so I will not add it. Considering that there is some explanation for the signifance of the other units, it might make sense to add that to the Planck energy subsection, though. The significance of the unit was a natural question that came up in my mind right away anyway. OdinFK (talk) 16:53, 26 July 2022 (UTC)

The page already says that it has been speculated that may be an approximate lower limit at which a black hole could be formed by collapse. We could potentially elaborate here or there; of course, it's hard to say how much detail we should go into when the whole topic is so speculative. XOR'easter (talk) 18:56, 26 July 2022 (UTC)

Thanks for the answer. The problem was actually, that I was looking in the wrong place. I was expecting a comment about the significance in the subsection titled Planck Energy. In comparison the first sentence of Planck length immediately gives a picture of its (assumed) physical relevance. Anyway, maybe it's better the way it is, just a suggestion on my part to experts because it baffled me a bit. OdinFK (talk) 07:43, 27 July 2022 (UTC)

Thanks for commenting! This is one of those topics where it can be hard to find the right spot to put a statement, because all the units are conceptually interrelated. The mass of a black hole determines its radius, so talking about a minimum mass is the same as talking about a minimum radius. My own feeling is that it's simplest to say "Planck scale", which covers all the bases, as it were. XOR'easter (talk) 17:57, 27 July 2022 (UTC)

"Normalized" constants

My wording was an attempt at improving historical correctness. As implied by Tercer, my wording might be clumsy/inscrutable, but at least it was not incorrect, which the alternative of suggesting setting the constants to 1 would be. Stoney, if you read his paper, was apparently mindful of remaining dimensionally correct, and used symbols for his units of length, time and mass. This was unfortunately complicated by his treatment, which reflected the usage of the time of what one could term the Gaussian system of quantities, in which the force equations of electromagnetism omitted what is now would be called the Coulomb constant, thus treating that differently. One could gloss over that and just say that he chose his units such that the numeric part of G, c, e and k_e were 1 when expressed in terms of these units. However, the concept of "normalizing/setting these constants to 1" appears to have been completely absent, but is only too prevalent in WP (and, I guess loved by some contemporary particle physicists). Is there a way of wording this so that it is in fact correct and "clear"? —Quondum 17:21, 7 October 2022 (UTC)

How about "Stoney chose his units so that G, c, and the electron charge e would be numerically equal to 1"? On a different note, I think we should remove the "cosmological constant" and "Hubble constant" rows from Table 3 until the cosmologists get the Hubble tension all figured out. (Or at least we should avoid the spurious appearance of precision that the figures we currently quote imply.) And I'm not sure we need Table 4 at all; "equations that include constants look simpler when those constants are set to 1" is not particularly edifying. One or two examples in prose would be better, I think. XOR'easter (talk) 17:29, 7 October 2022 (UTC)

The issue is that everyone understand what it means to set the constants to 1, and that was indeed Stoney's go. I don't think being technically correct will help the reader. Nor am I a fan of a historical approach to physics, which is usually more confusing than an anachronistic explanation. Tercer (talk) 17:46, 7 October 2022 (UTC)

How do reliable sources explain what Stoney did? JBL (talk) 17:46, 7 October 2022 (UTC)

XOR, I would be happy with your wording: simple, and would be interpreted to mean the same as I said (minus the subtlety about k_e, which Stoney evidently did not even consider: it was implicit in the equations that he used, and is a retrospective commentary for clarity, not needed in a historical account).

Tercer, I have no idea what you mean by "that was indeed Stoney's go". Anyhow, I am not objecting to your objection to my wording and would be happy with understandable simple alternatives. I do object to the statement that "everyone understand what it means to set the constants to 1", though. I would suggest that this is nearly manifestly untrue amongst WP readers, and to me it is thoroughly ambiguous: it could mean defining the units so that the constants are numerically 1, or it could mean defining the quantities involved so that they are mathematically 1 (and hence dimensionless) through a process of nondimensionalization. These are not the same.

JBL, you can read the paper by Stoney himself, which is a ref that I added in the diff linked at the start of this thread: On The Physical Units of Nature, The Scientific Proceedings of the Royal Dublin Society, 3, 51–60, 1883. It is a bit of a read, but I think it is fair to use it as a source for what Stoney did.

—Quondum 18:16, 7 October 2022 (UTC)

Sorry, that was a typo, I meant to say "that was indeed Stoney's goal". I don't think it is ambiguous what it means to set the constants to 1, the only sensible interpretation is choosing units that makes the constants numerically equal to 1. Moreover, Stoney's paper is not a good source on what Stoney did, see WP:PRIMARY. A good source is a paper by someone else analysing Stoney's work. In any case, I'm also happy with XOR's wording, so there is no need to argue. Tercer (talk) 18:43, 7 October 2022 (UTC)

Indeed there is no need. We seem to have a mutually agreeable result —Quondum 18:59, 7 October 2022 (UTC)

remove the "cosmological constant" and "Hubble constant" rows from Table 3

XOR'easter, I'm afraid your comment above, "I think we should remove the "cosmological constant" and "Hubble constant" rows from Table 3 until the cosmologists get the Hubble tension all figured out. (Or at least we should avoid the spurious appearance of precision that the figures we currently quote imply.)", got ignored. I agree. These entries seem to belong as much as any of the others and are only needed for order-of-magnitude illustration, so my inclination would be to reduce these to one significant digit with a preceding tilde rather than to remove the entries altogether. I have no strong feeling on this, though. —Quondum 21:37, 7 October 2022 (UTC)

I have no objection to trimming to 1 significant figure (e.g., "${\displaystyle \approx 10^{-122}}$" or what-have-you). XOR'easter (talk) 16:42, 8 October 2022 (UTC)

I might call that 0 significant figures (or order-of-magnitude), which feels right for the context, and matches about how it often seems to be expressed in this sort of context. Done. —Quondum 17:08, 8 October 2022 (UTC)

Semi-protected edit request on 24 October 2022

This edit request has been answered. Set the |answered= or |ans= parameter to no to reactivate your request.

Ann Guy BillyGuy1234 (talk) 01:06, 24 October 2022 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. Cannolis (talk) 01:16, 24 October 2022 (UTC)

Derived Electric Units

I would like to propose adding a table of planck units extended to the electric domain with the elementary charge. WalkingRadiance (talk) 14:12, 2 November 2022 (UTC)

I realize that the electric units aren't used that often but maybe they should be included. WalkingRadiance (talk) 14:16, 2 November 2022 (UTC)

I disagree on multiple grounds.

1. Electrical units were not part of in Planck's original version.
2. There are multiple versions depending on the choice of electrical constant. There is no definitive version.
3. Derived electrical units have no clear relevance in the Planck scale context.
4. We have had this argument before about derived units. Editors have extensively edit warred about it. This resulted in indefinite blocks and the derived units being removed.
5. Adding a whole list "nice-to-have" unused derived units is not what Misplaced Pages is for. The motivation "maybe they should be included" is not good enough here.
6. We don't have references. Individual papers using these units do not constitute a reference that these are units in general use.

—Quondum 15:47, 2 November 2022 (UTC)

About the previous arguments, see for example Talk:Planck_units/Archive_5#Planck_impedance_missing, Talk:Planck_units/Archive_4#Recent_expansion,_lack_of_sourcing_and_many_new_redirects and Talk:Planck_units/Archive_4#Named_Planck_units. Tercer (talk) 16:15, 2 November 2022 (UTC)

I realize this was not part of Planck's original set of units so maybe they don't belong in the article Planck units.

I think this could be added to article on natural units though. WalkingRadiance (talk) 20:01, 2 November 2022 (UTC)

Why do you think it belongs in Misplaced Pages? Talk:Planck_units/Archive_5#Planck_impedance_missing (linked by Tercer above), discusses this idea, and in particular, mentions that including lists of stuff anywhere in article space that is cute but has no encyclopedic value violates WP:INDISCRIMINATE, which, being policy, is stronger than a guideline. I find it difficult to imagine why what you are suggesting would not be covered by this policy.

Since you mention an article on natural units, we do have Natural units, which lists notable systems of natural units with a brief overview of each. You'll see that as a higher-level coverage of the topic, inclusion of low-level detail would be even more out of place there, even if it had a place in Misplaced Pages. What you seem to want is an article along the lines of Speculative extensions of some natural systems of units or Possible extensions of Planck units, which are quite clearly impermissible topics. —Quondum 21:35, 2 November 2022 (UTC)

I agree with all six of Quondum's points enumerated above, and I also agree that other articles would be an even worse place to include derived-unit-cruft than this article is. Sorry for sounding grumpy, but this article has a long history of suffering from irrelevant tangents, unsupported speculation, and people wanting to reshape physics rather than document the subject how it is. XOR'easter (talk) 13:30, 3 November 2022 (UTC)

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