Talk:Orders of magnitude (temperature)

SI Prefixes

This seems to be the only page on the internet using prefixes larger than "yotta" (10^24), all other sources suggest that the widely accepted range of SI prefixes ends at that point. —Preceding unsigned comment added by 50.47.106.228 (talk) 04:05, 2 May 2011 (UTC)

Planck temperature

Considering plank temperature is supposed to be the hottest temeprature that can be physically possible, why are there some entries as many as 3 order of magnitude higher? Rhialto 02:34, 4 April 2007 (UTC)

The Planck temperature corresponds with the Planck mass-energy of two bodies whose two level separations by gravital potential is equal to the wavelength of that potential. As gravity is rather weak, the mass of two motes and their attendant nearness must be rather strong. At that scale resonanses between gravity and elèctricity are sharp and coherent. It may be the greattest temperature that any body can hold with, say, elèctricity without interferent interactions, but it doesn't mean that it's the greattest possibil temperature. Above that temperature and below that length and span, interactions are "fuzzy" or "foamy" rather than nonexistent because all the forses are involved. There should be more energhetic harmònics yonder that scale. -lysdexia 07:38, 12 April 2007 (UTC)

List of significant temperatures merge

List of significant temperatures is orphaned and probably shouldn't exist. I've flagged it for merge into this page but I don't actually see any useful stuff in there that isn't already here. SteveBaker (talk) 03:41, 15 February 2009 (UTC)

I have to Agree. Besides, as SteveBaker said, most of the info is already on this page. Adam Hillman (talk) 12:07, 2 March 2009 (UTC)

No one objected, so I redirected List of significant temperatures to this article. The edit history of the page is still there, if anyone wants to copy more temperatures from that article to this one. Philbert^2.71828 22:42, 23 March 2009 (UTC)

extradimensional gauge freedom

What the heck is "extradimensional gauge freedom" supposed to be? I'm starting to think this term is made up. This article is literally the ONLY PAGE ON THE ENTIRE INTERNET with this phrase in it. Google it, there's only like 20 results all of which are asking "what the hell is that wikipedia temperature article talking about?".||bass (talk) 05:32, 21 February 2010 (UTC)

It was added on 2005-11-03T05:37:21, but I've removed it and added some more {{citation needed}} tags. -84user (talk) 10:40, 21 February 2010 (UTC)

At Planck temperature, two bodies will become gravitally bound and tend to shed excess internal energhy; when they are superheated, however, their mekanical energhy will become divergent or hýpervolic. In M- or brane theory the smallest limiting dimensions become open to such a body, where otherwise it would condense, cool, and be stuck here or there. In superstring terms, the body will become unbound to our brane, as a loop akin to the gravitòn's shape, and be keen to fare throuh other dimensions. -lysdexia 15:00, 23 September 2010 (UTC)

what does this mean

10−30 particular speeds bound paths to exceed size and lifetime of the universe (see least-energy in orders of magnitude (energy)) What does this mean? 137.122.45.191 (talk) 15:19, 6 April 2010 (UTC)

What is "particular speeds bound paths to exceed size and lifetime of the universe"?

The article says "particular speeds bound paths to exceed size and lifetime of the universe (see least-energy in orders of magnitude (energy))" as the entry for 10⁻³⁰. What is this supposed to mean? The article on orders of magnitude (energy) does not mention this at all and I can't find anything more about this anywhere. 137.122.149.229 (talk) 14:25, 13 May 2010 (UTC)

I think this entry was made up, as the only place I can find anything about it is this article and mirrors of this article, and I can't find anything more about what it is supposed to mean. 137.122.149.229 (talk) 14:24, 14 May 2010 (UTC)

It was not. At this temperature, a body's potential well is greater and its perihod longer than the univers. -lysdexia 15:00, 23 September 2010 (UTC)

Inconsistency

452.15 K 	179 °C 	354.2 °F 	mean surface temperature of Mercury
453.15 K 	180 °C 	350 °F 	oven at moderate temperature

How can 179 C be 354 F and 180 (more than 179) be 350 (less than 354)??? Screen317 (talk) 09:25, 8 September 2010 (UTC)

That's not exactly the problem here. The numbers are not properly approximated. It is beyond crazy to say that an oven at moderate temperature is EXACTLY 453.15!! That's just WAY too much precision! What has evidently happened is that the typical temperature of an oven is reasonably stated as 350F or 180C because we're rounding to the nearest 10 degrees. (350F is really 177C) But this is a horribly inexact measurement. I'm sure the temperature of the interior of a typical oven varies by at least 10C between bottom and top shelf - and no two ovens are going to maintain the temperature at the exact same value...and moreover, being thermostatically controlled, an individual oven will vary up and down by 10C. So 350F and 180C are perfectly OK. Of course 453.15K is just silly! Someone probably converted 180C to K and got that number. But it should be rounded to 450K. Sadly, that messes things up still further from your perspective.

Our article on Mercury states that the surface temps vary between 200K at the poles to 340K at the equator - and between 80K and 700K overall! So stating the average to a precision of one degree is also madness! Even though it might theoretically be possible to obtain a "mean temperature" - I VERY much doubt that it's known over the entire surface, in light and in shade, on dark rocks and light, over the entire Mercurian year/day, etc. So it too should be radically pruned in precision.

So - IMHO: 450K 180K 350F is the temperature of both an oven on "moderate" and the mean surface temp of Mercury. I'll edit accordingly.

SteveBaker (talk) 03:28, 9 September 2010 (UTC)

Urgh! Nearly all of the numbers in that table had stupidly high levels of precision. The fact that nearly all of the Kelvin numbers ended in '.15' strongly suggests that they were mindlessly converted from Celcius without thought for appropriate use of precision. SteveBaker (talk) 03:41, 9 September 2010 (UTC)

Planck temp inconsistent with http://en.wikipedia.org/wiki/Planck_temperature

On the planck temp page: http://en.wikipedia.org/wiki/Planck_temperature the value is given as about 1.42*10^32 K. On this page it is cited as 14.2 million YK, which to my understanding is 14.2*10^6 *10*24 = 1.42*10^31. Worse yet, on the magnitude side it says its on the order of 10^30, which is consistent with neither of the other values. That discrepancy makes me believe the number on this page is wrong. I brought this up under the other page's talk page also. Washyleopard (talk) 13:03, 17 July 2012 (UTC)

Encyclopædia Britannica - 1911

This rather old Ref. is used for some hard to understand strange claims at low temperatures. Low temperatures were rather new at this time, so this source is rather outdated to this respect. So I tranferred this strange part here for discussion an likely final removal:

Everyday substances near liquid air's temperature with incipient Fermi-condensate populations result in spontaneous luminescence, loss or lack of hysteresis, inductive and capacitive electronic moments that readily adsorb or expel or float upon unlike substances:--Ulrich67 (talk) 19:14, 28 July 2013 (UTC)

References

Paper 450F v. 450C

There was a "kindling point of paper" at 450C which I removed. It had a source citation but that may be bogus. There was and still is a paper entry at 450F, and Wikipedia's own Autoignition_temperature article has two sources saying paper's kindling point is 424-475F. This Slate article about the well-known "451F" temperature at which paper burns also backs this up. // 24.62.170.82 (talk) 00:43, 12 February 2016 (UTC)

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Absurdly vague examples

Some of the items in the list are risibly vague (and more than vaguely risible):

• Room temperature
• Food is well done
• Cake is well done
• Oven on low

And so on. These don't sit at all well with the more scientific, objective temperatures elsewhere in the list. Although it's useful IMHO to have familiar temperatures in a list like this, to balance the ones people can't really relate to, these are just far too woolly. Sorry that I don't have time to fix it right now; flagging it for someone else who may have the time later. 82.71.0.229 (talk) 14:01, 28 July 2018 (UTC)

What happened here?

This edit looks like it did something weird with indentation within cells. What wanted it to achieve? cyclopia^speak! 13:33, 24 September 2024 (UTC)

Unacceptable expression of sources/non-valid concept in sources

"Such a temperature, while formally negative in value, is hotter than every positive temperature - even infinite temperature"

This semantics of this statement isn't acceptable for the obvious reason that infinite is a maximal value which is non-transcendable. This is the first argument. After this argument it is obvious to realize with regards to the first considerate - the first considerate being = is it possible to be hotter than infinite?: in the laws of nature it isn't possible, but perhaps it is possible in quantum states with exotic matter. This answer to the problem is a mistake resulting from the presentation of the problem if or not hotter than - when in the first instance: infinitely hot isn't possible - which is the immediate negation of the possibility of there being any problem if/not hotter. @Cyclopia: Onemillionthtree (talk) 11:18, 21 February 2025 (UTC)

I'm sorry but you simply do not understand the topic. There is nothing "unacceptable" about a negative temperature system "being hotter than infinite", it simply means that a system with negative temperature will always cede heat to any system with any positive temperature. It does not mean you have to reach a positive infinite temperature before. This is a physical explanation. cyclopia^speak! 16:06, 21 February 2025 (UTC)

I think the scientists must have made an error resulting from comparing the values of the physics of changes of exotic matter with natural matter. In a mathematical understanding the scientists consider it is possible to imply range beyond the maximal natural range which they have previously considered is infinity. https://en.wikipedia.org/w/index.php?title=Orders_of_magnitude_(temperature)&direction=prev&oldid=1276284439: Hypothetical temperature not realizable in experimental conditions because ...energy input to a system to arrive at the temperature approach infinity. Onemillionthtree (talk) 11:44, 21 February 2025 (UTC)

If you think scientists have made a mistake, the place to discuss that is the scientific community, not Wikipedia. cyclopia^speak! 16:06, 21 February 2025 (UTC)

There is no real controversy on negative temperatures, and if there were, they do not belong on a sentence before the table

Onemillionthtree keeps adding a sentence (see e.g. this diff) stating that the concept of negative temperature is somehow controversial. There are some problems with this:

1. The concept of negative temperature is established since 1949 and it is overall accepted in thermodynamics. Academic manuals on thermodynamics routinely introduce the concept.
2. The source used in the edit acknowledges that there was some controversy on the topic in the 2010s, but it fixes that (and subsequent sources do the same, e.g. [1], also much more recently: [2].) It does not seem to me that there is a major scientific controversy: some authors have put some doubts on the validity of the concept but they get rebuked by multiple authors. It is pretty normal that the scientific literature challenges concepts, it doesn't mean they are fundamentally debated.
3. Even if there were a substantial controversy on the topic, a lonely sentence on top of this table is not the right place to include it. Discussion of the controversy, if necessary, can go to the main article on the topic. A lonely sentence sticked there is not the way to fix this issue (if there is an issue).

cyclopia^speak! 16:22, 21 February 2025 (UTC)

I disagree with this claim. I agree that negative thermodynamic temperatures are an established mainstream concept. But it is also completely clear from the citations required to establish this concept that it is not equivalent to many of the other entries in the table. Placing these negative thermodynamic temperatures in the same table as the other say cosmological temperatures is a form of synthesis that does not reflect the mainstream concept of temperature. Johnjbarton (talk) 18:13, 28 February 2025 (UTC)

The controversy is that the papers claiming negative temp may have made an off-by-one error in computing the entropy. There are several ways of defining the entropy, which apparently lead to off-by-one errors. This normally doesn't matter at all when you have N = 6 x 10^23 particles, but does matter when there are N = 100 states. There was a back-n-forth sequence of articles and rebuttals in Phys. Rev. Lett. trying to resolve this off-by-one error. When I last looked at it, it really did seem to be an off-by-one, and if you changed the N to N+1 you really did go from a negative temp to a small but positive temp. Unless you have proof that the controversy has gone away, and everyone has reached consensus on this topic, then I'll say "I don't believe it". Have you actually read through the PRL letters? (I did.) Did you understand what they were saying? (I did.) Can you articulate the nature of the controversy? (I can't, I forgot the details.) Scientists have controversies for a reason ... 67.198.37.16 (talk) 23:22, 14 March 2025 (UTC)

That is, I agree w/ what johnjbarton wrote. Extraordinary claims require extraordinary proof. Making a claim about negative temp that can be destroyed simply by adding one to the number of states when computing entropy means that half of the conventional textbook definitions of entropy are wrong when N is a small number. Have you gone through fixing all of the wikipedia articles that use the wrong definition? How about adding footnotes to all the college chemistry textbooks that have the conflicting definition? How do you think this is going to work out? Will we get another controversy the next time someone uses the wrong formula for entropy, and gets an off-by-one mistake? 67.198.37.16 (talk) 23:31, 14 March 2025 (UTC)

That is an interesting discussion but it has do to with the scientific community, not us. When the consensus on negative temperatures changes, we will reflect that. As long as negative temperatures are commonly covered in thermodynamics textbooks etc. they are not significantly controversial. cyclopia^speak! 17:30, 19 March 2025 (UTC)

Cyclopia "The concept of negative kelvin was controversial circa 2016.". This isn't to state: "the concept of negative temperature is (somehow) controversial." Onemillionthtree (talk) 21:06, 19 March 2025 (UTC)

"established since 1949" is obviously not in-itself proof for accepting negative temperatures - it is an argument for maintaining the status quo since 1949 though contrary evidence perhaps exists.

• "Academic manuals on thermodynamics" Onemillionthtree (talk) 22:02, 19 March 2025 (UTC)
  • supports:
    • p.1: Christopher Aubin · 2024 Raza Tahir-Kheli · 2021 - all other 2013 is the most recent. p.97-98
    • Page 2. Nicolas Sator, ‎Nicolas Pavloff, ‎Lenaic Couedel · 2023. p.77
    • Page 3. Jianzhong Wu, ‎John M. Prausnitz · 2024. "While the prediction appears absurd because the absolute tempertaure is commonly interpreted as a measure of the average kinetic energy, which is always non-negative - nevertheless, it has been demonstrated in the laboratory" p.43
    • Page 4. Patricia Faisca · 2022. https://www.google.co.uk/books/edition/A_Concise_Introduction_to_Thermodynamics/FJh8EAAAQBAJ?hl=en&gbpv=1&dq="negative+absolute+temperature"&pg=PT235&printsec=frontcover - no page number
  • neither:
    • page 2. Bertrand R Rowe, ‎Andre Canosa, ‎Dwayne E Heard · 2022. p.9 (foot of page) "Such claim of negative absolute "temperature" is also made"
  • doesn't support:
    • Page 2. Nicolas Sator, ‎Nicolas Pavloff, ‎Lenaic Couedel · 2023 p.76-7: "this study has led to controversy over the - definition of entropy in statistical physics" (note 27: study of 2013 published 2014)
    • p.4 Sergio Cecotti · 2024: "Negative absolute temperature is something which at first looks not to be consistent with the Laws of Thermodynamics . However , according to Ramsey [ 7 ]". - "the first point to stress is that "negative temperatures is rather misleading since these temperatures are hotter than all positive temperatures including T = + (symbol for infinite) p.67
    • p.8 Eugene Barsky · 2020: p.37: "it is impossible to imagine a negative temperature with respect to absolute zero" "absurd"

A single table with two header lines seemed awkward and confusing, so I separated the negative temperatures to a different table. Let me know if there is problem with this. I guess there is no controversy that the conventional temperatures are more central to the article topic Order of magnitude, and should be presented first. Negative temperatures on the other hand are somewhat tangential to the topic. Conventional temperatures are also easier to understand, so presenting them first also serves better our readers, who might not be familiar with negative temperatures. I did not understand what the header Conventional Kelvin volume:temperature of a gas determination of possible temperature range was trying to say, so I just restored the old nondescript header Item. 84.251.164.143 (talk) 08:53, 15 March 2025 (UTC)

Indeed. Negative temperatures are somewhat a distraction from the core topic of the article. —Edgar.bonet (talk) 10:53, 15 March 2025 (UTC)

This makes no sense. The core topic of the article are... orders of magnitude of temperature. Negative temperatures are part of the scale. That they happen in peculiar systems is hardly relevant -after all, also extremely high temperatures only happen in very exotic systems. cyclopia^speak! 17:31, 19 March 2025 (UTC)

Edgar.bonet, I see you are a physicist, so I'd be happy if you could explain your reasoning. :) cyclopia^speak! 17:33, 19 March 2025 (UTC)

(Not Edgar.bonet) For a non-scientist reader, the concept of negative temperature is likely unfamiliar. Encountering those temperatures first in the article might be confusing, especially since they are listed before absolute zero, which can give the impression that negative temperatures are colder than absolute zero. The reader might notice the popup note^[a], which clarifies that negative temperatures are actually hotter than any positive temperature—but they could also misinterpret the note as a reference.^[1]

A simple way to improve accessibility would be to avoid starting the table with negative temperatures. Since negative temperatures are an extension of the usual concept (albeit a natural one) and represent states that are in some sense hotter than the usual temperatures, they do not need to be listed first. Why not present them in a separate table? If that table is not in the beginning of the article, then there would also be space for a single paragraph before the table which could explain the concept.

Additionally, the table header—Conventional Kelvin volume:temperature of a gas determination of possible temperature range—is unclear, wouldn't you agree?

Another consideration is the phrase order of magnitude. It does not depend on the sign of the quantity, as seen in other articles like Orders of magnitude (charge), which do not discuss signs, but only decades. To illustrate this in the context of temperatures, consider the cited article (https://doi.org/10.1016/0921-4526(94)90475-8). The authors first determine the correct order of magnitude in positive temperatures (around 750 pK) using various cooling methods (dilution refrigerator, adiabatic demagnetization). Then, by flipping the magnetic field, they achieve a state of population inversion with an effective temperature of -750 pK. In this sense, the two temperatures are closely related and share the same order of magnitude. The minus sign only illustrates the concept of population inversion, and does not seem central to this article. 84.251.164.143 (talk) 20:15, 19 March 2025 (UTC)

Well, 84.251.164.143 has pretty much summed-up my opinion. The concept of negative temperature, although not controversial, is tricky, and exotic to say the least. I don't think this is what the average reader is looking for when reaching this page. Actually, I wouldn't bet the average reader is familiar with the concept of absolute temperature and absolute zero. Many people with no physics background would expect ultra-cold to mean something like “thousands of degrees below zero”. If they come here and learn that there is an absolute zero and ultra-cold temperatures are measured in “millionths of kelvins above absolute zero”, that's already a big win!

I would add that, in general, the “Orders of magnitude” Wikipedia pages are meant to give their readers a sense of scale: how small are small things, how big are big things, and where our units sit within that scale. As an example, assume you don't know what a candela per square meter is. You go to the page Orders of magnitude (luminance), and now you have a pretty good idea of how bright is 1 cd/m² or 1 kcd/m². Introducing the concept of negative temperatures at the top of this page is a distraction from this goal of giving a sense of scale. —Edgar.bonet (talk) 18:17, 20 March 2025 (UTC)

@Cyclopia: Could you explain your reasons on why you believe it is appropriate or necessary to place the negative temperatures first in the table? I am sorry if it is already written somewhere above, but I could not find it. 84.251.164.143 (talk) 05:20, 21 March 2025 (UTC)

Because I understand the convention is that we order values in increasing order. While formally negative temperatures are actually hotter than any positive temperature, they are assigned negative Kelvin values, and as such they come before. I understand the rationale to put them after positive temperatures, of course, and I'm not drastically opposed to it; but I am not sure if it makes sense to break convention. If consensus decides otherwise I'm not going to fight it :) cyclopia^speak! 09:47, 21 March 2025 (UTC)

The actual sources used give only negative temperatures - although the general science is the temperature is hotter - there isn't any information to use attached to the existing sources - those sources don't indicate hotter only colder - which is a contradiction using those sources to show hotter - that contradiction cannot be solved if they are used. I actually just have a problem with "hotter than all positive - hotter than infinite" - which I understand in the context doesn't indicate hotter than infinitely hot. If the temperatures are actually hotter than all positive temperatures - the scientists gave the negative temps. they wouldn't have indicated this if there isn't any reality. How both temperature positions exists needs more explanation; how this relates to the definition of temps: because entropy - the sub-zero gases will always provide energy to the colder: what are the actual conditions which would make always exchange from sub-zero - I think this must be a mathematical determination because always would necessitate a constant influx of energy - after time equilibrium would occur so no transfer of energy isn't always Onemillionthtree (talk) 15:01, 21 March 2025 (UTC)

Obvs. I do need to read more information on this topic: I would state "hotter than infinite" although the usage of infinite isn't non-permitted in the context - it shouldn't be possible to state this although the accepted semantic of "infinite" in the context allows - this is stated only from a linguistic perspective: ignoring the mathematical/conceptual values which support the acceptance of the statement. Onemillionthtree (talk) 15:07, 21 March 2025 (UTC)

@Cyclopia: However, for temperatures there is no such convention: no WP:RS arranges temperatures to run -∞K,-300K,-0K,0K,300K,∞K, but almost every reference points out that the correct order is 0K,300K,∞K,-∞K,-300K,-0K. Reference 1 even has a nice graphical representation of this. Taking the usual numerical order and applying it to temperatures is something like WP:OR or WP:Synth. 84.251.164.143 (talk) 18:24, 21 March 2025 (UTC)

I previous accepted this concept: "Negative Absolute Temperature" now I think it is a case of Suspension of disbelief because "-0K,0K" isn't necessary to show - obvs. as zero has no negative state - so "Negative Absolute" isn't possible to state - so I didn't make any effort to incorporate the reasoning of the paper. Onemillionthtree (talk) 18:55, 21 March 2025 (UTC)

"Under special conditions, however, negative temperatures- where high-energy states are more occupied than low-energy states - Absolute temperature T is one of the central concepts of statistical mechanics and is a measure of e.g. the amount of disordered motion in a classical ideal gas. Therefore, nothing can be colder than T = 0, where classical particles would be at rest." (Braun et al.). I would say that to retain "Absolute zero" linguistically would necessitate moving zero to the current most cold temperature not creating negatives of an absolute since the semantics of the word doesn't allow this. As much as I could understand from this brief excerpt: if T=0 & T=negatives temperatures: in both situations everything must/should be motionless - according to the kelvinian determination. In the example of an open universe - the laboratory special circumstances of T=negative is simply the same as the type of situation found in the open universe: a microcosmical reality. How absolute at the current position must be retained under the aegis of it being something necessarily classical I currently don't know. Onemillionthtree (talk) 19:23, 21 March 2025 (UTC)

A better example than "open universe" since this is hypothetical: the special circumstances of negative kelvn is simply a discovery of an actual temperature somewhere in the universe - an example of physics which we don't have common-Earthly knowledge of - is not special at all from the position of a different galaxy or solar system (outside of the observable universe perhaps) where the scientific evidence could easily show how apparent special physics in a laboratory are obviously possible - somewhere much further away from our ambient universal (background) temperatures - background radiation/temperature (this is to state the usual dynamic in a different environment is naturally at a lower absolute than science on Earth) is sufficiently lower that Absolute is the same as our negative states of kelvin. Onemillionthtree (talk) 19:33, 21 March 2025 (UTC)

I don't get the argument about a different galaxy. No material object, in any galaxy, can be at a negative absolute temperature. This concept of negative temperature can only make sense for specific sets of degrees of freedom (typically magnetic) where the energy levels are bounded in energy: there must be a “top energy level”, just like we always have a lowest energy level (the so called “ground state”). This cannot work with the translational degrees of freedom (thermal motion, lattice vibrations...) because the corresponding energy levels have no upper bound: as the temperature goes to infinity, so does the energy, and we cannot reach beyond infinity.

When a research group claims to have achieved a negative temperature, they are typically talking about a collection of spins in their sample, not about the sample as a whole. The lattice vibrations of the sample are typically very cold, and only very weakly coupled to the spins. If that coupling is weak enough, you can have a thermal equilibrium of the crystal lattice at a positive temperature and, at the same time, a thermal equilibrium of the spin bath at a negative temperature. The sample as a whole is not in thermal equilibrium and thus has no temperature. —Edgar.bonet (talk) 11:31, 22 March 2025 (UTC)

@Edgar.bonet: Thanks! Still, I am unsure why this is a 'distraction'. cyclopia^speak! 09:10, 24 March 2025 (UTC)

@84.251.164.143: If sources do so, then let's follow sources, absolutely :) Can you make a couple examples, so that these sources can be linked to explain readers a non-intuitive ordering? cyclopia^speak! 09:08, 24 March 2025 (UTC)

Consistent thermostatistics forbids negative absolute temperatures Jörn Dunkel & Stefan Hilbert 2014 "we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically." Onemillionthtree (talk) 20:52, 21 March 2025 (UTC)

It’s a negative on negative absolute temperatures New research shows negative absolute temperatures — and perpetual motion machines — are still out of reach. Jennifer Chu, MIT News Office December 20, 2013: "mathematicians at MIT and the Max Planck Institute for Astrophysics have challenged these ideas - the researchers analyzed past claims of negative absolute temperature and found that in all cases, scientists were interpreting experiments based on a flawed — though universally accepted — definition of entropy, or heat. This definition, called the Boltzmann entropy, appears in modern physics textbooks, and is widely used to calculate the absolute temperature of a wide range of physical systems." Onemillionthtree (talk) 21:18, 21 March 2025 (UTC)

There's a waterfall of confusions and misstatements in the conversation above. Sure, I suppose you can find textbooks that define negative temperatures. That's not the issue. The issue is whether these nuclear spin systems actually have a negative temperature. As long as there's no consensus on that specific result, please don't pretend it's some dry and dusted topic covered in textbooks. Removing statements that attempt to say that the results are controversial is a dis-service. As to setting it off into it's own zone, yes, absolutely! These are not temperatures that are just like any other, but below absolute zero. There's a reason its called "absolute zero", you can't just throw that out the window like it never happened. 67.198.37.16 (talk) 02:33, 20 March 2025 (UTC)

Ah, jeez. I just re-read the above. If we're using negative temperatures to denote population inversions, that's even more of a dis-service to the novice reader. Yes, population inversions are real. Yes, you can describe them "as if" they had a negative temperature. But lumping that concept into conventional thermo is just a recipe to confuse the novice reader: the high-school student, the non-physics-major college student-- these people will not know about population inversions. It does nothing other than to take a concrete idea -- "absolute zero", and turn it into something blurry, vague and meaningless. Don't mix up advanced and basic topics in this way. 67.198.37.16 (talk) 03:05, 20 March 2025 (UTC)

"Still"

I've removed the nonsensical claim that "free bodies are still" at absolute zero. While you can't actually get to absolute zero, if you could, there's no reason things couldn't be moving. --Trovatore (talk) 17:36, 24 February 2025 (UTC)

Yes, there is a reason! A physical system at zero temperature has a 100% probability of being in it's lowest energy state. This means that:

• A classical system must be at rest, otherwise it would have kinetic energy that it would not have if it was at rest.
• A quantum system can have kinetic energy in its ground state. However, the ground state being an eigenstate of the Hamiltonian, it is a stationary state and, as such, it does not evolve in time. In that sense, the system could be said to be “still”.

— Edgar.bonet (talk) 19:17, 25 February 2025 (UTC)

I think you're missing the point. Kinetic energy per se doesn't count; only internal energy. You can have, say, a metallic sphere spinning very very fast, with very high rotational kinetic energy, and it can still be cooled arbitrarily close to absolute zero, because its bulk kinetic energy is not part of the discussion at all. --Trovatore (talk) 23:10, 25 February 2025 (UTC)

Actually now you've got me wondering. Our internal energy article claims that It excludes the kinetic energy of motion of the system as a whole and the potential energy of position of the system as a whole, with respect to its surroundings and external force fields. It includes the thermal energy, i.e., the constituent particles' kinetic energies of motion relative to the motion of the system as a whole. The last bit about the kinetic energies of the particles relative to the system would seem to include their orbital kinetic energy, which summed up gives you the bulk rotational kinetic energy.

But bulk rotational kinetic energy doesn't seem thermodynamic. I have trouble believing that that's intended to be included. (I'd say the same thing about coherent vibration.)

I'm going to ask a question at WP:RD/Science#Internal energy and bulk rotational kinetic energy. Please feel free to contribute; I see you're a physicist. --Trovatore (talk) 00:03, 26 February 2025 (UTC)

OK, here's the deal. When you're talking about bodies with an Avogadro's number of atoms in them, then rotational energy doesn't count, because you'd have to take that energy and divide it by 6 x 10^23 and its silly and pointless. Thermodynamics is about counting degrees of freedom-- commonly vibrational, and bulk motion is just one (or two or three) degrees of freedom, and not 6 x 10^23.

However, it all gets trickier when you set the size of your system to 100 atoms, or smaller, at which point you have to start asking things like "what does it even mean to have thermodynamics of such small systems?" For example: "what if I have only two things, and they are orbiting each other?" then walk back up: "what if I have two oxygen atoms, bound to a molecule, and that molecule has non-zero orbital angular momentum?" and then "what if I gave a gas of oxygen molecules at finite temperature?" For this last question, the spinning of each individual molecule DOES contribute to the thermodynamics. But if you are thinking of a centimeter-sized ball of metal that is spinning round, that spin is not thermodynamic, at all.

Perhaps what I wrote above is silly-obvious, but it points in the direction of saying thermo for small N is non-obvious. Oh, and then there is the Fermi–Pasta–Ulam–Tsingou problem -- have fun with that. 67.198.37.16 (talk) 02:55, 20 March 2025 (UTC)

Absolute zero

Instead of Unachievable^[a] absolute zero.^[3][4] as the first entry, I would suggest simply using Absolute zero with no extra adjectives or notes. Emphasising the 'unachievability' in both the adjective and the note certainly seems too much. It would be better to rely on the dedicated article accessible through the link. The statement does not really need citations either, since it is common knowledge. 84.251.164.143 (talk) 16:01, 15 March 2025 (UTC)

Oppose. I don't see why emphasizing a fundamental feature of such a temperature is 'too much', nor it is "common knowledge". Not all our readers are scientists. cyclopia^speak! 17:29, 19 March 2025 (UTC)

Well as a comment on your comment - it seems reasonable in tone - but the content of your communication is after simply removing the information - what could be the reason you need to supress? I could think that "Absolute zero" then providing a contradictory less than Absolute could be a reason for not including: less than an absolute temps. I am somewhat naive with regards to the physics and would really hope for a more complete and comprehensible explanation of how negative temperatures are achievable. If Kelvinian physics is wrong then there is scope for more information - removing the information though I can't find much reason - your reason isn't a reason for removal. The other article could be made while maintaining/retaining the same element in this article."Emphasising the 'unachievability' in both the adjective and the note certainly seems too much.": I personally don't concur with your observation. Unachievable: "Theoretical lower temperature limit not realizable in practice because of the third law of thermodynamics" - is not poor use of English is only explaining - not much wrong with the language use I think. Actually "unachievable" I would state is wrong - the idea that science only fails to achieve it: such that "achievements" is a usage - successful/failed student - could imply (implicitly) is a type of non-achievement: I changed it unto: "Not scientifically realizable in Kelvinian physics". Onemillionthtree (talk) 20:45, 19 March 2025 (UTC)

Obviously I've taken a liberty here which maybe isn't acceptable per the protocol of consensus - maybe it is though an acceptable response for 84.251.164.143 Onemillionthtree (talk) 20:56, 19 March 2025 (UTC)

Oppose. Everything we know from physics is that it is unachievable. No one has ever claimed that they've "achieved" it, and there are lots of strong arguments that it can't be reached. No one has ever claimed it is possible. 67.198.37.16 (talk) 02:41, 20 March 2025 (UTC)

T_C BEC

Google advanced search didn't return the exact: "Critical temperature of alkali BEC". "atomic BEC" was found ai.

prev. v. links: "Critical temperature" into Bose–Einstein_condensate#Critical_temperature but no Tc

I couldn't find: the highest known temp. BEC which would define the range Tc

I didn't add "Critical temperature (T_c) range of atomic BEC (iask.ai/?mode=question&q=what+is+the+highest+temp+BEC+known)" as presumed 170approx. as Tc range approximate. removed was: "Critical temperature of alkali BEC" Onemillionthtree (talk) 02:36, 22 March 2025 (UTC)

"matter-wave lensing"

I reviewed "-38pK" as this part (i.e. title of this section) was excluded by the edits I made introducing uniBremen interview content (currently ref.8: up2date.uni-bremen.de) - though the excluded is shown in the original source: doi:10.1103/PhysRevLett.127.100401 currently ref. 7. I don't know what m-wl is: after https://iiask.ai/?mode=question&options[detail_level]=detailed&q=wht+is+matter-wave+lensing I determined m-wl is a methodical aspect "to focus or wikt:collimate" (askai) - which isn't imperative in the information provided similarly to the the anti-gravity drop: to increase the time of existing of the specific quantum state (c.f S.Herrman vid. up2date.uni-bremen.de) - so didn't return "lensing" as an information. (𒌋*𓆏)𓆭 18:39, 4 April 2025 (UTC)