Talk:Temperature/Archive 5

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An object perceived as cold has a lower temperature than one perceived as hot.

The present lead contains the following: "An object perceived as cold has a lower temperature than one perceived as hot." It is not necessarily so. Every textbook explains why.Chjoaygame (talk) 00:09, 25 January 2013 (UTC)

It would speed up the discussion if you would provide a counter-example. Spiel496 (talk) 01:00, 25 January 2013 (UTC)

I think what he is referring to is that if you touch a piece of wood at, say, 0 C, it will not feel as cold as a piece of steel at 0 K. The sensation of hot/cold relates directly to the rate of energy gain/loss from your finger, not simply to the temperature difference between your finger and the object touched. PAR (talk) 16:22, 25 January 2013 (UTC)

The statement would be true if the material is the same for both hot and cold objects (and the touching hand is the same too :-) Staszek Lem (talk) 21:33, 28 January 2013 (UTC)

In any case, there is a classical example that a neon lightbulb is cold on touch but the plasma inside may have a very high temperature. I didn't peruse the article: does it contain this factoid, quite useful to demonstrate the dictinction between intuitive and formal? Staszek Lem (talk) 21:32, 28 January 2013 (UTC)

edits by Staszek Lem

(with the exception of some quantum physics effects)

Perhaps Staszek Lem will explain what this means or why it fits here?Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

Yeah, that sounds like a goof to me. People get hung up on apparent the conflict between "abs zero = zero motion" and "quantum mechanics = nothing ever stops". To have a bunch of oscillators at absolute zero simply means they're all in their ground state. It's irrelevant that the ground state has nonzero K.E., am I right? Spiel496 (talk) 04:37, 29 January 2013 (UTC)

This is written as a summary of what is written in this article, if you managed to read it to the very bottom. Staszek Lem (talk) 01:26, 30 January 2013 (UTC)

At the same time I have to agree that the word "quantum" is ..er.. rather skewed in modern pop-culture, so I reworded the item. Staszek Lem (talk) 02:12, 30 January 2013 (UTC)

Oh, I totally didn't get that you were referring to negative temperatures (being possible in a quantized system). I see what point you were trying to make. If only there were a scratch-pad area where editors could propose wordings and discuss them before publishing on the page. Spiel496 (talk) 02:46, 30 January 2013 (UTC)

This is not how wikipedia works. Unless the text is grossly erroneous, there is no reason to discuss it before editing. You are free to improve my wording, bearing in mind that since the article has a section "negative temperature", it is reasonable to mention it in the intro, especially since there is apparent contradiction: "lowest possible temperature" and then suddenly there is even a lower one. Staszek Lem (talk) 04:38, 30 January 2013 (UTC)

"determines"

Staszek Lem's comment is taking a philosophical approach here, putting a particular meaning on 'determines'. The comment is reading 'determines' as meaning 'acts with causal efficacy upon' or somesuch. Another reasonable meaning is mere logical determination, 'provides information that finds or identifies the value of' or somesuch. True, there are problems with saying that temperature causes things, but that meaning is not specifically indicated here. I am not particularly defending what he removed here, but I would say that it might have been better to improve rather than merely delete it.Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

I agree. If necessary, reword it as "This and that important thing are temperature dependent" but it seems a loss not to motivate the concept of temperature a bit. Spiel496 (talk) 04:40, 29 January 2013 (UTC)

A Igree that "Depends on temperature" is a better wording that "determines". Temperature is a human way to measure something. And there is way more meanings to the word "determine" than the two mentioned. Therefore it is a sloppy word to be used in an intricate topic. (Especially bearing in mind taht everybody "knowns" what temperature is without actually knowing it). Staszek Lem (talk) 01:41, 30 January 2013 (UTC)

I am not against restoring whatever is to be restored/reworded, but with one big "but": references, please. In particular, the given examples are highly dubiously phrased. I may explain in detail why they suck (and trigger a lengthy discussion), but,... references please, and I am good. Staszek Lem (talk) 01:41, 30 January 2013 (UTC)

"the intro sucks bigtime"

Staszek Lem's comment apparently indicates that he thinks that the sentence "Temperature is a physical quantity that measures degrees of hot and cold on a numerical scale" "sucks bigtime". Staszek Lem's edit has replaced it with "Temperature is a physical concept that quantifies (provides numerical scale) for the informal concepts of ″hot″ and ″cold″." I have put headers A, B, and C on particular aspects of this view of Staszek Lem's comment, as may be seen immediately below, for particular further commentary.Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

A. "informal concepts"

Staszek Lem's edit is taking a philosophical line here. The usual idea of a Wikipedia lead is that it is in ordinary language, unless otherwise indicated, for some good reason. In this case his edit says that he is not happy with the ordinary language words hot and cold. He is treating them as if they come from some kind of mistaken or otherwise defective viewpoint. I think they are words of the ordinary language, and that ordinary language speakers know what they mean and how they can be mistaken or otherwise misperceived. In other words, it seems from his edit that Staszek Lem is presuming that physics can teach ordinary people what they should mean when they say 'hot' and 'cold'. It seems from his edit that when Staszek Lem indicates hot and cold as "informal" concepts, he thinks Wikipedia takes a superior position, that it teaches ordinary people the proper formal language that supersedes their ignorant one. I don't think so.Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

Yes they are informal concepts. And informal is not the same as "defective". And please cease a very bad habit to read someone's thoughts and intentions. Your diatribe is completely off the point. Staszek Lem (talk) 01:48, 30 January 2013 (UTC)

B. "physical concept that quantifies"

Staszek Lem's edit is apparently saying that a "physical concept that quantifies (provides numerical scale)" has a substantially different meaning from a 'physical quantity that measures on numerical scale', and that it improves the expression of the intended idea, to the extent that one can say that 'physical quantity that measures on a numerical scale' sucks bigtime. It seems from his edit that Staszek Lem is working from a very abstract and special philosophical position that thinks this kind of distinction is useful for the lead of a Wikipedia article. Perhaps he will explain why?Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

You apparently do not see the diffence between the result of measurement (quantity) and the concept which is being measured. I find it amusing that you use the words "abstract" and "philosiphical" as insults in the article which is very abstract and philosophical. Also, please don't misquote me. Although this time your misquote is a perfect fit: if you don't see what's wrong with the expression "measures on numerical scale'", I may only refer you to the wikipedia articles "measurement" and "tautology" (although I know taht wikipedia is not a valid reference :-) Staszek Lem (talk) 01:54, 30 January 2013 (UTC)

Editor Staszek Lem writes above that he finds my comments amusing. To me, this looks like a direct pejorative personal comment.

I directed my remarks to his edits and comments, not to him as a person. He is mistaken to suppose that I regard it as insulting to say that his edits and comments take an abstract and philosophical approach. But, yes, I am questioning the appropriateness here of that approach.Chjoaygame (talk) 05:33, 30 January 2013 (UTC)

C. "Further development of physics have brought a formal definition for the concept, which may sometimes disagree with the intuitive notions of ″hot/cold″."

From this edit it seems that Staszek Lem is telling us that it is important for the lead to point out possible differences between how the ordinary person finds things and how they are seem from the viewpoint of the further developed formal definitions of physics. I don't think this rather refined point is needed here; indeed I think it is an unhelpful distraction.Chjoaygame (talk) 22:18, 28 January 2013 (UTC)

I don't care for his wording much, but shouldn't we have something about the connection between temperature and the perception of hot/cold? All else being equal, a higher-temperature object will be perceived as warmer than a lower-temperature one, right? Then an explanation for the cases when perception does not match physics. Spiel496 (talk) 05:24, 29 January 2013 (UTC)

It may well be valuable to say something about the vagaries of perception of temperature. But the article doesn't contain it at present and so it has no place in the lead at present, because the lead should be a summary of the article. The lead should not say things that are not said in the body of the article.

Perhaps someone would like to put in something about this, into the body of this article. For myself, however, I would not favour a big deal being made of this in the lead, when it comes to summarizing such new material. Temperature is about objective measurement, not about psychophysics. The subject of psychophysics is a very important biological science. It presupposes the availability of physical knowledge about the physical objects of perception. This article, here, on temperature, will provide such presupposed physical knowledge of temperature for the psychophysicists.

But it is not the function of this article on the physics to pre-empt the work of the psychophysicists. Psychophysics provides a load of accounts of misperceptions of various kinds, not only of temperature. That is where they are best dealt with in detail, I think.Chjoaygame (talk) 15:33, 29 January 2013 (UTC)Chjoaygame (talk) 16:14, 29 January 2013 (UTC)

I have removed...

From the opening statement:-

Further developments of physics have brought a formal definition for the concept, which may sometimes disagree with the intuitive notions of "hot/cold".

What is sometimes doing here? It is not a statement of fact, just a vague notion, it has no place in an opening statement. --Damorbel (talk) 13:13, 29 January 2013 (UTC)

I agree that this sentence should be deleted.Chjoaygame (talk) 15:35, 29 January 2013 (UTC)

it is a statement of fact, as I mentioned in a section above #An object perceived as cold has a lower temperature than one perceived as hot.. If the firts sentense says thet temperature measures cold, then certainly the article must have a small section which explains the difference between informal (yes, Chjoaygame, informal) concept of "cold/hot" and what is actually measured and what surprizing differences may be. Also, the article badly misses a section on the history of the concept. Staszek Lem (talk) 02:06, 30 January 2013 (UTC)

Definition of temperature

I searched thru talk archives whether the definition of temperature was discussed, and I was amazed how much original research was done and how much time wasted. Why don't you guys (and me too; my bad; I made the same mistake, even seeing that the article is a mess) start from solid reference books and give not one but two or more definitions, with references, of course. Here are samples, readily available from dictionary.com:

Science Dictionary

temperature (těm'pər-ə-ch r') Pronunciation Key A measure of the ability of a substance, or more generally of any physical system, to transfer heat energy to another physical system. The temperature of a substance is closely related to the average kinetic energy of its molecules.

World English Dictionary

temperature (ˈtɛmprɪtʃə) 1. the degree of hotness of a body, substance, or medium; a physical property related to the average kinetic energy of the atoms or molecules of a substance

2. a measure of this degree of hotness, indicated on a scale that has one or more fixed reference points

Dictionary.com Unabridged 1. a measure of the warmth or coldness of an object or substance with reference to some standard value. The temperature of two systems is the same when the systems are in thermal equilibrium.

Why not start from here and/or solid textbooks? Staszek Lem (talk) 04:57, 30 January 2013 (UTC)

Editor Staszek Lem has put, as the second sentence of the lead, his own point of view, apparently formed from a dictionary of ordinary language, of what temperature measures. It is invalid, even as the expression of a point of view within physics.Chjoaygame (talk) 06:01, 30 January 2013 (UTC)

I have now put up a definition that follows the usage of Maxwell, who says that temperature is a physical quantity. The definition that I have put up is minimalist. The reason for this is that there is on this page wide divergence of viewpoint on more detailed questions about temperature, but I am hoping that there will not be too much divergence about the definition that I have put up: "Temperature is a physical quantity that indicates hot and cold." More detail will surely bring up divergence of opinion, that has appeared on this page, and that can be found in the body of the article, but is not called for in the first sentence of the lead.Chjoaygame (talk) 14:14, 30 January 2013 (UTC)

These are not definitions of temperature, they are descriptions of temperature. Let's not confuse the two. A definition of (thermodynamic) temperature will basically be a description of how to measure the temperature of a body in equilibrium, without the use of a thermometer. This is to be found in the second law of thermodynamics. PAR (talk) 21:42, 30 January 2013 (UTC)

Yes, I agree with this comment. As I read it, it means that the general theoretical definition of thermodynamic temperature is something more or less along the lines of:

In thermodynamics, in a system of which the entropy is considered as an independent externally controlled variable, and the internal energy is considered as a function of the other independent externally controlled extensive thermodynamic variables especially including the entropy, the thermodynamic temperature is defined as the partial derivative of the internal energy with respect to the entropy.<Callen, H.B. (1960/1985), Thermodynamics and and Introduction to Thermostatistics, (first edition 1960), second edition 1985, John Wiley & Sons, New York, ISBN 978-0471862567, p. 35.>

Something along those lines? It relies on the differentiability and convexity of the internal energy as a function of the entropy, and on something like the third law, to produce an absolute zero of temperature?

Respected authors Chapman & Cowling offer also what they call the kinetic theory definition of temperature, and spend some effort to check its agreement with the more general theoretical definition where their domains overlap.Chjoaygame (talk) 23:08, 30 January 2013 (UTC)

No, only the mechanical quantities (e.g. mass, pressure, volume, work) are directly measurable. Every other measurement requires a thermodynamic law for its validity. The way the second law usually defines temperature is using a Carnot heat engine. Without going into the reasoning, with a Carnot engine you only measure four values of the work done on or by the working body. If you start with the working body in thermal contact with the cold reservoir and call the work extracted during this step $\delta W_{1}$, then you have three more measurements: $\delta W_{2},\,\delta W_{3},\,\delta W_{4}$. According to the second law, the ratio of the temperatures of the hot reservoir $T_{h}$ and the cold reservoir $T_{c}$ are given by $T_{h}/T_{c}=\delta W_{1}/\delta W_{3}$. Lets say one of the reservoirs is a water triple point cell. Then you define its temperature to be 273.15 K, and you then have the temperature of the other reservoir in Kelvin. Or pick another number and make up your own temperature scale. Now you are ready to begin calibrating a thermometer to use in subsequent temperature measurements. That is the definition of temperature. There are other contenders, but unless they clearly state the basic axioms and preceding logical steps culminating in a clear measurement recipe, they are not definitions. If they do not agree with the definition above, (over the range of its applicability), then it may be a definition, but its not a definition of temperature. PAR (talk) 02:59, 31 January 2013 (UTC)

" ...only the mechanical quantities (e.g. mass, pressure, volume, work) are directly.... "

How?

I suggest you need Newtons laws (plus 20^thC relativity adjustments).

And again :-

...Lets say one of the reservoirs is a water triple point cell. Then you define its temperature to be 273.15 K, and you then have the temperature of...

No, you do not have the definition of temperature! You have the definition of a suitable temperature scale. But a scale is not 'the temperature', the temperature is the translational kinetic energy (more accurately the linear momentum) of the system particles. The triple point (of H₂O), other triple pointss could be used) just happens to be a nice, but rather inaccurate, stable condition that is fairly easy to establish. --Damorbel (talk) 06:43, 31 January 2013 (UTC)

Found?

I have removed the text :-

It has been found theoretically that...

Theoretically Found? Um, er... not possible! Theories are made. --Damorbel (talk) 21:25, 7 February 2013 (UTC)

A recent edit by Spiel496

This edit by User:Spiel496 is misleading. If temperature is not intensity, I ask Spiel496 to explain just what it is. To call it "a measure or hot and cold" is too imprecise for Wikipedia since "hot and cold" is a relative measures; the concept of temperature, as with the thermometer, serves to remove the relativity from the measurement of heat.

So Spiel496, lets be hearing from you. --Damorbel (talk) 18:46, 11 February 2013 (UTC)

I'm no fan of the "a measure of hot or cold" wording either. I just needed replace the phrase "intensity of heat" with something readers can understand. It would've been easier to just revert your last two edits, but I was trying not to be a jerk. Spiel496 (talk) 20:14, 11 February 2013 (UTC)

I just needed replace the phrase "intensity of heat" with something readers can understand.

Well, lets give them a chance, shall we? Temperature is the factor that governs the speed of chemical reactions, rates of phase change; the word intensity is used for similar effects in electricity; for mechanical force also; and much much else.

I do think you should give a reason why it should not be understood, it is not at all unususal. --Damorbel (talk) 21:17, 11 February 2013 (UTC)

Unless the readers know the definition of "intensity" and of "heat" they don't really have a chance. Mostly the trouble is I've never heard the phrase "intensity of heat". So I fall back on "intensity" which usually means a flux per unit area, and "heat"... It sounds like temperature should then have units of watts/area, which of course wasn't your intent. Spiel496 (talk) 20:57, 12 February 2013 (UTC)

I agree. But temperature is not only independent of the amount of energy it is also independent of the amount of matter; this is reflected in my latest edit where I have put energy density; this is not unreasonable given the Boltzmann relation. The relation is quite general, the relations PV = RT = k_BNT are equally valid. --Damorbel (talk) 21:16, 12 February 2013 (UTC)

Edit reverted, with summary: " (neither our article, not Maxwell's ref, nor Boltzmann constant page talk bout "energy density". Refs, please". Staszek Lem (talk)

Staszek, you are citing articles in Wikipedia as a reliable source, this is not Wiki policy because it can lead to chaos, so before you edit follow good advice and undo your revision until you find a better argument. --Damorbel (talk) 07:22, 13 February 2013 (UTC)

I am not putting anything into the article. It is you who is not citing nothing. Staszek Lem (talk) 15:46, 14 February 2013 (UTC)

Oh and by the way, the first line of the Wiki Boltzmann constant article is:-

The Boltzmann constant (k or kB) is a physical constant relating energy at the individual particle level with temperature. It is the gas constant R divided by the Avogadro constant NA

Can you explain why this is not relevant, please? --Damorbel (talk) 07:31, 13 February 2013 (UTC)

And of course you may want to read the Wiki article on energy density where the first line is :-

Energy density is the amount of energy stored in a given system or region of space per unit volume. --Damorbel (talk) 07:45, 13 February 2013 (UTC)

I think the Boltzmann constant would be relevant only when giving a statistical mechanics definition of temperature, complete with an equation and the "1/2 kT per degree of freedom" language. But if temperature was defined within classical thermodynamics long before any notion of kB (was it? not completely sure here) then kB is not relevant here.

I don't think the 'energy density' concept helps. The novice will be misled as much as educated. To be nit-picky, it shouldn't be energy, but rather something like 'kinetic energy associated with random microscopic motions of the atoms'. And 'density' usually means 'per unit volume' which is wrong. You mean something more like per-degree-of-freedom.

I'd be in favor of weighting the intro heavily toward the stat mech definition. Random vibrations are easier to visualize than the partial derivative with respect to entropy. The important points are:

• Temperature quantifies the common notion of hot vs cold
• It affects rates of chemical reactions, and so is extremely important biologically
• Make some connection with random microscopic motion, maybe even some 1/2*kB*T
• Possible quick def of "heat" and mention of the classical thermo definition

Spiel496 (talk) 22:01, 13 February 2013 (UTC)

Favor heavy weighting?Chjoaygame (talk) 01:33, 14 February 2013 (UTC)

Are you making fun of me?  :-) Spiel496 (talk) 07:29, 14 February 2013 (UTC)

No; giving you an opportunity to mend your error for yourself; an opportunity you didn't take. Wikipedia editors should take a neutral point of view, not favor heavy weighting.Chjoaygame (talk) 08:02, 14 February 2013 (UTC)

"Neutral point of view"? Lighten up, a little. Statistical mechanics and thermodynamics aren't opposing political viewpoints. I'm just saying if the stat mech definition of T is easier to understand, the Lead could use it. Spiel496 (talk) 19:41, 14 February 2013 (UTC)

You are trying to minimize the need for a neutral point of view. Not a good sign. It is evident that you don't understand the difference between the kinetic theory viewpoint and the statistical mechanical viewpoint. You are wanting to put "heavy weight" on what is obviously the kinetic theory viewpoint, but are calling it the statistical mechanical one. Indeed kinetic theory, statistical mechanics, and thermodynamics are not political ideologies. They do not compete. But they are distinct physical theories.Chjoaygame (talk) 20:51, 14 February 2013 (UTC)

Okay, kinetic theory, then. Sorry, that was sloppy of me. Same issue, though; we don't put the entire article into the intro, so something gets left out. So what if we define T in terms of kinetic theory, maybe with an ideal and/or monotonic gas as an example, followed by mention of one or more formal definitions?

The NPOV accusation strikes me as hyperbole or as an attempt to stir up an argument. I'm not listening to further accusations by Chjoaygame. If another editor would like to set me straight, please contact me, and I'll hear you out.

Finally, I'll just remark that the intro was stable and concise for about a year. Here's a snapshot from last April. The Lead in this version reads like an incomplete but reasonably accurate description of what temperature is and why it's important. In other words, a good intro. For a more complete picture, see the article. I think the Lead suffers if we introduce a lot of technical terms that themselves need defining. Spiel496 (talk) 02:36, 15 February 2013 (UTC)

Kinetic theory possesses a definition of temperature for its own use. It is not a general definition of temperature.Chjoaygame (talk) 05:25, 15 February 2013 (UTC)

Chjoaygame, what are we supposed to understand from temperature for its own use? Temperature scales may well be for own use but surely the "energy per particle" remains the same for all temperature definitions for all temperatures. --Damorbel (talk) 08:08, 15 February 2013 (UTC)

The temperature definition used by kinetic theory does not make sense outside the context of kinetic theory. Quantum phenomena provide many cases in which the kinetic theory definition does not make sense.Chjoaygame (talk) 09:12, 15 February 2013 (UTC)

You surprise me, for example? --Damorbel (talk) 12:18, 15 February 2013 (UTC)

It is hardly a surprise to learn that this surprises you. Are you asking me to use this talk page to give a lesson on quantum theory? I suggest that standard texts, for example on solid state physics, would do a better job at that than I would.Chjoaygame (talk) 20:08, 15 February 2013 (UTC)

Are you asking me .... to give a lesson on quantum theory?

You raised the matter; you should be able to give some kind of support, a few links perhaps? --Damorbel (talk) 21:07, 15 February 2013 (UTC)

The matter has been considered here many times before. I do not see that I am likely to do better.Chjoaygame (talk) 23:27, 15 February 2013 (UTC)

The matter has been considered here many times before

So you say, but without a summary or a ref. you are scarcely being explicit, so how can anyone grasp exactly what point you are making. You have made a vague assertion, please make it clear which (or where) Quantum phenomena provid[ing] many cases in which the kinetic theory definition does not make sense. --Damorbel (talk) 18:32, 16 February 2013 (UTC)

I regret that I do not think I can offer a useful response to this comment.Chjoaygame (talk) 19:57, 16 February 2013 (UTC)

• Temperature quantifies the common notion of hot vs cold

Not really, hot vs cold is a relative measure; Fahrenheit's thermometer, although using two fixed points, was always an absolute measure, whether the absolute zero of temp. was acknowledged or not.

For the rest of your comments, although useful and relevant, do not amount to an opening statement.

Lets try this:-

...[it} is a measure of the thermal energy of the particles of matter...

Thermal energy eliminates the frequently used awkward expression "translational kinetic energy" and "...of the particles" replaces the less precise "density".

The section on the Boltzmann constant:

The fundamental relation of energy density and temperature is the Boltzmann constant which relates temperature to particle energy.

The Boltzmann constant has different values according to the temperature scale used, ^oF, ^oC, K etc.

is absolutely essential because it is about the only measured constant in the whole business! It should be restored, perhaps with modifications e.g. "thermal energy per particle" in place of "energy density".

Temperature is not a measure of energy; energy is measured in Joules and it is proportional to the amount of material, temperature is independent of the amount of material, as is density. --Damorbel (talk) 08:51, 14 February 2013 (UTC)

<Sigh>. YOur opinion is respected, but... no refences, no density. Would you like me to quote some wikialphabet soup? Staszek Lem (talk) 15:46, 14 February 2013 (UTC)

My understanding from your response is that the suggestion:-

"thermal energy per particle" in place of "energy density".

is equally unacceptable to you? --Damorbel (talk) 17:20, 14 February 2013 (UTC)

"Per particle" is OK with me. However please take a look at my nitpicking of phrasing in Talk:Boltzmann constant and the resulting change in the article. Staszek Lem (talk) 20:11, 15 February 2013 (UTC)

Regarding "hot" and "cold", surely it is appropriate to make some mention of the correlation between perceived temperature and scientific temperature. While we may lack accuracy, we humans can sense absolute temperature, and it corresponds pretty well with the T in PV=nRT. This is in contrast to terms like "energy" and "potential" whose common definitions are quite different from what physicists mean. Spiel496 (talk) 02:54, 15 February 2013 (UTC)

...make some mention... Of course!

But this should be illustrated by the well kwown test - first dipping your left hand in hot water and your right in colder water and then both hands in water at a temp. between the two. The fact that your hands now detect different degrees of hotness is a good reason for using a thermometer, thermometers measure temperature!

However this is not material for the opening statement on Temperature, much more for thermometers --Damorbel (talk) 08:03, 15 February 2013 (UTC)

History of the concept

Please let me restress the importance of the (missing) "History" section. Let us take an analogy. There are words "work", "energy", "power" used in common parlance. However when comes to physics, they assume specific meanings, which may be confusing for a layman. Por example, historically the word "mass" was something akin to the "amount of stuff matter. But physicists eventualy concluded that it is most convenient to define it in terms of acceleration or interms of gravitational force, and have to discuss equivalence of the two definitions and whats not in further "rocket science" developments of theory of relativity and quantum physics.

The same happened with temperature. Originally people wanted to measure "the degree of hotness" whatever it was and it turned out that people were lucky enough that pereption of "temperature" may be adequately described by a single number, unlike, say, perception of color. Further digging into the reasons wise men tried to figure out where temperature comes from, and again, like it was with "mass" there was an issue of equivalence of theoretical derivations (and matching to experimental observations) in further "rocket science" deeper physics perspectives.

Only after this section, preparatore for a layman, the article may jump into quantum thermodynamics and whats not without an average person getting lost ("OK, OK, so when I touch a stove, do I really feel how molecules jig madly or what?" or "Does a single atom in vacuum have temperature?" "What is the temperature of quarks?"). Staszek Lem (talk) 20:11, 15 February 2013 (UTC)

Staszek Lem,I suspect you are getting there. You refer to a physicist's concept of mass and energy etc. might be confusing to the layman. Do you not think this is an endemic and insoluble problem? The physicist's view is not that of someone "trying to confuse the layman". The point of science is to learn by refining the interpretation of observation, so all may profit from the increase in knowledge; science should not be a secret code, although if you read some science literature that is indeed what it is.

The point of an encyclopedia is to lead the reader into areas not previously encountered, so it should not shirk from making a an explanation as clear and profund as can be supported by the literature. Many may get lost in an article, but that is not to say that they will not, with time, find their way to a full understanding.

So please do not decry the deeper aspects of physics to be found in a good encyclopedia article, it would not be doing its job if it did not go as far as possible. --Damorbel (talk) 20:57, 15 February 2013 (UTC)

How the heck you have come with the notion that I am trying to decry something other than clumsy presentation in our article? Yes "Many may get lost in an article", but it is bad if this happens from the very first lines of the text. Instead of reading my mind, please re-read the title of the section.

" re: Do you not think this is an endemic and insoluble problem?" It is an edendemic problem for people who look down an folks like me <"if you are dumb, it is not my problem", RTFM>. It was not endemic, say, for Isaac Asimov or Richard Feynman, who had a great knack of discosing "a secret code". Staszek Lem (talk) 20:47, 19 February 2013 (UTC)

Staszek Lem, though your post in terms of "sucks bigtime" was perhaps not the most diplomatic, I recognize that it made a useful point. The concept of temperature is not child's play. Underneath it is an intuitive understanding of the character of a 1-manifold. Each temperature is a physical quantity, but all temperatures are related because they can be referred to the hotness manifold, which is a pure abstraction, that Aristotle would have called an attributive universal. This is one of the underlying ultimate abstractions of the idea of temperature. It was perhaps first put into so many words by Ernst Mach, though it was considered by other writers before him, but not in so many words. In due course, I will try to smoothly incorporate into the article this idea that you have suggested. It is not always easy to do such things.Chjoaygame (talk) 00:35, 20 February 2013 (UTC)

Thanks fro finally stopping seeing my comments as personal insults. Here is another argument why the intro "sucks big time". Let me remind you that someone else mentioned here that the first sentence is not the definition of temperature, but rather description. Saying "A" you maust say "B". It is the description of how the temperature was understood initially, i.e. historically. It is rather naive to understand temperature of a molecule as its "hotness" - it is our anthropomorphisazion of the Universe, akin to attributing "color" to quarks. Once physicists gave a definition of "temperature", it starts living its own life, related to "stone age" perceptions, but beyound them in areas out of immediate touching by bare hands. The same in mathematics, a "strainght line" drawn by a pencil in not the same as a 1-dimensional Euclidean space. True understanding of the concept is impossible without understanding (and describing) its evolution. Otherwise "rocket science" is indistinguishable from "woodoo science" (and no wonder the latter one is more credible to average Amercian TV watchers). Staszek Lem (talk) 01:38, 20 February 2013 (UTC)

Now you are accusing me of "seeing [your] comments as personal insults". My response to that is: your post did not lead me to have any personal concern; no further comment from me here about that. Your post in terms of "sucks bigtime" was not diplomatic and you could have expected, as apparently from your above accusation you do, that it might offend. Then you seem put out that it does not elicit a very warm and friendly response. Then you repeat it; what should I make of that? Reading the rest of your comment makes me see you as someone who likes to lecture others; in English we would say that you like to teach your grandmother to suck eggs; that is just how your writing style comes across, a style which is your choice. I reject much of your lecture, for reasons that I will not state now. Nevertheless, I recognize that a more abstract framing of parts of the article is reasonable and feasible, and I will, when it seems opportune, try to do something about it.Chjoaygame (talk) 05:05, 20 February 2013 (UTC)

Staszek Lem you write (above):-

How the heck you have come with the notion that I am trying to decry something...

What you did was delete here a pointer to the fundamental relation between energy and temperature (the Boltzmann constant) without any justification, that is what I meant when I wrote "please do not decry the deeper aspects of physics to be found in a good encyclopedia article"

I have no idea why you deleted this reference, the matter (and importance) is hardly mentioned in the article, which is a major defect. Perhaps you disagree about the Boltzmann constant, would you care to say why? --Damorbel (talk) 06:56, 20 February 2013 (UTC)

what is temperature?

The new lead gives not the slightest idea of what temperature is. The new lead lists a few features of temperature, and shows to some extent how it is related to heat.Chjoaygame (talk) 02:10, 24 January 2013 (UTC)

I think "hot/cold" is gives an intuitive idea for what temperature is, sufficient for the lead. If you want to get into a rigorous definition, that should wait till later. PAR (talk) 06:08, 24 January 2013 (UTC)

Is this a hot potato? I mean, this is a risky area, as we have seen, but perhaps something more might safely be said?Chjoaygame (talk) 06:57, 24 January 2013 (UTC)

I think relating the temperature to the translational kinetic energy would be good. In the past, when that language appeared, someone would point out that it's not strictly true under this or that condition. Could we safely use gas as an example, saying "temperature of a gas is proportional to translational KE (even a formula maybe)" and make some statement about more complicated materials? Spiel496 (talk) 16:26, 24 January 2013 (UTC)

I have no problem relating temperature to kinetic energy, as long as its not presented as a definition of temperature. The nitpicks don't even have to be explicit, just make it clear that is not a definition of temperature, and it falls apart sometimes.PAR (talk) 16:49, 24 January 2013 (UTC)

If it appears in a section, and especially in the lead, as the only detailed physical indicator of what temperature is, then, no matter how carefully one tries to make it clear that it falls apart sometimes and that it is not a definition of temperature, it will be treated as such. To suppose otherwise is unrealistic. A very careful statement will be criticized as "too complicated", and airbrushed until it looks like a direct definition. To suppose otherwise is unrealistic.Chjoaygame (talk) 17:27, 24 January 2013 (UTC)

My apology. I wrote just above "will be criticized as ″too complicated″, and airbrushed". I should have written "has already been airbrushed uncriticized". The airbrushing was complete before I wrote just above. I had been working through the entries from earlier to later.Chjoaygame (talk) 17:40, 24 January 2013 (UTC)

The airbrushed version is loose, inaccurate, and vague.Chjoaygame (talk) 00:25, 25 January 2013 (UTC)

I came here to see what is temperature and didnt understood anything. Actually I kinda know that this is unknown - much same as energy - on the energy page at the definition it says - "It is important to realize that in physics today, we have no knowledge what energy is. We do not have a picture that energy comes in little blobs of a definite amount.". Would be nice to have a similar statement if such is true. Hotness and coldness are just observable effects of the phenomenon not the phenomenon. Same with gravity field. — Preceding unsigned comment added by 79.113.162.7 (talk) 08:52, 22 March 2013 (UTC)

Text Books as References

I have reverted the addition of a textbook as a reference for the following reasons:

1/ The editor gives no reason for this reference and no citation to show why the ref. supports the Wiki article.

2/ The ref. itself is not available on line for examination by users of Wikipedia.

3/ There are far better refs. freely available e.g. the ref. to Maxwell's 'Theory of Heat' but 'The Mechanical Theory of Heat' by Rudolf Clausius and 'Lectures on Gas Theory' (Ludwig Boltzmann) are also available.

Please note this is not a general attack on text books as references but on citing them in such a way that the intellectual contents is inaccessible from inside Wikipedia. --Damorbel (talk) 09:05, 9 April 2013 (UTC)

Reason #2 is not Wikipedia policy; see WP:SOURCEACCESS. Reasons #1 and #3 are not standards that I've ever seen enforced. Spiel496 (talk) 20:04, 9 April 2013 (UTC)

not Wikipedia policy

Really? I do not think that 1/ failure to explain the value of a ref. "needs to be enforced" (!) Or 2/ can be considered a useful contribution. And 3/ surely only the better refs. are acceptable in Wikipedia?

PS Do you approve the (deleted) ref.? --Damorbel (talk) 20:50, 9 April 2013 (UTC)

Did you make a typo? I can't follow your paragraph with all the questions.

In answer to your final question, Yes, from what I can tell from Google Books, it looks like a relevant passage. And the editor who added the ref is not known for link-spamming. So, until I get off my butt and check the book out of the library, I'm giving Chjoaygame the benefit of the doubt. Spiel496 (talk) 22:14, 9 April 2013 (UTC)

until I get off my butt and check the book out of the library, Just so! The butt belongs to you.

Surely the whole point of Wikipedia is to provide access, if possible, without a library? That is the non-trivial improvement I'm suggesting, no need to 'get-off-your-butt'; see? --Damorbel (talk) 06:34, 10 April 2013 (UTC)

The "whole point" is to provide solid information based on reliable sources. Those sources need not be available online. A book published by a reliable publisher is a valid source, even if it is not easily accessible online through Google books or some website. That is the point of WP:SOURCEACCESS and the essay Wikipedia:Offline sources. See Wikipedia:WikiProject Resource Exchange/Resource Request for assistance. This is not the place to change Wikipedia policy. Vsmith (talk) 11:27, 10 April 2013 (UTC)

This is not the place to change Wikipedia policy

I agree. Why are you raising it?

The author of Wikipedia:Offline sources puts it this way:-

Special care should be taken when using offline sources. Make sure to provide full bibliographic information, often by using a fully-filled out citation template, like {{cite book}} or {{cite news}}. Complete information helps Wikipedia's readers find the source when they need it, and also increases the source's credibility among the Wikipedia editing community (who may otherwise be skeptical of its reliability). Second, use the quote= parameter within those citation templates to provide some context for the reference. This is especially important when using the off-line source to support a fact that might be controversial or is likely to be challenged.

My only complaint is the source was not supported, only page numbers. Surely the contributor can do better than this? Why is this author cited, has he contributed to the developement of thermodynamics or is he a PhD student trying to earn a bit of life support? If a reference is to be suitable for any purpose the contributors have to make an effort to get the best and explain why. --Damorbel (talk) 12:13, 10 April 2013 (UTC)

I have undone the most recent edit.

The revision [1] is quite mistaken when it refers to the appellation absolute arising because it ' it is defined independently of the properties of any particular thermometric substance. ' The name comes from it being the lowest possible temperature i.e the temperature at the zero point.

There are two widely accepted absolute temperature scales Kelvin and Rankine, the zero points being 0K and 0R repectively. To get the scale interval both scales use as reference point the triple point of water, respectively 273.16K and 491.688R.

It is conceivable that other reference points could be used, indeed may well be used in the future since all reference points are subject to inaccuracies, but since temperature is a measure of particle energy it is not possible to separate it from the properties of any particular thermometric substance! --Damorbel (talk) 10:46, 16 April 2013 (UTC)

In case any doubt exist on this they should be supported by evidence that, in equilibrium, the temperature of a composite material is a function of the diverse properties of the materials making the composite. --Damorbel (talk) 13:48, 16 April 2013 (UTC)

Carnot Engine

Hi,

My name is Pete. I'm a science teacher currently teaching chemistry. I have an excellent chemistry background, but I'm limited in Thermodynamics (from a Physics point of view at least). I was reading this article on Temperature for a lesson on Temperature and the Kelvin scale and their relationships to gases. I have read some really difficult astrophysics articles and have been able to grasp the concepts somewhat. This article on something that has been studied for over a century, however, is very difficult for me to grasp. I believe that the language is somewhat difficult if you're not an expert on all the laws of Thermodynamics. Perhaps a diagram of the Carnot engine and the interaction of the heat reservoirs would make things a little easier for the layperson to understand.

For the record, I believe that those of you who contribute your knowledge to Wikipedia generally do a great job of phrasing things. I also believe that the knowledge Wikipedia holds should be available to everyone, especially high school kids who would benefit greatly if articles were written with the average student in mind.

Keep up the good work and I hope what I have said somehow helps.

Pete S. — Preceding unsigned comment added by 74.117.253.18 (talk) 09:35, 3 June 2013 (UTC)

Thank you for your suggestion, Pete S. I have in response added links to the articles on the Carnot engine and on the Carnot cycle. I have made some changes to the wording of the present account. Yes, I accept that it is still rather technical. The Kelvin scale does not refer to an ideal gas thermometer. An ideal gas thermometer might be considered to lead to the idea of an absolute zero of temperature, as the volume of the gas fell to zero with falling temperature.Chjoaygame (talk) 14:24, 3 June 2013 (UTC)

spark

Spiel496 has here restored a sentence that was twice properly challenged for lack of sourcing. His reason for restoring was that he thought that, rather than delete every unreferenced phrase, it would be preferable to just find a citation. If Spiel496 is for real about this, one would expect that he would forthwith supply a reliable source. It is not for editors to post what strikes them as fine rhetoric, and demand that others find a reliable source for it; that way the Wikipedia would be a mess. Editor Spiel496 followed up his restoration of the challenged sentence not by finding a reliable source, but by changing the sentence that he had restored, altering one of the prime points of the original, removing the reference to briefness. He thereby admitted that the sentence that he restored was not good enough as he restored it. A hunt for a reliable source for a moving target is not so easy.

The task of a Wiki editor is to find suitable material, with reliable sourcing, and to post it appropriately. When unsourced material is twice challenged, the right response is either to post at once a reliable source for it, or to remove it until a reliable source is found for it, not to leave it in place and ask someone else to find a source for it.

The sentence that Spiel496 restored was not appropriately posted and even if it were reliably sourced it should not stand in the place where Spiel496 restored it. It was posted in the lead, which is reserved for summary of the body of the article. The sentence was about sparks, which are not mentioned in the body of the article. Therefore the restored sentence was not in the appropriate place in the article. Moreover, the 'temperature' of a spark is a questionable notion, because a spark is very finely localized in a way that makes risky a definition of its temperature. This question is not dealt with in the body of the article. Such a risky example is hardly suitable for the lead, even if it is discussed in the body of the article.

For these reasons I have undone Spiel496's restoration of the sentence.Bridgeroad (talk) 05:09, 7 June 2013 (UTC)

That sentence 'temperature of spark is very briefly equal to that of the sun' attracted my attention. I googled but couldn't find ref. That sentence should not be in article without reliable ref. neo (talk) 06:54, 7 June 2013 (UTC)

Not finding a source in Google about speculation for a spark at about 6000K is absolutely no reason for deleting such speculation in a Wiki article. It is perfectly possible for a spark to have a temperature of 6000K, there is nothing that prevents material achieving such high temperatures, the Sun itself can do this through radiation. I assure you that nuclear fusion (or fission) exceed this by multiple orders of magnitude. (Did your Google search include fission/fusion reactions? Did you ever deal with lasers?). I am afraid that your Google searches do not constitute a reliable source. Do please discuss these matters. --Damorbel (talk) 12:19, 7 June 2013 (UTC)

I have restored the edit by Spiel since he has provided a suitable ref. on what is a highly relevant matter. The illustration of temperaure as an 'intensive' property i.e. local, is extremely important, quite important enough to appear in the opening section of any encyclopedia. --Damorbel (talk) 07:37, 12 June 2013 (UTC)

hmmm... OK. As it is sourced and explains rather difficult term by example, I have no objection to keep it in lead. neo (talk) 07:50, 12 June 2013 (UTC)

Agree, with the citation it is a reasonable example of characteristics of an intensive property. The lead still summarizes the more detailed discussion of the concept later on; there is no need to use the exact same example twice. VQuakr (talk) 08:09, 12 June 2013 (UTC)

Section "An intensive variable, local when local thermodynamic equilibrium prevails"

This section [2]

An intensive variable, local when local thermodynamic equilibrium prevails

contains many defects as listed below, and no merits that are not handled elswhere, it will shortly be deleted.

1/ In thermodynamic terms, temperature is an intensive variable because it is equal to a differential coefficient of one extensive variable with respect to another, for a given body. It thus has the dimensions of a ratio of two extensive variables.

It certainly is not.

There is no ref. given for this. The ref. that should be given is the Boltzmann constant which is the energy per particle (k). A particle is the smallest possible microscopic thermal system and it is the smallest physical unit that can be assigned a temperature.

2/ In particular, when the body is described by stating its internal energy U, an extensive variable, as a function of its entropy S, also an extensive variable, and other state variables V, N, with U = U (S, V, N), then the temperature is equal to the partial derivative of the internal energy with respect to the entropy:

This is a basic misunderstanding of entropy. Entropy is a system property, to determine the entropy of a thermodynamic system the energy distribution throughout the entire system must be taken into account; this is the complete opposite of temperature which can be different in all regions of the system, that is why it must be an intensive property.

3/ It makes sense, for example, to say of the extensive variable U,...[a density per unit volume]

This is meaningless because there is no inherent restriction on the distribution of energy in a thermodynamic system.

4/ or of the extensive variable S, that it has a density per unit volume,

Also meaningless because entropy is essentially a property of the whole (by definition) thermodynamic system.

5/ or per unit mass, but it makes no sense to speak of density of temperature per unit volume or per unit mass. Then it will be removed.

6/ On the other hand, it makes no sense to speak of the internal energy at a point, while when local thermodynamic equilibrium prevails, it makes good sense to speak of the temperature at a point. In this sense, temperature can vary from point to point in a medium that is not in thermodynamic equilibrium, but in which there is local thermodynamic equilibrium.

Similarly this contributes nothing to the article - it is merely POV. It is a complete waste of time to say what does not make sense.

7/ This last paragraph:-

Thus, when local thermodynamic equilibrium prevails in a body, temperature can be regarded as "a spatially varying local property in that body", and this is because temperature is an intensive variable.

is complete nonsense. How can an intensive property that is "a spatially varying local property in that body" be simultaneously a property of that body? Further, if, as the article has it, "local thermodynamic equilibrium prevails in a body" then there is only one temperature applicable to the system because that is the definition of equilibrium. --Damorbel (talk) 13:02, 12 June 2013 (UTC)

Dear Damorbel, Last time you undid an edit of mine, it turned out that you had not read the edit that you undid. Therefore I feel I need to ask you to read this edit again. It expresses a very orthodox view, almost I would say the canonical view. There is nothing controversial or specific to my own personal view here.

I will not right now address in detail your extensive criticism just above. Most of your criticism seems to be due to your unfamiliarity with the orthodox view on the nature of intensive and extensive variables, especially as it relates to temperature. Most standard texts on thermodynamics cover this. It is perhaps useful to distinguish between an introductory description of an intensive variable at the beginning of a text, and a precise and full definition of an intensive variable, which will be found deeper into the text. I will just make one specific comment about your criticism, on the last point you offer, point 7/. My edit wrote "when local thermodynamic equilibrium prevails in a body", but your criticism read that as referring to global thermodynamic equilibrium in the body. It seems you are unfamiliar with the widely used concept of local thermodynamic equilibrium, as distinct from global thermodynamic equilibrium, which of course entails homogeneity of all intensive variables if there is no externally imposed force field, and which of course entails homogeneity of temperature even when there is an externally imposed force field. The notion of local thermodynamic equilibrium is an important ingredient in the idea that one can have a local temperature in an inhomogeneous system. Texts on this which you may find useful are

Gyarmati, I. (1970). Non-equilibrium Thermodynamics. Field Theory and Variational Principles, translated by E. Gyarmati and W.F. Heinz, Springer, Berlin.

Glansdorff, P., Prigogine, I., (1971). Thermodynamic Theory of Structure, Stability and Fluctuations, Wiley, London, ISBN 0-471-30280-5.

Chjoaygame (talk) 15:42, 12 June 2013 (UTC)

Chjoaygame:-

1/ you write:-

There is nothing controversial or specific to my own personal view here.

It is to the insertion of your POV in Wikipedia that I am taking exception. Your frequnetly give no refs., this renders it almost impossible to discuss your contributions because they are your thoughts alone and you alone judge them suitable for Wikipedia, you clearly see any comments as a personal attack.

2/ You write further:-

I will not right now address in detail your extensive criticism

which fits very nicely with your previous declarations that you will not discuss [Wiki articles] with me.

3/ Yet again:-

which of course entails homogeneity of temperature even when there is an externally imposed force field.

Do you include gravity in the possible "force fields"? Then all the evidence (and the theory!) points to the existence non-homogeneous temperatures, the progressive rise in the sun's temperature towards its core is a good example.

If you are having "difficulty ... right now address in detail your ... criticism", are you able to give some idea when I can read your response? --Damorbel (talk) 17:50, 12 June 2013 (UTC)

Dear Damorbel, you write to me that "Your frequnetly give no refs." In fact, of the 68 citations in the present article, 48 or so were supplied by me. I did not give references in the initial version of the edit under present discussion because I felt what I wrote was obvious orthodoxy. Now I have supplied 9 references for my edit.

You write above that "Do you include gravity in the possible "force fields"? Then all the evidence (and the theory!) points to the existence non-homogeneous temperatures, the progressive rise in the sun's temperature towards its core is a good example." Yes, dear Damorbel, I include gravity in the possible "force fields". But it is well accepted in thermodynamics that in the presence of a gravitational field a body in its own thermodynamic state of internal equilibrium has a uniform temperature. (Maxwell, J.C. (1867). Gibbs, J.W. (1876/1878), pp. 144-150; Boltzmann, L. (1896/1964), p. 143. Bailyn, M. (1994), pp. 254-256. Chapman, S., Cowling, T.G. (1939/1970), Section 4.14, pp. 75–78. Coombes, C.A., Laue, H. (1985), A paradox concerning the temperature distribution of a gas in a gravitational field, Am. J. Phys., 53: 272–273. Román, F.L., White, J.A., Velasco, S. (1995), Microcanonical single-particle distributions for an ideal gas in a gravitational field, Eur. J. Phys., 16: 83–90. Velasco, S., Román, F.L., White, J.A. (1996). On a paradox concerning the temperature distribution of an ideal gas in a gravitational field, Eur. J. Phys., 17: 43–44.) On the internet you will find many sources which deny this, but they are not reliable, and are not familiar with basic thermodynamics. Yes, dear Damorbel, the temperature in the sun is inhomogeneous, but that is not simply because of gravity; it is mainly because the sun is not in global thermodynamic equilibrium; many calculations about the sun are, however, made using the assumption of local thermodynamic equilibrium; one of the first to make this clear was E.A. Milne (1930, Thermodynamics of the Stars, in Handbuch der Astrophysik, vol. 3, Part I, Chapter 2, pp. 65–255).

You write above "If you are having ″difficulty ... right now address in detail your ... criticism.″" I did not use the word "difficulty"; you are misquoting me there. The reason that I will not right now discuss in detail your extensive criticism is that I think you have not read the basic references on the subject, and have not read my edit with fair care and attention, and I do not think it useful to try to discuss it with you until you have done so and until you have made yourself more or less familiar with the basic ideas of thermodynamics. I have tried in the past long and hard to discuss things with you, but I have nearly always found, to my sorrow, that it is a waste of time, because of the way you respond. You write that that I insert my POV in Wikipedia; mostly I follow carefully the most orthodox and rigorous standard texts, and take care to check references, often back to original sources. It is because you are unfamiliar with standard texts on thermodynamics that you read my edits as my personal POV; there is no substance in your unjust allegation that they are my personal POV.

I will be willing to further discuss this with you when you show good evidence that you have familiarized yourself with the basic ideas of thermodynamics, and have carefully read my edit with those ideas clear in your mind. At present your comments make it obvious that you are not clear in your mind as to the differences in scope and approach between (1) equilibrium thermodynamics, (2) non-equilibrium thermodynamics, (3) kinetic theory, and (4) statistical mechanics. My present edit restricts itself, as it advertises, to the thermodynamic approach, and it does not venture into kinetic theory or statistical mechanics. Kinetic theory does deal with both equilibrium and non-equilibrium problems. Statistical mechanics, for the most part, restricts itself to equilibrium problems. Sad to say, there is in the present article no systematic account of the kinetic theory approach to temperature. As I understand you, you feel that the kinetic theory approach is the uniquely preferred one, but you do not recognize it as distinct from the thermodynamic approach, a distinction that is well recognized by most writers. As I have mentioned before, no one is stopping you from writing a systematic account of the kinetic theory approach to temperature into the present article.Chjoaygame (talk) 18:49, 12 June 2013 (UTC)

Chjoaygame surely this just a personal attack? When you write:-

when you show good evidence that you have familiarized yourself with the basic ideas of thermodynamics

and I think you have not read the basic references on the subject,

Please a/ stick to the matters of the article; and b/ answer the points I have indicated.

Adding the references after I remarked on their absence does not explain the 7 contradictions and points I have made.

Please answer them 1/ to 7/.

Saying I am ignorant is an insult, not an answer. --Damorbel (talk) 20:58, 12 June 2013 (UTC)

I regret that I am unable to make a useful reply to this.Chjoaygame (talk) 21:45, 12 June 2013 (UTC)

I think you can.

The point you seem to include in the article is the role of temperature in Non-equilibrium thermodynamics. I agree. But it is not helpful to mix up the two, they are sufficiently distinct to merit separate sections.

There is a good case for making a section dealing with equilibrium conditions where the energy of the particles is uniform (or Maxwell Boltzmann) i.e. uniform temperature, and another with non-uniform conditions for example planetary atmospheres which are retained by a gravitational field or choked flow e.g. a rocket engine nozzle where the accelerating forces acting on the hot gases lead to a temperature and pressure gradients.

In both cases the temperature of the gas is proportional to the kinetic energy of the particles. In the accelerating field, gravitational or pressure gradient, the temperature of the gas is no longer uniform because the particle energy (proportional to velocity squared) is dependent on the position in the field. --Damorbel (talk) 06:14, 13 June 2013 (UTC)

Editor Damorbel writes just above "In both cases the temperature of the gas is proportional to the kinetic energy of the particles. In the accelerating field, gravitational or pressure gradient, the temperature of the gas is no longer uniform because the particle energy (proportional to velocity squared) is dependent on the position in the field." I can hardly add usefully to what I have written above ("I include gravity ...) with 8 references about that. I have split the edit into two sections.Chjoaygame (talk) 21:09, 13 June 2013 (UTC)

Vibrational energy and temperature.

The energy in 'vibrational degrees of freedom plays no role in temperature because molecular energy is divided over all available degrees of freedom; change of temperature reqires that the energy in ALL degrees of freedom changes simultaneously. Vibrational degrees of freedom are supplemental to the translational (X Y Z) DoF so although the is more energy in a molecule with vibrational modes, the energy per DoF remains the same function of temperature. --Damorbel (talk) 13:50, 23 June 2013 (UTC)

Can you be more clear about your objection to the paragraph you removed? It speaks in general terms about how temperature is associated with the rapid movement of particles. Vibration is mentioned only once. What part is incorrect? Spiel496 (talk) 05:42, 25 June 2013 (UTC)

It is a section about statistical mechanics yet it contains only matter connected kinetic theory and without any references supporting anything in the contribution; as I remarked at the time:-

I removed section referring to the connection between vibrational energy and temperature because there is no connection. The section contained no ref. , it was pure POV without relevant support of any kind. (See Talk Page)

This kind of 'POV stuff' is not at all suitable for Wikipedia so I removed it. Rewrite it if you wish but please do better than the original. --Damorbel (talk) 10:14, 25 June 2013 (UTC)

This edit

Sorry Chjoaygame, you claim my edit was inaccurate, so you removed it explaining: (removed inaccurate "statistical mechanics"; removed lazily cribbed but inaccurate reference to Maxwell p. 2) The text exists at the refenced place in all editions of Maxell's 'Theory of Heat' so I am replacing what you deleted. It is sound practice when quoting a source to include the relevant text, don't you agree?

Further my observation in connection with statistical mechanics is equally relevant since temperature is at the root of statistical mechanics also, so I am replacing it. --Damorbel (talk) 10:00, 25 June 2013 (UTC)

Damorbel, your undo here is mistaken.

Your undo restored the phrase "statistical mechanics" and restored the reference to Maxwell page 2, as follows: "In kinetic theory and in statistical mechanics, temperature is a measure of the kinetic energy of microscopic particles [ref]Maxwell, J.C. (1871). Theory of Heat, Longmans, Green, and Co., London. p. 2.[/ref] such as atoms, molecules and photons."

If you look on page 2 of Maxwell 1871, as you apparently did for your recent change to the first sentence of the lead, you will note that that page 2 does not mention kinetic theory or statistical mechanics or microscopic particles. So the reference was inaccurate. It was copied by some lazy cribbing editor to its place from which I removed it. Evidently, that lazy cribbing editor didn't bother to read the reference that he inserted.

Again, statistical mechanics treats temperature as a parameter of a distribution, more or less along thermodynamic lines, not as something explicitly about particle kinetic energy; so the sentence from which I removed it was inaccurate. Your comment above about the root of statistical mechanics does not address the sentence in question and so is irrelevant and a red herring.

Because of your undo, I have now looked back over the record, to find who was the lazy editor who cribbed the Maxwell page 2 reference, who was not identified in my removal cover note. Now I know who it was.Chjoaygame (talk) 22:12, 25 June 2013 (UTC)

I suggest your logic is faulty. Merely because the citation does not mention statistical mechanics or kinetic theory it changes precisely nothing. In statistical mechanics temperature is a function of the probability of a particle occupying a given state, which is still due the kinetic energy of a particle i.e. its temperature. The same applies kinetic theory, there is no physical distinction . You may wish to insert this further down in the article, but it is innapropriate to put any distinction in the opening statement because it would cause confusion in those unfamiliar with the niceties of kinetic theory and statistical mechanics, they are about exactly the same thing! --Damorbel (talk) 11:52, 26 June 2013 (UTC)

Dear Damorbel, your answer is still mistaken. Not only does the cited reference on page 2 not mention kinetic theory or statistical mechanics, it also does not mention particles. Therefore it is not a suitable reference. It was cribbed by its lazy editor. The difference between kinetic theory and statistical mechanics is not a fine nicety that might confuse the average reader. They are not about exactly the same thing. They have a mighty difference of approach, and to put them mistakenly together as is done in your undo is to gratuitously invite confusion or to mislead.

Your suggestion that my logic is faulty is mistaken. Your undo is unacceptably faulty and should be undone. I will not further pursue this matter here for reasons I have given before, reasons which your answer here illustrates.Chjoaygame (talk) 20:30, 26 June 2013 (UTC)

well-intended edits which "correct"

Three edits "corrected" the article, here, here, and here.

The editor who made these edits is evidently well motivated, but has not thought through an adequately sound basis for any of his three edits.

The first edit added to the lead the sentence "Scientifically, temperature is the measurement of average kinetic energy within a body, starting at 0 Kelvin/-273.15°C." The sentence is inappropriately placed in the lead. It is vaguely and inadequately worded to express what it intends. It is rarely true. And it is misleading.

The sentence means to refer to the average kinetic energy of particles within the body, but does not say so. The phrase "average kinetic energy within a body" as it stands is nearly meaningless. Very few measurements of temperature work by actually measuring the kinetic energies of particles; some few that do are mentioned and referenced in the article. And it does not express the standard fundamental definition of temperature, which is indicated in the last sentence of the first paragraph of the lead: "The fundamental physical definition of temperature is provided by thermodynamics." Not by kinetic theory as the edit indicates.

The second edit replaced the word "coldest" when referring to the absolute zero with the word "lowest". The reason offered was that coldest is not a scientific term, that cold is a perception, not a scientific state. To use this as a reason is to call upon the idea that all words in the article should be scientific terms and must not refer to perceptions. That is not an adequate reason. There is no rule against referring to perceptions, and it is not the case that cold refers only to perceptions. The article used the word "coldest" instead of the word "lowest" because of the existence of so-called "negative temperatures". True, the term 'negative temperature' is to some extent an abuse of language, but it is more or less accepted in specialist physics. Accepting the term, it is the case that components with negative temperature have numerically lower temperatures, but they are not colder than absolute zero of temperature. They can pass energy to other components with colder temperatures, according to the second law; they are hotter than, not colder, than absolute zero. They are physically hotter, not colder, though numerically lower in temperature, than absolute zero. Accepting the term 'negative temperature' makes it preferable to say that absolute zero is the physically coldest temperature, and this is scientific enough.

The third edit changed the sentence "It cannot be achieved in any actual physical device" with the sentence "It has not, and is unlikely to be achieved in any actual physical device." That replacement is a near denial of the third law of thermodynamics, which says that the absolute zero cannot be reached in a finite number of steps. Actual physical devices can make only a finite number of steps, and consequently upon the third law cannot achieve the absolute zero of temperature.

Consequently I have undone the three edits.Chjoaygame (talk) 15:06, 28 July 2013 (UTC)

kinetic theory in the lead

It is good to see you working on this. I am not right now intending to do much here. But still I will comment on what you have written. It is a bit vague and tactful, not so much precise and informative; it is not so clarifying as polite. You could have indicated the grave and important limitations of kinetic theory more concisely in the lead, which is to be a summary of the body of the article, not a free essay in its own right. What is a simple system? One that kinetic theory talks about? Why does an ideal gas deserve to be considered as a physical system at all, why is it not just a mathematical model? Why is a solid not simple? Is simplicity an adequate account of what matters here? The harder and more important questions are just what does kinetic theory refer to, and how nearly valid is it, as an account of temperature? The limitations and weaknesses of kinetic theory are not made clear in the section on it in the body of the article, where they should be. The lead is not the place to introduce a subject. The article on kinetic theory is also very weak in this direction. Some soundly researched sourcing is badly needed.Chjoaygame (talk) 14:50, 1 August 2013 (UTC)

Hi Chjoaygame. I agree that it needs work, it's too much, and I'm not married to the term "simple"—maybe you can improve it if you have time. I just wanted to get something in there so as not to mislead the reader into thinking that kinetic theory and T proportional to mean KE is true in the general case. The goal isn't just to say something that's technically true, but also something that is most likely to convey reasonably good information to the casual reader. DavRosen (talk) 17:50, 1 August 2013 (UTC)

Ok. Research on good sources still in progress.Chjoaygame (talk) 03:08, 2 August 2013 (UTC)

reasons for undo of good faith edit

I have undone this good faith edit. It may appear that this edit is putting the same basic idea as was put by a very recent previous edit, also undone by me. My reasons are as follows.

To a paragraph of the already long lead, the edit adds the words in blue:

Within a body that exchanges no energy or matter with its surroundings, temperature tends to become spatially uniform as time passes. All bodies above absolute zero emit energy, but warmer bodies emit more energy than colder. A warm body in cold surroundings will emit more heat than it absorbs and therefore have a net energy emission. A cold body in warm surroundings will absorb more energy than it emits and therefore have a net energy uptake. When a path permeable only to heat is open between two bodies, the net energy always transfers spontaneously as heat from a hotter body to a colder one. The transfer rate depends on the thermal conductivity of the path or boundary between them. Between two bodies with the same temperature, no net heat flows. These bodies are said to be in thermal equilibrium.

The edit that I have undone intends to expound a view of how energy is transferred as heat. It is a good view, but is not in accord with the thermodynamic definition of transfer of energy as heat. It belongs in other areas of physics. The thermodynamic view is simply that heat is already a net transfer. In contrast, the edit intends to admit that the net transfer is the sum of two oppositely signed one-way transfers, as it were. Thermodynamics does not work with such conceptual unbalanced two-way transfers. This is because it has no means of saying how great each of them is. It is part of the thermodynamic idea of heat that its detailed mechanism is uncontrolled and unknowable, while the idea of the edit is to focus on its proposed detailed mechanism, an unbalanced two-way exchange. The idea of an unbalanced two-way transfer is physically reasonable, especially for radiative transfer, but it goes into mechanism in a way that is eschewed by thermodynamics. That idea belongs to other areas of physics, such as the theory of radiative transfer, and of kinetic theory. These areas do not contradict thermodynamics, but they are not considered by it. This eschewing of consideration of mechanism is a strong point of thermodynamics, because it means that thermodynamics does not rely on models of mechanism for its validity. That is to say, thermodynamics has a strong positive reason to avoid such consideration. Thermodynamics is the primary base of the idea of temperature.

Some consideration of transfer of energy as heat is appropriate in an article on temperature, because the idea of temperature is tightly coherent with the idea of transfer of energy as heat. It is possible to consider transfer of energy as heat even when temperature is definable for only one of the systems in the transfer. But it hardly makes sense to think of temperature when transfer of energy as heat is not admitted as prior.

The detailed mechanism of transfer of energy as heat is considered under the heading of kinetic theory, and that is the place for exposition of the ideas of the edit that I have undone, but not in the lead of an article on temperature.Chjoaygame (talk) 21:24, 22 August 2013 (UTC)

A paragraph that bothers me

I have only been editing Wikipedia for a couple of months, and thus far have made only minor edits. I really don't know how to behave on Wikipedia yet. But here I found a paragraph I would like to change. It is in the section:

In theoretical foundation >> Zeroth law of thermodynamics

Does anybody mind if I completely redo the paragraph?

Here are the paragraph's faults:

1. "The usual textbook statement" is not a good way to begin.
2. I need to know if people actually use gas thermometers to calibrate. I find it hard to believe since we have so many simpler ways to calibrate (e.g., triple points ect).
3. The paragraph an mention of gas thermometer is very important from a philosophical and probably historical point of view. It is likely that this is how people first identified absolute zero, and is certainly a great way for students to encounter the subject.

Here is the paragraph: The usual textbook statement of the zeroth law of thermodynamics is that if two systems are each in thermal equilibrium with a third system, then they are also in thermal equilibrium with each other. This statement is taken to justify a statement that all three systems have the same temperature, but, by itself, it does not justify the idea of temperature as a numerical scale for a concept of hotness which exists on a one-dimensional manifold with a sense of greater hotness. Sometimes the zeroth law is stated to provide the latter justification.[48] For suitable systems, an empirical temperature scale may be defined by the variation of one of the other state variables, such as pressure, when all other coordinates are fixed. The second law of thermodynamics is used to define an absolute thermodynamic temperature scale for systems in thermal equilibrium.---guyvan52 (talk) 02:35, 4 January 2014 (UTC)

Go for it! The proper Wikipedia jargon is be bold. Remember to preview your text before saving, and it's a good idea to have a local copy of your text if you have done a bit of work because stuff happens, and if a glitch occurs when editing it can be rather alarming, and that leads to the loss of what you typed. This article has seen quite a bit of back-and-forth—I have not paid much attention, but I got the impression that a number of people believe they have great insights on what temperature really is, but putting it into words (with reliable sources) can be elusive. If you are reverted, don't take it personally—the matter can be discussed here. Don't worry about any technical matters like correct syntax as someone will fix it. Johnuniq (talk) 02:52, 4 January 2014 (UTC)

Changed the statements about gas thermometer

In my rewrite, I am trying to rearrange what was already written. (For example, the ideal gas law is important to the kinetic theory, but not so much to the first law of thermodynamics).

But I felt compelled to take the liberty of softening the importance of the gas thermometer as a calibration device. Though not an expert, I have been in enough labs to believe that they are not used in practice. The important thing about the gas thermometer is that it is a theoretical device that defines temperature, at least for any object in contact with the ideal gas. (An this is where the zeroth law comes in)guyvan52 (talk) 04:44, 4 January 2014 (UTC)

quality prose in need of a place in wikipedia

I deleted this because it was placed in the wrong section. Perhaps put it into Atmospheric temperature?

• Many factors control the annual temperature range of a region, including latitude, water content, aridity, biotic community, etc. Water has a very high specific heat capacity – the second highest among all the heteroatomic species (after ammonia), as well as a high heat of vaporization (40.65 kJ/mol or 2257 kJ/kg at the normal boiling point), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. Thus, the tropical regions nearest to the equator and ocean tend to have the smallest annual temperature ranges with an annual temperature variation as low as 1.5°C. On the other hand, the inland continental areas of high latitudes tend to have the largest annual temperature ranges with an annual temperature variation that approaches 40ºC in some areas.

--guyvan52 (talk) 03:05, 29 January 2014 (UTC)

I think guyvan52 made the right call here.Chjoaygame (talk) 11:53, 29 January 2014 (UTC)

This article's section on Kinetic theory of gasses

Since Wikipedia already has a strong article on Kinetic Theory this article's section needs to focus on Temperature and on keeping it simple. The last paragraph will be condensed, if there are no objections.--guyvan52 (talk) 19:33, 5 February 2014 (UTC)

• Removed comment that ideal gas law demands that temperature is a positive number. [Why say this after already establishing that the ideal gas law establishes a zero a -273C?]
• Focused the discussion exclusively on monatomic gases, except for a link to "degrees of freedom" (without discussion). [This an article about temperature not about ideal gases]--guyvan52 (talk) 20:36, 5 February 2014 (UTC)

For example, a lightning bolt can heat a small portion of the atmosphere hotter than the surface of the sun.

The present lead contains the sentence: "For example, a lightning bolt can heat a small portion of the atmosphere hotter than the surface of the sun.<http://thunder.msfc.nasa.gov/primer/primer2.html>"

The surface of the sun is far from thermodynamic equilibrium. Vast fluxes of energy pass through it. It would be at best dubious and probably would be wrong to try to assign a single definite temperature to it. This is not to deny that it is surely hot. Likewise, it would be dubious to try to assign a single definite temperature to a small portion of the atmosphere heated by lightning. I think this is a poor example for the lead on temperature. It is intended to illustrate that temperature is an intensive variable and can be regarded as varying locally. But an example is not needed for this in the lead, and the one offered in this sentence is a poor one. I would like to delete this sentence from the lead.Chjoaygame (talk) 09:59, 5 February 2014 (UTC)

Maybe at one time it was an illustration that temperature is an intensive quantity, but that language is gone now. I agree that the sentence doesn't improve the article. Spiel496 (talk) 16:26, 5 February 2014 (UTC)

And I agree with both of you. The sentence is both misleading and unnecessary. --guyvan52 (talk) 16:58, 5 February 2014 (UTC)

Speaking of temperature and thermodynamic equilibrium, I will save the sentence in my sandbox because it could someday appear in an improved version of Temperature#Temperature_for_bodies_in_a_steady_state_but_not_in_thermodynamic_equilibrium. That and the next section should be combined and improved. --guyvan52 (talk) 17:17, 5 February 2014 (UTC)

Thank you.Chjoaygame (talk) 01:16, 6 February 2014 (UTC)

perhaps Editor 124.189.16.93 was right

Editor 124.189.16.93 at https://en.wikipedia.org/w/index.php?title=Temperature&diff=next&oldid=597020674 has written "this is wrong". Though his previous edit, at https://en.wikipedia.org/w/index.php?title=Temperature&diff=prev&oldid=597020674 was faulty, it may have been an inadvertent slip of the keyboard. His comment "this is wrong" seems pretty right to me. I think most of the problem is with revisions of equation numbers. I am to blame for this, when at https://en.wikipedia.org/w/index.php?title=Temperature&diff=592414772&oldid=592352067 I tried to rationalize the equations numbering of the article but did not do a complete job. I am sorry for this mistake.

I have now restored the proper equation numbering of the article as it stands. This will perhaps address the problem rightly pointed to by Editor 124.189.16.93. I have to say that the section in question seems pretty chatty to me, and not up to scratch. But at present I not interested in it and don't intend to try to fix it.Chjoaygame (talk) 04:33, 25 February 2014 (UTC)

I think you are correct on two counts:

1. The equations are properly referenced with respect to what is "fundamental" from the statistical physics point of view.
2. The section is "chatty". This is an article about temperature, not thermodynamics. But fixing it is a lot of work because somebody needs to carefully read the other articles on Wikipedia and reference them. If nobody else does it, I will someday go back and start from the Zeroth law of thermodynamics. I went so far as to order from the library and read the reference to the weird phrase:

"one-dimensional manifold with a sense of greater hotness"

Not everything that every professor writes deserves to be in Wikipedia. --guyvan52 (talk) 14:52, 25 February 2014 (UTC)

Though it might be a good thing to do, I think it beyond the call of duty to one article to try to deal with other articles for its sake. Moreover, I think it might very much slow down an attempt to fix that one article.Chjoaygame (talk) 15:55, 25 February 2014 (UTC)

Let's get the Zeroth Law right.

Since one qualified editor reverted the edit of another qualified editor, I propose that we rethink the entire Temperature#Zeroth_law_of_thermodynamics section. At issue is whether we need one or two examples of a state variable that varies with temperature. That can't be resolved until we improve the section. I will begin with a minor edit.--guyvan52 (talk) 17:32, 21 March 2014 (UTC)

Now, we address my real concern: Serrin's statement that the zeroth law "does not (yet) justify the idea of temperature as a numerical scale..." is not universally appreciated. See for example, question 3 on somebody's quiz. After a great deal of thought, I decided that Serrin is correct, but nevertheless was left with a "who cares?" attitude. So we have a choice: Either delete Serrin's idea or better explain it. I could go either way on this question.--guyvan52 (talk) 17:46, 21 March 2014 (UTC)

Here is another take on the same question, from another open source effort: [boundless-open-textbook/thermodynamics]Note how the author(s) make the logical jump from the zeroth law to the existence a temperature scale without explanation. --guyvan52 (talk) 18:00, 21 March 2014 (UTC)

The zeroth law is a name that has been used variously by respected authors, of whom Serrin is one. Different ideas exist as to what the zeroth law says or means. It is a bit like the first, second, and third laws, which are stated variously by different respected authors. Some think they know the one correct statement. The zeroth law as most often stated was invented long before the name was invented; the original invention was not originally labeled as a numbered law. I would favor better explaining Serrin's view rather than deleting it. I think most respected authors would agree with Serrin's physical logic, though they may not agree with his labeling. As far as I can find out, the label was invented by Fowler in reference to the 1935 text of Saha and Srivastava, as noted in the history section of the article on the zeroth law. Saha and Srivastava were talking about temperature as a numerical scale, which is not reflected in the commonest statement of the law, but is reflected in Serrin's statement.Chjoaygame (talk) 18:14, 21 March 2014 (UTC)

Your knowledge on this topic clearly exceeds my own, so I defer to your judgement. I know from your edits on other articles that you like prose to be short and to the point. I share your philosopy. So my question to you is this: Does the insight that "a thermometer takes its own temperature" belong in this section? It's your call.

When you respond, I will put a quick rough draft on this talk page that should not be longer than the current section. It will, however not be so cryptic or jarring to those of us who were (incorrectly) taught that the zeroth law automatically implies the existence of a numerical scale for temperature. For example, after stating the zeroth law, I might say something like this:

A temperature scale can be defined as the numerical labeling of "hotness" on a one-dimensional manifold that extends from "hot" to "cold". The zeroth law is not a sufficient condition for establishing that such a scale can be constructed.[Reference Serrin]

We certainly need to include the pressure of an ideal gas as one example of a suitable state variable. Whether or not the volume of a mercury thermometer should be given as another example depends on tight we can make our argument. Wikipedia has a habit of saying too much. On the other hand, there is a lot that needs to be implied, even if not explicitly stated. For example:

1. The pressure of an ideal gas not only permits the construction of a temperature scale, it constructs the Kelvin scale.
2. Some state variables fail to construct a temperature scale, such as the volume of water near the freezing point where two different temperatures will have the same volume. It was recognition of such unsuitable state variables that convinced me that Serrin's ideas are important. Another unsuitable scale would involve phase changes, where different ratios of solid to liquid are associated with the same temperature. We might consider putting a brief mention of at least one "unsuitable" state variables into the reference footnote.

The more I think about this, the more I want to make the section very short and include about four sentences in a long comment to the reference footnote. --guyvan52 (talk) 04:14, 22 March 2014 (UTC)

You bring up several things. Perhaps it may be useful if I discuss some of them.

"When two bodies are brought into thermal contact, they exchange heat, which is defined as energy that is transferred between two objects of different temperatures." At present, after some struggles, Wikipedia defines heating as transfer of energy from a hotter body to a colder one, other than by work or transfer of matter. Much discussion has led to this definition. The important points that it embodies include: (1) exclusion of explicit mention of temperature from the definition; (2) exclusion of transfer of energy accompanying transfer of matter; (3) making explicit that work transfer is excluded.

Hotness is a term that bears some thinking about. It is very broad, in referring not just to thermodynamic systems which are special physical systems defined by thermodynamic variables, which are not defined for all physical systems. Hotness refers to any physical system. Two physical systems can be such that one tranfers energy as heat to the other, while neither has a temperature. The one that transfers the heat out is said to be the hotter. Worse, it is not a given of physics that if physical system A transfers energy as heat to physical system B, and physical system B transfers energy as heat to physical system C, then it would follow that physical system A would transfer energy as heat to physical system C. In other words, 'is hotter than' is not a transitive relation between physical systems in general. Physical systems in general, especially when not in their own states of internal thermodynamic equilibrium, can do all kinds of things. But thermodynamics is not about physical systems in general. It is about a special and narrow class of physical systems, those that have defined thermodynamic variables. In that narrow class, 'is hotter than' is transitive. Also we agree to say that if two thermodynamic systems X and Y are in thermal equilibrium then Y and X are also in thermal equilibrium, and X is in thermal equilibrium with X. Putting all this together, we have that thermal equilibrium is an equivalence relation. This is useful in thermometry but as you say does not define temperature.

The hotness manifold that Serrin and others refer to is not a temperature scale. They do not think usually of many manifolds, one for each respective temperature scale. Rather, the idea of the hotness manifold is that it is an abstract universal common temperature order, which is charted by all temperature scales in their respective different ways. It is called "the" hotness manifold of thermodynamics because it is universal, not the private domain of one temperature scale. The reason why the term manifold is used is that a manifold is by nature free of any special chart or coordinate system, but can be charted in indefinitely many different ways. Its one-dimensionality is its special feature. In this light one can distinguish between temperature in the abstract, which lives uncharted, with no specific scale, on the hotness manifold, and a particular temperature scale, which can be charted with a specific scale on the manifold. I think it fair to recall Ernst Mach in the context of the hotness manifold. Though he did not actually use that term, he put the more abstract idea of temperature on the map.

While it is true that the ideal gas thermometer has much to recommend it, it is not the definition of the Kelvin scale. It might be called a particular and ideal empirical temperature scale that happens by its ideality to coincide in values with the Kelvin scale. The Kelvin scale nowadays is defined through the Carnot engine. Of course the Kelvin scale also can provide a chart of the hotness manifold, a special chart of much importance. The Carnot engine is almost an embodiment of the second law of thermodynamics. I think that's a good reason for mentioning in the subsection on the zeroth law that the Kelvin scale is defined by the second law, not just leaving it to the subsection on the second law to say so. An empirical temperature scale depends on the properties of a particular material, while the absolute thermodynamic scale does not, beyond using the triple point of water as its above-zero reference value.

I don't know the exact Wikipedia rules, but I think footnotes are discouraged, and I don't like them. If something is worth saying, it is worth saying in the body of the article, not in a footnote.Chjoaygame (talk) 07:58, 22 March 2014 (UTC)

While it is a neat aphorism, I am not enamoured of it going in the article at this stage. It means that thermal equilibrium is a reflexive relation.Chjoaygame (talk) 08:03, 22 March 2014 (UTC)

I was not comfortable with the last sentence of the section, "To the extent that this gas is ideal, the Kelvin scale can be constructed.", and will remove it. Regarding the "neat aphorism", we don't need it because the first paragraph illustrates the idea by example. The only thing that now bothers me now are these two sentences:

"This statement does not, by itself, justify the idea of temperature as a numerical scale for a concept of hotness which exists on a one-dimensional manifold with a sense of greater hotness. Sometimes the zeroth law is stated to provide the latter justification."

Very few readers will have any clue as to what that means. But the passage does no harm, and there are enough examples so people like me will get a sense of what is going on. And the section is shorter. I am now happy with "Zeroth law". Are you?--guyvan52 (talk) 12:41, 22 March 2014 (UTC)

Thank you for your care in this. I am not happy with the first paragraph that reads "When two bodies are brought into thermal contact, they exchange heat, which is defined as energy that is transferred between two objects of different temperature. This exchange of energy will, in turn, cause state variables to change. Left isolated from other bodies, the two connected bodies eventually reach a state of thermal equilibrium in which no further changes to state variables occur. If one of the two bodies is a liquid mercury thermometer, the value of the state variable volume can be used to ascertain the temperature of both objects (which now have the same temperature)." My unhappiness is most with the words "heat, which is defined as energy that is transferred between two objects of different temperature" for reasons that I offered above.

There are several introductory ideas to be expressed here. Thermal equilibrium as an end stage of a transfer. End stage identified by cessation of change of state variable. Transfer of energy as heat.

It is debatable whether the idea of temperature should appear in the statement of the zeroth law. Some would say that it should, others that it shouldn't. To please those who say it shouldn't, I guess it might be better not to put temperature as an introductory idea. Better to leave it to appear when the less common statement is presented.

There are those who say that the primary message of the zeroth law is the existence of states of internal thermodynamic equilibrium. Then secondarily of relations of contact equilibrium, especially thermal contact equilibrium.

The sentence "But, by itself, it does not justify the idea of temperature as a numerical scale for a quantity that exists on a one-dimensional manifold with a sense of greater hotness" is perhaps too opaque.

I will have a try at dealing with these things.Chjoaygame (talk) 13:22, 22 March 2014 (UTC)

This section is now vastly improved and it is time to move on. I hope we meet again. I do have two final comments for you to think about:

• You wrote "it is specifically important that the manifold is restricted to thermodynamic systems". I challenge you to think of one case where a reader might erroneously apply the manifold to something other than a thermodynamic system? The only example I can think of is information entropy, and who knows, it might be a good idea to view information entropy from this perspective.

In response, the manifold does not describe a physical system that is far from its own internal state of thermodynamic equilibrium. That is the point of its one-dimensionality. The 'space' of all physical systems is infinite-dimensional, and most physical systems don't have a fully and uniquely defined temperature, so their states don't lie in the one-dimensional thermodynamic hotness manifold.Chjoaygame (talk) 01:48, 23 March 2014 (UTC)

• I think the last sentence should be deleted ("The Kelvin scale is defined on the basis of the second law of thermodynamics".) Such links between topics are necessary in scholarly articles, but Wikipedia has topic headings that will catch the reader's eye. The previous topic contains an image showing how plots of pressure versus temperature leads one to think about essential nature of the Kelvin scale. And less than one centimeter after the final sentence of the "Zeroth Law", is a glaring 'headline' that reads: Second Law of Thermodynamics. Furthermore, the final sentence is not 100% accurate: The Kelvin scale can be defined using the second law, but it can also be defined solely on the basis of the ideal gas law(plus the heat capacity of water). It all depends on how you choose to construct your understanding of thermodynamics.--guyvan52 (talk) 15:14, 22 March 2014 (UTC)

It's not how I construct it. It's how it is more or less agreed to construct it. In current literature, and in the Wikipedia, the more or less agreed definition of the Kelvin scale is through the Carnot engine, not through the ideal gas thermometer. I think that needs to be made clear in the section on the zeroth law, lest the reader of the zeroth law section be left confused, and wonder 'Which is it, the ideal gas or the Carnot engine that defines the Kelvin scale?'Chjoaygame (talk) 01:48, 23 March 2014 (UTC)

belong in this article

Yes, I think it does. To measure a temperature, one must wait for the establishment of a thermal equilibrium between target system and thermometric system. Wait a finite time. Therefore a temperature is always measured as a time average. I think these people do just that. Interesting to learn of Boltzmann's thinking.Chjoaygame (talk) 20:51, 11 April 2014 (UTC)

Just arrived at this article and...

Well, it's in need of some housekeeping; the early citations seem to be missing. The first sentence seems to be paraphrased from OED (Oxford English Dictionary). I can't help wondering if a more scientific definition might be better. I'm happy to have a go but I don't have much time available at the moment.--Grandchant (talk) 13:11, 13 April 2014 (UTC)

The lead is acceptable to me, but everything on WP has room for improvement, and it might be a good idea to rethink the lead now. I suggest we jot down a few sentences, or even phrases on this talk page.

I also found the use of "hot" and "cold" to define temperature a bit jarring.

Temperature is what earlier versions of the lead called a "common notion".. The scientific definitions are all post-Newtonian, both historically and in complexity. The only possible technical definitions would involve either the zeroth law, or heat flow. These are in fact nothing more than "common notions" scientifically stated. Introducing them to students in the lead would teach them the jargon of physics but not the physics itself. --guyvan52 (talk) 15:04, 13 April 2014 (UTC)

″The first sentence seems to be paraphrased from the OED.″ The OED is a bit more precise, at meaning 7.a., indicating a "sensible" quality. I don't feel a strong need to add that here.

″I also found the use of "hot" and "cold" to define temperature to be a bit jarring.″

Maybe. Maxwell and Planck are not too proud to use those ordinary language words in their introductions. I think they are right for here. I think they set the right context, a general one, to approach the idea of temperature. Often we are told that the Wikipedia is for ordinary persons. They know what hot and cold are. There is a significant literature justification for the simple wording, also in the work of Ernst Mach, by whom Einstein was influenced in his thoughts about general relativity.

We have had some extended talk on this page here about the level at which temperature should be conceived. The most abstract level is in the hotness manifold, perhaps first expressed by Mach. Not even numbers there, just comparisons of hotness. Next is the logical level of empirical temperature, used by Planck for example in his introductory approach; with numbers. Then we get to the ideal gas and to the Kelvin thermometers, which are more explicitly the final definitions. We had a push from one editor to admit the most abstract level, and I am inclined to agree.Chjoaygame (talk) 21:52, 13 April 2014 (UTC)

Absolute thermodynamic temperature

The official term is only "thermodynamic temperature". The headline may read better --- Thermodynamic temperature; absolute thermodynamic temperature --- to quote even older term. Then, the content should be modified, e.g. as shown.

Thermodynamic temperature; absolute thermodynamic temperature

Thermodynamic temperature with the thermodynamic scale is based upon Kelvin's idea to start the temperature scale at the lowest possible system energy (in classical physics - no molecular motion, in quantum physics - ground state of system). For this reason, this scale was also called absolute The Rankine scale using Fahrenheit degree and shifted for -491.67 is in this sense absolute, too.

Thermodynamic scale keeps the same step as Celsius one, namely 1 K (kelvin) is equal to 1 °C (degree Celsius) to keep the compatibility in every-day's life. To reach it, the triple point of water has been chosen and its temperature (0.01 °C) was set to 273.16 K. (Value 273.22 K would be slightly better for now the temperature of boiling water under 1 atm pressure is slightly less than 100 °C.) Celsius scale is now defined vice versa, using Kelvin scale. Because dependency on a particular matter is unwanted (even isotopic composition of water consisting of two isotopes H, D and three isotopes of O must be given), kelvin will be redefined by BIPM in nearest future, namely setting fixed value to the Boltzmann constant $k$ and connecting temperature unit to energy unit using relation $E=kT$.

Notes and references

Many thanks before for improving English of my text. JOb 17:09, 31 May 2014 (UTC)

undid edit of first sentence of lead

I undid the new edit of the first sentence of the lead. The edit was obviously in good faith, but I think it was not an improvement.

The now restored and previous first sentence is "A temperature is a numerical measure of hot and cold."

The candidate replacement was "Temperature is a measure of the difference in thermal energy between two material objects."

The restored sentence is the product of a more or less settled consensus, with a degree of dissent probably also present.

There are reasons for the restored sentence that make it preferable to the proposed candidate replacement.

1. The phrasing 'a temperature' is used because some editors point out that there are many definitions or measures of temperature, if one takes 'temperature' in its most general or abstract sense, in which it is uttered without a definite article. Differing from this is the proposed version, which is written as if the more abstract sense can be ignored, and treats the word as immediately having the more concrete definition proposed.
2. The phrasing 'numerical measure' is used because it seems important to emphasize that the measure is numerical, even if that word 'numerical' is considered logically redundant because some definitions of measure include that it is necessarily numerical.
3. The ordinary language words 'hot and cold' are used because there is a preference for ordinary language in Wikipedia. The very words 'hot' and 'cold' are used instead of perhaps 'hotness' and 'coldness' because the shorter words are acceptable and more ordinary than the longer ones with abstract suffices.
4. The sentence ends after those words because it is not necessary at that point in the article to say exactly what is being described as hot or cold. In particular, radiation has a temperature and is not a 'material object' as the words are used in ordinary language.
5. A temperature in general is not regarded as a difference, and an important kind of temperature is absolute relative to an absolute zero.
6. The most proper definition of temperature does not use the term 'thermal energy', which is of slightly vexed meaning and is not here proposed to be used a word of the ordinary language. The term thermal energy is often enough used with reliance on a molecular model of material bodies, while the most proper definition of temperature is the thermodynamic one, which advisedly avoids reliance on a molecular model. There are perhaps other definitions of thermal energy, but often the term is used vaguely so that its meaning reflects to some extent the viewpoint of its user.

For these reasons I think the proposed candidate would not be an improvement.Chjoaygame (talk) 02:30, 21 October 2014 (UTC)

I appreciate this well explained justification for the original lead sentence, and realize there has been much discussion on the lead of this article already, however I will offer a justification for the candidate lead sentence. The indefinite article "a temperature" is to be avoided I think, because it does not fit the style of other articles on physical phenomena (e.g. mass, Spin_(physics), etc.). "Numerical" is indeed redundant, when admitting all definitions of numerical (i.e. real numbers like sqrt(2)). Or, if we get really unconventional and admit qualitative 'measures' (like "cold", or "pretty") then "numerical" is simply incorrect. Indeed, here lies the most obvious problem with the original lead sentence. It mixes the redundantly science-specific notion of a "numerical measure" with the decidedly unscientific notions of "hot" and "cold". We can't have it both ways. Either "a temperature is a numerical measure" in which case an objective method for obtaining that measure must exist, or "a temperature [describes] hot and cold" in which case scientific approaches to temperature take a back seat. As to the temperature of radiation (i.e. far-field electromagnetic radiation), this is a rather artificial use of "temperature" and has its own article Color temperature. I would be very skeptical of the expertise of a scientist who used the word temperature to refer to the energy of a photon. Radiation can raise the temperature of a material object, or even coherent laser cooling may decrease the temperature of samples in specific conditions, however to say that the radiation itself has a temperature would be quite informal in my experience. Again, "color temperature", which is vaguely related to the emission spectrum of a black body at various temperatures, is treated in another article and that is for the best, in my opinion. Now, to say that Kelvin scale temperature is not regarded as a difference is incorrect. Namely, the difference is between the theoretical quantum ground-state of the material in question, and the observed thermal excitations present in the sample. This difference is expressed on a scale in which the unit is defined like Celsius, however now the triple point of water is used as the definition of 273.16K, to avoid consideration of pressure in the boiling and melting of water. Yes, the term "thermal energy" is not perfectly straightforward to define, but as you point out, neither is temperature. I would argue that "the most proper definition" of temperature is a difference in thermal energy between two objects, or in the case of Kelvin, between the total energy of a sample and a theoretical thermal ground state. In practice, we are always dealing with the differences in actual thermal energy, because it seems that matter cannot be entirely devoid of thermal energy. The term thermal energy does not rely on molecular models as you assert, and is actually probably most easily understood in terms of ionic crystal latices or metallic latices, in which there is highly repetitive atomic structure and electrostatic confinement of nuclei. Moreover, there have been (and are ongoing) attempts to extend the micro-scale ideas about thermal energy to quantum mechanical objects. Indeed, it is the direct relationship between entropy and thermodynamic temperature in crystals that has been forefront in scientific thinking about low-temp physics and quantum thermodynamics. Cheers. -92.24.92.92 (talk) 11:14, 23 October 2014 (UTC)

You offer various thoughts. As for conformity of styles of articles, I think the style should fit the subject matter. As for whether radiation has a temperature, you could try reading Planck's The Theory of Heat Radiation. Broadly speaking, I am not persuaded by your thoughts. I accept that a difference method is involved, and I will put that in. Perhaps I should have written 'microscopic particle models' instead of 'molecular models'. The accepted basic definition of temperature is in terms of macroscopic thermodynamics, as perhaps you already know. It would make things feel more comfortable if you were to think up a suitable user name and set it up and use it.Chjoaygame (talk) 13:02, 23 October 2014 (UTC)

"the kinetic fraction can be measured"

Pray, Editor Lovevo, how?Chjoaygame (talk) 11:06, 1 November 2014 (UTC)

Definition

Temperature is the property that determines whether or not one body will transfer heat to another body. One body can have more 'net heat' (ie: by having a higher specific heat) than another body yet if the other body is at a higher temperature that body will transfer heat to the colder body until their temperatures are equal. — Preceding unsigned comment added by 172.248.197.0 (talk) 23:11, 4 November 2014 (UTC)

Suggestion followed.Chjoaygame (talk) 05:38, 5 November 2014 (UTC)

undid good faith edit; why

I undid a good faith edit. The added material was of a general kind unsuitable for where it was placed. It was also discursive editorial commentary.Chjoaygame (talk) 20:54, 21 November 2014 (UTC)

water for triple point

It seems to me, @User:Spiel496, that the original post was appropriate in pointing to the Vienna mean. Yes, one should as a default go for the ordinary, in this case Water (molecule). But this is a very specialized question, in which the isotopic composition is very relevant. One has to read deeply into the Water (molecule) article to find this out. Considering the obvious speciality of the case, I think it would be best if Spiel496 undid his change of link from Vienna to ordinary water. I think the Vienna is the one for this table. I am not undoing it myself because I don't want to seem disputatious. Perhaps I am mistaken.Chjoaygame (talk) 01:34, 31 December 2014 (UTC)

My apologies, I changed it back. I had never heard of the Vienna thing, so I thought it must have been an accident with the wikilink. However, I should have researched it more carefully. "Vienna Standard Mean Ocean Water" refers to fresh (non-salty) water. I saw the word "ocean" and acted without thinking. Spiel496 (talk) 21:22, 3 January 2015 (UTC)

reason for undo

I here undid a good faith edit.

"Heat energy" would if anything refer to a transfer of energy between two systems. It would have the dimensions of an extensive variable. Temperature refers to a common intensive variable for two systems that are not transferring energy through a path that connects them.Chjoaygame (talk) 02:09, 19 January 2015 (UTC)

Why does "km" link to the page for Terametre?

In the "Examples of temperature" table, a wavelength of 6,400 km is stated. The "km" is linked to the Wikipedia page for Terametre. Is this an error in linking, an error in the "km" unit, or no error at all? Is there some obscure reason that Km should link to Tm? "Pij" (talk) 01:41, 5 September 2015 (UTC)

I think you have found a mistake, which I think I have fixed.Chjoaygame (talk) 02:26, 5 September 2015 (UTC)

reason for undo

Here I have undone this edit.

My reason is that the links inserted by the edit are unsuitable or superfluous. They seem to indicate a failure to recognize a distinction between a physical system and a thermodynamic system. The term 'physical system' refers very broadly to a wide range of physical objects, but in contrast, the term 'thermodynamic system' refers to a very narrow class of physical objects, those that are described by thermodynamic state variables. The link would confuse a reader who followed it without enlightening him. I think no link is needed there. Nothing can be made to reach a temperature of absolute zero.

There is, however, in my view, a fault in the form of the sentence that was edited: it has been in the past considered a fault of style to start a sentence with "However, ..." It has been considered right, instead, for example, to write "An actual physical system or object, however, ..." I don't know if this judgment survives, but I think it does.Chjoaygame (talk) 17:50, 25 October 2015 (UTC)

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"improve" the English by changing the physical meaning

I have undone an "improvement" in the English that made the physical meaning wrong. The absolute zero of thermodynamic temperature is the coldest possible temperature, but the lowest possible temperature either does not exist or is −∞ K. The latter is also the hottest possible temperature. 'Coldest' is the appropriate word, not 'lowest'.Chjoaygame (talk) 22:40, 10 April 2016 (UTC)

The lede is wrong: temperature is not energy

It says: "absolute temperature as proportional to the average kinetic energy". This is wrong. It is only valid for an ideal gas. Temperature is not the same as energy. Adding energy to ice will melt it into water, but it can still be at the same temperature as ice. /Pieter Kuiper (talk) 00:22, 31 December 2015 (UTC)

Editor Pieter Kuiper is right that temperature is not defined by "average kinetic energy". The lead, however, does not make the mistake of defining it so. The lead sentences to which Editor Peter Kuiper objects (quoting a few words extracted from one of them) read in full: "The kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic systems, especially of fluids. It indicates the absolute temperature as proportional to the average kinetic energy of the random microscopic motions of their constituent microscopic particles such as electrons, atoms, and molecules." The proper definition of temperature is not simple, and, for the sake of brevity, the lead does not attempt it. The kinetic theory defines temperature as indicated, in its own specifically convenient way, not in the way that it is properly defined in thermodynamics.Chjoaygame (talk) 01:33, 31 December 2015 (UTC)

Not true. The lede says that the temperature is _proportional_ to energy in unspecified "fluids". This could be water. But the statement is only true for ideal gases. And even then, this talk about the "constituent particles" is so wrong. The kinetic energy of electrons is not proportional to temperature. It is amazing how wrong Wikipedia can be in the lede of a basic science concept. And Chjoaygame does not care. /Pieter Kuiper (talk) 04:12, 31 December 2015 (UTC)

Pieter, I edited that paragraph - see what you think (and please feel free to change it). As for what you say about wikipedia, you're absolutely correct. The problem seems to come down to a small number of non-expert editors, and too few experts with the time or inclination to contribute. Waleswatcher (talk) 21:20, 1 January 2016 (UTC)

Thank you, Waleswatcher, that is a huge improvement. Basically correct. One issue is that some readers will misunderstand and forget the limitation to ideal gas, but the lede is not the place to try to address this. This rest of this article has more problems (poorly organized, too long), but it would require a tremendous effort to edit it into something. And then there are so many more of this kind of articles... /Pieter Kuiper (talk) 23:13, 1 January 2016 (UTC)

Editor Pieter Kuiper wrote above "And Chjoaygame does not care." This was a gratuitous personal aspersion, contrary to Wikipedia policy.Chjoaygame (talk) 04:35, 3 January 2016 (UTC)

Some of the above comments, including the header of this section, by Editor Pieter Kuiper are substantially inaccurate or misleading, or are misquotations, as exposed by my above comments.Chjoaygame (talk) 05:35, 3 January 2016 (UTC)

It bothers me that this edit was made without achieving greater consensus on the discussion page. The previous version VERY clearly indicated that the temperature/kinetic energy relationship, which is often derived from KMT, is fundamentally limited in scope. The new version does NOT make such a clear indication. Furthermore, the new version tends to over-generalize. The kinetic-energy-only relationship is really only true for monoatomic ideal gases, not all ideal gases. Polyatomic ideal gases will exhibit intramolecular potential energy that cannot be neglected. It took many discussion threads and entries to arrive at the previous version. I am very much in favor of reverting the recent change. If the problem was with the phrase "...especially of fluids", then I am in favor of removing that phrase only, since it doesn't necessarily add to the quality of the explanation. JCMPC (talk) 03:16, 2 January 2016 (UTC)

Experiments to test it have for some systems verified the proposition that electrons moving more or less 'freely' do indeed indicate the absolute temperature. The exact scope of kinetic theory is not quite clear, I think. In Wikipedia it is not well defined with adequate support. For sure, it is good for ideal gases, and mostly for real gases in suitable circumstances. There are kinetic theories of liquids. The concept of 'kinetic energy of a particle' is partly applicable in some areas of solid state physics.Chjoaygame (talk) 04:59, 2 January 2016 (UTC)

Personally, I don't have any qualms with kinetic molecular theory. I do have problems with what I view as the over-generalization and over-emphasis of the temperature/kinetic energy relationship. In my experience, this over-emphasis stems from when and how temperature is taught in typical undergraduate curricula. Introductory courses in thermodynamics try to paint a physical picture for temperature, and this is routinely done for the first (and likely only) time using a monoatomic ideal gas since the kinetic molecular theory description of this system is fairly straightforward. Introductory textbooks are very clear in providing this context, but many students at this level are all to eager to apply the new idea and tend to ignore the context in which the concept is initially presented. A review of the talk page archives for this article reveals that this issue has been as major point of contention in the past and, if I am allowed to interpret, the consensus was to include a statement that explicitly draws attention to the potential problems with the interpretation of temperature as kinetic energy. Such a statement was in the previous version of the article. JCMPC (talk) 14:07, 2 January 2016 (UTC)

Also, to follow up on other comments, why can't electrons be influenced by the temperature? While it is often standard to ignore "thermal" motion of electrons, this is just because the typical energy gap between electronic states is substantially larger than kT. In cases where low lying electronic excited states exist, thermal excitation of electrons should be commonplace. At the very least, isn't this why metals are such good heat conductors? The highly delocalized electrons in close lying states can transport energy over long distances at a rate that is fast when compared to the transfer of energy via vibrational motion "only" in insulators. JCMPC (talk) 14:26, 2 January 2016 (UTC)

I seem to recall that electrons emitted from a hot wire have been analyzed for velocity, and found to have a Maxwell distribution that tells the temperature of the wire. I don't right now recall the exact reference.Chjoaygame (talk) 17:49, 2 January 2016 (UTC)

Though I cannot comment on the distribution law followed, what you mention is the basis for thermionic emission, which is the basis for many electron guns, which is in turn the basis for cathode ray tubes. JCMPC (talk) 20:26, 2 January 2016 (UTC)

I have now supplied references in the body of the article for the Maxwell distribution of velocities of thermionically emitted electrons.Chjoaygame (talk) 04:17, 3 January 2016 (UTC)

As for dense fluids, the following may be of interest: E. G. D. Cohen, (1984), 'The kinetic theory of fluids—an introduction', Physics Today, 37(1): 64–73; doi: 10.1063/1.2916049: "velocity correlations are, of course, also created by collisions in fluids in thermal equilibrium. The created correlations are, however, again destroyed through collisions in such a way that the Maxwell velocity distribution function is maintained. This is not true in nonequilibrium fluids."Chjoaygame (talk) 22:08, 2 January 2016 (UTC)

Are there any further thoughts on the lead? Can we add back in the caveat on KMT that was present several versions ago? The phrase "temperature is proportional to the average kinetic energy of the random microscopic motions of the constituent microscopic particles" doesn't sit well with me. In particular, this implies to me a linear relationship between temperature and kinetic energy, which I find problematic. JCMPC (talk) 22:39, 3 January 2016 (UTC)

Editor JCMPC, you are right to want to do something about it. Careful wording is needed. Some editors are by nature opposed or allergic to careful wording. In thermodynamics (I mean equilibrium thermodynamics) temperature is defined in terms of a Carnot cycle, a strictly equilibrium concept. Kinetic theory wants temperature to be defined for non-equilibrium. Logically that is not possible. Therefore they just say "Oh, forget the logic. Let's just define temperature as simply proportional to the average kinetic energy of particles that are moving more or less freely." For many purposes, they have there a very good and valuable approximation. For rigorous theory, the necessary concepts are still at the cutting edge of research, mostly beyond Wikipedia, I think.Chjoaygame (talk) 04:49, 4 January 2016 (UTC)

This paragraph is still wrong, especially because it mentions electrons: "The kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. It indicates the absolute temperature as proportional to the average kinetic energy of the random microscopic motions of those of their constituent microscopic particles, such as electrons, atoms, and molecules, that move freely within the material."

The kinetic theory is pre-quantum. For electrons in metals, this would be the obsolete Drude model. In metals, the energy of electrons is typically several electronvolt, on the order of 100 times larger than what kinetic theory predicts for room temperature. Also light atoms (hydrogen in water, carbon in diamond) have kinetic energies larger than what classical theory predicted. And the classical equipartition theorem does not depend on particles moving freely within a material. /Pieter Kuiper (talk) 20:05, 4 July 2016 (UTC)

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Lead changes

Prior to making any changes in the lead of this article, please be sure to achieve consensus on the talk page first. Temperature is a very important, yet incredibly subtle, topic. As such, this is a very difficult article to get right. The article has a long (and contentious) history regarding consensus. Please respect the years of work on this page by many editors by seeking and achieving consensus before making any changes.

DePiep, my justification of "long time stable" for undoing your well-intentioned edits was to reflect the need for consensus on this page. It took a long time (and lots of discussion) to achieve consensus on the sentence you removed. As a standalone statement at the start of the article, it is clearly the most important statement in the article. It should only be replaced with the utmost caution. JCMPC (talk) 14:20, 3 August 2017 (UTC)

In that case, your es better be like "Old versio n has broad consensus" ;-) which would have triggered me into the right direction. That said, I do:n't think the older first sentence was good enough: "Temperature is an objective comparative measurement of hot or cold" [3]. Notes:

• hot is not even an article (it's a DAB), and the DAB too says: we have no article hot (temperature) for high temperature (I'm not missing it; we also don't have fast (speed) for high speed.).
• The "objective comparative measurement" looks good at first, but doesn't cover it. It's not comparative (compared to what? As a base! SI quantity, it is measured independently! by definition). Objective it is, that's the 'physical'. And a 'measurement' is touching it: temperature is the description of a measurement (or, of a definition).
• As with all physical quantitys, best is to start with the (SI base) definition:

Temperature = number × unit. (we use the word temperature usually, esp in sentences, but in science one can use formally & internationally the less-known quantity symbol T). We know the number & unit notion, but helpful is to keep recognising the algebraic formula. Either in language or in symbols. Temperature is the quantity being described (measured, defined, or discussed). number & unit is the value of that quantity we point to.

Once this algebraic definition of the quantity is grasped, we can go to verbose description (which I tried in the opening sentence). With all this, it would be better to write like:

"Temperature (symbol T) is a physical quantity describing the thermodynamic energy[?], expressed as a value on a temperature scale (°C, °F, or K)." -DePiep (talk) 14:48, 3 August 2017 (UTC)

Regardless of whether or not YOU didn't think the old version was good enough, you should still obtain consensus before making such a change. All of your points have already been covered in exhausting detail, and can be found in the archives of this talk page. They will help you to understand why the opening sentence was what it was. Temperature is not a topic to be taken lightly. It is a very subtle concept to grasp if not done properly, and is routinely misunderstood. It is a very difficult task to explain what temperature is from both an intuitive standpoint as well as from a more rigorous, scientific standpoint. The opening statement was intended to better reach the general public. The rest of the article goes into the more rigorous detail. JCMPC (talk) 17:19, 3 August 2017 (UTC)

you should still obtain consensus — or I can apply BRD. Your claim 'long time stable so BOLD even BRD edits are forbidden' is incorrect. And in short: the opening sentence is too childish and off to even hint it was well fleshed out. But I'll google the archives shortly.

Meanwhile, I hereby propose to keep the change I made & motivated here. -DePiep (talk) 17:30, 3 August 2017 (UTC)

• Restart I propose this: you JCMPC write the opening sentence as you think best. That could include some my improvements (not just reverting). After that, we'll be back here to discuss improvements. Gives time & arguing space. Deal? -DePiep (talk) 21:15, 3 August 2017 (UTC)

Please don't assume that I believe bold or BRD edits to be forbidden. That is not what I implied. My reversion of your edits is entirely in line with the notion of BRD, which is why I chose to address this issue on the Talk page rather than reverting a second time. That being said, why be bold and disrupt a long-standing consensus (even if a temporary one) when a discussion thread can be opened instead? Making a BRD edit should not come at the expense of respect for the work and established consensus of other editors.

If I were to rewrite the opening sentence as I currently think best, I would just revert once again. Ideally, if I could first establish consensus among active editors, I would prefer to go back to an opening sentence from almost a decade ago, "Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold." That being said, what was there last week wasn't so much different from this and so poorly worded that I would justify the time trying to change it, especially when a consensus had been reached among many other editors.

Regarding your proposed suggestion (14:48, 3 August 2017 (UTC)) for another new opening sentence, the idea that "Temperature is a physical quantity describing the thermodynamic energy..." is highly problematic and easily subject to error and/or misinterpretation, which is something that has been discussed at length on this talk page. Additionally, the idea that "temperature is... expressed as a value on a temperature scale" is essentially a tautology, which does not add value to the article. Furthermore, the topics of symbols and units are covered in detail throughout the article, and there is no need to include them in the opening sentence, which should be of use to a broad audience. I do not suggest sacrificing rigor, because there is plenty of that in the article, but the people who read this article the most will likely be non-experts, and it is imperative that their needs are kept in mind. The goal of tying the idea of temperature to the concepts of hot and cold, regardless of whether or not there are individual articles for "hot" or "cold," would be highly beneficial for the non-expert, which is something that has been already been discussed on the talk pages. JCMPC (talk) 04:59, 4 August 2017 (UTC)

As I said: please first create the opening sentence as you think it should be. That could include changes I edit/proposed. After that we can dive into the content issues here.

About the process: your reversal had the es: "Reverted well-intentioned edits back to an earlier version that has been stable for a long time." [4]. I repeat that "stable for a long time" is not a reason at all, so I reverted that one for good reason (I'm not supposed to understand that something else was implied). Only then did you start this talk (correct & laudable), in which real arguments came up (like the consensus you refer to). And some less usefull ("respect the years of work" [... so don't be bold] is not the way WP works). This sequence does not make me in error. -DePiep (talk) 10:14, 4 August 2017 (UTC)

"Stable for a long time" is a reason. It implies that a consensus exists. If this was not apparent, then I apologize for not using clearer phrasing, but edits summaries are limited in length and I chose my wording to be brief. To be frank, I find your sentiment that Wikipedia does not work on the basis of respect for other editors to be deplorable. It goes directly against one of the Five Pillars of Wikipedia, "Editors should treat each other with respect and civility." (WP:Five Pillars) At the risk of being less civil and diplomatic than I prefer, I shall have to be more bold. The new opening sentence isn't even complete. It is grammatically incorrect, making it impossible to determine its intended meaning. Editing the sentence to improve it would have been in vain, so I simply reverted. Incorporating the new feedback from the talk page into a revision would also be in vain because the rationale is incomplete and incoherent. It lacks structure and clarity. Beyond wanting to include something about units, symbols, and measurement theory (which is far too much detail for the opening sentence, as I have mentioned above) it makes no sense. I will repeat what I suggested in my previous comment: that we should either revert back to what it was or, if consensus among editors can be achieved, revert back to an opening sentence that was used years ago. There is nothing wrong with a bold edit. Many bold edits by many editors have made this article far better than it used to be, but bold is not the same as cavalier. JCMPC (talk) 12:36, 4 August 2017 (UTC)

Why didn't you revert or partially revert, as I proposed (twice)? -DePiep (talk) 16:48, 4 August 2017 (UTC)

You never proposed reverting.

"I propose this: you JCMPC write the opening sentence as you think best. That could include some my improvements (not just reverting)." (21:15, 3 August 2017 (UTC))

"As I said: please first create the opening sentence as you think it should be. That could include changes I edit/proposed. After that we can dive into the content issues here." (As I said: please first create the opening sentence as you think it should be. That could include changes I edit/proposed. After that we can dive into the content issues here.)

You requested that I write the opening as I see fit and specifically mentioned not reverting. I have now done this multiple times. Here is what I propose, yet again: "Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold." JCMPC (talk) 22:01, 4 August 2017 (UTC)

Yes I did, twice:

(1) [5]: I propose this: you JCMPC write the opening sentence as you think best.

(2) [6] please first create the opening sentence as you think it should be

Of course, even if you did not get my invitations: you could have (partially) revert. -DePiep (talk) 22:23, 4 August 2017 (UTC)

Editors JCMPC and DePiep have been discussing the first sentence of the lead. I will also comment.

There are two kinds of temperature scale, empirical and absolute thermodynamic. Empirical scales are of historical and practical importance. The absolute thermodynamic scale is well founded in thermodynamic theory, being based on a ratio of quantities of heat transferred. The quantities of heat are in turn based on quantities of work, which in turn is defined by mechanics, not thermodynamics. In practice, the absolute scale is most often expressed by virtually empirical procedures, such as platinum resistance.

The numerical value of an absolute thermodynamic temperature measurement is set by an arbitrarily chosen reference number for an arbitrarily chosen reference state of an arbitrarily chosen thermodynamic system, 273.16 K for the triple point of water. There is no theoretical reason why the Kelvin scale could not have settled on making the triple point of carbon dioxide the reference state of the reference system, and it could not have been given the value 1000 K. This is the reason why the word 'comparative' was included in the lead. Perhaps the word 'comparative' is not the best possible one for the purpose, but the purpose is worth its place in the sentence, I think.

The word 'objective' intends to make a contrast between the valid but imprecise and possibly subjective wording in terms of 'hot' and 'cold'. These terms have both subjective (how does it feel to me when I touch it?) and objective (which way does heat flow?) connotations; in ordinary language, the prime language of Wikipedia, the subjective connotation is part of the meaning. So the word 'objective' has a useful purpose, I think.

The grammar of the present first sentence is not comfortable. It is hardly obvious what is gained by saying that temperature is a 'physical quantity' in the first sentence. A naive reader may have little idea of the connotations of the phrase 'physical quantity'.Chjoaygame (talk) 09:13, 12 August 2017 (UTC)

Thanks, a nice reading.

In short, I think we should aim for an opening sentence that has both definitions: the scientific one and the subjective one. The two descriptions should be unconnected (don't try to describe one in terms of the other).

As for the science, one way or another we must state it is a physical quantity, i.e. a property of a body etc. Too often people jump into the measurement of it, but a temperature exists even when we do not measure it. Seconds pitfall is starting with the scale (as Chjoaygame does ;-) ) or unit. These are why describing the quantity becomes such a difficult task: the wrong end (many physical quantity article & uses suffer from this). So the setup should be like: "Temperature is a physical quantity (T) usually expressed in degrees on scale K, C, or F. It is also a subjective sense of being hot or cold." (it's about the elements to be in there, for now; not my English).

I disagree with the dumbing down argument, saying "ordinary language" cannot describe it (and no, that is not the prime language). -DePiep (talk) 10:04, 12 August 2017 (UTC)

WHil this talk is going on, Kbrose edited the lede into [7] without engaging here. First, this is bad practice, second, current text is not following from this talk. I ask Kbrose to revert and to join the talk. -DePiep (talk) 16:25, 12 August 2017 (UTC)

Several questions now arise, but I will consider just one for the moment.

Editor DePiep writes:

I disagree with the dumbing down argument, saying "ordinary language" cannot describe it (and no, that is not the prime language).

This sentence of Editor DePiep is hard to interpret. Who is doing the "saying"? Perhaps the sentence intends that Editor DePiep says that ordinary language cannot describe temperature. Then it seems that Editor DePiep asserts that ordinary language is not the primary language of Wikipedia.

Where is the "dumbing down argument"? It seems that Editor DePiep intends that use of ordinary language is dumbing down.Chjoaygame (talk) 08:11, 16 August 2017 (UTC)

Why do you address me in 3rd person? Why the 'Editor' style? -DePiep (talk) 18:25, 16 August 2017 (UTC)

This has turned out to be a long thread with several editors involved, so I assume that Chjoaygame is choosing a grammatical voice to clarify which parts of the thread are being referred to. That being said, I do agree with the concerns raised by Chjoaygame. Wikipedia is not a technical publication, and this should be reflected in the language of the articles. This does not preclude an article from using technical language, but it should certainly not be the focus of the lead (let alone the first sentence). The lead section (in particular the opening sentence, see WP:Redundancy) should be written for the non-specialist reader. This presumes that the average reader will have little-to-know technical knowledge of the subject. If technical language should not be used, then the only thing remaining is ordinary language. Furthermore, using ordinary language does not automatically make a statement incorrect or "dumbed down". Both ordinary and technical languages should be equally able to describe a topic. Technical language is advantageous because it is far more precise for a given word count, but it has the disadvantage that the non-specialist will lack the required vocabulary to interpret a given statement. Ordinary language is advantageous because it is accessible to the non-specialist, but it has the disadvantage that a larger word count is necessary for achieving the same precision as technical language. JCMPC (talk) 14:17, 21 August 2017 (UTC)

the first sentence of the new lead

The new lead starts:

Temperature is a physical quantity that expresses the subjective perceptions of hot and cold.

The article is primarily about physics. Though the terms 'hot' and 'cold' have subjective connotations, they also have solid foundations in physics, as may be checked in many reliable source physics textbooks. When two bodies are connected solely by a path that is strictly selective for heat transfer (a diathermanous path), energy will pass from the hotter to the colder. For this, it is not necessary that either body possess a temperature. Temperature does not primarily express the subjective perceptions of hot and cold. It therefore is regrettable that the rather tricky topic of subjective perceptions of hot and cold is given top priority in the first sentence of the lead.

The former version of the lead mentioned the comparative nature of temperature. This is rooted in the comparison between hot and cold. There is no uniquely suitable reference temperature, and so the numbers assigned to temperature measurements rest on comparison with an arbitrary reference temperature. In contrast, for example, the speed of light is in a sense a unique reference for speed. Besides the nonuniqueness of reference for temperature, there are empirical as well as thermodynamically absolute temperature measurements. This is the reason why earlier versions used the indefinite artic'e 'a' as the first word.

Though its appearance in the first sentence of the lead may be questioned, that temperature is a physical quantity expresses its contrast with psychophysical quantities. Likewise, that temperature is an objective measure contrasts it with subjective perceptions.

Perhaps the first sentence might read:

A temperature is a comparative physical measurement of hot and cold.

Perhaps.Chjoaygame (talk) 19:58, 25 August 2017 (UTC)

This discussion is useless. I won't go into this while Kbrose can revert into a nonsense version without engaging in this talk [8]. Why does not anyone revert Kbrose? (to be clear: hot is a DAB page. What more do you want to know about 1st sentence quality?). -DePiep (talk) 22:45, 25 August 2017 (UTC)

Sorry for the lengthy post. I wanted to address a number of questions I have all at once.

Chjoaygame, can you please elaborate on what you mean by empirical vs. thermodynamically absolute temperature measurements and the non-uniqueness of temperature? Don't the third and zeroth laws of thermodynamics, in combination with the expression of temperature as an entropy/energy derivative, uniquely fix the reference for absolute temperature just as the speed of light fixes the reference for speed? If this is the case, then wouldn't empirical temperature scales then be similar to measuring speed empirically with an arbitrary definition for a standard length and fixed unit of time? Empirical scales predated absolute, thermodynamic scales, but so did empirical measurements of speed.

Also, could you please elaborate on your comment, "For [energy transfer], it is not necessary that either body possess a temperature." If you are dealing solely with heat transfer, then mustn't the two bodies both possess a temperature, each of which is different?

Regarding psycho-physical quantities, isn't that where most physical measurements historically come from, the quantification of some perceived, subjective quality of an object? (Note that I don't mean to include things like charge or spin, which were properties that came long after the quantification other qualities and thus have an origin that is not psycho-physical.)

I would like to point out that, for me, I don't believe that the problem is about defining temperature. It is about defining temperature for the general public in a way that is the best compromise between accessibility and accuracy. For instance, the IUPAC Gold Book defines (thermodynamic) temperature as "[A] Base quantity in the system of quantities upon which SI is based," which is what I now believe DePiep may have been going for (please correct me if I am wrong). While this is certainly acceptable in a technical reference such as the Gold Book, I don't see how it is accessible to the average reader. I think the opening sentence (or two or three) should err on the side of accessibility since there is much space to achieve accuracy in the rest of the page.

What is wrong with the terms "physical property" and "physical quantity"? Don't all physical properties/quantities have to be measurable by definition, and don't all measurements have to be comparative by definition? If so, doesn't the phrase, "temperature is a physical property..." imply that temperature is measured comparatively?

How would people feel about using the phrase "...related to hot and cold" in lieu of "..of hot and cold"? Based on my above comments, I would then suggest "Temperature is a physical property related to the common notions of hot and cold." Would this fix some of the issue? For now, I will at least remove the link to the DAB page as per DePiep's comment. JCMPC (talk) 01:13, 29 August 2017 (UTC)

"can you please elaborate on what you mean by empirical vs. thermodynamically absolute temperature measurements and the non-uniqueness of temperature? Don't the third and zeroth laws of thermodynamics, in combination with the expression of temperature as an entropy/energy derivative, uniquely fix the reference for absolute temperature just as the speed of light fixes the reference for speed? If this is the case, then wouldn't empirical temperature scales then be similar to measuring speed empirically with an arbitrary definition for a standard length and fixed unit of time? Empirical scales predated absolute, thermodynamic scales, but so did empirical measurements of speed."

All of these comments are fair. The thermodynamic definition of temperature is not as an entropy/energy derivative, using the third law; it is in terms of heat engines and the triple point of water. Though some mathematical developments assume entropy as given, its measurement usually relies on temperature. One can do a lot of thermodynamics with empirical temperatures and empirical entropies, as some reliable sources emphasize. The indefinite article 'a' is a short word, and it leaves open the possibilities. It may cause some readers to think about the topic. Why not use it?

"could you please elaborate on your comment, "For [energy transfer], it is not necessary that either body possess a temperature." If you are dealing solely with heat transfer, then mustn't the two bodies both possess a temperature, each of which is different?"

This comment raises an important point of principle. The new first sentence of the article on heat dumbs it out. It is important for the logic of thermodynamics that the definition of heat not refer to nor implicitly rely on any notion of temperature. The thermodynamic definition of temperature then relies explicitly on that of heat. Circular thinking is thereby avoided. Strictly speaking, thermodynamic temperature is defined for a body in its own internal state of thermodynamic equilibrium. Heat transfer is admitted to occur between bodies that are not in their own internal states of thermodynamic equilibrium, and do not possess temperatures. Relative hotness is defined by the direction (sense) of heat transfer, logically prior to the notion of temperature.

"Regarding psycho-physical quantities, isn't that where most physical measurements historically come from, the quantification of some perceived, subjective quality of an object? (Note that I don't mean to include things like charge or spin, which were properties that came long after the quantification other qualities and thus have an origin that is not psycho-physical.)"

Since it is mentioned in these comments that there is a subjective quality of a body that reflects hotness and coldness, it is reasonable in these comments to distinguish psychophysical measurements from physical measurements. It is easy to do psychophysucal experiments that display big gaps between them for hotness and coldness. Such a distinction might reasonably be called metaphysical. But I don't think it necessary in the first sentence of the lead to burden the reader with such metaphysical considerations. I think one use of the word physical should be enough in one sentence to indicate that the article is primarily about physics.

"I would like to point out that, for me, I don't believe that the problem is about defining temperature. It is about defining temperature for the general public in a way that is the best compromise between accessibility and accuracy. For instance, the IUPAC Gold Book defines (thermodynamic) temperature as "[A] Base quantity in the system of quantities upon which SI is based," which is what I now believe DePiep may have been going for (please correct me if I am wrong). While this is certainly acceptable in a technical reference such as the Gold Book, I don't see how it is accessible to the average reader. I think the opening sentence (or two or three) should err on the side of accessibility since there is much space to achieve accuracy in the rest of the page."

I am not persuaded that there is a need to err on the side of accessibility. It is not evident to me that "related to the common notions of hot and cold" offers more accessibility than "of hot and cold". It think it is reasonable to tacitly assume that the latter phrase is related to common notions. What other notions of hot and cold would occur to the average reader, unless he is inclined to metaphysical reading?

Editor DePiep distinguishes between 'comparative measurement' and 'physical property'. He prefers the latter in the first sentence of the lead. I get the feeling that he doesn't like to emphasize the comparative aspect of temperature measurement and the measurement aspect of physical properties. I think "physical measurement" gives a better slant than "physical property".

"What is wrong with the terms "physical property" and "physical quantity"? Don't all physical properties/quantities have to be measurable by definition, and don't all measurements have to be comparative by definition? If so, doesn't the phrase, "temperature is a physical property..." imply that temperature is measured comparatively?"

Not all physical properties are directly measureable by definition. Some properties of light beams can be found only by very elaborate calculation, based on direct measurement. The phrase "comparative measurement" was insisted upon by an enthusiastic editor. I was taught that measurement can be either by effect or by comparison. I agree with that teaching. I am not sure whether the insistent editor had that distinction in mind, but I did not try too hard to oppose him. Temperatures are in a sense less obviously raw primary physical properties than for example lengths and masses. It might be proposed that the thermodynamic definition of temperature is by effect, to do with heat engines, as well as with the triple point of water, but in practice that definition is not common, and comparison is the usual way, for example platinum resistance. If it is really objectionable to put it in the first sentence of the lead, I would not insist on the word "comparative", but I think it has some merit. To a certain kind of trained mind, "the phrase, "temperature is a physical property..." impl[ies] that temperature is measured comparatively?" But the implication may not occur to the mind of the average reader. The term 'physical property' is rather abstract, while 'comparative measurement' has a more concrete slant, perhaps being more accessible to the average reader.

"How would people feel about using the phrase "...related to hot and cold" in lieu of "..of hot and cold"? Based on my above comments, I would then suggest "Temperature is a physical property related to the common notions of hot and cold." Would this fix some of the issue?"

I would prefer 'A temperature is a comparative physical measurement of hot and cold.' Next preference 'A temperature is a physical measurement of hot and cold.'Chjoaygame (talk) 07:11, 29 August 2017 (UTC)

Thanks Chjoaygame for clarifying your points. I only have few (hopefully small) comments in response.

When commenting on physical properties/quantities being measurable, I didn't mean to imply only direct measurements. Most physical properties, like those you mentioned, are only indirectly measurable. Many empirical measurements of temperature are indirect as they consist of measuring lengths or volumes.

I suppose I don't have the same objection to cyclical definitions as long as they are presumed to make up some axiomatic system, i.e. postulates. The cyclical definitions create relationships between abstract entities that are then used to build up some the system. But, I agree that such definitions should be avoided in the context of an encyclopedic entry. That approach would be best suited to a full treatment of a subject.

My suggestion to use "related to hot and cold" as opposed to "of hot and cold" was not to make it more accessible, but to address some of your concerns by slightly softening the connection between temperature and the notions of hot and cold as psychophysical sensations. Not sure if that makes sense.

I am certainly not opposed to explicit mention of things like "measurement" or "comparative" as long as things don't get overly verbose. I think both of your suggested opening sentences are fine. Of the two, I prefer the first. Also, I do like including the article, "a", at the beginning. To me, it helps to create a subtle distinction between this article and the article on thermodynamic temperature. JCMPC (talk) 16:09, 29 August 2017 (UTC)

Thank you for these comments. Concern to avoid circular definitions has been a staple of the talk pages on heat and temperature. My impression is that undefined primitive terms may use circular thinking, to express relations amongst presupposed ideas. Such circularity is informal and perhaps even necessary. It intends merely to suggest basic intuitions that are hardly expressed precisely in words. It is not logical development. Starting from that informal basis, formal definitions and axiomatic development should avoid circularity. As for thoughts of psychophysics, my feeling is that they don't need expression in the first sentence of the lead. Hot and cold have directly physical meaning, found in reliable sources of thermodynamics, as well as psychophysical meaning.Chjoaygame (talk) 02:13, 30 August 2017 (UTC)

I see that Chjoaygame is pestering the talk pages of physics articles again. Be aware that this editor may be your worst Wikipedia nightmare. Don't feed Chjoaygame. Chjoaygame is issued a topic ban in quantum physics. It is mostly an accident that Chjoaygame is not so far issued a topic ban in thermodynamics as well. YohanN7 (talk) 13:24, 5 September 2017 (UTC)