Talk:Heat/Archive 6

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heat especially in thermodynamics

I have put into the lead the modifying phrase 'especially in', to say "especially in thermodynamics". The definition of heat used here is the carefully developed fruit of experiments interpreted in terms of thermodynamics. The modifying phrase makes it clearer and more explicit in the lead of the article that the definition of heat here used is a special definition. This should help to allay concerns that have been expressed on this talk page, that may perhaps to some degree be reasonable, that the present definition has in some sense arrogated the word heat without proper justification or notice.Chjoaygame (talk) 09:06, 2 April 2012 (UTC)

'Arrogated the the word'? Surely it is mostly the other way round. Of course animals have been 'in heat' for centuries, how long the elimination rounds for athletic events have been called 'heats' I neither know nor care. My question from the POV of Wikipedia what is wrong with a normal disambiguation section? Does anybody know of synonyms that can't be handled this way? I can't think of any at the moment. A lot of trouble on this matter is currently the poor knowledge of physics possessed by some of the would-be editors. --Damorbel (talk) 11:59, 2 April 2012 (UTC)

The term "thermal energy" needs reliable sourcing

The term "thermal energy" is not a standard term strictly defined by standard texts that I am familiar with. I think some homework needs to be done on this term so that this term should be well sourced from reliable sources, or that it should be made explicitly clear in the article that it is not to be found in reliable sources, or that the term should be removed from the article. Chjoaygame (talk) 03:48, 24 March 2012 (UTC)

• I suggest J C Maxwell 'The Theory of Heat', p9 l3 - 8 "When we require an adjective to denote that a phenomena is related to heat we shall call it a thermal phenomenon, as for instance, we shall speak of the thermal conductivity of a substance or of thermal radiation to distinguish the conduction and radiation of heat from the conduction of electricity or the radiation of light." --Damorbel (talk) 13:36, 5 April 2012 (UTC)

Thank you for this suggestion. The term that needs reliable sourcing is "thermal energy", not just 'thermal', which is an ordinary language word as well as having the imprimatur of Maxwell. To use that quote from Maxwell for the present purpose would be synthesis at best.Chjoaygame (talk) 14:14, 5 April 2012 (UTC)

What Maxwell wrote was "When we require an adjective..." You might possibly have a reasonable objection if there was another meaning for thermal but even 'thermal underwear' is generally understood as something to do with heat. Do you need a reliable source for this adjectival use of the word? Can there be any real misunderstanding of the meaning? If not then you have no valid objection. --Damorbel (talk) 15:33, 5 April 2012 (UTC)

Dear Damorbel, as I wrote above, the question is not about the separate word 'thermal'; it is about the combined term "thermal energy". You are not addressing this question.Chjoaygame (talk) 19:54, 5 April 2012 (UTC)

"it is about the combined term "thermal energy"." That is correct; when you use an adjective together with a noun the adjective describes the noun to further refine its meaning, just as Maxwell says. So 'thermal energy' is the (kinetic) energy (Joules) of the microscopic motions of the particles making up the thermal system. No problem there, it is just the required definition. --Damorbel (talk) 20:36, 5 April 2012 (UTC)

What you are recommending is called WP:SYNTHESIS and is not permitted by Wikipedia policy. The question here is about the combination as a special term "thermal energy". If the words are to be taken as separate words of ordinary language, then no special term is involved and nothing should be said about it; the Wikipedia is not a syntactic engine for ordinary language.Chjoaygame (talk) 21:08, 5 April 2012 (UTC)

• If you use Google scholar to search "thermal energy" as a term you get 2 million hits in the science and patent literature. A lot of the hits on the first page are for thermal energy storage in solids, as for solar heat dumps (storage) for home and building heating. [1] It is used properly as a synoym for "static energy derived from heat." These areticles use the word "heat" also, but always in the context of heat flow. And yes, I certainly admit that in the sciences you can find "heat content" used as a synonym for "thermal energy content." But we address the definition problem in the lede. There are plenty of examples of this article's use in the science literature. SBHarris 17:54, 5 April 2012 (UTC)

The question is about reliable sources. The Wikipedia is not a competitor with Google. If someone wants to know if the term can be found by Google, he can Google it. The Wikipedia is oriented differently from Google. The question is not whether the term can be found in the literature. It is whether reliable sources can be found for it.Chjoaygame (talk) 19:54, 5 April 2012 (UTC)

The published peer-reviewed scientific "literature" (what shows up on Google Scholar) has already been decided to be ex vi termini reliable for WP's science purposes. Even science textbooks at the college level qualify, by prior decission. Don't bother me with the philosophical implications of what is really-really-truly philosophically episemologically reliable and how to tell, in science. All that belongs on the WP:RS TALK page, where it's been discussed to death by people who know very little about such issues, and the "community" (ie, the editors with clout) have already made their decission. Welcome to Wikipedia. If you want to argue otherwise, go there to do it. SBHarris 20:54, 5 April 2012 (UTC)

If that leads you to a reliable source, then please show it. If not, I can reasonably conclude that it doesn't lead you to a reliable source. Wikipedia policy requires reliable sources.Chjoaygame (talk) 21:16, 5 April 2012 (UTC)

I did show it, in the link just above. [2] If you're incapable of clicking a link, it's not my problem. By the way, you might actually look at the references in thermal energy. Both engineering sources define heat and thermal energy in exactly the same way. I have Incropora and DeWitt, who say that heat and heat transfer are the same thing ("energy in transit due to a temperature difference"). Both define thermal energy as the part of internal energy that is responsible for temperature. That definition means that thermal energy does not include latent energy (sometimes loosely called latent heat). But modern texts are quite careful to use the word heat only when they mean heat flow or heat transfer. SBHarris 22:03, 5 April 2012 (UTC)

On page 16 the version of Incropera and others which I accessed on the internet writes: "the sensible and latent components of the internal energy (U_sens and U_lat respectively), which are together referred to as thermal energy." Perhaps we are looking at different versions of the text. Either way, the text I am seeing here explicitly uses heat to refer to components of the internal energy, not to components of heat transferred.Chjoaygame (talk) 03:27, 6 April 2012 (UTC)

SBHarris writes above: "[Thermal energy] is used properly as a synoym for "static energy derived from heat." The term "static energy" is not one that I am immediately familiar with in the present context. At a glance it seems that it might refer to a component of internal energy.

SBHarris writes above: "I have Incropora and DeWitt, who say that heat and heat transfer are the same thing ("energy in transit due to a temperature difference"). Both define thermal energy as the part of internal energy that is responsible for temperature." On pages 15 and 16 of the Incropera text that I can now read, there is discussion of "thermal energy generation". It seems that the reader should remember that such thermal energy generation is not heat generation as distinct from heat transfer? It seems that "thermal energy" here refers to a well defined component of internal energy, contrary to the import of the first law of thermodynamics. It seems that this source, in its own internal thinking, has not thoroughly abandoned the caloric theory of heat.Chjoaygame (talk) 03:57, 6 April 2012 (UTC)

SBHarris writes above: "Don't bother me with the philosophical implications of what is really-really-truly philosophically episemologically reliable and how to tell, in science." In response I say that I am not looking at those philosophical implications. I am looking to uphold Wikipedia policy for better reliability of the articles, by good selection of reliable sources.

SBHarris writes above: "The published peer-reviewed scientific "literature" (what shows up on Google Scholar) has already been decided to be ex vi termini reliable for WP's science purposes. Even science textbooks at the college level qualify, by prior decission."

From the article on reliable sourcing, we have:

Scholarship

• Articles should rely on secondary sources whenever possible. For example, a review article, monograph, or textbook is better than a primary research paper. When relying on primary sources, extreme caution is advised: Wikipedians should never interpret the content of primary sources for themselves. See Wikipedia:No original research.
• Material such as an article, book, monograph, or research paper that has been vetted by the scholarly community is regarded as reliable. If the material has been published in reputable peer-reviewed sources or by well-regarded academic presses, generally it has been at least preliminarily vetted by one or more other scholars.

Here it seems that SBHarris is asking us to accept the lowest permitted standard of reliability.

Even when one allows a peer-reviewed paper found by Google Scholar, according to the first dot point above, extreme caution is advised. Here it seems that SBHarris is asking us to by-pass this policy advice, so as to open the way for a lesser standard of reliability. Of course, SBHarris is far from being the only editor who wants to lower Wikipedia standards in ways like this.Chjoaygame (talk) 05:12, 6 April 2012 (UTC)

Again, if you're going to challenge the above-quoted WP:IRS policy in some way, you need to go to WT:IRS (the IRS talk page) and make your case there, not here. Go and complain that somebody is trying to use the "minimal standards" and you'd like it deleted. However, since I quoted to you from a Google Scholar paper, we've provided you with both primary scientific paper uses of "thermal energy" as well as two textbook uses of the term of art in engineering (as noted in the lede) so it's not at all clear what you're going to complain of, there. Texts are said in WP:IRS to be preferred over research papers, even though papers (as the one I quoted from an academic press) have been peer-reviewed, and sometimes textbooks are not.

Again, you should not think from this that I agree with WP's "rules" in this, as they can result in bad articles on WP (I ran into that problem in fighting bad physics textbook definitions of weight-- which is an article that still includes stupid definitions that allow weightless astronauts in orbit to have 90% of ground weight, as GR's cancelling effect on the major component of g in certain inertial frames is ignored, since some beginning college texts ignore it). The secondary sources (as in this case) may be sloppily-written textbooks for freshmen written by authors who aren't Ph.D. scientists (or else are not writing in their own field of expertise) and they disagree with each other, or make mistakes. So it's not always true that the preferred secondary sources are always better than primary sources. Sometimes primary sources are all that exist. In other cases, texts have worse standards. Again, however, here is not the place to argue that. I've been there, done that. If you want to take up this banner, you go, girl. I'll stand aside and cheer for you. SBHarris 17:49, 6 April 2012 (UTC)

comments on undone revision of new version

I accept that the wording that I wrote is very terse. The undone edit adds many words, which I do not see as improving the terser wording.Chjoaygame (talk) 13:45, 15 April 2012 (UTC)Chjoaygame

• Chj, no one is criticising terseness. It is not terseness that renders your text confusing and an embarrassment to read. Let's see a few examples.JonRichfield (talk) 16:32, 15 April 2012

First paragraph:

In physics, chemistry, engineering, and particularly in their thermodynamic aspects, the word heat refers to energy in a process of transfer or transformation such as to cause changes in the temperature, and thereby the associated attributes such as volume and pressure, of affected objects.

I find this edit introduces uninformative verbiage, and to be inaccurate. Heat processes do not have to cause change in temperature; transfer of heat is driven by difference in temperature, not the other way round. Telling us here that temperature changes are associated with other changes is simply chatty. Telling us that thermodynamics is an aspect of physics is uninformative; it is enough to say that it is in physics.Chjoaygame (talk) 13:45, 15 April 2012 (UTC)Chjoaygame

• Your assessment of chattiness is suitably crushing no doubt, but it makes your own version none the more comprehensible, nor your assessment of the accuracy of this text any the more penetrating. I am sorry that you found it uninformative, but maybe you could try harder. It was largely a paraphrase of your own text, and if you think that the association of changes with the transfer of heat is irrelevant (as implied by adjectives such as "chatty" seemed to imply) then you leave me in doubt as to your competence in something. I hope it is English rather than physics! Please don't bother to explain why you think that it means the same thing to call something an aspect as to say that it is "in", though I admit to an idle curiosity as to why you thought that you had conveyed half as much on the point you mention. I am sorry that you failed to understand that what I had said never claimed, thought, nor implied that heat drove temperature changes, but since you did not ask for elucidation, I have enough to keep me busy elsewhere.JonRichfield (talk) 16:32, 15 April 2012

Second paragraph:

Heat refers to macroscopic, or nearly macroscopic, behaviour, as opposed to elementary particles or the motion of isolated rigid molecules or atoms. The modes of the microscopic motions of particles such as the molecules that constitute physical materials, adequately explain the macroscopic behaviour of heat and heated objects or media.

Again I find this introduces unnecessary verbiage. Heat does not refer to nearly macroscopic behaviour, whatever that might be. The microscopic motions themselves are explanatory, and do not need to be wrapped up as 'modes'. The explanations are good, not merely adequate. 'Bodies' is near enough, and traditional, and does not need to be, indeed is better not, expanded into 'objects or media'.Chjoaygame (talk) 13:45, 15 April 2012 (UTC)Chjoaygame

• Here you seriously embarrass me. I would have thought that you would understand what "macroscopic" meant without my explaining anything so elementary. Macroscopic means something specific, namely that which can be seen (if only just) by the unaided eye. Let us say, down to 10 micrometres or so under favourable conditions. Bulk thermodynamic effects reign down to nanometre scales at least. I could have phrased it differently of course, saying something like "macroscopic, microscopic and submicroscopic, but not isolated particulate scales", though personally I would have preferred "bulk matter scales", but you seemed so proud of "macroscopic" that I didn't like to embarrass you. I trust that in future you will be in less puzzlement about what whatever "nearly macroscopic" might be in a reasonable context. Do feel welcome to ask.JonRichfield (talk) 16:32, 15 April 2012

Next paragraph:

In ordinary usage, as distinct from technical language, the word heat has a variety of meanings. This often leads to confusion when practitioners in fields dealing with the physical sciences experience difficulty in conveying technical points to parties unfamiliar with the correct technical definition and its implications.

Conversely, the word heat is used in various ways in various contexts in thermodynamics. These usages vary in their degree of formality. Understandably, the closer a study is to practical application of of theory (for example, in engineering) the further it is likely to stray from the austerely rigid usages of the thermodynamic physicist. Both classes of terminology however, reflect the theoretic conclusions arising from some three and a half centuries of experiment and research. Thus heat refers not to states of bodies, but rather to processes within or between bodies: "we cannot defend on any basis the statement that a system in a definite state contains a definite amount of work or a definite amount of heat."

Again I find this introduces unnecessary verbiage. There is real diversity of meaning, not merely variation. The word 'conversely' has a technical meaning which is irrelevant here and is here not actually meant. Really we do not need to know that practitioners are are talking to parties. I think it is distracting to read that the research has taken three and a half centuries. It is getting to be simply chatty.Chjoaygame (talk) 13:45, 15 April 2012 (UTC)Chjoaygame

• Really Chj, your ideas of "terse" and "chatty" would seem far more impressively austere if you used them more appropriately. As things stand you increase my embarrassment. Terseness is no virtue if it fails to convey necessary material to a selected audience with appropriate efficiency and comprehensiveness. Using few words only is a virtue when they convey the required sense and mood. The fact that you failed to find verbiage necessary may of course be because of your susceptibility to easy distraction. What on earth induced you, with your aversion to chitchat, to speak of the likes of "These usages are the carefully constructed fruit of a large and well confirmed body of experiment."? Must try harder. Thank you of course, for your helpfully intended explanation that "conversely" has a meaning. For your next exercise you might wish to see why it was used here. Don't bother to explain it to me though. I already know, so your effort would be excessively chatty.JonRichfield (talk) 16:32, 15 April 2012

Again, I accept that the wording that I wrote is very terse. It is so for carefully thought out reasons. The new revisions are mainly in a summary and an overview, not in a detailed section of the article. Some grammatical filler words that might at first sight seem called for would potentially mislead if they were put in, and are better left out.Chjoaygame (talk) 13:45, 15 April 2012 (UTC)Chjoaygame (talk) 14:45, 15 April 2012 (UTC)

• Chj, terseness is no sin as such; rest easy. Chattiness isn't either; not as such. The sin is in not matching register and clarity to one's audience and semantics to one's mastery of language. Bear those in mind and I'll leave you to it. Got some chatting to do. Let's see how terse you can be; don't let me stint you on that preference. Cheers, JonRichfield (talk) 16:32, 15 April 2012 (UTC)

Thank you for your detailed comments. I agree that my wording is very terse, perhaps too terse. You find it even nonsensical, clumsy, and ridiculous at times. Grammatical fillers carry risks of being misleading. I would like to soften the wording only as necessary and gradually; I will look it over. More pressing, as you can see, is that there are some editors with a determined point of view that may call for consideration.Chjoaygame (talk) 17:10, 15 April 2012 (UTC)

There. I have removed the offensive metaphor of fruit as too colourful or perhaps bizarre, and the long word macroscopic, which I agree is jargonistic. I have recast some sentences, I hope for the better.Chjoaygame (talk) 17:26, 15 April 2012 (UTC)

And there again! It seems that all my effort, sinful merely in being incomprehensible though it may be, was in vain because it was blasphemous!Chjoaygame (talk) 07:51, 16 April 2012 (UTC)

response to reversion to old version

I well understand Count Iblis' reason for his reversion to the old version, and I accept that a case can be argued for it. Indeed it is true that there exists a rigorous definition of a quantity of energy transferred other than by work, that does not refer to temperature, but that does not make it a definition of heat; it does not relate to heat until it relates to temperature. Carathéodory's 1909 paper, relied upon by Born 1921, and the source of the divergence of definitions, does not actually define heat in its own terms, although it defines temperature. Carathéodory's statement of the first law of thermodynamics does not admit the notion of heat. It is customary, though perhaps mistaken, to say that the zeroth law of thermodynamics helps in the definition of temperature. This suggests that the idea of temperature is considered preliminary to the statement of the first law of thermodynamics. This weakens the case that temperature is really not involved in the first law of thermodynamics. Close examination of Carathéodory's statements about his first axiom leave it in doubt whether he has really made a statement about a conservation law, or merely, as is explicit in his own words, made a statement of the existence of a function of state that he chooses arbitrarily to consider and call "internal energy".

Because of the diversity of meanings and points of view in physics for the word heat, it is inappropriate to insist on just one very exclusive definition in the lead; detailed definition should in this case be considered in sections of the body of the article. The definitions of heat that explicitly refer to temperature are also rigorously valid, as considered for example by Maxwell, Planck, and Kirkwood & Oppenheim. It is a matter of taste to prefer the very exclusive definition that Count Iblis and certain other editors consider best, but there are several other editors whose tastes do not concur with it. The new version of the article admits the Bryan-Carathéodory-Born definition of heat, but does not try to deal with the detail of the diversity of definitions in the lead.

The new lead does not pretend to define heat in detail, but defers detailed definition to the body of the article, and instead makes a true statement about heat that is more or less expected by several editors. Heat is indeed related to temperature, if not by definition then by deduction. It is a valid point of view that it must be defined without reference to temperature, but not the only valid point of view.

I think that insistence on the exclusively rigorous definition of heat, that does not mention temperature, being stated in the lead is an arbitrary exercise of personal taste, and tends to push a particular point of view to the exclusion of others.

Therefore I have undone the reversion by Count Iblis.Chjoaygame (talk) 16:35, 15 April 2012 (UTC)Chjoaygame (talk) 16:44, 15 April 2012 (UTC)

It is not true that definitions based on temperature are rigorously valid, because temperature cannot be defined in the general case (only when the system is in thermal equilibrium). This is not some esotheric point, in astrophysics one frequently encounters phenomena where local thermal equilibrium is not valid and you have to work with the velocity distribution of the particles (e.g. using Boltzmann equation or Vlasov equation).

The definition based on work is more general, what is written currently is a special case of the general definition. So, in reality, there is nothing exclusive about this, although one can argue that this issue has to be explained better in the article. Count Iblis (talk) 17:10, 15 April 2012 (UTC)

I am not saying that it is an esoteric point; I am just saying that it is not the only valid point of view. Carathéodory and Buchdahl both talk at length about quasi-static processes and they are essential to Carathéodory's arguments. They admit temperature in near-equilibrium processes. When local thermodynamic equilibrium does not prevail, it is difficult to define work, and when it is difficult to define work, it is difficult to define heat. You say that when local thermodynamic equilibrium does not prevail you have to work with the velocity distribution of the particles; that is not defining heat in terms of work, and indeed may not be defining heat at all. Perhaps the article should make it clear that there are situations where heat cannot be conveniently defined, but mostly they are so because temperature also cannot be conveniently defined.Chjoaygame (talk) 17:39, 15 April 2012 (UTC)

Done.Chjoaygame (talk) 19:36, 15 April 2012 (UTC)

Sorry, but this doesn't make much sense. Work is always well defined (being the change in internal energy due to the change in external parameters), heat transfer is thus also always well defined. Another thing is that what the article says should be consistent with how modern textbooks teach the subject. Old references to Planck and others are only appropriate if these are also cited by modern textbooks. Count Iblis (talk) 00:05, 16 April 2012 (UTC)

Dear Count Iblis, you are taking a very hard line, I think too hard. Moreover, you are being non-consultative. If you don't like the single sentence that I added to accomodate your concern, you might reasonably revert it, but to revert the whole new effort for that reason is I think excessive. I don't want to try to enter into an edit war with you, because you have already shown that you are very determined, even to a point that looks like violence to me, so I am not reverting your undoing again, but I do think you are using violence rather than reason here. The revision that I have tried to make is, I think largely though not in every detail, supported by several editors. My revision explicitly includes your point of view; but it allows that it is a point of view. My revision opens the way for balanced reasonable criticism of talk, that appears in some meteorology (Atrens, C.D., ninth edition, 2007) and even thermodynamics (Bailyn, M. 1994) texts, of the rigorously thermodynamically wicked locution "adiabatic heating". My revision was made in response to such complaints as "Right now, it's stinking up the lede." While I do not think that complaint is compelling and I don't like the spelling 'lede', neither do I think it is to be entirely ignored, while you do seem to insist that it should be entirely ignored. You, and I expect some other editors, are very deeply supportive, indeed insistent on the exclusive validity, of the Carathéodory line. But it is not the only valid way of thinking, and therefore I say it is one of several reasonable points of view.

You obviously have an admirable knowledge and understanding of this subject in detail; but that is not the same thing as having a uniquely and exclusively valid point of view or general perspective, as you seem to think yours is. I think you rely very much on statistical mechanical arguments to the detriment of the macroscopic point of view. To some extent, your rigid insistence that yours is the only valid point of view does indeed spoil or even poison the field for editors with a different valid point of view. The editing goes round and round in futile circles trying to say things in simple and reasonable terms, but being strangled at every step by the arbitrary and to some extent violent stipulations of you and a few other editors. You spoil it for others, but mostly don't bother to deal in the article with the things they are trying to deal with. Your contribution is therefore in a sense mostly as a spoiler.

It is far from clear from what you say here in your "discussion" how you would distinguish between internal energy and heat in many astrophysical situations. For example, the definition of heat transfer, by Balescu, R. (1997), Statistical Dynamics: Matter out of Equiligrium, Imperial College Press, ISBN 1860940463, conflates transfer of internal energy with transfer of heat. In other words, he doesn't really define heat transfer at all. Other writers who conflate heat transfer with internal energy transfer are listed at http://vixra.org/pdf/1111.0024v2.pdf; the list includes De Groot & Mazur 1962 and Jou, Casas-Vásquez & Lebon 2010. Carathéodory 1909 himself does not actually define heat transfer in his own terms, but he does rely on the existence of temperature.

Your note on your reversion says "Revert per discussion." Your comments above are indignant expostulations, but whether they constitute discussion I would not be so sure. You do not here explicitly state your argument or give sources for it, but rely on some pejorative rhetorical epithets.

As for citing Planck, many modern texts do it, and I follow them on occasions when Planck happens to be correct as I see it. I am inclined to do it to signal to students that their present texts are not written by gods.

Above, you define the "external parameters" as the x_i, and note that the work is not necessarily given by the X dx term. The X quantity is not necessarily definable far from thermodynamic equilibrium. You say that "There is no other way to define heat in general." It is not a given that in general a definition of heat exists; it is an arbitrary stipulation by you and some with your point of view. There are plenty who would say that they are happy not to be able to define heat in general, and you are just violently ruling them out. It is one thing to write the Gibbs-Duhem equation, another to define heat in general, especially for the cases when the temperature is not defined because of a large distance from thermodynamic equilibrium. Thermodynamics has limited scope, which you seem intent on denying.

So as it stands, unless there is some other editor who wants to take up the cudgels, it seems to me that your point of view now prevails exclusively through violence not discussion.Chjoaygame (talk) 07:37, 16 April 2012 (UTC)

If you can't define heat in general (i.e. during non-equilibrium conditions), then you have a huge problem, because we all know that heat flows during non-equilibrium conditions. Of course, thermodynamics does have a limited scope, but no one is denying that. In fact, this precisely motivates defining heat like the way it is done in the quoted textbooks. Count Iblis (talk) 15:32, 16 April 2012 (UTC)

We seem to agree that "thermodynamics does have a limited scope". We presumably agree that a person who couldn't define heat in general would have a problem with the idea that heat flows during ALL non-equilibrium conditions. I think we disagree however on this: I would say that it does not make sense to say that heat flow during all non-equilibrium conditions accounts for all non-work heat flows. I would say that heat flow does not account for things when it makes no sense to speak of temperature. I am saying that some disorganized or chaotic (or somesuch) energy flow other than work flow under some conditions is not reasonably described as heat flow because no temperature is defined for it. One needs some other term than heat to describe such flows. They are outside the realm of thermodynamics and therefore it makes no sense to insist on a thermodynamic definition of heat for them. Perhaps you could outline what you mean by "thermodynamics does have a limited scope".Chjoaygame (talk) 17:58, 16 April 2012 (UTC)

Count Iblis writes: "Of course, thermodynamics does have a limited scope, but no one is denying that. In fact, this precisely motivates defining heat like the way it is done in the quoted textbooks." This is an admission that the 'heat' defined in the insisted upon Born 1921 definition that is used by the quoted textbooks is motivated by the fact that it intends to refer to something that is outside the scope of thermodynamics. What is the use in thermodynamics of a definition of a quantity that is admitted to be outside the scope of thermodynamics, apart from sustaining an unjustified appearance of dogmatic omniscience?

It is not feasible in general to define work when temperature is not available. This naturally fits with the coherence of the ideas of heat and temperature. Thus for feasible calculations, the definition of heat, as a residual from a work calculation, breaks down when temperature is not defined.

For example, Callen (1960/985) on page 163 writes: "We do not imply anything about enthalpy during the process; the intermediate states of the gas are nonequilibrium states for which the enthalpy is not defined." On page 158 he writes: "for technical mathematical reasons to be elaborated in Chapter 16, statistical mechanical calculations are enormously simpler in Helmholtz representations, permitting calculations that would otherwise be totally intractable." The temperature is needed for the Helmholtz representation. Likewise, the temperature is needed to find the Gibbs potential, which is needed for the definition of work for open system processes.

The insistence on the Born 1921 definition of heat transfer relies on the definability of work. But there is nothing in the Carathéodory 1909 story, on which the Born definition rests, that can be calculated unless conditions are such that temperature is definable, even if the actual calculation of work does not explicitly mention temperature. This problem is not usually mentioned in talk of the Born definition because the Born definition is restricted to closed systems; but when the calculations go on to include open systems, the problem comes out into the open.

Thus it is implicit in the Born 1921 definition of heat transfer that there are limits on its applicability, namely that it needs conditions in which temperature can be defined, even though temperature is not explicitly used for the definition of work. When temperature cannot be defined, neither can work and heat transfers; we are not omniscient, and some of us are happy to say so explicitly. This fits with the essential coherence of the ideas of heat and temperature.Chjoaygame (talk) 17:46, 17 April 2012 (UTC)

Yes, I was a bit wrong in my previous comment, I agree that one does have to assume quasistatic changes. F. Reif puts it well when he says that thermodynamics is a misnomer, it should have been called thermostatics. So, in a rigorous set-up, one only ever considers states of thermal equilibrium. For such states, one can look at what happens if one starts at one state and ends up in another state. Then, as long as one considers only thermodynamic state functions, one can get around the problem of not being able to describe what happens during non-quasi static changes. So, the equation dE = T dS - P dV will remain valid, even if the change in S and the change on V is not quasi static, but then T dS won't be the heat absorbed by the system, and P dV won't be the work done by the system. Simple example: consider a free expansion of a gas where the gas expands infinitesimally from V to V + dV. Count Iblis (talk) 15:40, 20 April 2012 (UTC)

I went to far in some of my above remarks.

Perhaps one factor for confusion is when intentions are not clear as to whether the subject matter is classical thermodynamics in which the only states being considered are states of thermodynamic equilibrium defined as having all fluxes negligibly small or zero, so that in a particular state no change is observable; or whether the subject matter is non-equilibrium thermodynamics in which some flux or fluxes are regarded as going at significant finite rates, and 'states' are defined not only by quasi-equilibrium near enough "local thermodynamic equilibrium" values but also by non-zero fluxes, so that observable change is viewed as part of the 'state'—the so-called "classical irreversible thermodynamics"; or whether the subject matter is processes that have such fast changes or such steep spatial gradients, of intensive variables or of densities of extensive variables, that the "local thermodynamic equilibrium" approximation fails and many of the usual thermodynamic variables are not adequately defined. Also one may think of cyclic processes in which there are repeated significant departures from thermodynamic equilibrium, but the cyclic property still allows useful statements to be made about transferred quantities. In a sense, the cyclic processes are analogous to the quasi-static (quasi-)reversible processes.Chjoaygame (talk) 19:26, 20 April 2012 (UTC).

I'm feeling cold, I'm rubbing my hands

Discuss... Count Iblis (talk) 00:17, 16 April 2012 (UTC)

(Much more fun to rub someone else's hands!) --Damorbel (talk) 08:01, 18 April 2012 (UTC)

The label says: "shake before use"

Which will obviously add heat to the system. Note that we're free to define what e exactly mean by "system". So, if the reply is going to be along the lines that I can't choose to define the system with its system boundaries and external parameters in the way I like, then there is a problem with the theory you are defending.

While I am performing work, there is no (negative) thermodynamic work performed by the system, because its external parameters don't change from start to beginning. The initial state was in some well defined thermodynamic state, so is the final state. The temperature of the system has increased, so heat was added to the system, but it didn't flow to it from some hotter object. Count Iblis (talk) 00:37, 16 April 2012 (UTC)

It hardly follows that just because the temperature of a system went up, heat was added. All kinds of work can be done on systems that increases their temperature, and all kinds of energy added that do it, that are clearly not heating. I can compress a gas and make its temperature rise, but I am not heating it-- I am doing work upon it! But if you exclude addition of energy in ways that are clearly unrelated to transfer of energy via heat flow (which is defined as energy flow due to temperature difference) then you get a component of internal energy that is due to heating and heat only, not work done. That component is what wants for a name. SBHarris 05:15, 16 April 2012 (UTC)

The fundamental problem here is that thermodynamics (according to the modern point of view as tought in university today, not according to what some authors may have written half a century or longer ago) is all about giving a coarse grained description of a system. We're free to choose the level of coarse graining. A system can be treated as a single system, in thermal equilibrium it can be assigned a single temperature and there can be some external parameters. But you can als give a finer grained description, where effectively that system is chopped up into subsystems. Each of the subsystems can be in thermal equilibrium, without these subsystems being in mutual thermal equilibrium. The thermodynamic state space of this finer grained description is obviously a lot larger.

Ultimately, all you have is a large number of particles, the state of which evolves according to the Schrödinger equation . You cannot define heat transfer in terms of this alone. A choice has to be made on what degrees of freedom of the system we want to treat statistically and what degrees of freedom we want to keep in the effective thermodynamic description. Obviously, almost all the degrees of freedom of a system of 10^23 particles are going to be treated statistically. The freedom of choice about this is going to appear at boundary where we just keep the statistical description and where we don't keep it and explicitely keep track of variables.

If I take a bottle half filled with water, shake it and put it back, then thermodynamic work done by the water in the bottle and subsequently that work being dissipated to heat within the bottle will only be well defined if you give a very fine grained description of the bottle. But (and this really is thermodynamics lesson 101 at university, which is why I feel strongly about this point), you are allowed to treat the bottle as one single system. That means that there is no thermodynamic description at that level of the bottle during the shaking, but there is before you start shaking it and after when the contents of the bottle have setled down. You can compute the final state from the initial state if you have an estimate of the work you performed on the system.

Consider the textbook example of the free expansion of a gas. The standard textbook explanation there is based on that the system performs no work and no heat is added to the system. However, if you give a finer grained description, you could say that the expanding gas performs work which is dissipated into heat within the system. The power of thermodynamics lies precisely in that we don't need to consider the very complicated gas dynamics processes during the expansion. The concept of heat and work are defined according to how exactly you define the system (level of coarse graining), where you put the system boundaries, the choice of the external parameters etc. Count Iblis (talk) 15:22, 16 April 2012 (UTC)

Before we use your example we need to be clear on what it is. A "free expansion" of gas, to me, means against no pressure, which does no work, and (in an ideal gas) does not result in cooling. If the gas is allowed to perform work and no heat is added, then thermal energy disappears within the gas (being transformed perfectly into work) and the gas cools (as the velocity of the molecules has decreased as they strike the moving piston and rebound with less velocity and kinetic energy-- something that does not happen in a free expansion). This is where we need a concept like "thermal energy", as we need to say what kind of energy disappears in order to leave the system to turn into work on surroundings, here. It's kinetic energy of gas molecules, but it manifests itself as a temperature decrease of the gas. It's a loss of internal energy, but this is one of those cases where all the internal energy loss shows up as a decrease in temperature. It's adiabatic so that enthalpy change is zero. However internal energy change is not.

I'm trying to understand your other point. It requires TIME for vibrational energy input (like friction or certain types of uneven heating) to completely thermalize in a system, so that the entropy of this added energy is finally maximized. Thermodynamics isn't very good about describing systems in such flux (unless the thermal energy spreads with minimal temp differences from region to region), because the system has expanded in phase space, but not (even at any "point") to the maximum (equilibrium = highest entropy). So yes, thermo doesn't have much to say about it. Nor does physics has much to say about it, because it's a lot of particles in states that we can't know, and it's just too damn complicated for any theory there is. But I sort of take that as a given. We use thermo for situations where thermo was designed to give answers, and that's in slow processes where equilibrium has been reached in most or all "places." And by "places" I mean in collections of atoms large enough to give a statistical temperature and thus have a heat capacity, as happens even while heat is being conducted through a solid. In engineering, for example, even in problems of conductive heat flow, we pretend that the temperature field T(x,y,z) is composed of points. Of course it is not. It is composed of little bits of matter each of which has enough atoms that allow it to have a well-defined statistical temperature, which means that locally it has reached equilibrium and maximal entropy for the energy it contains. But nature is so fine-grained that in most systems this works like mechanics, with large objects, works without resorting to quantum mechanics.

In QM, as I've noted, thermo gets very much harder and Bolzmann-Gibbs entropy goes over to von Neumann entropy and you do have to worry about wave-function collapse. But that's a separate problem from the problems of large-scale non-equilibrium systems (your shaking bottle, or systems with frictive imputs), these are more like the problems of predicting the weather. There's just too much chaos and information, and we simply need to acknowledge that there is no theory that works. SBHarris 18:08, 16 April 2012 (UTC)

SBHarris writes: "It's kinetic energy of gas molecules, but it manifests itself as a temperature decrease of the gas." The kinetic energy of the gas molecules is tied to, one might say partly supplied by, the states of excitation of the molecules and by the potential energy due to the intermolecular forces.Chjoaygame (talk) 17:58, 17 April 2012 (UTC)

I said "ideal gas." Thus, no intra molecular forces and no Joule-Thomson effect. All thermal energy is kinetic (the only time that happens). For most real gases, the J-T effect is strictly a second-order one, anyway. And for many diatomic gases (like air) the vibrational effects are frozen out anyway, so they behave (to good approximation) like ideal gases. Or ideal gases with one detree of kinetic energy for each atom hobbled by the intermolecule bond. SBHarris 21:01, 17 April 2012 (UTC)

Yes, indeed I didn't take account of your ideal gas statement.Chjoaygame (talk) 07:09, 18 April 2012 (UTC)

Yes, in a free expansion experiment, you could look at the work done by the gas, and say tha tthis is zero. However, then you ahve chopped up thesystme in subssystems and are looking at the work done by the subsystems on each other. Now, as Reif explains in his book, thermodynamics is misnomer, it should have been called thermostatics, as it only describes systems in thermal equilibrium. But that doesn't mean that it cannot be applied to systems that undergo rapid change. You can derive exact statements using thermodynamics for such processes, like in case of the free expansion experiment.

Of course, such results involve initial and final states that are in thermal equilibrium. But that is a powerful reason not to make the definition of heat and work dependent on the details as SBHarris argues above, because that would make obscure the fact that such a results are rigorous (i.e. it is not conditional on being able to define temperature while the system is indergoing change, which is not possible to do precisely).

Another comment. It is temperature that is defined using the potential of heat flow when different systems are brought into thermal contact. One doesn't define heat in this way. And how would you define temperature if you were to chose this definition of heat (let's forget for the moment that this defintion of heat is problematic)? One can try the high school definition of temperature in terms of kinetic energy of particles, but this is problematic. That definition assumes the equipartition theorem, which isn't valid in quantum mechancs.

Even for classical systems, it won't work, because it would fail to capture a very fundamental aspects of thermodynamics, i.e. that it ultimately derives from an information theoretic description of a system. It is lack of information about the system that makes a thermodynbamic description useful. Entropy is proportional to the number of bits of intormation that you would need to fully describe the exact state of a system, give the macroscopc thermodynamic specification. Now, if you know all the velocities of all the particles, you have a complete description of the system, the entropy is then identically zero. Temperature remains equal to absolute zero at all times, no matter "how hot" the system gets, as suggested by the velocity distribution of the particles.

If you have complete information about a system, you can let Maxwell's demon be effective, it doesn't have to dump its memory (the Landauer bound is thus irrelevant here). The demon knows in advance when the next molecule will come along for which it has to open the gate, by looking up the system specification and doing some computations. This variant of Maxwell's demon is called "Laplace's demon". Clearly this makes any attempt to base thermodynamics on anything other than information theory paradoxical, as what you would get would be vulneralble to such thought experiments involving demons.

What i.m.o. is the big lesson here is that heat, temperature, entropy etc. etc. are to some extent subjective quantitites, that ultimately derive from how we choose to describe a system. In practice, when deriving thermodynamics from statistical physics in the usual way, you encounter this "subjectivity" when defining the Omega function Omega(E), which govesthe number of energy eigenstates between E and E + Delta E. You could say that we should take the limit of Delta E to zero and work with the density of states. However, Omega(E) should be the number of states the system can be in, and Delta E is a finite quantity. If Delta E were zero, you would know which state the system is in, so you would have complete information about the system's microstate. Now when we look at the familiar thermodynamic quantities, like entropy S = k Log(Omega), then it turns out that the Delta E dependence is utterly negligible, and that dependence vanishes completely when taking the thermodynamic limit. Count Iblis (talk) 02:17, 20 April 2012 (UTC)

This article is a train wreck. Best try again

It should be plain to any reader that instead of getting better the article is getting worse. For example, there is a "lede too long" tag. While the complaint is technically correct, length is not the operative problem. The underlying reason, which is not confined to the lede, is that both the writing and rationale are incoherent, ill-organised, doubtfully expressed, opaque to the reader unversed in physics, assailable to physicists, and self-indulgent. It certainly is neither encyclopedic in its current form, nor very Wikipedic. No names, no pack drill. At the current rate we will get no further than snapping at each other. This is as nauseating an example as ever I have seen, of trying to see further than others by standing on their toes rather than on their shoulders.

Now, the problem is not that there is a deficiency of available expertise in the subject matter. Nor is it clear that we could rescue the project by having any one person rewrite the whole thing (we certainly could, but how are we to identify the right person?) We definitely cannot do anything constructive in the current dogfight mode. Conversely, we cannot afford to let the existing mess stand as a WP article.

So?

So I am not going to prescribe or even propose what the article should look like, thereby prolonging the exchange of spittle and ink, but I do propose that anyone who wants to go off into a fit of the vapours do so now and let the rest get some work done. He can come back later and sneer if he chooses. Those remaining, I suggest that they leave the article alone for a while, archive most of this talk page, and each go off and work out not proposed text or material content, but a section layout. Then compare their products on the talk page. Given goodwill and flexibility that should not be so hard. The major principle should be that one does not veto material that is neither wrong nor better suited to a different or separate article; instead just put discrepant discussions into separate sections.

Then start rewriting each section till either there is a complete article, or it appears that there is a need to split, add or rearrange sections. Steer clear of editing each other's sections, short of actual error corrections. If one person turns to be writing in engineering terms and another in statistical terms, then put those two topics in separate sections for now. Worry about splitting the article later if at all.

And so on.

When all is done (if ever) either split the product into the right number of articles (if desirable) or call in a reader who is not a physicist but is literate and competent in lay English, and engage him or her to work on it till s/he and friends find it reasonably concise, easy to read and possibly to comprehend, without making physicists' teeth curl. No more of this argumentation about terseness and chattiness. Let's have a bit more competence and a lot less possessiveness. This is not a matter of taste, but of function, and infelicities are not just matters of literary taste, but sources of distraction and confusion. Opinions do matter, but not as a substitute for linguistic skills or hard fact.

And if anyone goes into sabotage mode, the rest of us can go into arbitration mode, and see who is left standing. This damned slanging match should stop. Round about now.

Now, no-one need take this exhortation too seriously, and I know some of us will hate it with all the fury of possessive parents, but when they have finished flinging their plates of porridge from their high chairs, I ask all and any of you: is it any worse than the mess currently in this talk page, or the proud product you see before you in the article? JonRichfield (talk) 09:30, 18 April 2012 (UTC)

Couldn't agree more! All I can add is there appears to be a major problem with university phyics for the moment, there appears to be a lot of really bad teaching out there. --Damorbel (talk) 11:05, 18 April 2012 (UTC)

University physics teaches that entropy, temperature, and heat are all statistical concepts that require more than one particle, and are used (in essentially all cases of interest) to refer to very large collections of particles in energetic equilibrium. If we don't start with those assumptions in THIS article, it will go nowhere. Most of the hassle we've had on this talk page is due to the fact that people like yourself disagree with it.

Much of the rest of our definitional problems is a holdout from the days of now-banned user user:Sadi Carnot, who insisted on the purity of usage that heat had to be thermal energy in the act of transfer (thus, heat = heat transfer always), and the very word "heat" even in science, could never apply to thermal energy residing in materials, not moving along a temperature gradient. But there's a residual of usage of heat to mean static thermal energy going back in science a long away, and some of it still remains (as in calling enthalpy "heat content"). Finally, there's a band of people who insist that the purely thermal component of the internal energy of an object or system (which is NOT enthalpy, since it doesn't include mechanical work input or output) can't EVEN be defined, and shouldn't be talked about, even though engineers use the idea all the time (as a differential and change, at least), and use it in their heat capacity calculations in heat transfer. I don't know what to do about these people. When doing calculations, it works. It does not give wrong answers. My opinion is that if it works, it's valid. SBHarris 16:42, 18 April 2012 (UTC)

If you say so, fine. Please produce at least the start of an outline that could accommodate the technical substance of your arguments or preferences. (I reckon that here in the talk page would be one place to do so, but by all means I am open to alternatives.) If other people wish to (a) disagree with you, or (b) include alternative views or material that they can justify in suitable contexts, fine; try to produce outlines that accommodate both, either in sections in the same article or in separate articles with suitable links. Just please avoid trying to shout each other down when they produce material that is only justified in special contexts. That way Wasteland lies. With a little impersonal goodwill, combined discussions should produce a better service to the reader and to WP and possibly each other, than what we have now. JonRichfield (talk) 18:21, 18 April 2012 (UTC)

Try this:-

The heat of a substance or body is the property that gives the sensation of hotness or warmth. Heat is measured by temperature, indicated by a thermometer. A number of different scales have been devised so that thermometers can indicate temperature in a convenient way, usually by the inventors of thermometers. Currently the most used scales are Celsius and Fahrenheit but many have been used down the ages; for some scientific work the Kelvin or Rankine scales is used; these scales have as zero the lowest possible temperature, known as absolute zero; the Kelvin scale has the same size of divisions as the Celsius scale but they are called Kelvins (K); the Rankine scale has the same size of divisions as the Fahrenheit scale the divisions are called 'degrees Rankine' (°Ra).

I suggest that small revisions be highlighted in colour; I tried to put the text in red but failed to find out how to 'do' colour.--Damorbel (talk) 08:15, 19 April 2012 (UTC)

A perfect example of why Damorbel should be asked to not edit this article at all. The above is a definition of temperature, not heat. Heat is not measured by temperature, nor by a thermometer. Temperature is measured by a thermometer. Heat is that energy that flows spontaneously from one place to another as a result of a difference in temperature between one place and another.

Heat and temperature have different physical units, and cannot be connected without using the concept of entropy. Temperature is proportional to the mean kinetic energy of an ensemble of particles in thermal equilibrium; heat is only connected to kinetic energy insofar as it sets the temperatures which cause the energy of heat to flow. The particular type of energy that composes heat is drawn partly from the kinetic energy of particles in matter in thermal equilibrium, but in all real situation such thermal energy is composed of other types of energy as well, which are distributed according to a partition function that varies from substance to substance. SBHarris 17:55, 19 April 2012 (UTC)

The opening section is adapted from a paper copy of the OED; an online version of the OED has this for heat

"noun

[mass noun]

1 the quality of being hot; high temperature:

the fierce heat of the sun

• Physics heat seen as a form of energy arising from the random motion of the molecules of bodies,

which may be transferred by conduction, convection, or radiation."

Now I agree that this OED physics definition is rather limited but surely newcomers to this Wiki article will at least find consistency with my suggested opening paragraph. --Damorbel (talk) 18:35, 19 April 2012 (UTC)

Well, I must of course sympathise with you to some extent, but really, I must far more urgently recommend that you hesitate to rely on lexicographers for cogent definitions of technical terms. Just today I had occasion to consult the internet facility of a very major dictionary, concerning "parasitoid", a matter of which I have a modest understanding. Their definition was biologically illiterate. I agree that the OED text on "Heat", to which you refer, might read more comfortably to the layman than our flowing (or non-flowing, as you prefer) stuff that we have been talking about, but really, OED or no OED, that text cannot possibly be acceptable in our WP article if we don't want to be a laughing stock, perhaps even a reproach and a byword, among our informed readership. It just won't do. Certainly you have a point in that what we have is heavy going to the innocent and with due deference to another author who eschews "chattiness", colloquiality, and comprehensibility, I insist that we should include at least introductory material that the intelligent layman can understand, but not by presenting inaccuracies for him to understand. Accuracy before comprehension, say I, though comprehension is next to godliness at least. JonRichfield (talk) 19:58, 19 April 2012 (UTC)

You refer to 'inaccuracies' but do not identify them. Care to explain? --Damorbel (talk) 07:07, 20 April 2012 (UTC)

we solve such problems with other words that have both common and tech meanings, by having the word direct to the dab page, and have the technical meaning with a paren. Thus, work directs to the work (disambiguation) and if you want the type of work that comes in in joules, you need to go to the technical work (physics) or work (thermodynamics). But heat directs here, since there isn't a heat (physics). Instead, people have insisted on shoehorning popular usages into this article, which otherwise could be a technical one. It's stupid, but there it is.

I've suggested otherwise before, but gotten little support. See above. Want to try this again as a suggestion? That would mean this article would be renamed heat (physics) or heat (thermodynamics). Actually, I think there's enough difference in the really technical thermo term to have a heat (thermodynamics) article where we only discuss heat transfer, and perhaps ALSO a heat (physics) article we could discuss arcane ideas like heat content and what we call the energy that results in heat capacity, when it's not going anywhere (i.e., the isovolemic or non-work component of internal energy change). What engineers often think of as heat (more than just heat transfer, but still measured in joules). That would at least cut down on the lede length, in the science articles. SBHarris 21:06, 19 April 2012 (UTC)

I don't agree with SBharris' proposal that would have the effect that the physics and chemistry articles should forgo their hard-won understanding of thermodynamics, by admitting an idea of "thermal energy" in whatever guise of language SBharris wants to use. Internal energy in general cannot be rigorously broken into parts as SBharris wishes; that is perhaps the main lesson of thermodynamics; that is why it is called internal energy; if the idea of SBharris were rigorously valid, the notion of internal energy would not have been invented.

As I have said below, physics and chemistry do allow a notion of heat production which is not just a matter of heat transfer from one place to another.

Let the engineers do their thing in their own articles, but let them not foist it on physics and chemistry articles.Chjoaygame (talk) 21:26, 19 April 2012 (UTC)

I believe it is modern thermodynamics that insists that heat is only heat flow as a result of temp-difference. It is physics and chem and engineering that expand the concept of heat to describe that thermal energy that increases temperature and that simply appears out of nowhere (without being added as heat flow), when you do work on a system (example: compress a gas in a cylinder, and it increases in temperature). In such a scenario you can then draw heat from it, and when you get to its former temp you will find that the heat you withdrew was equal to the work you did. So, I think we should have an article on the purist thermo definition, heat (thermodynamics) and leave the wider definitions that include thermal energy to physics and chem as heat (physics). Damorbel's notions of heat as being like temperature in common vulgar use, can go the dab page, as they are already ("90 degrees of heat in the Summer").

There is a perfectly usable definition of the part of internal energy that is thermal, and that is-- it's the part that has been thermalized, so that it cannot then be withdrawn EXCEPT as heat! That happens immediately to energy you add as heat flow, but it takes time with other types. A very slow compression work is immediately thermalized and immediately irreversible (if you want the energy back, you pay max entropy cost for it). A fast compression generates shock waves that bounce back and forth and take time to thermalize, and during that time, you can get some of your original work back because entropy hasn't increased to the max for the energy you added. Thermal energy is energy that has maximized its entropy for its temperature, by finding all degrees of freedom in the system available to it. That takes time, and I suppose it should thus be noted that the amount of thermal energy that resides in an object, is thus a function of time. But it's a useful concept if you know your timescale.

One of my favorite examples is in the proton spins of ortho vs para hydrogen. At room temp there's enough energy that 75% of H2 is ortho (spin aligned) which is a high energy state, see spin isomers of hydrogen. When you liquidfy the stuff, this should equilibrate to the low energy form, but it takes days to do so-- at first you liquid hydrogen has the same ratios of ortho/para as it did at room temp! The heat the ortho--> para conversion generates is enough to boil the liquid again, so engineers have to use a catalyst to get the extra energy out (thermalize it). Essentially, when you liquify H2 from room temp, the various translational and vibrational modes all go to 20 K, but the spin-temperature stays at room temp for awhile, as though this thermal energy were in an insulated compartment at a higher temp! There's a lovely example of having a kinetic barrier to thermal equilibrium and removal of maximal thermal energy. But it does eventually happen. You can think of it as a sort of slow phase change, and the spin-isomeric transition as a sort of latent heat. But that's not a perfect analogy, since in other phase changes the temperature of the phases is the same. Here, the spin-temp of the H2 is higher than the temp of the liquid, but heat cannot flow by conduction or diffusion. It has to flow in tricky ways to get energy from nuclei into energy of translation of molecules. It is a form of stored "heat" however, as it acts like thermalized energy at room temp, and you can't convert it to work, willy-nilly. The spin isomer energy has equilibrated with thermal energy at room temp, and it acts like themal energy at room temp, even after you've cooled the hydrogen down to cryogenic temps. SBHarris 23:19, 20 April 2012 (UTC)

the term "thermal energy" request for comment

There have been some recent edits for the term "thermal energy".Chjoaygame (talk) 03:16, 6 April 2012 (UTC)

Comment 1

On this talk page, one editor put the view that the words 'thermal' and 'energy' could be put together to form the phrase 'thermal energy' as a simple matter of ordinary syntax. This view would make perfect sense to someone who believed in the caloric theory of heat. The caloric theory of heat is not valid in thermodynamics, but it is not a silly theory in that under special conditions when energy cannot be transferred as work or chemical potential energy, but only as heat, as considered by no less a physicist-chemist combination than Laplace and Lavoisier, then quantity of heat transferred obeys the law of conservation of energy. The difficulty for the caloric theory arises when modes of energy transfer other than thermal are allowed. Such revered figures as Carnot and Kelvin were not clear in their minds about this in the early days, until the first law of thermodynamics was well understood. In general such other modes are allowed in thermodynamics; moreover there is no general resolution of internal energy into thermal and non-thermal components; that is part of the import of the first law of thermodynamics.

In tags to proposed edits, another editor puts the view that Wikipedia should effectively ratify the use of the term "thermal energy" because it is sometimes used by engineers. In the lead that he proposes, he argues that the term "thermal energy" is naturally related to heat capacity. In the lead that he proposes, he offers what, at first glance by a non-thermodynamicist, looks like a precise definition of amount of "thermal energy", and offers what looks like a definition of temperature as "the mean kinetic energy [...] of the system". These definitions again would make perfect sense to someone who believed in the caloric theory of heat,and they seem to conform with ordinary language usage. This proposed lead cites page 14 of an engineering text by Incropera and others. The library is closed today and for the moment I must make do with pages from another version of that text from the internet. On page 2 the authors write of "thermal energy in transit". The authors often are careful to write of "the sum of thermal and mechanical energy", and they write of "thermal energy generation". On page 9 they write: "Radiation that is emitted by the surface originates from the thermal energy of matter ...". On page 10 they write: "A portion, or all, of the irradiation may be absorbed by the surface, thereby increasing the thermal energy of the material". They repeatedly use the term "thermal energy" like this on page 10. It seems to me that these are occasions of lapse from sound expression or thinking by these authors, not consistent with their care on other occasions. (Also it is relevant that heat can pass through a surface, which has two dimensions, but can be absorbed only by a body with three dimensions.) On page 16 they write: "the sensible and latent components of the internal energy (U_sens and U_lat respectively), which are together referred to as thermal energy." This looks like an explicit definition of "thermal energy" as a component amount of heat in a body. But it also looks like a lapse into the caloric theory way of thinking, because more properly in thermodynamics, sensible and latent heats are defined not as components of internal energy but as components of heat transferred. It is clear enough that we are looking here at special engineering usage, that is not supported by the ordinary line of thinking in thermodynamics.

Perhaps a solution to this would be to put into the article an explicit statement that engineering usage sometimes departs from ordinary thermodynamic usage in ways that could be specified. I would suggest that the lead should only advert to the matter, not detail it or argue for it as is done in the currently proposed version. I would suggest that detail and argument be kept to the body of the article.Chjoaygame (talk) 03:16, 6 April 2012 (UTC)

response 1b

The lede now does differentiate thermodynamic use from engineering use. Engineering use doesn't "differ" from thermodynamics (which simply says nothing on the subject in the modern formulation), but rather extends it (breaking internal energy down into components of interest). Thermodynamics is not concerned with many heat transfer situations, such as heat conduction/transfer within solids. So it lacks terminology for what happens there. Engineers and physicists are forced to treat conduction and convection, however, and they need terms of art to do it. In all heat transfer problems, energy conservation IS thermal energy conservation (you can call that "caloric theory" if you like, but it is still true), so the components of internal energy that are thermal and nonthermal need to be identified (or else you cannot predict temperature-field evolution within your system). That is what is happening here, in terminology. "Thermal energy" is a very useful, even essential, term of art in treating thermal conduction and convection.

As to whether thermal energy is "latent heat plus sensible heat" or "sensible heat" alone, it appears from what you've written that Incropora and DeWitt may have changed their minds on this between editions. There may even be disagreements between texts on whether or not latent heat is to be incorporated into thermal energy. If a system has ways of storing or giving up sensible heat, clearly this needs to be taken into account when you do heat conduction problems (for example a microwaved caserole that is full of little bits of ice). If there are no phase changes involved, so that any internal energy changes result in termperature changes, then the sensible heat concept is enough. The point is that engineers need a term for ALL of the part of internal energy that is available if you want to extract heat from the system or object, using a cold reservoir, and this certainly includes both latent and sensible heat. This is called "thermal energy." If thermodynamics has a name for it, please let me know. Clearly a term is needed, and engineers have one. Thermal energy is that term. SBHarris 18:35, 6 April 2012 (UTC)

We have progress here. SBHarris thinks that internal energy can be broken down into components of interest. He also thinks that thermodynamics is not concerned with many heat transfer problems, such as conduction within solids. So he thinks that thermodynamics lacks terminology there. These views of SBHarris are important and need a reply.Chjoaygame (talk) 03:56, 7 April 2012 (UTC)

'internal energy can be broken down into components of interest'

A main import of the first law of thermodynamics is that internal energy cannot in general be broken down into components of interest by separating ""thermal"" from ""dynamic"" components.

The belief that it can be so broken down is too close to the caloric theory of heat for comfort.

SBHarris was kind enough to give us a sample of the effects of such a belief. He wrote above "But I'm pretty sure that thermodynamic work on a system is meant to be fully reversible. That needs checking." In response did try to check it for him. I wrote a fair bit, but evidently it seems I didn't make the situation clear enough. The Joule-Thomson experiment, with a system of two thermally isolated chambers separated by a porous plug, each chamber with its piston to control its pressure or volume, is the classic example that shows that thermodymanic work is not meant to be fully reversible. I am sorry I did not mention it in my previous response, which was in vague general terms.Chjoaygame (talk) 03:56, 7 April 2012 (UTC)

The Joule-Thomson (J-T) experiment in which a gas expands without doing work, does not involve thermodynamic work, as the gas explicitly does not DO any work in this experiment. And of course such a process is not reversible, as it is not isoentropic. Entropy increases in a J-T exapansion, so it's not reversible. That's the point of an entropy increase, don't you know. Reversible processes are isoentropic expansions and compressions, all of which are adiabatic, and thus reversible (you can extract work and then add it back, as many times as you like, and no heat is removed from the system, although its temperature goees up and down). Adiabatic/isoentropic processes are, by definition, not J-T processes. The J-T expansion is much like a phase change-- temperature drops (or even increases) due to a potential energy change in the gas. It is no more mysterious themodynamically than water vaporizing to a gas spontaneously. The "heats" (or heat contents or thermal contents) involved, are analogous to latent heats. That's it. When your sweat evaporates, it leaves your skin cooler. So what? SBHarris 20:10, 7 April 2012 (UTC)

SBHarris offers several propositions here, which I will quote as dot points, and then respond to:

• "The Joule-Thomson (J-T) experiment in which a gas expands without doing work, does not involve thermodynamic work, as the gas explicitly does not DO any work in this experiment."

My response: Joule and Thomson did a fair number of various experiments with porous plugs. Phil. Mag., (1852) ser 4 vol 4: 481–492;; Phil. Trans. Lond. (1853) 143: 357–365 Phil. Trans. Lond. (1854) 144: 321–364; Phil. Trans. Lond. (1862) 152: 579–589. The experiments are discussed in general terms, with little direct reference to particular experimental details, in secondary and tertiary sources. Planck (1923/1927), pp. 130-133; Partington (1949), pp. 615–621; Adkins (1968/1975), § 9.2; Bailyn (1994), § 8.7. The latter three show diagrams of the arrangement that I mentioned just above, with two chambers each with its own piston that controls pressure or volume. The secondary sources all discuss the work done on or by the gas in the two chambers during the experiment. Joule and Thomson 1852 write on page 482: "Let air be forced continuously and as uniformly as possible, by means of a forcing pump, through a long tube, open to the atmosphere at the far end, ..."

• "And of course such a process is not reversible, as it is not isoentropic. Entropy increases in a J-T exapansion, so it's not reversible."

My response: agreed that the Joule-Thomson process is not reversible, but not agreed that it is necessarily "such a process" that is to say that it necessarily occurs "without doing work", as remarked just above.

• "Reversible processes are isoentropic expansions and compressions, ..."

My response: agreed that isoentropic expansions and compressions are reversible; in general, they must be made infinitely slowly.

Nevertheless, not all reversible processes are isoentropic; for example, the isothermal limbs of the Carnot cycle, conducted infinitely slowly, are reversible, but entropy is gained or lost by the working substance. Adkins on page 54 writes about the first limb: "The working substance expands isothermally and reversibly at temperature $\Theta _{1}$ absorbing heat $Q_{1}$."

• "all of which are adiabatic, and thus reversible ..."

My response: Not all adiabatic processes are reversible. Adiabatic processes do not have to be infinitely slow. When they are not infinitely slow, they are irreversible. Some of the Joule-Thomson experiments, ideally performed, involve adiabatic expansion. For example, Adkins writes on page 164: "The Joule–Kelvin (or Joule–Thomson) expansion is a steady flow process in which a gas is forced through a porous plug or a throttle under conditions of thermal isolation from the surroundings."

The Gay-Lussac experiments which preceded the Joule–Thomson experiments, according to Bailyn p. 320 (I did not check the original Gay-Lussac paper), involved free irreversible adiabatic expansion, no work being done, and no change in the internal energy of the gas.

• "Adiabatic/isoentropic processes are, by definition, not J-T processes."

My response: agreed that isoentropic processes are not Joule-Thomson processes.

But not all adiabatic processes are isoentropic. Examples are some of the Joule-Thomson experiments (and their Gay-Lussac predecessor according to Bailyn), ideally performed, as just above; they are adiabatic but not isoentropic.Chjoaygame (talk) 16:40, 8 April 2012 (UTC)

Though not in general, nevertheless in particular ways, internal energy can be represented as a sum of terms. The procedure is routine: to stipulate one's choice of a particular system of interest, with one's chosen stipulated independent variables (for example a closed system, with entropy S and volume V). Then one describes the particular constitution of one's system by its fundamental equation in these terms, U = U(S,V), that gives the internal energy U as a function of the stipulated independent variables. Experiment often shows for simple systems that this function is differentiable, even twice differentiable. Then one has dU = T dS + P dV with $T\ \equiv \ (\partial U/\partial S)_{V}$ and $P\ \equiv \ (\partial U/\partial V)_{S}$. But this depends on the particular stipulated choices. Expressions for different choices can be derived by Legendre transforms, and the sums of terms will be different. This is the mathematical expression of the fact that in general, the internal energy cannot be broken down into components of interest. To misunderstand this is usually to be still clinging, in one's internal thinking, to the caloric theory of heat.

As I remarked above, it seems that the proposed source Incropera et al. do indeed in their internal thinking, at least at times, still cling to the caloric theory of heat. SBHarris points out that they seem to have changed their minds between editions. If so, I would say it is a symptom of their internal clinging to the caloric theory of heat, no matter how often they make explicit denials of it, and no matter how often they write correctly in addition to their confusing writings. The Wikipedia should not seem to support the caloric theory of heat as a general principle.Chjoaygame (talk) 03:56, 7 April 2012 (UTC)

"thermodynamics is not concerned with many heat transfer situations"

SBHarris is here pointing out that classical thermodynamics is not concerned with following the time course of processes that are significantly far from equilibrium. But non-equilibrium thermodynamics is so concerned. The Wikipedia article on thermodynamics has been criticized for giving too much emphasis to non-equilibrium thermodynamics at the expense of due emphasis on equilibrium thermodynamics. It seems that the alleged overemphasis has not led SBHarris to take too much notice of non-equilibrium thermodynamics, even in the form that is sometimes called "classical irreversible thermodynamics". But that is not a reason to accept SBHarris's unreserved statement that "thermodynamics is not concerned with many heat transfer situations". It is perhaps a reason for SBHarris to check some texts of non-equilibrium thermodynamics.

Indeed, the present articles on thermodynamics and on heat do not adventure into the definition of heat transfer for open systems. SBHarris is apparently not aware that some texts, such as Kondepudi & Prigogine 1998 do indeed give valid definitions of that. It is true that the Kondepudi & Prigogine 1998 definition is unhappily not in terms of Gibbs' natural variables (see http://vixra.org/pdf/1111.0024v2.pdf ).

SBHarris above adverts to a definition of heat transfer including convection, which can be described in terms of open systems, that does not actually distinguish heat transfer from internal energy transfer. Such an empty or insignificant definition can be found even in texts that one might expect to be reliable, such as De Groot & Mazur 1962. So SBHarris can be forgiven for this mis-step. But engineers as a group cannot be forgiven for it, and we need to expose this clearly as our article is progressively developed.Chjoaygame (talk) 03:56, 7 April 2012 (UTC)

a proper term for "thermal energy"

SBHarris asks for a proper term for "thermal energy". As I remarked above, the very concept is mistaken and no such proper term, can, in general, exist in thermodynamics or in engineering insofar as it would be comfortably consistent with thermodynamics. As I pointed out above to Damorbel, putting two ordinary language words such as thermal and energy together, though permitted in ordinary language syntax, does not justify a term of art such as the proposed "thermal energy". Wikipedia should not seem to ratify or underwrite such a synthesis as if it were a term of art, and indeed it seems it needs to warn specifically against it. It would perhaps be reasonable for this article to mention the use of the term by some but probably not all engineers, at the same time pointing out how, unless read in a very restricted way, it contradicts thermodynamics.Chjoaygame (talk) 03:56, 7 April 2012 (UTC)

Look, engineers who do heat transfer must work with conservation of the energy changes brought about by heating in materials. In a control volume, the energy must be conserved at each moment. The heat into the volume, minus the heat out, may be equal. However, if they are not, the residual energy left in the material due to heating needs a name. A change in internal energy is not enough, because we need some asurange that this change is reversible if we try to extract this energy with reverse thermal gradient. The energy change is latent+sensible energy, heating energy, heat content, caloric, whatever you like. It is NOT "internal energy". It is a reversible change in internal energy strictly due to heating and cooling. This is conserved quantity, since any energy stored in a substance by pumping heat into it, will also be removed if you extract heat FROM it (so long as you wait long enough for all reactions, chemical and otherwise, to come to equilibrium). So this is a very useful concept. It's a interesting variety of energy. It's more than just kinetic energy also. It needs a name. We have a name. Engineers have a name. You don't like the name. That's too bad. I'm so sorry. SBHarris 19:22, 7 April 2012 (UTC)

response 1a

Chjoaygame, you write:- "These definitions again would make perfect sense to someone who believed in the caloric theory of heat". The term 'thermal energy' was applied by J C Maxwell to the kinetic theory as he developed it, it has nothing in common with the caloric theory. Kinetic theory was developed by Maxwell and others because Lavoisier's caloric theory where heat was considered to be a fluid, simply did not explain many observations such as 'heat is not conserved' and the particle (atomic) nature of matter; there is no possible way to explain quantum effects by caloric theory. --Damorbel (talk) 06:07, 6 April 2012 (UTC)

In the first edition of Maxwell's Theory of Heat (1871) I find just three instances of the use of the phrase "thermal energy".

On page 153 I find:

The heated body would thus be rendered perfectly cold, and all its thermal energy would be converted into the visible motion of some other body.

(Also, relevant to a different question, on page 153 I find:

Admitting heat to be a form of energy, the second law asserts that it is impossible, by the unaided action of natural processes, to transform heat of a body into mechanical work, except by allowing heat to pass from that body into another body at a lower temperature.)

I find on page 187:

When the parts of a system are at different temperatures, and if there is thermal communication between them, heat will pass from the hotter to the colder parts by conduction and radiation. The result of conduction and radiation is invariably to diminish the difference of temperature between the parts of the system, and the final effect is to reduce the whole system to a uniform temperature.

During this process no external mechanical work is done, and when the process is completed, and the temperature of the system has become uniform, no work can be obtained from the thermal energy of the system.

(Relevant to a different question, I find on page 283:

Hence, whether we consider the radiation of heat as effected by the projection of material caloric, or by the undulations of an intervening medium, the outer surface of a hot body must be in a state of motion, provided any cold body is in its neighbourhood to receive the radiations which it emits.)

Again I find on page 284:

The conclusion at which we shall arrive, that a very considerable part of the energy of a hot body is in the form of motion, will become more evident when we consider the thermal energy of gases.

Perhaps we may yet find Maxwell using the phrase in other places. Perhaps Damorbel already knows where, and will very kindly tell us?Chjoaygame (talk) 07:50, 6 April 2012 (UTC)

Maxwell's 'Theory of Heat' went through several editions, sum during his lifetime (He died in 1879) and notably by John Strutt (Lord Rayleigh). Maxwell made fundamental revisions to the book himself, he freely admitted that his definition of entropy was mistaken.

I did not find any instance of the phrase 'thermal energy' in Maxwell's 1867 paper, On the Dynamical Theory of Gases, Philosophical Transactions of the Royal Society of London, 157: 49-88.Chjoaygame (talk) 08:08, 6 April 2012 (UTC)

Maxwell's 'Theory of Heat' ran to perhaps ten editions which he himself revised on some important matters such as entropy, so you must look only in the later editions. I think the last edition was edited by Lord Rayleigh who had deep knowledge of Maxwell's works. The period 1860 - 1910 was a time of profound developemnet in thermodynamics and statistical mechanics; much work as done - remember that as late as 1900 there were many doubters e.g. Ernest Mach as to the validity of atomic theory. Equally the concept of energy was far from universally accepted, in fact it is safe to say most scientists were much happier with caloric theory; even today many cannot distinguish the differences between the hopelessly outdated caloric theory and kinetic theory. --Damorbel (talk) 10:52, 6 April 2012 (UTC)

In the 1902 edition revised by Rayleigh, the instance of the phrase 'thermal energy' that was on page 187 of the first edition had been removed. The other two instances of it were allowed to stand. No further instance was added.Chjoaygame (talk) 13:21, 6 April 2012 (UTC)Chjoaygame (talk) 13:23, 6 April 2012 (UTC)

Comment 2

The term "thermal energy" appears in many thousands of books; no doubt many of those uses would be wrong, or unsatisfying, to a thermodynamicist. Yet others are probably used in a more rigorously correct way, where the inability to in general distinguish thermal from other types of energy is recognized, or at least not violated. So the issue is not whether to use "thermal energy", but where and when to use it without being incorrect, or without being significantly incorrect in practice. Dicklyon (talk) 07:02, 6 April 2012 (UTC)

response 2b

Dickylon, I know of no places where there is any difficulty figuring out which part of thermodynamic "internal energy" is "thermal energy." Thermal energy by all definitions is the part of internal energy that changes when you add heat to an object, or extract heat from it. It is also the part of internal energy that you can, in theory and practice, extract as heat, using a cold reservoir. That is simple enough, but absolutely essential if you're looking at problems of heat conduction (with heat sources and sinks added), which thermodynamics largely ignores. Conservation of internal energy is not enough to do all heat transfer problems, particularly transient conduction problems: for that, conservation of energy needs to be translated into temperature changes in some way (see heat equation), and in order to do that, you need the concept of heat capacity, or thermal diffusivity of which heat capacity is an essential component. Integration of heat capacity and temperature (plus phase change energy if you have any of that happening) gives an energy term which defines thermal energy, and yet is not internal energy (rather is the part of internal energy that is available to make or absorb heat, even if the heat hasn't been extracted from the object or system, yet). In many problems, if there were no term for this, you'd have to define it mathematically and make up a term. Well, engineers have made up a term! Thermal energy is what thermodynamicists used to call "heat content" (I don't know if they still do or not). But whether or not they do, what is the problem, here? Engineers need a term. So would thermodynamicists if they did engineering heat transfer problems. SBHarris 18:18, 6 April 2012 (UTC)

SBHarris writes above: "Thermal energy is what thermodynamicists used to call "heat content ..."."

What some thermodynamicists sometimes called 'heat content' is enthalpy. Enthalpy is a perfectly valid thermodynamic potential which can be derived from internal energy by a Legendre transform. It does not fit the bill for the "thermal energy" that SBHarris proposes.Chjoaygame (talk) 02:33, 10 April 2012 (UTC)

SBHarris writes above: "Thermal energy by all definitions is the part of internal energy that changes when you add heat to an object, or extract heat from it." No, SBHarris, this is not the case. The heat you add (or remove) to (from) an object may well induce change of state, in which case there is no change in thermal energy because the will be no change temperature. --Damorbel (talk) 06:56, 25 April 2012 (UTC)

====response 2a====

In response to Comment 2 made by Dicklyon, I would say that it is an issue as to whether we make the Wikipedia appear to ratify the term "thermal energy" as a properly defined technical term or term of art; or whether we leave it as a phrase that can occur in the ordinary language as opposed to as a term of art, which the Wikipedia has no automatic duty to examine.Chjoaygame (talk) 08:22, 6 April 2012 (UTC)

Wikipedia has as much duty to examine terms of art as terms of ordinary language use. Where are you getting this idea? Every natural science discipline has terms of art. As for the ordinary language, WP is the preeminant web source of dilitation on pop culture, including terminology. SBHarris 18:18, 6 April 2012 (UTC)

Ah, yes, I am sorry. I wondered if my meaning was misrepresented by my sentence structure there. I should have re-cast my sentence to make it clear. The faulty clause is "or whether we leave it as a phrase that can occur in the ordinary language as opposed to as a term of art, which the Wikipedia has no automatic duty to examine." My phrase "as opposed to as a term of art" did the misleading and would have been better left out. I would have done better to write 'or whether we leave it as a phrase that can occur in the ordinary language, which the Wikipedia has no automatic duty to examine.'

My meaning is that the Wikipedia can be expected to examine terms of art in scientific articles like ours here; but the Wikipedia has no automatic duty to examine phrases that can occur in the ordinary language. The Wikipedia is neither a dictionary nor a grammar. It is an encyclopaedia.Chjoaygame (talk) 02:09, 7 April 2012 (UTC)

There is much crossover between dictionaries like Wiktionary and encyclopedias, which is why there have been encyclopedic dictionaries and why historically encyclopedias are alphabetically arranged (WP is not, since it is not linear, although some necessarily-linear parts of it, as material within some articles, are alphabetical). So there is great overlap. There is no work in common English which does not have a WP article. See the one on you if you don't believe me; the dab pages for other absolutely common words like me and them contain the various meanings and some prelim definition, and the pages dab'ed nearly always etymologies and full definitions. The only point of WP:NOTDICT is that the focus of WP articles should not be on the word itself and etymology, although often some or all of that is included in the articles we do have (which also have more).

You can fulminate all you like about what you think WP SHOULD be, but often such opinions fail in the face of seeing what WP actually IS. All that means is you don't have enough experience here. So stick around. You can give your opinions, but as a newb (experience-wise-- just making edits for three years in and of itself doesn't count), we don't really have to take you seriously until you know what you're talking about. It takes 10,000 hours to master any complex subject, and probably that long to really know WP. I'm not even there, yet, and I've 15 times your edits, on a vastly great range of topics, and a lot of arguing on WT. Your 2000 edits, almost entirely on things like Planck's law and thermo topics, and almost nothing in the WP: or WT: namespaces, does not qualify you as to any expertise as to how Wikipedia works. Please try to know what you don't know. If I need to know more about Planck's law, I'll come to you (years ago you might have explained to me why lambda(max) and frequency(max) of the blackbody curve don't multiply to c; but I understand that now). However, when it comes to how WP works and what it is, perhaps you could slap that student sign on your forehead. As we all need to frequently with most areas of our lives.

In any case, thermal energy is clearly a term of art in heat transfer engineering (hell, do you know anyone who uses this in common language?!), and so should be discussed and have an article on WP. If the engineers sometime cannot agree whether to include latent heat in it, that makes it no worse than many another term in science, not all of which are defined by the CIPM or NIST (see weight, where nobody seems to care about ISO). Some terms like matter have even worse definitional problems. This article on heat is nothing special in that regard. SBHarris 18:40, 7 April 2012 (UTC)

Again I am sorry I left in the phrase "as opposed to as a term of art". It was intended to make things clear, but it had the opposite effect.

My response to Dicklyon's comment 2 was not intended to irritate you or to reflect on Wikipedia policy. Dicklyon's comment 2, it seemed to me, was suggesting that we should try to tell people how to use the phrase or term "thermal energy", assuming that it would be used and that the Wikipedia was thereby obliged to comment on it and perhaps thereby endorse its use. My point was that it is a question as to whether we should regard it as a phrase of the ordinary language or as a term of art; if it is to be regarded as a phrase of the ordinary language, the Wikipedia would not be obliged to comment on it (partly because it is not easy to tell people how to use the ordinary language); if it is to be regarded as a term of art, then it makes more sense for the Wikipedia to say something about it.

On the substantial question here, it seems that you and I agree that the words 'thermal energy' are candidate as a term of art, not just as a phrase of the ordinary language.Chjoaygame (talk) 13:37, 8 April 2012 (UTC)