Talk:Heat

Hard to understand, needs attention.

I was just looking for a fundamental explanation, but this article reads like a debate among philosophers and historians. Gives the impression that there is no agreement among scientists as to what "heat" is, and is too complex and obscure for general audiences. There is certainly a place for such information, but it needs to be deeper in the article, not first. According to Wikipedia's guidelines, There should be a opening description for general readers, that represents the general consensus, and then work up to the different opinions and interpretations for more advanced, knowledgeable and expert readers later in the article. Perhaps the article needs to be flagged for attention, but I dont know how to do that. Solviva (talk) 04:28, 7 April 2025 (UTC)

Yes, your comment has some validity.

For thermodynamics, the fundamental explanation is that, for a closed system, heat transfer is the unique alternative to thermodynamic work, and that thermodynamic work is defined by macroscopic criteria, while heat transfer occurs by microscopic mechanisms, namely conduction, radiation, and friction. That is a combination of a definition and an explanation, not the same thing as a straight definition.

One line of thinking that you could advocate is that the article should be about heat in general, partly along the lines of a dictionary, where all meanings are considered. Traditionally, the Wikipedia article has been about heat as considered in thermodynamics. I accept that tradition. Heat in thermodynamics is defined for closed systems as a mode of energy transfer that is alternative to energy transfer by thermodynamic work, which is itself a carefully technically defined notion. That has the advantage of providing a clean and logically secure definition for thermodynamics. It is the foundation of thermodynamics. It is a definition by exclusion, which is a little unusual for ordinary language. But clean logical security is important for such a basic topic as thermodynamics.

Though your comment is reasonable, and I can see pretty clearly what you mean, I don't exactly agree with the analysis that you give. There is a difference between a general consensus and an ordinary language account. The thermodynamic consensus isn't something reserved for more advanced, knowledgeable readers; it's something for the beginner, right from the start.

This question comes up from time to time. You can bring it up again. There will be proposals to make the article fit better with the ordinary language ideas of heat. The discussion will bring in many instant experts, some of them convinced that they have the one right answer; they are sometimes so convinced of their own rightness that they can outstay all others. The result will be very damaging for the article, though perhaps you may feel it is already damaged beyond repair?

One is concerned that the leading definition in Wikipedia is often quoted as authoritative, and that a loose or vague definition will not be good for such a purpose.

Someone who looks up 'heat' in Wikipedia is looking for something more exact than the ordinary language usage, perhaps a fundamental explanation. If someone doesn't know what he means by the ordinary language word 'heat', Wikipedia isn't the place for him to find out; he should go to a dictionary.

May I suggest that you consider the possibility that a definition by exclusion can still be intelligible to the ordinary person.

Perhaps you may like to point to specific items in the article that could be improved? Or propose or make some specific improvements?Chjoaygame (talk) 09:33, 7 April 2025 (UTC)

The lead section in any Wikipedia article is intended to be helpful to the widest possible audience. I can suggest that the lead should provide an explanation, not a definition. More advanced information should be placed lower down in the article. See MOS:INTRO.

The widest possible audience includes many who are not yet familiar with concepts of thermodynamics, closed system, macroscopic criteria, conduction, radiation. Some good guidance is available at WP:Make technical articles understandable. Dolphin (t) 13:21, 7 April 2025 (UTC)

Thank you, Editor Dolphin, for your helpful specific suggestion that the lead start with an explanation, not a definition. We can try that.Chjoaygame (talk) 16:57, 7 April 2025 (UTC)

Thank you, Editor Girth Summit, for your helpful undo, with your edit summary "I'm not sure this is an improvement - it does not seem to comply with MOS:FIRST, which essentially says that our first sentence should define the subject." I agree with you on this point. Like you, I would prefer that the definition come first. I was just offering a trial.

Though it perhaps seems obvious and simple, the physical conception and thorough explanation of heat took centuries to settle. It has been worked on for over a decade in Wikipedia.Chjoaygame (talk) 19:15, 7 April 2025 (UTC)

Erm... you're welcome? I'm not sure if your thanks are sarcastic or not - text isn't a great medium for conveying nuances of language like that. Thanks for offering a trial, but I honestly don't think it was an improvement - to my eye, it looked like it would more complicated for a lay reader, not less so. If the three of you already engaged in this discussion disagree, however, then I won't kick up a stink about it. Girth Summit _(blether) 19:27, 7 April 2025 (UTC)

Thank you, Editor Girth Summit. No, I was talking straight, not being sarcastic. I agree with you on that point. For me, my trial edit was not an improvement. 'Heat' is an abstract term, and not too easy to present.Chjoaygame (talk) 19:37, 7 April 2025 (UTC)

OK, good to know. I can see that a subject like this would be difficult to get right, whatever that might mean, and there are inevitably going to be differences of opinion on what the best way to start it would be. Girth Summit _(blether) 20:45, 7 April 2025 (UTC)

Thank you, Editor Girth Summit. I think that a big problem is that the definition of heat transfer is by exclusion. One can't be sure that one has listed all the possible modes of transfer other than thermodynamic work and matter transfer. So the resort is to just say 'whatever else'. That is logical but not too intuitively satisfying. The Wikipedia consensus has been that logic is essential, because thermodynamics seeks to be truly general. The present list (thermal conduction, electromagnetic radiation, friction) is quite good, but it doesn't please everyone. For example, some people like to list 'convection' as a mode of heat transfer, though it isn't such, as observed long ago by Maxwell; it's a form of energy transfer in association with matter transfer. Friction isn't put on the list in common parlance, though it was noted by Clausius, and was the basis of the Joule experiments, and had been focused on by Rumford, and is emphasized by Planck in some papers in German that are apparently? not available in English translation.

So definition by exclusion is a hitch, but I think it has to be accepted.Chjoaygame (talk) 02:49, 8 April 2025 (UTC)

The below Section, Talk:Heat#edit history of Wikipedia article on Heat is relevant to this Section. The very edit history appears as "a debate among philosophers and historians [aka Wikipedia editors]. Gives the impression that there is no agreement among scientists [aka Wikipedia editors] as to what "heat" is, and is too complex and obscure for general audiences [aka Wikipedia editors]." In my opinion/observation, this is evidence that the thermodynamic concept of 'heat', and its "fundamental explanation", are indeed "hard to understand, [and] need[s] attention." The request for explanation in the lead has to allow that the lead should start with a "concise definition". The "widest possible audience" may be hard to identify. I think that the average schoolchild has been taught that 'heat transfer is by conduction, radiation, and convection'? Perhaps not?Chjoaygame (talk) 19:04, 1 December 2025 (UTC)

definition of heat in physics in Wikipedia

Another edit that puts heat as a quantity of energy in transfer from one thermodynamic system to another is Heat: Difference between revisions - Wikipedia with the edit cover note "revert this misleading lede".

Some engineering textbooks (and, I seem to recall, some thermodynamics texts?) define heat as proposed in the edit.

Some texts regard convection as a mode of heat transfer, but most thermodynamics texts follow Maxwell and think of convection as a mode of transport of matter along with its internal energy, not as a mode of heat transfer. I don't have easy access to the 1978 edition of van Wylen (which is written from an engineering perspective) that is cited in the edit, but I do have access to its 2009 seventh edition, which uses the same heat definition and regards convection as a mode of heat transport/transfer because it depends upon temperature difference.

The edit proposes to change from the traditional Wikipedia thermodynamical definition which was developed over a decade or so, through extensive talk page debate and editorial consensus. It intended to make the definition suitable for a rigorously logical presentation of thermodynamics in Wikipedia. It was constructed with the following several ideas in mind.

The traditional Wikipedia definition was in terms of transfer of energy between a thermodynamic system and its surroundings. This differs from the edit's proposed definition because a thermodynamic system has a temperature, but its surroundings do so only if they also consist of another thermodynamic system that has a temperature. The source of thermal radiation from the surroundings is not required to possess a temperature, and is consequently not required to be thermodynamic system, because it is allowed to be far from thermodynamic equilibrium.

A reason for the traditional Wikipedia definition is to avoid possible circularity of definition. This entails that Wikipedia should state the first law without logical reliance on a prior statement of the second law, and without a prior definition of temperature, along with the idea that thermodynamics defines temperature, as Kelvin did, through the second law. An objection to this idea is that it is fine to make the statement of the first law depend logically on the statement of the second law and on the definition of temperature. Another objection to this idea is that, nowadays, 'temperature' is officially defined through what thermodynamics calls 'empirical temperature', not through the thermodynamic definition of temperature. Eventually, for rigorous logical consistency and validity, thermodynamics has to use the thermodynamic definition. The official empirical definition is practically close to the thermodynamic definition but it is not exactly the same.

The edit's proposed definition excludes friction as a source of heat. This is fine for the caloric theory of heat, but it hardly recognises that the caloric theory was abandoned in the first half of the nineteenth century largely because it came to be recognised that friction generates heat. This is particularly recognised in writings of Planck that have mostly not been translated into English.

Considering friction as a source of heat: The friction can be internal to the thermodynamic system of interest, as in the experiments of Mayer, and of Joule, that led Helmholtz in 1847 to enunciate his version of the principle of conservation of energy. Or the friction can be jointly between the system of interest and its surroundings, as in the 1798 cannon boring experiments of Count Rumford, or as in dragging a rough block over a rough surface; some of the heat generated will go into the thermodynamic system, and the rest into the surroundings. The first law separates these two quantities of energy through the notion of internal energy, which is an essential part of the first law. The internal energy of a thermodynamic system is defined through the concept of thermodynamic work, which is defined through the thermodynamic system of interest's state variables other than temperature and entropy. In some cases, thermodynamic work can be practically equated to ordinary physical work defined by processes external to the thermodynamic system.

The upshot is that the traditional Wikipedia definition was by exclusion of transfer of energy through thermodynamic work and through transfer of matter. This is perhaps a strained idea, but it has the advantage of strict logical validity for the presentation of thermodynamics: for a closed system, transfer of energy is either as heat or as thermodynamic work. So far as is obvious, the only modes of energy transfer that conform to this requirement for heat are thermal conduction, thermal radiation, and friction. Perhaps there are others?

The definition of a term is distinct from an explanation of it, and from examples of its use.

A prime relevant reference, for a closed system, is
F. Reif, Fundamentals of statistical and thermal physics, McGraw–Hill, New York, 1965, page 73:
"In short, (2 8-1) defines the quantity Q by the relation
                                            Q = ΔE − *W = ΔE + W                                     (2 8-2)
where W = − *W is the work done by the system. The relation (2 8-2) constitutes the general definition of the heat absorbed by a system. When the external parameters are kept fixed, (2 8-2) reduces, of course, to the definition already introduced in Sec. 2 • 6 for the case of purely thermal interaction. The relation (2 8-1) simply splits the total mean energy change into a part W due to mechanical interaction and a part Q due to thermal interaction. One of the fundamental aims of our study will be to gain a better understanding of the relationship between thermal and mechanical interactions. This is the reason for the name "thermodynamics" applied to the classical discipline dealing with such questions."

Another reference for a closed system is
H.B. Callen (1985), Thermodynamics and an Introduction to Thermostatistics, 2nd edition, John Wiley, New York, pages 19–20:
"The heat flux to a system in any process (at constant mole numbers) is simply the difference in internal energy between the final and initial states, diminished by the work done in that process."Chjoaygame (talk) 08:31, 24 November 2025 (UTC)

There is no "traditional Wikipedia thermodynamical definition which was developed over a decade". Wikipedia does not develop definitions or does not engage in any kind of other creative processes. Yet this has been the practice of few editors such as the OP who insist on confusing and widely entangled subject matters, which is totally unnecessary. Wikipedia follows established science and uses existing notable sources to present the facts.

The subject matter is not difficult, but editors here engage in confusing arguments and personal views.

To state it once more. Heat is described differently in the varied fields of applications and environments. The term heat transfer is a term of engineering, while physics uses a much stricter definition for just heat. In physics heat is always a transfer of energy. That's the reason for having articles for each terminology. The general public and its history has yet a different scope of usage. There is nothing wrong with explaining all, but it needs to be clear in every treatment which scope of usage is relevant or desired. kbrose (talk) 20:11, 26 November 2025 (UTC)

The essential question is not 'whether 'heat' or 'heat transfer' is the natural term, but rather 'what kind of transfer is heat'?

The two candidate kinds are:

• transfer of a conserved quantity
  

The kind that is supported by the new edit is 'transfer of a conserved quantity'. This is how calorimetry works. It proposes that 'heat is conserved because the heat gained by the colder body is equal to the heat lost by the hotter body'. Coordinate with this is the proposition is 'the work expended by the driver in the surroundings is equal to the thermodynamic work received by the system; in this sense, work is conserved'. These are historically supported suppositions. They are convincing for suitably isolated thermal conduction, through contact between the bodies. For radiative heat transfer, it is sometimes but not always possible to restrict the radiative loss of the emitting body to be equal to the radiative gain of the receiving body. But there are kinds of heat transfer that are not covered by these historically supported suppositions.

• transfer defined by its mechanism of process
  

Twentieth century reliable sources see things differently. In the middle of the nineteenth century thermodynamics distinguished heat from work in a systematic way. For example, Bryan (1907) and Bridgman (1941) analysed the effect of friction, as follows. Ordinary physical work can be reliably measured in the surroundings, without recourse to the state variables of the system. In contrast, thermodynamic work is measured by the state variables of the system other than temperature and entropy, excluding transfer of matter. The relevant changes in the state variables exclude those due to transfer of matter, because the associated energy cannot be split reliably into work and heat. Because of friction, the two kinds of work (ordinary physical and thermodynamic) in a process are not equal, so that "work" cannot be treated as a conserved quantity. For example, Bridgman (1941) wrote "the work received by the block from the pavement… is not equal to the work done on the pavement by the block." When friction intervenes, the process generates heat, which is consequently also not conserved. In physical terms, friction dissipates energy from ordinary physical work by generating heat.

The definition proposed in the new edit is that of the caloric theory, while the thermodynamic definition takes into account that the mechanism of heat transfer includes changes in the form of the energy in the transfer process. For a process with matter transfer excluded, the assumption that internal energy is a state variable effectively makes the first law of thermodynamics into a definition of heat. This mode of distinction between work and heat is central to the logic of thermodynamics, because it allows entropy to be defined consistently.Chjoaygame (talk) 05:50, 27 November 2025 (UTC)

evolution from the caloric theory into thermodynamics

In the middle of the nineteenth century, thermodynamics emerged by evolution from the caloric theory of heat.

The caloric theory was largely the work of two great physicist–chemists, Laplace and Lavoisier. It was based on thorough and careful experiments in calorimetry, heat being accurately conserved when it was measured by passing it by thermal conduction from a hotter body to a colder one. As defined by calorimetry, the heat lost by the hotter body was equal to that gained by the colder body. Conservation of heat was also accounted for in the light of the difference between latent heat, which was hidden from the thermometer, and sensible heat, which was evident to the thermometer, as elucidated by the accurate calorimetric measurements of another great physicist–chemist, Joseph Black. The caloric theory of the conservation of heat persisted into the first half of the nineteenth century, as supported by Sadi Carnot, whose heat-engine studies contributed much to the discovery of the second law of thermodynamics.

At the end of the eighteenth century, however, Benjamin Thompson, Count Rumford, in his cannon boring experiments, moved physics forward by showing that heat could be endlessly generated by friction. After all, heat was not conserved. In the first half of the nineteenth century, Robert von Mayer showed that heat could be generated by friction also in the stirring of a very viscous liquid. Near the middle of the nineteenth century, James Joule did more extensive and precisely accurate experiments on the production of heat by friction, in a liquid stirred by a paddle wheel, and in an electrical conductor, through the friction of the passage of an electrical current.

In the middle of the nineteenth century, the work of Helmholtz, Rankine, Clausius, and Kelvin created the new theory of thermodynamics.

The new theory created the idea that the internal energy of a body could be changed and measured purely through energy transfers that avoided thermal conduction, radiative transfer, and friction. On the other hand, thermal conduction transferred heat through a conductive medium, thermal radiation transferred heat without a conductive medium, and friction generated heat from externally supplied mechanical energy. The first law of thermodynamics was established on this basis. Calorimetry remained useful, but not necessary, for the estimation of internal energy. But the caloric theory was abandoned.

With the avoidance of thermal conduction, radiative transfer, and friction, the new theory determined the internal energy of a body purely through its ‘macroscopic’, or ‘external’ quantities or 'parameters', such as volume and electric polarisation. Preventing microscopic energy transfers to a body leaves the only transfers as the macroscopic ones, of thermodynamic work, defined by the external quantities, and of matter with its associated energy.

Thermal conduction, radiative transfer, and friction, are ‘microscopic’ mechanisms. Temperature is a purely ‘internal’, ‘microscopic’, or ‘intensive’ property of a body. It has a thermodynamically conjugate ‘extensive’ property, entropy. Chjoaygame (talk) 03:31, 25 November 2025 (UTC)

edit history of Wikipedia article on Heat

The first version of the Wikipedia article contained the following:

"Conduction is the most common means of heat transfer in a solid. On a microscopic scale, conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighboring atoms and molecules, transfering some of their energy (heat) to these neighboring atoms.
"Convection is usually the dominant form of heat transfer in liquids and gases. In convection, heat transfer occurs by the movement of hot or cold portions of the fluid. For example, when water is heated on a stove, hot water from the bottom of the pan rises, heating the water at the top of the pan. Two types of convection are commonly distinguished, free convection, in which gravity and buoyancy forces drive the fluid movement, and forced convection, where a fan, stirrer, or other means is used to move the fluid.
"Radiation is the final means of heat transfer. Radiative heat transfer is the only form of heat transfer that can occur in the absense of any form of material and as such is the only means of heat transfer through a vacuum. Thermal radiation is a direct result of the movements of atoms and molecules in a material. Since these atoms and molecules are composed of charged particles (protons and electrons), their movements result in the emission of electromagnetic radiation, which carries energy away from the surface. At the same time, the surface is constantly bombarded by radiation from the surroundings, resulting in the transfer of energy to the surface. Since the amount of emitted radiation increases with increasing temperature, a net transfer of energy from higher temperatures to lower temperatures results."

The revised lead read:
“Heat is related to energy in a similar fashion to how work is related to energy. Heat is said to flow from areas of high Temperature to areas of low temperature. Essentially, all objects have a certain amount of energy within them that is related to the random motion of their atoms. This internal energy is directly proportional to the temperature of the object. When two bodies of different temperature come in to thermal contact, they will exchange internal energy until the temperature is equalized. The amount of energy transfered is the amount of heat exchanged. It is a common misconception to confuse heat with internal energy, but there is a difference, and understanding the difference is a necessary part of understanding the First law of thermodynamics.”

I can’t date that oldest version for sure: perhaps it was 22:48, 8 August 2001? I got it by searching for the first revision to it, dated 15:43, 25 February 2002.

We may note: the reference to the first law involving internal energy, without explicit mention of the second law, but with extensive reference to temperature; the assumption of conservation of heat in the transfer; no mention of the nineteenth century abandonment of the caloric theory; no mention of the Bryan (1907) – Caratheodory (1909) revolution in thermodynamical theory, to a 'mechanical' theory of heat. Chjoaygame (talk) 12:53, 1 December 2025 (UTC)

@Chjoaygame: See my subsequent import of old edits to this page; the first revision is now this one on 7 August 2001 (UTC). Graham87 (talk) 13:04, 1 April 2026 (UTC)

At 15:19, 25 May 2004, the following was added as the first sentence of the lead:
"Heat (abbreviated q, also called heat change) is the transfer of thermal energy between two bodies which are at different temperatures. The SI unit for heat is the joule."
This is a loose statement that heat, called 'thermal energy', is conserved in a transfer between two bodies at different temperatures, the fundamental principle of calorimetry.

At 10:41, 25 August 2004, the following was added as the last sentence of the lead:
"Infrared radiation is often linked to heat, since objects at room temperature or above will emit radiation mostly concentrated in the mid-infrared band (see black body)."
Thus the lead explicitly mentioned thermal radiation.

At 10:39, 17 February 2005, convection was removed from the list of heat transfer mechanisms. At 14:09, 17 February 2005, that removal was undone.

At 08:42, 25 January 2006, generation of heat was added to the lead: "electromagnetic dissipation (as in electric stoves,) or mechanical dissipation (such as friction.)"Chjoaygame (talk) 13:55, 2 December 2025 (UTC)

definition by exclusion of thermodynamic work

At 18:14, 10 August 2009, the edit https://en.wikipedia.org/w/index.php?title=Heat&diff=prev&oldid=307207471 , with the credit cover note "I made some statements more rigorous. I used the definitions given in the book by F. Reif", introduced the definition of heat by splitting transfer of energy, to or from a closed system, into thermodynamic work and heat:

In physics and thermodynamics, heat is the process of energy transfer from one body or system due to thermal contact, which in turn is defined as an energy transfer to a body in any other way than due to Work (thermodynamics) performed on the body.

Thermodynamic work is distinct from ordinary physical work in that thermodynamic work is defined by the changes only in the thermodynamic system's state variables disregarding the characteristic thermodynamic conjugate variables entropy and temperature. Ordinary physical work is defined by macroscopic variables in the surroundings; this does not take into account that some of it is dissipated by friction, converting it into heat, which may pass to the surroundings or to the thermodynamic system. This is the underlying physics of the first law of thermodynamics, setting things up for the second law and the definition of entropyChjoaygame (talk) 13:59, 5 January 2026 (UTC)

At 17:39, 11 April 2012, the key point of the just foregoing definition still stood at the head of the lead, appearing with more references. Most regrettably, however, at 10:30, 15 April 2012, by this edit https://en.wikipedia.org/w/index.php?title=Heat&diff=next&oldid=486852969, it was demoted by yours truly to appear only as a sort of conclusion to a long section of the article that overviewed various definitions, as follows:

Heat transfer as a residual quantity

Heat transfer as a residual quantity is a concept of theoretical character.[19] There are five main elements of the underlying theory.

• The existence of adiabatic enclosures and walls.
• The existence of states of thermodynamic equilibrium.
• The universality of the law of conservation of energy.[19]
• The universal irreversibility of natural processes.[20]
• The recognition of work as a form of energy transfer.

From these five elements is theoretically distilled an idea of heat as a form of energy transfer other than by work. Also theoretically distilled from them is the idea of absolute or thermodynamic temperature. From here it is deduced that heat transfer is related to temperature differences.[20][21][22][23][24]

I can only apologise and say that I am sorry because this demotion led to the following: at 21:33, 21 April 2012, by this edit https://en.wikipedia.org/w/index.php?title=Heat&diff=next&oldid=488504036, the section that stated the definition of heat transfer as a residual quantity was removed.Chjoaygame (talk) 06:29, 6 January 2026 (UTC)

It is quite ridiculous that you are analyzing edits from twenty three ago. My eyes glazed over when I realised.

Could you define whatever the hell your problem is in say Three sentences, with diffs? Please? Walter Ego 11:00, 7 January 2026 (UTC)

Thank you, Editor Walter Ego, for your response. I am talking on the Talk page in order to avoid edit dispute.

The problem is that an engineering notion has taken over the lead of the article, to the practical exclusion of thermodynamic thinking.

Often, engineers are happy with eighteenth century caloric theory thinking, defining heat simply by calorimetry: this is covered in the article Heat transfer. For this present article, am trying to take into account the fall of the caloric theory of heat around 1798 to 1850, and its replacement by the mechanical theory.

Thermodynamic thinking of the twentieth century defines heat by exclusion: For a system for which transfer of matter is prevented, transfer of energy as heat is defined by the first law of thermodynamics, as follows: transfer of energy is either as heat or as thermodynamic work; change of internal energy that is not due to thermodynamic work is defined as energy transferred as heat.Chjoaygame (talk) 12:11, 7 January 2026 (UTC)

Thank you for trying to help me, but unfortunately I am still none the wiser. I'm pretty convinced that this is due to my own lack of understanding of the subject though.

At the moment, because the problem is so ill defined, I will not be making any changes to the article, and I cannot see anywhere you have tried to propose specific changes to the article; I doubt changes will be made. - Walter Ego 14:16, 7 January 2026 (UTC)

Thank you for your thoughts.Chjoaygame (talk) 14:25, 7 January 2026 (UTC)

Edit that corrects thermodynamical definition of heat

I have again edited in the correct thermodynamical definition of heat, in this edit https://en.wikipedia.org/w/index.php?title=Heat&diff=1354635829&oldid=1354629176 .

This is to express thermodynamics in a logical development. In the SI, temperature is defined in microscopic terms, in statistical mechanics, but thermodynamics is a macroscopic theory. In thermodynamics, temperature is defined in macroscopic terms, based on the prior definition of heat. Thus, circular definition is avoided.

The eventual liberation of thermodynamics from the 18th century caloric theory is described in the history section of the article. It was settled in the early 20th century, particularly with the work of Bryan, Born, and Carathéodory.

The engineering topic of heat transfer sometimes prefers to retain the caloric theory definition, but this article is about the thermodynamic approach, through the mechanical theory. Chjoaygame (talk) 14:38, 17 May 2026 (UTC)