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Definition of heat in physics

Thermodynamicists are a peculiar breed, and if they use a definition of heat different and more narrow than anybody else's, that's fine, but it shouldn't be the primary one.

So far as I can tell, the definition of heat in physics is transfer of energy from one system to another due to a temperature difference, period. This obviously includes transfer to heat as radiant heat. I reject the idea that although "thermal radiation" is heat transfer, that in this peculiar case "heat transfer" is not literally "transfer of heat." Yes, I know Wikipedia actually says that, but it also gives no citation and I don't believe it. This emperor has no clothes.

The SI system of units [1] gives "heat flux density" as a synonym of "irradiance." Apparently SI thinks that irradiance involves heat flux, which is very puzzling if physical contact is necessary for heat flux to occur. Perhaps SI means "irradiance" without any kind of radiation?? Or perhaps they mean that in the case of heat flux counted as irradiance, there is heat flux without a literal flux of heat? I'm sorry, but again this is a bit much to swallow.

Meanwhile NIST calibrates "heat flux sensors" with blackbody radiation. [2]. I don't see any notation that the NIST standards are for engineers-only, and that physicists should avert their eyes, since this is not for them. NIST, after all, is using SI language, and SI is standarization body for physicists.

So here's the deal, Kbrose. If you want to make these changes to this article for "physics," let's see your physics references and cites.

And while you're at it, you might give one for the your implied idea that thermal contact is the same as physical contact. Are Earth and Sun in "thermal contact," or not? SBHarris 19:28, 12 December 2011 (UTC)

The definition of heat doesn't invoke temperature, that would be putting the horse behind the cart. Temperature is only defined when very, very, very, very, special conditions are met, i.e. thermal equilibrium. And if you consider a process involving heat flow, you'll see that this necessarily involves a departure of thermal equilibrium. Not just the fact that the two bodies exchanging heat are not in mutual thermal equilibrium, but that the bodies themselves are not in thermal equilibrium. In practice the way one can deal with this is to consider process where heat is exchanged so slowly that thermal equilibrium is still approximately true. Books that focus on the theoretical side of these issues will make rigorous statements, by introducing the concept of a quasistatic process. So, you consider the limit where the heat flow tends to zero, but you also increase the time span so that it tends to infinity, such that the total heat being exchanged can be finite.

So, there is a fundamental contradiction between having a finite heat flow per unit time and being able to define a temperature rigorously. That's why the definition of heat should not invoke temperature. Count Iblis (talk) 22:30, 12 December 2011 (UTC)

I feel uncomfortable most times I read the phrase 'thermal equilibrium'. It is perhaps possible to use that phrase with safety and precision, but mostly for basic theoretical work I think it safer to refer to thermodynamic equilibrium, unless there is a special reason not to do so.Chjoaygame (talk) 00:28, 13 December 2011 (UTC)

Heat is a word of ordinary language, as well as being a term of scientific art. For example, according to the Oxford English Dictionary, in 1665, Robert Hooke wrote "A Thermometer, thus marked and prepared, will be the fittest Instrument to make a Standard of heat and cold." I see no obvious reason to deny that Hooke was using ordinary English when he wrote that. From the same source, in 1794 J. Hutton wrote "When we approach the fire, our sense informs us in a particular manner; and this we name heat, which is then purely a sensation." This seems again like a usage of ordinary language. The English ordinary language word heat comes from older European sources, but does not seem to have been traced right back to an Indo-European source, according to Pokorny.Chjoaygame (talk) 00:45, 13 December 2011 (UTC)

Thinking of the word heat as a term of art, Count Iblis is surely right that temperature rigorously defined refers to thermodynamic equilibrium which entails zero flow of everything, while flow of heat refers to a non-zero flow. On the other hand, one may contemplate two bodies in their respectively separately isolated thermodynamic equilibria, each with its own temperature, then 'connected thermally' so as to produce a new isolated body, which may be envisaged to come eventually to its own isolated thermodynamic equilibrium.

What does this phrase 'connected thermally' mean? Kbrose seems to be of the view that it means only conductive connection, as I read him. SBHarris disagrees, and thinks that heat transfer includes thermal radiation.

According to some, as noted in another Wikipedia article there is a weakness in many thermodynamic discussions, that they do not mention radiative heat transfer. An example would be Planck's Treatise on Thermodynamics, edition of 1917. But it would be hard to argue that Planck did not know of the concept of thermal radiation, considering for example the title of his monograph Vorlesungen über die Theorie der Wärmstrahlung, Leipzig, 1906, giving his views on his law of black-body radiation.

Would two bodies separated by near-enough a vacuum be considered to be in 'thermal connection"? Pierre Prevost would say so. In 1791, he described experiments with two spherical mirrors located some distance apart, with two bodies so placed at the optical foci that radiation from each body is focused on the other. He referred to radiation of free heat between the bodies. He worked within the then current paradigm of heat as a conserved subtle fluid called 'caloric', which distinguished free heat, in two forms, 'sensible' and 'latent', and (chemically) 'combined' heat. He distinguished radiant from non-radiant heat ("le feu rayonnant" versus "le feu non rayonnant"), the latter creeping along an iron rod that sometimes joined his two focally placed bodies. For Prevost, radiant heat consisted of very fine particles, so fine that they practically never collided, but travelled practically instantaneously in straight lines obeying an inverse square law of density, like light. In the half century after this article, the caloric theory of heat was gradually demolished.

Thermal radiation, according to Planck, has the same temperature in each of its constituent wavelength components, of which there is a broad and nearly continuous spectrum. Light from a gas discharge tube or from a laser does not have the same temperature, as defined by Planck, at every wavelength of a nearly continuous spectrum. For these wavelength-specific kinds of light, the spectrum is far from being broad and nearly continuous, and they are not regarded as thermal radiation. Whether light reaching a body is considered as heat or work depends on how the problem is formulated. One should distinguish whether one is considering the thermodynamic state to be specified by the conditions within the body, or by external conditions that determine what enters and leaves it; each of these two methods has been used at times, and each is valid if properly stated (see for example Gislason, E.A, Craig, N.C. (2005), Cementing the foundations of thermodynamics: Comparison of system-based and surroundings-based definitions of work and heat, J. Chem. Thermodynamics 37: 954–966). If the receiving body includes a device that can use the narrow spectrum of gas-discharge or laser light more efficiently than merely thermally, and the problem is stated in terms of the conditions within the body, then the light can be considered at least partly as work supplied. But if the wavelength-specific devices are not referred to, or are known to be absent, then it may perhaps be argued or debated or denied that the light is received only as heat.Chjoaygame (talk) 02:02, 13 December 2011 (UTC)

Thermal radiation indeed acts like a photon gas with the temperature of its radiating body. Most common and physics usages consider such radiation with a blackbody spectrum, if it is carrying net energy from one location to another, over time, as a type of heat. Temperature is usually used to define "heat" because without the concept of temperature, heat would be no different from any other kind of internal energy. However, what makes heat a special kind of energy is that it is subject to demands of temperature gradients, ala Fourier's law and without these gradients the heat flow goes to zero. Thermal energy may remain, but it no longer flows, hence no heat flow.

And yes, while it is quite true that strictly speaking temperature needs equilibrium conditions to be defined, in the limit of small thermal energy flux one can define a temperature "well enough." Thus, the heat equation, which defines a temperature field as "temperature" of points in space, evolving in time: T (x,y,z,t) even as heat (thermal energy) continues to flow in systems. Of course, these points are not geometric points, but if you stand back, they represent parcels of matter large enough each to have its own equilibrium over a (small) volume of space, and through a (small) snapshot in time. SBHarris 07:28, 13 December 2011 (UTC)

In thermodynamics, one prefers to think in terms of transfer of energy as heat, or in terms of a process of heating, rather than of heat as a kind of internal energy or a kind of energy. The latter conceptions cannot be consistently maintained with a definite meaning. Generally speaking there are no kinds of internal energy; internal energy is a concept in its own right. In many cases, thermal radiation propagates in rays like light, at the speed of light, according to an inverse square law, and only in special circumstances is it conveniently likened to a gas. Many processes in physics do not admit uniquely defined temperature at points of space. Thermodynamics has its limitations, and has difficulty in describing processes far from thermodynamic equilibrium. How to define heat transfer far from thermodynamic equilibrium is often not too obvious.Chjoaygame (talk) 10:20, 13 December 2011 (UTC)

Chjoaygame, if you think that that 'energy tranfer' can be equated with heat then you will surely have problems editing in thermodynamic matters. Heat is the kinetic energy of particles, that is why it is related to temperature by the Botltzmann constant. The idea that 'heat' somehow is 'energy in motion'is a hangover from caloric theory. Caloric theory is still widely believed and keeps re-emerging as 'heat flow'. The definition of caloric, just like 'the aether', changes to follow the twists and turns in the arguments of the aficionados for its existence. For example, look at the woderfully circular definition of 'Heat' here in Wikipedia where it says (first line) 'heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact'. Now check 'Thermal contact where it opens by saying 'a thermodynamic system is said to be in thermal contact with another system if it can exchange energy with it through the process of heat.' Get the picture? In fact in solid and liquids the conduction of heat by is by the coupling of phonons through the interatomic forces comprising the various bonds between atoms and molecules - there is no 'flowing' going on at all! In gases, thermal energy (heat) is transferred by the random collision process(es) between the atoms and molecules that is responsible for the exchange of energy (more accurately, momentum), that is why gases are such terrible conductors of heat. What causes a lot of confusion is the existence of flow processes like convection that move hot material about but these are 'bulk' or macroscopic processes wheras heat is a microscopic or molecular (atomic) effect, this seems to be the justification for 'heat flow'.

Further, radiation 'propagates in rays like light' is just as out of date as caloric because it gives no explanation for the emission and absorption of 'light energy' or more accurately photons. Trying to explain the absorption/emission of photons using wave equations is hopeless, the maths just cannot be made to fit the facts. (Of course the modern approach is to make the facts fit the maths - it is a lot easier to be a 'scientist' that way! --Damorbel (talk) 12:57, 13 December 2011 (UTC)

When I said "any other kind of internal energy" I really meant "any other contributor to internal energy." Obviously there are other contributors to an object's internal energy-- these all remain when you've sucked all the thermal energy out of the object, and have it at absolute zero temperature (or as close to that as you like to, or need to, get).

In the same way, there are many ways of changing an object's internal energy other than to transfer heat to it. The fact that some of these ways "heat" the object (change its thermal energy) should not fool us into thinking that they are "heat" For example, pounding on the object with a hammer (or hitting it with alpha particles) may heat it. Or stretching it may heat it, like a rubber band or the interior or Jupiter's moon Io. But none of these operations transfers energy as heat. Even shining a laser on a object "heats" it (increases its thermal energy), without a laser beam itself being "heat," any more than a beam of alpha particles is. What makes these types of energy different is that they do not necessarily have to heat the object, but could be potentially harnessed as energy stored, and no heat generated at all. For example, some objects or systems store mechanical work without heating up (not like a rubber band, but more like raising an object to a height). Heat cannot be stored as potential in that way, unless the TS entropy cost of it is paid in some other way; but there is no entropy cost with other types of energy (even though they are all measured in "joules"), so they are all potentially useable as free energy.

There's a good reason thermodynamicists split out heating from other ways of increasing internal energy, and that is that only heat MUST increase an object's entropy. Other forms of work can increase an object's entropy, but they are not required to do so. The fact that a bit of heat is always associated with a certain amount of entropy change TdS not only defines heat, but it tells us why the heat flows, and why it can't go the other way (second law).

$dU=\delta Q+\delta W\ =T\mathrm {d} S\ +\delta W\,$

The Gibbs equation which tells how the Gibbs free energy of a system changes as we do various things to it, is clear about the differing nature of the TdS term:

$\mathrm {d} G=V\,\mathrm {d} p-S\,\mathrm {d} T+\sum _{i=1}^{I}\mu _{i}\,\mathrm {d} N_{i}\,$

Note from the above that you can increase free energy in a system (the work that the system can return back to you) by increasing its chemical potential (like charging a battery or fueling a car) or by doing PdV work on it (which can be stored). But that TdS term is negative and so it works against you, decreasing the work available if dS is positive in the changes you make by adding PdV or chemical potential. And of course, if you heat the system, ALL the internal energy change is TdS type, and the free energy changes not at all. Heating a system generally increases its internal energy but does not increase its free energy. That anergy is "degraded", which is at the core of all energy transfered by heat-- heat energy dQ cannot be converted to other types of energy unless some other way is found for paying the TdS entropy cost that comes with it. Work and laser beams aren't like that. Blackbody radiation, however, IS like that-- it has a temperature, and thus a minimal TdS entropy change cost for every bit of heat it delivers (not the case with other types of radiation, which have no TdS cost, and might as well be pure work). SBHarris 21:29, 13 December 2011 (UTC)

But all we have is matter and motion, plus a storage facility for potential "work". So if you want to get rid of something and conserve your matter, which you say can be converted into motion, then you have to get rid of the fastest possible motion of the smallest particles that you can create to get rid of. And the heating value of what you're getting rid of is related to its kinetic energy (matter x motion squared). But the rate at which you can get rid of it seems to increase as the square of the energy content value and the 4th power of the absolute temperature.WFPM (talk) 18:34, 19 March 2012 (UTC)

In the case of a star, the Gibbs energy content equation leaves out the stored atomic fusion energy supply that can keep the star radiating at a constant temperature (and entropy)for maybe another 5 Billion years. but in the end the temperature will go down by depletion into a lower temperature radiating process and a resulting increase in the entropy of the system. And I don't see what that process has to do with the exchange of energy with anything other than with its surrounding environment. And so 2 separate masses both give off heat radiation, and a different portion of that heat amount for each one happens to impact the other one. What does that matter? It's not really an exchange of heat process but rather an accounting process. But I guess the formulas are necessary for the purposes of the calculus of thermodynamic processes.

propose to delete paragraph of non-notable opinion

On the grounds that it is not notable, and is potentially misleading, I would like to delete the following paragraph from the section Heat#semantic misconceptions;

In a 2004 lecture, Friedrich Herrmann opined that the confusion may result from the modern practice of defining heat in terms of energy, which is at odds both with the historic scientific definitions and with the modern lay concept of heat. He argues that the quantity heat as introduced by Joseph Black in the 18th century, and as used extensively by Sadi Carnot, was in fact what is today known as entropy-- something possessed by a substance in amounts related to that substance's temperature and mass, which exits one substance and enters another in the presence of a temperature gradient and can be created in many ways but never destroyed. He further argues that the layperson's concept of heat is essentially this entropy concept, and so in redefining heat to refer to an energy concept, modern science creates an unnecessarily awkward and confusing presentation of thermal physics. Herrmann's opinions about heat and entropy are hardly supported by other writers.

Reading the article by Herrmann, I am not impressed that it contains notable information for the present context. I would like to delete the paragraph about it.Chjoaygame (talk) 03:15, 26 December 2011 (UTC)

I agree with the proposal to delete that paragraph. Cardamon (talk) 07:58, 27 December 2011 (UTC)

I have removed that paragraph, and changed the title of the section to "Semantics", which seems more neutral. Cardamon (talk) 01:33, 5 January 2012 (UTC)

technical versus ordinary language

Editor 64.234.48.159 removed from the lead the sentence "In ordinary language, as distinct from technical language, heat has a broader meaning. This can lead to confusion if the diversity of usage of words is forgotten." I have reverted his edit.

My reason is that part of the article, and in particular part of the lead, is about mistakes that can arise from confusion when the diversity of usage of words is forgotten. This was a re-wording of a similar concern previously expressed in terms of "lay" language versus various technical languages, and is a proper concern of the article. Even within the techical realm, the meaning of the word heat needs careful attention, and it is proper for the article to say so.Chjoaygame (talk) 02:21, 4 January 2012 (UTC)

I'm all for giving the meaning careful treatment, but if you want to include statements about usage and confusion, those would at least need good sources. Dicklyon (talk) 02:56, 4 January 2012 (UTC)

What is needed is a simple rename of this article to heat (physics) or heat (thermodynamics), very much as we've had to do with work and energy. Indeed, there are both work (physics) AND work (thermodynamics) articles, as well as many others for other types of work in the language; if you search for work, then work (physics) is the primary direct, with a dab page. I see no reason why a similar solution can't be the same for heat. Heat already (after all) has a dab page that lists thermal energy. That dab page probably also needs to list the colloquial use of heat to mean temperature, as in: "I can't stand Florida since I can't stand heat.." SBHarris 04:35, 4 January 2012 (UTC)

Call for article rename to heat (thermodynamics)

I propose this article be renamed "heat (thermodynamics)" and that "heat" be redirected to it (instead, right now it's the other way around, and heat (thermodynamics) redirects to heat!) The other popular/colloquial uses of the word "heat" in English (as a synonym for temperature, for example) can be reduced to entries to the heat (disambiguation) page. There is already an article for the semi-technical (and older) use of heat that includes thermal energy (as in "heat content"), and that is on the dab page already.

What say you all?

So:

RENAME

1. I vote this article be renamed heat (thermodynamics) (or heat (physics)) and be the primary direct for the search term "heat" in Wikipedia. Alternately, the search term "heat" may be made to direct to the heat (disambiguation) page, if many concerned editors don't like the thermodynamic definition being the primary one for "heat." Either solution is okay by me. Both solutions avoid the problem that the article about the technical thermodynamic definition is merely called "heat" intead of the more descriptive heat (thermodynamics). Again, the analogy for all this is work (physics). SBHarris 00:38, 7 January 2012 (UTC)
2. I would prefer that it be renamed 'Heat (physics)'. Calorimetry stands on its own feet and is a valid part of physics, senior to thermodynamics in history, and does not depend on thermodynamics. True, thermodynamics gives most important understanding of calorimetry, but this is a relation between parts of physics. Calorimetry is not just a subset of thermodynamics; it is a part of physics and is a main source of empirical data for present-day thermochemistry.Chjoaygame (talk) 01:44, 7 January 2012 (UTC)

Heat (physics) is also okay with me. SBHarris 01:49, 7 January 2012 (UTC)

Definition of heat used throughout wiki does not conform to the useage by earlier scientists

Until recently heat was kinetic atomic vibrations

The wiki version is enormously confusing for anybody educated from the writing of the classical scientists who worked out what Heat was and went on to develop things like the nuclear reactor.[This comment was posted by editor Andrewedwardjudd at 13:29, 13 March 2012 but he forgot to sign it by the four tilde method.Chjoaygame (talk) 00:24, 14 March 2012 (UTC)]

• People like Count Rumford in 1798 argued against the implausibility that matter contained a substance called caloric. He said that heat was matter in motion. The idea was already fairly well argued but he just did some convincing demonstrations of unlimited amounts of heat being generated by friction. Maxwell himself said that heat was molecular vibrations. In the preface of the 1871 theory of heat he says

The last chaper is devoted to the explanation of various phenomena by means of the hypothesis that bodies consist of molecules, the motion of which constitutes the heat of those bodies

• Joule said of sensible heat, when referring to both latent and sensible heat, where living force was the term used to describe kinetic energy, "Heat must therefore consist of either living force or of attraction through space. In the former case we can conceive the constituent particles of heated bodies to be, either in whole or in part, in a state of motion
• R Clausius said in On the moving force of heat, and the laws regarding the nature of Heat itself which are deducible therefrom July 1851

It may be remarked further, that many facts have lately transpired which tend to overthrow the hypothesis that heat is itself a body, and to prove that it consists in a motion of the ultimate particles of bodies

• Lord Kelvin said when describing the Kelvin version of the second law of thermo in A dynamical theory of heat 1851 said the dynamical theory of heat was previously established by Sir Humphrey Davy in 1799 who concluded that Heat consists of a motion excited among the particles of bodies
• John Tyndal wrote Heat as a mode of motion in 1868
• The current wiki version of reality is just odd.
• Who made the decision to rewrite history and not tell anybody about it???

Andrewedwardjudd (talk) 15:05, 14 March 2012 (UTC)andrewedwardjudd

• Heat has never been kinetic atomic vibrations. In the past it has, however, included static "thermal energy" (heat "content"), which consists of any kinetic and potential atomic vibrational energy that exceeds the zero-point energy. But yes, you're right that it's confusing that this article uses only the strict thermodynamic definition of heat, and not the wider one which equates it with thermal energy in a system, even when it is not being transferred anywhere. Some possible solutions for this have been discussed above. One is a separate heat (thermodynamics) article which is short, and sets out the very limited thermodynamic notion of energy TRANSFER. The article on heat (physics) could be longer and also contain the idea of heat as thermal energy (even if static thermal energy content, and not thermal energy in transfer or transit). SBHarris 23:48, 13 March 2012 (UTC)

• The unsigned comment by Andrewedwardjudd starts "Until recently heat was kinetic atomic vibrations." The unsigned comment is itself confused; this much is apparent in that the first response to it was to deny it: "Heat has never been kinetic atomic vibrations."

The author of the comment has not sufficiently studied the history that he claims to be relying upon. Heat is studied in macroscopic thermodynamics and in statistical mechanics. Thermodynamics deliberately and advisedly ignores the atomic or molecular constitution of materials and bodies, while statistical mechanics is built on ideas of atomic and molecular constitution. One of the merits of thermodynamics is precisely this, that it does not depend on hypotheses about atoms and molecules. Contrary to the confused ideas of the author of the comment, but as considered by classical authors, heat is primarily a macroscopic thermodynamic concept, not a microscopic one. The microscopic ideas explain and are derived or based on the macroscopic concept but do not supplant or obsolete it.

The confusion of which the author of the comment complains, and which is manifest in his comment, has been long discussed and clarified by the very classical authors whom he seems to refer to and by whose writing he claims to have been educated, but whom he seems not to have studied carefully. They make clear the distinction between macroscopic and microscopic approaches. To judge from his comment, it seems likely that he has been educated by reading textbooks which think they are very "modern and clever and sophisticated" by not making that distinction clear enough.

The present Wikipedia article on heat is intended to carefully follow the definitions preferred by the classical authors, but apparently not accepted by the author of the comment. The author of the comment states that such definitions are used throughout Wikipedia. If that is so, it is a good thing, and he might like to think about why it is so.Chjoaygame (talk) 00:58, 14 March 2012 (UTC)

• If you search for Heat (disambiguation) you will find under the heading 'Physics' the explanation "the sum of a body's latent and sensible forms of energy (sometimes confused with "heat")". In its efforts to 'disambiguate' the section 'Heat (physics)' links to Thermal energy which is quite incorrect; heat is an intensive property measured by temperature, it is at the root of the 2nd law of thermodynamics; thermal energy is an extensive property measured in Joules - related to heat but not the same.This is clearly confused and in real need of 'disambiguation'. --Damorbel (talk) 07:17, 14 March 2012 (UTC)

Heat is not, and has never been, "measured by temperature." They are two different things, something we've all tried to explain to you, Damorbel, but you've never seemed to understand. YOu can add heat to melting ice and never change the temperature at all. SBHarris 17:57, 14 March 2012 (UTC)

You write "Heat is not, and has never been, "measured by temperature."" Which leaves the question - just what does 'temperature' measure?

Temperature measures the mean kinetic energy of particles. But particles with the same kinetic energy can have very different potential energies, as we see in the case of water at the triple point at 0 K, which is gas, liquid, and solid, all at the same temperature. The heat contents of the gas and solid (per mole of atoms or molecules) are quite different in such circumstances, even though the kinetic energies (and temperatures) of the molecules are equal. SBHarris 20:30, 14 March 2012 (UTC)

I understand 0K is the temperature where all atomic motion ceases i.e. where the kinetic energy is zero. From this we deduce that, if a first group of atoms has more energy than a second, otherwise identicle group, the first will have a higher temperature than the second i.e. the first group will be hotter than the second, it will have more heat and, because the groups are otherwise identicle, the first group will have more energy than the second. But this last condition does not apply if the first group is smaller than the second; in this case the two groups may have equal energy but different temperatures i.e. the first group 'has more heat' than the second because it is at a higher temperature (than the second). If the two groups are brought into thermal contact the first group will lose heat to the second and its temperature will fall; similarly the temperature of the second group will rise so its heat will increase. Is there a problem with this? --Damorbel (talk) 19:17, 14 March 2012 (UTC)

Yes, it is wrong. At 0 K, solids still contain zero-point energy and their atoms are not still. Motion cannot cease for quantum reasons. Temperature and heat are related by heat capacity and only temperature will deterimine which direction heat will flow. It may will to an object with more heat content if its temperature is lower. Also, again due to latent heat, one can add heat to a system and see no change in temperature. Rather, one phase changes to another.SBHarris 20:30, 14 March 2012 (UTC)

kinetic atomic vibrations

Sbharris, you write above - "Heat has never been kinetic atomic vibrations." I'd like to see some justification for this argument. That heat is a vibration of one sort or another goes back to Daniel Bernoulli (1700 - 1782) and developed slowly, partly because of the absence of a satisfactory atomic theory, to present day Thermodynamics,Statistical mechanics etc. I am curious to know what is it about Kinetic theory you find that excludes its explanation connecting atomic vibrations to heat. --Damorbel (talk) 09:51, 14 March 2012 (UTC)

Kinetic energy is not potential energy, and at least half of the thermal energy in a solid is potential energy. ALL of the "latent heat" of phase change is potential, not kinetic energy. You can read the article on heat capacity if you don't get this.

As for this article, it has some serious problems with circular definitions up front (at worst) and definition-by-exclusion at best. We're told thermal energy is any energy that isn't thermodynamic work. Then if you look up thermodynamic work, you're told it's any energy added to a system that isn't heat! LOL. You want to try that again? SBHarris 17:41, 14 March 2012 (UTC)

Sbharris, you are mixing a few ideas up. If you measure the global temperature of a well mixed ice bath that is not the same thing as the local temperatures produced when heat is added to that ice bath. You cannot possibly perfectly mix an ice bath while you heat it. Even an infintesimal addition of heat will act on the ice bath in a way that causes the ice bonds to be arranged differently and because they are arranged differently there will be an infintesimal temperature difference at that point only

And as you know latent heat is another name for hidden heat. But it not actual heat this moment. Neither is the combustion heat of petrol actual heat. Until some point fairly recently, actual heat in a substance has always been viewed in the modern theory as vibrations of the matter itself. Presumably you have already seen the large number of quotations from the likes of Humphrey Davy, Maxwell, Joule, Kelvin, Clausius and so forth that say your viewpoint of ""Heat has never been kinetic atomic vibrations." is not shared by the classical creators of the theory of heat. Andrewedwardjudd (talk) 18:15, 14 March 2012 (UTC)andrewedwardjudd

No, you're the one mixed up. Temperature is not determined by "ice bonds" but by average kinetic energy. You can always wait for a mixture to equilibrate after you add some heat, and if you do, you will find that in in a phase mix, after this equilibration, the temperature of the system does not change between before and after the heat is added, only the amounts of liquid, solid and gas change. For example, if you have a sealed system of water at the triple point (gas, liquid, solid 0 C), you can add heat to any of these three, and after a while you will see that you have not succeeded in changing the temperature of the whole system, which remains at 0 C. Rather, you just change the amounts of ice, water, and vapor. Latent heat is not "hidden heat" unless you expect all heat to show up as a temperature change. But that's as naive as saying that your computer is "hiding" its parts just because you can't see them all at every moment. Not all heat causes a temperature change. Latent heat is not hiding, and it certainly is real (and available for extraction from a three-phase system any time you'd like, without temp change, so long as three phases remain). SBHarris 20:30, 14 March 2012 (UTC)

Sbharris, Telling me i am wrong does not make you correct. I tried to explain why you are wrong and you are agreeing when the heat is added there are local temperture changes. Joule described latent heat as a distancing of molecules with forces acting over greater distances. Clearly it is true that according to Joule that if local molecular bonds change so that ice changes to water locally this is the same thing as a local temperature change or change in the amount of sensible heat and latent heat, where sensible heat is molecules in motion. As for your comment about absolute zero, that does not sound right to me because thermal energy is what used to be known as heat so you seem to be arguing there is thermal energy present at absolute Zero. Enrico Fermi did not agree back in 1952 that there was atomic movement at absolute zero.

what is the problem in explaining why the definition of heat has changed if there is thermal motion of atoms at absolute zero if that is the case?

You said this earlier.

"we've all tried to explain to you, Damorbel, but you've never seemed to understand. YOu can add heat to melting ice and never change the temperature at all. "

Thats an extremely patronising comment considering you know he was right that there is a temperature change when heat is added to the system and you need to wait "a while"

Your argument seems to be founded on the past not existing as it existed, and you are arguing this with considerable force. Why??Andrewedwardjudd (talk) 20:48, 14 March 2012 (UTC)andrewedwardjudd

Because the history of science should be taught as the history of science. I don't really care what Joule was happening when ice melts-- I care about what modern scientists think. Joule didn't know about liquid helium, which is a liquid (at 1 atm) even at 0 K (absolute zero). It does not freeze at normal pressure, no matter how cold. I'm fairly sure Fermi knew about liquid helium in 1952, so I very much doubt that he thought molecular motion ceases at absolute zero. If you have liquid, it's quite obvious the molecules are still moving! This energy is not referred to as thermal energy, since it cannot be extracted. But it is there, all the same, and the amount can be calculated (did you READ zero-point energy?) As for the comment on time to come to equilibrium, it demonstrates my point, no matter if it takes time. If added-heat can EVER disappear without a temperature-trace in a system (which it certainly can) that means heat is not temperature. It means you can add heat, and ultimately temperature does not change, yet the heat is still there, and can be removed (as for example when an ice pack is used to cool something). One would exect that you'd have to wait some time to see what effect heat would have on a system, anyway, since temperature is a system-property, and single particles do not have temperatures (nor, for that matter, do they have a definable "heat." We've already been over this on this talk page and I'm not going to do it again.)SBHarris 21:34, 14 March 2012 (UTC)

It is peculiar how you can come up with this,

Heat has never been kinetic atomic vibrations

Then say you dont care what Joule said and then say the history of science should be taught as the history of science. Evidently facts are irrelevant to you. Why??Andrewedwardjudd (talk) 21:53, 14 March 2012 (UTC)andrewedwardjudd

Not at all. Have you read the lede to this article, lately? The planets have never revolved in crystal spheres, either, though some ancient astronomers thought they did. But you'll have to go pretty deep into various articles to find that fact. Look at the artcle on Jupiter or (say) the Solar system. Do you see any mention of Aristotle's etheric spheres? No? Why not? SBHarris 23:25, 14 March 2012 (UTC)

Sbharris your explanations seem to apply only at exreme conditions, liquid helium, zero point energy and so forth. Would you care to say how you measure zero point energy. e.g. joules, ergs, calories etc.? And how you describe the properties of gases that liquify above, let us say, 40K?

Further you write "I don't really care what Joule was happening when ice melts-- I care about what modern scientists think." I would like to know what these "modern scientists" think, I suggest that, if it is 'modern', you will have no problem giving a link, I would like one, please! --Damorbel (talk) 14:01, 15 March 2012 (UTC)

language

We are here looking at a problem of language. Textbooks of physics mostly prefer to read the word heat to refer to quantity of energy transferred as heat; this is the usage of the Wikipedia articles. More widely based usage, including ordinary language, vaguely refers to heat as a moiety of the internal energy of a body; this is the usage that Andrewedwardjudd is advocating.

As a matter of logic, it might be useful to distinguish between 'heat' and 'quantity of heat'. As another matter of logic, the sentence 'heat is intestine motion' is not logically identical with the sentence 'heat is constituted by intestine motion', nor with the sentence 'heat is properly explained as intestine motion'. The present debate above seems mostly to be about failures to make these distinctions.

Andrewedwardjudd is right that the various usages are at least sometimes confusing. The present approach of the Wikipedia seems to be to take heat in physics strictly defined to mean quantity of energy transferred as heat. Andrewedwardjudd may be right to protest that this is an abuse of language, but it is one that is more or less universal in textbooks of physics and is rationally extracted from the classical writings. Andrewedwardjudd is wrong to practically ignore this well established textbook extraction from the classical writings.Chjoaygame (talk) 18:51, 14 March 2012 (UTC)

Chjoaygame, earlier you said this of me "Contrary to the confused ideas of the author of the comment, but as considered by classical authors, heat is primarily a macroscopic thermodynamic concept, not a microscopic one" Evidently you realise it was not me who lacked knowledge of history and was confused.

Earlier there was a reference here to a study highlighting this issue and you who had it removed. Your defensive attitude is a bit peculiar. You are obfuscating for some reason that I find very hard to understand. You are evidently deliberately trying to get wiki to reflect something that you know is incorrect. Even attacking me and then attempting to ignore me came easy to you. Wiki is wrong and most people regard the classical writers as being right so Wiki needs to reflect this reality. Unless of course you are one of those wiki insiders who create history these days?

You said while attacking me,

>>The present Wikipedia article on heat is intended to carefully follow the definitions preferred by the classical authors.

Come on! you are doing your best to ensure that never happens. Why??

Andrewedwardjudd (talk) 20:13, 14 March 2012 (UTC)andrewedwardjudd

Andrewedwardjudd is right to complain that I initially and wrongly responded that he had not carefully studied the classical authors. I now accept that he has done so.

But I think his reading of them is partial and that it does not give due weight to the present day textbooks that abuse language by taking heat to mean quantity of heat, as distinct from heat in a more ordinary language usage, which includes heat as meaning temperature. This distinction is to be found in the classical authors. The idea of 'the amount of heat in a body' is not convenient as a quantity of physics and this is recognized by the classical authors, but I have the impression that it is not recognized clearly enough by Andrewedwardjudd. Must go to breakfast now; will continue later.Chjoaygame (talk) 21:42, 14 March 2012 (UTC)

The issue here is that academics in the same vein as Sbharris and yourself are writing patronising papers about how stupid their students are because they say heat is something in a body and these academics are saying absolutely that the classical writers never said that and the students are wrong confused and need to learn what is correct.

Wiki should reflect the reality that people like yourself, who are confused as to what the classical writers said, are wrong, and their students are not necessarily as stupid as they are claimed to be. It is not just about language. People like you and Sbharris want to pretend there is no history and only idiots think there was. It is pervasive everywhere you go these days that people swear blind black is white when evidently they have no clue what they are talking about.

Wiki needs to point out that for reasons that are not clear the modern definition of heat is very different to the one used by the classical writers. And we do have a reference already to justify that which you removed because you decided it had no significance. Andrewedwardjudd (talk) 22:03, 14 March 2012 (UTC)andrewedwardjudd

At present the lead of the article starts:

In physics, chemistry, engineering, and thermodynamics, heat is energy produced or transferred from one body, region, set of components, or thermodynamic system to another in any way other than as work.

In ordinary language, as distinct from technical language, heat has a broader meaning. This can lead to confusion if the diversity of usage of words is forgotten.

Further details are given in the body of the present article. Evidently Andrewedwardjudd thinks that these warnings about language are not enough. At least one other editor thought that they were otiose and would be better omitted. I suppose there is a range of opinion about the proper emphasis here.

I think that the present article takes a considered view extracted from the classical authors who were more or less conscious of the difference between the ordinary language meaning of heat and the technical meaning, and that the present article concentrates on that technical meaning and is not at all interested in the ordinary language meaning. Andrewedwardjudd seems to think that this considered view is patronizing and insulting and inaccurate. Subject to correction by further comment on this page, I think this considered view probably accords with the current weight of editorial feeling?

I think an article that tried to preserve the dominance of the ordinary language meaning of the word heat would be so cumbersome as to make it impractical and hard to read. I would not object if someone went through and systematically, instead of 'heat', wrote 'amount of energy transferred as heat' in the appropriate places; but I think this would probably be unacceptable to many editors.Chjoaygame (talk) 23:35, 14 March 2012 (UTC)

According to Wiki what is heat? This spectacular picture appears on the heat page

http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/171879main_LimbFlareJan12_lg.jpg/300px-171879main_LimbFlareJan12_lg.jpg

The description begins with the word heat. There is no heat in that picture according to wiki. Heat is something that is mathematical rather than actual. So why the misleading picture that begins with heat? What the hell is heat these days?? Worse the caption reads heat generated by the nuclear energy of the sun. No heat is generated by the nuclear reaction according to wiki. Instead thermal energy is created and then heat is something that is moving due to the temperature difference created by thermal energy. But what is moving? Sometimes it is a thermal energy transfer and sometimes it is a radiation transfer. Radiation is not heat and heat is not radiation. heat cannot be transferred by radiation. Wiki is insane. Andrewedwardjudd (talk) 03:42, 15 March 2012 (UTC)andrewedwardjudd

Andrewedwardjudd asks above "According to Wiki what is heat?" The Wikipedia article on heat says that the word heat can be used either technically or in ordinary language. Andrewedwardjudd seems not to understand that distinction. Let us hope that he will calm down and come to understand it, a process that will take him some time and effort.Chjoaygame (talk) 19:37, 15 March 2012 (UTC)

Thermal radiation is a (small) subset of radiation-- it is electromagnetic radiation with a black body spectrum. This type of radiation IS a type of heat. Thermal radiation is thus one mechanism of heat transfer. I'm really sorry to confront you with a language in which all airplanes are vehicles, but not all vehicles are airplanes. It's very confusing, is it not?

In this present thermodynamic sense of heat, heat is heat in the sun as long as it's moving. All that is necessary to have "heat" is that the energy be thermalized (have a temperature). Then, it is heat so long as it is moving along a temperature gradient. That includes when it is conducted from the solar core by radiative transport, then to the outer edges of the Sun by convection (see convection zone for nice pictures), and then finally across space by radiation transport, once again.

As for the problems of a language in which thermodynamics uses the word "heat" slightly more carefully than the average person, that's science. I've suggested making this article heat (thermodynamics), very much as we've done with work (thermodynamics) so that the other ways of using the word (including the classical ones) can have their own places as articles, accessable by dab page. So far, nobody has seen fit to comment on my suggestion (just above). I supposed you'd rather just complain? SBHarris 19:54, 15 March 2012 (UTC)

I agreed with Sbharris that a re-name would be good, as above.

I do not know the proper technique for re-naming articles. If I did, I would forthwith re-name this one Heat (physics). I prefer this over other possibilities that I have seen. If someone who knows the proper technique for re-naming articles made this change I would be happy. If not, I will consider trying to do it myself simply by creating a new article called Heat (physics), copying this article to the new article, re-directing from the present article title and blanking the contents, and fixing the disambiguation page appropriately.Chjoaygame (talk) 20:10, 15 March 2012 (UTC)

No, don't do that-- it gets you into endless trouble with edit histories. Moving articles with a long history to a new title now really needs to be done by an admin. You can make a simple request at the renmame board if we're agreed that this article needs to be heat (physics) or heat (thermodynamics). SBHarris 20:30, 15 March 2012 (UTC)

Ok. I think your and my agreement will be enough since there seems to be no opposition. I prefer Heat (physics). If you agree with that I could make the request that you suggested, or you might do it yourself.Chjoaygame (talk) 20:36, 15 March 2012 (UTC)

Circular definitions

Copy-and-paste of part of the comment by Sbharris from just above:

As for this article, it has some serious problems with circular definitions up front (at worst) and definition-by-exclusion at best. We're told thermal energy is any energy that isn't thermodynamic work. Then if you look up thermodynamic work, you're told it's any energy added to a system that isn't heat! LOL. You want to try that again? SBHarris 17:41, 14 March 2012 (UTC)

In my opinion, this comment about circular definition signals an important contention, and is well founded and worthy of attention.

The definition of amount of heat as energy transferred by mechanisms other than work does indeed rely on a massive presupposition, that energy is conserved, and on lesser presuppositions about ways of distinguishing between heat and work transfers. This definition was perhaps first proposed by Bryan in 1907. Carathéodory at the suggestion of Born took it up in 1909, and it was promulgated by Born in 1921. It is now often used with a triumphalist flourish in order to celebrate how clever was Carathéodory and how clever are his followers.

The traditional way before these events was to define and measure quantity of heat transfer by calorimetry, and to show that combined with observations of energy transfer as work, this definition led to the first law of thermodynamics, which is a form of the law of conservation of energy with specific reference to heat transfer. In this tradition, the law is derived from observations, not assumed a priori.

In contrast, the Bryan-Carathéodory-Born tradition takes the law of conservation of energy as assumed a priori for thermodynamics, so that the first law appears as hardly more than a mere definition. In this tradition, this re-casting is viewed triumphally as a masterstroke of physical insight. This tradition is the one followed in much of the Wikipedia writing on this subject. Some editors feel so strongly, it seems, about the "correctness" of this tradition, that I would be surprised if another tradition would survive editorial exchanges.

I haven't chased up the definition of work as by exclusion of heat, but it seems that Sbharris has a good point here.Chjoaygame (talk) 18:35, 14 March 2012 (UTC)

When I read wiki i have absolutely no idea what heat is. It appears it has nothing to do with hotness. It is just so totally silly it is beyond belief. When i drop this lump of metal it will become heated and be hot but it will contain no heat! It is brain damagingly stupid that heat has nothing to do with hotness or temperature. What is heat these days??? Andrewedwardjudd (talk) 20:31, 14 March 2012 (UTC)andrewedwardjudd

You cannot measure heat only with "calorimetry," because that requires that you know the heat capacity in advance. You can't know THAT unless you have some other way of measuring heat. The ONLY way to be sure how much heat you've made, is to make it from some work, as Joule and others did it classically. And if you can do that, you don't need calorimetry-- you already know by conservation of energy how much heat you have, since you measured how much work you did, and that's how much heat you made. No temperature measurement is needed. You see the point? SBHarris 20:36, 14 March 2012 (UTC)

I am not sure what your point is. Calorimetry is still used today so evidently they dont know how much heat will be produced.Andrewedwardjudd (talk) 20:57, 14 March 2012 (UTC)andrewedwardjudd

Actual calorimetry must be standardized with a known amount of heat made by some other known process of work (usually work used to heat an electrical resistor). Have you ever actually used (including calibrated) a modern calorimeter (for example, a differential scanning calorimeter)? SBHarris 21:14, 14 March 2012 (UTC)

When i last used a calorimeter it was not modern when I used it, but as a matter of course everything we used had to be calibrated by us or somebody else.

But this is a bit of a distraction. At some point in time the definition of heat changed and in the interests of readability that ought to be recorded by Wiki if Wiki is going to so often quote the classics.

Does it not interest you that so many people have no idea that the modern definition is so different to the previous one??? Were you surprised by my quotes or do you just enjoy attacking people so often so quickly when they try to highlight this to you??Andrewedwardjudd (talk) 22:16, 14 March 2012 (UTC)andrewedwardjudd

There is an endless series of aricles to be written about how the language of science has changed in the past, and is still charging. And this is true in every subject. However, one could get bogged down in it forever. In fact, the word science itself once meant something very different from what it means now, and you should see the article science for some wars over when natural philosophy stopped being that and became natural science and then finally just "science" to many people. But not for everyone.

Wikipedia is always stuck with having to pick out definitions in words. For scientific words, and even technical words, concensus has been that WP always try to give the best technical defintion, and leave other looser ones to dab pages. Thus, if you look up energy you get the physics definition in joules first, and others only as a dab. You might find this at odds with the way most people use the world "energy," but there you have it. Most editors have tended to let the well-defined definition, if it exists, be primary. Otherwise you're going to have to explain "energy" in terms of why I have more of it on some days than others, or some other metaphorical stuff. Wikipedia actually does this for terms like "heat" and "work" and "energy". But it doens't do them in the primary articles on them. SBHarris 22:48, 14 March 2012 (UTC)

Sbharris you write - "Wikipedia is always stuck with having to pick out definitions in words". Isn't that what an encyclopeadia is for? If you want to do something else I suggest you are in the wrong place! But I agree, if you want to explain how much 'heat' or 'energy' you have today, this is not the place to do it; perhaps a poetry club will suit your muse better. --Damorbel (talk) 16:35, 15 March 2012 (UTC)

May I remind you of WP:NOTDICT plus the existence of a separate Wiktionary for people who want to carry out the endless task of deciding what the common person means by a word? Wikipedia's policies about this kind of thing are set in a very different way. Which I don't have time or inclination to explain to you. But which I will be happy to put you in arbitration if you violate. SBHarris 19:38, 15 March 2012 (UTC)

(Thermodynamic) work is defined as follows. You have some system whose formal description contains some external parameters. Exam[ples of such parameters are the volume of a system, the magnetic field the system is subject to, the position of the center of mass in the gravitational field etc. etc. Work is then defined as the change in (internal) energy due to the change in these external parameters. If X is such an external parameter, then for small changes dX, the work done by the system will be proportional to dX and can thus be written as -x dX, and x is called the generalized force conjugate to X. Heat is defined as the change in energy due to any other process than the changes in external parameters, and conservation of energy implies that dE = dQ - sum over xi dXi. In case of quasistatic changes, the change in the Xi don't contribute to the entropy change, and dQ = T dS. This means that dE = T dS - sum over xi dXi. But since the internal energy in thermal equilibrium is fixed when S and the Xi are specified, you always have that dE = dE/dS dS + sum over dE/dXi dXi. That in the special case of quasistatic changes you have dE = T dS - sum over xi dXi then implies that you always have dE/dS = 1/T and dE/dXi = - xi. The relation dE = T dS - sum over xi dXi thus holds generally, also when the changes are not quasistatic. Count Iblis (talk) 20:27, 15 March 2012 (UTC)

reasons for undoing good faith edit of lead

I have undone the new edit by Andrewedwardjudd because it was unsuitable for the lead where he placed it. It was too detailed and specialized for its placement.

The content of his edit was perfectly reasonable and may be suitable, with perhaps some modifications, for a place in the body of the article, as opposed to the lead of the article. It is a matter of semantics and history and perhaps a suitable new subsection might be useful for it.Chjoaygame (talk) 20:20, 15 March 2012 (UTC)

Looking again over that undone edit by Andrewedwardjudd, I see that my comment just above is too accommodative, when I wrote that it was "perfectly reasonable". The contents of the undone edit were not adequate representations as they claim to be. For example, for a considerable time before 1850, Kelvin more or less accepted the caloric theory of heat. Lavoisier and Laplace are classical authors who could be cited selectively to make it seem that they supported the intestine motion theory, because they carefully stated it in comparison with the alternative caloric theory. The classical authors such as Clausius and Maxwell were aware of the difference between the ordinary language and the technical meanings of the word heat, and it would be seriously misleading to hide that important fact; but the undone edit did more or less hide it.

The undone edit was based on the editor's own reading of original sources, and this is not reliable sourcing as required by Wikipedia policy. It would be loosely described as synthesis or original research in Wikipedia terms. For such general questions of history of scientific usage, secondary and tertiary sources are very necessary for Wikipedia standards of reliability; the undone edit did not comply with this.Chjoaygame (talk) 22:55, 15 March 2012 (UTC)

This comment is utterly stupid. When Kelvin wrote the second law of thermodynamics he wrote that in a paper entitled On the Dynamical Theory of Heat in 1851. The idea that I am misreading the reliable sources is a lie. It is seriously misleading the reader to obfuscate like Wiki editors are doing over the classical definition of heat. Wiki is just garbage while this goes onAndrewedwardjudd (talk) 15:48, 17 March 2012 (UTC)andrewedwardjudd

Editor Andrewedwardjudd should read some of the Wikipedia policies about reliable sourcing, for at present he seems not to understand them. The editor is reading a primary source (Kelvin 1851) for himself, and proposing therefrom to cite it as a reliable source. Wikipedia policies do not accept such a process. It is an example of original research for the present purposes. For a reliable source for opinion about such historical questions as those we are now considering, several concordant secondary and tertiary sources are needed to constitute reliable sourcing for Wikipedia entries.

Moreover, Editor Andrewedwardjudd is pushing a very particular point of view and that also needs to be taken into account, besides the problem of reliable sourcing versus original research.Chjoaygame (talk) 21:27, 17 March 2012 (UTC)

This has got to be the strangest comment i have ever heard on Wiki and that is saying something. A newspaper is a reliable source for the purposes of Wiki and you are telling me that quoting Lord Kelvin himself is not a reliable source?

Original research means the writing is the primary source of the information. If you build an article that extensively quotes other peoples verbatim comments without changing the context of what they say it cannot by definition be original research. Now stop being so silly and allow editors to produce something capable of accurately describing the historical record, where for reasons that are not clear a new so-called "strict" definition of heat has been imposed via later text books that enormously confuse the reader educated before this imposition.

Have you read this?

http://books.google.fi/books?id=B5QOAAAAIAAJ&pg=RA1-PA108&dq=On+the+Nature+of+the+Motion+which+we+call+Heat,+clausius,+philosophical+magazine,+1857&hl=en&ei=FH84TJvOEIKknQfXuoznAw&sa=X&oi=book_result&ct=result&redir_esc=y#v=onepage&q&f=false

http://www.eoht.info/page/On+the+Nature+of+the+Motion+which+we+call+Heat

http://books.google.fi/books?id=hA-oIDR0eXkC&lpg=PA38&dq=clausius%20heat%20as%20motion&pg=PA38#v=onepage&q=clausius%20heat%20as%20motion&f=false

And what is interesting is that it was because of John Tyndalls enthusiasm for Clausius that so many of his memoirs were translated into English. In the preface to the translations Tyndall said that Clausius was his teacher on the molecular theory of heat and still was. Tyndall wrote the classic Heat as a mode of motion around 1868

http://books.google.fi/books?id=MwwAAAAAQAAJ&printsec=frontcover&dq=heat+as+a+mode+of+motion&hl=en&sa=X&ei=Kn9lT7DYBMKG4gSQ75GsCw&ved=0CC4Q6AEwAA#v=onepage&q=heat%20as%20a%20mode%20of%20motion&f=false

Andrewedwardjudd (talk) 21:57, 17 March 2012 (UTC)andrewedwardjudd

Requested move

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: Not moved. Jafeluv (talk) 13:34, 22 March 2012 (UTC)

---

Heat → Heat (physics) – See conversation on TALK:Heat. There are multiple complaints that the page that heat directs to is the science page, which defines heat in the thermodynamic way, which is incompatible with many colloquial uses of "heat" in English, and even use of "heat" in science 150 years ago (when you could speak of an object's "heat content," if it had a static temperature distribution whereas now, you must speak of its thermal energy content). My proposed solution is to do what we've done for topics like work which directs to a dab page, rather than energy which goes to the science page without this being renamed energy (physics). Somehow, people have more problem doing for heat what they now do for energy. Which is to generally not ONLY have the primary direct to the most well-defined tech use of a word, but (at least in cases where this doesn't happen, such as energy) at least make the main article into a parenthesis-category named article, such as work (physics).SBHarris 23:01, 15 March 2012 (UTC)

• Comment. The top referent for heat is an NBA team that got 385,000 page views in the last 90 days. This page is the No. 2 referent with 211,000 views. The DeNiro movie got 127,000, thermal energy got 87,000, and the magazine got 12,000. Kauffner (talk) 08:43, 16 March 2012 (UTC)

• I favour the requested move.Chjoaygame (talk) 18:59, 16 March 2012 (UTC)

• Oppose this is the most encyclopedic/educational topic, the topic with the most long term significance. Per the Avatar decision, the physics concept should remain primary. 70.24.251.224 (talk) 04:36, 17 March 2012 (UTC)

• Oppose. None of the other relevant topics seem appropriate as possible primaries. No one has even suggested making anything else primary. Why demote this topic? Kauffner (talk) 06:31, 17 March 2012 (UTC)
• Oppose. The situation with work is not analogous because of the alternative definition of "work" as "labor". The situation with energy is analogous, as the scientific concept is the basal topic and the other contenders for primary meaning are subtopics thereof (the basketball team notwithstanding). Powers ^T 14:51, 17 March 2012 (UTC)

• Oppose I think the distinction between heat and thermal energy may confuse some lay people and even some people with a basic understanding of science, but apart from that the scientific meaning is clearly the primary one, which is not the case with "work". PatGallacher (talk) 21:14, 17 March 2012 (UTC)

• Oppose Wiki should make it clear up front that some modern writers have imposed a new so-called "strict" definition of heat upon readers, and ridiculed the classical idea that heat was a living force or molecular motion inside the object that contained heat, to the point that articles are written today abusing students who agree with the classical writers like Joule Clausius Maxwell Kelvin etc etc as if these people are scientific morons. And evidently there are a few wiki editors here who are fond of considering others as ignorant when this topic is raised, when they are themselves demonstrably ignorant of the history of the modern theory of heat. Wiki obviously needs to link the basic idea embedded in the classics which develop the modern theory of heat to which it constantly refers to, with todays "new improved super duper" 'modern' theory of heatAndrewedwardjudd (talk) 06:37, 18 March 2012 (UTC)andrewedwardjudd
• Oppose as others already say here, heat as it is now is the main meaning of the word and should have precedense. Pinut (talk) 09:50, 18 March 2012 (UTC)
• Oppose -- The physics/thermodynamics topic is clearly WP:PRIMARYTOPIC. The only potential rival is the preliminary rounds at an athletics tournament. I am not clear how they come to share the name, but my copy of Concise OED treats it as the 7th (of 10) usages of the word, a derivative usuage not as a separate word. All other uses are clearly derivative, and they can easily be found via a dab-hatnote. Peterkingiron (talk) 14:19, 19 March 2012 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Flow

This article starts: "Heat flows spontaneously only from systems of higher temperature to systems of lower temperature." It would be far better if it were net heat flow that was discussed. Heat does flow both ways, unless one system is at absolute zero. Yes, in the distant past the current wording was OK, but it isn't now. The wording creates the question "How do the two systems know which is hotter?" - but of course there is no "know" to it. This is not a trivial point: nobody is going to understand the principles involved when discussing "global warming" if the level of understanding is limited by a mysterious knowledge by inanimate systems of which of two systems is warmer. There is clearly heat flow from the sun to the earth. There is a much smaller - essentially negligible - heat flow from earth to sun. It is far easier to understand that heat emanates from all bodies (not at absolute zero) and the observed flow is always a net flow. 184.60.38.240 (talk) 01:54, 16 March 2012 (UTC)

Heat flowing is a concept that belongs to the Caloric theory of heat which regarded heat as a fluid that determined the temperature of a substance (or body) according to the amount of caloric it contained. Caloric was said to be invisible and weightless, hotter objects weighing and appearing the same as in their cooler state, the theory remains popular in certain cultures but it fails every observational test.

The modern theory that puts heat as the microscopic motions of the atoms and molecules making up matter does not require 'flowing' for heat transfer, although fluid flow and convection are both examples of heat transfer by flowing, in both of these cases it is the matter that is flowing, not the heat. It may be of interest to note that, when the caloric theory of heat was being promoted, there was no consistent atomic theory available.

Modern theory has it that all matter above 0K has vibrations (or motions) that can be exchanged (thus in both directions) with adjacent matter. The vibrations in solids are coupled to adjacent matter by the very (atomic) forces that make the matter solid. In gases the atoms (and molecules) are not bound together so this method does not apply, instead the molecules have independent velocities and they exchange (kinetic) energy by collision. Thus at all times the motions of the atomic (and molecular) particles are being exchanged, the more energetic motions of the hotter particles gradually increasing the energy of the cooler particles and the coller particles gradually reducing the energy of the hotter particles. --Damorbel (talk) 07:22, 16 March 2012 (UTC)

The correct word for flow appears to be transfer. Flow is similar, but nothing actually flows. Instead via conduction vibrations from one object are exchanged by contact with another object where the net energy transfer is called heat. Via radiation exchange no heat can possibly flow from object to the other since heat is not radiation. But the net transfer of radiation is called amount of heat or amount of heating. Andrewedwardjudd (talk) 15:38, 17 March 2012 (UTC)andrewedwardjudd

andrewedwardjudd, you write "where the net energy transfer is called heat". Indeed you will find authors who state this. But what do you call the motion, possessed by particles above 0K, when the temperature is also uniform? In this case surely there is no 'net' energy transfer. --Damorbel (talk) 08:58, 18 March 2012 (UTC)

If you have an object at absolute zero in a system and you drop it, then state variable internal energy remains the same, state variable potential energy reduces, and therefore state variable heat increases. The system contains recently created heat. That was the view of Clausius where heat was hypothesised to be the kinetic motion of molecules, so that is my view until i find evidence otherwise, but iether way the system now has new heat inside the system, whereas most text books talk about heat entering the system and call heat a path variable. Obviously Clausius thought a body could have a quantity of heat that was available to do work that was there in the body due to the nature of the body itself - even if he was not absolutely sure what actually constituted that heat in the bodyAndrewedwardjudd (talk) 09:36, 18 March 2012 (UTC)andrewedwardjudd

100% of the kinetic energy of an object at absolute zero can be used to perform work, and thus NONE of such energy is heat. Heat always requires a temperature gradient, as well as at least one temperature above absolute zero. As for the other matter, is the net transfer of energy that is normally called heat. Of course two objects in thermal contact at the same temperature transfer energy back and forth to some degree as statistic demands, but by definition, we don't refer to this as thermodynamic heat. SBHarris 04:39, 19 March 2012 (UTC)

I assume you know that sensible heat classically was kinetic energy inside an object?

If you do know that, please give me some details as to what you mean about kinetic energy inside an object being used to perform work at absolute zero. Andrewedwardjudd (talk) 05:38, 19 March 2012 (UTC)andrewedwardjudd

The talk above was about DROPPING an object at absolute zero in a system. Doing that adds kinetic energy to the system, but no heat. I have no idea what you mean by "classically." Since Einstein and Debye, it has been understood that the thermal energy in solid objects is only half composed of kinetic energy. However, this kinetic energy is very different from that of a dropped object, inasmuch as it is distributed in phase space, whereas the kinetic energy of an object at zero kelvins has only one direction and one momentum. It's not heat.

I will add that for a crystal at 0 K, there is zero entropy. This is true in any reference frame, for entropy is Lorentz invariant (as temperature is not). To make a crystal at zero K move, simply shift to a different reference frame. It now has kinetic energy but still zero entropy and still no thermal content. It isn't any "hotter"

Also, it also still has a temp of zero K, inasmuch as temperature is not Lorentz invariant, but like energy, the scaling factor for velocity between frames is the Lorentz factor, and gamma*zero = zero. It makes sense that faster objects are cooler, since their clocks run slower so you see their atoms move more slowly on average. It takes some work to show that if they have any entropy, it doesn't change due to this, however. It is believable with handwaving, however, as entropy is related to loss of information, and why should information in a thing depend on what frame you look at it from?SBHarris 19:09, 19 March 2012 (UTC)

It appears to me that the Lorentz factor should affect emissivity, not temperature, unless if we assume a different theory of physical potentials. Here's why:

"To make a crystal at zero K move, simply shift to a different reference frame. It now has kinetic energy but still zero entropy and still no thermal content. It isn't any "hotter"

Also, it also still has a temp of zero K, inasmuch as temperature is not Lorentz invariant, but like energy, the scaling factor for velocity between frames is the Lorentz factor, and gamma*zero = zero. It makes sense that faster objects are cooler, since their clocks run slower so you see their atoms move more slowly on average."

If your suggestions that the "coolness" for an object above 0K has something to do with the Lorentz factor, then an object would be "hotter" in frames of reference where it is at rest or closer to rest and "colder" in frames of reference where it is further from rest. The laws of thermodynamics use temperature, not entropy, to judge whether a body is "hotter" or not, for the purpose of determining the spontaneous flow of heat. To say that one object may be both hotter and colder than another object according to different observers, would create immense problems for the thermodynamics. For example, the efficiency of a Carnot cycle engine would depend on the frame of reference - a nonsensical idea. A Lorentz factor connected with physical potentials, rather than the relative velocity of some arbitrary observer, would allow for an invariant treatment of the theoretical efficiency of such engines. This is what I suggest is necessary.

It is clear that the only kinetic energy that can be attributed to temperature and entropy in a body is that which corresponds to modes of momenta in a body which cancel out, that is to say, excluding any net momentum of that body (I.O.W. the "phase space" as you called it). It is clear then that accelerating such an object in a frictionless, time-like geodesic path would have but one effect that may follow according Lorentz time dilation, increasing its emissivity, for field interactions which would otherwise act to block radiation from being permitted into the object would be delayed, thus allowing the radiation to permeate through the material as if it were closer to the ideal of a black body (by factor of ε=1-1/γ²=(v/c)²). The Lorentz factor in question would be defined in terms of velocity relative to the source of the radiation - not the observer.

There would also be a decrease in temperature, but only because of "spaghettification" of the modes of momenta inside the body such that thermal energy is converted into bulk kinetic energy, inasmuch as the modes of momenta may at first travel transversely to the gradient of the local potential (and thus subject to lateral forces, in addition to headway forces). At relativistic speeds, these momenta would travel mostly along the gradient of the local potential, given sufficient time and lateral forces. To the extent to which any bulk momentum of the accelerated object was derived from redirecting and "spaghettifying" the modes of momenta inside a body, the extent to which the object's temperature decreases. A similar concept is the conversion of heat energy into wind energy via pressure-volume work.

Conditions: If all bulk momentum were derived through this same process from "spaghettifying" deflection of internal modes of momenta, only then you could say that temperature would fall inverse to the Lorentz factor's increase, otherwise, the temperature change is free to follow some other function not equal to the Lorentz factor. Such an all encompassing requirement itself requires that local acceleration on a body to be solely a lateral-type force, and thus particles may not be allowed to change speed, only direction. Thus, the absorption of external momentum is either not allowed (as in the case for the assumption of a frictionless, time-like geodesic path), or it may be trivial (i.e. absorption of momentum with no net resultant other than that matching the instantaneous bulk velocity of the object, i.e. external momentum contributes a change in m*v via a change of m not v). If the object in question has the speed of light as its limit to bulk velocity, then particles comprising of that bulk must already move at the speed of light if the above said constraint is to be followed.

Proof: To show that this is required to meet the requirement that internal modes of kinetic energy (thermal energy) be inversely proportional Lorentz factor, all one has to do is complete the following thought experiment:

If v^2+u^2=c^2. Then γ=(c/u)=1/sqrt(1-v^2/c^2), which is the Lorentz factor $\gamma$. Proof:

(c/u)=1/sqrt(1-(v/c)^2)

(u/c)^2=(1-(v/c)^2)

(v/c)^2+(u/c)^2=1

v^2+u^2=c^2

Let v^2 be the squared bulk velocity of the system particles, and let u^2 be the weighted mean square of the transverse velocity of the particles. Assuming that the bulk has fixed transverse radial and circumferential dimensions, if the transverse velocity were inverse to the Lorentz factor, then it would explain time dilation. This is analogous to Einstein's "light clock" thought experiment. Furthermore, at a least in electrodynamics, particles traveling at c are limited to lateral or "orthogonal" forces:

“ Figure 3: A point charge at rest, surrounded by an imaginary sphere. Figure 4: A view of the electric field of a point charge moving at constant velocity. A very important application of the electric field transformation equations is to the field of a single point charge moving with constant velocity. In its rest frame, the electric field of a positive point charge has the same strength in all directions and points directly away from the charge. In some other reference frame the field will appear differently. In applying the transformation equations to a nonuniform electric field, it is important to record not only of the value of the field, but also at what point in space it has this value. In the rest frame of the particle, the point charge can be imagined to be surrounded by a spherical shell which is also at rest. In our reference frame, however, both the particle and its sphere are moving. Length contraction therefore states that the sphere is deformed into a spheroid, as shown in cross section in Fig 4. Consider the value of the electric field at any point on the surface of the sphere. Let x and y be the components of the displacement (in the rest frame of the charge), from the charge to a point on the sphere, measured parallel and perpendicular to the direction of motion as shown in the figure. Because the field in the rest frame of the charge points directly away from the charge, its components are in the same ratio as the components of the displacement: ${E_{y} \over E_{x}}={y \over x}$ In our reference frame, where the charge is moving, the displacement x' in the direction of motion is length-contracted: $x'=x{\sqrt {1-v^{2}/c^{2}}}$ ”

Thus, if v=c, then the "longitudinal" electric field of charge would vanish beyond a range of 0, or in layman terms, it does not exist. Thus, such a charge may not be subject to any change of speed. Its speed, if c, is always c. Furthermore, according to classical predictions, a charge moving at the speed of light that is subject to instantaneously circular motion is not subject to radiation:

“ Then we obtain; $P={\frac {2q^{2}\gamma ^{6}}{3c}}\left(({\vec {\dot {\beta }}})^{2}-({\vec {\beta }}\times {\vec {\dot {\beta }}})^{2}\right)$ where I have replaced all the constants and the negative sign dropped earlier. This is the Lienard result, which was first obtained in 1898. [....] It's also interesting that when the acceleration and velocity are orthogonal the power is reduced by a factor of ${\vec {\beta }}\cdot {\vec {\dot {\beta }}}$. The faster the motion becomes the greater this reduction gets. In fact, it seems to imply that as $\beta$ tends to one the power radiated tends to zero (for orthogonal motion). This would suggest that a charge moving at the speed of light, in instantaneously circular motion, emits no radiation. However, it would be impossible to accelerate a charge to this speed[....] ”

The model of electrons as "probability charge density functions" could be in a sense be the mere result of observing the statistical density of underlying fractional charges which move at the speed of light. So the idea that charges may satisfy the aforementioned characteristic is quite tenable.

Only in a model which assumes primary behavior in such a manner can one derive a temperature function that may inversely relate the Lorentz factor. Otherwise, such a temperature function would serve as a mere approximation.siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 18:11, 21 March 2012 (UTC)

You say: To say that one object may be both hotter and colder than another object according to different observers, would create immense problems for the thermodynamics. For example, the efficiency of a Carnot cycle engine would depend on the frame of reference - a nonsensical idea. A Lorentz factor connected with physical potentials, rather than the relative velocity of some arbitrary observer, would allow for an invariant treatment of the theoretical efficiency of such engines. COMMENT The efficiency is a temp difference divided by another temp. If all the temps are multiplied by gamma, then gamma factors out in that expression, and efficiency becomes Lorentz-ndependent also, unlike single temperatures. As for transfer of information between frames as a result of this, it all goes through what you call emissivity, but also the relativistic doppler effect, and it all comes out okay. Look at hot object moving by you at some speed will seem to you to have its clocks running more slowly and thus atoms moving more slowly back and forth, and thus it will be cooler for you, for the same reason its clocks run slow. It will radiate less (and also in different directions) for all the relativistic reasons. That the entropy (though not the temperature) of systems is Lorentz-invarient was known as early as 1907, proven by Planck himself: [3]. SBHarris 16:04, 22 March 2012 (UTC)

"If all the temps are multiplied by gamma, then gamma factors out in that expression, and efficiency becomes Lorentz-ndependent also, unlike single temperatures." Two fluids can have a different gamma. Also, if the two gamma are different, the change in gamma is also not going to be the same if you change the velocity of the observer. This would cause the ratio of the two temperatures to dependent on relative velocity with respect to the observer. To me, this is more than enough to consider this issue a real one.siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 21:03, 22 March 2012 (UTC)

If you have some odd system where you have heat tranfer between two fluids with relative velocities, you no longer have a single system and have just complicated the problem for no reason. In reality there is a Doppler shift in the heat transfer between fluids, which takes care of the fact that they are in two different frames. Whether you figure the efficiency from one frame or the other, it comes out the same. SBHarris 21:17, 22 March 2012 (UTC)

0	0.3	1	1.05	1.05	1	0.73	1.36
0.1	0.39	1.01	1.09	1.08	0.9	0.66	1.36
0.2	0.47	1.02	1.13	1.11	0.82	0.6	1.36
0.3	0.55	1.05	1.2	1.14	0.73	0.54	1.36
0.4	0.63	1.09	1.28	1.17	0.65	0.48	1.36
0.5	0.7	1.15	1.39	1.21	0.58	0.42	1.36
0.6	0.76	1.25	1.55	1.24	0.5	0.37	1.36
0.7	0.83	1.4	1.78	1.27	0.42	0.31	1.36
0.8	0.89	1.67	2.17	1.3	0.33	0.24	1.36
0.9	0.94	2.29	3.05	1.33	0.23	0.17	1.36

Row by row: Ten different observers at ten different velocities

The first column: Velocity of fluid one

The second column: Velocity of fluid two, with a rapidity that is 0.3 greater

The third column: Gamma of the first fluid

The fourth column: Gamma of the second fluid

The fifth column: Ratio of the third and fourth

The sixth column: Relativistic Doppler effect of the first fluid

The seventh column: Relativistic Doppler effect of the second fluid

The eight column: Ratio of the sixth and the seventh

This means that if the ratio between the temperatures remains the same, then the temperatures must vary by Relativistic Doppler effects, not the Lorentz factors. And honestly, that makes a lot more sense than saying that time dilation is what you focus on when discussing relative temperature changes.

However, you said that:

"To make a crystal at zero K move, simply shift to a different reference frame. It now has kinetic energy but still zero entropy and still no thermal content. It isn't any "hotter"

Also, it also still has a temp of zero K, inasmuch as temperature is not Lorentz invariant, but like energy, the scaling factor for velocity between frames is the Lorentz factor, and gamma*zero = zero."

So either you were right then, or you are right now.siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 03:06, 23 March 2012 (UTC)

I'm right in both cases. Here: enjoy. [4] SBHarris 03:52, 23 March 2012 (UTC)

After clicked the link, I just began to read the paper, and I saw the term "apparent spectral temperature". That seems like an important distinction there. I'm going to proceed the whole 11 pages now.siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 03:55, 23 March 2012 (UTC)

Going a little bit further, I already see it says, "An essentially tougher problem is to understand the relativistic thermalization: what is the intensive parameter governing the state with energy exchange equilibrium between two, relatively moving bodies in the framework of special relativity." This is exactly the topic of interest I had in mind. Continuing....siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 03:58, 23 March 2012 (UTC)

“

Snapshot 1: the Planck–Einstein equilibrium, when the energy current is carried by the moving body, ; in this case the moving body appears cooler

Snapshot 2: the Blanusa-Ott equilibrium, when the energy current stays with the observing body, ; in this case the moving body appears hotter

Snapshot 3: the Landsberg equilibrium, when the energy current velocities compensate each other inside the two bodies, ; in this case the temperatures of the two moving bodies are equal

Snapshots 4 and 5: the Doppler blue shift and red shift () equilibria, when the energy transfer is due to radiation, , ; in these cases the temperatures of the two moving bodies are related by a Doppler shift

”

(http://demonstrations.wolfram.com/TransformationsOfRelativisticTemperaturePlanckEinsteinOttLan/)siNkarma86—Expert Sectioneer of Wikipedia
^{86 = 19+9+14 + karma = 19+9+14 + talk} 04:16, 23 March 2012 (UTC)

Two bodies cannot simultaneously exchange heat by radiation. Edit undo

Edit summary should have read

heat not exchanged by rad. Heat only be transfer by rad. Radiation exchanged. Net radiation result

When two bodies are in radiative contact they simultaneously exchange radiation but only one amount of heat flows from hot to cold. Heat cannot be exchanged by radiation because radiation is not heat. When two isolated bodies of the same temperature are in radiative contact they exchange radiation with each but there is no heat transfer or exchange.

We do not talk in terms of net heat transfer from hot to cold when a hot body is in contact with a cold body. We talk in terms of net radiation transfer from hot to cold.

Net radiation transfer is calculated via stefan-boltzman for each separate body for a final net result.

If one photon is exchanged from a hot body to a cold body how much heat is that?

Heat exchange by radiation is without meaning. Andrewedwardjudd (talk) 16:03, 17 March 2012 (UTC)andrewedwardjudd

If you believe Stefan-Bolzmann then there's thermal energy exchange anytime you have two bodies, period. Whether you want to call that "heat" in both directions or just reserve the term "heat" for the net difference in energy transfer (net in the direction that there is a net flow in), that's up to you. The definition current in science now tends to reserve "heat" for the net flow from each object.

As for solids in contact, of course there's energy transfer in both directions whether they are separated by 10 nm of vacuum, or touching. The NET transfer is zero if they are the same temperature, but not if not. But it's only a net result in both cases, for of course energy always goes both ways. In any two objects at the same temperature, each has a distribution of atomic energies, and there's bound to be cases in which it goes either way by chance, whenever an especially slow atom hits an especially fast one. SBHarris 18:50, 19 March 2012 (UTC)

You are talking about energy exchange alot but the edit was talking about heat exchange. I dont think anybody has ever talked about a cold body in contact with a hot body exchanging heat with the hot body at the macro level? Instead we talk about a flow of heat from hot to cold. However at the microscopic level temperature might not be uniform in any body, we could then see a cold body sending heat from a tiny part of the cold body to the hotter body. Bodies in radiative contact are no different to bodies that are in physical contact. We dont talk about bodies exchanging heat at the macro level. Do we? Andrewedwardjudd (talk) 21:41, 19 March 2012 (UTC)andrewedwardjudd

No, your way of thinking about it correct. And your point is taken as good. When you go from micro to macro, all those small fluctuations of energy transfer both ways even out (subtract out), and only the bulk flow is left. And it is only that macro (bulk) flow of thermal energy that we call "heat." SBHarris 01:57, 20 March 2012 (UTC)