# Talk:Thermodynamic equilibrium

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1.What the formula for specific heat capacity????

see Heat capacity, Specific heat capacity

2.What the formula for specific latent heat of vaporization and specific latent heat of fusion?

Please show some examples that can prove the formula are correct.

'Local t. e.' Anybody got a reference for that? It's not what my understanding is.GangofOne 06:28, 15 August 2005 (UTC)

The first paragraph is general but good. I have a problem with LTE, namely the field to which these considerations apply need be mentioned (heat transfer?). Local thermodynamic equilibrium can mean many other tings, for instance it is an hypothesis on which calculations of collective diffusive processes are often based (not only radiation heat), and the basis for the Onsager approachuser:ThorinMuglindir

The definition of TE should include the word "isolated" somewhere - otherwise we could be talking about a non-equilibrium stationary state, for example a material with a constant flow of heat through it. The zeroth law then needs to say that the systems in equilibrium need to be in contact with each other, but otherwise isolated. The LTE is too specific - it should say that parts of the system are approximately equilibrium states, but not in equilibrium with each other, for example if the temperature varies with position. Carl Dettmann, Bristol 24 October 2005.

Global thermodynamic equilibrium means that the values of intensive parameters are homogeneous throughout the whole system Temperature certainly and pressure maybe, but density by no means (e.g. water at the triple point). --Art Carlson 17:23, 25 October 2005 (UTC)

Art, you are certainly right, that statement is too far-encompassing. Density doesn't work because it is not a quantity linked to the exchange of some extensive quantity (like pressure is linked to the exchange of volume, and temperature is linked to the exchange of heat). Otherwise on another notice sometimes the intensive parameter that controls equilibrium is not always something simple as (just) P. For example, in the presence of a gravity field, equilibrium is reached not when P is constant, but rather when ${\displaystyle P-\rho gz}$ is constant over the system. It seems the text needs to be more careful, though I need a bit of thinking in order to explain these subtleties as simply as possible. The rewriting from what I left is great.ThorinMuglindir 21:17, 25 October 2005 (UTC)
OK I made a more careful rewriting of that part.ThorinMuglindir 22:57, 29 October 2005 (UTC)
On a similar notice I reworded slightly the part about the glass of water at the end. An out-of-equilibrium state can be maintained in a system, not only "artificially maintained" as I had written. For example, the sun maintains a certain amount of non-equilibrieum on the surface of earth, but this is not "artifical."ThorinMuglindir 21:28, 30 October 2005 (UTC)
Two points:
• Density gradients are linked to the exchange of mass, through the process of diffusion
• diffusion of molecules will sometimes happen according to the gradient of density (like within a gas, if gravity is negligible), but not always (like at a liquid vapor interface). I believe that most generally, diffusion of a certain species will happen according to the gradient of chemical potential of that species: that's ${\displaystyle \mu }$ in thermodynamics equations and ${\displaystyle \mu _{j}}$ in statistical mechanics (grand-canonical ensemble).
• What is the equilibrium nature of water at the triple point, in the absence of gravity and boundaries? Would there be a tendency as time goes by to form large scale density variations, like water/ice planets, or would it be a big cloud of small ice crystals and water droplets? If so, how small? PAR 22:05, 30 October 2005 (UTC)
• If the system is not submitted to external gravity, but gravity between components of the system would remain, there would be a tendancy to form ice and water planets (or planets made of both more probably), though that would be only for very large systems. If gravity is totally suppressed, or for a smaller system, capillarity would prevent water drops from divinding when they are below a certain size. Sometimes two water drop would collide each other and merge. Big droplets would have a tendancy to divide, but would this process eventually eliminate all water masses above a certain size before they have time to form by random merging? I can't answer to this last question.ThorinMuglindir 23:58, 30 October 2005 (UTC)
That makes sense, except the part about large droplets having a tendency to divide. What's the force causing the division, just the random accumulation of angular momentum? PAR 02:47, 31 October 2005 (UTC)

Shouldn't the relation of thermodynamic equilibrium to entropy (specifically, the fact that entropy is maximized at equilibrium) be mentioned in here somewhere? I'm not knowledgeable enough about the technical details to add it myself, but I thought it was pretty important. Hypnosifl 21:50, 19 October 2006 (UTC)

## Steady state versus uniform conditions

It would seem the article needs to make a clearer distinction between the concepts of a "uniform" medium versus a system in steady state, the latter allowing spatial but not temporal dis-uniformity. I can take a stab at some of this in the thermal context. Rnestle 18:31, 22 February 2007 (UTC)

There's another state - equilibrium, which may not be uniform but will be steady state. This article should confine itself to the equilibrium state, with mention of other possibilities which should be developed in their own article. PAR 20:25, 22 February 2007 (UTC)
As far as other articles, shouldn't we have an article called Thermal equilibrium? presently that link just takes one to the present article. Rnestle 21:40, 22 February 2007 (UTC)

# Definition?

I'm a little confused about the wording and inferences implied in the definition. Can ANY system EVER be said to actually be in 100% equilibrium or 100% isolated from its environment or surroundings. i.e. will ΔS ever actually equal 0 or does it just 'approach' it?

—Preceding unsigned comment added by Nomdelapaix (talkcontribs) 12:15, 9 April 2010 (UTC)

You are right. No physically real system can be in strictly exact thermodynamic equilibrium. One studies approximations to it, and they are useful for theoretical studies, and for practical measurements. Practically all real physical systems involve transport of matter or energy or both, and are thus not strictly exactly in thermodynamic equilibrium.Chjoaygame (talk) 21:53, 28 November 2011 (UTC)

## Thermal dispersion?

What the heck is thermal dispersion? I am removing it from the article as it means nothing to me. --Drozdyuk (talk) 14:44, 14 July 2010 (UTC)

Furthermore I removed the reference to C.Michael Hogan et al., 1973, as I was not able to find it immediately, and there is not journal, publisher or any other indication as to the origin of the reference. --Drozdyuk (talk) 14:47, 14 July 2010 (UTC)

Agreed, the reference was too ambiguous for any one to find it. I believe the term that the previous author was looking for was "thermal diffusion", but perhaps by the term "dispersion" he was trying to to be inclusive of advective effects. However, there is still a serious problem with this section in that the river example contradicts the previous statement "in an equilibrium state, there are no unbalanced potentials (or driving forces) with the system." The river, while not time variant, has temperature gradients (i.e. potentials) driving heat flows via Fourier's Law and is encountering thermodynamic irreversablity. I think this section is confusing "equilibrium" with "steady". Even so, the river analogy has complications in that the flow is only valid in the Eulerian frame of reference and that real rivers are turbulent and hence stationary (invariant statistics with respect to time) rather than steady (invariant spacial distribution of state variables). Not sure what your background is Drozdyuk, so I apologize if I lost you with any of the aforementioned terminology. In any case, I wish to look at some text books for reference next week for a solid reference on the meaning of the term "thermal equilibrium". I think the truth is that it is often causally used in situations that really don't stand up to rigorous scrutiny because they depend on the frame of reference and a good article needs to discuss the distinction in a manner that people can understand. —Preceding unsigned comment added by Bdentremont (talkcontribs) 04:29, 15 July 2010 (UTC)

## Definition of Thermal equilibrium

TThe current article (08/10/10) states:

"Thermal equilibrium is achieved when two systems in thermal contact with each other cease to exchange energy by heat"

I believe is more proper to state that

"Thermal equilibrium is achieved when there is no longer a net change of heat exchange between two systems in thermal contact with each other"

in the same sense as when a chemical reaction reaches equilibrium. My point is that heat exchange never "ceases," but that the rate of heat exchange between AB and BA are the same. I don't think my version expresses this idea fully, Can someone paraphrase properly?

I think an even better definition would be "when the net energy exchange rate by heat between two system is zero". But I'd like to dig what textbooks say, before. --Cyclopiatalk 00:44, 11 August 2010 (UTC)

## Global stationarity

I feel that the phrase "global stationarity" is too technical for this article. I "think" I understand what it means, but I am very sure that the average reader won't. Q Science (talk) 16:36, 14 November 2010 (UTC)

## Equilibrium Temperature? (of planets. Copied from Kepler 11.)

This chart is copied straight out of the article for Gliese 581 g.
Does anyone else think it would be a good idea to make it a standard chart for all extra-solar planets that are compared to Earth?
With the relevent values swapped in of course.
24.79.40.48 (talk) 17:05, 26 November 2011 (UTC)

 Temperature comparisons Venus Earth Gliese 581 g Mars Global equilibrium temperature 307 K 34 °C 93 °F 255 K −18 °C −0.4 °F 209 K to 228 K −64 °C to −45 °C −83 °F to −49 °F 206 K −67 °C −88.6 °F + Venus' GHG effect 737 K 464 °C 867 °F + Earth's GHG effect 288 K 15 °C 59 °F 236 K to 261 K −37 °C to −12 °C −35 °F to 10 °F + Mars' GHG effect 210 K −63 °C −81 °F Tidally locked Almost No Probably No Global Bond Albedo 0.9 0.29 0.5 to 0.3 0.25 Refs.[1][2][3] [4][5]

### refs

1. ^ Cite error: The named reference Vogt was invoked but never defined (see the help page).
2. ^ Cite error: The named reference Stephens was invoked but never defined (see the help page).
3. ^ "NASA, Mars: Facts & Figures". Retrieved 2010-01-28.
4. ^ Mallama, A.; Wang, D.; Howard, R.A. (2006). "Venus phase function and forward scattering from H2SO4". Icarus. 182 (1): 10–22. Bibcode:2006Icar..182...10M. doi:10.1016/j.icarus.2005.12.014.
5. ^ Mallama, A. (2007). "The magnitude and albedo of Mars". Icarus. 192 (2): 404–416. Bibcode:2007Icar..192..404M. doi:10.1016/j.icarus.2007.07.011.

### break

Possibly. I'd definitely find it useful in visualizing the planets more accurately. I'll request more input by notifying WikiProject Astronomy, see if this can get any extra opinions. --Starstriker7(Talk) 19:11, 26 November 2011 (UTC)
No, many exo-planets are Super-Jupiter or Neptune sized, comparing those to Jupiter or Neptune would be better. Large Super-Jupiters should be compared to the smallest theoretical brown dwarf and Jupiter, smaller ones ( <5MJ ) can drop the brown dwarf comparison. 70.24.248.23 (talk) 23:11, 26 November 2011 (UTC)
That's why I mentioned, with relevent values swapped in. I know for example Jupiter has a suface temperature, core temperature, and equilibrium temperature. I don't see the problem with swapping the gas giant values in. I think the main point would be the comparison of equilibrium temperatures, which is mainly influenced by distance. The irradiance of each planet would be good also but no one does a comparison of those, the equilibrium temperature is the closest thing. 24.79.40.48 (talk) 15:35, 28 November 2011 (UTC)
Remember that thermodynamic equilibrium is a laboratory and theoretical thing, not found in general in nature, useful for basic theoretical studies, but not directly in practical applications. Thermodynamic equilibrium is a special kind of equilibrium, in which there is zero transport of everything. The kinds of equilibrium that pertain to planets involve massive transport of energy and matter, and are thus quite far from thermodynamic equilibrium.Chjoaygame (talk) 21:48, 28 November 2011 (UTC)
♦ What I will remember is your suggestion that a great many Astrophysicists, using Equlibrium Temperature, are out to lunch. 24.79.40.48 (talk) 03:25, 15 December 2011 (UTC)
That chart is nonsense. For instance, the Earth's "Global equilibrium temperature" is close to 5°C, not -18°C (which includes the albedo of clouds, ice, and the like). If the albedo is included for Venus (in order to make a fair comparison), the surface temperature should be 184.2K (-89°C), not 34°C. The greenhouse stuff is also nonsense, as is the claim that Venus is almost tidally locked (? - not really). Note: that chart was created by user:GabrielVelasquez the day before he was permanently blocked. I suggest that everything written by that person needs a real close look. Q Science (talk) 04:35, 29 November 2011 (UTC)
Apart from the above criticism of the content of the chart, I would add that the chart would not be appropriate for this article on thermodynamic equilibrium even if it were not nonsense.Chjoaygame (talk) 22:43, 29 November 2011 (UTC)

I find these comments silly since the chart is already in several articles for extrasolar planets, there is no need to dismiss it based on a hatred of a particular user. In fact I would go as far as to say the criticism is very irrational since almost every popular article on an extrasolar planet refers to its Equilibrium Temperature.
If scientist keep referring to this ( and it is -18°C for Earth) in many articles for extrasolar planets, then where is the article for this idea???
Maybe this thing that scientist keep refering to needs its own article, instead of being directed back here,?? 24.79.40.48 (talk) 03:30, 15 December 2011 (UTC)
List of 41 planet articles refering to Equilibrium Temperature 24.79.40.48 (talk) 07:14, 10 January 2012 (UTC)

I agree with Chjoaygame: this chart is completely inappropriate to this article, and even this talk page is not the place to discuss the usefulness of producing a standard chart. For a proper discussion, move it to someplace where editors with a suitable knowledge of the area will be involved. Quondumtalkcontr 08:11, 15 December 2011 (UTC)
It seems that my above remarks are not making sense to some editors. Please let me try again. Equilibrium is a widely used word, with many meanings. Thermodynamic equilibrium is a term of art in thermodynamics, a specifically defined kind of equilibrium, indeed a kind that practically never occurs exactly as defined; it can be approximated in laboratory experiments. Thermodynamic equilibrium explicitly forbids flow of any kind, while the energy budgets of planets are all about significantly large flows of energy, the very denial of thermodynamic equilibrium. The question here is not as to the content of the table but as to the content of an article on thermodynamic equilibrium. I have not studied the table in question here, but it does not need study to say that the present Wikipedia article on thermodynamic equilibrium is not its natural home. Without prejudice as to the value of the table for elsewhere in the Wikipedia, the table has no place here.Chjoaygame (talk) 18:38, 15 December 2011 (UTC)
Note, it would be courteous to state the actual question when starting an RFC. I infer it's whether to include the above chart? No, it refers to a different kind of equilibrium. Nobody Ent (Gerardw) 22:03, 16 December 2011 (UTC)

I have removed the text-wrap code and displayed the references. Notice that 2 of the references don't go anywhere. Also, that most of the data in the table is not referenced. Q Science (talk) 07:57, 17 December 2011 (UTC)

♦ How convenient for your argument that they don't work here, but they work fine where the chart was copied from: Original Chart
24.79.40.48 (talk) 07:11, 19 December 2011 (UTC)
Then please fix them here. After all, you are the one who added the chart here. Q Science (talk) 07:47, 20 December 2011 (UTC)
♦ Again, Maybe this thing that scientist keep refering to needs its own article! instead of being redirected back here. 24.79.40.48 (talk) 07:14, 19 December 2011 (UTC)
♦ Regardless of anyone understanding your comments about Thermodynamic Equilibrium or not, by default the relevant and important point you are both missing is that mentions of equilibrium temperature in articles about extrasolar planets do link to this Thermodynamic Equilibrium Article. All mentions in all articles. Any mention in any article of Equilibrium Temperature, here, Hello? If you are correct then correct all the redirects of Equilibrium Temperature. 24.79.40.48 (talk) 07:23, 19 December 2011 (UTC)
Perhaps you've not noticed that Thermodynamic equilibrium and Thermal equilibrium are distinct articles, and more importantly, distinct concepts. The relevant links in the Equilibrium temperature article appear to be correct as they are; the links to this article are only to point out that the two should not be confused. — Quondumtc 07:57, 19 December 2011 (UTC)
A very deceptive and rude statement given that the second article was just created out of the first as a result of this discussion here.24.79.40.48 (talk) 07:27, 10 January 2012 (UTC)

This chart/table definitely does not belong to this article or the thermal equilibrium article. If it is placed here, by similar argument, so should be tables and values for equilibrium temperatures of laptop computers, electric bulb, human body, stars, etc. Nothing special about temperatures of planets! This article is about the concept from physics, not a database of temperature values for different bodies. - Subh83 (talk | contribs) 21:20, 19 December 2011 (UTC)

Comment from uninvolved editor with interest in both areas, and some expertise in one (thermo and astro) This chart is almost completely irrelevant to this article. There's a rock in my back garden that is currently at 302K. So what? Greglocock (talk) 06:04, 20 December 2011 (UTC)

Nonsense, that you would compare a rock in your back yard to an extra solar planet and make the later as worthless says a lot about your reasoning, Any planet near the Habitable zone of the parent star is going to refer the concept of Equilibrium temperature in its article, bet on it! There are three or four such article that have this chart in them already. 24.79.40.48 (talk) 22:23, 8 January 2012 (UTC)
List of 41 planet articles refering to Equilibrium Temperature24.79.40.48 (talk) 07:19, 10 January 2012 (UTC)
Dear Editor 24.79.40.48, the question for the present purpose is not (1) whether or not the table is valuable or correct or interesting or important for climate science. The question for the present purpose is (2) whether it is relevant to the subject of the present article on Thermodynamic equilibrium; this question (2) is not affected by the question (1). Editors need to understand the articles to which they contribute. The article on Thermodynamic equilibrium is about a theoretical area of physics that is mostly concerned with small homogeneous systems and with strictly cyclic processes. By the criteria of the present article, planetary processes are far from thermodynamic equilibrium and discussion of them is therefore far from the concern of the present article. I have therefore tried to change the target of the re-direct from Equilibrium temperature to Climate model#Zero-dimensional models in order to satisfy your desire for a re-direct, as you will see below. But another editor insists that this is not acceptable, and I do not have time or inclination to struggle over it. However that re-direct problem is dealt with, it remains the case that a table about planetary equilibrium temperature is not suitable for an article on Thermodynamic equilibrium, no matter how excellent and valid and valuable might be that table might be from the point of view of studies of climate and planetary temperature. You may wish to verify this for yourself by studying the article on Thermodynamic equilibrium.Chjoaygame (talk) 04:10, 9 January 2012 (UTC)

### redirect

For the redirect from the source Equilibrium temperature, I have changed the target from Thermodynamic equilibrium#thermal equilibrium to Climate model#Zero-dimensional models. This may not be the best solution, but it may be a start to finding a better one.Chjoaygame (talk) 21:21, 24 December 2011 (UTC)

It should redirect to Thermal equilibrium. Equilibrium temperature has nothing to do in specific with the climate. It is a general concept in physics. There is an equilibrium temperature for your refrigerator as well. I am changing the redirection accordingly. - Subh83 (talk | contribs) 00:19, 25 December 2011 (UTC)
It is contrary to Wikipedia policy or ill-mannered of you to refer to my refrigerator, because it deliberately and quite unnecessarily makes it personal.
Your comment just above is an assertion of your unsourced opinion, which you may wish to back up with some reliable sourcing, if you wish it to be taken as more than your opinion. The phrase 'equilibrium temperature' is conveniently used occasionally in general physics, but, contrary to the implication of your comment, it is not a specially defined technical term. On the other hand it does have a usage in present day climate science that is more than a mere occasional phrase.
I think the best solution would be simply to delete the redirect item Equilibrium temperature. I thought this at first, then changed my mind when I thought of the usage in present-day climate science, but now you have led me to revert to my initial response, to delete the redirect item.
If one wants to keep the redirect item Equilibrium temperature, one should present a properly supported reason. I am not denying the occasional use of the term in ordinary physics, but I am saying that it is just an occasionally convenient phrase, not a specially defined term of physics, and as such does not deserve a Wikipedia entry of its own, not even a redirect. For this reason I would oppose retaining the redirect item if the redirect is to thermal equilibrium or to thermodynamics.
I think that most people who Google 'equilibrium temperature' or try to find it in Wikipedia will be coming from a climate science perspective, indeed from the very climate science perspective to which the redirect pointed just before you changed it. The webpage [1] provides an example of the special use of the term in present-day climatology, though by itself it does not qualify, I think, as a reliable source. An example that might perhaps just do as a reliable source would be the usage "... where T0 is the equilibrium temperature before the forcing ..." from Wallace, J.M., Hobbs, P.V. (2006), Atmospheric Science. An Introductory Survey, second edition, Elsevier, Amsterdam, ISBN 978–0–12–732951–2, page 446. A near-miss is "T = Te = 255 K , which is referred to as the radiative equilibrium or skin temperature of earth" from Dickinson, R.E. (1982),"Modelling climate changes due to carbon dioxide increases", pages 103-133 of Carbon Dioxide Review, 1982, Oxford University Press, Oxford UK, ISBN 0198553684, page 105. The climatologic specific usage is real but not very heavy, and hardly justifies a Wikipedia redirect for itself.
I repeat, my preference is now to delete the redirect item Equilibrium temperature altogether.Chjoaygame (talk) 10:39, 25 December 2011 (UTC)
User:Chjoaygame: Please provide reference to the relevant Wikipedia policy that forbids use of refrigerator as example. As for the rest of the discussion, please move it to Talk:Equilibrium_temperature. - Subh83 (talk | contribs) 19:53, 26 December 2011 (UTC)
Thank you for this. I was not referring to use of a refrigerator as an example, but to its being made my personal one. Further comments from me at Talk:Equilibrium temperature. I intend not to dispute this matter further, but to leave your edit as you made it there.Chjoaygame (talk) 00:20, 27 December 2011 (UTC)

### the table now put into the article on thermal equilibrium

The table in question has now been newly put into the article on Thermal equilibrium. I am not impressed that it should be there and I am here asking editors with relevant interests to look at its being there, and to make their comments on that question in the talk page there.Chjoaygame (talk) 08:03, 10 January 2012 (UTC)

I would say that I think the reason the table was newly put there is that the redirect of Equilibrium temperature has target Thermal equilibrium at the insistence of another editor, when I think the better redirect (if the entry 'Thermal equilibrium' is not deleted as I would prefer) would be to Climate model#Zero-dimensional models as noted above. Perhaps even another redirect target would be better?Chjoaygame (talk) 02:48, 10 January 2012 (UTC)

The lead is a summary of the article. There is no mention of information in the body of the article and therefore no reason to mention it in the lead. Information is not a concept of classical thermodynamics, and the body of this article is probably not the place to introduce it. This comment does not deny that information is relevant to thermodynamics, but says that this was not the way to express such relevance.Chjoaygame (talk) 03:46, 2 March 2012 (UTC)

## Entropy

This article mentions entropy only in the overview, this important thermodynamic concept is neither explained nor referenced in the rest of the article. Since the maximisation of entropy is fundamental to the concept of thermal equilibrium I suggest that this deficiency be remedied as soon as possible. --Damorbel (talk) 09:09, 31 December 2012 (UTC)

## This whole article is fit only for deletion

This article is:- 1/ subtantialy unsourced. Most of the material is WP:POV, e.g. the section Local and global equilibrium and the section Types of equilibrium The reason for the given links is unclear, either based on the contributors interpretation of what the link is about or to text books with no mentioned merit i.e. it contains the authors POV, without technical content.

2/ Very unclear. The opening statement:-

Equilibrium means a state of balance. In a state of thermodynamic equilibrium, there are no net flows of matter or of energy, no phase changes, and no unbalanced potentials (or driving forces), within the system. A system that is in thermodynamic equilibrium experiences no changes when it is isolated from its surroundings.

does not even contain the essential feature of equilibrium - that of uniform temperature. The writer is trying very hard to include systems that are not in equilibrium; read this section on uniform temperature where you will find the contributors opinion:-

Planck was setting aside surface effects and external fields and anisotropic crystals. Though referring to temperature, Planck did not there explicitly refer to the concept of thermodynamic equilibrium. In contrast, Carathéodory's scheme of presentation postulates the concept of thermodynamic equilibrium, though not explicitly postulating the existence of a temperature to define it.

Interesting stuff, fine for the opening of a high school paper but not for an encyclopaedia.

3/ The writer of this material contributes to another article Thermal Equilibrium with sections such as Distinctions between thermal and thermodynamic equilibria and http://en.wikipedia.org/wiki/Thermal_equilibrium#Theoretical foundations. In these sections the writer repeats much that is contained in this one without observable justification.

4/ Both of these articles should be rewritten with the contents substantially acceptable to a number of contributors.--Damorbel (talk) 14:16, 2 January 2013 (UTC)

So fix it, but all what you just stated can be fixed by editing, so deletion is not an option. AfD is not cleanup. --Cyclopiatalk 14:52, 2 January 2013 (UTC)
When two articles are virtually indistinguishable one of them should go!
I am extremely reluctant to edit when currently there is a very active editor who seldom responds to article discussion points in the talk pages. If you want to see what I mean, look here - very many edits; and here - very few talk contribs. --Damorbel (talk) 15:58, 2 January 2013 (UTC)

### Does Equilibrium Exist?

Earth scientists believe so, from geochemists sampling water to petrologists sampling rocks. Equilibrium is a relationship. Its existence is sought by simplifying the variables in those relationships (necessary and sufficient) to three classes: extensities, densities, and intensities. (The last two are intensive variables.) These, with phases, can be observed or measured to our satisfaction. If the equations are satisfied to the accuracy of our current instruments, the system is is equilibrium--by definition. Predictions will be reliable to our instruments' accuracies.

If we perturb the system when studying it, The Gibbs-Duhem equations predict that the system will respond in a manner that ameliorates these perturbations by buffering. This amelioration is also continuous, during phase changes, while experiencing a continuous flux of extensities; but if the generation of responses by internal reactions is much faster than the fluxes, the equilibrium relations will exist at every measurable point.

Practically, if two adjacent assemblages of minerals (differing in bulk composition) have densities that predict the same intensities, induction suggests they were in equilibrium. The system will be in equilibrium with respect to space (local equilibrium) and to time (quasi-static equilibrium [a most unhappy term]). It is the intensities that need be continuous (T, p, mu), not densities (specific entropy, concentrations).

So yes, geologists think there is an equilibrium even when any or all walls are relaxed. Those descriptions quoted in the article gave at least sufficient conditions; but most tried to strive for necessary conditions as well. (The connection with efficiency, asked above, was somewhat lost when switching to a theory of states rather than phenomena; but the relations sought above are the systems' characteristic functions and their derivatives.) Geologist (talk) 06:04, 4 January 2014 (UTC)

## undid good faith edit; why

I undid what was probably a good faith edit, unfortunately unsigned with a user name.

The undone edit intended to say that an externally maintained force field can produce temperature inhomogeneity in a body that is in a state of thermodynamic equilibrium.

There is in reliable sources unanimity that such is not so.

Nevertheless, it keeps being proposed by occasional users that it is so.

I think perhaps one reason why such users repeat the mistake might be that they see temperature inhomogeneity in non-equilibrium steady states in a gravitational field, and they fail to recognize that the difference between thermodynamic equilibrium and a non-equilibrium steady state is profound and far reaching. It invalidates their proposal. To understand this further, users should study the reliable sources, of which nine are currently listed in the article in the second paragraph of the subsection Uniform temperature of the section Characteristics of a state of internal thermodynamic equilibrium of the article.Chjoaygame (talk) 15:06, 13 November 2014 (UTC)

## undid good faith edit; why

I undid this good-faith edit. Thinking of the universe as a thermodynamic system is trying to stretch thermodynamics far beyond its scope. There are references to this effect in the article on Heat death of the universe. That topic is only of historic interest. It was conceived before the discovery of the general theory of relativity and the concept of black holes. Clausius poetically wrote of the entropy of the universe and suchlike, but that was fancy, not science. It doesn't fit here.Chjoaygame (talk) 18:42, 5 February 2016 (UTC)