Talk:Radiative equilibrium

question of the acute accent on Prevost's name
I have copies direct scans of direct photographs of the original journal article, generously supplied to me by the BNF. They show Prevost's name in bold capitals without the acute accent. The font of the article contains the acute accented small capital e as may be seen from the rest of the article. Perhaps Prevost did not know that his name should be spelt with an acute e, or perhaps the editor of the original journal thought he knew better or made a mistake. Yes, one sees Prevost's name spelt with an acute e in secondary sources. Perhaps they knew better than the original characters. Perhaps you have some reason to put in the acute? Chjoaygame (talk) 23:58, 18 October 2009 (UTC)


 * I changed the accent to be consistent with Pierre Pr%C3%A9vost. In French, especially in older texts, diacritic marks are omitted for uppercase letters, hence explaining the absence of accent in the original article. Reply if you need sauce. 134.76.223.1 (talk) 19:24, 19 October 2009 (UTC)

Thank you for your reply. In the originally printed journal article, of which I have a copy of what is probably a digital photograph kindly supplied to me by the BNF, one can see that the editor of the day did not know that he should omit diacritic marks for uppercase letters, and he supplied them liberally in several uppercase fonts, including the one in which he printed Prevost's name. He did not, however, supply one in the spelling of Prevost's name. I had checked this carefully in the original article when I posted the entry, because the acute accent mark does appear in secondary sources.Chjoaygame (talk) 11:05, 20 October 2009 (UTC)


 * Interesting. So there are a few books which follow the same pattern, with no accent for the name of the author: http://books.google.com/books?id=vYsJAAAAIAAJ&pg=RA1-PA457&source=gbs_selected_pages&cad=4#v=onepage&q=&f=false, http://cnum.cnam.fr/CGI/redir.cgi?8SAR20, http://gdz.sub.uni-goettingen.de/dms/load/img/ . If there is sufficient evidence that indeed the name has no accent, then for consistency, the name of this article Pierre Pr%C3%A9vost should be corrected. Big props, sincerely, 134.76.223.1 134.76.223.1 (talk) 14:59, 20 October 2009 (UTC)

Thank you for your reply. Thank you for this research which is valuable to lead me to more works of Prevost/Prévost on the physical side. It seems that modern French thinks the name should have the accent while the fellow himself, or at least his contemporaries, didn't?Chjoaygame (talk) 21:27, 20 October 2009 (UTC)

Out of date concept.
The concept of radiative equilibrium is as outdated as caloric and for the same reasons. Caloric failed as a concept because it treated heat as a material substance not as energy. In the early 18thC it became clear that mechanical work could be converted into heat without limit, thus there was no quantity of material substance that could be identified in a body that comprised 'the heat' i.e. a substance that made a body warm. Likewise radiation is a manifestation of energy that can have a source that is e.g. chemical or work. In particular radiation is freely exchangeable with chemical energy, it is the energy that is conserved not the radiation, thus 'radiative equilibrium is a meaningless concept. --Damorbel (talk) 18:10, 26 September 2010 (UTC)


 * Dear Damorbel, you may regard radiative equilibrium as out of date, and perhaps you are right. But the various forms of the concept are still widely used in current physics, and the Wikipedia does not, I think, put classical physics out of bounds as excluded by modern work. I do not agree with your argument that the concept of radiative equilibium is out of date for the same reasons as is the concept of caloric. Your reasons for regarding caloric as out of date are sound, but they do not apply to radiative equilibrium. It is true that there are various definitions and concepts of radiative equilibrium and the phrase 'radiative equilibrium' simple is often used inconsistently or ambiguously. But that is a reason to qualify it, not to try to outlaw or abolish it. If you read the references given in the article, you will find that the there are still valuable uses for concepts of pointwise radiative equilibrium (for example, besides the examples in the main Wikipedia article, and besides the countless other examples that one can easily find, also in E.A. Milne (1928), 'The effect of collisions on Monochromatic Radiative Equilibrium', Monthly Notices of the Royal Astronomical Society 88: 493-502 [http://adsabs.harvard.edu/abs/1928MNRAS..88..493M}) and of radiative exchange equilibrium (M.Planck (1914), The Theory of Heat Radiation, 2nd edition, translated by Morton Masius, Blackiston's Sons & Co, Philadelphia, recommended as the most explicit and readable account of Kirchhoff's law of emissivity/absorptivity by Goody and Yung (1989), on page 64 of their Atmospheric Radiation: Theoretical Basis, 2nd edition, Oxford University Press, Oxford; Goody and Yung is still currently used.)


 * Your statement that radiative energy is exchangeable with chemical energy is right, but it does not imply that 'radiative equilibrium' is meaningless. Large areas of present-day physics would be crippled if deprived of access to notions of radiative equilibrium; if you doubt this, your doubt will perhaps be dispelled by your reading of the literature.


 * You have a point here, that there are risks of ambiguity and confusion that arise when the word 'equilibrium' is used carelessly, and that the term 'steady-state' is sometimes safer. But it is not the job of the Wikipedia to act as risk monitor and preventer.


 * The Wikipedia is not aiming to correct people who use out of date concepts. The Wikipedia is aiming to report what the sources say. Your view that radiative equilibrium is an out of date concept is, in Wiki-speak, your own original research, see No original research, and is not a reason to edit the Wikipedia.Chjoaygame (talk) 23:33, 26 September 2010 (UTC)

Unsigned talk-age posts
Two unsigned talk-page entries, as follows, were posted today.Chjoaygame (talk) 00:04, 12 April 2013 (UTC)

Related concepts include the global-mean surface air temperature

 * How is it related? The blackbody temperature is an effective physical quantity, can you show the physical significance of the global-mean temperature? [This unsigned talk-page entry was posted by editor 79.119.56.246 at 23:06, 11 April 2013‎.]

Radiative equilibrium

 * Call me stupid, but such thing could be achieved only in a steady state (that is, dynamic equilibrium). For a general non equilibrium case, it's only an extraordinary coincidence if radiative equilibrium is achieved, and that will be only for a little bit, because the non equilibrium evolution will force it out. Maybe you could come out with examples where that radiative equilibrium exists but the system is not in a steady state? I mention this because Earth is assumed to be in radiative equilibrium, but it is not in a steady state.[This unsigned talk-page entry was posted by editor 79.119.56.246 at 23:06, 11 April 2013‎.]

comment on two unsigned entries
These two unsigned talk-page entries seem to be intended to start a general discussion. Here is not a place for general discussion. Here is a place for discussion specifically about edits to the article page. The two entries seem to seek discussion about things that are not the direct concern of this article page, but are perhaps, at a stretch, related concepts. It would be wrong to continue to try to promote on this talk page a discussion of the apparently intended kind.Chjoaygame (talk) 00:04, 12 April 2013 (UTC)


 * I was specifically referring specific claims in the article page. Read it carefully. But you might change "related" with "unrelated" and specify that the radiative equilibrium of the Earth is a hypothesis contrary to the fact. "this means that, in a steady state" - should change, too, because it suggests that Earth is in a steady state, and it is not. — Preceding unsigned comment added by 79.119.56.246 (talk) 15:03, 12 April 2013 (UTC)


 * Ok, fair enough. I have made changes that I think respond to your reasonable concern. This page is not about the factual actualities or speculations of climate, but about abstract or general physical concepts. The article already intended not to imply factuality or speculation, but evidently it was not clear enough about that intention. In response to your comments, I have now made changes that intend to more clearly avoid saying what might or might not be fact or speculation.Chjoaygame (talk) 16:07, 12 April 2013 (UTC)

Radiation not conserved
Radiation is not a conserved quantity, so this whole article is invalid. Radiation is similar to heat in this respect. Radiation is freely generated when charge is accelerated and correspondingly radiation is completely annihilated when absorbed i.e. when it accelerates charge.

This may be difficult to grasp but the non-conservation of radiation lies at the heart of all quantum theory.

It is quite normal to find texts supporting radiative equilibrium but, as with heat and caloric, the authors are mistaken at the most fundamental level. The defects of any citation puporting to explain radiative equilibrium should be treated with the same respect as those explaining perpetual motion! --Damorbel (talk) 11:55, 12 April 2013 (UTC)

Radiative balance
Should be merged with this article. Prokaryotes (talk) 21:39, 22 September 2013 (UTC)


 * No. The article titled 'Radiative balance' should simply be deleted or made more scientific. As it stands, the article titled 'Radiative balance' is obviously written by an autodidact enthusiast and it does not express the idea of radiative balance for the earth in properly logical terms that a trained scientific mind would use. It would be possible to re-write the article titled 'Radiative balance' so as to express it in properly logical terms that a trained scientific mind would use, but that would still have it as an article on the special topic of planetary radiative balance, not an article on radiative equilibrium in general.Chjoaygame (talk) 23:00, 22 September 2013 (UTC)


 * What is your suggestion for the term Radiative equilibrium oder Radiative balance or just Energy balance used in climate and Earth sciences to determine planetary energy budget, should it be incorporated under "Example" or get it's own article? Prokaryotes (talk) 00:58, 23 September 2013 (UTC)


 * Forgive me, is your "oder" a German word for 'or'? The possessive adjective 'its' is spelt its without an apostrophe.


 * Your recent round of edits is an enthusiastic attempt to change the direction of the present article by putting specialized material, not otherwise in the article, into the lead. As such it was fit for summary undoing.


 * It seems you want to insist on your way, and have put it back again, still with the same problem. You are the one who needs to propose things on the talk page before acting, not complain when others undo your faulty work.


 * The present article with the title Radiative equilibrium is a basic physics article. The notion of radiative equilibrium was put on the map by Prevost in 1791. It is important as basic idea for the understanding of electromagnetic radiation. It is of general physical interest.


 * It is evident that you wish to put something about its special relevance to climate science right into the lead, thus giving special prominence to your preferred example. The language you propose for your lead insertion is a specialized jargon of climate scientists, not the ordinary language of physicists. The term "radiative forcing" is the give-away there. It is an invention of climate scientists. In general physicists use other terms for such ideas. The adjustment for the tropopause is a very specialized consideration, not otherwise explained in the article, and not suitable for inclusion in a general physical article such as the present one; it is suitable perhaps for specialized articles on climate theory.


 * There is a specialist article entitled Radiative balance about your concern. That article is hardly worked on. There would be good place for you to do what seems best to you for that special area.


 * It is evident that you have not carefully read the article titled 'Radiative equilibrium' into which you wish to insert your preferred example, because it is already dealt with in the article, under the heading Radiative equilibrium, and your entry hardly takes that into account, so that your section Radiative equilibrium is redundant. Also it contains only one example, the one that concerns you, and that it has no reference.


 * I am not right now undoing your insertions, but I will continue to oppose it being done in the way that it has been done so far. I think it better if all of your recent edits to the present article so far were undone.


 * As for your question about what term do I prefer for Radiative equilibrium oder Radiative balance. That is not my worry about the scientific approach. My worry there is with the present article Radiative balance. I don't want to try to edit that article. But it has the serious fault that a trained scientific mind would know that no one in their right mind thinks that 'radiative balance' is a theory. It is a heuristic assumption or postulate for analytic purposes. It is a convenient assumption for analyzing the planetary energy transfer process. No one in their right mind thinks that it is strictly true at every time. The assumption is convenient for thinking about middle-to-long-term time averages. The Radiative balance article's lead's appeal to the law of conservation of energy misses the specifically most important physical assumption, of a steady state.


 * In summary, I oppose your attempt to coopt this physics article into becoming a climate article. I do not intend to try edit climate articles.Chjoaygame (talk) 03:12, 23 September 2013 (UTC)
 * Since your revert i changed the lede accordingly. Since the entire physical process evolves around a planetary climate system, adding an example for it in the lede is warranted. Especially so because the current article version has a "tone" notice, because it is to technically. Prokaryotes (talk) 03:30, 23 September 2013 (UTC)


 * The term at Google Scholar http://scholar.google.de/scholar?as_ylo=2013&q=Radiative+equilibrium+&hl=en&as_sdt=0,5 Prokaryotes (talk) 03:33, 23 September 2013 (UTC)


 * You continue to take a special enthusiast's approach. What do you mean by the entire physical process ...? What physical process? You seem to assume that a planetary energy transfer process is the default. Your special enthusiasm. Not the main focus of the present general physical article.


 * You wish to argue that the tone notice is because the article is too technical. Perhaps. It doesn't say that. Then you wish to propose that to deal with the tone, you are entitled to change the direction and subject of the article. Not a warranted move. If you want to write about your specialist concern, it would be easier if you wrote in a specialist article, than tried to turn the direction of another article, which you regard as "to technically".


 * You send me to Google scholar for some reason. I suppose it is to justify your terminology. I am not saying that your terminology is wrong or unfounded. I am saying that it is specialized. Specialized into an area that is not the emphasis of the present article. Your changes to the lead do not address my worries about your insertions.


 * Your reply above does not address all the problems I raised.Chjoaygame (talk) 04:03, 23 September 2013 (UTC)
 * Chjoaygame a talk page is not a FORUM, the page lacks/lacked a clear definition (hence the example) and noted for tone since April 2011. The focus should be the various kinds of radiative equilibrium, with focus on Earth atmosphere( Google Scholar http://scholar.google.com/scholar?q=Earth+radiative+equilibrium&btnG=&hl=en&as_sdt=0%2C5&as_ylo=2013 ) and use sections to address the different physical and historical aspects of the topic there.  Prokaryotes (talk) 04:30, 23 September 2013 (UTC)


 * First you tell me to go to the talk page, now when I do so you complain that I am treating it as a forum. I am on the talk page instead of just violent overwriting of your faulty edits. You offer your opinion about what the article should focus on, and put your opinion into direct editing without talk-page first. I disagree. Your lead definition is not a general definition, it is only an example, as you admit. So it does not deal with your worry that the lead lacks a definition. There are so many definitions that one in the lead needs to be very carefully considered. I am not sure that a fully precise definition is needed in the lead. The lead presently notes that there are various types of radiative equilibrium, and I think that is enough of a definition for the lead, when the next section of the article deals directly with the various definitions. It is a pity that you have damaged the structure of the article by putting mechanisms ahead of definitions.Chjoaygame (talk) 04:43, 23 September 2013 (UTC)

Per your request moved mechanism back to bottom, improved lede. There are now 2 examples in the lede and a clear definition (the reference could be improved). Prokaryotes (talk) 05:06, 23 September 2013 (UTC)


 * I see that you have made big changes to further your special interest against a more general physical approach. I will consider the matter further.Chjoaygame (talk) 06:49, 23 September 2013 (UTC)

radical new approach
Editor Prokaryotes has made a [number of edits that radically change the direction of the article, so as to make it accord with his special interest in climate, taking the article from its original nature as a general physical article. I do not like this at all. I think a specialist article on climate is a more appropriate place for Editor Prokaryotes to push his special interests in climate. It is evident that Editor Prokaryotes is resolutely determined to push those special interests, regardless of disagreement on the talk page; he makes changes that superficially seem to take regard of the talk, but the changes amount more to circumventive camouflage than to reasonable response.Chjoaygame (talk) 07:10, 23 September 2013 (UTC)

new definition
Editor Prokaryotes has put in a new and very special, muddled, and I think faulty definition of radiative equilibrium, for the sake of close focus on his special interest. His new definition needs strong revision.Chjoaygame (talk) 07:10, 23 September 2013 (UTC)
 * Considering the many errors, repeats of text and weasel wordings in the article and you as the main editor i suggest you stop editing this page and relevant topics. See WP:COMPETENCE Prokaryotes (talk) 07:25, 23 September 2013 (UTC)


 * I can see that you are a violent and resolute editor pushing his special point of view. It seems you have decided to invade and radically change this article. When I object on the talk page, you accuse me of incompetence, but you fail to address the matters that I raise civilly in the talk page, and your accusation of errors is unfounded. Now you want to silence me.Chjoaygame (talk) 07:31, 23 September 2013 (UTC)

examples in new lead
The examples in the new lead are specialized and inappropriate.Chjoaygame (talk) 07:11, 23 September 2013 (UTC)

a different article
I can see that Editor Prokaryotes is resolutely determined and unreasonably violent in his Wikipedia editorial way of pushing of his point of view, and deeply muddled in this mind over the logic of the various kinds of radiative equilibrium. He has practically destroyed the logic of the article as it stood before his invasion. He has created a nearly new and nearly incurably muddled article on a different topic. I do not have time or inclination to struggle against his kind of editing practices.Chjoaygame (talk) 09:44, 23 September 2013 (UTC)

Approximate radiative exchange equilibrium
The section in the article on approximate radiative exchange equilibrium is to some degree inappropriate, and now that editor Prokaryotes has drawn my attention to it, I am removing it.Chjoaygame (talk) 07:10, 23 September 2013 (UTC)

Remove of tone notice
Can we remove that page notification now? I reworked most of the article, removed repeats, weasel wording, errors and reconstructed the topic to better reflect the science. Prokaryotes (talk) 07:59, 23 September 2013 (UTC)
 * This revision shows the version prior to my edits: https://en.wikipedia.org/w/index.php?title=Radiative_equilibrium&diff=574148574&oldid=550050676 Prokaryotes (talk) 08:08, 23 September 2013 (UTC)

RfC; this article has rapidly been changed, from an account of the various physical notions of radiative equilibrium, to an expression of some ideas in climate theory
This article has rapidly been changed, from a more or less systematic account of the various physical notions of radiative equilibrium, to an expression of some ideas of climate theory. Is this the way the article should go?Chjoaygame (talk) 19:49, 23 September 2013 (UTC)
 * The article is in better shape now has less errors, what you call expression of ideas is referenced. I wonder to what degree you are at fault for all the errors you maintained on this article over the years. Prokaryotes (talk) 06:16, 24 September 2013 (UTC)
 * You may not be too pleased with each other, but the end result of your battles is a good article. Campoftheamericas (talk) 07:47, 25 September 2013 (UTC)
 * I agree, that article looks reasonably good right now. There is enough room in this article for both the physical notions of radiative equilibrium and and pointing out applications of the topic, such as in climate modeling. From my own POV, it would be nice to strengthen ties of this article to other topics, like radiative transfer and radiative convective equilibrium, although I don't think we have a general article on the latter topic yet. I urge the editors of this article to remain civil. No WP article is any single editor's 'fault' and we all have the shared goal of improving coverage. Thanks to both of you for your efforts. --Mark viking (talk) 11:53, 25 September 2013 (UTC)

I am inclined to agree with you. This article is about the general topic. The stuff that Prokaryotes has added to the lede is garbled and mangled William M. Connolley (talk) 21:26, 25 September 2013 (UTC)
 * , want to start by discussing a single edit? Campoftheamericas (talk) 22:01, 25 September 2013 (UTC)


 * I would like to discuss the second sentence in the first paragraph, which is awkwardly worded:
 * In atmospheric physics the definition to derive radiative equilibrium is, total flux F is constant with depth.
 * Shouldn't this say either "definition of radiative equilibrium" or "derivation of radiative equilibrium" or maybe "formula for radiative equilibrium"? Or did you mean:
 * In atmospheric physics, in the definition of (or derivation of, or formula for) radiative equilibrium, total flux F is constant with depth. (This comment was added unsigned at 04:35, 12 October 2013 by User:Anne Delong.)


 * Comment The point of the RFC is unclear to me and I have not gone into the history. I am disinclined to do so in the light of the discussion so far, but certainly the current wording of the lede paragraph is incoherent scribbling and the line of discussion is no better than handwaving. ("It is a kind of dynamic equilibrium" -- "the net change in the tropopause after temperatures readjust to radiative equilibrium in the stratosphere, is used to determine the radiative forcing, which assess natural and anthropogenic climate change"!!! I ask you! Whose idea of encyclopedic writing is that?) If you folks can agree on what it is you want the article to say and what those on each side of the discussion want the other lot to say or want the article to say, then I might take a closer look. Just for a start, try to separate the concerns into separate sections, word them properly (use really short, carefully checked sentences) and then to integrate them into something coherent. Before something of the kind looks like taking off, some of us have better things to do. JonRichfield (talk) 07:28, 12 October 2013 (UTC)


 * I tend to agree with User:JonRichfield here. Radiative equilibrium is simply the state where a system is losing as much energy by radiation as it is gaining by radiation, either as a total system or throughout its bulk.  The current lead paragraph is extremely confusing, and is in fact completely incorrectly worded in places:
 * "radiative equilibrium is a steady state system" is completely incorrect. Radiative equilibrium is not a system, it is an attribute of a system.
 * "dependent on a constant energy flux and energy absorption of electromagnetic radiation." is only correct for discussions of radiative equilibrium throughout a bulk medium, not (for example) a solid surface of negligible thickness under radiative equilibrium (thermal radiation from the surface is equal to radiation absorbed by the surface.) A good statement of this state is "The net radiative heat flux to a surface that is in radiative equilibrium, or radiatively adiabatic, is zero." [from "Pressure Relieving Systems for Marine Bulk Liquid Cargo Containers"]
 * "the definition to derive radiative equilibrium" is an extremely confusing turn of phrase, and the statement that "flux is constant with depth" is only true for symmetrical systems, like stellar atmospheres. Consider for example a cube, made of a perfectly insulating grey anisotropic medium, bounded on each face by a black body surface, each of which is at a different constant temperature. Here the flux is not constant with depth, even after radiative equilibrium is achieved.
 * The sentence "It is a kind of dynamic equilibrium." is completely out of place in the paragraph. I could imagine it near the start: something like "Radiative equilibrium is a kind of dynamic equilibrium where the radiative energy entering a system equals the radiative energy leaving the system." but certainly not on its own like that inbetween other sentences.
 * The sentence about atmospheric science really needs to be rewritten. As it stands, it is only comprehensible after a whole lot of previous material is presented. We need a sentence which simply explains the basic importance of radiative equilibrium in atmospheric science: leave the discussion of tropopause effects to the body of the article. --Slashme (talk) 21:46, 14 October 2013 (UTC)

I've changed the first sentence to more clearly define what radiative equilibrium is, with a reference to a recent book on the subject. --Slashme (talk) 22:21, 14 October 2013 (UTC)
 * Well that is a start. At least the lede is now grammatical and coherent. If this is one of your fields of interest, don't let anyone put you off proceeding with the rest of the article. If not, I hope that a few of the others involved will take inspiration from that example. JonRichfield (talk) 18:14, 15 October 2013 (UTC)

Pointwise radiative equilibrium
How relevant is the term "pointwise"? Isn't pointwise equilibrium the same as just equilibrium? Also i recently removed this part from the section "Pointwise radiative equilibrium is closely related to Prevost's absolute radiative equilibrium", because it was unsourced and i think it is enough to mention his studies in the history part (which is new). And he referred to fluids... The section could be improved further.

Prevost wrote: "RADIATION AND ABSORPTION. Absolute equilibrium of free heat is the state of this fluid in a portion of space which receives as much as it allows to escape it." Page 6 http://archive.org/stream/lawsofradiationa00bracrich/lawsofradiationa00bracrich_djvu.txt  Prokaryotes (talk) 06:32, 25 September 2013 (UTC)

this article still a wreck beyond piecemeal repair
This article remains a wreck made by an editor who thought he could improve it, and rejected other views. I have not tried to fix the wreck, which is beyond piecemeal repair.Chjoaygame (talk) 03:50, 6 August 2015 (UTC)


 * I have reverted to an earlier version. I think this article should attend to the basic radiative concepts, not try to supply information about meteorology.Chjoaygame (talk) 18:37, 28 January 2016 (UTC)


 * Dear Editor DavidMarsh2016, you can offer as many excuses as you please, and you can use the freedom given in talk pages to act as you have, by force. But your actions, for example deleting my talk-page comments, remain unethical. That you are a new editor does not excuse your actions. You may be happy to know I do not care, or have time, to chase this up, but you may also know that I disapprove of them.Chjoaygame (talk) 14:24, 29 January 2016 (UTC)
 * You seem to have a habit of calling other editors such words as violent or unethical or implying they are rude or they are pointlessly offering up excuses as if they are in any way answerable to you.  It ¨should be perfectly ok for an editor to tidy up the comments when the comments are no longer relevant and are only wasting the time of other readers as ours have done.  DavidMarsh2016 (talk) 00:51, 30 January 2016 (UTC)Davidmarsh2016

Disambiguate Absolute radiative equilibrium from relative radiative equilibrium
If the two ideas are kept separate then the page becomes much easier to understand. Alternatively since absolute radiative equilibrium is a balance without regard to anything else at all and is therefore more of a very simple arithemetical idea rather than a complex thermodynamic one, just describe what it is with respect to planetary equilibrium temperature and direct people to that page

Although the idea of 'planetary equilibrium temperature' sounds totally wrong from the point of view of thermodynamics the idea is a very long established one going back to Prevost himself. DavidMarsh2016 (talk) 20:23, 28 January 2016 (UTC)DavidMarsh2016


 * It seems you have well researched and understood ideas on the subject matter. You are of course free to edit those ideas into the page.Chjoaygame (talk) 22:04, 28 January 2016 (UTC)

Radiative balance note
I just reverted an IP edit that added a parenthetical comment that radiative equilibrium can also be called radiative balance. That's not true: wikt:radiative balance is how much more energy is coming in vs going out of a system by radiation. --Slashme (talk) 07:01, 17 February 2017 (UTC)

Contradiction
This page contradicts itself:

"Radiative equilibrium is the condition where the total thermal radiation leaving an object is equal to the total thermal radiation entering it."

- vs. -

"This means that, at every point of the region of space that is in (pointwise) radiative equilibrium, the total, for all frequencies of radiation, interconversion of energy between thermal radiation and energy content in matter is nil (zero)."

The first statement subscribes to the Prevost Theory of Exchanges (a Caloric Heat-based model first promulgated in 1791 which treated radiation as a rarefied material substance, and placed upon the midden heap of scientific knowledge by none other than James Clerk Maxwell, who convinced the scientific community to subscribe to the Kinetic Theory of Heat), which makes the claim that all objects above 0 K emit regardless of ambient energy density or the existence of other objects in line-of-sight of the emitting object.

In reality, 2LoT holds even on a per-interaction radiative exchange basis.

At thermodynamic equilibrium, the Helmholtz Free Energy is zero: F = U - TS Where: F = Helmholtz Free Energy U = internal energy T = absolute temperature S = final entropy TS = energy the object can receive from the environment

If U > TS, F > 0... energy must flow from object to environment. If U = TS, F = 0... no energy can flow to or from the object. If U < TS, F < 0... energy must flow from environment to object.

If U = TS, p_photon = u/3 = p_object, energy cannot flow because no work can be done. Photon chemical potential is zero.

Let's look at the Stefan-Boltzmann equation: q = ε σ (T_h^4 - T_c^4) A_h

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1 P/A = ε σ T^4 = c/4 * Energy density Energy density = 4/c σ T^4

At 303.15 K, energy density is 0.6384870391162539e-5 J/m^3. At 287.64 K, energy density is 0.51751020211456733e-5 J/m^3.

It requires energy (an energy gradient) to perform work, to provide the impetus for any action... in the case above, it would require external energy performing work upon the system to force energy to flow against an energy gradient of 0.12097683700168657e-5 J/m^3.

The above is why the Prevost Theory of Exchanges is an outdated model of energy exchange.

71.135.41.65 (talk) 23:24, 30 January 2021 (UTC)

Bad link...
Reference #5 is a dead link: Mihalas, D., Weibel-Mihalas, B. (1984). Foundations of Radiation Hydrodynamics, Oxford University Press, New York ISBN 0-19-503437-6.

Here's an updated link: https://www.sciencemadness.org/lanl1_a/lib-www/books/00418557.pdf 2606:1A40:1002:0:1978:639B:DE36:9075 (talk) 21:02, 16 May 2022 (UTC)