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 Prévost. 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 Prévost 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 Wikipedia:No original research, and is not a reason to edit the Wikipedia.Chjoaygame (talk) 23:33, 26 September 2010 (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?

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.