Misplaced Pages

Revision as of 06:40, 15 December 2005

General discussion

I'd like to rewrite the overview. It has no relevance to thermodynamics as a subject, and dwells on thermodynamics as a college class. I will do this now, and if there is a problem with what I do, please let me know before reverting it. Thank you. Lagrangian

Why did user CDC revert my edits to this page (as 129.170.x.x)? I am attempting to transform the page into a more logically coherent sequential exposition of the basics of thermodynamics and its relationship to statistical mechanics, and I can't for the life of me figure out why my edits were reverted. 64.222.115.30

Vhung wrote what looks like a brand new Thermodynamics article. Why? Why not try to adapt the old one, or, if the old one is irremediably bad, why not move it to a /Talk page? Basically, we don't want to have to vote about which version is the best. That's not the wiki way... --LMS 0th-law:

• It is possible to build a thermometer.
• That is: If objects A and B are

in thermal equilibrium with each other, and objects B and C are in thermal equilibrium with each other, then objects A and C are also in thermal equilibrium with each other.

• Two objects are in thermal equilibrium

with each other, if their macroscopic properties, such as electrical resistance or volume, do not change with time when these objects are brought into thermal contact with each other.

Excised old version

1st-law:

• Convervation of Energy

2nd-law:

• Degradation of Energy (irreversibilities)
• "Nothing goes without loss"
• concept of Entropy (s)
• T.ds = du + p.dv
• T.ds = dh - v.dp

In lay terms,

• You can't win.
• You can't even break even.
• And you can't get out of the game.

3rd-law:

• At absolute zero, the Entropy of a Perfect crystal is zero.

Would it be unfair of me to suggest that this page requires some serious refactoring?  :-) --LMS

Refactoring thermodynamics is best attempted by madmen or fools, or by foolish madmen such as Clifford Truesdell.

There should be a reference to the relationship between Thermodinamics and Statistical Mechanics

Rephrased second law. I am very wary about making statements that involve the entire universe.

I don't like the version of the third law given here. I just did a search on the Internet, and it looks like it's fairly popular, but I have no idea why. The first thing someone's going to say when they see it is "who cares about perfect crystals". What about

All processes cease as temperature approaches zero

or

Absolute zero can only be approached asymptotically

I also don't like the ones that say S(T=0)=0, because in the usual derivation of the third law, S(T=0) is a constant, which is set to zero merely for convenience. It's similar to the way you can set gravitational potential energy at r -> ∞ to zero.

If no-one answers, I'll just change it. -- Tim

Okay, no-one answered. It's changed. -- Tim Starling

"If A and B are at the same temperature, and B and C are at the same temperature, then A and C are also at the same temperature."

Actually, I'm under the strong impression that the zeroth law is: "If A and B are in thermal equilibrium, and B and C are in thermal equilibrium, then A and C are also in thermal equilibrium."

The way it is written down now, the zeroth law becomes a trivial fact. Since '=' is an equivalence relation, 'having the same temperature' is necessarily transitive. If no-one disagrees, I'll change the definition shortly. (More information can be found in Status_of_the_zeroth_law_of_thermodynamics.) --Victor Gijsbers

Quite so, well spotted. I like your new article, but note that you don't need to put underscores in links, so ] is fine. Also, although titles are case sensitive, the first letter is automatically capitalised, so ] goes to the right place too. See Misplaced Pages:How to edit a page. -- Tim Starling 23:46 7 Jul 2003 (UTC)

Ok, thanks for the tip. --Victor Gijsbers

Current statement of the third law: "All processes cease as temperature approaches zero."

This is not only wrong, it is positively meaningless in the context of thermodynamics. In this theory, temperature is defined for equilibrium states only (the theory only talks about equilibrium states), so no processes take place whenever a temperature is defined, not just at absolute zero. Something along these lines could perhaps be the 3rd law of statistical mechanics, but it cannot be a law od thermodynamics.

I suggest replacing it by Buchdahl's (1966, The concepts of classical thermodynamics) formulation: The entropy of any given system attains the same finite least value for every state of least energy. --Victor Gijsbers

How about, The entropy of a system reaches some finite minimal value for every state of minimal energy. Pizza Puzzle

You say that the idea of a change or process taking place is absolutely meaningless. This is incorrect, indeed the bulk of any undergraduate level thermodynamics course deals with precisely such processes. This is done formally by defining a process as being a succession of infintesimally separated equilibrium states. This is called a "quasistatic" process. There is no time variable as such, instead relationships between various thermodynamic properties are calculated. I'm taking this from Chapter 1 of Sears & Salinger, by the way.

The statement of the 3rd law I was paraphrasing (again from S&S) is:

It is impossible to reduce the temperature of a system to absolute zero in any finite number of operations

It's true that I allude to the presence of a time variable, but I do this to maintain comprehensibility. I don't believe it significantly affects the accuracy of the statement. After all, I don't define the word "cease" -- I could easily make up a definition on the spot which fits in with the quasistatic picture.

The advantage of this statement is that a lay-person can understand it. A person not trained in thermodynamics has very little conception of it means for entropy to approach zero. "You can't cool something to absolute zero" is a statement that your Mum would understand, and it is sufficiently rigorous at the level of this article.

An alternative statement, again saying exactly the same thing, is this:

The derivative of temperature with respect to any macroscopic property, with entropy held constant, is zero when temperature is zero.

But please, save it for an article with a more advanced target audience. Specifically, save it for third law of thermodynamics, where a proper explanation can be given of such complexities.

-- Tim Starling 14:16 8 Jul 2003 (UTC]

The statement that "all processes cease as the temperature approaches zero" is not even true (and hence it cannot be a proper statement of the 3rd law). For example, one could take a zero-temperature Fermi gas and allow it to undergo an isothermal expansion process, doing p dV work. I am removing the erroneous statement. 67.186.28.212 01:48, 8 September 2005 (UTC)

Sorry, I missed this comment, saw no edit summary and reverted as vandalism. I'll revert myself now. El_C 02:05, 8 September 2005 (UTC)

Can someone explain to me the reason the edits of 129.170.29.119 are unacceptable? PAR 22:03, 7 Apr 2005 (UTC)

1st Law

"The sum of heat flowing into a system and work done by the system is zero. " - No, non-zero heat may flow into a system (e.g. a metal bar) but the system do no work. It might just get hot.

Perhaps the more standard "The heat flowing into a system is equal to the change in internal energy minus the work done by the system." would be better.

Oops. Good point, sorry. -- Tim Starling 09:40, 31 Aug 2003 (UTC)

"The work exchanged in an adiabatic process depends only on the initial and the final state and not on the details of the process. " - What is "work exchanged"? You obviously have a context in mind here but it is not spelt out. Anyway, work is "done", not exchanged.

Quite so. Those alternate statements were added by Reddi, I didn't really pay much attention to their accuracy. He claimed to get them out of physicsworld.wolfram.com, maybe there was a bit of paraphrasing going on there as well. See for a pre-Reddi revision. -- Tim Starling 09:40, 31 Aug 2003 (UTC)

They are from physicsworld.wolfram.com (and can be cited from other sources). JDR

The way I remember this stuff, just like the zeroth law is a statement about the existence of a transitive thermodynnamic equilibrium and can be used to define temperature, the first law (as it is stated) requires an explanation of what is meant by heat transfer (or absence thereof: adiabatic) and can be used to define work. I need to research the details so I can add it to the article. — Miguel 03:15, 2004 Feb 26 (UTC)

Without context information, it's not clear (to me) that the "entropy" version is really the same as the 1st law. I think that you need to clarify this statement.

2nd Law

I think that the laws as stated on this page need some work.

The 2 versions of the zeroth law are too similar. Please pick one.

I think I left them because I was trying to avoid pissing Reddi off for the fifth time in one day. Obviously I should have paid a bit more attention. -- Tim Starling 09:40, 31 Aug 2003 (UTC)

Don't worry about that JDR

Have already posted comments on 1st law

"A system operating in a cycle cannot produce a positive heat flow from a colder body to a hotter body " - so how does a refrigerator work?

By using external work. The right statement is "A system operating in a cycle without using external work..." Miguel 03:17, 2004 Feb 26 (UTC)

See Lord Kelvin's work in Thermodynamics ...

"A system operating in contact with a thermal reservoir cannot produce positive work in its surroundings" - Does this mean that a steam engine doesn't work?

See Rudolf Clausius work in Thermodynamics ...

Delete them all and join me in the fun pastime of Reddi watching - see User:Tim Starling/Reddi watchlist. He's made a few edits outside Nikola Tesla recently that I didn't bother checking up. Welcome to Misplaced Pages, Sokane. Please sign entries on talk pages with ~~~~, which is automatically converted to a name and a date. Note that you don't need to use <p> here, just pressing enter twice does the trick. I'll put a few more tips on your user talk page. -- Tim Starling 09:40, 31 Aug 2003 (UTC)

1st, don't delete the factual info ... 2nd, Have you updated that list lately? =-D JDR

We have: "The entropy of a closed macroscopic system never decreases". Shouldn't this say "isolated" since we are giving the system theoretic definition: "closed systems: exchanging energy (heat and work) but not matter with their environment". I have changed this to "thermally isolated" as in the Entropy article. Physics texts usually define "closed" to mean "thermally isolated". I came here because of a discussion with someone who was using the statements in this article to argue that the Earth is essentially a closed system so it's entropy must increase.

Whether the Earth is a closed system depends on the level of approximation. The Earth's atmosphere loses hydrogen and gains small amounts of matter from solar wind, the interstellar medium and meteorites. It also exchanges work on other celestial bodies (notably through lunar and solar tides). Finally, the Earth clearly exchanges heat with its "environment" - it radiates energy away as a black body because it is hotter than the CMB. The energy radiated should (on average) match that absorbed from solar radiation, resulting in net entropy production. The Earth is also not in local equilibrium internally, so entropy gets constantly produced. — Miguel 03:58, 2004 Oct 5 (UTC)

The article defines 'closed system' as a system that exchanges but energy but not matter with its surroundings. This is BTW the standard definiton in textbooks for physical chemists. Using this definition the statement 'The entropy of a closed system never decreases' is clearly wrong. Any cooling lump of matter that is neither gaining or loosing material to its surroundings is clearly: A) a closed system by the definition used; B) is decreasing its entropy (by giving out heat to its surroundings). The statement should be changed to 'The entropy of an isolated system never decreases'. RistoP

I concur, and therefore I have changed it to "isolated system." Ed Sanville 01:12, 12 November 2005 (UTC)

Time

User:Moink said "took out "thermodynamics is not concerned with time"... not true in my experience". It's true in my experience. In all my time studying thermodynamics and statistical physics, I don't think I saw a single t. Time is mentioned obliquely -- for example it's often noted that a Carnot engine would take an infinite amount of time per stroke. But the statement you removed was, I felt, quite accurate. Can you explain? -- Tim Starling 06:03, Jan 13, 2004 (UTC)

Think about the second law of thermodynamics: Entropy increases with time. If that's not a dynamic law I don't know what is. Almost all the thermodynamics I've ever done (I'll admit it is not my central field, fluid dynamics is) has included time in some way or another. Here's a problem for you: A reservoir is separated into two cells with a thermally insulating membrane. The temperature on side A is 400K, on side B is 100K. The membrane is removed. What is the resulting temperature as a function of space and time? If you agree that this is indeed a thermodynamic problem, then we can say that thermodynamics is more than thermostatics. moink 22:29, 13 Jan 2004 (UTC)

Thermodynamics uses time qualitatively, but not quantitatively. This is the fundamental point the original author was trying to make. The question of temperature as a function of space and time is not thermodynamics. The question of entropy differences between initial and final states is thermodynamics. The term "thermostatics" reminds me of quasistatic equilibrium, and interesting concept in itself. -- Tim Starling 23:23, Jan 14, 2004 (UTC)

If that's the point the article is trying to make, it doesn't make it very clearly. And I disagree that the study of flow with temperature changes is not thermodynamics. This article states that "Thermodynamics is the study of energy, its conversions between various forms..." and if a viscous flow with temperature differences is not a study of the conversions of energy between forms, I don't know what is. moink 22:29, 15 Jan 2004 (UTC)

I don't think specific mechanisms of heat transport such as conduction or convection are considered part of thermodynamics. -- Tim Starling 00:25, Jan 16, 2004 (UTC)

I've taken a class called "thermodynamics" and one called "fluid dynamics". We never took time into consideration in thermo, but we did do the problem Moink suggested in fluid dynamics. I think thermo tells you what a system tends to do, but not how it does it.

I think part of what's going on here is that most people have taken only an introductory thermo course. Introductory courses tend to deal only with equilibrium states, mostly because they're easier to solve for beginners, and also because solving for an equilibrium state gives you quite a bit of valuable information. But I do think thermo, in its more advanced incarnations, does deal with how it gets there. moink 22:15, 16 Jan 2004 (UTC)

I've studied thermodynamics, kinetic theory and statistical physics to third year level as a physics major. All up I've done about about 50 hours of lectures on the subject. -- Tim Starling 10:44, Jan 17, 2004 (UTC)

Could this be pointed out in the article? JDR

Maybe not heat convection and conduction, but definitely transferring energy between types, like heat to velocity. moink 22:15, 16 Jan 2004 (UTC)

Velocity is more the domain of kinetic theory not thermodynamics.

From Sears & Salinger chapter 1-1:

Thermodynamics is an experimental science based on a small number of principles that are generalizations made from experience. It is concerned only with macroscopic or large-scale properties of matter and it makes no hypotheses about the small-scale or microscopic structure of matter. From the principles of thermodynamics one can derive general relations between such quantities as coefficients of expansion, compressibilities, specific heat capacities, heats of transformation, and magnetic and dielectric coefficients, especially as these are affected by temperature. The principles of thermodynamics also tell us which of these relations must be determined experimentally in order to completely specify all the properties of the system...

Thermodynamics is complementary to kinetic theory and statistical thermodynamics. Thermodynamics provides relationships between physical properties of any system once certain measurements are made. Kinetic theory and statistical thermodynamics enable one to calculate the mangitudes of these properties for those systems whose energy states can be determined.

-- Tim Starling 10:44, Jan 17, 2004 (UTC)

Phenomenological study of time-dependent phenomena such as fluid mechanics or chemical reaction kinetics is separate from kinetic theory or statistical mechanics. Just like in thermodynamics on can introduce a phenomenological "heat capacity" whose value can be calculated from first principles using statistical mechanics, one can introduce a phenomenological "heat conductivity" whose value can only be calculated using kinetic theory. See my stub on non-equilibrium thermodynamics for more on this. Miguel 03:26, 2004 Feb 26 (UTC)

I think the issue is almost a semantical one with the occasional more generalized usage of "thermodynamics" to exclusively mean "equilibrium thermodynamics". But both "equilibrium thermodynamics" and "nonequilibrium thermodynamics" contain the word thermodynamics, so it doesn't seem quite right to claim that time is not involved in thermodynamics. Even introductory thermodynamics courses typically deal with things like heat transfer rates, so I don't think it's an educational level issue so much as a semantical one. Perhaps the divide between the two can be explained more clearly without excluding time from thermodynamics. — Cortonin | Talk 10:53, 24 Mar 2005 (UTC)

The quality of the article

I am actually surprised to see that the article's quality has decreased (in my very humble opinion) since I was last involved with it about a year ago. The presentation has lost all coherence and it reads just like a collection of equations!

I think some discussion needs to take place as to what exactly we want to emphasize about thermodynamics. — Miguel 20:03, 2005 May 19 (UTC)

• • I agree, the artile reads like a pasted collection of randomness. As no one has taken responsibility to clean this article, I will begin to do so. If anyone cares to help, don't hesitate. Thanks: --Wavesmikey 04:02, 13 September 2005 (UTC)

• • • When I first visited this article long ago, it was just a terrible pile of random bits about each of the three laws of thermodynamics, as if the three laws, (and various random jokes/analogies), were all there is to thermo. Given that I have and had little time to do major overhauls to articles, I instead decided to add sections on the thermodynamic parameters and potentials, which are the cornerstones of thermodynamics in practice, (and weren't even mentioned in the article at the time). I agree that this article is one of the worst articles on a huge, broad topic, but unfortunately I'm not good enough with thermo/teaching in general to put together a good encyclopedic piece. Good luck to you wavesmikey! Ed Sanville 05:36, 13 September 2005 (UTC)

Thanks for the encouragement! Thus far I've smoothed over the introduction, added a history section, added a joke, added an attachment (to Carnot's seminal 1824 paper), and added some external links. If management would like to now remove the clean-up tag, I would be grateful (I will continue to smooth-over the article as time goes on). If anyone has any suggestions as to where futher improvement is needed I would be happy to oblige. Please leave comment here or on my talk page. Thanks: --Wavesmikey 06:17, 13 September 2005 (UTC)

I've started to get this article moving somewhere again. It's going to take alot of work. Karol 21:44, 28 October 2005 (UTC)

The drawing showing cold photons and hot photons is beautiful but misleading. Individual photons (like individual molecules in a gas) have energy, but do not have temperature. The radiation from the sun have the temperature of the surface of the sun. The steady-state temperature of the planets is determined by the condition that the influx of energy from the sun to the planet equals the outgoing radiation from the planet to the universe. Bo Jacoby 09:48, 23 November 2005 (UTC)

I agree, hot and cold photons are not a good concept. The image is misleading, and not relevant to the discussion. The whole discussion of thermodynamic evolution should be in a separate article, not in the thermodynamics article. I will move it soon if nobody objects. PAR 10:28, 23 November 2005 (UTC)

Very true. Karol 14:17, 23 November 2005 (UTC)

The section has been moved to Thermodynamic evolution including the above discussion on its talk page. PAR 04:07, 25 November 2005 (UTC)

• I agree with everyone generally; I was the one that designed the image and wrote the article out of impulse being that I think this concept is a big part of thermodynamics presently. Every new textbook or related book that comes out lately has at least one chapter on the thermodynamics of evolution. Regarding the diagram, I based it on one similar, but without Pluto, as found in Schneider & Sagan’s 2005 Into the Cool – Energy Flow, Thermodynamics, and Life. I will admit that when I first read the book, the idea of a “cold photon” didn’t really make a lot of sense to me, and I thought the diagram was a bit dumbed-down. Yet, over the past couple of months the diagram has grown on me a bit even if it is not word-for-word accurate. If someone has a better way to contrast the photons to either side of the earth, then please let me know and I will up-load a new diagram.

• I thought of maybe using high and low frequency, but that doesn’t seem to be as visually appealing. If we want to stick with the hot/cold idea, although technically it’s not perfect, we can define temperature as:

      Temperature: a measure of the tendency of an object or system to spontaneously give up energy. 

• (textbook)]. Thus, we can think of the region of space towards the sun as being in possession of the ability to give up energy, if it were to come into contact with another adjoined system. And as the energy portion of the universe can be defined as predominately the four fundamental forces, that is according to Nobelist Martinus Veltman (Book: Facts and Mysteries in Elementary Particle Physics (2003)], we can think of the photons towards the sun as being in possession of more energy, and hence hotter in a loose sense of the term. More than this, no one really knows what a photon is in essence? Of all the explanations on the double slits experiments that I have every read no one has an answer. And no one for the past 40 years has been able to explain why light (i.e. photons) shined on ultra cold liquid helium subjected to voltage functions to increase current. Thus, if anyone has more appropriate terminology I will be glad to amend the diagram. Thanks:--Wavesmikey 04:26, 26 November 2005 (UTC)

I don't think the photons coming from the sun have a lower frequency out near Pluto. The sun looks the same color out there, after all. I think the flux of photons is simply lower out there. Ed Sanville 16:20, 26 November 2005 (UTC)

Thermodynamic Evolution (section moved)

for discussion see: talk:thermodynamic evolution

Resectioning

I have switched sections around, hopefully putting first things first. The only actual changes that I made was to put the different types of thermodynamics (e.g. biological) into the see also section, and I move the history to the history page. I know that we should have a small history section here, so I didn't intend that move to eject history entirely, I just don't know what the small amount should be.

I would like to start modifying the first section or two in order to describe things from the ground up, more or less, developing the idea of system, then parameters and state, and then really define the parameters by describing thermodynamic instruments, thermometer, barometer, etc. I will wait and see if this resectioning flies first. PAR 14:45, 27 November 2005 (UTC)

Well it has my Seal of Approval (for what it's worth) :) Long overdue. DV8 2XL 14:49, 27 November 2005 (UTC)

I was going to move the history section tomorrow myself. I already have the paragraph in mind that I am going to use. It will start with Robert Boyle and how he invented the pump with which he noticed the pressure-temperature correlation. From here a bone digester was built . From here a release valve was implemented to keep the machine from exploding. And by watching the steam valve move rhythmically up and down the concept of piston and cylinder was conceived (Denis Papin). Then Savery built the first engine . Finally, in 1824, the father of thermodynamics Sadi Carnot published “Reflections on the Motive Power of Fire”. Does this sound ok to everyone? P.S. leave the potential section for me, I am going to write a short paragraph on potentials and move the rest to the potential page. Also, I don't think "instruments" is big focal point in thermodynamics; it's theory that's important. A small bit will be ok thought.--Wavesmikey 19:00, 27 November 2005 (UTC)

I did some more work today. The article is getting kind of long so I shortened and merged a few sections; I would suggest doing the same with the tools section - i.e. write a little mini-tools section and then connect a link to a main thermodynamic tools page. Also, this one paragraph:

Thermodynamics is difficult to grasp in a linear fashion. Each concept seems to require the understanding of some other concept, which ultimately refers to the initial concept for its complete explanation. The best way to understand thermodynamics is to go through the development of its concepts and principles, without expecting to understand them thoroughly on the first pass. Then, as certain concepts become more clear, others will fall into line. Accordingly, the following article will not develop ideas in a linear fashion, with each idea explained in terms of preceeding ideas. Certain concepts will be introduced without explanation, and will best be understood only upon re-reading the article.

sounds a little soft and fluffy; it kind of sounds like were giving the reader instructions on how to read an encyclopedia? I'd do some trimming on this one.--Wavesmikey 09:19, 29 November 2005 (UTC)

About the tools part - maybe you're right.

About the above paragraph - Rewriting things, it was just bothering me that it was difficult to explain anything without assuming something else had already been explained. I think some remark should be made about that. If you can express it less "soft and fluffy", please do. PAR 13:04, 29 November 2005 (UTC)

I must say that I really like the direction this article (group of articles, in fact) is going! Karol 09:47, 29 November 2005 (UTC)

Thanks Par and Karol. I am going to do main articles and mini-sections for the whole thermodynamics article if nobody objects? It seems to be getting kind of long and I think mini articles would be a nice read; where if the reader wants further information they can click to the main article. Talk later, --Wavesmikey 19:56, 29 November 2005 (UTC)

Homogenizing Article

I'm going to begin trying to bring uniformity to the article; and then remove the clean-up tag for awhile if no one objects?--Wavesmikey 04:46, 30 November 2005 (UTC)

Sounds good, but go piece by piece, ok? PAR 05:36, 30 November 2005 (UTC)

That's fine with me; we can always revert any changes. Temporally, I removed the following from the intro:

In particular, the entropy of a system exchanging no heat with the outside can never decrease with time. As such, entropy allows predictions on the transformations and energy exchanges that are accessible to a given system. Related to entropy, Statistical mechanics or statistical thermodynamics is one of the underlying theories that sustain thermodynamics; it provides a way to predict the entropy of a thermodynamic system, based on the statistical analysis of the fluctuations the system experiences over a set of microstates

I feel that it is too much for the intro; I feel the intro should represent the typical first five chapters of a general thermodynamics text book (which I have many of). Somehow, I feel the above section needs to be filtered in somewhere? Going to work on the third section now (parameters)--Wavesmikey 07:00, 30 November 2005 (UTC)

Happy Article

Thank-you for all who have helped on this article over the last couple of months! I gave it a good overhaul. You will find that I moved a lot of writing to its own page and connected those pages with short summaries. I hope I helped; it feels clean to me (for the moment). Adios: --Wavesmikey 09:25, 30 November 2005 (UTC)

Hey Wavesmikey - very good job, thank you. (Of course I disagree with some aspects) By the way, on that joke - the way that anon wrote it was the way I have heard it, but getting the jokes right is not a big priority with me. PAR 04:55, 2 December 2005 (UTC)

You’re welcome, it took me the good part of a day to do it. Also, you're right about the joke (although the one there now is funnier); after I deleted it, I then returned and moved it to the Quotes & humor (thermodynamics) page, plus I added a good quote, and organized that page. Talk later:--Wavesmikey 19:12, 2 December 2005 (UTC)

This article now looks about 10 times better than it did at the beginning of this year. We can debate the specifics of the layout, and expand on the sections, but I think we're on the right track now... Ed Sanville 07:01, 2 December 2005 (UTC)

Yes, and thank-you; but let’s do expanding and layout changes gradually with conciseness being a focal point. Talk later:--Wavesmikey 19:12, 2 December 2005 (UTC)

4th thermodynamic principle

An interesting thing about this article is that it has evolved through a process of original collaborative research towards an astute clarification of the principles of thermodynamics in words, not simply formulas. However there still seems to be the matter of time implied by the 2nd law. This has been taken up in the proposed 4th law, which I have attempted to add to the article previously. There is at least one scientist who has said that "maximum empower" is generally accepted as the 4th principle of thermodynamics. I would therefore like to add the following in the section on laws

• Fourth principle of thermodynamics

Designs prevail that maximize empower.

Sholto Maud 06:30, 4 December 2005 (UTC)

Until you can write down an experimental technique to quantitatively measure "empower", and then write down mathematical equations that demonstrate an experimentally testable relationship of "empower" to other thermodynamic variables, I am opposed to this. PAR 08:16, 4 December 2005 (UTC)

PAR does this mean you require the specification of an instrument that will measure "empower"? Sholto Maud 10:39, 4 December 2005 (UTC)

ABSOLUTELY. If "empower" cannot be measured, then it has no scientific significance whatsoever. A detailed specification is not necessary, just enough to see the possibility.

As for the mathematical equations, C.Giannantoni (2002, The Maximum Em-Power Principle as the basis for Theromodynamics of Quality, Servizi Grafici Editoriali, Padova.) has given equations. I'm not sure I can verify them re: experimentally testable relationship of "empower" to other thermodynamic variables. Sholto Maud 09:31, 4 December 2005 (UTC)

I will try to find this article and read it.

• It is a small book - it appears to be available from http://www.emergysystems.org/books.php. Sholto Maud 10:39, 4 December 2005 (UTC)

Well, I don't want to buy a book, but googling "emergy" was informative. Especially and . As far as I can tell, the concept of empower (emergy/time) was pioneered by Howard T. Odum, and is concerned with the link between energy usage and evolution. With regard to human evolution, it has something to say about energy conservation, energy usage, ecology, and energy economics. Although it appears to be a legitimate concept, I don't think it is quantitatively developed enough to be considered a "hard" science. Its area of inquiry is not that of thermodynamics and therefore does not belong in this article. I think that these ideas should perhaps go into the thermodynamic evolution article. PAR 11:31, 4 December 2005 (UTC)

• This thread has been informative for a number of reasons.

• 1. Perhaps most important is that this thermodynamics article needs a clear statement on what areas of inquiry are that of thermodynamics. Where is the boundry drawn and why?

1.1 For example if "in essence thermodynamics studies how energy instills movement", as stated in the article, then thermodynamics includes areas of inquiry which study how energy instills movement at scales such as organisms, ecological systems and the geobiosphere. Therefore the study of how embodied energy (emergy) instills movement seems to be equally as relevant.

• 2. The article mentions that open systems, open to energy flow, are a class of thermodynamic systems. M.Tribus (1961) Thermostatics and Thermodynamics, Van Nostrand, University Series in Basic Engineering, gives mathematical and instrumental statements of both closed and open systems. On page 619 (§ 16.11), Tribus cites H.T.Odum and R.C.Pinkerton (1955 'Time's speed regulator: The optimum efficiency for maximum output in physical and biological systems ', Am. Sci., 43 pp. 331-343) with respects to 'Generalized Treatment of Linear Systems Used for Power Production' and maximum power. G.Q. Chen (in press) 'Scarcity of exergy and ecological evaluation based on embodied exergy', Communications in Nonlinear Science and Numerical Simulation, p. 16. Notes that maximum power has been proposed as the fourth principle of energetics and open system thermodynamics. How is maximum power (and apparent maximum empower corralary) not a thermodynamic area of inquiry?
• 3. For pedagogic utility, all the main entries on the first 4 laws would benefit examples of how to construct simple instruments that can, A. measure mechanical and energetic power, B. and thereby demonstrate a method by which each law can be verified by anyone - else empirical knowledge of the "laws" are confined only to specialists. Sholto Maud 12:19, 4 December 2005 (UTC)

I agree with 1-thermodynamics needs to be clearly defined - and 3 the instruments need to be defined - see thermodynamic instruments.

However, you have not defined emergy in a quantitative sense. Tell me how to measure the emergy of a glass of water. Something that results in a number. I can tell you how to measure the pressure, the entropy, the temperature, all the thermodynamic variables of that glass of water. I can tell you the relationships between these variables. Tell me how to measure the emergy of a glass of water. Tell me the relationships between emergy and the other thermodynamic variables. Does emergy change with temperature? If so, by exactly what amount? Until you can do this, its not part of thermodynamics. PAR 12:58, 4 December 2005 (UTC)

• I'm glad PAR and I agree on 1. Without the intruments anyone can say anything and concot all sorts of symbolic logic laws about the world. An abstract empower law has just the same status as an abstract zeroth, 1st, 2nd, or 3rd law. Specifications of instruments would be of benefit to many basic science curriculums - ie. wiki entry should say, here are the instruments by which one can demonstrate the laws of thermodynamics so that any average person can understand what is involved in the definition, and what it refers to.

• For example zeroth law should say something like, take three glasses of water all at different temperatures, measured with a mercury (or electronic) thermometer, and connect them with each other. Take a watch (or data logger) and observe what happens to the temperatures over time - record your results at equal time intervals. What is the final temperature? How long did it take. Now try the same experiment with different starting temperatures and try predict how long it will take to reach equilibrium. How accurate was your prediction? Which thermodynamic law did you use to make your prediction?

• In turn, I agree that I have not defined emergy in a quantitative sense. But assuming I could say how to measure the emergy efficiency of a chemical reaction, I cannot do so here because as far as I am aware, with reference to the literature, to do so would constitute Original Research! Which is against the rules of Misplaced Pages. Catch 22. :)

• I would therefore like to swing the attention away from "emergy" and back to "energy". The proposed fourth principle is a statement of the maximum power theorem. Tribus, Chen, Odum and others consider that this has to do with thermodynamics. Indeed load power generated through a load resistor generates a heat and therefore pressure change. So maximum power seems to qualify under the conditions given by PAR. Do you agree PAR? (by the way how do you measure the energy of a glass of water?) Sholto Maud 22:02, 4 December 2005 (UTC)

This is an encyclopedia of established knowledge, and I used to be annoyed by that, but I have come to realize that it has to be that way. Misplaced Pages has no editorial board, no group of appointed referees, so the published literature has to act as a de facto standard. If measuring emergy is original research on your part, then publish it in a reputable peer-reviewed journal, and then you can enter it into an article as established knowledge.

• Agreed. That's why I have not given specifications for an emergy measuring instrument in any of the articles. Sholto Maud 23:32, 4 December 2005 (UTC)

With regard to the maximum power theorem, if this has thermodynamic significance, then please write down the mathematical equation of the fourth principle in terms of established (or newly defined) thermodynamic parameters. All of the other laws can meet this demand, and the fourth must do so as well.

• Ok, I'll see if I can make sense of the Tribus reference noted earlier, and post a summary here (...it may take a while). Sholto Maud 23:25, 4 December 2005 (UTC)

You measure the energy of a glass of water by measuring its temperature and its amount. To a good approximation, the energy is equal to the energy at STP plus the amount times the temperature in degrees celsius. In other words:

${\displaystyle U=U_{0}+NT_{c}\,}$

where U is the energy, U_0 is the energy at STP, N is the amount, and Tc is the temperature in celsius. The energy at STP is the energy at zero degrees celsius, and one atmosphere of pressure. To be any more exact, the measurement process gets more complicated but it is just as precisely defined. Also the properties of water in general must be accurately measured as well, but this is a well defined process too.

• Perhaps this is a semantic quibble, but the example measures the temperature of a glass of water with an instrument (thermometer). The energy of the glass of water is not measured, but is calculated from the temperature measurement. On this basis it appears that emergy, like energy, does not have to be directly measured, but only calculated, in order to be thermodynamically valid. Sholto Maud 23:25, 4 December 2005 (UTC)

No I think its a valid point. Even the thermometer is not measuring temperature, its measuring the volume of a quantity of mercury. The thermometer's scale is then an analog device to "calculate" temperature.

It can be seen that this makes some sense. If you double the temperature, you double the energy above the standard energy. If you double the amount, you double the energy above the standard energy. PAR 23:09, 4 December 2005 (UTC)

• Sholto, I see that you are very intense in your ambition; and there is isolated talk about a maximum power 4th law, and another similar one is maximum efficiency principle (which pulls from the ecological thermodynamics fields), and there are others (about 20 that I know of). The point is that the fourth law is far from agreed upon. Of course there could be some room for some of your writing somewhere in the wiki? But the fourth law is kind of like a joke (at present); if you study thermodynamics decade by decade, i.e. by reading textbook after textbook, you'll notice that it slowly took about 100 years for the main two laws to come into existence. I don't think the 4th law will solidify for at least another 50-100 years. Why don't you write out your main statement or paragraph below so we can all think about your plan. P.S. I collect fourth laws, what is the main book the makes this declaration?--Wavesmikey 06:35, 5 December 2005 (UTC)

• A connoisseur of fourth laws? Impressive!! Perhaps the information revoultion, and a medium like wiki, will reduce the time of evolution for scientific laws, their clear and concise statement, and verification? Most people in the field I have been looking at seem to cite Lotka (1, 2) for the original proposal. Which was then taken up by Odum (4, 5), and most recently given by G.Q. Chen (3). I believe we can see some of the nascent origins further back in the 1600's rationalism of Leibniz, and then the energetics of Mach. M.Tribus (7., § 16.11, p. 619) draws conclusions and variables about maximum power efficiency of thermodynamic steady state from the article by Odum, H.T. and Pinkerton, R.T (4). The statement of the principle appears to have evolved in this literature. First it was maximum power, now it has been restated as maximum 'empower'. The main declaration appears to be in the words of C.Giannantoni,

The "Maximum Em-Power Principle" (Lotka-Odum) is generally considered as the "Fourth Thermodynamic Principle" (mainly) because of its practical validity for a very wide class of physical and biological systems (C.Giannantoni 2000, § 13, p. 155)

His related mathematical work is referenced above.

• my plan?

First ask, "What is a scientific principle or law?" and try not to answer this question with symbolic mathematical logic proof, but rather instrumental proof.

Second. Construct a simple galvanoscope (which appears to be an uncalibrated ammeter). Observe that this one instrument involves at least each of magnetism, electricity, chemical corrosion, mass transfer and heat dissipation all at the same time. Construct to verify for yourself...it gets quite hot with a 9 volt battery!

Third. If this instrument is involved in the quantification of any of the laws of thermo(heat)dynamics then it seems to me that it is also involved in the quantification of magnetism, electricity and chemical corrosion at the same time.

Fourth. There is no fourth, simply ponder and play with the instrument.

Fifth. See if you can divorce "power" (voltage and current) from the instrument.

Sixth. If you cannot divorce power from the instrument, and the instrument is involved with the quantification of the laws of thermodynamics, then power -and therefore time- also appears to be involved with the quantification of the laws of thermodynamics.

Seven. Pause and consider, how many scientific laws can be demonstrated with this instrument? This will do for now cept to say that max power principle involves heat and current and max empower will involve corrosion and mass transfer. Sholto Maud 11:17, 5 December 2005 (UTC)

References

1. A.J.Lotka (1922a) 'Contribution to the energetics of evolution'. Proc Natl Acad Sci, 8: pp. 147–51.

2. A.J.Lotka (1922b) 'Natural selection as a physical principle'. Proc Natl Acad Sci, 8, pp 151–4.

3. G.Q. Chen (in press) 'Scarcity of exergy and ecological evaluation based on embodied exergy', Communications in Nonlinear Science and Numerical Simulation, p. 16.

4. H.T.Odum amd R.C.Pinkerton (1955) 'Time's speed regulator: The optimum efficiency for maximum output in physical and biological systems ', Am. Sci., 43 pp. 331-343.

5. H.T.Odum (1994) Ecological and General Systems: An Introduction to Systems Ecology, Colorado University Press.

6. C.Giannantoni (2000) 'Toward a Mathematical Formulation of the Maximum Em-Power Principle', in M.T.Brown (ed.) Emergy Synthesis: Theory and applications of the emergy methodology, Proceedings from the first biennial emergy analysis research conference, The Center for Environmental Policy, Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL.

7. M.Tribus (1961) § 16.11 'Generalized Treatment of Linear Systems Used for Power Production', Thermostatics and Thermodynamics, Van Nostrand, University Series in Basic Engineering.

Sholto, I ordered your suggested book: Giannantoni, C. (2000). After I receive it, I'll give it a read and see what this is all about? I know I've read a little about Lotka somewhere; and loosely I know that all this 'exergy', 'emergy', empower, stuff is just a backwards British way (using sign changes) of talking about the SI 'free energy' (exergy, with correlations), 'entropy' (extropy, with correlations), etc. So why don't you give me some time to read your book, maybe a month or so, and we can possibly do a short paragraph on ecological evolution in the thermodynamic evolution article. Also, I work with a group of people that runs the largest fourth law of thermodynamics list on the internet (we are a top three search on dogpile.com for "fourth law of thermodynamics"): List 4th Laws; thus, if what you are talking about is true we can add your contribution there. P.S. here at Misplaced Pages we just write concise, to the point, referenced articles, we don't build things. Talk later:--Wavesmikey 20:01, 5 December 2005 (UTC)

Also, power and time are already both accounted for in the 1st and 2nd laws combined in the form of an energy balance on a thermodynamic system. The concept of thermodynamic "state" accounts for time, i.e. the energetic difference between to states, and work, which is power multiplied by time, is accounted for in either Helmholtz or Gibbs free energy, depending upon system constraints. I'll jot a note to your user page when I receive the book. Toodle-oo:--Wavesmikey 20:14, 5 December 2005 (UTC)

• Thank you for your kind comments Wavesmikey. I notice your humanthermodynamics site references Jorgensen as giving a statement of 4th law as maximum power. In fact Jorgensen and Odum combined their approaches. In S.E. Jorgensen, S.N.Nielsen, H.Mejer (1995) 'Emergy, environ, exergy and ecological modelling (I995) Ecological Modelling 77, pp. 99-109, they state that,

"Emergy calculations have the same aim as exergy: to capture the energy hidden in the organization and construction of living organisms."

In S.E.Jorgensen, M.T.Brown, H.T.Odum (2004) 'Energy hierarchy and transformity in the universe', Ecological Modelling, 178, pp. 17-28, they state that "Lotka's principle of self-organizing for maximum power, offered as the fourth energy law" (p. 18).

I've just noticed also that Tribus (see above references) first references Odum & Pinkerton re: maximum power, and then goes on to talk about the Onsager relations in the same sub-chapter. Lets reconvene after you've had a look at the book. Sholto Maud 22:45, 5 December 2005 (UTC)

Part of Article tagged for Afd

Someone has sent the thermodynamic evolution article to the "Articles for Deletion" section; if you care to vote, the section is: Afd 2005, Dec. 15.