Talk:Entropy (order and disorder)

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[edit] Archives

• Archive: Talk:Entropy/Disorder ['04-(Nov)'05]
• Archive: Talk:Entropy/Archive1#disorder
• Archive: Talk:Entropy/Archive2#Entropy, order, and disorder

[edit] Comments from Talk:Entropy page

Hi, in continuation from kenosis' comments (above), first I'm going to add a short referenced sentence as per kenosis’ suggestion about recent incorporation of the "energy dispersal" perspective. Second, to help diffuse this issue, e.g. noting that “order and disorder” are hot topics on the talk page archives (ex. Talk:Entropy/Archive3#Disorder) and current ones, I’m going to start a order and disorder header section (with a link to its own article: entropy (order and disorder)). Third I collected the following stats to help clarify the prevalence of terms via Google search results:

1. entropy energy time – 6,490,000 results
2. entropy energy order – 5,310,000 results
3. entropy energy information – 5,070,000 results
4. entropy energy life - 1,670,000
5. entropy energy chaos – 1,050,000 results
6. entropy energy disorder – 694,000 results
7. entropy energy dispersion – 639,000 results
8. entropy energy dissipation – 503,000 results
9. entropy energy irreversibility – 164,000 results
10. entropy energy dispersal – 63,000 results
11. entropy energy disgregation – 88 results

I hope this clarifies things. I suggest that we work together to build the entropy (order and disorder) article (where we put most of the chaos discussion) over the next few weeks and put a short intro paragraph with a “see main” link on the entropy page. I'll take a chunk out of the statisitical perspective section to give it a quick start and we can build on this. Is this fine with all? --Sadi Carnot 10:32, 31 October 2006 (UTC)

Hi Sadi, all!

How's your German (I'll translate later). I've found this in a scriptum by Norbert Straumann [1]:

In der Thermodynamik ist es wichtig, dass man Wärme und Arbeit streng unterscheidet, obwohl im 1. Hauptsatz ihre Aequivalenz festgestellt wird. Diese Unterscheidung ist nur möglich, wenn man sich auf die Existenz adiabatischer Wände beruft. Diese sollen zwar selber keine thermodynamischen Eigenschaften haben, aber dennoch den Ausgleich von Temperaturdifferenzen verhindern. Aehnliche Fiktionen (z.B. ideale Antikatalysatoren) werden wir später benötigen. Für deren Existenz kann man sich nicht wirklich auf die Erfahrung berufen, und deshalb hat diese Pauli mit Recht "Zaubermittel" genannt. Erst in der statistischen Mechanik hat man diese Zaubermittel nicht mehr nötig. In dieser ist die Wärme derjenige Anteil der Energie, der den makroskopisch nicht beobachteten Freiheitsgraden zugeschrieben werden muss. Was aber makroskopisch beobachtet wird, hängt wesentlich von den Beobachtungsmöglichkeiten ab. Darum ist die Wärme, und damit die Entropie (s.u.), in der statistischen Mechanik strenggenommen immer nur relativ zu einem makroskopischen Beobachter definiert.

Short essence: Whereas in statistal mechanics heat and therefore entropy are only defined relavtive to a choice of macro variables, they are unique in classical thermodynamics, but only because of use of "adiabatic walls", which are a fiction themselves.

And from the preface:

Die phänomenologische Thermodynamik wird von Dozenten und Studenten mit Recht immer wieder als eine Disziplin empfunden, die zwar mathematisch anspruchslos, aber begrifflich doch recht subtil ist. Hinzu kommt, dass diese Theorie anderen Gebieten der theoretischen Physik in ihrem ganzen Aufbau fremdartig gegenüber steht. Für die meisten Studierenden ist es vernünftig, nicht zuviel Zeit in das Studium der Thermodynamik zu investieren und sich möglichst rasch der Statistischen Mechanik zuzuwenden.

My translation: Teachers and students a like see phenomenological thermodynamics as a topic, which is mathematically undemanding but with some subtle points. In addition the theory in its entire composition is rather alien to other topics in theoretical physics. Most students shouldn't invest too much time for studying thermodynamics but proceed swiftly to statistical mechanics.

Of course, after having stated that thermodynamics is mathemically rather trivial, he proceeds to the modern treatment via differential forms and manifolds in all glory ;-)

Pjacobi 11:00, 31 October 2006 (UTC)

Hi Pjacobi, my German is in need of improvement (I hope to be semi-fluent before I go to Octoberfest some day). Here's one of my favorite quotes, from the chemical thermodynamics page, which exemplifies my perspective: In the preface section to popular book Basic Chemical Thermodynamics by physical chemist Brian Smith, originally published in 1973, and now in the 5th edition, we find the following overview of the subject as it is perceived in college:^[1]

Also, I gave the new header section to "order and disorder" a good start (and added seven new sources and uploaded two images); we can all now build it, e.g. I'm pretty sure that Hermann von Helmholtz and possibly others had some ideas on order and disorder, then later when it gets too big paste most of it to its own page. Out of time for today. Happy Halloween - ! --Sadi Carnot 13:57, 31 October 2006 (UTC)

A good start, but you still don't seem to have provided a clear explanation of what "disorder" means in relation to modern science as an introduction for beginners, and indeed seem to be using the Encarta reference which you consider to be not exactly correct. No doubt these points can be improved, The section leads naturally on to the "dispersal" perspective, so I've revised that section to bring it closer to the modern approach, and have incorporated the Atkins reference you provided in its context. The Scott reference appears to have no obvious relevancy and is clearly not the first to use the concept, so I've moved that to the main dispersal article. Lets hope you can clarify the disorder approach in a way that no longer stretches the most powerful of minds! Please remember that while you're very familiar with the jargon, this page should be aimed at helping newcomers to the subject. ... dave souza, talk 15:58, 1 November 2006 (UTC)

I just added the adiabatic demagnetization example (with a new image); I hope this helps. Also, I moved most of the "order/disorder" stuff to its own page: Entropy (order and disorder). I also, likewise, trim down the dispersal section a bit so that it is in proportion to the rest of the sub-articles (with a new source) and moved some of it to its own page. --Sadi Carnot 17:13, 1 November 2006 (UTC)

[edit] Adiabatic demagnetization

I've revised this section a bit to clarify the process. However, the bit about the second law seems a bit dodgy as magnetic energy clearly goes through the insulated chamber – perhaps you could reconsider that bit? .. dave souza, talk 11:16, 17 November 2006 (UTC)

Although it wouldn't have the practical application of ultra-cooling, the relevance to entropy might be more clear if magneto-caloric effects were discussed in an isothermal context (temperature held constant) rather than an adiabatic context (insulated - no heat flow). In an isothermal context, heat will flow into or out of the sample to maintain the temperature as the magnetic field is changed. This heat flow can be related directly to the definition of entropy (heat flow divided by temperature). Compbiowes 22:35, 10 January 2007 (UTC)

I think the discussion is incorrect here. If the magnetic field is reduced adiabatically, the amount of order in the spin has to remain the same (Delta S = 0). The temperature does indeed decrease because the entropy is roughly a function of B mu / T, and in order to keep entropy fixed with decreasing B, then T must also drop. —Preceding unsigned comment added by 135.245.8.36 (talk) 19:57, 27 April 2008 (UTC)

Have a look at the cited NASA page on the effect – it's to do with the energy involved in aligning the magnetic field, rather than any appearance of "order" or "disorder". .. dave souza, talk 20:07, 27 April 2008 (UTC)