Talk:Entropy/Archive 8

message: I found this nice page about Boltzmann's contribution to science:
*1872 Boltzmann Article - Manhattan Rare Book Company  
This rare article costs $3,600 dollars; I'll pitch in the first ten dollars. --Sadi Carnot 04:56, 22 November 2006 (UTC)
replies: text: Coming back to look at the Entropy article after a long hiatus, I am refreshed by Sadi's light comment (although still depressed by the size of the article and the discussion, prior to Bduke!)  As Sadi undoubtedly is well aware, an English translation of the 1872 article is available on pp. 88-175 of Volume 2 of "The kinetic theory of gases : an anthology of classic papers with historical commentary" by Stephen G Brush ; edited by Nancy S Hall. London: Imperial College Press ; River Edge, NJ : Distributed by World Scientific Pub., C2003. This is evidently a reprint of the 1965 Brush publication by Oxford  (The 'Boltzmann equation' to which the ad for the rare article refers is Boltzmann's H equation, of course, not Planck's 1900 or 1906 versions of the equation on Boltzmann's tombstone.)     FrankLambert 06:02, 23 November 2006 (UTC)
thread_title:  Nice 1872 Boltzmann article page 

message: Firstly, thanks for tackling the major task of making this article understandable. Sorry it's been a bit hectic lately at souza acres, so haven't had time to do more than glance at it. 
My first impression is that the lists of definitions have to be removed: if they provide useful explanation, that should be incorporated into the text. From memory, many of them don't even appear in the detailed articles, where they belong. The disorder / dispersal and topics in entropy sections also need severe pruning to focus on an elementary explanation. Secondly, as you say, some work is needed to improve the brief explanations: in particular no previous knowledge of maths symbols can be assumed, so for example Δ needs to be described in writing, and ln explained. Agree with PAR that a very brief explanation of the information entropy / statistical position is needed. Will try to find time to comment in more detail, but rather tied up for a while, .. dave souza, talk 09:19, 6 December 2006 (UTC)
thread_title: More pruning and explanations

message: "via intermolecular molecular frictions and collisions" •Jim62sch• 23:45, 22 November 2006 (UTC)
thread_title:  What???? 

message: This isn't Wikiquote.  Is there any reason we need a humor-quote section in an article on a serious science topic?  I'm unsure if this was the result of some previous consensus discussion or something, so I thought I'd inquire before simply pulling the material.  Serpent's Choice 02:01, 9 January 2007 (UTC)
replies: text: Section removed, though I'm open to discussion regarding means to include the content elsewhere if someone so desires.  Serpent's Choice 07:52, 10 January 2007 (UTC)
thread_title:  Quotes and humor 

message: Maybe I'm just silly, but I don't feel there is an actual definition for entropy.  The article states that entropy increses or dececreases in a given system, that it is essential to the 2nd law of thermodynamics.  But what IS it, if it is already there, and I missed it, can somebody point me to it? Thanks 201.134.106.227 Alex B.
: Here's a somewhat nontechnical definition from the article:  "Spontaneous changes tend to smooth out differences in temperature, pressure, density, and chemical potential that may exist in a system, and entropy is thus a measure of how far this smoothing-out process has progressed." - JustinWick 21:26, 23 January 2007 (UTC)
thread_title:  Definition 

message: Why is the page perpetually terrible? The two definitions of entropy are unbelievably difficult to find in the intro - the statistical definition being findable, the other.. almost not being there at all... Fresheneesz 22:08, 17 April 2007 (UTC)
thread_title:  Awful 

message: Is there a formula for (relative) entropy like there is for temperature?
:T = \frac{\ 2 \langle E \rangle}{k}
That is, if I have a molecular simulation and know the velocities of all atoms, then I know the velocities of all atoms at another point in time, can I find ΔS? —Ben FrantzDale 22:42, 1 May 2007 (UTC)
thread_title:  Formula 

message: I have just run across this page, The Laws of Thermodynamics by one John S. Denker, which I think would make a particularly useful "External link".  IMO the page is unusually clear and well-written, and would be particularly useful for intermediate-level readers, who may have come across quite a lot written quite loosely about entropy and heat and thermodynamics. I think it could be particularly useful to them, in presenting rather cautiously and carefully what is fundamentally true about entropy, and clarifying it and separating it from notions which are only mostly true, which readers may have picked up from more glib introductory presentations.
In that respect I believe it fits rather well WP's key criterion for external links, of information which is accurate and on-topic, but presented at a level of detail (and in this case perhaps a level of technical nicety) which is more than is appropriate for WP's own article.  I think it fits the criterion of a useful additional external source over and above the content which a Wikipedia "Good Article" might be expected to contain.
So, what do people think of the link, both in its own right, and as a candidate for the "External Links" section of this article?  -- Jheald 13:49, 22 May 2007 (UTC)
replies: text: I did not read that section as a ranking. He states that those nearer the top are more informational entropy and those nearer the bottom more thermodynamic entropy. Therefore it is quite proper for chemistry to be at the bottom as the least concerned with informational entropy. I share your other concerns however after a brief read of an enormous document. --Bduke 03:11, 8 June 2007 (UTC)
replies: text: Are we talking about the same page here?  Denker's page seems absolutely rooted in physics.  That page is overwhelmingly a page about entropy in thermodynamics.  I don't see any substantial material on that page that is not relevant to entropy in physics.  Jheald 09:00, 8 June 2007 (UTC)
thread_title:  A nice external page? 

message: Merely to scroll down this enormous site takes 4 minutes and 40 seconds, but using Denker's 'Contents' (reached in 15 seconds :-)) to quickly access Section 20 "The relevance of entropy" near its end, you will discover his unique ranking of the importance of entropy to various fields of interest: "1. cryptography...4. librarianship...11. chemistry and chemical engineering".  A brilliant physicist and published author in aeronautics, John Denker for many years has been writing his own sometimes good, sometimes awful version of information entropy. He does not believe in the relevance of energy to thermodynamic entropy. He says that the Third Law of thermo does not exist. He cites no peer-reviewed publications of his in the field of entropy, nor a single text or any kind of book by others that cite his writing. Thus, to cryptographers or librarians -- but not to those concerned about thermodynamic entropy in chemistry or physics -- Denker could be recommended.   FrankLambert 01:26, 8 June 2007 (UTC)
replies: text: I did not read that section as a ranking. He states that those nearer the top are more informational entropy and those nearer the bottom more thermodynamic entropy. Therefore it is quite proper for chemistry to be at the bottom as the least concerned with informational entropy. I share your other concerns however after a brief read of an enormous document. --Bduke 03:11, 8 June 2007 (UTC)
replies: text: Are we talking about the same page here?  Denker's page seems absolutely rooted in physics.  That page is overwhelmingly a page about entropy in thermodynamics.  I don't see any substantial material on that page that is not relevant to entropy in physics.  Jheald 09:00, 8 June 2007 (UTC)
thread_title:  But only for information entropy, '''''not''''' for thermodynamic entropy! 

message: There is an error in the integral defining the entropy difference, even if dS is an exact integral (if the transformations are reversible that is) dQ is NOT an exact integral, and this should be stated by having a barred "d" or a "delta" instead of a simple "d" in the formula. The best would be a barred "d" like the "\dj" in the MikTex distributions.
I cannot do this correction myself because i don't know latex that much :)  —Preceding unsigned comment added by 89.97.102.194 (talk) 09:22, 22 September 2008 (UTC)
replies: text: In physics and mathematics we call this "abuse of notation". Abuse of notation is very common in the physics and math literature. Since wikipedia is supposed to reflect the literature, there is really no problem. What we should do is explain that "dQ" is not to be interpreted as a differential of a function "Q", as such a function does not exist. It merely represents an infinitessimal amount of heat added to the system. Count Iblis (talk) 14:45, 27 November 2008 (UTC)
thread_title:  Exact Differential 

message: Bduke, all I did was move the bulk of the lead to an "overview" section.  The current lead paragraph (which is completely un-referenced), show below, is filled with errors (especially the etymology):
:The concept of entropy (Greek: εν (en=inside) + verb: τρέπω (trepo= to chase, escape, rotate, turn) [wrong (τροπή meaning "transformation", )]) in thermodynamics is central to the 2nd law of thermodynamics, which deals with physical processes and whether they occur spontaneously [wrong (the measure of spontaneity is "free energy" as per the combined law of thermodynamics)]. Spontaneous changes occur with an increase in entropy [wrong (only for isolated systems)]. Spontaneous changes tend to smooth out differences in temperature, pressure, density, and chemical potential that may exist in a system, and entropy is thus a measure of how far this smoothing-out process has progressed [close (in some cases, but no reference)]. In contrast, the first law of thermodynamics deals with the concept of energy, which is conserved [correct (but does not explain what the connection is to entropy)].
I'll move the bulk of the lead back in, but I'm still correcting all this mess; for instance, all these suppositions need to be referenced.  As to your statement "entropy is not anymore what Clausius wrote", there is some truth to this (in terms of verbal terms), but entropy, at its core, is what he wrote (in conceptual and mathematical terms).  Now that the original paper is available, I intend to include a blend of this, as well as modern views, in the lead.  No need to do any further reverting, please work together on this.  --Sadi Carnot 07:05, 31 July 2007 (UTC)
replies: text: It seems good now.  I'm guessing, however, that if the lead keeps growing, some of it will have to be moved into a new "overview" section (which is what I was attempting to do before), as per WP:LEAD which states that opening section "should contain up to four paragraphs, should be carefully sourced as appropriate, and should be written in a clear, accessible style so as to invite a reading of the full article". --Sadi Carnot 07:16, 31 July 2007 (UTC)

text: I agree with you, any subject should be written in the manner that best conveys information in a digestible manner.  One should not, however, bend, twist, misconstrue or even misrepresent basic science and logic for the sake of readability.  Presently, to review as things currently stand, we are debating the first two sentences in the article.  Please explain what your fuss is about (with these two sentences)?  All I did was to correct wrong information and to add a reference. --Sadi Carnot 08:00, 31 July 2007 (UTC)
thread_title: Current lead

message: Jheald, let me get this straight: from your point of view, I’m an imbecile and you want me to go away? --Sadi Carnot 02:36, 1 August 2007 (UTC)
replies: text: No, but from time to time, like all of us, you may write things which make you look clueless.  At which point, the best solution is to get a clue.  I told you 18 months ago that this sort of statement about information entropy was misconceived, and yet you still trot it out. Jheald 08:22, 1 August 2007 (UTC)

text: In any event, thanks for the nice comments, I've added them to my user page. --Sadi Carnot 03:21, 1 August 2007 (UTC)
thread_title: Jheald’s comments

message: I have changed economic entropy from being a quantitative value to a semi-quantitative value. I would go further and call it qualitative, but people might disagree. I fail to see how it can be quantitative without a mathematical definition, which is stated by the article by filing it under sociological definitions. I would argue that quantitative measurements must be of a known quantity if they are to be named as such. Thanks User A1 11:26, 6 August 2007 (UTC)
thread_title:  Economic entropy 

message: Ω, the number of microstates, in S = k ln Ω might be better interpreted as a relative number of states which would be a dimensionless quantity for which the logarithm would be defined.
On p. 24 of Wolfgang Pauli's Statistical Mechanics (Vol. 4 of Pauli Lectures on Physics) he comments,
"The statistical view also permits us to formulate a definition of entrophy for nonequilibrium states. For two states, 1 and 2 we have
S2 - S1 = k log(W2/W1);
leaving the additive constant unspecified, we obtain
S = k log W.
Because of the logarithm, and because the probabilities of independent states multiply, the additivity of entrophy is maintained."  --Jbergquist 18:41, 2 October 2007 (UTC)
thread_title:  Entrophy and the relative number of states 

message: Under "Miscellaneous definitions", "Gibbs entropy"
is described as being the "usual statistical
mechanical entropy of a thermodynamic system".
However, Gibbs entropy does not appear to be
defined in this article, and the linked article
on "Gibbs entropy" does not define some of the
terms used. 68.111.243.96 20:18, 17 October 2007 (UTC)
thread_title:  Gibbs entropy as fundamental but not defined? 

message: Editors of this page might like to look over the recent to-and-fro and Entropy (disambiguation).  User:Thumperward seems dead set to (IMO) make the page harder to use.  Compared to eg this edit, he seems determined to
* remove the link to Introduction to entropy
* remove links directing people to find additional entropy articles in the categories
* reduce the structuring of the page between thermodynamic entropy and information entropy.
-- all of which (IMO) are mistakes.  Anyhow, there have been a series of reverts and counter-reverts (I've now had my 3 for the day), and there's discussion on the talk page there, if anybody wants to have a look.  Jheald 13:52, 18 October 2007 (UTC)
replies: text: Never mind, we seem to have come to agreement.  Edit war over :-)  Jheald 15:47, 18 October 2007 (UTC)
thread_title:  Entropy (disambiguation) 

message: And if I click on the wiki link or multiplicity function I see the expression for a system of N noninteracting spins :) Also, we should avoid using misleading examples of a system of which the energy levels are exactly degenerate. It is better to define \Omega as F. Reif does in his textbook: \Omega\left(E\right) is the number of energy eigenstates with energy between E and E+\delta E, where \delta E is a macroscopically small energy interval. The entropy defined in this way depends on the choice of \delta E, but this dependence becomes negligible in the thermodynamical limit. It cannot be set to zero, because then for generic systems \Omega=1, and the entropy becomes identical to zero.
Basically what happens is that if you specify the energy of a system with infinite accuracy, then there can be only one microstate compatible with that energy specification. This entropy is the so-called fine grained entropy, while the entropy defined with the nonzero \delta E is the coarse grained entropy.  Count Iblis 15:24, 23 October 2007 (UTC)
thread_title:  "calculated using the multiplicity function" ???? 

message: Shouldn't the inequality be a less than or equal to sign rather than a greater than or equal to sign?  That should probably be fixed.
--Lee  —Preceding unsigned comment added by 24.3.168.99 (talk) 05:39, 21 November 2007 (UTC)
thread_title:  Clausius Inequality