Talk:Second law of thermodynamics/Archive 1

message: Moving the whole discussion about the Second Law, creationism, and the evolution/stability of organised systems to Talk:Second law of thermodynamics/creationism Jheald 13:29, 5 November 2005 (UTC)
thread_title:  Separate talk page for Second Law and creationism / organised systems 

message: I believe the following explanation is false or at least very misleading, so I intend to correct it after a quick review in my stat-mech book. I post my intentions here so that if someone things I am wrong (and the current article is correct), we can have that discussion first.
:"Since the universe is tending towards a greater entropy (expanding over time, with lower energy density), all work processes within the universe also tend towards a greater entropy. "
I believe the above is false or very misleading. The 2nd law of thermodynamics is not caused by the expansion of the universe. The 2nd law is believed to apply to any closed system, and so it is not caused by the expansion of the universe. The 2nd law is believed to be a macroscopic statistical property that can be derived from the microscopic laws of physics (although I don't know whether or not anybody has managed to do this yet in a rigorous way.) 
Does anybody disagree with me, and believe the 2nd law is held to be due to expansion of the universe? If so, is there an academic paper or text book you can cite? Thanks. Bmord 
:I'm wondering if you didn't just misunderstand the quote.  Certainly your interpretation of it was different from mine.  I honestly wasn't given the impression from the quote that the second law was actually caused by the expansion of the universe; though it certainly is true that the entropy is increasing as our universe expands.
:--Wade A. Tisthammer (10/2/2005)
::A does not cause B, and B does not cause A - this is why I figured I would remove it. The basket ball does not fall down due to increasing entropy, and it does not bounce back up because of increasing entropy. If the universe were to stop expanding and start falling back in on itself for the 'big crunch' due to gravity finally overwhelming leftover momentum from the big bang (as has at times been predicted), this again would not be due to increasing entropy. (The fact that the basketball doesn't bounce quite as high on each subsequent bounce - now that does have something to do with increasing entropy.) (I should mention that I have made the edit - apologies for not using the edit summary feature on the main article.) Bmord 
:::I thought we had settled this, I'm not sure why it reappeared. Discussion of this has now moved to a lower section ('Deletion of part related to universe collapse'), refering to a more recent reincarnation of this popular mistake. Bmord 18:39, 5 November 2005 (UTC)
thread_title: False/Misleading Explanation?

message: the only way i have ever understood this stuff is someone explaining macrostates and microstates. they reduce it to a small game of black and white chits on a board or something. or maybe it was coins, and heads and tails. i cant remember where i saw this, but it sure would help people reading wikipedia if someone could do the same here.
A microstate is the specification of the of the system at a microscopic level, while a macrostate is a description of the global average of the system.  
As an example, lets play a game with 4 dice (read: discrete particles) that are repeatedly rolled.  Only combinations of the rolls that total "6" (read: total energy of all particles is "6") are retained.  This leads to a number of possible microstates, whilst maintaining a constant macrostate, viz.,
Dice: 
1  2  3  4  
2  2  1  1  
2  1  2  1  
2  1  1  2  
1  2  2  1  
1  2  1  2  
1  1  2  2  
3  1  1  1  
1  3  1  1  
1  1  3  1  
1  1  1  3  
If you look at dice (particle) one say, there are a number of different numbers (energies) that are permissible given the (macroscopic) constraints of the system.  Thus, the specification of the individual numbers on the dice (energy of a particular particle) is the microstate of a system, which leads to the same global average, or macrostate.  
As an aside, under statistical mechanics the probability of obtaining any given microstate is equally likely (equally likely a priori probabilities) however, the "score" of each individual dice is not uniformally distributed.  For dice 1 there's 6 microstates that yield  1, 3 that yield  2 and only 1 that yields a score of 3.  When drawn properly as a histogram (using a liberal amount of imagination) this looks a little like an exponential, and if you take the limit of N (the number of rolls) to infinity then you end up with true exponential graph.  This is a demonstation of how the Boltzmann distribution can be obtained for an equilibrium system upon the premise of equally likely a priori probabilities.   Lateralis 22:33, 7 December 2005 (UTC)
thread_title: microstates and macrostates

message: I'm trying to explain the 2nd law in simple terms. This is still very much a work in progress. Any help welcome.  I have some difficulty making the link between the fact that no heat cycle has a 100 % efficiency, and the fact that disorder is growing: why are those facts equivalent ??  I'll have to do some more research to find out... Pcarbonn 20:41, 22 May 2004 (UTC)
thread_title: Link between heat cycle and entropy ? 

message: Quote from page: "Any device that violates the second law of thermodynamics would be called a perpetual motion machine of the second kind. One example of this would be a device that can do work such as pumping water, simply by taking energy from the air."
Though I'm not sure what the definition of a perpetual motion machine of the second kind is, it seems to me that this paragraph is unclear since readers will think "But that's possible - people have been using windmills for ages - so perpetual motion is possible?" Perhaps change this to "by taking heat energy from the air. ( Or better yet, the perfect example would be a light powered the solar panel that it was shining on" --Jomel 15:23, 13 Aug 2004 (UTC)
replies: text: I agree, the statement is *very* confusing. After looking at the definition of a perpetual motion machine "of the second kind", its clear that "pumping water, simply by taking energy from the air" is not an example of such a thing. The second kind requires that the heat energy is converted ENTIRELY into other forms of energy. If the mechanism used a heat gradent between the air and the ground, this would not violate anything. Fresheneesz 02:23, 8 December 2005 (UTC)
thread_title:  Makes it seem like perpetual motion machines are possible 

message: In perusing the archive I was disturbed that a blatant plug for a self published book of New Age, crank physics/metaphysics - complete with a link to the author's webpage where the book is hawked - was able to survive in the article unchallenged until until September 28th, 2005 (I won't further promote the book by repeating the name and title - suffice it to say it was in the section of the article entitled 'Other'). It is disturbing to think that such a blatant and cranky product placement could have gone unchallenged for so long. It makes one wonder how many similar instances of this sort of mischief there might be here at Wikipedia. 
WikipediaEditor 19:23, 1 October 2005 (UTC)
thread_title:  Kooks hawking books in Wiki articles 

message: quote from the article:
:The second law of thermodynamics is a consequence of the first law of thermodynamics (ie., energy is conserved) and the fact that the universe is expanding.
Just curious, how is the fluctuation-dissipation theorem related to the expansion of the universe? There must have been something I missed, because with the way the article is written, if I believe in everything that's in there, then I believe something's going to happen to fluctuation-dissipation theorem the day the universe stops expanding. Oh no, I know, the day where stops expanding, fluctuation-dissipation theorem will revert so that evolution will become proven and creationnism will become forbidden by the 2nd law arf arf arf!
Not to mention broken glasses would start jumping on tables.
No seriously, I disagree with that statement on the expansion of the universe and the 2nd law, on the basis that Hawking says he has been convinced of the contrary, in his book "A brief history of time." I don't think we should disregard such authorized scientific authority, unless someone can prove this statement for good.ThorinMuglindir 23:04, 31 October 2005 (UTC)
thread_title:  Let's start with the beginning 

message: This sub-section is for discussion of the deletion of the part relative to the collapse of the universe.ThorinMuglindir 00:50, 2 November 2005 (UTC)
replies: text: I agree with the deletion. My Stat Mech textbook (Fundamentals of Statistical and Thermal Physics, McGraw-Hill) describes the 2nd law as applying to all closed systems. From this I conclude that it applies also to closed systems that are not expanding - most of their examples are of non-expanding systems. I removed something similar before, but I guess someone added it back in - I agree it should not be added again. Bmord 18:27, 5 November 2005 (UTC)
thread_title:  Discussion of deletion 

message: Page temporarily protected due to Vandalism. If you want to unprotect, please make a request at WP:RPP ≈ jossi fresco ≈ t • @ 17:45, 21 November 2005 (UTC)
thread_title:  Protected 

message: Editors following this page might also like to quickly look at Probability of the universe, which IMO should not be in Wikipedia. -- Jheald 22:26, 21 November 2005 (UTC)
thread_title:  AfD: Probability of the universe 

message: Somebody revert the page, please. I can\'t, because I\'m using a proxy which is escaping all \' and \\  (like that). But it looks like this guy just won\'t stop. He needs to be banned. Infinity0 talk 12:06, 25 December 2005 (UTC)
replies: text: I reverted it and I agree, its the same vandal as before. PAR 15:30, 25 December 2005 (UTC)
thread_title:  The vandal is back... 

message: Regarding the statement that spontaneous processes increase entropy, what is a spontaneous process? 14:14, 26 December 2005 (UTC)
replies: text: A spontaneous process is one which naturally happens in a system without any outside interference.  For example, a pen balanced on its tip will spontaneously fall, which increases entropy.  Putting a pen on its tip is not a spontaneous process, because it would never reach that state naturally. --Ignignot 17:56, 26 December 2005 (UTC)
thread_title:  spontaneous process 

message: Please enumerate all your sugesstion below.  Bonaparte  talk 13:34, 29 December 2005 (UTC)
thread_title: Enumerate suggestions

message: Have you finish all your comments?  Bonaparte  talk 18:11, 1 January 2006 (UTC)
replies: text: See also Talk:Second_law_of_thermodynamics/creationism#Straw_poll PAR 23:23, 1 January 2006 (UTC)
replies: text: Yes. According to the poll the majority (5) vs. (2) disagree with it. Now, have you all solved all the issues? Are ther another issues that needs mediation?  Bonaparte  talk 16:56, 4 January 2006 (UTC)
thread_title: mediation

message: Is the agreement reached yet?  Bonaparte  talk 14:09, 5 January 2006 (UTC)
replies: text: On 7 January, after some exchanges on the Talk:Second law of thermodynamics/creationism subpage, I edited a two line capsule summary in at the end of the "complex systems" section, plus a link to a stub for a new separate article on the subject.  I hope this is an adequate resolution of the question, acceptable to all. -- Jheald 01:30, 10 January 2006 (UTC)
thread_title: agreement

message: I cleaned up the notation for the "exergy" section, I think the entire thing can be expressed in infinitesimals, and I added some clarifications. I do not endorse this section. I have not considered its validity or meaning. PAR 15:15, 3 January 2006 (UTC)
replies: text: I think you are right that infinitesimals are better. From an engineering perspective, they describe flow situations. From a physics perspective, they are better too. But I think the changes you made are less correct in a sense than what was there originally. I believe a funny-looking d(\delta Q) is involved in a more rigorous derivation...but this is a vague memory from college. I am looking into this.  Flying Jazz 22:47, 3 January 2006 (UTC)

text: I am certain the infinitesimals must be derivatives with respect to time for the concept to hold. I am using fluxions for clarity. In a sense, this application should not be endorsed by physicists because of the assumption made. I am adding content which may describe this better. Flying Jazz 09:42, 4 January 2006 (UTC)

text: I don't know enough right now to have a strong opinion on many details of your changes, but...I think most uses of the second law must either refer to a differential with respect to time or to "flowing along" with a substance in an open system. For example, cross sections of a turbine with condensing steam flowing in the -y direction would still obey the first law expressed as d/dy along the turbine, but if the second law is expressed as d/dy, you'd get the exact opposite of the math presented here. As you move mathematically from the outlet to the inlet of a turbine, entropy decreases and available work increases. Which seems almost too silly or contrived or maybe too obvious to mention for people who already know it, especially since the idea is explicitly stated in the words before the equations about what is leaving and entering the systems.  But it's always nicer when math explicitly agrees with words. Although this may require a diagram like the one that's in the enthalpy article now. As for renaming the exergy artcle, my hope is that when the article is done, readers who are familiar with the idea by another name will think "Oh.  Well now I see why this concept should have its own unique name," but I sure understand what you're saying about familarity, and...to be perfectly honest...until the article is more complete, I not 100% sure that I'll even be able to write an article that convinces me of this. Flying Jazz 08:50, 10 January 2006 (UTC)
thread_title:  Exergy