On 2/20/2012 12:02 PM, Evgenii Rudnyi wrote:

On 20.02.2012 19:54 meekerdb said the following:On 2/20/2012 10:33 AM, Evgenii Rudnyi wrote:On 19.02.2012 22:13 Russell Standish said the following:On Sun, Feb 19, 2012 at 11:21:01AM -0500, John Clark wrote:On Sun, Feb 19, 2012 at 5:32 AM, Evgenii Rudnyi<use...@rudnyi.ru> wrote:If one well defines a thought experiment with the Maxwell's demon, thenit is quite clear that such thing does not exist. Why then to spend on it so much time?Maxwell's demon is possible in classical physics and it was not clear that quantum mechanics made it impossible until 1929 when Leo Szilard proved that to be the case. And understanding just why it can not exist aids in understanding the relationship between energy information entropy and reversibility. Maxwell's demon was the starting point for Rolf Landauer's discovery in 1960 that erasing information always requires energy and increases entropy because it's thermodynamically irreversible.Good answer John. Does anyone want to pick on Evgeni's comments about Chris Adami's book? It weird, because Chris's book gives some of the bext examples of the application of statistical physics to artificial life. In particular, his observation that mutation should play an analogous role to temperature in an evolutionary process, and that several evolutionary regimes exist as mutation is varied, corresponding to phase transitions in materials.I have nothing against Adami's book as such. His description of his software avida and his experiments with it are okay. My point was about his claim that his work has something to do with thermodynamics. It is definitely not. The thermodynamic entropy is not there. The quotes from the book displays this pretty clear. You have written about "an analogous role". I would not object if you say that there is an analogy between the thermodynamic entropy and information. Yet, I am against the statement that the thermodynamic entropy is information and I believe that I have given many examples that show this.What you are overlooking is that information is *about* things. So entropy in thermodynamics is information about the system's location in phase space. That's what connects "information" and "work" and "temperature". Entropy in communication theory is about the location of a message in message space. It's a different application of the same concept. The two overlap when considering the minimum free energy requirements of a physical realization of a computation - but existing computers operate far above those minimums so the overlap is only of theoretical interest.What is left is to apply your concept to examples in practice. Then it would be moreclear what you mean. Let me repeat just one question that you have not answered yet (butI believe that I have given much more examples and they have not been worked out).The only example of the entropy used by engineers in informatics has been given by Jasonand I will quote him below. Could you please tell me, the thermodynamic entropy of whatis discussed in his example?I am ready to learn the meaning of information in thermodynamics. Please just explain itby means of practical examples.

`The link I sent below works out the entropy of an ideal gas using information. You keep`

`asking for "practical examples" but that's like asking for practical examples of`

`calculating molecular reaction free energy from quantum mechanics. It is very difficult`

`because it depends on the electron energy levels. It has been done in a few simple (not`

`necessarily practical) cases as a proof of principle. But it is not the way engineering`

`or chemistry is done because it is both easier and more reliable to measure them. But`

`that doesn't mean that they don't have energy or that the concept of energy doesn't`

`apply. No one calculates the strength of steel from carbon and iron atomic bonds and`

`crystal structure either. But that doesn't mean the strength of steel is a separate,`

`independent property.`

I personally do not see thermodynamics in the Jason's work. Please just explain what Iam missing.On 03.02.2012 00:14 Jason Resch said the following: … > Evgenii, > > Sure, I could give a few examples as this somewhat intersects with my > line of work. > > The NIST 800-90 recommendation ( > http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf ) > for random number generators is a document for engineers implementing > secure pseudo-random number generators. An example of where it is > important is when considering entropy sources for seeding a random > number generator. If you use something completely random, like a > fair coin toss, each toss provides 1 bit of entropy. The formula is > -log2(predictability). With a coin flip, you have at best a .5 > chance of correctly guessing it, and -log2(.5) = 1. If you used a > die roll, then each die roll would provide -log2(1/6) = 2.58 bits of > entropy. The ability to measure unpredictability is necessary to > ensure, for example, that a cryptographic key is at least as > difficult to predict the random inputs that went into generating it > as it would be to brute force the key. > > In addition to security, entropy is also an important concept in the > field of data compression. The amount of entropy in a given bit > string represents the theoretical minimum number of bits it takes to > represent the information. If 100 bits contain 100 bits of entropy, > then there is no compression algorithm that can represent those 100 > bits with fewer than 100 bits. However, if a 100 bit string contains > only 50 bits of entropy, you could compress it to 50 bits. For > example, let’s say you had 100 coin flips from an unfair coin. This > unfair coin comes up heads 90% of the time. Each flip represents > -log2(.9) = 0.152 bits of entropy. Thus, a sequence of 100 coin > flips with this biased coin could be represent with 16 bits. There > is only 15.2 bits of information / entropy contained in that 100 bit > long sequence.Thermodynamic entropy is not subjective and not context dependent*, so my claim is that Adami does not understand what the thermodynamic entropy is. He has never taken a class in experimental thermodynamics, this is the problem.I'm beginning to think you have never taken a class in statistical mechanics. There's a good online course here:I have done a class in statistical thermodynamics. Actually it was a pretty good classwhere different approaches of Boltzmann, Gibbs and other have been considered in detail.The difference is that I do not believe that a similar equation in different areas implythat the different things are the same.If you would like to show that information is very useful in thermodynamics,

Other, smarter people have already done that.

please apply it to simple thermodynamic problems to show how the concept of informationhas simplified for example the computation of the phase diagram (or equilibriumcomposition between N2, H2 and NH3). Should I repeat my examples?

`No, you should consider why chemists don't just calculate all reactions and structure from`

`atomic theory and QM.`

Brent

Evgeniihttp://farside.ph.utexas.edu/teaching/sm1/lectures/lectures.html Those particularly relevant to this thread start at http://farside.ph.utexas.edu/teaching/sm1/lectures/node61.html and go through the next six or seven. Brent* I would accept the notation that the entropy is context dependent in a sense that its definition depends on the thermodynamics theory. If we change the theory, then the entropy could have some other meaning. But it seems not what you have meant. EvgeniiThis phenomena I have observed in my own evolutionary experiments. Plus, it appears to be correlated to Mark Bedau's evolutionary classes. This is the paper I usually refer to, although his ideas have evolved somewhat since 1998: M. A. Bedau, E. Snyder, N. H. Packard. 1998. A Classification of Long-Term Evolutionary Dynamics. In C. Adami, R. Belew, H. Kitano, and C. Taylor, eds., Artificial Life VI, pp. 228-237. Cambridge: MIT Press. Also published as Working Paper No.98-03-025, Santa Fe Institute, Santa Fe, NM. http://people.reed.edu/~mab/publications/papers/alife6.pdf

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