Gravity as an emergent phenomenon
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Re: Gravity as an emergent phenomenon
 
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Yes! YES! THANKYOU Grant!!!!!! I keep forgetting that crucial point.
OK, all you wise guys out there. What do you say to that?
Nick
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://www.cusf.org [City University of Santa Fe]
============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by Russell Standish
Russell Standish wrote circa 07/14/2010 02:09 PM:
> On Tue, Jul 13, 2010 at 10:07:14PM -0600, Roger Critchlow wrote: >> Working from the context, I'd guess: the tensor product between the >> components <i>dx<sup>a</sup></i> and <i>dx<sup>b</sup></i>of the stress >> energy tensor <i>T<sub>ab</sub></i>, but I've never been too sure about >> tensors. >> > > Not a tensor product, but an exterior product. It's somewhat related to > a cross product of two 3D vectors. Thanks for all the answers! It's interesting to me that this page: http://en.wikipedia.org/wiki/Differential_form#Wedge_product is less understandable to me than this page: http://mathworld.wolfram.com/WedgeProduct.html which is _less_ understandable to me than this page: http://en.wikipedia.org/wiki/Exterior_algebra A usual, each answer is different enough to provide a parallax. I always wonder what it would look like to circumscribe my (or anyone's) knowledge (or, at least, familiarity). Would the surface of such a circumscription have a very rough texture? Or would it be smooth[ish]? Would it have great big divots? Would the "things one knows (of)" even form a connected set? Everyone talks about wise people knowing when they don't know something. That seems easier said than done. ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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In reply to this post by Nick Thompson
Glen Ropella asked:
>What is that ^ symbol between dx^a and dx^b? Roger Critchlow writes: > Working from the context, I'd guess: the tensor >product between the components <i>dx<sup>a</sup></i> >and <i>dx<sup>b</sup></i>of the stress energy tensor > <i>T<sub>ab</sub></i>, but I've never been too sure ' >about tensors. I haven't read the Verlinde paper (and don't intend to; I find that treating string theoretical physicists as ignorable crackpots who, alas, have immense institutional power makes my life much simpler), but my guess about the "^" symbol is that it's meant to be the "wedge product" or "exterior product" rather than the general tensor product--in other words, it's skew-symmetric. As an example, in old fashioned terms, the tensor product of two vectors in R3, a = a1x1+a2x2+a3x3 and b = b1x1+b2x2+b3x3, where you can make the indices of ai and bj be lower and those on x be upper if you like, is the "dyad" ab = a1b1x1x1+a1b2x1x2+...+a3b3x3x3, which skew-symmetrizes to a^b = (a1b2-a2b1)x1^x2 + (a1b3-a3b1)x1^x3 + (a2b3-a3b2)x2^x3 (or maybe, depending on taste, to that divided by 2 or 3 factorial). ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by Nick Thompson
It doesn't matter, the bell jar serves to isolate the vapors inside from those outside. -- rec -- On Jul 14, 2010 9:38 AM, "Nicholas Thompson" <[hidden email]> wrote: ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by David Eric Smith
I can also recommend Harley Flander's book on Differential Forms ...
tom On Jul 14, 2010, at 5:53 AM, Eric Smith <[hidden email]> wrote: > Hi Glen, > > I believe it's also called a "wedge product". Mike Spivak's tiny but frustrating but elegant book Calculus on Manifolds, if I remember correctly, defines these things and explains what they mean in geometric terms. > > Eric > > > > > > On Jul 13, 2010, at 7:30 PM, glen e. p. ropella wrote: > >> >> So, Verlinde lost me in section 4. But I usually try to continue reading even if I don't understand (just like I continue talking about stuff I don't understand ;-). And equation 5.35 (attached) had a surprise for me. What is that ^ symbol between dx^a and dx^b? >> >> -- >> glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com >> >> <eq-5.35.png>============================================================ >> FRIAM Applied Complexity Group listserv >> Meets Fridays 9a-11:30 at cafe at St. John's College >> lectures, archives, unsubscribe, maps at http://www.friam.org > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org > ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by Grant Holland
Did Verlinde draw the scrabble metaphor? Or was it just Overbye, the
NYT author? From the paper, it's not clear to me that Verlinde was implying that the straightened out (minimum entropy config?) polymer molecule was special in any anthropomorphic sense, just that it was special in the sense of the elastic force. I have two questions about your distinction between "absence of arrangement" and "uncertainty". Isn't all uncertainty evaluated in the context of a particular conceptual target? Similarly, wouldn't any judgment of arrangement or absence thereof be obtained in the context of a particular conceptual target? E.g. Bob can estimate his uncertainty of guessing the arrangement of scrabble chips, as arranged by Joe in another room. And that estimation, were Bob rational and if he thought Joe were rational, would involve some consideration of the physical characteristics of the scrabble chips (tiled plane vs. tiled line, characters upside right vs. upside down or sideways, etc.)? And, if so, then regardless of _which_ particular target configuration (of polymers or scrabble chips) has the [at|in]tention of the predictor, we can estimate the uncertainty associated with each configuration based on its probability of obtaining, including all factors, some purely physical, some psychological, etc? These are rhetorical questions; but I wouldn't mind answers to them anyway because I'm not convinced of my own conclusion that, although arrangement and uncertainty _can_ be distinguished they are not independent. Grant Holland wrote circa 10-07-14 04:38 AM: > Verlinde makes the same unfortunate argument that is made by scores of > scientists - even noted thermodynamicsists - about so-called "disorder": > namely that certain permutations are "disordered", while other > permutations are not. To wit: > > "Think of the universe as a box of scrabble letters. There is only one > way to have the letters arranged to spell out the Gettysburg Address, > but an astronomical number of ways to have them spell nonsense. Shake > the box and it will tend toward nonsense, disorder will increase and > information will be lost as the letters shuffle toward their most > probable configurations. Could this be gravity?" > > I find this argument specious. > > Just because, from an anthropomorphic, English-speaking bias, he finds > the Gettysburg address "more ordered" than any other permutation of the > same length - it is not. They are all permutation of the same number of > letters. Each is as well-defined, and well-ordered, as the other. > > Anyway, "order" is an ill-defined, conflated term within the discussion > of thermodynamics. It enjoys two distinct usages that get oft-conflated > in the conversation regarding entropy. One usage is that it means > "disorganization", "absence of arrangement", "dispersed", etc. This is > approximately the meaning had originally by R. Clausius. The other usage > is that of "uncertainty" or "unpredictability". This is the meaning had > by Shannon. "Disorganized" and "uncertain" do not mean the same thing. I > can prove this because they can vary independently - and, the same > phenomenon can exhibit one without the other - the Organized state can > sometimes be Uncertain... > > In between the meanings of Clausius and Shannon are the meanings of > entropy put forth by Boltzmann and Gibbs. Those meanings are often taken > to be about "disorganization", but they are actually about > "uncertainty". They involve probabilities. So, there is much confusion > within statistical thermodynamics about "entropy", because the > conversation often assumes that "disorder" is about "disorganization", > when it is actually about "unpredictability". Certainly, it is confusing > since Clausius was all about "dispersion", "disorganization", while > these other two physicists, Boltzmann and Gibbs, were actually about > "uncertainty". > > On the other hand, Shannon was not behaving as a physicist, when he > "borrowed" the word "entropy" (upon the insistence of von Neumann) for > his measure of uncertainty. Indeed, he even "borrowed" most of his > formula from Gibbs. However, with his definition of entropy, Gibbs ( and > Boltzmann before him) was doing physics - he was describing a specific > physical phenomenon. > > On the other hand, Shannon was not doing physics. Rather he was doing > mathematical statistics. His definition of entropy is a mathematical > function whose domain space is probability distributions (to use the > term loosely). With Shannon's entropy, any probability distribution now > has a "measure of unpredictability". Some PDFs have more > unpredictability built into them than others, and he measures it. > > Harold Morowitz also makes this point: > > [Shannon’s entropy] is a meaningful measure over any probability > distribution, while [Gibb’s thermodynamic entropy] has meaning only if > the p_i are the probabilities of a system being in the i^th quantum > state when the system is at equilibrium, as rigorously defined for > thermodynamics….[Shannon’s entropy] is a measure on a probability > distribution; it is not a physical quantity.” [Morowitz 1992] > > This is obviously a pet peeve of mine. Welcome any comments! > > Grant p.s. Please excuse the top-posting and full quote... I had some trouble discretizing your post. -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by lrudolph
[hidden email] wrote:
> Glen Ropella asked: > >> What is that ^ symbol between dx^a and dx^b? >> > > Merle Lefkoff writes: I thought a tensor is a description of a multi-dimensional space, like stress and strain (what I'm going through right now). > Roger Critchlow writes: > >> Working from the context, I'd guess: the tensor >> product between the components <i>dx<sup>a</sup></i> >> and <i>dx<sup>b</sup></i>of the stress energy tensor >> <i>T<sub>ab</sub></i>, but I've never been too sure ' >> about tensors. >> > > I haven't read the Verlinde paper (and don't intend > to; I find that treating string theoretical physicists > as ignorable crackpots who, alas, have immense institutional > power makes my life much simpler), but my guess about > the "^" symbol is that it's meant to be the "wedge > product" or "exterior product" rather than the general > tensor product--in other words, it's skew-symmetric. > As an example, in old fashioned terms, the tensor > product of two vectors in R3, a = a1x1+a2x2+a3x3 > and b = b1x1+b2x2+b3x3, where you can make the indices > of ai and bj be lower and those on x be upper if you > like, is the "dyad" ab = a1b1x1x1+a1b2x1x2+...+a3b3x3x3, > which skew-symmetrizes to a^b = (a1b2-a2b1)x1^x2 + > (a1b3-a3b1)x1^x3 + (a2b3-a3b2)x2^x3 (or maybe, depending > on taste, to that divided by 2 or 3 factorial). > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org > > ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: Gravity as an emergent phenomenon
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In reply to this post by Russ Abbott
Russ,
I am just catching up on this but first the analogy to gas distribution is not accurate, or at least I question it from my work in solid state diffusion i.e alloys etc.
There is a dynamic that ultimate results in lower energy states Interacting atoms seem to adopt a kind of neighborliness. They try and balance their energy state to accommodate the neighbor, of course this is not perfect. Since the energy levels are structurally different. For mixtures of similar species my impression is that they just wander about randomly trying to avoid getting excited. This tendency to go low results in the diffused state. Or crystalline system??? Emergence again Perhaps??
Now I can see diffusion as an emergent behavior directly resulting from atoms preferring lower excitement states. But the connection to gravity eludes me. AS it seems to be counter entropic.
Just from a quick reading I was surprised how I thought diffusion was being misunderstood and yet now I am thinking that diffusion may be more likely emergent than the previous link to gravity. How curious. When I was working on the diffusion issue I adopted an approach where dissimilar species were forced to be neighbours and I ran loops for each species trying to adapt to the other and see if there was a stable point between them when they were “Happy” with eachother. I was in hind sight trying to treat each atom as an autonomous agent In a sense without ever having heard the concept. My assumption was that they were only able to adjust electrons but that was very simplistic. The atomic diameter of an atom can change radically depending on how much energy is involved in the electron distributing pattern. Roughly more electrons, smaller diameter and higher energy states. Dumping photons lowers the energy state. Too bad I wrote this stuff so long ago. I almost forgot that in the misty past. So in brief the atoms are struggling to accommodate eachother and constantly altering their diameter and that seems to push them away from eachother hence the emergence of diffusion.
Turns out that there are other mechanics involved. But curious how Emergence shows up in unexpected places. I will read the mail and try and figure out a more refined response.
Vladimyr Ivan Burachynsky Ph.D.(Civil Eng.), M.Sc.(Mech.Eng.), M.Sc.(Biology)
120-1053 Beaverhill Blvd. Winnipeg, Manitoba CANADA R2J 3R2 (204) 2548321 Phone/Fax
-----Original Message-----
I
always find myself confused about how to think about entropy. The article says
that gravity is an entropic force. I understand that to mean that it not
reducible to lower level forces but to be reducible (if that term applies) to
statistical thermodynamics. On Tue, Jul 13, 2010 at 10:36 AM, Nicholas Thompson <[hidden email]> wrote: Pamela, >
============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
entropic force (was Gravity as an emergent phenomenon)
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In reply to this post by Roger Critchlow-2
Roger Critchlow wrote circa 10-07-13 09:07 PM:
> The proposition of entropy causing action at a distance reminded me of a > notorious demonstration. A beaker of water and a beaker of sugar > dissolved in water are sealed together inside a bell jar. Over time the > level of liquid in the beaker of water will drop and the level of liquid > in the beaker of sugar water will rise. For better or worse, I can't stop thinking about this concept that gravity is an entropic force... perhaps especially because I'm lacking a good (any?) understanding of the physics and math. It seems to me that entropic forces can be described as the tendency of systems to move toward, stay in, and return to densely populated regions of configuration space. I.e. if there's a (small/sparse set of) configuration(s) that's isolated (in some sense) from larger, denser sets of configurations, then saying "entropic force" is just a term expressing that the system is more likely to be found in and move toward those larger, denser sets. And then if gravity were such an entropic force, I would be forced to think that, somehow, the close proximity of any two bits (pun intended) of matter allows more configurations than if those two bits are far apart. That would be why gravity is attractive. There are more ways for the bits to interact if they're closer together. I'm not sure why, but this seems counter intuitive to me. I just naively assumed that it doesn't matter how far apart two bits of matter are, the measure of the configurations of the system they constitute is constant.... like two entangled photons at opposite sides of the universe. I suppose my fundamental confusion could be caused by the unnaturalness of cosmic time scales, quantum entanglement, and action at a distance. But it seems inverted for me. I suppose having worked in simulation for so long has brainwashed me. E.g. parallelism can be simulated by serialism, time can be compressed to make slow interactions equivalent to fast interactions, occluded interactions can be ignored as long as there are no side effects of the hidden events, etc. I suppose I've come to think that the universe really does submit/adhere to the closures we stamp onto various sub-systems (holons). But if that were the case, then gravity as an entropic force would not make sense because the configuration space has a constant size no matter how close any bits of matter are. So my question to y'all is: Am I interpreting "entropic force" correctly? What have I misunderstood? -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Glen,
You and Grant are starting to make my poor=old rejected english major's brain spin: I think I have finally seen the point of this whole discussion about gravity. Let it be the case that everything in the universe is in one spot .... that is low entropy right? And we all agree that the world tends to high entropy. So, what's with this gravity thing, which will, eventually, if allowed to play out, bring everything together in a single lump. Nick Nicholas S. Thompson Emeritus Professor of Psychology and Ethology, Clark University ([hidden email]) http://home.earthlink.net/~nickthompson/naturaldesigns/ http://www.cusf.org [City University of Santa Fe] > [Original Message] > From: glen e. p. ropella <[hidden email]> > To: The Friday Morning Applied Complexity Coffee Group <[hidden email]> > Date: 7/16/2010 12:34:15 PM > Subject: [FRIAM] entropic force (was Gravity as an emergent phenomenon) > > Roger Critchlow wrote circa 10-07-13 09:07 PM: > > The proposition of entropy causing action at a distance reminded me of a > > notorious demonstration. A beaker of water and a beaker of sugar > > dissolved in water are sealed together inside a bell jar. Over time the > > level of liquid in the beaker of water will drop and the level of liquid > > in the beaker of sugar water will rise. > > For better or worse, I can't stop thinking about this concept that > gravity is an entropic force... perhaps especially because I'm lacking a > good (any?) understanding of the physics and math. > > It seems to me that entropic forces can be described as the tendency of > systems to move toward, stay in, and return to densely populated regions > of configuration space. I.e. if there's a (small/sparse set of) > configuration(s) that's isolated (in some sense) from larger, denser > sets of configurations, then saying "entropic force" is just a term > expressing that the system is more likely to be found in and move toward > those larger, denser sets. > > And then if gravity were such an entropic force, I would be forced to > think that, somehow, the close proximity of any two bits (pun intended) > of matter allows more configurations than if those two bits are far > apart. That would be why gravity is attractive. There are more ways > for the bits to interact if they're closer together. > > I'm not sure why, but this seems counter intuitive to me. I just > naively assumed that it doesn't matter how far apart two bits of matter > are, the measure of the configurations of the system they constitute is > constant.... like two entangled photons at opposite sides of the universe. > > I suppose my fundamental confusion could be caused by the unnaturalness > of cosmic time scales, quantum entanglement, and action at a distance. > But it seems inverted for me. I suppose having worked in simulation for > so long has brainwashed me. E.g. parallelism can be simulated by > serialism, time can be compressed to make slow interactions equivalent > to fast interactions, occluded interactions can be ignored as long as > there are no side effects of the hidden events, etc. I suppose I've > come to think that the universe really does submit/adhere to the > closures we stamp onto various sub-systems (holons). But if that were > the case, then gravity as an entropic force would not make sense because > the configuration space has a constant size no matter how close any bits > of matter are. > > So my question to y'all is: Am I interpreting "entropic force" > correctly? What have I misunderstood? > > -- > glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Nick Glen Grant,
Another confused old guy, But there was something called Planck's Distance that said that two atoms could not get any closer under normal circumstances without enormous forces yet Bose condensates are literally superimposed indistinguishable atoms albeit identical. From my meager metallurgy days. So there seems to be some kind of stand off between the two. Lets really bend the rules here and speculate that all that we have defined is a figment of our biological failures. We are always making assumptions that we can think, when we might just be spinning old neurons that make us feel good about ourselves. Kind of like a little too much beer and the girls start looking better and better as the night proceeds. With Much regret in the mornings. Perhaps our intelligence is much less than claimed and not even an emergent phenomenon at all. While everything else is. I don't like where this is leading... I have had enough trouble understanding economic theorems now this tsunami of an idea spooks me. I guess it is like Freeman Dyson's one electron universe. It can be everywhere and everywhen to satisfy infinite expectations. Vladimyr Ivan Burachynsky Ph.D.(Civil Eng.), M.Sc.(Mech.Eng.), M.Sc.(Biology) 120-1053 Beaverhill Blvd. Winnipeg, Manitoba CANADA R2J 3R2 (204) 2548321 Phone/Fax [hidden email] -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Nicholas Thompson Sent: July 16, 2010 4:00 PM To: [hidden email] Subject: Re: [FRIAM] entropic force (was Gravity as an emergent phenomenon) Glen, You and Grant are starting to make my poor=old rejected english major's brain spin: I think I have finally seen the point of this whole discussion about gravity. Let it be the case that everything in the universe is in one spot .... that is low entropy right? And we all agree that the world tends to high entropy. So, what's with this gravity thing, which will, eventually, if allowed to play out, bring everything together in a single lump. Nick Nicholas S. Thompson Emeritus Professor of Psychology and Ethology, Clark University ([hidden email]) http://home.earthlink.net/~nickthompson/naturaldesigns/ http://www.cusf.org [City University of Santa Fe] > [Original Message] > From: glen e. p. ropella <[hidden email]> > To: The Friday Morning Applied Complexity Coffee Group <[hidden email]> > Date: 7/16/2010 12:34:15 PM > Subject: [FRIAM] entropic force (was Gravity as an emergent phenomenon) > > Roger Critchlow wrote circa 10-07-13 09:07 PM: > > The proposition of entropy causing action at a distance reminded me of a > > notorious demonstration. A beaker of water and a beaker of sugar > > dissolved in water are sealed together inside a bell jar. Over time the > > level of liquid in the beaker of water will drop and the level of liquid > > in the beaker of sugar water will rise. > > For better or worse, I can't stop thinking about this concept that > gravity is an entropic force... perhaps especially because I'm lacking a > good (any?) understanding of the physics and math. > > It seems to me that entropic forces can be described as the tendency of > systems to move toward, stay in, and return to densely populated regions > of configuration space. I.e. if there's a (small/sparse set of) > configuration(s) that's isolated (in some sense) from larger, denser > sets of configurations, then saying "entropic force" is just a term > expressing that the system is more likely to be found in and move toward > those larger, denser sets. > > And then if gravity were such an entropic force, I would be forced to > think that, somehow, the close proximity of any two bits (pun intended) > of matter allows more configurations than if those two bits are far > apart. That would be why gravity is attractive. There are more ways > for the bits to interact if they're closer together. > > I'm not sure why, but this seems counter intuitive to me. I just > naively assumed that it doesn't matter how far apart two bits of matter > are, the measure of the configurations of the system they constitute is > constant.... like two entangled photons at opposite sides of the universe. > > I suppose my fundamental confusion could be caused by the unnaturalness > of cosmic time scales, quantum entanglement, and action at a distance. > But it seems inverted for me. I suppose having worked in simulation for > so long has brainwashed me. E.g. parallelism can be simulated by > serialism, time can be compressed to make slow interactions equivalent > to fast interactions, occluded interactions can be ignored as long as > there are no side effects of the hidden events, etc. I suppose I've > come to think that the universe really does submit/adhere to the > closures we stamp onto various sub-systems (holons). But if that were > the case, then gravity as an entropic force would not make sense because > the configuration space has a constant size no matter how close any bits > of matter are. > > So my question to y'all is: Am I interpreting "entropic force" > correctly? What have I misunderstood? > > -- > glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Vladimyr Ivan Burachynsky wrote circa 10-07-16 06:53 PM:
> Another confused old guy, But there was something called Planck's Distance > that said that two atoms could not get any closer under normal circumstances > without enormous forces yet Bose condensates are literally superimposed > indistinguishable atoms albeit identical. From my meager metallurgy days. > > So there seems to be some kind of stand off between the two. Right. I think the admission of an "entropic force" (distinct from the non-causal measurement problem pointed out by Russ in the other thread) as a force says something about the _agility_, instability, or sensitivity to perturbation of the system being studied. A completely "disordered" heat death (I assume) is a completely stable, robust equilibrium. So, although we'd say it has maximum entropy, it's actually quite orderly, as it were. On the other hand, as Nick put it, all the matter in the universe lumped into a singularity, which (again, I assume) would mean minimum entropy, is also quite orderly. So, I suppose it's important to remember that entropy is _purely_ a relative term... a way of relating one system to another (or two systems to the third they become when mixed). If there's only a single system, then the term "entropy" is meaningless. If all this rhetoric flows well, then an entropic force is a statement about the difference between the degrees of freedom (wiggle room) between two sets of configurations, _assuming_ some/any microscopic force doing the wiggling (brownian motion, heat, diffusion, particle-mediated fields, ... whatever). In particular, it shows up when the space of configurations is not totally well-mixed. I.e. when some regions of the configuration space have lots of well-connected "points" and other regions are isolated in whatever sense that matters to the hypothetical/unspecified microscopic force. This would all make the conclusion that black holes are _not_ singularities perfectly reasonable. The death of a black hole would just be the system walking that rare/difficult path away from the well-connected region of configuration space out to the ill-connected region of the configuration space of normal space-time. That rare path could happen by a vanishingly rare chance (assuming the hypothetical/unspecified microscopic force is stochastic at all) or due to a bias in the microscopic force that makes the path more likely (e.g. more heat, more mass, more energy, whatever). All this would mean is that a mostly ill-connected universe, sparsely populated by (dynamically evolving) gravity wells keeps the universe in a dynamic equilibrium somewhere between heat death (chaos) and one big lump of condensate (order). (Sorry... I've been brainwashed by Langton. ;-) > Lets really bend the rules here and speculate that all that we have defined > is a figment of our biological failures. We are always making assumptions > that we can think, when we might just be spinning old neurons that make us > feel good about ourselves. Kind of like a little too much beer and the girls > start looking better and better as the night proceeds. With Much regret in > the mornings. Perhaps our intelligence is much less than claimed and not > even an emergent phenomenon at all. While everything else is. Heh, all I can say to that is "So what?" ;-) I already _know_ that all my thoughts are flawed and, likely, mere self-gratification. And, being the self-centered bastard that I am, I tend to think that other people are like me and that all their thoughts are flawed and, likely, just their own self-gratification. (That's why the myth of the free market is so attractive to me.) But you can choose to play the particular game. Or you can choose to hang out on the balcony smoking cigars with the misfits while others play the game at the kitchen table. I'm just making a small attempt to play the game... or perhaps learn enough about the game to know I wouldn't have any fun playing it. When I get tired, bored, or lazy, I'll quit. -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Under the information-based view of entropy a heat death universe would have high entropy because it would take a large amount of information--a great many bits--to capture it. One would have to say where each bit of material is. Since each bit is more or less randomly located, there is no way to compress that information. On the other hand, if all matter were compressed into a single point, it would take very little--very few bits--to record that state of the universe.
-- Russ On Mon, Jul 19, 2010 at 3:41 PM, glen e. p. ropella <[hidden email]> wrote: Vladimyr Ivan Burachynsky wrote circa 10-07-16 06:53 PM: ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Russ Abbott wrote circa 10-07-19 03:54 PM:
> Under the information-based view of entropy a heat death universe > would have high entropy because it would take a large amount of > information--a great many bits--to capture it. One would have to say > where each bit of material is. Since each bit is more or less randomly > located, there is no way to compress that information. On the other > hand, if all matter were compressed into a single point, it would take > very little--very few bits--to record that state of the universe. You seem to be repeating things I just said. ;-) But that's not the interesting part of what I said. The interesting part is that no work can be done in either case. In fact, neither end of the spectrum is interesting at all. Interestingness lies between heat death and singularity. A further interesting thing (perhaps only to my self-gratifying thoughts) is that the maximal entropy heat death actually _can_ be described with very little information. All it takes is a uniform RNG distribution. I can write that program in... 5 minutes! ;-) Seriously though, it all depends on what layer, stance, or aspect taken by the observer. And if the universe is in a state of heat death, there is no observer. So, again, the concept of "entropy" becomes meaningless in heat death. Entropy is only meaningful in between the heat death and the singularity. I.e. it's only a relative term. It's degenerate in any absolute/universal context. -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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On Mon, Jul 19, 2010 at 4:13 PM, glen e. p. ropella <[hidden email]>
wrote:
A further interesting thing (perhaps only to my self-gratifying
thoughts) is that the maximal entropy heat death actually _can_ be
described with very little information. All it takes is a uniform RNG
distribution. I can write that program in... 5 minutes! ;-) I guess that's a joke. But to be overly literal minded, one random distribution of elements is not the same as another random distribution any more than one string of random digits is the same as another string of random digits--unless of course they just happen to be identical. Of course they have a lot of properties in common, but one might just happen to be the first n digits of pi, whereas the other might not be. Seriously though, it all depends on what layer, stance, or aspect taken by the observer. And if the universe is in a state of heat death, there is no observer. As I said, I struggle with the notion of entropy, but as I understand it no observer is needed. I think it's well defined in both the information and thermodynamics senses without relying on an observer. Why do you say it relies on an observer? -- Russ On Mon, Jul 19, 2010 at 4:13 PM, glen e. p. ropella <[hidden email]> wrote: Russ Abbott wrote circa 10-07-19 03:54 PM: ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Russ Abbott wrote circa 07/19/2010 05:06 PM:
> On Mon, Jul 19, 2010 at 4:13 PM, glen e. p. ropella > <[hidden email] <mailto:[hidden email]>> > wrote: > > I guess that's a joke. But to be overly literal minded, one random > distribution of elements is not the same as another random distribution > any more than one string of random digits is the same as another string > of random digits--unless of course they just happen to be identical. Of > course they have a lot of properties in common, but one might just > happen to be the first n digits of pi, whereas the other might not be. Yeah, sorry. I never learned to tell jokes. Yes, I agree that it's not as simple as a distribution of an RNG. It would have to be a real RNG, anyway, I suspect. And that would imply more than 1 system: the one being described and the one generating the random numbers for the description. But my underlying point still stands: that when characterizing a physical system (with concepts like entropy and thermodynamics as a whole), one has to choose the layers or aspects they want to pay attention to. If the characterization is intended to capture the details of every particular element (boson, lepton, virtual particle pair, etc. in its position, velocity, spin, etc.), then the description _would_ be as large as the universe, itself. There could be no abstraction in such a characterization, making it useless as a model. >> Seriously though, it all depends on what layer, stance, or aspect taken >> by the observer. And if the universe is in a state of heat death, there >> is no observer. > > As I said, I struggle with the notion of entropy, but as I understand it > no observer is needed. I think it's well defined in both the information > and thermodynamics senses without relying on an observer. Why do you > say it relies on an observer? Well, I'm using a rather naive definition of entropy that depends on there being 2 systems to compare. The total entropy of one (closed) system is only useful when comparing it to another (closed) system, distinct in any variable like space or time. When talking about an increase in entropy for a single system, we compare the system at time t_0 to that same system at time t_1. Even in that case, entropy is a measure applied to 2 different systems. We often choose to call it the same system and refer to it as changing state; but in practice, it's the same measure used to compare 2 separate systems (non-causally derived from measures of heat and causally derived from measures of the states of its constituents). The observer is necessary to do the measuring. If the observer is _inside_ the system, then that results in an infinite regress. So, an observer measuring the entropy of the universe from inside can, at best, approximate (or show a bound for) the total entropy. And the only point in placing the whole universe in that metric space (the entropy quantity) is to compare it to other systems, subsets of itself or the whole universe at different times. -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Please see below.
-- Russ But my underlying point still stands: that when If all the particles were arrayed in a regular lattice, the description could be smaller than the universe itself. I thought that was the point of entropy.
Whether it's one system or two, a messy arrangement takes more work
to describe than a neat one. This is a perspective from outside the system, but it would seem to be a perspective in which entropy makes sense without having to say anything special about an observer. Of course whenever we say anything about anything there is an implied observer, but we don't complain about that in other contexts. ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: entropic force (was Gravity as an emergent phenomenon)
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Russ Abbott wrote circa 07/20/2010 09:55 PM:
> If all the particles were arrayed in a regular lattice, the description > could be smaller than the universe itself. I thought that was the point > of entropy. Perhaps you're right. But that is also counter-intuitive to me. If entropy really is a measure of "disorder" in any sense, then it's hard for me to imagine a maximal entropy state as describing a completely smooth landscape where every element sits on a point in a regular lattice. But physically, entropy is about the ability to do work. So, it seems to me that our understanding of the concept of "heat death" needs a little more emphasis on "heat", which describes the vibration of particles and says nothing about any microscopic patterns. A heat death doesn't describe particles laid out on a regular lattice. It's about not being able to _use_ any of the microscopic activity, whether you know what that activity is (data about the degrees of freedom for every particle) or not. Still, a shortest description of it can be made by uniform RNGs over all the potential degrees of freedom for elements spread more or less evenly, though not necessarily _totally_ ... omnisciently, god-like, regular lattice evenly, through the universe. In order to get that short description, though, you have to abstract yourself from the microscopic detail. The RNG distribution demarcates the ontological wall, behind which we're completely ignorant (e.g. "heat"). A fully concrete, non-abstract model would be the same "size" as the universe itself, even in heat death. > This is a perspective from outside the system, > but it would seem to be a perspective in which entropy makes sense > without having to say anything special about an observer. Of course > whenever we say anything about anything there is an implied observer, > but we don't complain about that in other contexts. I don't see how it's possible to talk about a perspective from outside the system without talking about an observer, even if that observer is just another, separate, system. That was the whole point. Entropy only seems like a coherent concept in the context of 2 or more systems, making either extreme (heat death of the universe or all matter inside a singularity) degenerate cases. -- glen e. p. ropella, 971-222-9095, http://agent-based-modeling.com ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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