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Le vocabulaire courant de la vulgarisation scientifique, de même que le vocabulaire scolaire le plus répandu, associe la notion d'entropie à la notion de désordre, sinon de chaos, et projette peu ou prou cette notion vers le futur lointain de l'univers comme sa mort thermique probable supposée...
Le principe de la conservation de l'énergie, supposément « acquis », comme connaissance, dès la 3ème des collèges, est aussitôt associé aux notions de « consommation » et d' « économie » d'énergie, de la manière à la fois la plus contradictoire et la plus absurde qui soit : une doxa supposément « écologique » et « économique » remplace donc aussitôt la réalité scientifique dans quasiment tous les esprits, et durablement. Une des rares « victoires » de la pseudo- « durabilité » en « écologie » : celle de l'imbécilité, de la servilité à une nouvelle quasi-religion aussi stupide et dogmatique que toutes les précédentes et souvent plus ou moins associée, tant qu'à faire, dans une « interprétation » complètement dévoyée du concept de laïcité.
Pourtant, dès 1865, Clausius avait éclairé le monde et la société humaine, ou du moins, la partie qui voulait bien regarder la réalité en face, sur le devenir « énergétique » de l'univers, en fondant le concept d'entropie, notamment avec sa célèbre Deuxième loi de la Thermodynamique.
Ce concept radicalement réaliste n'a pour autant pas empêché les esprits les plus éclairés au sens de la logique d'y intégrer le cours de l'évolution, et notamment le cours de l'évolution du vivant.
Mais il est clair qu'intégrer le cours de l'évolution du vivant dans un processus qui annonce logiquement la mort thermique de l'univers est une démarche fondamentalement et même littéralement iconoclaste, voire carrément « sacrilège » au regard des dogmes religieux et idéologiques.
La « finitude » de la vie humaine, de même que la soumission à l'ordre établi, n'est une « valeur » socialement et culturellement admise qu'avec l'espoir illusoire d'une « transcendance » de l'humanité au regard de l'éternité, qu'elle soit « spirituelle » ou même seulement « historique ».
Vivre lucidement avec la réalité de la finitude du phénomène humain, que ce soit à l'échelle individuelle ou à l'échelle cosmique, c'est quasiment le début d'une véritable révolution culturelle, celle qui permettrait enfin vraiment à l'humanité de prendre son destin en main, pour le temps qui lui reste, et dont la prolongation éventuelle, même si nécessairement pas infinie, ne dépend donc que de son libre-arbitre, pourvu qu'elle se décide enfin à en user : inaboutie en pratique, c'est pourtant, jusqu'à présent, sa plus grande conquête, en termes d'évolution.
Luniterre
PS: comme on l'a vu, la relation entre l'entropie et la vie était donc finalement au cœur du débat suite à la republication sur AgoraVox de:
Ilya Prigogine et il y a le temps ...et le bon côté de l'entropie
Ilya Prigogine et il y a le temps ...et le bon côté de l’entropie ! (Débat sur AgoraVox)
Ilya Prigogine et il y a le temps ...et le bon côté de l’entropie ! (Eléments complémentaires)
Dans le prolongement de ce débat nous continuons donc à publier des liens et des extraits d'articles et même d'ouvrages scientifiques sur le sujet. Roderick Dewar, notamment cité par feu François Roddier dans un texte cité au cours du débat, est l'un des continuateurs les plus éminents dans ce domaine de recherches. En 2014 il a initié un ouvrage collectif et pluridisciplinaire autour du thème commun de la Deuxième Loi de la Thermodynamique. Un extrait de sa présentation et deux extraits des chercheurs associés à ce projet, avec en plus un lien vers cet ouvrage gratuitement disponible, à la suite! Même si seulement les parties de commentaires épistémologiques seront accessibles à la plupart des profanes et ne constituent que des parties spécifiques de l'ouvrage, le moins que l'on puisse dire est qu'il vaut tout de même le déplacement!
A la suite encore trois extraits de recherches plus récentes et un quatrième, de 2017, en hommage pour le centenaire de la naissance d'Ilya Prigogine, mais pas seulement hagiographique au sens usuel du terme: c'est aussi précisément un rappel salutaire du caractère iconoclaste de sa démarche!
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NDLR : le lien vers le livre de Roderick Dewar se trouve à la suite du spot des pubs mensongères qui nous sont imposées ici par le système depuis la fusion « eklablog-overblog-webedia »
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Beyond The Second Law:
Entropy Production
And Non-equilibrium Systems
INTRODUCTION
DEWAR PAGE 4 - R. C. Dewar et al.
1.1 The Challenge: Understanding and Predicting Non-equilibrium Behaviour
Non-equilibrium dissipative systems abound in nature. Examples span the biological and physical worlds, and cover a vast range of scales: from biomolecular motors, living cells and organisms to ecosystems and the biosphere; from turbulent fluids and plasmas to hurricanes and planetary climates; from growing crystals and avalanches to earthquakes; from cooling coffee cups to economies and societies; from stars and supernovae to clusters of galaxies and beyond.
A characteristic feature of all open, non-equilibrium systems is that they import energy and matter from their surroundings in one form and re-export it in a more degraded (higher entropy) form. A sheared viscous fluid driven out of thermo dynamic equilibrium by the external input of kinetic energy eventually dissipates and expels that energy to its environment as heat; the Earth absorbs short-wave radiation at solar temperatures and re-emits it to space as long-wave radiation at terrestrial temperatures; living organisms use the chemical free energy ultimately derived from photons to grow and survive, eventually dissipating it to their environment as heat and carbon dioxide.
In association with these exchanges of energy and matter, spatial gradients in temperature and chemical concentration are set up and maintained, both internally and between the system and its environment. The patterns of flows and their associated gradients self-organize into intricate dynamical structures that continually transport and transform energy and mass into higher entropy forms: thus emerge plant vascular systems, food webs, river networks, and turbulent eddies such as Jupiter’s Red Spot and the convective cells on the Sun’s surface. Idealised systems in equilibrium with their surroundings exhibit no flows or gradients; they appear static, structureless, lifeless. In stark contrast, non-equilibrium systems, even purely physical ones, appear to be alive in a sense that perhaps even defines life itself, at least thermodynamically.
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The Time Evolution of Entropy Production in Nonlinear Dynamic Systems
DEWAR PAGE 116 - H. Ozawa and S. Shimokawa
6.1 Introduction
Since an early investigation by Ziegler [1], maximum entropy production (MaxEP) has been suggested as a general thermodynamic property of nonlinear non equilibrium phenomena, with later studies showing that the MaxEP state is consistent with steady states of a variety of nonlinear phenomena. These include the general circulation of the atmosphere and oceans [2, 3], thermal convection [4], turbulent shear flow [5], climates of other planets [6], oceanic general circulation [7, 8], crystal growth morphology ([9]; Martyushev, this volume) and granular f lows [10]. While the underlying physical mechanism is still debated, the MaxEP state is shown to be identical to a state of maximum generation of available energy [11, 12]. Moreover, recent theoretical studies suggest that the MaxEP state is the most probable state that is realized by non-equilibrium systems ([13, 14]; Dewar and Maritan, this volume).
It is known, however, that entropy production in a linear process tends to decrease with time and reach a minimum in a final steady state when a thermodynamic intensive variable (such as temperature) is fixed at the system boundary. This tendency was first suggested for a linear chemical process in a discontinuous system by Prigogine [15], and then extended to the case of a linear diffusion process in a continuous system [16]. Since then, this minimum entropy production (MinEP) principle has become widely known in the field of non-equilibrium thermodynamics. Although a number of attempts have been made to extend this MinEP principle to a general one including nonlinear processes, the results remain controversial and inconclusive (e.g. [17, 18]). In fact, Prigogine [19] explained the situation as: “It came as a great surprise when it was shown that in systems far from equilibrium the thermodynamic behavior could be quite different—in fact, even directly opposite that predicted by the theorem of minimum entropy production.” Sawada [20] pointed out the limitations of the MinEP principle, and instead proposed the MaxEP principle as a general variational principle for non linear systems that are far from equilibrium. More recently, Dewar and Maritan (this volume) showed using Jaynes’smaximum entropy method that a state of minimum dissipation (MinEP) is selected for a system without dynamic instability, whereas that of maximum dissipation (MaxEP) is selected for a system with dynamic instability. It seems therefore that the existence of dynamic instability plays a key role in deter mining the behavior of entropy production in nonlinear non-equilibrium systems. However, the nature of the dynamic instability as well as its relation to nonlinearity remains unclear. Moreover, until now, we do not have a reasonable specification of the dynamic conditions under which the MinEP or MaxEP state is realized. In order to clarify the issues in the phenomena mentioned above, we have investigated the behavior of time evolution of entropy production in a fluid system. Based on a general expression of entropy production and balance equations of energy and momentum, we present a condition under which the MinEP state is realized in the course of time in a system of linear diffusion (Sect. 6.2). We then add nonlinear advection terms in the balance equations, and examine the condition under which the MinEP state becomes unstable and the MaxEP state is realized in the system (Sect. 6.3). We show that the rate of advection of heat or momentum plays an important role in the enhancement of entropy production in a fluid system that possesses dynamic instability. Results obtained from this study are compared with the observed state of vertical atmospheric convection, a typical example of nonlinear dynamic phenomena (Sect. 6.4).
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The Entropy of the Universe and the Maximum Entropy Production Principle
DEWAR PAGES 418-422 - C. H. Lineweaver
22.2 The Entropy Gap and the Initial Entropy of the Universe
The early universe was close to thermal equilibrium. Direct evidence for this comes from the high level of isotropy of the temperature maps of the cosmic microwave background (CMB) [11, 12]. CMB photons give us a direct view of the universe as it was *380,000 years after the big bang when the entire universe had a temperature of *3,000 K. Tiny temperature fluctuations in the CMB maps have a DT/T * 10-5. That is, the anisotropies seen in the maps (hot spots and cold spots) are deviations of amplitude DT * 30 lK around the current average temperature T = 3 K. If CMB photons were its only component, the universe would have started out in equilibrium, at maximum entropy (DS = 0) and would have stayed there. Nothing would have happened and no life would be possible. Such a universe is unobservable by life forms of any kind. The second law of thermo dynamics (Eq. 22.1) tells us that as long as life or any other irreversible dissipative process exists in the universe, the entropy of the universe Suni will increase. Thus the entropy of the very early universe had to have some initially low value Sinitial, where ‘‘low’’ means low enough compared to the maximum possible entropy Smax so that the entropy gap DS (=Smax- Suni(t)) was large and could produce and support irreversible processes, such as stars and life forms [1] (Fig. 22.2).
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Trying to understand the low initial entropy of the universe is an important unresolved issue of cosmology [13–16]. Figure 22.3 summarizes a few hypothe ses. The ‘‘uniform’’ distribution in Fig. 22.3 is just a toy model without physical justification. However, physically plausible arguments can be made for both the ‘‘Penrose’’ and the ‘‘smooth energy dump’’ distributions. In standard thermodynamics there are many more ways to be at high entropy than at low entropy. Motivated by this idea and applying it to the early universe, Penrose makes the assumption that there are many more ways for the universe to have had high initial entropy than low initial entropy. Thus he refers to ‘‘our extraordinarily special big bang’’ ([14], p 726, Chap 27 and Fig. 27.4) because contrary to his assumption and expectation, our universe started out at low entropy.
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If there are many more ways to be at Smax (in the absence of other constraints) Penrose would be correct that it is much more likely that the universe should have been born at or near maximum entropy (and our expectations should be that Sinitial * Smax). However, at the beginning, did the universe have access to all those ways? Or were there constraints associated with the origin of matter that restrict the universe to having a smooth matter distribution and therefore low gravitational entropy? It is possible that there were physical constraints associated with the physics of inflation. Inflation starts from an initially smooth distribution of false vacuum energy (quantum fluctuations of false vacuum, this can also be understood as a higher zero-point energy than the current zero-point energy of the vacuum state of the universe). See [15]. Part of the definition of vacuum energy is that it does not, and cannot clump. This false vacuum energy is homogeneously distributed (sub ject to quantum fluctuations). When the false vacuum decays during reheating creating all the energy and matter in the universe, it may only be possible for this to happen as a smooth energy dump, resulting in a universe with a relatively smooth distribution of matter (and therefore low initial gravitational entropy). Thus inflation provides a natural initial condition that could explain why the initial entropy of our universe (Sinitial in Fig. 22.2) is so low. Homogeneously distributed matter (i.e. with low gravitational entropy) could well be an initial constraint (boundary condition) associated with the origin of matter from false vacuum energy. The low gravitational entropy of the homogeneously distributed matter is what gives the universe its low initial entropy [1, 16]. Penrose ([14], p 706) explains: “A uniformly spread system of gravitating bodies would represent relatively low entropy (unless the velocities of the bodies are enormously high and/or the bodies are very small and/or greatly spread out, so that the gravitational contributions become insignificant), whereas high entropy is achieved when the gravitating bodies clump together.”
For an elaboration of this view see [17–19].
22.2.1 Anthropic Reasoning Cannot Rescue Penrose’s Model
In Penrose’s model, if the initial entropy is too close to Smax, the entropy gap DS will not be large enough to produce stars and life. Thus, in Penrose’s model, an anthropic argument (in the context of a multiverse scenario in which the proba bility distribution of Sinitial,P(Sinitial) is exhaustively sampled) has to be invoked to explain why Sinitial Smax [20]. That is, although universes with Sinitial * Smax greatly outnumber universes with low initial entropy, life (and observers like us) are only possible in universes with low initial entropy.
Sagan [21] has poetically described the low entropy requirements for life: ‘‘If you wish to make an apple pie from scratch, you must first invent the universe.’’ However, the entire universe did not have to be at low entropy in order for our part of the universe to have low entropy. Feynman [22] discussed the idea of whether our low entropy part of the universe could be a low entropy fluctuation, i.e. a low entropy sub-set of a larger universe that is much closer to maximum entropy:
“[F]rom the prediction that the world is a fluctuation, all of the predictions are that if we look at a part of the world we have never seen before, we will find it mixed up, and not like the piece we just looked at. If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it…Every day [astronomers] turn their telescopes to other stars, and the new stars are doing the same thing as the other stars. We therefore conclude that the universe is not a fluctuation, and that the order is a memory of conditions when things started. This is not to say that we understand the logic of it. For some reason, the universe at one time had a very low entropy for its energy content, and since then the entropy has increased.”
Feynman’s argument, based on new stars coming into view, can be made more rigorous by basing it on the increasing particle horizon. If we are living in a rare low entropy fluctuation that has enabled us to be here, then when we view previously unobserved parts of the universe (more specifically when we observe parts of the universe that we had not been in causal contact with), we should find them to be close to maximum entropy. The entropy fluctuation that made us should be of minimal extent. As the size of the observable universe increases, new parts of the universe that were out of causal contact, come into causal contact—new regions of the universe appear over the horizon [23]. If our part of the universe were a low entropy fluctuation, then the new parts coming over the horizon would tend to be of higher entropy. This does not seem to be the case. The distant universe seems to be at low gravitational entropy. Our observations that the distant universe is in a state of low entropy is inconsistent with the expected rarity of such low entropy states. This rarity can be quantified by the ratio of the probability of the high entropy state (with Whi microstates) to the probability of the low entropy state (with fewer Wlo microstates) [24]:
P Shi ð Þ=P Slo ð Þ¼Whi=Wlo ¼exp Shi Slo ð Þ=k ½ ð22: 4Þ
Low entropy regions of the universe are not only rare, they are also much more likely to fluctuate to higher entropy than to fluctuate to lower entropy. How much more likely is given by the fluctuation theorem [25]:
PðdSi=dt ¼ rÞ=PðdSi=dt ¼ rÞ¼expðrt=kÞ ð 22:5Þ
which can be cosmologically interpreted as follows: If some part of the universe (indexed by the subscript i) is not at equilibrium (Si\Si,max), then during a subsequent time t, this part of the universe is much more likely to increase its entropy at a positive rate r and fluctuate toward equilibrium (Si,max) than it is to f luctuate further from equilibrium at a rate-r. How much more likely is given by the expression exp(rt/k).
The Feynman quote ends with an unresolved issue: ‘‘For some reason, the universe at one time had a very low entropy for its energy content…’’ To resolve the issue of the initial entropy of the universe, Carroll [16] has suggested that either we just accept the initial condition without asking why, or that the big bang is not the beginning. The first is the abandonment of scientific cosmology and the second is a very poorly supported speculation. Penrose and Tegmark [14, 20] use anthropic reasoning, but it seems like overkill since it should only apply to the minimal sized local patch needed to create us. However, as mentioned earlier, the inflationary origin of matter from unclumped false vacuum energy may produce a low gravitational entropy universe everywhere it has produced matter. This could be the reason for the initial low entropy of the universe.
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Quatre extraits récents de la continuation
de la recherche dans le domaine
des structures dissipatives:
Dissipative Structures, Organisms and Evolution
Dilip K Kondepudi, Benjamin De Bari, and James A. Dixon
2020 https://pmc.ncbi.nlm.nih.gov/articles/PMC7712552/
Abstract: Self-organization in nonequilibrium systems has been known for over 50 years. Under non equilibrium conditions, the state of a system can become unstable and a transition to an organized structure can occur. Such structures include oscillating chemical reactions and spatiotemporal patterns in chemical and other systems. Because entropy and free-energy dissipating irreversible processes generate and maintain these structures, these have been called dissipative structures. Our recent research revealed that some of these structures exhibit organism-like behavior, reinforcing the earlier expectation that the study of dissipative structures will provide insights into the nature of organisms and their origin. In this article, we summarize our study of organism-like behavior in electrically and chemically driven systems. The highly complex behavior of these systems shows the time evolution to states of higher entropy production. Using these systems as an example, we present some concepts that give us an understanding of biological organisms and their evolution.
D. K. KONDEPUDI 2020 Dissipative Structures, Organisms and Evolution
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On the Thermodynamics of Self Organization in Dissipative Systems: Reflections on the Unification of Physics and Biology
Bong Jae Chung, Benjamin De Bari, James Dixon, Dilip Kondepudi, Joseph Pateras and Ashwin Vaidya
2022 https://www.mdpi.com/2311-5521/7/4/141
[...]Such variational theories are not new; they have been in existence for decades and gained popularity through the Nobel Prize-winning work of theorists such as Lars Onsager and Ilya Prigogine. The arguments have evolved since then to include systems of higher complexity and for nonlinear systems, though a comprehensive theory remains elusive. The overall attempt is to bring out examples from physics, chemistry, engineering, and biology that reveal deep connections between variational principles in physics and biological, or living systems. There is sufficient evidence to at least raise suspicion that there exists an organization principle common to both living and non-living systems, which deserves deep attention.
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A Drive towards Thermodynamic Efficiency for Dissipative Structures in Chemical Reaction Networks
Kai Ueltzhöffer, Lancelot Da Costa, Daniela Cialfi and Karl Friston
Entropy 2021, 23, 1115. https://doi.org/10.3390/e23091115
Contrary to the—still widely held—belief that life is a struggle against the second law of thermodynamics, recent advances in nonequilibrium thermodynamics successfully recast biological systems as a subclass of dissipative structures. The formation of such dissipative structures is statistically favoured by (generalizations of) the second law of thermodynamics, because their existence enables the dissipation of reservoirs of free energy, which could not be accessed otherwise. Therefore, their formation facilitates the irreversible relaxation of the associated disequilibria [1–5]. In other words, dissipative structures constitute channels in the universe’s highly structured state space, which enable transitions from one frustrated, metastable state to another metastable state of higher entropy [6]. This line of thinking dates back at least to the work of Lotka, who tried to relate natural selection to a physical principle of maximum energy transformation [7,8]. Dissipative structure formation has been well understood for many systems in the near equilibrium, linear-response regime, due to the work of Prigogine and colleagues in the 1960s and 1970s [9], leading to the notion of biological systems as a class of self-organising free energy-conversion engines [10].
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Dissipative structures and irreversibility in nature: Celebrating 100th birth anniversary of Ilya Prigogine (1917–2003)
Friends and colleagues who knew Ilya Prigogine well called him “A poet of thermodynamics.” It is an apt description. When Prigogine talked about thermodynamics and irreversible processes, one had the sense he understood or knew more than what his words conveyed. Natural processes all around us are irreversible; it is a fact. Their consequence is not merely to increase the entropy of the universe and destroy order. They can also do the opposite: create highly ordered complex structures with extraordinary properties and create life itself. Prigogine saw this as a profound aspect of nature that thermodynamics has revealed. When he came across the famed South Indian sculpture of Nataraja, the dancing Shiva, that depicts as a cosmic dance the perfect balance between creation and destruction that originate from the same source, he made sure he had a bronze statue of Nataraja of highest artistic quality in his art collection. A picture of it became the cover art for the book Thermodynamic Theory of Structure Stability and Fluctuations, that he coauthored with Paul Glansdorff. It was poetry of thermodynamics, creation and destruction emerging from a common source, a perfectly balanced cosmic dance. One could surmise all this from Prigogine's discourses on thermodynamics.
Celebrating 100th birth anniversary of Ilya Prigogine
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Malheureusement, on ne trouve qu'un extrait de ce livre en version PDF:
Thermodynamic-theory-of-structure-stability-and-fluctuations-Glansdorff-Prigogine-1971
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