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Author
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Topic: Life: process that decreases entropy locally
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Jurie
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Member # 716
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posted 03. March 2004 17:07
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In fact growing increases entropy locally. Two kilograms of water has exactly twice the entropy of one kilogram of water at the same conditions. By the same token, a seed or baby rabbit has very little mass, so very low entropy compared with the tree or adult rabbit.
I wonder if you are correct here.
Adding plain disordered mass, yes. But the order in a tree growing from a seed is increased compared to just a seed and CO2 and water dispersed in the environment.
Another point is that in living processes, the maintenance of the low state of entropy requires a continuous expense of energy. In self-organising structures like Benard cells, the energy is used once to set up the order.
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Rex Kerr
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posted 03. March 2004 21:31
I think you will have to try again on making the "against the flow" intuition rigorous. Entropy is locally maximized, not globally.
For example, if I have a balloon filled mostly with hydrogen, there's still going to be a bit of oxygen inside. Entropy would be increased if it went from H2+O2 -> 2H2O right away, but it doesn't. Further still, if the hydrogen could only smash a hole in the balloon and combust with the air around it, there would be a massive increase in entropy. Yet, this doesn't happen--the hydrogen leaks out slowly and mixes in with the atmosphere.
Or consider the Amazon river. How much shorter it would be if the river "simply" went through the Andes into the Pacific, rather than all the way across Brazil into the Atlantic! But, no, the Amazon river and combustion and so on simply obeys local rules--downhill is that way right here right now, so that's the way the water flows.
But this is exactly what the Krebs Cycle does. It maximizes entropy locally--it just so happens that in so doing it converts sugar into ATP (quite efficiently, I might add). Thermodynamics can't see far enough into the future to figure out how to escape biochemistry, or balloons, or the Andes.
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Jurie
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posted 04. March 2004 01:44
Rex Kerr wrote:
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I think you will have to try again on making the "against the flow" intuition rigorous.
Agreed. I also see that one concept is apparently misunderstood - that of maximal entropy production. I think maybe I have caused confusion by not using the correct terminology. The Law of Maximal Entropy Production (assuming this law exists) says that systems will settle into that state which produces entropy at the maximal rate. For example, in the Benard cell experiment, after the liquid settles into the Benard cell configuration, heat is transferred through the liquid faster than before, so the rate of entropy production is maximised.
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For example, if I have a balloon filled mostly with hydrogen, there's still going to be a bit of oxygen inside. Entropy would be increased if it went from H2+O2 -> 2H2O right away, but it doesn't. Further still, if the hydrogen could only smash a hole in the balloon and combust with the air around it, there would be a massive increase in entropy.
Or consider the Amazon river. How much shorter it would be if the river "simply" went through the Andes into the Pacific, rather than all the way across Brazil into the Atlantic!
Those are invalid examples - valid entropy production paths are only those that are possible, and out of all possible paths, non-life processes follow those paths that maximise the rate of entropy production. The Amazon flowing over the Andes is obviously impossible. So the Amazon flows through Brazil because that is a possible entropy production path. Same with the hydrogen/balloon example.
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But this is exactly what the Krebs Cycle does. It maximizes entropy locally--it just so happens that in so doing it converts sugar into ATP.
I don't think so - I think entropy is not produced at the maximum rate along the path of the Krebs cycle, because the energy is stored in a different free form. A path that maximises the rate of entropy production would be that in which the energy is turned into heat in the fastest possible way. That clearly is not what we find in the Krebs cycle, since energy is converted to a low entropy form ie ATP, instead of the highest entropy form, ie heat. I can't give an alternative path than the Krebs cycle that would increase the rate of entropy production, I have to study the case first, or perhaps one could be suggested by someone else.
I can suggest a entropy rate maximising path for ATP synthase. Its action is rather like a battery-driven electric motor that is doing useful work, like pumping water. Electric charge flows through the motor coil. The magnetic field resists the flow of charge, setting up a torque in the rotor, which then does useful work. If we disconnect the motor's axle from the pump, then the motor would spin at the maximum rate, producing only heat in the process while draining the battery.
The same with ATP synthase. Protons (charge) flows from a positive to a negative potential, turning the spindle which does the work of binding ADP and Pi. The Fo turbine resists the flow of protons, setting up a torque in the rotor that does the work of binding ADP with Pi. If we take away the gamma spindle, then the potentials will simply equalise while the Fo rotor spins rapidly and produces heat in the process.
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The Pixie
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Member # 548
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posted 04. March 2004 09:48
Jurie
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Adding plain disordered mass, yes. But the order in a tree growing from a seed is increased compared to just a seed and CO2 and water dispersed in the environment.
I assumed you were considering the organism alone when you said entropy decreases locally, and not the environment...
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Another point is that in living processes, the maintenance of the low state of entropy requires a continuous expense of energy. In self-organising structures like Benard cells, the energy is used once to set up the order.
As I understand it, the Benard cell requires a temperature difference; there is heat energy being transferred across the system, and so a continuous influx of energy.
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The Law of Maximal Entropy Production (assuming this law exists) says that systems will settle into that state which produces entropy at the maximal rate.
I think this may be a factor, but others exist too. To build on Rex's example, a balloon full of oxygen and hydrogen will sit there quite happily, despite the fact that the reaction to make water will produce a lot of entropy. The problem is the activation energy. You require a little bit of energy to get the hydrogen and oxygen to come together. Put a lighted match to the balloon, and you supply the energy; the oxygen and hydrogen react explosively (and indeed I saw this done as a demonstration of activation energy at school).
The activation energy can prevent a reaction that produces more entropy. Let me illustrate with an obscure chemistry reaction, the dimerization of hexafluoropropene with fluoride:
CF2=CFCF3 --> (CF3)2C=CFCF2CF3 + (CF3)CFCF2CF=CF2
There are two products, a "thermodynamic isomer" and a "kinetic isomer". At moderate temperature there is not enough energy to make the thermodynamic isomer; you cannot get over the activation energy, but you can still make the kinetic isomer. On the other hand, at high temperature, the activation energy is not an issue, and your Law of Maximal Entropy Production applies. The system goes to the thermodynamic isomer, because that produces the most entropy.
You kind of touch on this:
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Those are invalid examples - valid entropy production paths are only those that are possible, and out of all possible paths, non-life processes follow those paths that maximise the rate of entropy production. The Amazon flowing over the Andes is obviously impossible. So the Amazon flows through Brazil because that is a possible entropy production path. Same with the hydrogen/balloon example.
Right, so hydrogen plus oxygen to make water is not a valid entropy path under certain conditions, but if you change the conditions, by adding energy, it is a valid entropy path. The problem you run into is in the intermediate area. For the dimerization of hexafluoropropene at intermediate temperature you get both the kinetic isomer and the thermodynamic isomer. Things are just not that simple, sadly.
The Pixie
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Rex Kerr
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posted 04. March 2004 12:18
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The same with ATP synthase. Protons (charge) flows from a positive to a negative potential, turning the spindle which does the work of binding ADP and Pi. The Fo turbine resists the flow of protons, setting up a torque in the rotor that does the work of binding ADP with Pi. If we take away the gamma spindle, then the potentials will simply equalise while the Fo rotor spins rapidly and produces heat in the process.
But the spindle is there, so you have just appealed to an inaccessible pathway. How is this different than saying, "If there was a hole (or lit match) in the balloon, entropy would increase"? The point is, there is not a hole in the balloon.
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Jurie
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posted 04. March 2004 16:52
Pixie wrote: quote:
I assumed you were considering the organism alone when you said entropy decreases locally, and not the environment...
I need to make the various definition clearer. This discussion is useful since it shows clearly the various weaknesses there are at the moment.
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Right, so hydrogen plus oxygen to make water is not a valid entropy path under certain conditions, but if you change the conditions, by adding energy, it is a valid entropy path. The problem you run into is in the intermediate area. For the dimerization of hexafluoropropene at intermediate temperature you get both the kinetic isomer and the thermodynamic isomer. Things are just not that simple, sadly.
Agreed. I am at this stage purposely keeping the terms very general. Concepts like activation energy do not invalidate the principle of maximal entropy production, but gives structure to it.
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Jurie
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posted 04. March 2004 16:59
Rex Kerr wrote: quote:
But the spindle is there, so you have just appealed to an inaccessible pathway. How is this different than saying, "If there was a hole (or lit match) in the balloon, entropy would increase"? The point is, there is not a hole in the balloon.
I only gave a naturally possible scenario where the proton energy would be dissipated in the fastest way; this could be the case where ATP synthase is damaged, as in mitochondria in aged organisms or people with chronic fatigue syndrome.
Edit: The point about all this is to show how ATP synthase is not a pathway to maximise entropy production, but rather the contrary - it is not wasteful with energy, but rather an efficient energy conversion pathway. I am proposing that this sort of process is unique to life, hence its use in the definition.
[ 04. March 2004, 17:13: Message edited by: Jurie ]
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Jurie
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posted 04. March 2004 22:38
Here is a refined definition for life, based on the previous discussion. The basic thrust of the definition remains the same, but the terms are more rigorous. The definition is rooted in the Second Law of Thermodynamics:
"Life is defined as an energy expending process that increases order or maintains a state of high order locally, in an efficient and sustainable manner."
Definitions:
energy expending:
* requiring free energy to do it;
process:
* a series of actions, that belong together in the sense that all the actions are required to complete the process;
* the process is executed by means that are intrinsic to it;
* a process is not necessarily limited to one individual organism, but can extend to include a number of organisms, such as a bee colony where many individual bees are necessary to complete the process in a sustainable manner;
increases order or maintains a state of high order:
* the process and its intrinsic means actively move towards, or remain in, a state of high order;
* the local order includes any elements included into the process from the environment;
* the process includes actions to actively maintain the high state of order;
* the process increases order or maintains a state of high order, as a major goal;
* non-living processes can decrease entropy locally, but only as a mechanism for the opposite goal of increasing the rate of entropy production;
* an example is a tree growing from a seed, where local order is increased by assembling originally dispersed water and CO2 from the environment into ordered structures;
locally:
* the process operates in a limited scope while at the same time increasing the entropy in a wider scope, such that the global entropy increases;
efficient:
* the process converts and utilises energy in a way that results in high yield and little waste;
* the process has the result that wider entropy is not increased at a maximum rate;
* non-living processes can increase local order, but only as a mechanism for increasing the rate of entropy production;
* living processes are efficient while non-living processes waste energy as fast as possible;
sustainable manner:
* the ability to maintain the process for as long as the means to do so is present;
* it would include the means to effect self-repair and reproduction from the environment in order to ensure sustainability;
* process reproduction is an ultimate way to escape the effects of the Second Law of Thermodynamics almost indefinitely.
Living processes increase entropy at well below the maximum possible rate, while non-living processes increase entropy at the maximum possible rate. Why this is so, can be elucidated from the major "goal" of living processes versus that of non-living processes: Living processes strive to resist the entropy-increasing trend of the Second Law of Thermodynamics; it does so by utilising energy as efficiently as possible. Non-living processes can't resist the trend, so simply operate according to the principle of maximising entropy production. Living processes strive to conserve energy as much as possible, as long as possible. Non-living processes waste energy as much as possible, as fast as possible. These two opposite "goals" can explain the maintenance of high order in living processes as well as the spontaneous ordering of non-living processes.
It is therefore invalid to use examples from Life to demonstrate principles in the ordering of complex dynamic systems (see for example Francis Heylighen, "The Science of Self-Organization and Adaptability"), since the origin of the order in the respective cases differ. The two cases may exhibit effects that appear superficially similar, but the underlying reasons differ diametrically.
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RBH
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Member # 380
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posted 04. March 2004 23:34
Jurie wrote quote:
Living processes increase entropy at well below the maximum possible rate, while non-living processes increase entropy at the maximum possible rate. Why this is so, can be elucidated from the major "goal" of living processes versus that of non-living processes: Living processes strive to resist the entropy-increasing trend of the Second Law of Thermodynamics; it does so by utilising energy as efficiently as possible. Non-living processes can't resist the trend, so simply operate according to the principle of maximising entropy production. Living processes strive to conserve energy as much as possible, as long as possible. Non-living processes waste energy as much as possible, as fast as possible. These two opposite "goals" can explain the maintenance of high order in living processes as well as the spontaneous ordering of non-living processes.
The first sentence makes an assertion of a difference in the rate of entropy production in living and non-living systems, but fails to specify the boundaries within which that difference is to be considered. If one considers the complete "system" in calculating the entropy accounts, including in the measurement the energy sources and sinks in which systems are embedded, is there in fact a sharp distinction to be made in that rate between living and non-living systems, particularly if it is calculated as some sort of standardized measure that takes into account system volumes, densities, and the like?
Jurie further wrote quote:
It is therefore invalid to use examples from Life to demonstrate principles in the ordering of complex dynamic systems (see for example Francis Heylighen, "The Science of Self-Organization and Adaptability"), since the origin of the order in the respective cases differ. The two cases may exhibit effects that appear superficially similar, but the underlying reasons differ diametrically.
So much for complexity theory, hm? And so much for conjectures like Kauffman's about self-organizing chemical systems being relevant to the origin of the first biotic replicators. But the claim that "the origin of the order in the respective cases differs" has not in fact been established by the definitional exercise above. It seems to me that the "origins of order" (to borrow Kauffman's title) is an empirical question, not a definitional one.
RBH
[ 04. March 2004, 23:37: Message edited by: RBH ]
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Claire
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Member # 725
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posted 04. March 2004 23:48
Jurie,
Just quickly. These are excellent posts you have pu here and the thread in general is a breath of fresh air. What you say might mean a couple of new thoughts here form myself. One is about energy expenditure and entropy, or to put it simply what we think expenditure means to us (so far). You mention what the local entropy of a system is and give examples, then whole entropy etc and its purpose in a round about way. I was thinking then, that along the lines of that mysterious subject of human cognition, this cognitive brain system seems to take charge of how a specific type of thinking pattern creates a type of memory (maybe global goal oriented) and how when, according to some newish research (that i can't get my hands on at this moment)that suggests a theory about what happens when we create new thoughts in order to change a type of memory, or even delete the same memory, a specific part of the cognitive system actually requires more energy to break those very patterns! (that's creatvity for you) in order to make the mind actually forget not remember. However as you say roughly, it is about efficiency (life using maximum energy, no waistage) it might be a good idea to also consider, at the same time, that maybe then, not all efficient systems have direct status as it could be dependant on what the time goals are. Could it be that we have more than the two rates of energy space, time goals. For example, not just local entropy, then global general entropy but a third over all, not quite sure yet entopy space/goal? And what about this third state emerging from a specific set of systems even more complex than ordinary ATP proccesses (not in the human brain) compared to that of the human brain? Of course the brain cognitive systems are very physical and we have scientific reasons to support this, as physical as it is, however, as is the ATP structure and DNA etc.. what then could be missing that suggests we might have more reason to consider a third resultant global entropy state other than the two or the ones we allready have theories for? It could be mind itelf or thinking as a product. We could include local entropy effects, global entropy effects etc etc with these ideas. Anyway, this was supposed to be a short post! My second thought is, could another entropy state/goal be responsable for the fact that a "potential" changing factor of patterns of the mind itself, is a result of a specific type of new breed than effiency(in our eyes of course)? Imagine then if we could combine this third theory of reasoning (not just local, not just global, but an emergent reasone for entropy) that, on top of all that we know could be a be responsable for an explanation for the reasoning behind the re-creation of what a new thought pattern represents about say, even intelligent design as an example, that thinks about those very systems in a different manner about the re-construction of how we think about a different set of memory systems! I did say something very brief about effectiveness and efficiency on my site years ago, and what I suggested was a different whack at the second laws that revolved around efficiency and effectivness but most importantly recenty looking at the latter, why would I assume there could be another one in the first place.
Claire
[ 05. March 2004, 00:06: Message edited by: Claire ]
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Jurie
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posted 05. March 2004 07:34
RBH wrote:
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The first sentence makes an assertion of a difference in the rate of entropy production in living and non-living systems, but fails to specify the boundaries within which that difference is to be considered.
I'm not sure it is a case of boundaries; I think it might rather be a case of maximum entropy production or not. That is the logic behind my reasoning. But it is quite possible that there will be cases where the distinction is not clear. But in the case of energy conversion processes, I expect the difference should be very clear. I will see if I can come up with some efficiency numbers for ATP cycles.
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If one considers the complete "system" in calculating the entropy accounts, including in the measurement the energy sources and sinks in which systems are embedded, is there in fact a sharp distinction to be made in that rate between living and non-living systems, particularly if it is calculated as some sort of standardized measure that takes into account system volumes, densities, and the like?
It is of course possible to calculate the energy involved eg in the Krebs cycle, but there is no abiotic cycle that we can compare it with to see if there is a clear distinction, so this question might not be meaningful. What we can do, is calculate the efficiency of this cycle, by comparing the amount of free energy entering the cycle with the amount that is produced by it, and the ratio of these two yields the efficiency. A valid question might be, what constitutes a high and what a low efficiency? This question stands for the moment.
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So much for complexity theory, hm? And so much for conjectures like Kauffman's about self-organizing chemical systems being relevant to the origin of the first biotic replicators.
Not so fast, you seem to imply I reject complexity theory - far from it. But I do question the degree to which it governs biotic processes. In abiotic systems order arises from the maximisation of entropy production, and I argue that this is not the case for biotic systems. It follows that the assumption of whether the same principle governs biotic processes, may be questioned. I think it is questionable that cases from life is slipped in to serve as examples to explain complexity theory, when the validity of those examples is far from established. This can create the false impression that complexity theory holds true in arenas where it actually does not. Swenson's thesis is that the world is in the order production business; this rests entirely on the principle of maximal entropy production, a principle which is not necessarily applicable to life. That is my main point.
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But the claim that "the origin of the order in the respective cases differs" has not in fact been established by the definitional exercise above. It seems to me that the "origins of order" (to borrow Kauffman's title) is an empirical question, not a definitional one.
If it is assumed that the principle of maximal entropy production does not apply to a particular biotic process, it follows that order in that process cannot have its origin in the principle. Living processes strive to conserve energy as much as possible, as long as possible. Non-living processes waste energy as much as possible, as fast as possible. If those twin statements are true, then the assumption is valid. The truth of those statements will rely on empiricism, the rest follows logically.
Jurie
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