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Post by Progenitor A on Mar 10, 2011 21:23:52 GMT 1
"So, we have entropy acting on two levels. The atomic level and the level of chemical reactions that form the world around us, including all life on earth. The latter tends to be more sensitive to entropy as it is involved in complex lifeforms." I don't get that bit about "the latter", abacus. Looks to me as if 'life' is one of the exception to the rule of everything "running down". And what about stars and planets forming as I speak from cosmic dust clouds? That is change in the direction of greater not less organisation isn't it? Well, what you are looking at there is entropy at a much lower level, i.e. complex structures, as opposed to entropy at the atomic level (very high entropy). You see, to go back to the example of a pile of sand and the sandcastle, they are both made of sand which is, in turn, made of bits of matter which as you know is made of atoms but despite the sandcastle being extremely sensitive to disorder, it does not affect the atoms that compose it. You could destroy the sandcastle and its atoms would be exactly the same as those in the pile of sand. Stars are still forming, yes, but in doing so an infinitesimal amount of disorganization takes place, as with all other processes in the universe, so that the universe will still go on for a very long time but very gradually the matter in it is tending towards disorder. Eventually, in an unimaginable amount of time, there will be no more matter in the universe, just a sea of photons at absolute zero. I think that I understand the general trend of the universe becoming more disordered. Professor Cox also likened this disordering to the probability of a state existing. More disordered states have a higher probability of existing than than more ordered states. The Universe is getting more disordered However there are parts of the universe that are becoming more ordered in terms of the low probability of states existing. Thus a scyscraper in New York is more ordered than the piles of bricks and steel that existed before its its construction. The probability of the scyscraper is lower than the probability of the piles of bricks and steel. So on that measure, the entropy is reducing. So as the universe is gradually sinking into disorder, there are pockets within the universe that are doing the opposite In Professor Cox's terms we have the arrow of time travelling in the same direction as the iicreasing entropy of the universe, yet at the same time we have other arrows of time that are travelling in the opposite direction! But that appears to be nonsense So is this a possible solution? The universe is in a state of increasing entropy. But until entropy becomes complete, we can always extract work out of the system and that work can transform matter from one state to another. Thus during the gradual steady decline of the universe into disorder, pockets of order can exist (the skyscraper can be built). But the very fact that such manufactured order can exist means that we have used available energy from the universe, and once that energy is used it is gone (diffused). So the very creation of order in the universe is an indication of the progress of disorder! We cannot create order indefinitely because we are using energy up to create the order. So it seems that we cannot use local variations in order to measure entropy, but must integrate all orders and disorders and the disorders will always exceed the orders and hence we have the steady march of increasing entropy I wonder
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Post by speakertoanimals on Mar 10, 2011 21:32:58 GMT 1
Because the second law ONLY applies to a closed system, hence you have to take either the whole universe, or a closed part of it, compute the entropy, and that gives the thermodynamic arrow of time.
wittering on about energy just confuses things, because the simple fact is that the entropy of some sub-system can only decrease if it is not closed (energy flows in). It is pointless computing the entropy of non-closed bits, because then the entropy of that bit can either increase, decrease, or remain constant, and tells you little apart from you haven't chosen a closed susb-system.
Which is why all those nutty creationists get in such a lather thinking they have disproved evolution, whereas all they have done is shown that they've got no idea what entropy IS. Unfortunately some people on here seem to be following a similar path...........
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Post by abacus9900 on Mar 10, 2011 22:18:42 GMT 1
Yes, I think that is a very good way to put it. Even energy needs order to work, to be energy, but as you have pointed out, over time the order of energy gradually tends towards disorder so that in the end it dissipates completely and is no longer available to build stars, planets, human beings and so on.
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Post by abacus9900 on Mar 10, 2011 22:21:30 GMT 1
Because the second law ONLY applies to a closed system, hence you have to take either the whole universe, or a closed part of it, compute the entropy, and that gives the thermodynamic arrow of time. I'm sorry but you will have to make this statement clearer. Please define closed system, for a start.
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Post by speakertoanimals on Mar 10, 2011 22:38:42 GMT 1
Isn't it OBVIOUS?
How do you think you can talk about entropy if you don't know what closed means? Especially since ANY statement of the second law includes the term:
Closed equals isolated, basically -- nothing outside acts on it, and it doesn't act on anything outside. No matter, or heat, or anything is allowed to flow in or out, isolated from the rest of the universe.
So you aren't an isolated system, you take in air and food, and excrete stuff. Plants take in air, water, and sunlight. The earth isn't isolated, since it absorbs heat and light from the sun, and reflects some back to space. Plus we have gravitational interactions with the moon and the sun.
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Post by abacus9900 on Mar 10, 2011 23:06:11 GMT 1
Isn't it OBVIOUS? Closed equals isolated, basically -- nothing outside acts on it, and it doesn't act on anything outside. No matter, or heat, or anything is allowed to flow in or out, isolated from the rest of the universe. Examples? Professor Cox did not say there were any exceptions to entropy. In the end everything will end up as a sea of photons at absolute zero, so if you are trying to tell me there are things that won't, it is not credible.
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Post by buckleymanor1 on Mar 11, 2011 0:08:48 GMT 1
Isn't it OBVIOUS? Closed equals isolated, basically -- nothing outside acts on it, and it doesn't act on anything outside. No matter, or heat, or anything is allowed to flow in or out, isolated from the rest of the universe. Examples? Professor Cox did not say there were any exceptions to entropy. In the end everything will end up as a sea of photons at absolute zero, so if you are trying to tell me there are things that won't, it is not credible. There are no exceptions it's just that if you take what seems like an isolated system for instance the Earth and life on it. What you have is not isolated or closed but open to the rest of the universe. We borrow from the gravitational formation of the sun to exist in less dissorder but the general trend is towards dissorder as the sun dies out.
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Post by speakertoanimals on Mar 11, 2011 1:52:43 GMT 1
I DIDN'T say that! Just that if you look at the entropy of a non-isolated bit, the entropy of that may go down -- but that will be balanced by an increase elsewhere. And we aren't talking about all the way to the end of the universe here, we are just talking about shorter timescales, life for life evolving on earth.
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Post by Progenitor A on Mar 11, 2011 8:29:41 GMT 1
Yes, I think that is a very good way to put it. Even energy needs order to work, to be energy, but as you have pointed out, over time the order of energy gradually tends towards disorder so that in the end it dissipates completely and is no longer available to build stars, planets, human beings and so on. In fact, Abacus, the original definitions of the 2nd Law of Thermodynamics do not mention 'order' or 'entropy' Here are two original statements of the Law from Clausius and Kelvin ClausiusNo process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature.Kelvin statementNo process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work.It is importnat (I think) to realise that the laws of thermodynamics (heat, or energy transfer) were forged from the industrial revolution where engineers were concerned to get the most work out of their Manchester heat engines. It was a practical endeavour and horny -handed Lancastrians such as James Joule would not have concerned themselves with airy-fairy notions of universal entropy - they were concerned to make their bloody machines work better - efficiency, efficiency! Thermodynamics is about the transfer of heat energyWe should bear that in mind at all timesPersonally I think that Professor Cox, has, in this case, truly coxed things up I do not mean that he is wrong in what he said - I would not presume to call a distinguished physicist wrong, but his approach over one hour to this topic of heat transfer has led to great confusion amongst intelligent people that I respect - people such as you and Marchesa and Carnyx [and myself] (although Carnyx, to his everlasting credit did pour scorn upon Cox's presentation - a scorn I thought a little harsh at first, but in view of the confusion that Cox has created amonst intelligent people, I now consider that Carnyx's scorn was almost entirely justified). Those inteligent people have quite righty pointed out inconsistencies, illogicalities in Cox's interpretation and we are now, through discussion coming to terms with those inconsitencies I believe that the confusion that Cox created was unnecessary and that there are alternative ways of explaining entropy that do not cause people who have a penchant for enquiry people to scratch their heads in despair I believe that explanation lays in sticking rigorously to the terms in which the 2nd law was couched by Clausius and Kelvin the transfer of heat energy and ignore the Guardin-coffee-table tweeness of building sandcastles in the air that Cox so delighted in! Perhaps we should start a new thread that addresses the universe as a closed -system heat engine (a heat engine is a device that does work using the energy of heat -of course the form of that energy can be changed into other forms such as light, electricity, nuclear energy)and look a the entropy in terms of the distribution and dispersion of that total heat energy within the closed system.(For the closed system, imagine that the universe is enclosed inside a perfectly insulating sphere through which no heat can enter or be lost. Inside that sphere we have an enormous source of heat energy [that was originally the BB] and then we can examine what is happening to that heat energy over time). We will find that with that heat energy we can do wonderful things, but, having done them, we have 'used up' our original energy so that it can never be re-used, and that in essence is the entropy of our heat-engine system Fancy starting a new discussion on these terms?
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Post by Progenitor A on Mar 11, 2011 8:47:30 GMT 1
The most incisive posting on this topicI half-watched this prog last night, with its typical piccies of galaxies and portentious swirly music meant to evoke wonder, but the overall tone was depressing. And I had to laugh at the TellyDon presenter sitting by a calving glacier, explaining that the water molecules could somehow jump up out of the sea and organise themselves into lumps of ice ready to fall off again .. but that it was improbable. But, that is PRECISELY what the water molecules had done, and were going to carry on doing it! How does he think they got there in the first place? And what is stopping them repeating the process? AGW? Then, his sandcastle analogy found me getting a bit annoyed. That 'Nature' could actually arrange sand-grains into a castle shape, was being demonstrated in front of our very eyes! Sorry, but I found the thing too metaphysical by far. The concept of entropy is a scientific convenience, and to elevate it into a metaphor is a matter for poets, and not scientists. Cox in this programme came across as neither. But what on earth was this programme about? Dramadoc? Infotainment? Travelogue? Science edutainment? We had seen it all before, and done better. For example, the blue dot thing was a straight crib of Sagan's programme, and it was a bit cheesy even then; because one of Apollo astronauts had first coined it. A waste of money. Derivative stuff. And Cox has an unfortunate cast of face which gives him an irritating half-grin, which the tellyfolk pfresumably think is 'photogenic' .. or god forbid ..'sexy'. Verdict on the programme? 0/10. Nothing new. It would have been more entertaining to show the programme's project acccounts. Anyway, that 'arrow of time' metaphor is a necessary bit of blab to cover up the irritating fact that the 't' of Newton's and Maxwell's formulae can go negative but the sums still work. Well done Cranyx, I now believe that you are right and Cox coxed up!
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Post by abacus9900 on Mar 11, 2011 10:18:47 GMT 1
Examples? Professor Cox did not say there were any exceptions to entropy. In the end everything will end up as a sea of photons at absolute zero, so if you are trying to tell me there are things that won't, it is not credible. There are no exceptions it's just that if you take what seems like an isolated system for instance the Earth and life on it. What you have is not isolated or closed but open to the rest of the universe. We borrow from the gravitational formation of the sun to exist in less dissorder but the general trend is towards dissorder as the sun dies out. Well, indeed.
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Post by abacus9900 on Mar 11, 2011 10:20:17 GMT 1
naymissus, well if the good professor was wrong it should not have been put out on tv and I will stand corrected.
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Post by abacus9900 on Mar 11, 2011 10:26:52 GMT 1
We could but I think we would be in danger of making assumptions about the universe based on our current knowledge, which might be a bit risky as we haven't yet formulated a really good model of the quantum side of things, like quantum gravity, etc. Even STA does not know what is beyond or underlies our spacetime universe. Is string theory correct, for example? We don't yet know.
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Post by abacus9900 on Mar 11, 2011 10:40:19 GMT 1
I don't think you can expect an academic treatment of thermodynamics in a one hour popular science programme made for general viewing. Obviously you could go into the detailed mathematics and finer implications of the 2nd. law but Cox was just giving a basic overview of it and at least it allows ordinary people like me and others to have a basic framework with which to think about it. This is the purpose of such programmes, I mean just look at the discussion we are having here about it! Best to look upon it as a starting point, for which I feel eternally grateful for. You see, a lot of people might look up this subject and be put off by all the maths and jargon but in a tv presentation it is more likely to whet the appetite of ordinary people who don't have the IQ of Einstein or, indeed, STA! (Do I hear the word 'bollocks' ringing somewhere in the ether?)
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Post by Progenitor A on Mar 11, 2011 10:40:24 GMT 1
naymissus, well if the good professor was wrong it should not have been put out on tv and I will stand corrected. But I did not say he was wrong - simply thatentropy was badly presented
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