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An opportunity for the audience to have their say on In Our Time. |
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THE SECOND LAW OF THERMODYNAMICS
Rene VonCarte - 2nd Law & negative energy
Great programme. Good on Melvyn Bragg for chasing after such interesting ideas to talk about. Reading the comments, I'd like to say that this negative energy thing should not really be surprising. In classical mechanics, negative gravitational potentials simply drop out the equations. In outline, given Newton's law of gravity, force (of attraction) = -GMm/r^2, the gravitational potential works out as -GMm/r + some constant. (This follows from the definition of the potential, V, namely -dV/dr = force.) Since it doesn't matter what the constant is, it may as well be chosen as zero. In which case the potential is always negative (-GMm/r), or tops out at zero at infinite distances, as John Gribbin explained on the programme. The minus sign in the first equation is necessary to make the force attractive, otherwise it would be repulsive. Also, it's only the change in potential that's interesting for dynamics, and that's why it doesn't matter where you set the origin for energy levels. In short, the idea of negative energy arises fairly naturally in classical physics, so it should be no wonder if it were found to have a more solid basis in modern physics, if in fact it does.
Alan Jenkins
2nd law of Thermodynamice. Brilliant. I remember 'doing' it as a student in the sixties and thought that I had a grasp but that was only until the exams were over!! It was so eloquently explained. This is a fine example of 'dumbing up' PS can we please have access to previous subjects?
sean grainger - second law of thermo...
I thought this was a tour de force. I've played it three times but confess I'm still struggling with the gravity/negative energy bit. Perhaps you could revisit that sometime. Cheers Sean
Ali McNab - In Praise of Podcasts
Fantastic idea making programmes available for download. Please, please make your archive available on the same service. Yours is the only programme around that makes such complex subjects accessable to dunderheads like myself.
Roland Barker - Entropy
Re the newsletter, the sentence ' "All - change - is the consequence - of the purposeless - collapse - of energy - and matter - into disorder." ' brought to mind the similarly powerful sentence ' plus ca change, plus est la meme chose'.
Dennis Benson
The 1st and 2nd law stated Biblically is as follows "And, Thou, Lord, in the beginning hast laid the foundation of the earth; and the heavens are the works of thine hands: 11 They shall perish; but thou remainest; and they all shall wax old as doth a garment; 12 And as a vesture shalt thou fold them up, and they shall be changed: but thou art the same, and thy years shall not fail. (Heb 1v 10-12)
Canon Borer - 2nd Law
Thank God for Melvyn Bragg. Lovely series. It would be wonderful if all previous programmes in it were to be made available in MP3 format. I would have a wodge of them on my PDA as a vade mecum.
Rebekah - second law of thermodynamics
I hate to be flippant about such a fascinating subject - but my two children seem to disprove the idea. They are both hot little bundles of energy, which will hopefully become more diffuse over time, but I suggest that they will become more ordered and less chaotic. Tell me I'm right!
David N. Brown - The Second Law of Thermodynamics
Another excellent programme. Melvyn Bragg did a fine job questioning the physicists on the Second Law. He detected what looks suspiciously like slipperiness in the way the Law is applied. This was in response to the obvious point that order and complexity have actually increased on earth over the last 2 billion years or so thanks to the evolution of life. That means we've broken the Second Law? No, say the physicists. We've forgotten the sun. Whilst the biosphere was climbing into order and complexity and lower entropy, the sun was pouring out energy and gaining in entropy. It's solar energy which has powered life on earth. Our fossil fuels are a legacy of ancient life. Even Michelangelo's marble started off as an organic calcareous sediment. Look at the total system, they say, and you'll find that entropy is increasing overall. The Second Law triumphs. The problem I think Melvyn picked up is that this kind of 'explanation' is far too elastic - certainly on the cosmic scale, though accepting that it's fine for smaller things like steam engines. Whenever we find an apparent exception to the Second Law the physicist can always reply: "Ah, but you must look at the wider picture" ... And so we go on widening the picture, inevitably, because we can't shut out the rest of the universe. At the very least there will always be gravity, perhaps other forces too (lambda repulsion, quantum vacuum?) impinging on our 'picture'. This puts our contributors' belief that the Second Law is pretty well foolproof in a different light. The Second Law won't be falsified precisely because we won't let it be falsified! To put it more philosophically, the Law now looks like an a priori assumption or principle for making sense of the physical world, not a theory that can be falsified by empirical evidence. In short, a puzzling concept but a great discussion. PS. There's a useful account of entropy and the Second Law in Roger Penrose's The Emperor's New Mind, (OUP, Vintage edition, 1989) especially Chapter 7,
Daemon Maxwell - 2nd Law Of Thermodynamics
" '[A]ll change is the consequence of the purposeless collapse of energy and matter into disorder'. It's denser than most lines of poetry and carries more meaning than all but very rare lines of poetry." - Melvyn Bragg, newsletter 20/12/2004. Well said, Melvyn. Only one quibble: no poem can hold a candle to physics. I see no one here has yet mentioned the Zeroth Law of Thermodynamics. My question is: Should there a Minus-oneth['wunth'] Law? To answer this myself: Yes, there should. Here's a candidate: Despite all evidence of the universality of the following Laws, there will always be persons willing to gainsay them for nutty reasons.
TED
O! MELVYN! Temperature of your tea falls whether or not you drink it!!
Chris Peters - Entropy
John Gribbin referred to the death of the universe after the big bang and its rebirth when stars where created stars and gravity became the driving force. A question that Melvyn Bragg could have asked was what is the driving force for organic life forms? - i.e. why should life happen at all as there is no obvious benefit to the universe and its formation and greater order goes against fundamentals of entropy.
Keith_R Entropy
An excellent discussion of the second law although I did not understand the concept that the total energy of the universe was zero. It would have been interesting to have explored this in a little more detail. The localised decrease of Entropy caused by energy transfer was well explained and the fact that after the big bang and the formation of the fundamental particles we had essentially a hydrogen filled universe. The gravitational force and random variance caused the hydrogen to coalesce and as the structures became more massive they became stars, their gravitational compression generating enough heat to start the fusion process and give off radiant energy. The analogy of the falling weight causing a mechanical clock to work is an excellent one as it demonstrates how energy can be used to do useful work and cause a local decrease in entropy. The falling weight represents a mass falling through a gravitational field from a point of higher to lower potential energy. In the sun hydrogen nuclei.....protons, fuse to form helium. They fall through the strong nuclear or hadronic force field and become more tightly bound, in so doing their mass is reduced and the resulting energy released in accordance with Einsteins mass energy equivalence equation E=mc2. It is the suns radiant energy that causes us to have the entropy reversal......the localised ordered state that allows us to exist. Currently we are burning hydrocarbons formed over millions of years as a result of plants absorbing the energy of the sun and converting it into a more ordered higher energy state. Every time we burn these hydrocarbons the electrons in the shells of the atoms fall into lower energy states, the difference in energy being liberated. There is a loss in mass here too as E=mc2 is a universal equation.....However the loss in mass is so small as to be immeasurable although it can be quite easily calculated. The energy level change in a hydrogen fusion to cause an increase in nuclear binding energy is millions of times the energy change in the electromagnetic binding energy of the electrons in a typical hydrocarbon chemical reaction. We can all only hope that this power is harnessed for our own energy requirements if we are to go on increasing the entropy of the Universe at our current rate!
M.A.Cherian | The Second Law of Thermodynamics
The zeroth, first and second laws of [equilibrium, not steady-state] thermodynamics make temperature, internal energy and entropy functions of state of the thermodynamic fluid. The concept of entropy and the identification of the unidirection of time with increase in entropy of a system are only as profound as the heuristic concepts of thermodynamic equilibrium, reversibility, isolated, open systems, the concept of time itself and the preconceived mis-deduction from the time-invariant (-symmetric) Boltzmann probability distribution that entropy can only increases with time. All processes in nature are irreversible, Clausius. In any spontaneous or irreversible process the entropy of the system increases. Entropy is no Ahriman bringing disorder into the world. It is not even an entity, but a function of coordinates, the heat taken in in calories per degree of temperature, for each assumed local equilibrium state of the system. The energy of the universe is constant, its entropy tends to a maximum. A system in which there is no interflow of energy with its surroundings tends to the most probable arrangement of its constituent parts, viz. the random state, i.e. the entropy of an ISOLATED system never decreases, reaches a maximum at the state of equilibrium. ."In case the universe is regarded as an 'isolated system', it can never return again to the state in which it once was, because then also the entropy which is a function of the co-ordinates would again assume the old value, while it must always increase", Poincaré. If the whole universe is considered an isolated system, what is it isolated from and where are the isolator and isolated located? Its part(s) are considered isolated only with poetic licence. The only coherent practical isolated system is the adiabatic, in which work is done at the expense of internal energy. Fluid in a Dewar flask is usually taken as the nearest to an example of the adiabatic system. If the system is open to outside influences, entropy decreases. The concept of the thermodynamic system can be conveniently imprecise when based on the tacit impracticable assumption that the system refers to the thermodynamic fluid itself excluding containers, or when the closed system is imagined as a room with closed doors and windows, as many people find out during winter. The closed system, which is said to transfer in or out only energy, not mass, is also conceptual. A lot of science is dedicated to the proposition that mass and energy are synonymous. Where the does the energy that the closed system of the cyclic processes of a steam engine transfers comes from? Condensation occurs in enclosed spaces. It was one of Joule's experimental findings that, "no change in temperature occurs when air is allowed to expand in such a manner as not to develop mechanical power". Poincaré's Recurrence Theorem and Brownian motion are exceptions to the scope of the second law of thermodynamics: entropy fluctuates.
alan warburton
wonderful show this week on thermodynamics. really set my mind thinking. great idea with MP3s too. keep it up. great to have such a show exploring complex and interesting ideas in neat and accesible mannar. top marks to Lord Bragg for the interruptions and questions too.
kate - 2nd law of thermodynamics
Brilliant!
Peter Durose - Second Law of Thermodynamics
I have listened to this discussion four times, each time gaining more understanding of what the contributors were attempting to describe, and they did a superb job, as each one added to the total picture. Melvyn, true to form, supplied the "intelligent glue" to connect it all together. In my opinion this is one of the best discussions I have heard so far, and I have listened to many of these over the past months, including items from the Archives. Thanks, each one of you, for providing me with such rich food for thought, there is so much more still to be discovered, of course. As a young electrical engineering student in the 1950's, I learned about the First and Second laws of Thermodynamics, but never dreamed that they describe such fundamental universal "truths". I read with dismay some of the dismissive comments from fellow listeners, because they have misquoted the panel and failed to really listen to what was actually said. Thanks for this, I am a little wiser and more knowledgeable now, I love the MP3, and I LOVE the series.
Podcast
Thank you for pioneering podcasting. It does work very easily. I have now used it twice. I am surprised how few UK sites there are on the US website. Are thre any other listen again programmes to be included? Would be fantastic to get some more intelligent stuff available. I am living in Northern Territory Australia and this is what keeps me sane. You are providing a real service. Thank you. Andrew Stainer-Smith stainersmith@internode.on.net
David Price : Entropy
A most illuminating programme! But perhaps the most interesting aspect that was left somewhat unexplored. Scientific research says that the universe started somewhat chaotically in a Big Bang. Early pictures of the universe indicate few organised patterns of this elementary matter. The universe ends with maximum entropy or lack of organisation. Yet we today, at our stage of intelligence and observation, recognise massive organisation around us. It is not only that we have invented computers and databases but our very existence is made of a complex of 10 trillion cells. Each cell is hugely compex -- more than a city in terms of organisation. How does entropy move from a chaotic energy ball (high in energy, low in organisation) to this level of organisation? It can't all, as was suggested, be drawn out of inert Big Bang chaos by the pull of gravity. Gravity may pull things together but organise the complexity of life forms? No! Newton's apple was bruised by gravity. It wasn't raised to a new qualitative level of complex organisation.
Stephen Daly - Thermodynamics.
Dear Melvyn, Thank you for your interesting discussion on thermodynamics. By the way there is also a Zeroth Law and a Third Law of Thermodynamics. Years ago I studied the subject separately in Physics, Chemistry and Engineering classes. Each seemed to have its own slant on the subject. Woe betide the person who answered an examination question using the information provided by another discipline! For a start they all had different definitions of the laws. I had one particular query that no one seemed able to answer including various research scientists and a Fellow of the Royal Society whom I once quizzed. Back in 1957, "New Scientist" number 3 had a news item on negative absolute temperatures. Now one definition of Entropy (S) relates it to the quantity of heat absorbed (Q) and the absolute temperature (T). Entropy is also a measure of the disorder in a body. Again apparently 2 different definitions - I never found a description showing how both sets of equations are equivalent. Anyway by cooling certain crystals to just above absolute zero researchers found that there was still some disorder in the crystal lattice. By applying an electromagnetic field this disorder was reduced. From the definitions of Entropy this was interpreted as creating a negative absolute temperature. At around the same time an American magazine "Atoms for Peace" ran an article on the same phenomena and speculated that it might be possible to achieve nuclear fission by using these techniques to super cool certain substances. From my understanding negative absolute or Kelvin temperatures seem to contradict the second law. The recent ideas about a dark energy that is pushing the galaxies away from each other at an ever increasing rate also seems to contradict the first law. Perhaps one of your experts could kindly suggest a book that could resolve my difficulties? By the way I passed all my exams in the subject by the simple expedient of feeding back to the various tutors their own individual ideas as expressed in their lectures. Thank you. Steve Daly.
Philip 2nd law of thermodynamics
Anyone have any idea how I can introduce these concepts to a child ( including me in this) ( 9 and 12 !) I'm afraid I lost it when we went to gravity as negative energy and while I was puzzling I missed the speculation about whether the universe was orderly or not before the big bang. Great program and certainly has us going. I'd like to follow it up a bit more. downloading for another listen I'll take it slowly. br Phil.
James Baring - 2nd Law of Thermodaynamics
The very useful contributions to this debate so far demonstrate how confused, with the possible exception of John Gribbin, were the contributors to this programme. Paradoxically the most trenchant comment is from Mark Terrell, who takes Gribben to task on the meaning of the word entropy. Terrel highlights one of the problems that make this subject so difficult. Another example is the simple picture on the website with two coffee mugs, hot and cold, with the arrow of increasing entropy pointing from hot to cold. We then had Monica Grady giving the example of highly ordered crystals being heated first to liquid, then to gas, by the application of energy, and we were told that this represented a progression from order to disorder, an increase in entropy. It is this sort of things that makes young students abandon science as a subject to safeguard their sanity. Paradox is fine, nonsense is damaging. The fact is any order/disorder state is derivative, not fundamental or dependent on a single law that exists in isolation. It is unfortunate that an apparent division of perceptual talent has so separated scientific pioneers, teachers and students that few of them have been (still are?) capable of understanding the combined effects of gravity and entropy. Orthodox studies are years behind where they should be. It is not yet understood, let alone taught, that what we call 'gravity' is itself derivative of what we now call Dark Energy. It is within the localised gravitation fields where the resultant effect is to consolidate that order arises because choice, under varying degrees of proximity and pressure, is forced on the elements of the material universe that were themselves created by previous gravitational and thermodynamic cycles. The silliest moment in your programme was when Monica Grady justified her position by claiming that there was no life on any other planets in the universe, and that there was no tendency in this direction. The worst judgment on the meaning of the data was that of Peter Atkins. But well done, again, Melvyn, for making them talk. That's all we need...
Rita Kingham 2nd Law of Thermodynamics
Fascinating programme, but I would like to have heard more about "negative entropy" and information content. According to an old textbook of mine, Information is said to be like negative entropy, since it creates order out of chaos. I think it would be useful to have a further programme discussing this very difficult subject.
2nd law of thermodynamics - Mr Celal Berker
Dear Mr. Bragg, Congratulations on another excellent programme featuring the physical sciences !! Towards the end, Professor Gribbin implied that sunlight was sufficient to power the engine of naturalistic evolution. Because entropy is always increasing no system can move to a level of greater or increased complexity which is what is required by Darwinism. While the energy from the sun DOES feed the food chain, as it were, here on the earth it CANNOT build, create or establish the food chain in the first place. It is a physical impossibility. Only God can do that.
Mark Littleover, Thermodynamics
To Mark Credland: The 'disorder' that is meant in a thermodynamic context is simply that molecules having relatively high energy tend to lose their energy to others having less energy. It isn't clear that the informal disorder of genetic mutation is the same kind of thing. Even in the absence of mutation, a cell functions as a thermodynamic machine, contributing its bit to the overall increase of entropy.
Harry Armitage - 2nd Law of Thermodynamics
When I was young I almost became a physicist, and though my career has not been in science or technology as such, I have never lost a certain fascination with physics and related topics. I think that was because my Physics teacher was a human being first and a physicist second, able to expound really complex or counter-intuitive ideas in such a way that anyone listening attentively was certain to come away wiser and eager to learn more. So it was with Melvyn's programme this week. Many congratulations to all the contributors (and to Melvyn himself) for being like Ken Lyon (who taught at Bristol Grammar school in the nineteen fifties); the very best among a very high-quality group of spreaders of wisdom. Somehow I suspect that Melvyn, like me, secretly believes that the resultant decrease in entropy (i.e the increase of wisdom among his group of listeners) will not all end up dissipated and nullified by the ultimate spread of chaos in the universe!
Marcus Small 2nd Law of Thermodynamics
Is entropy the physical equivalent of alienation? Will the the physical parts of the universe end up alienated, out of relationship with one another? Do we see similar things in th moral universe? Are we created for relationship, yet tend towards the breaking up of these relationships?
Simon Dunkley 2nd Law of Thermodynamics
Surely the paradox that Melvyn pointed out can be explained by observing that the 'cold sink' in the system is actually the depths of space. The flow of energy on Earth is from the sun (during the day) and subsequent loss of that energy to outer space over night. This suggests that for life on Earth to have developed, it has to be spinning on its axis. The Earth represents a local reversal of entropy: an entropy 'sink' because of our fortunate position in space. This is reasonable, as we are only a small part of the solar system, intercepting 1 billionth of the sun's energy. The worrying thing is, that as mankind burns fossil fuels and works against this local entropy 'sink' we accelerate the planet towards the same fate as the rest of the universe. Soberingly, I suspect that sometime during the 20th century, we turned the Earth into a net 'source' of entropy. I wonder how long we can continue to do so...
Mark Credland: Second Law of Thermodynamics
I have some questions... Is it true to say that natural selection is made possible because of the small changes or errors that occur in DNA when living things make copies of themselves? If so then would it be true to say that these small changes, or errors, occur because of entropy, the tendency for things to move from a state of order to a state of disorder? I wish I had the opportunity to ask a panel of experts these questions.
Lucrezia Bibbia - 2nd Law of Thermodynamics
"The human brain is the pinnacle of complexity" Melvin,oh dear, oh dear! No surprise then the more abstract concepts seem to escape you completely. ;-)
Mark Terrell - In our time - entropy
I came in at the end but 1. Mr Gribbin is exactly wrong when he says increasing entropy is increasing disorder. This is only true mathematically. In ordinary English the contrary is true. Entropy is increasing unavailable energy ie. Increasing Order! (Ordinary English) 2.Because our interpretation of the world around is based on Probability (to avoid the impasse of Solipsism) so our picture of the world is more or less accurate only at our scale. Beyond the limits set by our scale these limits are defined by physics as the point at which a different system has to be employed. Such are, the Big Bang, Planck's Constant & the various physical constants There are many examples from the value of sq.rt.2,Pi, 'e', &c.
RK Cook Thermodynamics
So now we know what Melvyn Bragg's In Our Time is. In an increasingly disordered world, it is a local abatement of chaos. And somewhere in it is an engine or mind, some kind of genius, who reduces three- quarters of an hour in the morning to half an hour in the evening without loss of meaning or coherence. Brilliant.
Mark Littleover, Thermodynamics
The contributors stumbled when trying to explain the decrease of entropy implicit in life on Earth. As they said, the Sun is solely responsible via its energy input to us. However, the increase of entropy isn't vaguely connected with some other planet, as suggested. The Sun is radiating its energy into space, and when this radiation is absorbed by a relatively cold object (even the Earth), then the total entropy of the system (Sun + the rest of the universe) increases. An increase of entropy simply means that heat has moved from a hot place to a cool one.
Mike: Theromodynamics
Another interesting programme and it's much appreciated that I can listen later and repeat parts via the internet and downloads. I appreciate that its an art to balance 'hard' scientific facts and theories using presentable models, but I understand that Entropy is only about energy spreading out and not disorder in the usual english sense of more random patterns. It might be useful in programmes such as this to make these points. Also I am not sure that evolution does flow against the 2nd law, in the first place we (all life) do actually consume energy and are a quite efficient way of the universe breaking down stored energy. Secondly, although evolution does appear to build more complex structures over time, the cost is a need for even more energy that is quickly dissapated by the irritating trait of complex beings to cease. Finally, after an explosion of experimenting with designs evolution seems to be running down and reducing the overall complexity (reducing biodiversity). Even without bringing the rest of the galaxy into the equation it is obvious that life and humans in particular casue more spreading (waste) of stored energy and disorder that owt else in the milky way.
David Pollard, Entropy and Entelechy
One of the reasons that entropy is difficult to understand is that its partner, entelechy, doesn't (yet) have much of a place in science. Although entropy, disorder, increases continuously, apparent order also sometimes arises from the chaos. From ripples on a sandy beach as the tide goes out and mackerel skies to life and thought itself, it seems undeniable that order and meaning arise in the universe. It would be interesting to hear today's discussion extended to include entelechy - how meaning and knowledge fit in to the physical world.
Marc, 2nd Law of Thermodynamics
I would have liked a stronger focus on the correlation between the law and entropy, especially in regard of the view (as stated excellently by Erich Jantsch for example) of this property of the Universe being the force that drives creativity (in a physical/biological) sense, as well as in a cultural sense. But maybe this would require a broadcast about self-organisation? Re MP3: Offering the program as MP3 is so much more convenient. I record a lot of internet radio during the day and store it on my iPod to be listened to in the car or when walking the dogs. (Nice to hear about Higgs in the Cairngorms while walking in the Souther Uplands.) BTW. this has become my favorite radio program!
Steve Dale Sale Cheshire: 2nd Law
AAAAAAGGGGGGHHHH, You stopped just as it was getting even more interesting! How do your correspondants view death and how does death fit into the law? Death is strange, it seems to be the only thing that is 100% efficient(everything dies but no machine or system is 100% efficient). It may follow that death is a demonstration proving entropy. Are we just a stage in the order to chaos progression? Or do we live on in the "ether" but in a different form? How does the concept of God fit into this theory if at all? Will we all come back when the second (or 3dr,4th.5th et al big bag occours? Questions, questions, questions. Brilliant programme, the highlight of the week.
Una Monaghan
I am a third year Astrophysics student at Cambridge. I listened to the programme today because I got a text from my mammy which woke me up and said "radio four, quick!!" It covered exactly what I was doing last term. I'd just like to say it was very informative, and Melvyn, you're a legend for stopping them and asking the questions you did....I go through weeks and weeks at university with the same questions as you but I can't stop them every few minutes during a lecture! so I enjoyed listening to you do that. thanks for the help, and all the "but...." :)
Tags: 2nd Law of Thermodynamics
Currently we are deducing from known facts and I query the certainty that the universe will come to a stop. It seems to me that it is likely that there are many things that we yet do not know and have not discovered, and therefore certainty is inappropriate. Maybe the only certainty we have is that things change! I do not agree that there is an end when man becomes dust - that dust contains atoms, say of nitrogen, which can be absorbed by plants - then humans. I may have an atom in my body that was once in Machiavelli's! Even when the sun's cools to carbon, carbon atoms contain energy and this energy could at some point be tapped, perhaps by a small ripple in the universe such as those that started the big bang. We have limited organs of perception, and are always reliant ultimately on these, even with the help of very complex tools. Who knows what we may never be able to perceive?
Paul Kirkley: The 2nd Law of Thermodynamics
Thank you for a very clear explanation of the 2nd Law, and its importance to an understanding of how everything works. You explored the concept of waste heat - but not waste materials. That's a pity. It would have been an ideal opportunity to question European and UK Government waste managemetn policies, by explaining how recycling adds to global warming. Such policies (including "Sustainable Aviation" and "Sustainable Development" are fools' errands - like trying to invent Perpetual Motion Machines. It's a pity you didn't mention them either. The 2nd Law neatly explains why thay are impossible, as the Patent Office will confirm.
Richard Klemperer - 2nd law of thermodynamics
A fascinating program this morning. I was following everything and then one of the contributers said that that this universe started from the near death of the previous universe when the force of gravity "brought all the hydrogen together" and drove entropy into reverse using this 'negative energy'. Where then did all this hydrogen come from? - because another contributer had just explained all about how the universe dies when all of the hydrogen fuel which drives it as being the starting point of the process of increase in entropy is exhausted by conversion into heavier elements inside stars. How then do these heavier elements convert back into hydrogen in order to start the next universe? Perhaps the best comment was the person who said that nobody understood yet how gravity fits in with entropy.
P J Devlin - Entropy
Agree with other comments that Melvins question of "how to reconcile evolution and entropy" was not the simplistic misconception that it was brushed off as i.e. 'local effect breaching universal principle' but hinted at a substantial philosophical problem. If the increase in local complexity can always be explained by increasing chaos elsewhere (exporting entropy) then how can this process ever be subject to verification by observation since "out there" is by definition what is not being observed. This is a case in danger of breaching the falsifiability principle in which any proposition claiming to be scientific must predict future outcomes that can conceivably be subject to observational testing. Where this is not the case we have to ask if it is telling us anything about the universe or can be resolved into a tautology telling us nothing.
Ron Etherington - Entropy
As regards evolution I am surprised that no one on the discussion pointed out that the evolution in which we are involved is in fact a reduction in possibilities or potential. The more complex the given point the less directions remain available. I'm very glad that such programmes are being made - a real justification for public broadcasting which is prepared to stretch the listener's mind.
Amos Blur
Another Fantastic Programme. Entropy. Dispersal. Disorder. The Three Laws. Yet no mention of concentration channels?
Carl Evans - The Second Law of Thermodynamics
I have not heard 'In Our Time' before today, but I thoroughly enjoyed this morning's broadcast. I now have nothing but admiration for the consummate communicator Melvyn Bragg as he sought to bring order out of the chaos presented by his contributors. This was obviously not without input of considerable energy by our host as he dealt with explanations from John Gribbin, Peter Atkins and Monica Grady which only deviated from the contradictory when they wandered off into the nonsensical. This sorry band had meandered its way through conjecture on 'constantly expanding universe', 'multiverses', 'heat death' and 'dark energy' before declaring that the current ordered state of evolution would no doubt be balanced by an equal amount of disorder - 'elsewhere' in the Universe. I confess that I had long before given in to fits of giggles by the time Mr. Bragg succumbed to laughing out loud as the Professor of Chemistry declared death to be a satisfactory state of equilibrium. Keep up the good work Mr Bragg. Long may your subtle humour underline error and fuzzy thinking among so called 'scientists'.
The meaning of life'n'evryfing
Today's prog linking gravity, thermodynamics, natural selection and the rest was brilliant and mind blowing. More please. And another prog to go over it all point by point and to probe the next level of questioning: WHY are there laws of gravity, thermodynamics, eletcromagnetism et al. What was there before the Big Bang? Thanks. Colin Robinson.
R H Jenkins - Entropy
Melvyn Bragg was correct to query how evolution fitted into the idea of increasing disorder. The quick answer is that life is the unique process wherebye order is achieved contrary to disorder and hence entropy is negative. This distinguishes the crucial difference between the inanimate physical world and the animate living world.
Mark Nicholas, The 2nd Law of Thermodynamics
Melvyn Bragg rightly challenged the seeming contradiction of the 2nd Law of Thermodynamics and the theory of evolution. Though superbly conceived, almost without exception, evolution as a explanation of the origin of life is discussed not as a hypothesis but as a fact. It was refreshing to hear evolution itself exposed to scientific scrutiny. Biochemistry is continually revealling that the most elementary forms of life are far from simple as evolution must assume. Indeed the cell is as complex in structure as higher forms of life. From the perspective of biochemistry there is little evidence that our antecedents were less complex. Indeed, the 2nd Law of Thermodynamics would seem to encapsulate a theological question as all is destined to decay; that of the Fall. Many thanks for a stimulating discussion. Perhaps there is more to discuss in these matters at a future date.
Nick Hudson: second law of thermodynamics.
What a stunning program. I now have deal with the 1st "near death of the universe" and "gravity stores negative energy". This is what we need. Changeing our perceptions of how the universe works - and no pictures required! Thank you so much.
harry clarke/thermodynamics?
I've just listened to your program which attempted to explain the wonders of thermodynamics. This discussion reminded me of the debates Socrates had with the resident intellects in his time. Socrates visited his each of his esteemed collegues as an ingnorant individual searching for explanation of simple ideas which were considerede incontravertible. During these debates he exposed fundamental flaws in the arguments of the intellects. This program was a re-enactment of the last days of Socrates (in our time). Fantastic entertainment!
Thermodynamics
Well done Melvyn for querying the local question of the third law. It's taken physicists years to accept gravity doesn't follow the normal rules.
Dave Nicholson
I think this is the best radio programme " in our time".Fascinating. I would like one on Leanardo Da Vinci in the future or has there ben one and have I missed it
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