00:00:00.000 Welcome to Topcast, and it's episode 119 and the 8th, I believe, in my series on the Science
00:00:06.880 of Canon Card, the book by Chiara Marletto, all about Constructa Theory.
00:00:12.320 And today, it's a video because there's going to be diagrams, movies, and even real-life
00:00:17.880 experiments, such as going on in the background, which you may hear a little bit of a ticking,
00:00:21.520 the motion of a motor, an engine, a heat engine, specifically something called a sterling
00:00:29.320 These things, these objects, these devices, pieces of technology, have helped build the
00:00:34.480 advanced society around us, or the explanation for their operation comes down to the field
00:00:43.520 And that's what this chapter of Chiara Marletto's book is all about.
00:00:47.520 Now, let me grab a hold of this really interesting, but simple, yet subtle, piece of technology.
00:00:59.760 What it has are two surfaces, one at the bottom, one at the top, the one at the bottom can
00:01:05.200 be placed in contact with a heat source, and over there, that's nothing but a hot cup
00:01:12.200 And at the top, it's cooler, hot down here, cold up here.
00:01:16.560 And in between is a diaphragm, and the diaphragm is moved by gas beneath, expanding, because
00:01:23.000 it's heated, heated gas expands, increasing in volume, pushing the diaphragm up and doing
00:01:32.920 And this basic principle is the principle of all such heat engines.
00:01:37.840 A foundational part of, not only technology, physics itself, and why Chiara has devoted
00:01:43.480 an entire chapter of her book, in part, to this phenomenon.
00:01:49.000 So, even deeper reason why anyone will be interested in such a thing.
00:01:53.640 Put it back over there, and you can see that, although it's stopped now, because there's
00:01:57.440 no energy being supplied, we can put it back onto the hot water.
00:02:06.280 We need to give it a little push to get it started.
00:02:15.040 The thing is, we have high energy, of a type that we'll talk about throughout the course
00:02:19.600 of this episode, in the water, which is in the cup there.
00:02:23.920 That heats the gas, that's in the cylinder here.
00:02:27.120 The gas when heated expands, pushing the diaphragm up, it's connected to a piston, the piston
00:02:35.160 And that in theory could be used to do work of some kind.
00:02:38.760 And that is what work is, force over some distance.
00:02:41.600 And in theory, you could hook that thing up to a generator, a generator, a series of wires
00:02:47.000 moving in a magnetic field, which would generate electricity.
00:02:50.600 Again, one of the fundamental features of our modern civilization, all down to simple
00:02:58.760 But as we'll see, although simple, there's a whole bunch of really interesting subtleties
00:03:07.200 Let me grab a hold of it again, being very careful, because it's actually filled with
00:03:21.200 And essentially there are, we will come to three important parts of this in order to turn
00:03:28.120 the energy that's in the cup, into the energy of work, the capacity to move stuff around.
00:03:35.080 What that is, is somewhere that's hot, as well as somewhere that's cold, there needs to
00:03:41.280 be a temperature differential in order for there to be a transfer of energy by heat from
00:03:50.680 And by virtue of that temperature difference, we do get this movement of heat and the movement
00:03:56.360 That's the thing that's able to do the work, but why should it happen at all?
00:03:59.920 What's really going on in terms of the physics here?
00:04:03.000 Well, that's what we're going to talk about in part today.
00:04:10.560 I might remove the motor for the rest of the episode, otherwise I think it's making noise
00:04:16.320 Now today there won't be many, if any, readings from the book itself.
00:04:22.240 This is more like a prelude, and I've done this a few times.
00:04:25.120 I think that the topics are so interesting that are in the science of Canon card.
00:04:30.280 The topics are so interesting in and of themselves, that sometimes I like to step outside
00:04:34.760 of the book for a moment, just to discuss some of the physics absent the book.
00:04:39.560 Now the reason for this is because constructor theory, remember, is a new mode of explanation,
00:04:45.000 a new mode of explanation of those concepts of those things, such as as we're going to
00:04:50.600 be talking about today, thermodynamics, and as we've previously talked about, knowledge
00:04:56.240 So this constructor theoretic mode of explanation is a new way of looking at things, things
00:05:01.200 that we already know about, to try to come to a deeper understanding of things, to try
00:05:08.160 And therefore, constructor theory is touching on topics that have a history in science.
00:05:17.480 The very title of the chapter, work and hate, will scream out to anyone who's done physics
00:05:22.000 or chemistry, the topic of thermodynamics might move away my little setup here so that
00:05:27.760 I don't spill the water anymore than I already have.
00:05:33.160 It's one of those subjects at undergraduate level, where I'm like quantum theory, where
00:05:38.400 happily early on I was able to sort of uncover for myself, discover by reading some popular
00:05:45.160 science accounts, that the lecturers and tutors weren't giving me the story, because
00:05:50.600 I found the fabric of reality and I encountered David Deutsch through the internet.
00:05:55.480 So happily I understood that my confusion in quantum theory was warranted because I wasn't
00:06:05.960 But unlike quantum theory, thermodynamics was a field where I got through doing physics
00:06:11.920 and not until later when I was actually teaching the subject myself.
00:06:17.560 Did I realize that the way I had been taught the subject was itself deeply riddled with misconceptions.
00:06:24.600 I couldn't believe that even after studying physics, I didn't really know what a concept
00:06:31.400 I mean, if you'd asked me coming straight out of university, I'm sure I would have had
00:06:35.200 an answer, I would have said something and I would have been awarded marks on tests
00:06:40.320 and I would have been able to do calculations of things like specific heat capacity or
00:06:48.640 But that's just to say, of course, I was working instrumentally, plugging in numbers into
00:06:53.200 equations that were to predict the outcome of experiments without ever knowing what was
00:07:02.240 You know, some of these questions are things like a heater-provide heat energy at a rate
00:07:07.920 of the thousand watts to one liter of water, calculate how long it takes for the water
00:07:14.400 to change its temperature from 20 degrees Celsius to its boiling point at 100, something
00:07:21.760 But that whole way of asking the question, that whole way of putting the question, is
00:07:25.600 itself entirely misconceived, this idea of heat flowing or some such or thermal energy moving
00:07:35.640 It took me teaching this stuff and therefore being challenged myself to really think
00:07:40.480 about this, to really understand what was happening at the level of the particles.
00:07:44.880 What's flowing from one place to another when things are heated?
00:07:51.680 Is there some substance coming out of the kettle?
00:08:01.280 This energy flows out of the heating element and into the substance causing its temperature
00:08:09.400 I think I can explain it now, but I don't think I could have explained it then.
00:08:13.160 I always heard, for example, that heat flows from a hot body to a cold body, but never
00:08:21.200 What the heck is this thing heat that's flowing around?
00:08:28.400 And the person that taught me that was the great physical chemist, perhaps the most famous
00:08:32.840 leaving thermodynamicist of all, Peter Atkins, and it took me listening to his lectures,
00:08:39.240 watching him on YouTube, reading his books, especially his textbooks and his popular accounts
00:08:45.240 Let me quote my favorite quote of his on the topic of heat.
00:08:49.600 I mean, there's many, many other concepts in thermodynamics, but heat is possibly the most
00:08:54.240 misunderstood and subtle of all the concepts within thermodynamics.
00:08:59.200 And I find this particular distillation of wisdom on the topic of thermodynamics, the most
00:09:04.160 brilliant of all, it's from one of his popular books on thermodynamics that I'll mention
00:09:09.080 again later, but Atkins wrote quote, in thermodynamics, heat is not an entity or even a form
00:09:20.080 It is not a form of energy or a fluid of some kind or anything of any kind.
00:09:25.320 Heat is the transfer of energy by virtue of a temperature difference.
00:09:28.840 Heat is the name of a process, not the name of an entity.
00:09:33.360 So in grammatical terms, heat is more of a verb than what it is a noun, but of course
00:09:41.920 And so sometimes it's almost unavoidable in normal day to day conversation, in using
00:09:46.720 the word in its less precise meaning, even when you're talking to other physicists and
00:09:51.520 so on, because that's just what we've inherited from the long history of the use of the
00:09:56.800 word and the way in which thermodynamics began and our scientific understanding of this
00:10:01.040 began, of heat being some kind of substance or fluid, even though it's not because now we
00:10:07.720 Heat is the movement of energy, but what energy?
00:10:10.360 Well, it's kinetic energy in the mind and that kinetic energy can cause increased kinetic
00:10:15.280 energy of the particles of the cooler body by physical collisions with particles in the
00:10:22.680 So conduction of heat in solid metal, for example, happens because not this substance
00:10:30.880 There is no such substance, but rather at the hot end of a piece of metal, the particles
00:10:35.880 there are vibrating really fast and they are physically colliding with their neighbours and
00:10:40.520 that collision goes all the way along the solid piece of metal until you get this transfer
00:10:45.440 of energy, kinetic energy, the energy of motion, of vibration of these particles from the
00:10:52.640 That's what heat is fundamentally movement at the level of the particles.
00:10:58.240 It's not only that, but as a first approximation, that's a very good way to understand
00:11:03.880 It's not that there is this strange substance flowing from one place to another, rather,
00:11:10.880 And if they're vibrating in one place, they'll be colliding with their neighbours and
00:11:14.320 their neighbours will collide with their neighbours and so on, and that's how conduction
00:11:17.760 in, for example, solids like metals happens to work.
00:11:20.800 Now it's not always that the kinetic energy happens to increase.
00:11:24.600 If you heat something, it can be the case that the temperature will rise, but also maybe
00:11:29.880 the temperature won't rise, maybe just its state will change.
00:11:33.680 State changes happen at the one temperature, by the way.
00:11:36.080 So, for example, water typically at sea level under the standard conditions and so on.
00:11:42.600 That means that at that temperature, the liquid water is turning into gaseous vapour at
00:11:51.160 The liquid water is at 100 degrees Celsius, and the vapour is at 100 degrees Celsius as well.
00:11:56.600 And we're going to get back to exactly what this idea of temperature means as well.
00:12:01.080 That itself is another subtle concept that needs to be made precise by physics.
00:12:06.200 This is what physics tends to do, but people can tend to have this misconception.
00:12:10.920 You put water in a pot on a stove and you boil it, and one of the first misconceptions
00:12:15.760 that people have about that process is that although they understand that the water boils
00:12:20.720 at a particular boiling point at like 100 degrees Celsius, then if you continue to apply the
00:12:24.840 heat, maybe the temperature goes up and up and up.
00:12:27.400 You can ask people this question if they don't remember their high school science, let's
00:12:34.240 After all, you're adding more heat, you're heating the water, you're continuously heating
00:12:37.600 the water, shouldn't the water continue to get hot?
00:12:40.720 It stays at 100 degrees Celsius until it all boils away.
00:12:43.720 When I say 100 degrees Celsius, I mean, assuming all the usual conditions, if you lower
00:12:47.720 the air pressure, the temperature, the temperature at which the water boils happens to
00:12:52.440 Why are there these misconceptions well, it's because the teaching of thermodynamics around
00:12:56.120 the world still follows this misconception-safe pattern.
00:12:59.960 Heat is strongly implied to be a fluid of some kind, such and such contains more heat
00:13:06.680 Now, it's fine to say something is hotter than something else, but not to say it contains
00:13:15.480 Because again, heat is not a substance, it's not a thing.
00:13:18.520 Kinetic energy is a thing, how fast the particles are moving or vibrating.
00:13:23.280 Potential energy is a thing, how strong the bonds between particles happen to be, but heat
00:13:29.280 Heat is the name of a process, to heat something.
00:13:32.520 And having heated something, the temperature, the kinetic energy or the potential energy
00:13:36.400 stored in the bonds of the particles will have increased.
00:13:39.600 The real goal I'm reaching for in this podcast, and especially the next one is a more
00:13:44.560 precise statement of something called the second law of thermodynamics, in terms of deeper
00:13:51.440 underlying principles, or a deeper underlying theory.
00:13:55.080 So here's a bit of pedagogy first, a method of teaching or learning.
00:13:58.680 It's been interesting to me as I've come out of teaching and into doing well this kind
00:14:05.080 of thing among other things, that people will sometimes ask me when I am explaining some
00:14:09.760 aspect of cow popper, or David Deutsch's work, some deep and subtle part of either philosophy
00:14:15.760 or epistemology or science or physics, they desire, on occasion, a particularly precise
00:14:25.160 I notice David gets this when people ask him questions as well, it's often, you know,
00:14:29.440 if they have the opportunity to interview David or to discuss with him, they'll say,
00:14:33.480 well, can you define knowledge for me, can you define optimism, can you define this that
00:14:39.000 And David, I think, I can't speak for David, but like me, I guess, following in the
00:14:43.600 tradition of popper, I think, has an automatic kind of aversion to that kind of thing,
00:14:52.680 Now, I'll speak for myself here, there are a couple of reasons for that.
00:14:56.080 I worry about the term definition of being asked to define things precisely.
00:15:01.000 The first is, well, the idea of having a definition in people's minds, I think, is supposed
00:15:06.720 to capture something of the essence of the thing you are talking about, that you are defining.
00:15:12.400 It's as if you define the term and then you are held to the definition.
00:15:16.280 And people find holes in the definition, but all the while, that was never your intention
00:15:20.120 to say everything that could be said about the term.
00:15:23.560 So the problem with definitions to my mind is that they have this pretense in some people's
00:15:31.160 This is the perfect statement of what this term actually means.
00:15:37.440 And inconsistent with the broader worldview that we can always make progress and learn
00:15:43.280 And it's anti-philosophy as well as we understand the term.
00:15:45.800 Popper even wrote about not wanting to quibble over definitions.
00:15:49.640 He spoke about this and wrote about this in objective knowledge.
00:15:53.000 Now, putting all that aside, the other reason to object to providing precise definitions
00:15:59.080 of things is, well, I think people are enacting a kind of meme of a kind when they
00:16:05.520 ask the question, what's your definition of knowledge?
00:16:12.000 What they want, aside from trapping you in a debate over terms, perhaps, which is, again,
00:16:18.280 not real philosophy, is that they might genuinely want to learn, but they want to learn
00:16:25.640 It's like they're back at school and they want to write their list of words in a glossary.
00:16:30.560 And once they learn them off by heart with their definitions, they can top the test and say
00:16:35.840 they understand all those words, and therefore they understand this thing and what they're
00:16:41.000 talking about, because they've got the vocabulary and they know what these definitions
00:16:46.640 And I think that's just a wrong way of going about understanding reality and understanding
00:16:54.160 But it's the traditional conception that people have about how learning kind of words.
00:16:59.160 I know this is the way I was taught, and here write a glossary of terms, here write these
00:17:03.080 definitions of words, and it's still done today, teaches love, a good glossary at the back
00:17:09.080 Now, was this to say definitions are utterly pointless?
00:17:12.200 Well, no, of course not, but you have dictionaries for that kind of thing, the better
00:17:15.720 idea, especially when it comes to subtle and open-ended concepts to some extent, especially
00:17:21.240 in philosophy and science, is to approach the term from various different angles and try
00:17:27.160 to come to a more complete panoramic understanding of the term, realising the whole time.
00:17:33.320 There is no single definition for some of these things, but rather we have an explanation
00:17:38.120 of what this concept is, and we can likely improve it over time as well.
00:17:42.640 So, don't learn the definition, just try to understand what this thing is all about.
00:17:48.600 Why would I be saying that approach to learning is wrong?
00:17:50.880 Well, in this field, in thermodynamics, it's filled with this kind of subtlety.
00:17:56.800 And the use of very common words that everyone thinks they know, but in thermodynamics,
00:18:02.920 these words have a certain kind of precision, precision use, one might say, idiosyncratic use.
00:18:09.040 But sometimes that precise and idiosyncratic use can seem to make things more difficult
00:18:15.080 And so, for that reason, I'm going to be doing something else today, in this particularly
00:18:20.720 Rather than me just telling you, well, here's what energy is, for example, and here's
00:18:26.640 Here's the first law, and here's the second law listing things.
00:18:29.520 Here's the definition of, let's say, entropy, which is something we'll get to.
00:18:33.440 And then, presuming at the end, once you've understood all those words, you're going
00:18:39.720 We're going to talk about the words, talk about some of the definitions, but I want to take
00:18:43.760 a wide variety of approaches to these things from popular science and from the history
00:18:48.720 of science and from mainstream texts as well, and see if and where they converge.
00:18:55.000 And hopefully, this will help us create some sort of background knowledge.
00:18:59.160 So then we can understand what Kiara and David are accomplishing with the constructor
00:19:05.240 theoretic view when it comes in particular to the second law, which, as I say, is kind
00:19:12.600 I'm going to meander through this territory today to try to come to thermodynamics and
00:19:20.480 There are, as usually, counted four of those laws numbered, confusingly, 0, 1, 2, and 3.
00:19:27.560 So perhaps if you are largely unfamiliar with this stuff, that by the end of this episode,
00:19:32.800 you're in a good position to really get the punchline, so to speak, by the end of next
00:19:38.560 And perhaps if you didn't know much about thermodynamics before, and perhaps you have a casual
00:19:42.200 interest in it, you'll be more scientifically literate in it, let's say, from now on
00:19:48.040 I'm referring to a few old texts that I'm going to dust off.
00:19:51.680 And my own notes as well from having taught some of this stuff over many years, and I'm
00:19:56.920 going to therefore lean on some of the giants who write in this area of thermodynamics.
00:20:02.560 And first and foremost, among them, I've already mentioned the man who's the perhaps
00:20:06.000 one of the greatest minds on this topic, Professor Peter Atkins.
00:20:10.400 He wrote some of the seminal and foundational texts on the topic of thermodynamics and
00:20:15.080 physical chemistry, mainly for chemists and physicists and engineers and others who needed
00:20:22.360 He's the kind of the go-to guy when it comes to thermodynamics.
00:20:25.560 But more than that, he backed up all that heavy technical stuff with some really, really
00:20:30.080 good popular science books explaining the implications of these things, the sort of broader
00:20:35.640 deeper philosophical implications of some of this stuff.
00:20:38.280 He's got numerous lectures, by the way, online, and again, those online span the highly
00:20:44.040 technical through to the popular and philosophical.
00:20:47.320 So up front, I want to say that today, much of what I am saying comes straight from
00:20:54.040 Atkins, but of course, errors are my own entirely.
00:20:57.360 I just don't want to have to stop all the time and quote him when I'm saying stuff,
00:21:02.160 because many of his words that he's written down will just come flying out of my mouth
00:21:06.600 because I'll be apping what he says when it comes to thermodynamics.
00:21:10.640 Most of my own lessons that I have delivered on thermodynamics were basically me imitating
00:21:14.840 Peter Atkins as he appeared in print, like that heat quote earlier, which I really love
00:21:23.560 It comes flying out of my mouth whenever the topic of heat comes up.
00:21:27.600 And the other guy I'm going to be referring to and I'm going to read snippets from his
00:21:33.920 Paul Davies is of course not only an accomplished physicist, but you know, a polymath of
00:21:37.720 a kind in his own right and one of the most prolific popular science authors ever.
00:21:43.480 And really my first introduction to the idea that the second law had anything like deep
00:21:49.560 implications or philosophical implications came from Professor Davies.
00:21:54.400 And in particular, the mind of God, where I read, well, let me just read that for you
00:22:00.600 from the mind of God to give you a taste of why I was inspired by it and realize that
00:22:06.400 this thermodynamic stuff is up there alongside quantum theory and general relativity as being
00:22:13.120 the stuff that you want to understand better if you want to understand the deepest theories
00:22:18.880 So I've taken the mind of God here and I'm reading a little bit of page 46 over to 47
00:22:25.800 and Paul Davies wrote quote, today we recognize that no star could keep burning forever.
00:22:33.920 This serves to illustrate a very general principle, an eternal universe is incompatible
00:22:39.120 with the continuing existence of irreversible physical processes.
00:22:44.080 If physical systems can undergo irreversible change at a finite rate, then they will have
00:22:52.720 Consequently, we would not be witnessing such changes such as the production and a mission
00:22:59.240 In fact, the physical universe abounds with irreversible processes.
00:23:03.880 In some aspects, it is rather like a clock slowly running down.
00:23:07.680 Just as a clock cannot keep running forever, so the universe cannot have been running
00:23:14.760 These problems began to force themselves on scientists during the mid-19th century until
00:23:19.080 then physicists had dealt with laws that are symmetric in time, displaying no favouritism
00:23:25.480 Using the investigation of thermodynamic processes change that for good at the heart of thermodynamics
00:23:30.720 lies the second law, which forbids heat to flow spontaneously from cold to hot bodies,
00:23:37.200 while allowing it to flow from hot to cold, pausing their my reflection.
00:23:41.080 Notice here, even with the Great Paul Davies, who much respect love dearly as a thinker,
00:23:46.040 he's got the idea of heat flowing there from one place to another.
00:23:49.120 A misconception, I think, a not the best use of language.
00:23:53.040 It doesn't really get across what's actually going on, and it will get to the reason
00:23:56.920 why people still talk in this way, anyway, let's keep going.
00:24:03.680 It imprints upon the universe an arrow of time, pointing away of uni directional change.
00:24:10.440 Scientists were quick to draw the conclusion that the universe is engaged in a one-way slide
00:24:18.600 This tendency towards uniformity wherein temperatures even out in the universe settles
00:24:22.560 into a stable state became known as the heat death.
00:24:26.680 It represents a state of maximum molecular disorder or entropy.
00:24:31.840 The fact that the universe has not yet so died, that is, it is still in a state of less
00:24:38.200 than maximum entropy, implies it cannot have endured for all eternity and quote from
00:24:49.280 An irreversible law that tells us the universe cannot have endured forever.
00:24:54.560 So forget the Big Bang and expanding space-time and Hubble Redshift and so on.
00:24:58.920 All you need to know that the universe actually had a beginning in time is that there is
00:25:08.760 Well, as he says there, it's disorder, okay, but what's that?
00:25:17.320 And we can measure, well that's called mass, the quantity of matter, and we can measure
00:25:20.720 the force of gravity for the effect of gravity on something.
00:25:25.720 And we can measure volumes and we can measure lengths with rulers, but entropy.
00:25:33.040 So I'll come back to Paul Davies, that was the first of his books that I have read, and
00:25:37.040 I recently bought his much recent book, What Eating the Universe and Other Cosmic Questions
00:25:44.760 here, and it too has a chapter all about Times Arrow, the second law.
00:25:50.080 So I'll come back to that, and don't you love the title, What Eating the Universe, which
00:25:56.520 really is bringing the concept of online clickbait into the world of popular science publishing.
00:26:02.400 But that aside, it is actually a great book that chapters are very short, almost little
00:26:07.240 blog posts, again another sign of our times, perhaps.
00:26:10.480 But chapter 16 of the book is titled What is the Source for Times Puzzling Era, so I'll
00:26:18.560 And there's a third book here that I want to mention, there's many books that I'm going
00:26:22.360 to be referring to, but not all of them will get a name check, but I have to name check
00:26:27.560 It's called a cultural history of physics by Carol Simoni.
00:26:32.560 And it's an absolutely beautiful book, I've got the hardcover version, very hard to find
00:26:37.160 now, though, in hardback form anywhere I've been looking for other copies of, very difficult
00:26:44.080 But if you can get a hold of it, if you have someone in your life who absolutely loves
00:26:48.280 physics, then this is the gift for them, it's obviously a history of physics.
00:26:52.440 But it's got all sorts of little gems in there, like little biographies of the physicists
00:26:56.920 and nice, clear images of original texts and diagrams taken from, you know, the original
00:27:03.440 work of like Newton, Newton's Principia or Descartes own notes or all the sections on quantum
00:27:08.800 theory have juke quotes from dueling physicists trying to understand what the heck was going
00:27:13.680 on exactly pages from Einstein's first article on relativity and so on, and yeah, I understand.
00:27:19.160 All of this stuff can be found online these days, but having it in one place in chronological
00:27:23.840 order as well as a history of physics, that's really nice.
00:27:27.360 As I say, you could find it online, but here someone else has done all of the hard work
00:27:32.000 for you, and the author unpacks what it all means from the perspective over the time,
00:27:37.880 what they were understanding, the philosophical problems they were having at the time, and
00:27:41.720 from our perspective now, given what we know, but what they couldn't have.
00:27:46.320 So actually, I'm going to go to that book right now and read from a section which indicates
00:27:51.040 the kind of subtleties of language in this area of thermodynamics that I've mentioned
00:27:55.120 already, and how there has been this resistance at times in the history of science and
00:28:00.840 in physics in particular, to take seriously the best prevailing theory at any given time.
00:28:07.400 So it's something like heat, as I've already spoken about, well, Simon you, he writes himself,
00:28:14.200 One would expect that ideas concerning the nature of heat would have been based on a conception
00:28:19.000 that was already widespread at the end of the 17th century, namely that heat has its
00:28:23.920 origin in the motion of the particles that make up the material body.
00:28:28.360 This would have led directly to the connection between the two forms of energy, heat and
00:28:36.920 In a seemingly superfluous and at first glance surprising detour in the history of physics,
00:28:42.560 the kinetic theory of heat was abandoned, and in its place, a theory of heat substance.
00:28:50.280 It is only the result of our hasty judgment about what should have happened that names
00:28:54.560 such as Joseph Black have fallen into obscurity.
00:28:59.240 Although we owe our thanks to him for such quantitative concepts as heat quantity, specific
00:29:05.240 heat, latent heat, melting point and boiling point, it has also been forgotten that findings
00:29:10.280 in canoes and Fourier's theory of heat that are seen today as fundamental and used in
00:29:15.560 teaching are based on the theory of calaricum, based on this theory of heat being a substance.
00:29:22.200 And that is why there is this misconception in our language that we inherit today.
00:29:26.720 I should have said it in quote there, but you get the picture.
00:29:29.360 And in that bit that I just read there, you might have noticed a quibble as well.
00:29:34.440 Simyani is praising Black for the concept of heat quantity, but heat quantity itself is
00:29:39.760 also one of those very misconceptions someone like Atkins is trying to help us understand
00:29:46.200 So let's just move past that, that can be a little speed pump.
00:29:49.160 And Simyani brings up Joseph Black, a name who's fallen as he says into obscurity, because
00:29:55.400 actually he did as much as anyone and should be credited with some of the first formulations
00:30:02.000 Joseph Black was Scottish and he lived from 1728 to 1799, it was a professor of chemistry
00:30:08.560 and medical science and Black taught James Watt among others.
00:30:13.720 And he introduced the concept of specific heat as was mentioned just there.
00:30:18.720 Now what specific heat exactly or find and explain that as being like the absorbency
00:30:24.880 of a cloth, some cloths like you know tissues can hold very little water before becoming
00:30:32.080 While others like a sponge can hold much more water specific heat or let me talk about
00:30:37.160 specific heat capacity, it's the quantity of energy that a substance can hold or more
00:30:43.160 precisely the quantity of energy taken to raise the temperature of a substance or if we want
00:30:50.200 to be exact with this, it is the quantity of energy usually in jewels these days required
00:30:56.400 to heat a unit mass, usually in kilograms by one Kelvin, which is equivalent to one degree
00:31:04.640 Basically if I have a one kilogram lump of metal like a lump of iron and I put it over
00:31:10.200 a flame for one minute, it's temperature will rise quite a lot.
00:31:15.240 It has low specific heat capacity, it doesn't take much energy to raise its temperature.
00:31:21.640 As compared to, if I was to take one kilogram of water, which is a liter of water and
00:31:27.320 use the same flame to heat it, presumably it's in a saucepan of some kind or a pot,
00:31:32.560 in one minute you don't get anywhere near the same temperature rises what you do with
00:31:36.720 the iron, there is an inherent property, therefore, and inherent property of substances
00:31:42.200 that determines how much their temperature rises given some change in their internal energy.
00:31:53.320 Another concept that Joseph Black was first to figure out was latent heat and it's a
00:31:58.320 similar idea if you have one kilogram of water and it's boiling at 100 degrees Celsius,
00:32:04.200 and there's a certain quantity of energy it takes to boil away all of that water.
00:32:08.400 In other words, to change one kilogram of water in its liquid form at 100 degrees Celsius
00:32:13.480 into its gaseous form at 100 degrees Celsius, that's what latent heat's all about.
00:32:19.240 Now for other substances, if you've got one kilogram of it, let's say one kilogram of
00:32:23.960 pure alcohol and it's boiling, the amount of energy it takes to change its state from
00:32:28.680 liquid to gas is less, that's what latent heat is.
00:32:32.240 And there's latent heat for solid stuff turning into liquid stuff and latent heat of
00:32:37.040 liquid stuff turning into gaseous stuff as well, or in some cases, solid straight into
00:32:41.960 gasses in the case of carbon dioxide, let's say.
00:32:45.000 So this idea of specific heat and latent heat can be a little bit confusing because right
00:32:50.080 there, if you're Joseph Black and you have some sound concepts like that, latent heat
00:32:55.720 and specific heat, easily tested and measured in the chemistry lab.
00:33:00.040 It looks for all the world like latent heat and specific heats are kinds of heat and thus
00:33:05.200 heat is something that is itself a thing of a kind, a substance of a kind, so there's
00:33:13.720 And when you increase the temperature of something, the heat goes up and decrease the temperature
00:33:20.280 And surely it's common sense that if you heat something strongly enough, like a metal rod
00:33:24.560 that I was talking about earlier, you heat one end and eventually the other end gets hot
00:33:28.200 too, why, well, the common sense theory goes that the heat is flowing, conducted, so we
00:33:34.200 Now, as I explained before, that contains misconception.
00:33:37.720 It's not like it's utterly wrong, I don't like to say anything like that is utterly
00:33:42.160 wrong, it contains some truth, but it also contains important misconceptions.
00:33:48.160 But to explain more fully those important misconceptions with that whole view of heat, let's
00:33:53.480 do a pass of the four laws as well that say I would normally explain them if I had to
00:34:01.120 And this will allow us to understand the misconceptions in this idea of heat flowing from
00:34:05.800 here to there, from hot bodies to cold bodies and bodies, having heat in them and so on and
00:34:11.480 And by going through these laws of thermodynamics, we'll be able to then, before the
00:34:17.000 end of today's lengthy episode, come back and linger on the deeper implications of the second
00:34:24.400 This will set us up well, I hope, for what constructor theory has to offer, that's new,
00:34:30.160 and we'll be able to introduce Kiara's chapter on heat and work.
00:34:36.720 And the zeroth law basically forces upon us the concept of temperature.
00:34:42.160 Why is it the zeroth law and not the first law?
00:34:46.080 The first law was found first, and later it was understood that prior to understanding
00:34:50.880 parts of the first and second law, we needed a law governing what temperature was, what
00:34:57.240 So temperature is this interesting concept in and of itself, so they introduced the zeroth
00:35:06.600 And that's fine, you can say that, but it's qualitative.
00:35:09.800 Now you could say that temperature is the thing that a thermometer measures, and that's
00:35:13.840 also true, but we want to know what it's measuring precisely.
00:35:18.480 What is it that's going on, causing the thermometer to indicate one temperature rather than
00:35:25.760 Well, we've already said that's not a thing, but even if you imagine it is, you might imagine
00:35:30.280 something like the red-hot nail compared to a bath full of boiling water.
00:35:36.320 Now the red-hot nail might be a thousand degrees Celsius.
00:35:40.240 The bath of boiling water is cooler by a factor of 10, but if a torturer gave you the
00:35:46.360 choice of holding either the nail or plunging into the bath, there really is no choice.
00:35:54.760 Sure you'll burn your hand, but you won't be dead.
00:35:58.280 The bath contains far more energy, even though it's at a much lower temperature.
00:36:05.320 So temperature has something to do with intensity rather than quantity, intensity of what
00:36:14.240 I've already told you, but we're going to make this more precise.
00:36:18.160 If you consider the air in a room at 30 degrees Celsius, the most of that air is made up
00:36:24.200 of nitrogen, nitrogen exists as N2 molecules, two nitrogen atoms join together.
00:36:30.840 And at 30 degrees Celsius, a nitrogen molecule has an average speed of about 500 meters
00:36:38.880 Now if you increase the temperature of the room, the average speed of the molecules will
00:36:48.400 The temperature is a measure of the average speed of the particles.
00:36:52.360 Well that's all very well, except that if the nitrogen is at 30 degrees, and that corresponds
00:36:57.360 to 500 meters per second, what about the chair in the same room as the air?
00:37:04.360 The chair is made of wood or metal or plastic, and its particles are not zipping around
00:37:14.000 So this is a bit of a problem, because although it is true that increasing the temperature
00:37:17.320 of a body increases the speed of the motion of the particles, particles have different
00:37:21.920 masses and they're bonded to each other more or less strongly.
00:37:26.040 So it can't be a one to one thing of that a particular temperature corresponds to a particular
00:37:33.120 So we need a somewhat more precise conceptual understanding of temperature.
00:37:37.920 We might have more luck if we weren't just talking about speed, but we're talking about
00:37:41.840 kinetic energy of the particles, because kinetic energy takes into account the mass of
00:37:46.520 the particles as well, but still can we have something straightforward that everyone can
00:37:54.960 If I've got two bodies, A and B that are in contact and isolated from the environment,
00:38:01.720 then if A is hotter than B, energy moves from A to B until A is no longer hotter than
00:38:09.880 B, nor B hotter than A, they have become equal in some way.
00:38:16.000 What is it exactly that has become equal between them or the temperature has?
00:38:21.480 More precisely, we say that A and B have the same temperature when they are in thermal
00:38:29.120 One statement of the zeroth law of thermodynamics is, if A is in thermal equilibrium with
00:38:35.800 B and B is in thermal equilibrium with C, then C and A will be in thermal equilibrium.
00:38:44.520 So it's a law of thermal transitivity effectively.
00:38:48.000 The zeroth law implies the existence of a thermometer.
00:38:52.240 It's the device in thermal equilibrium with its surroundings.
00:38:55.480 So none of that statement of the law even implies the existence of particles you will notice.
00:39:01.040 As Atkins famously says, you can do classical thermodynamics even if you don't believe
00:39:09.440 So as a result, we have this thing called statistical thermodynamics, which is an account
00:39:14.480 of what is happening according to the laws of thermodynamics in terms of particles or atoms.
00:39:20.720 It's statistical because we are less concerned about what individual particles are doing and
00:39:25.040 more about aggregates or averages that give rise to the bulk properties that we do observe.
00:39:30.600 It was Ludwig Boltzmann in the 1800s, actually, who provided a view of temperature that
00:39:36.480 is connected to particles and I've already hinted at it.
00:39:39.800 The thing about Boltzmann's view from statistical thermodynamics is that it provides some
00:39:45.160 insight into quantum theory, which came a little later.
00:39:48.440 If we've got a glass of water at room temperature, then we know that left long enough,
00:39:57.920 Doesn't water only change state from liquid to gas when it boils?
00:40:02.440 How can we explain evaporation that happens at any temperature?
00:40:08.640 Why is it that if water changes from gas, what temperature does the water change from
00:40:14.120 liquid into gas people will say, well, at the boiling point, at 100 degrees Celsius, if
00:40:17.600 you're not an American using Fahrenheit, let's say?
00:40:21.800 Why should it be the case that any temperature less than the boiling point at the temperature
00:40:25.840 at which the liquid turns into a gas that you still get a liquid turning into a gas?
00:40:32.600 Well, water can change in its liquid form into a gaseous form at any temperature because
00:40:37.520 the temperature of the water, in terms of the particles, has something to do with the
00:40:42.480 distribution of energies of those particles, and those particles have a range of energies.
00:40:48.880 Not any energy that you like, that's quantum theory there.
00:40:52.360 They must have specific energies, but they can have a range of energies.
00:40:57.680 At any given temperature, most of them will have a certain kind of energy, or be grouped
00:41:03.440 up into a particular kind of energy, but some of them will have much less energy than
00:41:08.640 the average, and some will have much more energy than the average.
00:41:11.760 And maybe you can see where I'm going with this.
00:41:14.120 In any average typical glass of water at room temperature, there will be some small number
00:41:19.280 of water molecules in your glass of water that have the lowest possible energy they could
00:41:25.080 And that corresponds to energy at or very close to what would be regarded as zero Kelvin.
00:41:30.480 So some molecules of water in a glass of water at room temperature can't vibrate any
00:41:38.000 And some will be vibrating basically not at all.
00:41:44.320 Therefore their temperature corresponds to something like zero Kelvin minus 273 degrees
00:41:50.520 Not many of them, not many of them of course, but some, most of them will have energies
00:41:58.480 But if you don't accept that, well, you have to accept that, well, some of the water molecules
00:42:02.800 in any given room temperature glass are literally boiling away.
00:42:09.320 They have the energy required to change the state of the water from liquid into gas.
00:42:20.040 As the temperature of the water rises, a greater and greater proportion of the molecules
00:42:24.560 of the water molecules begin to occupy those higher energy states.
00:42:29.120 Hence more of them are turning into gas, achieving a escape velocity from the rest of
00:42:33.960 That's why evaporation tends to increase as the water increases in temperature.
00:42:38.800 Now the energy of particles like molecules of water comes actually in three kinds.
00:42:43.760 It comes in what I've already mentioned, vibrational, which is all that solid particles
00:42:48.480 can do there, just fixed in place and they're vibrating because the bonds that hold them
00:42:58.480 And rotational energy is the kind of energy that your particles get.
00:43:04.880 So the bonds break and now they're able to rotate around one another, still in contact,
00:43:12.840 But in physical contact with one another, they're still vibrating.
00:43:15.600 But now they're actually also able to rotate and that's in the liquid phase.
00:43:19.280 They can slide around each other once those solid bonds are broken.
00:43:24.480 And then finally, if you add a little more energy, you get translational energy as well.
00:43:33.160 But now they can move from one place to another.
00:43:37.720 That's what happens to move from solids where the particles are vibrating fixed in position
00:43:44.680 But now they're also able to rotate because the bonds are broken.
00:43:47.400 And then once all the bonds are effectively broken, the intermolecular bonds that exist
00:43:51.880 in liquids like water, once they're broken as well, although you have vibration and rotation,
00:43:59.520 So they're the three modes of kinetic energy that you can have.
00:44:05.440 You can quantify this using something called the Boltzmann distribution.
00:44:11.720 The parameter, beta, on how the energy of the molecules at some temperature are distributed.
00:44:20.840 There is a simple equation, beta equals 1 over kT, where T is the temperature in Kelvin,
00:44:28.320 Kelvin temperature, and k is the Boltzmann constant.
00:44:32.200 The higher the T, the smaller the beta, and vice versa.
00:44:36.120 Temperature is thus a measure of the distribution of energies of particles in some substance
00:44:45.520 The zero floor has forced upon us, has explained the concept of temperature for us, either
00:44:51.840 classically as that quantity, which is equal when two bodies are in thermal equilibrium,
00:44:56.720 or in terms of particles as that quantity, which indicates the distribution of the energies
00:45:11.920 The idea here is that however much energy there is at the beginning of the universe, that's
00:45:16.960 how much you have at every other time, at any other time in fact.
00:45:20.840 Pick your year or moment after the big bang, and you've got the same amount of energy
00:45:24.880 in the universe then as what you had at the big bang.
00:45:30.480 The zero floor introduced temperature and refined its meaning for us.
00:45:34.920 The first law is really about trying to get at what we mean by energy, especially internal
00:45:45.160 I said I didn't like to get fixed on definitions, but here's one that we can use.
00:45:49.320 It's very useful and people don't have quibbles with.
00:45:58.760 The work has to be done in the same direction as the force.
00:46:05.760 It takes some force to overcome the friction on the ground.
00:46:08.880 Someone asks you to move the fridge five meters.
00:46:11.080 That's one thing that's a certain amount of work for you to do, a certain amount of effort.
00:46:14.840 But to move it 50 meters, that's something else entirely.
00:46:24.080 And in fact, lifting is the best way of envisioning this.
00:46:27.360 You lift a weight vertically against gravity and you've done work.
00:46:31.000 We're speaking in Newtonian turns here, of course.
00:46:36.320 You can lift a one kilogram mass with your hand, but presumably so could an electric
00:46:44.280 And maybe that motor is powered by an electric battery.
00:46:47.240 So the battery has capacity to do work as well.
00:46:50.080 Or maybe some coal can be burned and that drives a turbine that lifts the mass.
00:47:02.520 Maybe there are some kinds of energy that can't do work.
00:47:12.360 And work is the capacity to exert some force over some distance.
00:47:17.920 It's concepts have something to do with the common sense notions that we have of these
00:47:21.720 things work in energy, but they're sharpened up by physics.
00:47:25.640 Now there's this standard high school physics experiment.
00:47:28.600 It's due to dual who first performed the experiment where basically a falling weight over
00:47:34.720 a pulley drives some paddles that stir some water.
00:47:38.680 You know, perfectly well insulated, well insulated as you can manage, container of water.
00:47:48.240 Because the work done goes straight into the water and from there, well, it's in the
00:47:53.440 water, it can only cause the temperature to rise.
00:47:58.080 Well, it shows that work, the falling overweight can be used to heat water.
00:48:03.880 You can convert work into heat and vice versa, of course, as my little sterling engine
00:48:10.680 But with this experiment, this is a dual experiment.
00:48:14.080 In the high school lab, you can make some precise measurements and show that using an actual
00:48:19.240 heater to heat the water requires the same energy.
00:48:22.920 You can use equations like energy equals power times time or equivalently energy equals
00:48:29.920 And they can be used to calculate the work done by a heater of known voltage and current
00:48:39.200 Well, that introduces this idea of path independence.
00:48:42.880 It does not matter how the temperature changes come about, whether by heat or by work,
00:48:50.600 But although earlier, we were talking about kinetic energy of particles and so on, here,
00:48:54.920 in this case, of rising temperature, we can talk about the specific number of joules of
00:49:00.040 energy imparted to the water, but we don't measure temperature using joules.
00:49:05.200 So what happens to these joules of energy, imparted by the heater or by the paddle?
00:49:13.000 But again, not as a separate fluid of some kind.
00:49:15.640 After all, the paddles weren't doing anything, but agitating the water.
00:49:20.440 We say they have gone into a quantity we call the internal energy and we use the symbol
00:49:28.880 So the internal energy of the system, of the water.
00:49:32.120 When the temperature rises in a system like a cup of water or whatever, we say that U has
00:49:38.480 Nothing is increased here, yes, the temperature has, but also the number of joules have
00:49:44.040 increased where in the internal energy of the water.
00:49:47.720 Now, what the internal energy is exactly, we don't need to worry ourselves about exactly
00:49:53.760 We just know that it's gone up or gone down because then we can calculate the change by
00:49:58.960 But if you want to know now that I'm going to come back to this, the internal energy
00:50:02.040 is the sum of all the kinetic and potential energies of the particles that make up the substance.
00:50:07.240 And perhaps even also the mass energy, but calculating the total internal energy of any
00:50:12.920 Well, no one ever bothers with that, but we're only ever interested in the change in
00:50:18.880 That's the most relevant thing for when you're building engines and so forth.
00:50:22.440 Now if we imagine joules experiment where the paddles spin, the temperature rises, there's
00:50:32.800 The thing is, if we take away the insulation, then more energies are quiet in order to achieve
00:50:47.000 It's going into the surroundings because the things aren't insulated anymore.
00:50:50.560 But what this shows profoundly is that energy, therefore, is of two types.
00:50:57.000 You do work on something that's well isolated and the temperature rises because you've
00:51:02.200 increased the internal energy of the system in the water.
00:51:05.920 But if you remove the insulation, then you must do more work because the energy has gone
00:51:12.360 Well, there has been a transfer of energy to the environment and not by work.
00:51:22.320 The reason the energy has been lost to the environment is because there is a temperature
00:51:26.000 difference between the water now, which is warmer, and the rest of the environment around
00:51:35.120 This transfer of energy as a result of a temperature difference is called heat.
00:51:41.920 Again, heat is the transfer of energy as the result of a temperature difference.
00:51:47.840 As I quoted him earlier, it is not the name of the thing, but rather the name of a process.
00:51:52.960 We can measure the energy transverse heat, therefore simply by determining the work done
00:51:59.640 And then measuring the difference between that case and when the insulation is removed,
00:52:03.800 the difference is the energy transferred as heat, usually to the environment.
00:52:08.320 Now there is no such thing as perfect insulation of course.
00:52:11.440 So if work is done on a system and that changes its temperature, its internal energy,
00:52:16.840 then the work done is never exactly equal to the change in internal energy.
00:52:26.520 So energy is transferred to substances either by work or by heating.
00:52:31.800 In the case of work, what is going on is that there has been, at the level of some particles,
00:52:36.400 some uniform motion of the atoms in the case of joules apparatus.
00:52:41.040 The molecules are all pushed in the same direction by the paddles.
00:52:44.880 Work is force over a given distance in the direction of the force.
00:52:48.360 So all the particles end up moving in the same way.
00:52:51.520 But when a substance is heated, that's not uniform motion of the particles.
00:52:55.960 However, there is an increase in the random motion of the particles.
00:52:59.480 Their kinetic energy, either of translation and vibrational rotation, increases.
00:53:07.880 Both of these things can cause a temperature rise.
00:53:10.280 But one is an average bulk motion all in the same direction.
00:53:14.560 That's work or randomly sort of causing all of the particles to speed up in their motion.
00:53:24.440 And if, if mind you, I, W, if and only if, there was a perfectly insulated container
00:53:30.360 of water, and you did work on the container of water, then the amount of work done would
00:53:34.200 be transferred to the water entirely and be represented as a temperature increase.
00:53:39.320 The first law says that the work done, W, must be equal precisely to the increase in
00:53:46.680 So W would equal delta u, work equals the change in internal energy.
00:53:52.520 And that's the first law for a perfectly isolated system.
00:53:55.720 Of course, if it's not perfectly isolated, then W equals delta u plus q, where q is the
00:54:02.640 energy transferred as a consequence of heating.
00:54:05.960 So that is the first law that the work done is equal to the change in internal energy,
00:54:11.480 but plus heat, the heat lost to the environment, let's say.
00:54:15.840 Now normally, text and so on actually write that first law as delta u equals q minus
00:54:22.280 But for size, I think we can measure only changes in u, not any absolute amount of u.
00:54:31.280 So it's the sum of all the kinetic energies, the motion, and the potential, the bond
00:54:38.480 And as I say, presumably it can also include things like the mass energy as well, if you
00:54:43.040 So that's the first law, which means we're at the second law.
00:54:45.400 And at this point, I'm just going to hand things over wholesale to Peter Atkins.
00:54:49.840 And his book called Four Laws that Drive the Universe.
00:54:54.080 And the beginning of his chapter on the second law.
00:54:57.160 Now here, I'm going to be reading from page 49, where Atkins writes, quote, when I gave
00:55:03.160 lectures on thermodynamics to an undergraduate chemistry audience, I often began by saying
00:55:08.360 that no other scientific law has contributed more to the liberation of the human spirit
00:55:15.680 I hope that you will see in the course of this chapter why I take that view, and perhaps
00:55:23.600 The second law has a reputation for being recondite, notoriously difficult, and a litmus test
00:55:31.200 Indeed, the novelist and former chemist, C.P. Snow is famous for having asserted in his
00:55:37.160 the two cultures that not knowing the second law of thermodynamics is equivalent to never
00:55:45.080 I actually have serious doubts about whether Snow understood the law himself, but I can
00:55:50.800 The second law is of central importance in the whole of science, and hence in our rational
00:55:56.040 understanding of the universe, because it provides a foundation for understanding why any
00:56:01.120 change occurs, thus not only is it a basis for understanding why engines run and chemical
00:56:06.920 reactions occur, but it is also a foundation for understanding those most exquisite consequences
00:56:15.120 The acts of literary, artistic, and musical creativity that enhance our culture, and quote
00:56:22.600 So that's pretty amazing stuff, and it really is why people like Paul Davies and
00:56:27.120 other popularizers make such a big deal about the second law.
00:56:30.880 What Atkins says there puts the second law of thermodynamics into a sort of different category
00:56:36.880 It is elevated to this place where it is invoked alongside not only physics and chemistry
00:56:44.240 So let's get a little technical on this and go back to Atkins, who writes, quote,
00:56:49.360 as we have seen for the zeroth and first laws, the formulation and interpretation of a
00:56:54.600 law of thermodynamics leads us to introduce a thermodynamic property of the system.
00:57:00.800 The temperature T springs from the zeroth law, and the internal energy U from the first
00:57:07.160 Likewise, the second law implies the existence of another thermodynamic property, the entropy
00:57:13.960 To fix our ideas in the concrete as an early stage, it will be helpful throughout this
00:57:18.560 account to bear in mind that whereas U is a measure of the quantity of energy that a system
00:57:23.800 possesses, S is a measure of the quality of that energy.
00:57:28.840 Low entropy means high quality, high entropy means low quality, end quote.
00:57:38.240 Here's the way I used to think about this, and I can't remember where I heard it first,
00:57:43.400 but I know Brian Cox used it in one of his documentaries, presumably we both got it from
00:57:50.000 Anyways, the metaphor goes like this with a little bit of local adaptation.
00:57:54.840 Here in Australia, we've got some very nice beaches.
00:58:01.040 It's called Himes Beach, and it's close to where my parents live.
00:58:04.200 It's famous if you move in some circles because it's said to have, among, the whitest
00:58:11.760 So if you go there on a typical Australian summer's day in early January's day and you
00:58:16.160 go without shade and without sunscreen, you will get sunburned.
00:58:20.320 The sun is intense in Australia in summer, especially in places like Himes Beach.
00:58:25.040 Sunburn is caused by ultraviolet light, UV light, comes down from the sun and it can
00:58:33.160 Now throughout the course of a day, that sunlight, that bright sunlight from the sun, comes
00:58:38.240 down beaming all day long, heating the sand, as well as the water.
00:58:45.000 It heats it all day long for a good 10 hours or so, ignoring the less bright times of
00:58:51.160 So it's unsurprising that at night, once the sun is gone, the sand is still warm and it
00:58:57.080 will gradually cool over the course of the night.
00:58:59.880 But anyone who goes to the beach will know that beach sand is warm even well after sunset.
00:59:07.360 Well, the first law of thermodynamics, of course.
00:59:09.360 The heating of the sand during the day by the sunlight causes a change in the internal
00:59:13.520 energy of the sand and that is noticeable by a change in temperature of the sand.
00:59:18.320 The heating happens because there is a temperature difference between the sun and the
00:59:23.400 The sunlight has a higher temperature and it heats the sand, which is cooler and it does
00:59:32.880 So at night when the sun is gone and it goes dark because the earth is facing away from
00:59:39.040 And the temperature difference between the sand and the cool air and the dark sky now
00:59:44.200 means that the same process has happened but in reverse.
00:59:47.920 The energy gained from the sun is now lost to the atmosphere, which is then lost to
00:59:53.800 The sand heats the air above it and it gradually cools.
00:59:57.080 It gained by the sun during the day is lost by the sand at night.
1:00:01.520 And this goes on day after day, year after year, year after year, year after year and just
1:00:07.560 Because if it was not the case and there was not this equilibrium, this equality between
1:00:12.760 energy and energy out, if the energy gained by the sand from heating by the sun during
1:00:18.000 the day was not all lost at night by an equal amount each day, then the sand would be
1:00:23.640 hotter the next day and the day after that and the day after that.
1:00:26.840 It wouldn't be long before the sand was so hot, it was glowing red hot.
1:00:31.760 There is a relatively constant temperature of the sand during the day and during the night.
1:00:37.080 All the energy gained on Monday is lost Monday night only to be regained again on Tuesday
1:00:42.680 and lost Tuesday night and so it goes with no net increase of energy by the sand.
1:00:48.720 The quantity of energy gained equals the quantity of energy lost.
1:00:55.480 Before the energy is accounted for, none is lost from the universe or created from nothing.
1:01:05.480 If the energy that comes from the sun in the daytime is in the form of UV light which
1:01:10.360 can sunburn you and a visible light which helps you see as well as some other things,
1:01:15.840 then why at night is it not radiated back into outer space as UV light and a visible light?
1:01:22.120 In fact, it's only irradiated back to outer space, broadly speaking, as infrared radiation.
1:01:28.080 So what's happened to the UV and visible light?
1:01:35.080 The infrared radiation from the sun is not the only kind of radiation from the sun that's
1:01:40.040 The sand, like a human skin, also absorbs UV light and that's coming from the sun during
1:01:46.200 We know we absorb it, we know that skin absorbs UV radiation because we can get sunburned.
1:01:50.320 But if that UV radiation and the visible light is absorbed by the sand, why can't we get
1:01:56.600 sunburned at night as the UV light is re-emitted back into outer space?
1:02:02.240 For that matter, why doesn't the sand glow with visible light at night so as to return
1:02:06.840 all the visible light energy it absorbed during the day?
1:02:11.680 Although the quantity of energy is the same, absorbed during the day and emitted at night,
1:02:19.560 The energy absorbed during the day is degraded in this process.
1:02:24.720 At night, the high quality stuff, the UV and the visible light, is all of it degraded
1:02:30.600 to a longer wavelength, lower frequency, lower quality, less useful kind of energy.
1:02:36.920 At night, as infrared radiation, that our eyes cannot see, but our skin can feel.
1:02:42.120 The overall quantity of energy re-emitted at night is the same, but the quality has changed.
1:02:49.160 And this quality of energy can be quantified as a thing called entropy.
1:02:56.640 Now I said there, in that account, the energy from the sun becomes less useful as it
1:03:05.200 Well, here we can turn to some history and Sadie Carnot, another great name from thermodynamics.
1:03:12.120 From the early 1800s, he looked at how to make engines more efficient.
1:03:17.880 First story short, I'll just give you the punchline to this bit of science, the efficiency
1:03:23.720 In other words, how much of the heat will be converted into useful work is given by this
1:03:29.040 The efficiency equals one minus the temperature of the sink divided by the temperature
1:03:35.720 So, you know, here we had the sterling engine going on earlier on, and my cup is the source
1:03:42.680 And the sink is the rest of the environment here in my room.
1:03:45.480 This is the formula for maximum efficiency.
1:03:48.520 So today it's like 23 degrees Celsius in here, and my cup is 98 degrees Celsius there.
1:03:55.880 We need to convert things to Kelvin to get this equation to work.
1:03:59.520 So we've got the temperature of the sink or the environment here is 273 plus 23.
1:04:06.960 And the temperature of the source, well, it's about 98 degrees, that water is not quite
1:04:10.800 boiling, but 273 plus 98 gives me 371 Kelvin.
1:04:15.960 Now putting all this into our equation, one minus 296 over 371, that works out to be about
1:04:25.360 Now the way to improve this is to have higher temperature of the source, or lower temperature
1:04:31.760 Ideally, let the sink temperature approach absolute zero, or ideally let the source temperature
1:04:37.800 approaching infinity, but how do you do either of those things?
1:04:41.280 Real life engines run on fuels that burn at particular temperatures.
1:04:45.920 Real life sinks are the environment of the earth, which have a fixed temperature as well.
1:04:51.080 The sink, the environment, is why the energy is lost as heat in these situations, and
1:04:59.560 We need the sink to push the heat energy away so that the bits continue to move around
1:05:04.640 because we need those temperatures to be as far apart as we can get them in order for the
1:05:11.760 Or consider it another way, let's imagine a power station.
1:05:14.880 Here's a good diagram of a coal fired power station.
1:05:18.640 I say this diagram is good because it emphasizes those really important.
1:05:22.880 This thing here, this thing here is the cooling tower.
1:05:27.560 Whenever you see pictures of power stations, you see these things, and they usually have
1:05:33.800 The environmentalists use those pictures to imply that's the pollution.
1:05:37.120 Well, if you think water vapor is pollution, well, that's your business.
1:05:40.800 They should be showing the smoke stacks, which are these things.
1:05:44.600 Problem is, that the smoke stacks almost never have any visible smoke coming out because
1:05:48.840 modern power stations, coal fired power stations, they filter out the particles.
1:05:53.360 The only thing that's coming out, really, is carbon dioxide.
1:05:56.240 But anyways, why not in a situation like this?
1:05:59.280 If the power station is doing its job, converting heat to work, why waste the heat coming
1:06:09.480 Then that can generate some more electricity.
1:06:15.080 Sure the hot steam can do less work as it passes through the first turbine, but who cares?
1:06:21.880 Well, the problem is, that means the steam slows down here, slowed down by the second
1:06:27.480 turbine, so things begin to pile up, and it begins to heat up.
1:06:33.080 So for this turbine here, the temperature here, and the temperature here, quickly approach
1:06:37.680 approximately the same, the efficiency reduces.
1:06:40.880 The only reason this is spinning at all, this first turbine, is that the steam is high
1:06:46.480 pressure here, low pressure here, because the lower temperature here.
1:06:50.880 So it's rushing to fill the low temperature void, but if you put another turbine there
1:06:55.280 in an attempt to capture that lost heat, to do work with it, the only thing that happens
1:07:02.280 And so whatever you think you've gained here with the second turbine, you've lost from
1:07:09.480 As some people put it with the first law, they say the first law is a statement of how
1:07:16.080 In other words, you cannot get work done for nothing, so sometimes people say that.
1:07:20.680 The first law is, you can't win, the second law is, you can't break even, and the third
1:07:29.480 So anyways, here we have it that in systems for converting heat to work, the process cannot
1:07:34.400 be perfectly efficient, and some of your work is lost as heat.
1:07:38.760 So you have some heat here, and not all of it becomes work.
1:07:42.080 By necessity, it has to be lost, and that's an irreversible change.
1:07:47.440 We cannot capture that heat out there somehow, and bring it back into our power station.
1:07:51.640 Doing so increases the temperature, and in the long run slows down the whole thing grinding
1:07:57.320 If it was an isolated system, the whole power station, what would happen?
1:08:02.920 Thermally equilibrium, and that would mean zero motion anywhere.
1:08:06.000 Now just to drive this point home a little further, because we did, if you remember the
1:08:11.720 parable of the beach, where I was talking about how, although ultraviolet light and
1:08:18.600 visible light are coming down amongst other things, onto the beach, onto the sand, hitting
1:08:23.640 the sand throughout the course of the day, in the evening, what is re-emitted back into
1:08:28.400 outer space is the same quantity of energy, but not the same quality of energy.
1:08:33.040 The energy has been degraded to longer wavelengths of light, and so ultraviolet light
1:08:38.200 is not coming from the beach during the night time.
1:08:41.600 With the power station, something similar is going on.
1:08:45.840 What's happening here is that the energy is degraded after it's done some work, so that
1:08:51.800 this heat energy here is of, we say, higher quality.
1:08:55.760 But the heat that's coming out here is of lower quality.
1:09:01.760 And remember right at the beginning of all this, I was talking about how energy is that
1:09:06.880 thing, which has the capacity to do work, that's what we said a definition of energy could
1:09:12.880 However, in this case, we have energy that is not quite so capable of doing work.
1:09:19.040 As I said, after all, one thing that the naive person might think is that we could put
1:09:24.760 another turbine right there in order to capture the heat energy coming from the first
1:09:34.120 It's just being let off into the atmosphere there.
1:09:36.840 But as I said, that's merely going to cause the temperature here and the temperature here
1:09:43.480 And if those temperatures are equal, then this thing is going to stop spinning.
1:09:47.960 There's no reason for it to keep going because there's no reason for a pressure differential
1:09:52.640 anymore between this point and that point if the gas in both places is at the same temperature.
1:09:59.080 And so therefore we say that the energy has been degraded, there has been an increase in
1:10:10.000 And in the limit, the heat energy lost into out of space is actually energy unable to
1:10:16.920 Perhaps even in principle, it is unable to do work.
1:10:20.680 And so then we say, well, what does it mean to say that all energy is this thing that
1:10:26.720 has the capacity to do work when some of it does not have the capacity to do work?
1:10:31.280 Well, it's an interesting scientific philosophical question that we can get into if we originally
1:10:35.400 defined energy as being that thing that could do work in principle.
1:10:39.840 But some of it, after being degraded by the second law, is ultimately unable to do work
1:10:48.480 Well, it's still energy of a kind, but it's degraded and unable to do work, and therefore
1:10:52.680 violates what we originally said energy was.
1:10:56.760 This formula of Carnot's for efficiency, it's worth reading what Atkins actually says
1:11:05.920 And he wrote, at control, quote, Carnot's analysis established a very deep property of
1:11:10.160 heat engines, but its conclusion was so alien to the engineering prejudices of the time
1:11:15.920 that it had little impact, such as often the fate of rational thought within society
1:11:22.600 sent as it may be to purgatory for a spell, end quote.
1:11:28.400 That's worth keeping in mind when we think of David and Kiara's work on all this.
1:11:33.320 Anyways, this problem of the power station can be summed up in what is known as the Kelvin
1:11:38.920 statement of the second law of thermodynamics, which is no cyclic process is possible
1:11:45.600 in which heat is taken from a hot source and converted completely into work.
1:11:52.480 Something is said not to be possible, which is a counterfactual claim, the science of
1:11:58.640 So I'll read it again, no cyclic or cyclic process is possible in which heat is taken
1:12:04.560 from a hot source and converted completely into work.
1:12:08.480 Now, I really have to go back to Atkins here and just read what he says about this and
1:12:14.200 about cold sinks, quote, there must be a cold sink, even though we might find it hard
1:12:20.200 to identify and it is not always an engineered part of the design.
1:12:24.320 The cooling towers of a generating station are, in this sense, far more important to
1:12:29.840 its operation than the complex turbines or the expensive nuclear reactor that seems to
1:12:36.960 Yes, sir, the heat sink is a crucially important part of these thermodynamic systems so
1:12:45.680 that you can have this transfer of energy from the hot to the cold, which is the thing
1:12:52.440 There's another way of putting the second law and it's kind of inconvenient that there
1:12:56.280 are this variety of ways of putting things qualitatively speaking, but quantitatively
1:13:01.480 it turns out that can be shown to be equivalent.
1:13:04.120 The other way of putting the second law is known as their classiest statement of the second
1:13:09.040 law, which goes like this, the change in entropy equals the heat supplied reversibly divided
1:13:15.920 Basically, entropy is disorder, a gas has got high entropy, a solid being all ordered
1:13:22.320 and crystal-like has low entropy, all the particles are there lined up like soldiers standing
1:13:28.400 A change in entropy is a ratio of energy and jewels of heat transferred to the temperature
1:13:34.920 So the units of entropy are jewels per Kelvin.
1:13:37.680 And so yet another way of putting the second law is that the entropy of the universe increases
1:13:44.320 in the course of any spontaneous change, and this is what Paul Davies makes a big deal
1:13:51.440 about and what many physicists make a big deal about, you've got this, irrevocable increase
1:14:00.400 In other words, the system and the surroundings is what we mean by the universe, so whatever
1:14:04.120 change is going on and the rest of the universe, so that's the universe.
1:14:10.920 The system, all the surroundings can have a decrease, a local decrease in entropy.
1:14:16.280 For example, biology is a highly ordered thing, a biological system is a highly ordered,
1:14:21.880 and so this leads these misconceptions where people try to, I don't think they do it so
1:14:26.280 much anymore, but creationists, intelligent designers, just say things like, well, we've
1:14:31.360 got this law of thermodynamics that says that entropy must always increase, but biology
1:14:37.840 is a thing that violates that, and after all, biology is a decrease in entropy, therefore
1:14:43.960 No, of course not, okay, you can have a local decrease in entropy.
1:14:50.880 It cools things and you have a decrease in entropy inside the fridge, but it is expelling
1:14:56.080 entropy and increase of entropy to the rest of the universe, same to with biology.
1:15:00.480 The sun is shining on the earth and heating the earth and causing all sorts of increases
1:15:06.280 in entropy everywhere else, even if locally with the knowledge being created inside of
1:15:13.840 organisms, you have a decrease in entropy there in the organism, but the organism is causing
1:15:19.800 an increase of entropy in the rest of the universe.
1:15:22.480 We can go right down that rabbit hole with entropy.
1:15:24.760 It's all very interesting and subtle and so forth, but this is already a super long episode.
1:15:30.280 I might leave the technical discussion of disorder, exactly, but it's probably worth
1:15:36.560 It is worth going over, at least a more precise definition of entropy or understanding
1:15:41.760 of entropy, as I like to say, rather than definition, in terms of what's happening with
1:15:47.720 So let's consider particles at a fixed temperature.
1:15:51.040 And remember what a particular temperature means.
1:15:53.840 It means that the particles have a distribution of energies and that distribution is called
1:15:59.360 the Boltzmann distribution of the energy of the particles over the allowed energy levels
1:16:09.040 For a given volume of space, they're different to other volumes of space.
1:16:13.760 There are fewer permitted states or energies that some collection of particles can have
1:16:20.960 You can imagine a microscopic box like this one, and in that microscopic box, only
1:16:26.320 certain energies are allowed, according to the laws of quantum physics, that's just
1:16:34.800 You can't just have any energy that you like.
1:16:37.040 You can have this energy, all that energy, all that energy, but not just any energy in
1:16:41.640 So let's say we have this tiny, tiny box, let's say this is the scale.
1:16:46.480 And these are more particles in this box at some temperature.
1:16:49.320 And let's say that's 100 Kelvin, tiny little box there.
1:16:52.640 And there's your particles and they're the energies that they have.
1:16:57.280 This is the ground state, so to speak, and on the minimum energy, although out to this
1:17:04.680 One, two, three, four, five, six energy levels here, permitted inside of that box, at that
1:17:11.880 Now, the thing is, that volume of space accommodates those certain energy levels.
1:17:17.600 They are the energy levels permitted by particles in that volume.
1:17:21.000 But what if we increase the volume of the box by widening it, keeping the temperature the
1:17:27.120 Well, this is what happens to the energy levels.
1:17:32.080 So now, instead of only having six energy levels, we have one, two, three, four, five,
1:17:37.040 six, seven, eight, nine, ten, we can have more.
1:17:40.160 And so the particles distribute themselves across more energy levels.
1:17:44.080 The energy levels get closer together, more permitted in this box.
1:17:50.520 So the Boltzmann distribution spans more energy levels at the same temperature.
1:17:58.920 What is ordered simply by virtue of the fact there are more energy levels permitted in
1:18:04.840 Or another way of putting this is to say if we were to randomly select a particle from
1:18:09.120 the first box with the aim of getting it from the first level, the chance of getting
1:18:13.400 our random particle from that first level in the second box is lower in comparison, because
1:18:20.640 As Atkins puts it, quote, the disorder and the entropy increase as gas occupiers are
1:18:25.880 greater volume at the same temperature, end quote, which is right for people to consider
1:18:34.000 Now you'll let them out into the playground, disordered, just the completion of the technical
1:18:38.640 stuff, the formula normally taught for entropy is this one, which is the entropy s is
1:18:49.600 He cays the Boltmann constant just as before, and it appears in our definition of temperature
1:18:55.520 But here w is not the work, but it's the weight of arrangement of particles.
1:19:01.600 The ways the particles can be arranged to achieve some amount of energy.
1:19:05.600 But anyways, that's the formula for total entropy.
1:19:11.840 And we're going to talk about that again in the next episode, and a little bit more before
1:19:15.560 the end of this episode, but we really have to go on and just mention without going into
1:19:20.000 too much detail, the third law of thermodynamics and the third law of thermodynamics and
1:19:24.040 its states that the entropy of a system approaches a constant value as the temperature of
1:19:33.240 So different substances, different systems will have different minimum entropies, but that
1:19:39.040 great amount of order will be achieved at absolute zero.
1:19:43.280 So you'll end up having a constant value at the minimum possible temperature, but I'm
1:19:48.720 not going to get hooked on the third law of thermodynamics.
1:19:51.640 So before I finish up today and well done for persevering, I have to go, as I promised
1:19:56.080 to Paul Davies' latest book and the chapter, all about times puzzling arrow.
1:20:03.920 Davies writes in his latest book, quote, I'm not reading the entire chapter just a part of it,
1:20:11.560 The issue with times arrow is this, imagine taking a movie of an everyday incident and
1:20:16.400 playing it in reverse to an audience, everybody laughs because it looks so preposterous.
1:20:21.560 People walking backwards, rivers flowing uphill, sand castles washed into shape by retreating
1:20:34.600 Open a new pack of cards, the manufacturers arrange them in numerical order by suit, shuffle
1:20:42.600 If a magician shuffled a pack of jumbled cards and gave them to you in numerical order,
1:20:47.160 you'd know you were being duped while it's not impossible for jumbled cards to be randomly
1:20:55.600 The arrow of time here is clear, random disruption turns order into disorder.
1:21:00.880 Scientists zeroed in on this basic property in the middle of the 19th century.
1:21:04.240 The Austrian physicist, Ludwig Boltzmann, considered how gas molecules rush around randomly
1:21:09.160 banging into each other and spreading heat energy around.
1:21:11.920 He analyzed this natural shuffling mathematically and identified something called entropy,
1:21:16.720 a precisely defined quantity that measures the degree of disorder in the gas.
1:21:20.640 Then he used Newton's laws of mechanics plus an averaging assumption to prove that entropy
1:21:27.400 The rise and rise of entropy is one expression of the so-called second law of thermodynamics,
1:21:32.360 perhaps the most inclusive law in all of physics.
1:21:35.640 Because what's true of gases is true of everything.
1:21:38.160 All systems have a natural tendency to grow messier, to degenerate and decay, just skipping
1:21:43.800 I'm picking it up where he writes, understanding the cosmic implications of all this, the
1:21:47.120 British physicist, Lord Kelvin, delivered a lecture in 1852, famous for it has to be the
1:21:52.880 most depressing prediction in the history of science.
1:21:55.800 The entire universe, claimed Kelvin, is dying, slowly choking on its own entropy.
1:22:01.400 Gradually, inexorably, cosmos is turning into chaos, and then babies goes on to say.
1:22:06.760 If the relentless march of disorder defines the arrow of time, then the universe must
1:22:13.040 Indeed, it was, as I have been at pains to point out, the universe that emerged from
1:22:17.480 the Big Bang was astonishingly, bafflingly, extremely highly ordered.
1:22:22.240 Had it been exactly ordered, the arrow of time would have stalled, because perfection
1:22:27.880 It would have been a case of blandness forever.
1:22:31.200 Gravity would have nothing to get its teeth into.
1:22:33.360 But of course, the nascent universe wasn't 100% perfect.
1:22:37.240 There were those ever-slides, wispy spludges found by Coby, I mean, 0.01% variation in temperature
1:22:44.200 far below what the human senses would register, posing as my reflection.
1:22:48.480 Coby is the cosmic microwave background explorer.
1:22:51.240 It is the satellite, here it is, it looks like this.
1:22:54.680 First credited with detecting these so-called anisotropies in the cosmic microwave background.
1:23:02.000 These anisotropies are fluctuations in the temperature.
1:23:07.160 Obviously, we thought that the cosmic microwave background, the heat left over from the
1:23:11.000 Big Bang, was extremely uniform, 2.7 Kelvin.
1:23:18.280 But uniform in all directions, so exactly 2.7 Kelvin, everywhere that you looked, unless
1:23:23.400 you take extremely precise measurements, with a microwave detecting satellite far above
1:23:31.480 So the first images that came back looked kind of like this.
1:23:34.680 This is an anisotropy, it's a dipole, in fact.
1:23:38.920 Here it's slightly warmer, here it's slightly cooler.
1:23:41.600 Now the reason for this, it's an artifact, it's an artifact of the fact that we are moving
1:23:47.480 In fact, the galaxy is moving through space, so that can be subtracted from the image,
1:23:54.960 And that red band through the middle there, well, that should look familiar, that's
1:23:58.200 the Milky Way, and that can be subtracted out of the image as well, using image processing.
1:24:04.440 And finally, you end up with the image that everyone was after, which is this, the first
1:24:08.880 image of the cosmic microwave background, showing the slightly warmer and slightly cooler
1:24:15.200 regions, the slightly cooler regions are the slightly more dense regions, which eventually
1:24:19.360 go on to condense into the matter out of which everything that we see in the universe is
1:24:26.960 So all the galaxies end up condensing out of these slightly more dense regions, and those
1:24:32.040 warmer regions are the voids in between where clusters of galaxies and so on and so forth are.
1:24:38.080 It was the first satellite that detected evidence of the cosmic microwave background radiation,
1:24:43.720 the heat left over after the big bang, the person given the Nobel Prize for Physics for
1:24:52.280 His student was his graduate student who I think was the first one to really analyze the
1:25:00.880 And then handed data to Smoot was Charlie Lionweaver, that famous physicist I often talk
1:25:06.240 about, who also works with, has worked with Paul Davies, taught me as well, he was one
1:25:13.560 So yes, I heard a lot about Kobe during and those stories about Kobe during lectures.
1:25:19.600 Anyway, continuing, spludges his talk about, spludges in the images, take a my Kobe, and
1:25:25.120 Davies goes on to write, quote, the splotches betray a minute departure from orderly perfection,
1:25:30.200 a pellet of almost imperceptible density perturbations in the primordial plasma.
1:25:35.280 Gravity set to work on the spludges, the overdense regions pulled more strongly, drawing
1:25:39.440 in on the surrounding material and amplifying the density contrast, generating large scale
1:25:44.280 complexity, clusters of galaxies churning clouds of gas and meandering stars, clumping,
1:25:49.680 is gravity's gift to cosmos, and I'm skipping apart here and I'll pick it up where Davies
1:25:55.600 concludes with, thus it is that gravity, the incubator and annihilator of habitable order,
1:26:00.760 is also the source of times pervasive arrow, the time asymmetry that distinguishes yesterday
1:26:05.760 from tomorrow, memories from anticipation birth from death can be traced back to the birth
1:26:10.680 of the universe itself, and specifically to its extraordinary degree of primordial smoothness.
1:26:17.240 But where did that smoothness come from in the first place?
1:26:19.600 Do we just accept it as an unexplained initial condition, a big fix?
1:26:24.840 One possible explanation is that an appeal to the tiny violation of time reversal symmetry
1:26:30.080 in certain hard to discern particle processes, did the very particles of the universe themselves
1:26:34.800 come with their own in-built arrow, which somehow projected itself onto the entire cosmos,
1:26:40.400 in the turret aftermath of the Big Bang, maybe, but in my view, not very likely, far and
1:26:45.360 away the most popular explanation for the smooth start to the universe is the inflationary
1:26:49.880 scenario, a burst of antigravity, propelled expansion in the first split second, creates
1:26:55.560 precisely that almost, they're not quite perfect uniformity, but that's still not the
1:27:00.120 end of the trail because the universe has to get itself into an inflationary state of
1:27:06.440 The scientific community is still very far from reaching consensus on these thorny issues,
1:27:11.000 all that can be said for certain is that one of the most fundamental properties of the
1:27:14.280 physical world that tomorrow is different from today, still lacks a full explanation,
1:27:20.240 and it lies high on my own list of essential unanswered big questions.
1:27:27.920 Now, the question is, if so many other approaches to trying to understand the origins
1:27:34.520 of this second law have hitherto not borne truth, neither from quantum theory nor general
1:27:40.960 relativity nor string theory, maybe construct a theory has something to add, key, and it
1:27:48.280 That's where we will leave it today so that next time I can get straight into readings
1:27:53.440 from the book itself, actual readings from the sides of Canada, so even though this is
1:27:58.300 misleadingly titled, something to do with the science of Canada, we didn't actually
1:28:04.800 Until next time, bye-bye, oh and one thing, oh my god, personal appeal, if you'd like
1:28:10.240 to support this enterprise for, want to have another word to describe it, see my Patreon
1:28:16.960 The links are there on my website here at www.brejo.org, bye-bye.
