0:00:07 > 0:00:13How did humans acquire the power to transform the planet like this?
0:00:14 > 0:00:16Looking at the earth at night
0:00:16 > 0:00:18reveals to us just how successful we've been
0:00:18 > 0:00:21in harnessing and manipulating energy
0:00:21 > 0:00:24and how important it is to our existence.
0:00:34 > 0:00:36Energy is vital to us all.
0:00:36 > 0:00:40We use it to build the structures that surround and protect us.
0:00:40 > 0:00:44We use it to power our transport and light our homes.
0:00:44 > 0:00:48And even more crucially, energy is essential for life itself.
0:00:48 > 0:00:52Without the energy we get from the food we eat, we'd die.
0:00:52 > 0:00:54But what exactly is energy?
0:00:54 > 0:00:57And what makes it so useful to us?
0:01:02 > 0:01:04In attempting to answer these questions,
0:01:04 > 0:01:07scientists would come up with a strange set of laws
0:01:07 > 0:01:12that would link together everything, from engines, to humans, to stars.
0:01:12 > 0:01:17It turns out that energy, so crucial to our daily lives
0:01:17 > 0:01:22also helps us make sense of the entire universe.
0:01:26 > 0:01:29This film is the intriguing story
0:01:29 > 0:01:34of how we discovered the rules that drive the universe.
0:01:39 > 0:01:42It is the story of how we realised
0:01:42 > 0:01:49that all forms of energy are destined to degrade and fall apart.
0:01:53 > 0:01:57To move from order to disorder.
0:02:00 > 0:02:04It's the story of how this amazing process
0:02:04 > 0:02:06has been harnessed by the universe
0:02:06 > 0:02:09to create everything that we see around us.
0:02:47 > 0:02:49Over the course of human history,
0:02:49 > 0:02:52we've come up with all sorts of different ways
0:02:52 > 0:02:55of extracting energy from our environment.
0:02:55 > 0:02:57Everything from picking fruit,
0:02:57 > 0:03:02to burning wood, to sailing boats, to waterwheels.
0:03:02 > 0:03:06But around 300 years ago, something incredible happened.
0:03:06 > 0:03:08Humans developed machines
0:03:08 > 0:03:12that were capable of processing extraordinary amounts of energy
0:03:12 > 0:03:15to carry out previously unimaginable tasks.
0:03:15 > 0:03:19This happened thanks to many people and for many different reasons,
0:03:19 > 0:03:21but I'd like to begin this story
0:03:21 > 0:03:23with one of the most intriguing characters
0:03:23 > 0:03:25in the history of science.
0:03:25 > 0:03:29One of the first to attempt to understand energy.
0:03:45 > 0:03:51Gottfried Leibniz was a diplomat, scientist, philosopher and genius.
0:03:51 > 0:03:54He was forever trying to understand the mechanisms
0:03:54 > 0:03:56that made the universe work.
0:03:58 > 0:04:01Leibniz like several of his great contemporaries
0:04:01 > 0:04:04was absolutely convinced that the world we see around us
0:04:04 > 0:04:10is a vast machine designed by a powerful and wise person.
0:04:10 > 0:04:15And if you could understand how machines worked,
0:04:15 > 0:04:18you could therefore understand how the universe
0:04:18 > 0:04:23and the principles that had been used to make the universe worked as well.
0:04:23 > 0:04:30So there was an extremely close relationship for Leibniz
0:04:30 > 0:04:33between theology and philosophy on the one hand
0:04:33 > 0:04:35and engineering and mechanics on the other.
0:04:39 > 0:04:41It was this relationship between philosophy and engineering
0:04:41 > 0:04:46that in 1676 would lead him to investigate
0:04:46 > 0:04:50what at first sight seemed to be a very simple question.
0:04:57 > 0:04:59What happens when objects collide?
0:04:59 > 0:05:01This is was what Leibniz
0:05:01 > 0:05:04and many of his contemporaries were grappling with.
0:05:04 > 0:05:07So when these two balls bump into each other,
0:05:07 > 0:05:11the movement of one gets transferred to the other.
0:05:12 > 0:05:14It's as though something's been passed between them
0:05:14 > 0:05:18and this that Leibniz called the living force.
0:05:18 > 0:05:20He thought of it as a stuff,
0:05:20 > 0:05:26as a real physical substance that gets exchanged during collisions.
0:05:34 > 0:05:39Leibniz argued that the world is a living machine
0:05:39 > 0:05:42and that inside the machine,
0:05:42 > 0:05:47there is a quantity of living force put there by God at the Creation
0:05:47 > 0:05:49that will stay the same forever.
0:05:49 > 0:05:54So the amount of living force in the world will be conserved.
0:05:54 > 0:05:56The puzzle was to define it.
0:06:01 > 0:06:05Leibnitz would soon find a simple mathematical way
0:06:05 > 0:06:08to describe the living force.
0:06:08 > 0:06:10But he would also see something else.
0:06:10 > 0:06:12EXPLOSION
0:06:12 > 0:06:17He realised that in gunpowder, fire and steam,
0:06:17 > 0:06:22his living force was being released in violent and powerful ways.
0:06:25 > 0:06:26EXPLOSION
0:06:35 > 0:06:38If this could be harnessed,
0:06:38 > 0:06:41it could give humankind unimaginable power.
0:06:51 > 0:06:53Leibniz would soon become fascinated
0:06:53 > 0:06:56with ways of capturing the living force.
0:07:03 > 0:07:07A prolific letter writer, Leibniz struck up correspondence
0:07:07 > 0:07:10with a young French scientist called Denis Papin.
0:07:15 > 0:07:18As they corresponded, Leibniz and Papin realised
0:07:18 > 0:07:22the living force released in certain situations
0:07:22 > 0:07:24could indeed be harnessed.
0:07:25 > 0:07:30Heat could be converted in to some form of useful action.
0:07:36 > 0:07:40But how far could this idea be taken?
0:07:40 > 0:07:42Papin was in no doubt.
0:07:42 > 0:07:45This is an extract from his letter to Leibniz...
0:07:48 > 0:07:50"I can assure you that the more I go forward,
0:07:50 > 0:07:53"the more I find reason to think highly of this invention,
0:07:53 > 0:07:59"which in theory, may augment the powers of man to infinity.
0:07:59 > 0:08:02"But in practice, I believe I can say without exaggeration,
0:08:02 > 0:08:04"that one man by this means
0:08:04 > 0:08:08"will be able to do as much as 100 others can do without it."
0:08:11 > 0:08:14Now, you might expect me at this point to tell you
0:08:14 > 0:08:18that Leibniz and Papin changed the world forever.
0:08:18 > 0:08:19Well, they hadn't.
0:08:19 > 0:08:22Their ideas had been profound and far reaching, yes,
0:08:22 > 0:08:25but they hadn't really moved things forward.
0:08:25 > 0:08:29For that, you need something much more tangible.
0:08:29 > 0:08:31You need innovation, industry.
0:08:31 > 0:08:34You need countless skilled workers and craftsmen
0:08:34 > 0:08:37who are going to apply these ideas,
0:08:37 > 0:08:40to experiment with them in novel and new ways.
0:08:40 > 0:08:43Well, in the century that followed Leibniz and Papin,
0:08:43 > 0:08:47this would take place in the most dramatic way imaginable.
0:08:56 > 0:09:01150 years after Leibniz and Papin's discussions,
0:09:01 > 0:09:05the living force had been harnessed in spectacular ways.
0:09:06 > 0:09:09The machines they dreamed of had become a reality.
0:09:09 > 0:09:15Steam engines were now the cutting edge of 19th century technology.
0:09:24 > 0:09:26If you look at steps in civilisation,
0:09:26 > 0:09:32then one great step was the steam engine, because it replaced muscle,
0:09:32 > 0:09:35animal muscle, including our muscle, by steam power.
0:09:35 > 0:09:38And the steam power was effectively limitless
0:09:38 > 0:09:43and hugely important to doing almost unimaginable things.
0:09:51 > 0:09:56But steam technology would do more than just transform human society.
0:09:56 > 0:09:59It would uncover the truth about what Leibniz had called
0:09:59 > 0:10:03the living force and reveal new insights
0:10:03 > 0:10:05about the workings of our universe.
0:10:10 > 0:10:14This is Crossness in south-east London.
0:10:14 > 0:10:18It's an incredible industrial cathedral,
0:10:18 > 0:10:23home to some of the most impressive Victorian steam engines ever built.
0:10:32 > 0:10:39Constructed in 1854, Crossness houses four huge engines
0:10:39 > 0:10:44that once required 5,000 tonnes of coal each year
0:10:44 > 0:10:46to drive their 47-tonne beams.
0:11:02 > 0:11:07Everything about this place seems to have been built to impress.
0:11:07 > 0:11:09From the lavish ironwork -
0:11:09 > 0:11:14the grand pillars like something out of a Greek or Roman temple.
0:11:14 > 0:11:16It's the kind of effort you'd think would be lavished
0:11:16 > 0:11:20on a luxury ocean liner for the rich and famous.
0:11:20 > 0:11:24And yet this place was built to process sewage.
0:11:24 > 0:11:29Although only a few workers and engineers would see inside it,
0:11:29 > 0:11:30steam had become
0:11:30 > 0:11:35such a vital part of Britain's power and economic prosperity
0:11:35 > 0:11:39that it was afforded almost religious respect.
0:11:53 > 0:11:56But for all the great success and immense power
0:11:56 > 0:11:59that engines were bestowing on their creators
0:11:59 > 0:12:03there was still a great deal of confusion and mystery
0:12:03 > 0:12:06surrounding exactly how and why they worked.
0:12:06 > 0:12:11In particular questions like, "How efficient could they be made?"
0:12:11 > 0:12:13"Were there limits to their power?"
0:12:13 > 0:12:15Ultimately, people wanted to know
0:12:15 > 0:12:19just what might it be possible to achieve with steam.
0:12:30 > 0:12:34The reason these questions persisted was simple almost no-one
0:12:34 > 0:12:38had understood the fundamental nature of the steam engine.
0:12:38 > 0:12:42Very few were aware of the cosmic principle which underpinned it.
0:12:46 > 0:12:51These great lumbering machines we think of as the early steam engines
0:12:51 > 0:12:54actually were the seed of understanding
0:12:54 > 0:12:57of everything that goes on in the universe.
0:13:01 > 0:13:04As unlikely as it sounds,
0:13:04 > 0:13:09steam engines held within them the secrets of the cosmos.
0:13:33 > 0:13:36This is the Chateau de Vincennes in Paris.
0:13:36 > 0:13:41Events here would motivate one man's journey to uncover the cosmic truth
0:13:41 > 0:13:46about the steam engine, and help to create a new science.
0:13:46 > 0:13:50The science of heat and motion. Thermo-dynamics.
0:14:05 > 0:14:08In March 1814, during the Napoleonic wars,
0:14:08 > 0:14:12when Napoleon and his armies where fighting elsewhere,
0:14:12 > 0:14:15Paris itself came under sustained attack
0:14:15 > 0:14:19from the combined forces of Russia, Prussia and Austria.
0:14:19 > 0:14:23Citizens were deployed around key locations to protect them.
0:14:23 > 0:14:29This chateau was being defended by a group of inexperienced students
0:14:29 > 0:14:33who were forced to retreat under sustained artillery fire.
0:14:33 > 0:14:37One of them was a brilliant young scientist and soldier.
0:14:37 > 0:14:41His name was Nicolas Leonard Sadi Carnot
0:14:41 > 0:14:44and the humiliation he felt personally
0:14:44 > 0:14:47would drive him and motivate him
0:14:47 > 0:14:52to uncover a profound insight into how all engines work.
0:14:56 > 0:14:59Carnot came from a highly-respected military family.
0:14:59 > 0:15:03After the French defeat here and elsewhere around Europe,
0:15:03 > 0:15:07he became determined to reclaim French pride.
0:15:13 > 0:15:17What really bothered Carnot was the technological superiority
0:15:17 > 0:15:19that France's enemies seemed to possess.
0:15:19 > 0:15:24And Britain, in particular, had this huge advantage
0:15:24 > 0:15:27both militarily and economically
0:15:27 > 0:15:30because of its mastery of steam power.
0:15:30 > 0:15:36So Carnot vowed to really understand how steam engines work
0:15:36 > 0:15:40and use that knowledge for the benefit of France.
0:15:42 > 0:15:46He says absolutely explicitly that if you could take away
0:15:46 > 0:15:48steam engines from Britain
0:15:48 > 0:15:51then the British Empire would collapse.
0:15:51 > 0:15:55And he's writing in the wake of French military defeat
0:15:55 > 0:15:58and he proposes to analyse,
0:15:58 > 0:16:02literally, the source of British power
0:16:02 > 0:16:07by analysing the way in which fire and heat engines work.
0:16:10 > 0:16:12Living on half-pay with his brother Hippolyte
0:16:12 > 0:16:15in a small apartment in Paris,
0:16:15 > 0:16:18in 1824 Carnot wrote the now legendary
0:16:18 > 0:16:22Reflections On The Motive Power Of Fire.
0:16:22 > 0:16:24In just under 60 pages,
0:16:24 > 0:16:28he developed and abstracted the fundamental way
0:16:28 > 0:16:30in which all heat engines work.
0:16:30 > 0:16:32Carnot saw that all heat engines
0:16:32 > 0:16:37comprised of a hot source in cooler surroundings.
0:16:38 > 0:16:42Now, Carnot believed heat was some kind of substance
0:16:42 > 0:16:47that would flow like water from the hot to the cool.
0:16:47 > 0:16:50And just like water falling from a height
0:16:50 > 0:16:53the flow of heat could be tapped to do useful work.
0:16:58 > 0:17:00Carnot's crucial insight
0:17:00 > 0:17:03was to show that to make any heat engine more efficient
0:17:03 > 0:17:08all you had to do was to increase the difference in temperature
0:17:08 > 0:17:11between the heat source and cooler surroundings.
0:17:15 > 0:17:20This idea has guided engineers for 200 years.
0:17:22 > 0:17:25Ultimately, a car engine is more efficient than a steam engine
0:17:25 > 0:17:29because it runs at a much hotter temperature.
0:17:29 > 0:17:32Jet engines are more efficient still
0:17:32 > 0:17:35thanks to the incredible temperatures they can run at.
0:17:38 > 0:17:40Carnot had revealed
0:17:40 > 0:17:44that heat engines weren't just a clever invention.
0:17:44 > 0:17:48They were tapping into a deeper property of nature.
0:17:49 > 0:17:53They were exploiting the flow of energy
0:17:53 > 0:17:55between hot and cold.
0:18:00 > 0:18:07Carnot had glimpsed the true nature of heat engines and, in the process,
0:18:07 > 0:18:09begun a new branch of science.
0:18:09 > 0:18:14But he would never see the impact his idea would have on the world.
0:18:16 > 0:18:20In 1832, a cholera epidemic spread through Paris.
0:18:20 > 0:18:25It was so severe, it would kill almost 19,000 people.
0:18:25 > 0:18:28Now, back then, there was no real scientific understanding
0:18:28 > 0:18:31of how the disease spread, so it must have been terrifying.
0:18:31 > 0:18:34Carnot undaunted by the risks,
0:18:34 > 0:18:38decided to study and document the spread of the disease.
0:18:38 > 0:18:44But, unfortunately, he contracted it himself and was dead a day later.
0:18:44 > 0:18:46He was just 36 years old.
0:18:46 > 0:18:50A lot of his precious scientific papers were burned
0:18:50 > 0:18:52to stop the spread of the contagion
0:18:52 > 0:18:55and his ideas fell into temporary obscurity.
0:18:55 > 0:19:00It seems the world wasn't quite ready for Carnot.
0:19:04 > 0:19:07Carnot had made the first great contribution
0:19:07 > 0:19:11to the science of thermodynamics.
0:19:11 > 0:19:16But as the 19th century progressed the study of heat, motion and energy
0:19:16 > 0:19:19began to grip the wider scientific community.
0:19:19 > 0:19:24Soon, it was realised these ideas could do much more
0:19:24 > 0:19:26than simply explain how heat engines worked.
0:19:26 > 0:19:31Just as Leibniz had suspected with his notion of living force,
0:19:31 > 0:19:36these ideas were applicable on a much grander scale.
0:19:49 > 0:19:51By the mid 19th century,
0:19:51 > 0:19:54scientists and engineers had worked out very precisely
0:19:54 > 0:19:58how different forms of energy relate to each other.
0:19:58 > 0:20:02They measured how much of a particular kind of energy is needed
0:20:02 > 0:20:06to make a certain amount of a different kind.
0:20:06 > 0:20:08Let me give you an example.
0:20:08 > 0:20:14The amount of energy needed to heat 30ml of water
0:20:14 > 0:20:16by one degree centigrade
0:20:16 > 0:20:19is the same as the amount of energy needed
0:20:19 > 0:20:24to lift this 12.5kg weight by one metre.
0:20:26 > 0:20:29The deeper point here that people realised
0:20:29 > 0:20:34was that although mechanical work and heat may seem very different,
0:20:34 > 0:20:40they are, in fact, both facets of the same thing - energy.
0:20:42 > 0:20:48This idea would come to be known as the first law of thermodynamics.
0:20:48 > 0:20:53The first law reveals that energy is never created or destroyed.
0:20:53 > 0:20:57It just changes from one form to another.
0:20:59 > 0:21:0319th Century scientists realised this meant the total energy
0:21:03 > 0:21:07of the entire universe is actually fixed.
0:21:07 > 0:21:11Amazingly, there's a set amount of energy
0:21:11 > 0:21:15that just changes into many different forms.
0:21:15 > 0:21:20So, in a steam engine, energy isn't created -
0:21:20 > 0:21:24it's just changed from heat into mechanical work.
0:21:31 > 0:21:36But impressive though the first law is, it begged an enormous question -
0:21:36 > 0:21:42what exactly is going on when one form of energy changes into another?
0:21:42 > 0:21:44In fact, why does it do it at all?
0:21:51 > 0:21:58The answer would, in part, be found by German scientist Rudolf Clausius.
0:21:58 > 0:22:01And it would form the basis what would become known
0:22:01 > 0:22:03as the second law of thermodynamics.
0:22:09 > 0:22:14Rudolf Clausius was a brilliant German physics student
0:22:14 > 0:22:16from Pomerania
0:22:16 > 0:22:18who studied in Berlin
0:22:18 > 0:22:22and at a ridiculously young age became a very brilliant professor
0:22:22 > 0:22:26in Berlin and then in Zurich
0:22:26 > 0:22:30at the new technology university set up there in Switzerland.
0:22:30 > 0:22:36In the 1850s and 60s, Clausius offered what was really
0:22:36 > 0:22:41the first, coherent, full-blown, mathematical analysis
0:22:41 > 0:22:44of how thermodynamics works.
0:22:47 > 0:22:50Clausius realised that not only was there
0:22:50 > 0:22:52a fixed amount of energy in the universe
0:22:52 > 0:22:57but that the energy seemed to be following a very strict rule.
0:22:59 > 0:23:02Put simply, energy in the form of heat
0:23:02 > 0:23:05always moved in one particular direction.
0:23:09 > 0:23:10This insight of his is
0:23:10 > 0:23:15in fact one of the most important ideas in the whole of science.
0:23:15 > 0:23:17As Clausius put it,
0:23:17 > 0:23:22"Heat cannot of itself pass from a colder to a hotter body".
0:23:22 > 0:23:24This is a very intuitive idea.
0:23:24 > 0:23:29If left alone, this hot mug of tea will always cool down.
0:23:29 > 0:23:33What this means is that heat will pass from the hot mug
0:23:33 > 0:23:39say to my hand and then again from my hand to my chest.
0:23:46 > 0:23:51This might seem completely obvious but it was a crucial insight.
0:23:53 > 0:23:58The flow of heat was a one-way process that seemed to be built
0:23:58 > 0:24:03very fundamentally into the workings of the entire universe.
0:24:07 > 0:24:10Of course, objects can get hotter
0:24:10 > 0:24:14but you always need to do something to them to make this happen.
0:24:17 > 0:24:22Left alone, energy seems to always go from being concentrated
0:24:22 > 0:24:24to being dispersed.
0:24:34 > 0:24:38One of my favourite statements in science was made
0:24:38 > 0:24:41by the biochemist called Albert St George who said that,
0:24:41 > 0:24:45"Science is all about seeing what everyone else has seen,
0:24:45 > 0:24:48"but thinking what no-one else has thought."
0:24:48 > 0:24:55And he, Rudolf Clausius, looked at the everyday world
0:24:55 > 0:24:57and saw what everyone else had seen,
0:24:57 > 0:25:03that heat does not flow spontaneously from a cold body to a hot body.
0:25:03 > 0:25:05It always goes the other way.
0:25:05 > 0:25:09But he didn't just say, "Ah, I see that."
0:25:09 > 0:25:11He actually sat down and thought about it.
0:25:19 > 0:25:22Clausius brought together all these ideas about how energy
0:25:22 > 0:25:26is transferred and put them into mathematical context.
0:25:26 > 0:25:29It could be summarised by this equation.
0:25:47 > 0:25:52Now, what Clausius did was introduce a new quantity he called entropy.
0:25:52 > 0:25:54This letter S.
0:25:54 > 0:25:58Basically, what it's saying in the context of this equation
0:25:58 > 0:26:02is that as heat is transferred from hotter to colder bodies,
0:26:02 > 0:26:05entropy always increases.
0:26:11 > 0:26:17Entropy seemed to be a measure of how heat dissipates or spreads out.
0:26:17 > 0:26:22As hot things cool, their entropy increases.
0:26:22 > 0:26:26It appeared to Clausius that in any isolated system
0:26:26 > 0:26:29this process would be irreversible.
0:26:39 > 0:26:42Clausius was so confident about his mathematics
0:26:42 > 0:26:46that he figured out that this irreversible process
0:26:46 > 0:26:49was going on out there in the wider cosmos.
0:26:49 > 0:26:53He speculated that the entropy of the entire universe
0:26:53 > 0:26:55had to be increasing toward a maximum
0:26:55 > 0:26:59and there was nothing we could do to avoid this.
0:26:59 > 0:27:04This idea became known as the second law of thermodynamics
0:27:04 > 0:27:07and it turned out to be stranger, and more beautiful,
0:27:07 > 0:27:12more universal than anything that Clausius could have imagined.
0:27:21 > 0:27:26The second law of thermodynamics seemed to say that all things
0:27:26 > 0:27:30that gave off heat were, in some way, connected together.
0:27:33 > 0:27:38All things that gave off heat were part of an irreversible process
0:27:38 > 0:27:40that was happening everywhere.
0:27:41 > 0:27:45A process of spreading out and dispersing.
0:27:46 > 0:27:49A process of increasing entropy.
0:27:52 > 0:27:57It seemed that, somehow, the universe shared the same fate
0:27:57 > 0:27:59as a cup of tea.
0:28:01 > 0:28:05The wonderful thing about the Victorian scientists
0:28:05 > 0:28:08is that they could make these great leaps
0:28:08 > 0:28:13and they could see that their study of a thermometer in a beaker
0:28:13 > 0:28:17actually could be transferred... could be extrapolated,
0:28:17 > 0:28:20could be enlarged to encompass the whole universe.
0:28:39 > 0:28:42Despite the successes of thermodynamics,
0:28:42 > 0:28:44in the middle of the 19th century,
0:28:44 > 0:28:47there was great debate and confusion about the subject.
0:28:47 > 0:28:52What exactly was this strange thing called entropy
0:28:52 > 0:28:53and why was it always increasing?
0:28:55 > 0:28:59Answering this question would take an incredible intellectual leap
0:28:59 > 0:29:03but it would end up revealing the truth about energy
0:29:03 > 0:29:06and the many forms of order and disorder
0:29:06 > 0:29:08we see in the universe around us.
0:29:12 > 0:29:17Many scientists would tackle the mysterious concept of entropy.
0:29:17 > 0:29:21But one more than any other would shed light on the truth.
0:29:21 > 0:29:23He'd show what entropy really was
0:29:23 > 0:29:27and why, over time, it always must increase.
0:29:27 > 0:29:30His name was Ludwig Boltzmann
0:29:30 > 0:29:34and he was one science's true revolutionaries.
0:29:45 > 0:29:48Boltzmann had been born in Vienna in 1844.
0:29:48 > 0:29:53It was a world of scientific and cultural certainty.
0:29:53 > 0:29:54But Boltzmann took little notice
0:29:54 > 0:29:57of the entrenched beliefs of his contemporaries.
0:29:57 > 0:29:59To him, the physical world
0:29:59 > 0:30:03was something best explored with an open mind.
0:30:05 > 0:30:09Boltzmann wasn't your stereotypical scientist.
0:30:09 > 0:30:12In fact, he had the kind of temperament
0:30:12 > 0:30:16most people might associate with great artists.
0:30:16 > 0:30:19He was ruthlessly logical and analytical, yes,
0:30:19 > 0:30:24but while working, he'd go through periods of intense emotion
0:30:24 > 0:30:27followed by terrible depressions
0:30:27 > 0:30:30which would leave him completely unable to think clearly.
0:30:36 > 0:30:39He had terrible
0:30:39 > 0:30:42mental crises and breakdowns
0:30:42 > 0:30:48in which he really thought that the world was coming apart at the seams
0:30:48 > 0:30:50and yet these were also accompanied
0:30:50 > 0:30:55by some of the most profound insights into the nature of our world.
0:30:56 > 0:31:00Outside of mathematics, Boltzmann was passionate about music
0:31:00 > 0:31:06and was captivated by the grand and dramatic operas of Wagner
0:31:06 > 0:31:08and the raw emotion of Beethoven.
0:31:10 > 0:31:12He was a brilliant pianist
0:31:12 > 0:31:17and could lose himself for hours in the works of his favourite composers
0:31:17 > 0:31:21just as he could lose himself in deep mathematical theories.
0:31:21 > 0:31:24MUSIC: Beethoven's 5th Symphony - First Movement.
0:31:29 > 0:31:33Boltzmann was a scientist guided by his emotions and instinct
0:31:33 > 0:31:37and also by his belief in the ability of mathematics
0:31:37 > 0:31:39to unlock the secrets of nature.
0:31:39 > 0:31:42It was these traits that would lead him to become
0:31:42 > 0:31:47one of the champions of a shocking and controversial new theory.
0:31:47 > 0:31:51One that would describe reality at the very smallest scales.
0:31:51 > 0:31:55Far smaller than anything we could see with the naked eye.
0:31:56 > 0:32:01During the second half of the 19th century, a small group of scientists
0:32:01 > 0:32:05began speculating that, at the smallest scales,
0:32:05 > 0:32:08the universe might operate very differently
0:32:08 > 0:32:10to our everyday experiences.
0:32:15 > 0:32:20If you could look close enough, it seemed possible that the universe
0:32:20 > 0:32:25might be made of tiny, hard particles, in constant motion.
0:32:38 > 0:32:40Viewed in terms of atoms
0:32:40 > 0:32:44heat would suddenly become a much less mysterious concept.
0:32:44 > 0:32:47Boltzmann and others saw that if an object was hot
0:32:47 > 0:32:51it simply meant that its atoms were moving about more rapidly.
0:32:56 > 0:33:00Viewing the world as atoms seemed to be an immensely powerful idea.
0:33:03 > 0:33:05But this picture of the universe
0:33:05 > 0:33:08had one seemingly insurmountable problem.
0:33:11 > 0:33:14How could trillions and trillions of atoms,
0:33:14 > 0:33:18even in a tiny volume of gas, ever be studied?
0:33:18 > 0:33:20How could we come up with mathematical equations
0:33:20 > 0:33:22to describe all of this?
0:33:22 > 0:33:26After all, atoms are constantly bumping into each other,
0:33:26 > 0:33:30changing direction and speed, and there are just so many of them.
0:33:30 > 0:33:33It seemed almost an impossible problem.
0:33:34 > 0:33:37But then Boltzmann saw there was a way.
0:33:45 > 0:33:48Boltzmann saw more clearly than anyone
0:33:48 > 0:33:52that for physics to explain this new strata of reality
0:33:52 > 0:33:55it had to abandon certainty.
0:34:04 > 0:34:08Instead of trying to understand and measure the exact movements
0:34:08 > 0:34:14of each individual atom, Boltzmann saw you could build working theories
0:34:14 > 0:34:18simply by using the probability that atoms would be travelling
0:34:18 > 0:34:21at certain speeds and in certain directions.
0:34:29 > 0:34:33Boltzmann had transported himself inside matter.
0:34:36 > 0:34:39He had imagined a world beneath our everyday reality
0:34:39 > 0:34:42and found a mathematics to describe it.
0:34:44 > 0:34:48It would be here at this scale that Boltzmann would one day manage
0:34:48 > 0:34:52to unlock energy's deepest secret -
0:34:52 > 0:34:55despite the widespread hostility to his theories.
0:35:02 > 0:35:06Boltzmann's ideas were highly, highly controversial.
0:35:06 > 0:35:10And you have to remember that today we take atoms for granted.
0:35:10 > 0:35:15But the reason we take atoms for granted is precisely because
0:35:15 > 0:35:19Boltzmann's mathematics married up so beautifully with experiments.
0:35:48 > 0:35:51One of the most surprising aspects of this story is that
0:35:51 > 0:35:55many of Boltzmann's contemporaries viewed his ideas about atoms
0:35:55 > 0:35:57with intense hostility.
0:36:02 > 0:36:04Today the existence of atoms,
0:36:04 > 0:36:07the idea that all matter is composed of tiny particles,
0:36:07 > 0:36:10is something we accept without question.
0:36:10 > 0:36:11But back in Boltzmann's time
0:36:11 > 0:36:16there were notable, eminent physicists who just didn't buy it.
0:36:16 > 0:36:17Why would they?
0:36:17 > 0:36:21No-one had ever seen an atom and probably no-one ever would.
0:36:21 > 0:36:23How could these particles be considered as real?
0:36:34 > 0:36:38After one of Boltzmann's lectures on atomic theory in Vienna
0:36:38 > 0:36:42the great Austrian physicist Ernst Mach stood up
0:36:42 > 0:36:46and said simply, "I don't believe that atoms exist!"
0:36:46 > 0:36:49It was both cutting and dismissive.
0:36:49 > 0:36:53And for such a comment to come from a highly regarded scientist
0:36:53 > 0:36:56like Ernst Mach, it would have been doubly hurtful.
0:37:04 > 0:37:07They argued that, "No, atoms don't exist."
0:37:07 > 0:37:09They're names, labels,
0:37:09 > 0:37:13convenient fictions, calculating devices.
0:37:13 > 0:37:16They don't really exist. We can't observe them.
0:37:16 > 0:37:18No-one's ever seen one.
0:37:18 > 0:37:23And for that reason, so Boltzmann's critics said, he was a fantasist.
0:37:27 > 0:37:29But Boltzmann was right.
0:37:29 > 0:37:33He had peered deeper into reality than anyone else had dared,
0:37:33 > 0:37:37and seen that the universe could be built from the atomic hypothesis
0:37:37 > 0:37:41and understood through the mathematics of probability.
0:37:41 > 0:37:45The foundations and certainty of 19th century science
0:37:45 > 0:37:47were beginning to crumble.
0:37:55 > 0:37:59As Boltzmann stared into his brave new world of atoms
0:37:59 > 0:38:05he began to realise his new vision of the universe contained within it
0:38:05 > 0:38:10an explanation to one of the biggest mysteries in science.
0:38:10 > 0:38:15Boltzmann saw atoms could reveal why the second law of thermodynamics
0:38:15 > 0:38:20was true, why nature was engaged in an irreversible process.
0:38:20 > 0:38:24Atoms had the power to reveal what entropy really was
0:38:24 > 0:38:28and why it must always increase.
0:38:32 > 0:38:36Boltzmann understood that all objects these walls,
0:38:36 > 0:38:41you, me, the air in this room, are made up of much tinier constituents.
0:38:41 > 0:38:45Basically, everything we see is an assembly
0:38:45 > 0:38:48of trillions and trillions of atoms and molecules.
0:38:48 > 0:38:53And this was the key to his insight about entropy and the second law.
0:38:59 > 0:39:02Boltzmann saw what Clausius could not.
0:39:02 > 0:39:07The real reason why a hot object left alone will always cool down.
0:39:08 > 0:39:10Imagine a lump of hot metal.
0:39:12 > 0:39:14The atoms inside it are jostling around.
0:39:16 > 0:39:20But as they jostle, the atoms at the edge of the object
0:39:20 > 0:39:24transfer some of their energy to the atoms on the surface of the table.
0:39:28 > 0:39:32These atoms then bump into their neighbours, and in this way,
0:39:32 > 0:39:37the heat energy slowly and very naturally spreads out and disperses.
0:39:40 > 0:39:45The whole system has gone from being in a special, ordered state
0:39:45 > 0:39:48with all the energy concentrated in one place,
0:39:48 > 0:39:50to a disordered state
0:39:50 > 0:39:56where the same amount of energy is distributed amongst many more atoms.
0:39:56 > 0:39:58Boltzmann's brilliant mind
0:39:58 > 0:40:02saw this whole process could be described mathematically.
0:40:04 > 0:40:07Boltzmann's great contribution was that,
0:40:07 > 0:40:12although we can talk in rather sort of casual terms,
0:40:12 > 0:40:16about things getting worse, and disorder increases,
0:40:16 > 0:40:21the great contribution of Boltzmann is that he could put numbers to it.
0:40:21 > 0:40:25So he was able to derive a formula which enabled you
0:40:25 > 0:40:27to calculate the disorder of the system.
0:40:36 > 0:40:39This is Boltzmann's famous equation.
0:40:39 > 0:40:43It would be his enduring contribution to science,
0:40:43 > 0:40:46so much so, it was engraved on his tombstone in Vienna.
0:40:48 > 0:40:50What this equation means in essence
0:40:50 > 0:40:55is there are many more ways for things to be messy and disordered
0:40:55 > 0:40:58than there are for them to be tidy and ordered.
0:41:01 > 0:41:07That's why, left to itself, the universe will always get messier.
0:41:13 > 0:41:19Things will move from order to disorder.
0:41:31 > 0:41:35It's a law that applies to everything
0:41:35 > 0:41:38from a dropped jug to a burning star.
0:41:40 > 0:41:45A hot cup of tea to the products that we consume every day.
0:41:53 > 0:41:57All of this is an expression of the universe's tendency
0:41:57 > 0:42:00to move from order to disorder.
0:42:07 > 0:42:12Disorder is the fate of everything.
0:42:18 > 0:42:22Clausius had shown that something he called entropy
0:42:22 > 0:42:26was getting bigger all the time.
0:42:27 > 0:42:31Now Boltzmann had revealed what this really meant
0:42:31 > 0:42:36entropy was in fact a measure of the disorder of things.
0:42:41 > 0:42:43Energy is crumbling away.
0:42:43 > 0:42:45It's crumbling away now as we speak.
0:42:47 > 0:42:51So the second law is all about entropy increasing.
0:42:51 > 0:42:55It's just a technical way of saying things get worse.
0:43:23 > 0:43:26Boltzmann's passionate and romantic sensibility
0:43:26 > 0:43:28and his belief in the power mathematics
0:43:28 > 0:43:32had led him to one of the most important discoveries
0:43:32 > 0:43:34in the history of science.
0:43:34 > 0:43:37But those very same intense emotions
0:43:37 > 0:43:40had a dark and ultimately self-destructive side.
0:43:47 > 0:43:50Throughout his life
0:43:50 > 0:43:53Boltzmann had been prone to severe bouts of depression.
0:43:53 > 0:43:56Sometimes these were induced by the criticisms of his theories
0:43:56 > 0:43:58and sometimes they just happened.
0:44:00 > 0:44:03In 1906, he was forced to take a break from his studies in Vienna
0:44:03 > 0:44:06during a particularly bad episode.
0:44:17 > 0:44:21In September 1906, Boltzmann and his family were on holiday
0:44:21 > 0:44:25in Duino, near Trieste in Italy.
0:44:25 > 0:44:27While his wife and family were out at the beach,
0:44:27 > 0:44:29Boltzmann hanged himself,
0:44:29 > 0:44:34bringing his short time in our universe to an abrupt end.
0:44:34 > 0:44:37Perhaps the saddest aspect of Boltzmann's story
0:44:37 > 0:44:40is that, within a few short years of his death,
0:44:40 > 0:44:44his ideas that had been attacked and ridiculed during his life,
0:44:44 > 0:44:46were finally accepted.
0:44:46 > 0:44:50What's more, they became the new scientific orthodoxy.
0:44:59 > 0:45:05In the end there is no escaping entropy it is the ultimate move
0:45:05 > 0:45:09from order, to decay and disorder, that rules us all.
0:45:13 > 0:45:18Boltzmann's equation contains within it the mortality of everything
0:45:18 > 0:45:24from a china jug to a human life to the universe itself.
0:45:33 > 0:45:38The process of change and degradation is unavoidable.
0:45:38 > 0:45:42The second law says the universe itself must one day
0:45:42 > 0:45:47reach a point of maximum entropy, maximum disorder.
0:45:50 > 0:45:52The universe itself must one day die.
0:46:28 > 0:46:32If everything degrades, if everything becomes disordered
0:46:32 > 0:46:36you might be wondering how is it that WE exist.
0:46:37 > 0:46:40How exactly did the universe manage to create
0:46:40 > 0:46:45the exquisite complexity and structure of life on earth?
0:46:45 > 0:46:49Contrary to what you might think
0:46:49 > 0:46:53it's precisely because of the second law that all this exists.
0:46:54 > 0:46:59The great disordering of the cosmos gives rise to its complexity.
0:47:04 > 0:47:08It's possible to harness the natural flow
0:47:08 > 0:47:11from order to disorder, to tap into the process
0:47:11 > 0:47:16and generate something new, to create new order and new structure.
0:47:17 > 0:47:20It's what the early steam pioneers had unwittingly hit upon
0:47:20 > 0:47:21with their engines
0:47:21 > 0:47:25and it's what makes everything we deem special in our world -
0:47:25 > 0:47:31from this car, to buildings, to works of art, even to life itself.
0:47:49 > 0:47:51The engine of my car, like all engines,
0:47:51 > 0:47:54is designed to exploit the second law.
0:47:54 > 0:47:57It starts out with something nice and ordered like this petrol
0:47:57 > 0:47:59stuffed full of energy.
0:47:59 > 0:48:04But when it is ignited in the engine it turns this compact liquid
0:48:04 > 0:48:08into a mixture of gases 2,000 times greater in volume -
0:48:08 > 0:48:12not to mention dumping heat and sound into the environment.
0:48:12 > 0:48:15It's turning order to disorder.
0:48:23 > 0:48:27What's so spectacularly clever about my car
0:48:27 > 0:48:30is that it can harness that dissipating energy.
0:48:30 > 0:48:32It can siphon off a small bit of it
0:48:32 > 0:48:34and use it to run a more ordered process
0:48:34 > 0:48:39like driving the pistons which turn the wheels. That's what engines do.
0:48:39 > 0:48:43They tap into that flow from order to disorder
0:48:43 > 0:48:46and do something useful.
0:48:51 > 0:48:53But it's not just cars.
0:48:53 > 0:48:55Evolution has designed our bodies to work
0:48:55 > 0:48:58thanks to the very same principle.
0:48:58 > 0:49:00If I eat this chocolate bar
0:49:00 > 0:49:03packed full of nice, ordered energy,
0:49:03 > 0:49:07my body processes it and turns it into more disordered energy
0:49:07 > 0:49:10but powers itself off the proceeds.
0:49:16 > 0:49:21Both cars and humans power themselves by tapping into
0:49:21 > 0:49:24the great cosmic flow from order to disorder.
0:49:28 > 0:49:34Although overall the world is falling apart in disorder
0:49:34 > 0:49:37it is doing it in a seriously interesting way.
0:49:38 > 0:49:43It's like a waterfall that is rushing down,
0:49:43 > 0:49:48but the waterfall throws up a spray of structure
0:49:48 > 0:49:55and that spray of structure might be you or me or a daffodil or whatever.
0:49:55 > 0:49:59So you can see that the unwinding of the universe,
0:49:59 > 0:50:03this collapse into disorder, can in fact be constructive.
0:50:10 > 0:50:11Steam engines,
0:50:11 > 0:50:14power stations,
0:50:14 > 0:50:17life on earth -
0:50:17 > 0:50:20all of these things harness the cosmic flow
0:50:20 > 0:50:22from order to disorder.
0:50:32 > 0:50:35The reason the earth now looks the way it does
0:50:35 > 0:50:39is because we've learnt to harness the disintegrating energy
0:50:39 > 0:50:44of the universe to maintain and improve our small pocket of order.
0:50:47 > 0:50:50But as humankind has evolved,
0:50:50 > 0:50:54we've had to find new pieces of concentrated energy
0:50:54 > 0:50:58we can break down to drive the ever more demanding
0:50:58 > 0:51:02construction of our technologies, our cities, and our society.
0:51:05 > 0:51:10From food, to wood, to fossil fuels over human history
0:51:10 > 0:51:13we've discovered ever more concentrated forms of energy
0:51:13 > 0:51:16to unlock in order to flourish.
0:51:28 > 0:51:32Now in the 21st century we're on the cusp of harnessing
0:51:32 > 0:51:35the ultimate form of concentrated energy.
0:51:35 > 0:51:38The stuff that powers the sun.
0:51:39 > 0:51:41Hydrogen.
0:51:54 > 0:51:58This is the Cullham Centre for Fusion Energy in Oxford
0:51:58 > 0:52:03and at this facility they're attempting to recreate
0:52:03 > 0:52:06a star here on earth.
0:52:06 > 0:52:07But as you might imagine
0:52:07 > 0:52:10creating and containing a small star
0:52:10 > 0:52:12is not an easy process.
0:52:17 > 0:52:20It requires many hundreds of people
0:52:20 > 0:52:23and some extremely ingenious technology.
0:52:24 > 0:52:29This machine is called a tokamak and it's designed to extract
0:52:29 > 0:52:32an ancient type of highly-concentrated energy.
0:52:34 > 0:52:37The ordered energy of hydrogen atoms.
0:52:38 > 0:52:44These tiny packets of energy were forged in the early universe,
0:52:44 > 0:52:48just three minutes after the moment of creation itself.
0:52:52 > 0:52:58Now using the tokamak we can extract the concentrated energy
0:52:58 > 0:53:01contained in these atoms by fusing them together.
0:53:06 > 0:53:11Inside the tokamak machine two types of hydrogen gas,
0:53:11 > 0:53:13deuterium and tritium,
0:53:13 > 0:53:18are mixed together into a super hot state called a plasma.
0:53:18 > 0:53:22Now, when running this plasma can reach the incredible temperature
0:53:22 > 0:53:25of 150 million degrees!
0:53:25 > 0:53:28Large magnets in the walls of the tokamak contain the plasma
0:53:28 > 0:53:32and stop it touching the sides where it can cool down.
0:53:32 > 0:53:36When it gets hot enough the two types of hydrogen atoms
0:53:36 > 0:53:41fuse together to form helium and spit out a neutron.
0:53:41 > 0:53:43These neutrons fly out of the plasma
0:53:43 > 0:53:46and hit the walls of the tokamak, but they carry energy
0:53:46 > 0:53:51and the hope is that this energy can one day be used to heat up water,
0:53:51 > 0:53:55turn it into steam to drive a turbine and generate electricity.
0:53:56 > 0:54:00Essentially for a brief moment inside the tokamak
0:54:00 > 0:54:04a small doughnut-shaped star is created.
0:54:16 > 0:54:19The problem is it's extremely difficult to sustain
0:54:19 > 0:54:24the fusion reaction for long enough to harvest energy from it.
0:54:24 > 0:54:28And that's what the scientists at Cullham are working to perfect.
0:54:29 > 0:54:32It's a boundary between physics and engineering.
0:54:32 > 0:54:37How do we hold on to this very hot thing which is the plasma?
0:54:37 > 0:54:42And how do we optimise the way in the performance of this plasma?
0:54:42 > 0:54:46So what we want is the particles to stay in there as long as possible
0:54:46 > 0:54:49to maximise their chance of hitting each other.
0:54:49 > 0:54:53We are trying to push this to the limit
0:54:53 > 0:54:56with what we have available in this machine.
0:54:56 > 0:54:59And whatever we can learn to understand this plasma better
0:54:59 > 0:55:03will allow us to design a better machine in the future.
0:55:03 > 0:55:07Although it happens several times a day... Oh, here we go.
0:55:07 > 0:55:10The scientists here all gather round the screens.
0:55:10 > 0:55:13OK, it's about to come on.
0:55:47 > 0:55:49What the tokamak is doing
0:55:49 > 0:55:54is mining the fertile ashes of the big bang.
0:55:54 > 0:55:58Extracting concentrated energy captured at the beginning of time.
0:56:00 > 0:56:04As hydrogen is the most abundant element in the universe,
0:56:04 > 0:56:08if future machines can sustain fusion reactions,
0:56:08 > 0:56:12they offer us the possibility of almost unlimited energy.
0:56:22 > 0:56:26From a science that began as the by-product of questions
0:56:26 > 0:56:28about steam engines,
0:56:28 > 0:56:32thermodynamics has had a staggering impact on all our lives.
0:56:34 > 0:56:39It has shown us why we must consume concentrated energy to stay alive
0:56:39 > 0:56:45and has revealed to us how the universe itself is likely to end.
0:56:48 > 0:56:51Looking at the earth at night reveals how
0:56:51 > 0:56:55one seemingly simple idea transformed the planet.
0:57:14 > 0:57:19Over the past 300 years, we've developed ever more ingenious ways
0:57:19 > 0:57:23to harness the concentrated energy from the world around us.
0:57:23 > 0:57:27But all our efforts and achievements are quite insignificant
0:57:27 > 0:57:31when viewed from the perspective of the wider universe.
0:57:31 > 0:57:34As far as it's concerned all we are doing is trying to preserve
0:57:34 > 0:57:40this tiny pocket of order in a cosmos that's falling apart.
0:57:49 > 0:57:52Although we can never escape our ultimate fate
0:57:52 > 0:57:55the laws of physics have allowed us
0:57:55 > 0:57:59this brief, beautiful, creative moment
0:57:59 > 0:58:02in the great cosmic unwinding.
0:58:02 > 0:58:07My hope is that by understanding the universe in ever greater detail
0:58:07 > 0:58:11we can stretch this moment for many millions
0:58:11 > 0:58:14maybe even billions of years to come.
0:58:27 > 0:58:30The concept of information is a very strange one,
0:58:30 > 0:58:34it's actually a very difficult idea to get your head round.
0:58:34 > 0:58:37But in the journey to try and understand it
0:58:37 > 0:58:40scientists would discover that
0:58:40 > 0:58:44information is actually a fundamental part of our universe.
0:59:12 > 0:59:14Subtitles by Red Bee Media Ltd