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  • How did humans acquire the power to transform the planet like this?

  • Looking at the earth at night

  • reveals to us just how successful we've been

  • in harnessing and manipulating energy

  • and how important it is to our existence.

  • Energy is vital to us all.

  • We use it to build the structures that surround and protect us.

  • We use it to power our transport and light our homes.

  • And even more crucially, energy is essential for life itself.

  • Without the energy we get from the food we eat, we'd die.

  • But what exactly is energy?

  • And what makes it so useful to us?

  • In attempting to answer these questions,

  • scientists would come up with a strange set of laws

  • that would link together everything, from engines, to humans, to stars.

  • It turns out that energy, so crucial to our daily lives

  • also helps us make sense of the entire universe.

  • This film is the intriguing story

  • of how we discovered the rules that drive the universe.

  • It is the story of how we realised

  • that all forms of energy are destined to degrade and fall apart.

  • To move from order to disorder.

  • It's the story of how this amazing process

  • has been harnessed by the universe

  • to create everything that we see around us.

  • Over the course of human history,

  • we've come up with all sorts of different ways

  • of extracting energy from our environment.

  • Everything from picking fruit,

  • to burning wood, to sailing boats, to waterwheels.

  • But around 300 years ago, something incredible happened.

  • Humans developed machines

  • that were capable of processing extraordinary amounts of energy

  • to carry out previously unimaginable tasks.

  • This happened thanks to many people and for many different reasons,

  • but I'd like to begin this story

  • with one of the most intriguing characters

  • in the history of science.

  • One of the first to attempt to understand energy.

  • Gottfried Leibniz was a diplomat, scientist, philosopher and genius.

  • He was forever trying to understand the mechanisms

  • that made the universe work.

  • Leibniz like several of his great contemporaries

  • was absolutely convinced that the world we see around us

  • is a vast machine designed by a powerful and wise person.

  • And if you could understand how machines worked,

  • you could therefore understand how the universe

  • and the principles that had been used to make the universe worked as well.

  • So there was an extremely close relationship for Leibniz

  • between theology and philosophy on the one hand

  • and engineering and mechanics on the other.

  • It was this relationship between philosophy and engineering

  • that in 1676 would lead him to investigate

  • what at first sight seemed to be a very simple question.

  • What happens when objects collide?

  • This is was what Leibniz

  • and many of his contemporaries were grappling with.

  • So when these two balls bump into each other,

  • the movement of one gets transferred to the other.

  • It's as though something's been passed between them

  • and this that Leibniz called the living force.

  • He thought of it as a stuff,

  • as a real physical substance that gets exchanged during collisions.

  • Leibniz argued that the world is a living machine

  • and that inside the machine,

  • there is a quantity of living force put there by God at the Creation

  • that will stay the same forever.

  • So the amount of living force in the world will be conserved.

  • The puzzle was to define it.

  • Leibnitz would soon find a simple mathematical way

  • to describe the living force.

  • But he would also see something else.

  • EXPLOSION

  • He realised that in gunpowder, fire and steam,

  • his living force was being released in violent and powerful ways.

  • EXPLOSION

  • If this could be harnessed,

  • it could give humankind unimaginable power.

  • Leibniz would soon become fascinated

  • with ways of capturing the living force.

  • A prolific letter writer, Leibniz struck up correspondence

  • with a young French scientist called Denis Papin.

  • As they corresponded, Leibniz and Papin realised

  • the living force released in certain situations

  • could indeed be harnessed.

  • Heat could be converted in to some form of useful action.

  • But how far could this idea be taken?

  • Papin was in no doubt.

  • This is an extract from his letter to Leibniz...

  • "I can assure you that the more I go forward,

  • "the more I find reason to think highly of this invention,

  • "which in theory, may augment the powers of man to infinity.

  • "But in practice, I believe I can say without exaggeration,

  • "that one man by this means

  • "will be able to do as much as 100 others can do without it."

  • Now, you might expect me at this point to tell you

  • that Leibniz and Papin changed the world forever.

  • Well, they hadn't.

  • Their ideas had been profound and far reaching, yes,

  • but they hadn't really moved things forward.

  • For that, you need something much more tangible.

  • You need innovation, industry.

  • You need countless skilled workers and craftsmen

  • who are going to apply these ideas,

  • to experiment with them in novel and new ways.

  • Well, in the century that followed Leibniz and Papin,

  • this would take place in the most dramatic way imaginable.

  • 150 years after Leibniz and Papin's discussions,

  • the living force had been harnessed in spectacular ways.

  • The machines they dreamed of had become a reality.

  • Steam engines were now the cutting edge of 19th century technology.

  • If you look at steps in civilisation,

  • then one great step was the steam engine, because it replaced muscle,

  • animal muscle, including our muscle, by steam power.

  • And the steam power was effectively limitless

  • and hugely important to doing almost unimaginable things.

  • But steam technology would do more than just transform human society.

  • It would uncover the truth about what Leibniz had called

  • the living force and reveal new insights

  • about the workings of our universe.

  • This is Crossness in south-east London.

  • It's an incredible industrial cathedral,

  • home to some of the most impressive Victorian steam engines ever built.

  • Constructed in 1854, Crossness houses four huge engines

  • that once required 5,000 tonnes of coal each year

  • to drive their 47-tonne beams.

  • Everything about this place seems to have been built to impress.

  • From the lavish ironwork -

  • the grand pillars like something out of a Greek or Roman temple.

  • It's the kind of effort you'd think would be lavished

  • on a luxury ocean liner for the rich and famous.

  • And yet this place was built to process sewage.

  • Although only a few workers and engineers would see inside it,

  • steam had become

  • such a vital part of Britain's power and economic prosperity

  • that it was afforded almost religious respect.

  • But for all the great success and immense power

  • that engines were bestowing on their creators

  • there was still a great deal of confusion and mystery

  • surrounding exactly how and why they worked.

  • In particular questions like, "How efficient could they be made?"

  • "Were there limits to their power?"

  • Ultimately, people wanted to know

  • just what might it be possible to achieve with steam.

  • The reason these questions persisted was simple almost no-one

  • had understood the fundamental nature of the steam engine.

  • Very few were aware of the cosmic principle which underpinned it.

  • These great lumbering machines we think of as the early steam engines

  • actually were the seed of understanding

  • of everything that goes on in the universe.

  • As unlikely as it sounds,

  • steam engines held within them the secrets of the cosmos.

  • This is the Chateau de Vincennes in Paris.

  • Events here would motivate one man's journey to uncover the cosmic truth

  • about the steam engine, and help to create a new science.

  • The science of heat and motion. Thermo-dynamics.

  • In March 1814, during the Napoleonic wars,

  • when Napoleon and his armies where fighting elsewhere,

  • Paris itself came under sustained attack

  • from the combined forces of Russia, Prussia and Austria.

  • Citizens were deployed around key locations to protect them.

  • This chateau was being defended by a group of inexperienced students

  • who were forced to retreat under sustained artillery fire.

  • One of them was a brilliant young scientist and soldier.

  • His name was Nicolas Leonard Sadi Carnot

  • and the humiliation he felt personally

  • would drive him and motivate him

  • to uncover a profound insight into how all engines work.

  • Carnot came from a highly-respected military family.

  • After the French defeat here and elsewhere around Europe,

  • he became determined to reclaim French pride.

  • What really bothered Carnot was the technological superiority

  • that France's enemies seemed to possess.

  • And Britain, in particular, had this huge advantage

  • both militarily and economically

  • because of its mastery of steam power.

  • So Carnot vowed to really understand how steam engines work

  • and use that knowledge for the benefit of France.

  • He says absolutely explicitly that if you could take away

  • steam engines from Britain

  • then the British Empire would collapse.

  • And he's writing in the wake of French military defeat

  • and he proposes to analyse,

  • literally, the source of British power

  • by analysing the way in which fire and heat engines work.

  • Living on half-pay with his brother Hippolyte

  • in a small apartment in Paris,

  • in 1824 Carnot wrote the now legendary

  • Reflections On The Motive Power Of Fire.

  • In just under 60 pages,

  • he developed and abstracted the fundamental way

  • in which all heat engines work.

  • Carnot saw that all heat engines

  • comprised of a hot source in cooler surroundings.

  • Now, Carnot believed heat was some kind of substance

  • that would flow like water from the hot to the cool.

  • And just like water falling from a height

  • the flow of heat could be tapped to do useful work.

  • Carnot's crucial insight

  • was to show that to make any heat engine more efficient

  • all you had to do was to increase the difference in temperature

  • between the heat source and cooler surroundings.

  • This idea has guided engineers for 200 years.

  • Ultimately, a car engine is more efficient than a steam engine

  • because it runs at a much hotter temperature.

  • Jet engines are more efficient still

  • thanks to the incredible temperatures they can run at.

  • Carnot had revealed

  • that heat engines weren't just a clever invention.

  • They were tapping into a deeper property of nature.

  • They were exploiting the flow of energy

  • between hot and cold.

  • Carnot had glimpsed the true nature of heat engines and, in the process,

  • begun a new branch of science.

  • But he would never see the impact his idea would have on the world.

  • In 1832, a cholera epidemic spread through Paris.

  • It was so severe, it would kill almost 19,000 people.

  • Now, back then, there was no real scientific understanding

  • of how the disease spread, so it must have been terrifying.

  • Carnot undaunted by the risks,

  • decided to study and document the spread of the disease.

  • But, unfortunately, he contracted it himself and was dead a day later.

  • He was just 36 years old.

  • A lot of his precious scientific papers were burned

  • to stop the spread of the contagion

  • and his ideas fell into temporary obscurity.

  • It seems the world wasn't quite ready for Carnot.

  • Carnot had made the first great contribution

  • to the science of thermodynamics.

  • But as the 19th century progressed the study of heat, motion and energy

  • began to grip the wider scientific community.

  • Soon, it was realised these ideas could do much more

  • than simply explain how heat engines worked.

  • Just as Leibniz had suspected with his notion of living force,

  • these ideas were applicable on a much grander scale.

  • By the mid 19th century,

  • scientists and engineers had worked out very precisely

  • how different forms of energy relate to each other.

  • They measured how much of a particular kind of energy is needed

  • to make a certain amount of a different kind.

  • Let me give you an example.

  • The amount of energy needed to heat 30ml of water

  • by one degree centigrade

  • is the same as the amount of energy needed

  • to lift this 12.5kg weight by one metre.

  • The deeper point here that people realised

  • was that although mechanical work and heat may seem very different,

  • they are, in fact, both facets of the same thing - energy.

  • This idea would come to be known as the first law of thermodynamics.

  • The first law reveals that energy is never created or destroyed.

  • It just changes from