A História da Ciência - Episódio 4: Podemos ter Energia Ilimitada? (2010) [HD]

Uploaded by ReVCieN on 16.08.2012

There are some great questions
that have intrigued and haunted us since the dawn of humanity.
What is out there?
How did we get here?
What is the world made of?
The story of our search to answer those questions is the story of science.
Of all human endeavours,
science has had the greatest impact on our lives -
on how we see the world, on how we see ourselves.
Its ideas, its achievements, its results are all around us.
So how did we arrive at a modern world?
Well, that is more surprising and more human than you might think.
The history of science is often told as a series of eureka moments,
the ultimate triumph of the rational mind.
But the truth is that power and passion,
rivalry and sheer blind chance have played equally significant parts.
In this series I'll be offering a different view of how science happens.
It's been shaped as much by what's outside the laboratory as inside.
This is the story of how history made science
and science made history,
and how the ideas that were generated changed our world.
It is a tale of power...
..and passion.
This time, an ancient human ambition -
the search for limitless power.
We are the most power-hungry generation that has ever lived.
Energy is the heartbeat of our civilisation.
The pursuit of power has created and destroyed fortunes.
It has raised and toppled nations.
And it has utterly transformed how we live our lives.
But this relentless search for more power has an importance
that is far greater than discovering what it can do for us.
When people ask themselves "What is power?" as opposed to simply, "Where can I get more of it?"
well, that led to some of the greatest insights in the whole history of science.
The 17th century was a pivotal edge,
when the balance between man and nature began to change forever.
There was no electricity.
There were no cars, no trains.
The most common power sources had to be fed and watered.
Horsepower meant just that.
But a remote beach in Holland would provide a glimpse of what was to come.
If you had been walking along a beach in north-west Holland 400 years ago
you might have seen a much larger version of one of these zip past.
It was called the wind chariot.
Designed to carry heavily armoured soldiers along the coast line...
..it amazed and terrified in equal measure.
Here was the power of the wind being harnessed to produce motion on land.
It must have been an extraordinary sight. Oh, yes.
The people were afraid of it and they called it a devil's rig.
The devil's rig. Very dramatic, yeah.
How fast? It could outpace a horse running.
Outpace a horse? So that must have made it one of the fastest things in the world at the time.
Probably one of the fastest things.
Using wind power. Just wind power. Very impressive.
The wind chariot was designed by an engineer and mathematician called Simon Stevin,
a remarkable man who would literally change the face of Holland
and help turn it into a great trading empire.
Because Stevin's ambitions for wind power went far beyond chariots.
He wanted to transform his country using mathematics.
Mathematics was changing.
For hundreds of years, in the universities,
geometry and arithmetic had been important theoretical pursuits.
Practical applications, like building bridges and firing canons, were limited.
But now, men like Simon Stevin would use maths theory
to create something much bigger...
A new, mathematically grounded science.
And that would help them solve a whole range of complex problems.
Now, Stevin was clearly a mathematician who didn't mind getting his hands dirty.
He saw the value of applying mathematical knowledge to the solution of practical problems.
The problem Stevin turned his mathematics to
was a crucial one in low-lying Holland -
How to keep the country dry.
For over a century, Holland's windmills had been scooping water
from drainage ditches, tipping it into canals to carry it away.
But Stevin was convinced that mathematics could make windmills much more efficient.
We're at the top of the windmill now and this is the gearing system.
This was the heart of what Stevin did.
Mathematically it's interesting because what he's done is, there is no whole number relationship.
It's not like two to one, three to one between this and this. There's no regular relationship.
Also you can probably see these things are angled.
It is not a simple vertical plane meeting a horizontal plane.
It's going at an angle.
And that is quite difficult to deal with mathematically as well.
It looks crude, but it is fantastically refined.
It's very impressive. I'm looking forward to seeing it run.
Magnificent isn't it? It's like being inside an enormous clock.
Standing here, you get the impression of
immense, inexorable power which is sort of just driving round and round.
And the thing which surprises me is it is so quiet.
And that is a tribute to Stevin's mathematics because he obviously got it right. The interactions all work.
There's very little clanking.
If all that power was being wasted in sound and heat, this whole place would be vibrating.
But actually it's very smooth.
This new, mathematically designed windmill
was three times more efficient than the ones it replaced.
It's almost poetic.
I mean, this is a mathematical model realised in a physical reality.
Stevin designed new paddle wheel shapes, sluices,
even a chain of windmills that could be used to drain not just fields, but a lake.
What's more, he patented his many inventions
to ensure his work would be well rewarded.
Mathematics made Stevin rich.
And it wasn't long before it started to change the whole country.
Simon Stevin had shown what really well designed windmills were capable of.
And people now began to ask themselves, "If they could drain lakes, what else could they do?"
Holland was already an emerging European force.
Now the power of windmills helped turn it into an industrial power house.
Seeds and nuts were ground to extract their valuable oil.
Paper mills became mechanised.
Wood could be cut 30 times faster and with greater precision than by hand...
..helping to turn this small country into the biggest ship builders in western Europe.
To the sound of mathematically designed mills whirring in the wind
Holland became an even more dynamic trading nation...
..and Amsterdam one of the richest
and most cosmopolitan cities on earth.
Here, you could buy almost anything -
diamonds, furs, exotic spices.
Amsterdam was enjoying a golden age.
The city produced the first central bank, the first stock exchange
and the first economic crash.
The growth of Holland changed the power map of Europe.
It had been helped by advances in windmill design
and new mathematically based science.
And a belief amongst men like Simon Stevin
that science should be useful.
It was obvious what power could do.
But what was still missing was any scientific understanding of what power actually is.
That would only begin to emerge far later, on the other side of the Channel.
The English country house of the 18th century was a place of intrigue,
romance and gossip.
But, between visits from dashing cavalry officers,
these bastions of high society
also hosted the occasional visiting experimenter.
The home of an unlikely alliance
that marked the birth of a world changing new source of power.
Science had become popular entertainment for the drawing room.
Most of these contraptions had been developed to explore the wonders of the age,
like static charge and magnetism.
Now that really is impressive.
Now, this was a real crowd pleaser.
The vacuum trick. What you do is you take an alarm...
set it to go off...
then put it in here...
and pump out the air.
The alarm clock goes off...
..and you hear...absolutely nothing.
No-one fully understood the science behind these demonstrations.
But the ability to dazzle and intrigue helped bring new ideas
to a new and attentive audience.
Matthew Boulton was an entrepreneur
who belonged to the Lunar Society,
so called because they met on the night of the full moon.
They were industrialists,
experimenters and natural philosophers
who all shared a love of practical knowledge.
A leading lunar man was Scottish engineer, James Watt.
For some years Watt had been working with prototype steam engines.
And this prompted Matthew Boulton to invite him to take part in a joint business venture.
He had heard that Watt was trying to develop a new type of steam engine.
As he later wrote to Watt, the reason for backing were twofold -
love of you and love of a money-getting ingenious project.
Now, the plan was clear.
Boulton had the capital, Watt had the idea.
Together they would get seriously rich.
This was capitalism in action.
The steam engine had enormous global impact.
And yet the surprising thing is, there was hardly any scientific theory behind it.
That would come later.
This is a Boulton and Watt steam engine.
And this the familiar bit - man, coal, furnace.
But what you might not expect is it is stationary and it is vast.
This single machine occupies the whole building.
So vast that this engine, originally built to keep the nearby canal topped up with water,
boasts its very own driver.
Hello. Hello. Nice to see you. You're the driver? Yes, I'm the driver of this engine.
I am amazed. This is still working, isn't it? Actually doing the job.
This, at this moment, is actually maintaining the canal. The electric pumps British Waterways
normally use are switched off and we're actually doing that job.
Can I have a go at driving? You certainly can. Step round this lever.
Always wanted to drive a steam engine.
This wasn't quite what I'd imagined it. Right OK.
So.. Turn that lever to the left, about a quarter of a turn.
There's a sort of narrow window between...
There is. There are indeed.
What drove the engine was not so much the power of the steam directly,
rather an industrial version of that country house trick - the vacuum.
The steam is injected, then cooled, creating a vacuum.
It's this which drags the piston head down
providing the engine with its lifting power.
Close it another quarter of a turn.
What's happened? Well, you actually closed it too far.
This is not good.
I was thinking it was really quite simple and then within 30 seconds of taking charge of this machine
I managed to stop it, which is quite bad.
That's looking good.
James Watt didn't invent the steam engine
or even the idea of using a vacuum.
Engines had been powered this way for decades.
Watt's fame, and that of his machine,
rests instead on one small modification
located here, right at the bottom of the engine.
It may not look like much, but down there
is James Watt's unique contribution to the story of power.
It's called a separate condenser.
It's where the steam was cooled to create the all-important vacuum
well away from the hot cylinders, a small but ingenious technical innovation with enormous benefits.
The Boulton and Watt steam engines were far more efficient than their rivals.
They used a quarter of the amount of coal.
The potential savings were enormous.
Something any business man could understand. Over to you.
Thank you.
Why some ideas change the world while others languish,
unloved and unnoticed, is seldom down to their intrinsic merit.
The success of Boulton and Watt's engine was not just due to new technology,
but also a clever piece of financial engineering.
The machines were complicated and needed someone to install them
and that someone was more often than not James Watt himself.
In his letters he complains bitterly about all the travelling he had to do.
Walk on.
Gee up, boys. Go on. Go on.
And you can sort of see why, can't you?
Lots of jolting. Now this is bearable...
Short trip, middle of summer.
But imagine there it's cold, it's winter,
it is absolutely lashing down - completely different experience.
But the discomfort of 18th-century travel was a price worth paying
because once his engines had been installed, the money began to flood in.
This three-page document was the key to Boulton and Watt's wealth.
It's a patent. It covers Watt's adaptations to the steam engine.
Now, you had to go on paying royalties year after year, long after the machine was installed.
Any savings you made from the machine, a proportion went straight back to them.
I think it's very telling how scientific discovery is rarely far away from the smell of money,
and that's especially true of the search for power.
But, for all the riches on offer, there was still no real
scientific framework to explain what power actually is.
Science would have to wait till steam power became a force throughout the land.
The big demand for steam engines was in the West Country,
pumping flood water from mines.
Their owners soon became reliant on Boulton and Watt's more efficient machines.
Some mine owners, fed up with royalties, stopped paying.
Boulton and Watt got tough and responded with legal writs.
It's said that a delivery man who came to one of these mines
was seized by the ankles, hung over the mine shaft and asked if he still wanted to deliver that writ.
The man behind that particular story was Richard Trevithick.
To get round of Watt's patent Trevithick began to build his own engines.
This was his greatest achievement, the Puffing Devil,
all eight horsepower of it.
And unlike Boulton and Watt's engine, it moved.
Trevithick's genius was he built high pressure steam engines where the steam drives the piston.
So he didn't need vacuums or condensers.
Instead of being the size of houses, his steam engines were small, powerful, mobile.
And as an added bonus they produced that wonderful "whoo-hoo" noise.
That's the sound of high-pressure steam escaping.
I'd read that people thought they were incredibly dangerous, and not unreasonably,
that they would blow up, the high-pressure system.
You're quite right. They didn't have the knowledge of metallurgy
we do today, and they did get boiler explosions.
There's no risk of this one blowing up, I take it?
Not at all.
This new steam engine clearly pointed to a better way of moving goods and people around.
Yet Trevithick has not gone down in history as the father of the modern railway.
I gather that he actually did, on one occasion, manage to get
his steam car, if you like, on a track, on a railway. Why didn't it work?
The engine weighed five tonnes or so, so the rails broke under the weight of the engine.
So the problem wasn't the train at all. It was the rail it was running on. Absolutely.
Yes, the engine worked a dream.
Right. That is incredibly ironic isn't it? Yeah.
The history of science is full of moments like this.
Great ideas have to come at the right place and the right time.
Sadly for Trevithick, the place and time were wrong.
So why didn't he die rich and famous?
Well, it's partly because he didn't have his own Matthew Boulton to get his inventions out there
and to make sure he was raking in the cash.
But it's also because his ideas were well ahead of their time.
In the early 1800s, if you wanted to get from A to B, you were better off buying a horse.
Steam engines would eventually bring unprecedented change
borne out of a combination of different forces.
The Lunar Society, where men of science and business
could meet and exchange ideas.
Technical innovations, like high-pressure steam.
The promise of money and the protection of patents.
From all this emerged a previously unimaginable source of power...
..the mechanical equivalent of countless horses
to work the factories and mills of the 19th-century landscape.
The steam engines, their profits, their owners,
these were the forces shaping Victorian Britain.
But the effects of all this power were felt far beyond the world of heavy industry.
The new aristocracy of factory owners and businessmen knew
just how they wanted to use their new-found influence.
Some used their wealth to campaign for social change,
like the abolition of slavery or the education of women.
The search for power had given political power to a new group of people, the middle classes.
The quest for power had produced so much...
but with no more scientific understanding than had existed a century before.
Only now, belatedly, came the theorists.
The Victorians were utterly entranced by the power of steam.
But the science behind it posed some of the greatest questions of the age.
It demanded a new theory, a new way of looking at nature.
Fortunately help was at hand.
This is Mrs Beeton's Book Of Household Management,
a Victorian classic which contains pretty well everything you need to know
about how to run a household efficiently and well,
including how to sack your servants.
"Frugality and economy are virtues, without which no household can prosper."
Mrs Beeton, like so many in Victorian society, was obsessed with efficiency.
Waste was not just uneconomical, it was also un-Christian.
In the kitchen, if you had old bones, you made soup.
If you had old bread, you made a pudding.
And this obsession was shared by the scientific community.
In fact, it led to the development of a whole new concept, that of energy.
As steam engines took off, people became interested in comparing which engines were most efficient.
A new theory of energy would now help them make precisely that sort of judgment.
No-one really knew what energy is.
Some people thought of it as a fluid which flows from one place to another.
But what was becoming increasingly clear is it could be transferred.
The steam engine, like a kettle, could be explained scientifically.
As it burns, chemical energy from the coal is turned into heat.
This energy heats the kettle and the water inside....
Which turns into steam, which can then be used to perform work.
It sounds really simple, but this was a turning point in science.
For the first time, such diverse things as heating coals,
warming water, production of steam, even the spinning of windmills
could all be united by a single concept - that of energy.
It led to the formulation of a new law of physics, one that is absolutely fundamental.
It's called the first law of thermodynamics.
The first law of thermodynamics is a mathematical description of energy,
known as conservation of energy.
It states that energy cannot be created or destroyed.
So you can never get more out than is contained in the fuel you put in.
And it applies to every source of power there is -
from kettles, to steam engines,
to windmills.
Thermodynamics was one of the crowning glories of 19th-century science,
inspired in part by the need to explain
that wonder of the age, the steam engine.
And by an obsession with thrift and efficiency.
But thermodynamics was only one component
of what was to be a far more comprehensive theory of energy and power.
In June 1772, a small sailing expedition set off for the coast of France
on a voyage that would help point science towards the modern age.
Its leader was John Walsh, recently retired from the British East India Company.
Walsh was fascinated by the electricity found in nature.
He went looking for it, not in the skies, but under water...
..in a fish....
..the torpedo fish...
..which uses electric shocks to catch its prey.
Walsh wanted to find out whether the power emitted by this strange fish
was the same as that given off by lightning...
..or a spark generator.
Having done numerous experiments on himself and his crew,
Walsh now headed back to London to try and find out
just how the torpedo fish produced electric shocks.
Some of the fish Walsh brought back are still preserved
at the Hunterian Museum in London.
They were dissected by the renowned surgeon John Hunter to reveal some very peculiar organs.
Well, you see these two patches of white tissue, one top, one bottom either side of the fish?
These are things which Hunter hadn't seen before in other fish,
other rays that he'd dissected.
Right. This one looks very different.
It's a much more detailed dissection,
but also Hunter's worked a bit of magic on it
by injecting it with a red dye to show where the blood vessels are.
The electric charge seemed to come from these tiny cells,
now known as electrocytes, found within the electric organs.
It is extraordinary because you begin to see where the charge would have come from.
You can actually see each of the cells. It is beautiful, isn't it?
A work of art. A work of art in its own right, isn't it?
Walsh was convinced that the electricity from the torpedo fish
was not only the same as the electricity in lightning,
but that it must be possible to produce it using a machine.
But plenty of people did not agree with Walsh.
It seemed almost sacrilegious to claim that electricity from a machine made by man
was exactly the same as electricity from a fish which had been created by God.
And yet, proof that this was the case was not far away.
In the archives of the Royal Society in London sits a letter that dates back to 1800.
Written by an Italian scientist, Alessandro Volta,
essentially it contains instructions on how to build your very own torpedo fish.
This is a copy of the letter that Volta sent to the Royal Society.
It's in French, got a useful diagram over in the corner.
I've also got a box here of bits and pieces.
Right, first of all I need some zinc and some copper.
Also I need some bits of cardboard or tissue
capable of soaking up a briny solution.
It is very hard to believe
this is actually going to do anything.
We shall see.
A piece of copper on the top and I've got a lead on it.
Now, if you look at it closely, it really does resemble
the working bits, if you like, of a torpedo fish.
And he suggested to call it an artificial electric organ.
The "voltaic pile", as it became known,
could generate a significant electric current.
Volta couldn't measure it, but he could demonstrate
that it delivered a shock, just like the torpedo fish.
Oh! Ooh!
What's interesting is that Volta, when he writes to the Royal Society,
effectively gives away all his secrets,
which is a bit of a shame for him because this turned out to be
one of the greatest technological discoveries of all time.
It is of course the battery.
What is really surprising, looking at it from a modern perspective,
is that for a long time people had no idea what to do with the battery.
It had not obvious practical application.
There was nothing to plug it into.
It would be a generation before somebody managed to find
a really significant practical use.
An ingenious response to a rather urgent problem.
On the 18th June 1815,
the armies of the Duke of Wellington and the Emperor Napoleon met at Waterloo.
It was a battle on whose outcome rested the fate of Europe.
By the end of the day, the battle was over. The French had lost.
Wellington was keen to get this good news to London as quickly as possible.
Major Henry Percy was ordered to carry the message.
He mounted his battle-weary horse and rode off across Belgium until he got to the coast.
When he arrived, he had to wait for the correct wind and tide
before finally he could set sail for England.
In all, it took him four days to reach London,
four days during which I'm sure the people in the war office
were biting their fingernails with anxiety
because many expected the French to win.
Now, if you could have got a secret message from Waterloo to London
faster than Major Percy, you could have made a fortune, betting on an improbable English victory.
There was clearly a need for faster communication.
Volta's Pile was about to get plugged into something useful.
And this time it was science that led the way, thanks to a man called Hans Christian Oersted.
The story goes he was about to give a lecture and he was preparing his equipment.
Amongst it, he had a voltaic pile and some wire.
When he connected up the wire, something utterly unexpected happened.
The needle of a nearby compass twitched
and every time he connected the wire
or disconnected,
it moved again.
People had known for centuries that compass needles were deflected by magnets.
Somehow the electric current in the wire was also acting like a magnet,
deflecting the needle, which left Oersted completely baffled.
Now, he obviously realised this was important
because he did further research and published his findings.
But I think it's extremely unlikely he ever appreciated
just what a massive impact his discovery would make on the world.
Within a few years, that twitching compass needle had grown into the electric telegraph.
The power of electricity could now be used to get messages from A to B almost instantaneously.
Telegraph tables were soon running right across the globe.
And when the telegraph came together with that other great invention the steam engine,
the combination was unstoppable.
Steam power did the heavy work -
draining mines, spinning cotton,
powering a new railway network.
And with the telegraph that ran alongside those same railways,
the battery brought control - political and financial.
Together, they helped build the empires of 19th-century Europe.
The stage was now set for the next step in the scientific understanding of power.
The tiny, twitching needle of the telegraph had shown
how electricity from a battery could be truly useful.
But what's happening here is also something which is much more profound.
It is the coming together of two great forces
that previously were regarded as utterly separate.
And covering the link between two things as disparate as an electric current and a magnetic compass
was one of the greatest achievements of science,
a major step towards a unified concept of energy.
Electricity was the crowd pleaser.
Flashes, sparks, electric shocks.
Magnetism was altogether more sedate, something of interest mainly to navigators.
But when the two came together, they created the science of electromagnetism
that would dominate the 19th century.
Electromagnetism not only explained the relationship between electricity and magnetism,
it would go on to explain the very nature of light...
..of radio waves...
of x-rays.
And it helped persuade 19th-century physicists
that they had now discovered all the fundamental laws of nature.
As it turned out, this cosy assumption was somewhat wide of the mark.
At the turn of the 20th century, the discovery of a new element
was splashed across front pages all over the world.
One reason for all the excitement was the way radium behaved.
It spontaneously glowed in the dark...
..and created ghostly patterns on photographic plates.
It seemed to be creating energy out of nowhere.
Radium's mysterious properties caught the public imagination,
helping to sell a new range of consumer products...
..which was unfortunate, since radium is radioactive.
..Yes. Thank you. Have a look.
OK. So what am I looking at?
Well, you're looking at a variety of radioactive consumer products,
mostly from the 1920s,
produced in the United States. So this one here, for example,
you actually put... Water in it. You put water in it?
That is the most famous of the radioactive quack cures, at least in the United States.
Over half a million of these were sold.
This is a similar device, except, rather than put the water in it,
you would put this in the water.
This is not radioactive now, I take it? Or mildly?
Yes, it is radioactive, but it's mild.
It is quite spooky, I must admit.
I can hear it still active all these years later.
So great was the hype
that small amounts were put into toothpaste,
heat pads, toys.
Just the name radium was enough to sell a product.
Radium, er...condoms!
Oh, it's an empty box. I was looking forward to seeing a radium condom.
The scientists responsible for first isolating radium were Marie Curie
and her husband, Pierre.
It didn't take them long to recognise its extraordinary potential.
One of the things that stood out in Marie's mind
and piqued her curiosity and interest
was the tremendous amount of energy being released by the radium.
So they saw radium as a potentially unlimited source of energy, did they? Yes. Absolutely.
So they saw radium as a potentially unlimited source of energy, did they? Yes. Absolutely.
Just one gram contained enough energy to turn a tonne of freezing water into steam...
while one tonne of radium could do the work
of one-and-a-half million tonnes of coal.
The problem facing the scientists is that all this seemed to go
completely against the established laws of physics.
Radioactivity presented a serious problem for scientists.
They knew that energy cannot be created or destroyed.
That is the first law of thermodynamics.
But they also knew that these radioactive substances were pouring out huge amounts of energy.
So where was it coming from?
Across the world scientists had been studying radioactivity intensely.
People noticed something peculiar -
that as radioactive substances emit energy, they transform.
They turn into something else.
Radium, for example, becomes lead.
And as they transform, they become lighter.
In other words, as they emit energy, they also lose mass.
The link between energy and mass was eventually explained by Albert Einstein's famous equation.
Energy equals mass times the square of the speed of light.
The energy from the radium wasn't coming from some magical source,
but from the mass itself.
People had previously realised that you could describe heat and movement in terms of energy.
Now it seemed you could also describe mass in the same way.
Energy which hadn't even existed as a concept
was now being used to explain the very nature of matter itself.
In fact there wasn't much that could not be explained in terms of energy.
Not just steam engines...
and windmills,
but living things.
Stars, even galaxies were all governed by the laws of energy.
In its quest to understand what power is,
science had uncovered secrets which lay at the very heart of the universe.
The theory encapsulated in E equals MC squared would eventually lead
to the release of nuclear energy and the atomic bomb.
But the consequences of that belong to a different story.
Instead, to complete the story of power, I want to go back to the 19th century.
Back then theories of energy might have been lighting up men's minds,
but they weren't lighting up homes.
Not yet, at any rate.
Most people's domestic lives were largely unaffected
by developments in thermodynamics or electromagnetism.
Outside there were telegraphs and steam trains,
but at home, gas lamps, candles and open fires.
What changed our personal relationship with power was the discovery
that the link between electricity and magnetism worked both ways.
Oersted had shown that an electric current could act just like a magnet.
British scientist Michael Faraday was the first to demonstrate the opposite,
that moving a magnet could produce an electric current.
He used the idea that switching on an electric current could make a magnetised piece of metal move
to build the world's first electric motor.
But he also demonstrated the reverse is true.
Take a magnet, push it through some copper wire
and you produce electricity.
Beautiful, isn't it?
It's called electromagnetic induction
and it was the key to the electric age.
If one could keep the magnet moving fast enough,
one could produce an electric current that was continuous.
What was needed was something to keep the magnet moving.
Something like this.
Niagara Falls, one of the most powerful waterfalls in the world.
This is about as close as I can get to the Falls and it really is magnificent.
There's about a 150 million litres of water coming over the Falls every single minute.
And you can really feel the power.
The challenge lay in finding a way of converting this mass of energy
into an altogether more useful form - electricity.
Until very recently, I couldn't have stood here because there would have been millions of litres of water
just pouring down here, sweeping everything away.
Up that way, about a kilometre or so,
is the power station.
The project began deep under ground.
Tunnels were dug into solid rock by hand
to divert some of the water to an electrical generator.
Those taking part sensed the dawn of a new age.
When it was first built, it was described as a feat to rival the pyramids, the temples of the Greeks,
the great cathedrals of Europe, a monument to the scientific age.
And personally I think they were right.
Because these giant turbines really are the ultimate expression
both of what power is and what power does.
Huge magnets turned by the power of falling water,
creating enough electricity to power three quarters of a million light bulbs.
But for electricity to become a true commodity,
something that could be bought and sold,
there was one final barrier to overcome -
how to get electricity from here in Niagara to the places you'd actually want to sell it.
Cities like Buffalo, 24 miles away,
or power-hungry New York, 400 miles away.
The problem was the power loss as the current travelled along the cable.
If you happened to live near a generating plant like this, then you were fine.
But the further away you moved, the less power you got.
After just a mile,
you would begin to notice the difference.
After two miles, hardly any current would be getting through at all.
But here at Niagara, this problem was overcome.
Its generators produced what's known as alternating current -
high voltage, low power loss...
..which meant that electricity could finally travel.
When, in 1896, this new form of current was switched on,
it took less than a second to reach Buffalo, over 20 miles away.
In that instant was born the electric age.
The discovery of what power can do for us has transformed our lives
and set us on a relentless search for new sources of energy.
From deep within the earth to inside the smallest atom,
to the sun itself, a hunger for more power knows few bounds.
Small wonder that our planet alone in the solar system glows in the dark.
But the quest to find out what power is
has had an equally profound effect.
Using the language of mathematics,
we have shown energy to be a basic property of the universe.
And it's the coming together of the practical and theoretical approaches to power
which underpins the modern world.
For a long time, the search for power was led by practical men.
And then the theorists caught up.
And to the plaintive cry, "Can we have limitless power?"
replied a resounding "No."
But that search also led to the uncovering of the fundamental laws of nature
which now tell us how everything in the universe operates.
Next time, the great puzzle of existence...
What is the secret of life.
Subtitles by Red Bee Media Ltd
E-mail subtitling@bbc.co.uk