Original subtitles

- [Narrator] The world's greatest structures,

push the boundaries of engineering,

all fueled by a constant desire to innovate.

- Without engineering there will be no modern world.

- [Narrator] Gigantic buildings,

complex infrastructure,

and ingenious inventions.

- Engineering is the key that turns dreams into reality.

- [Narrator] Many of today's incredible achievements

rely on breakthrough technologies first devised

by ancient engineers.

- It's astounding how they achieve this.

- [Narrator] Early civilizations

built on an unimaginable scale,

and with incredible precision.

- They raised a bar for engineering

in a way that no one thought possible.

- These are some of the finest engineers in history.

- [Narrator] Redefining the known laws of physics

and dreaming up the impossible.

They constructed engineering wonders,

from colossal stadiums

to mighty waterways,

and complex machines,

all with the simplest of tools.

- You cannot imagine the skills people would've needed

to build like this.

- [Narrator] By unearthing the mysteries

left by these ancient engineers,

we can now decode their secrets.

- That so many of their creations still survive

is testament to their engineering prowess.

- [Narrator] And ultimately reveal

how they're genius laid the foundations

for everything we build today.

(upbeat music)

(dramatic music)

Navigation,

charting a course from A to B,

shapes our lives.

- Without navigation there'd be no trade,

there'd be no exploration,

there'd be no sharing of ideas,

there'd be no modern world.

- It really is the thing that has brought us

to where we are today.

- [Narrator] It has allowed us

to conquer towering mountain ranges,

inhospitable deserts,

vast oceans,

and even the cosmos beyond our planet.

- It has transformed our relationship with the world.

- [Narrator] Today, cutting edge tools

guide us where we want to go,

anywhere on the globe,

using nothing more than a smartphone.

- The level of advancements that we have today

in navigation technology

is really just incredible.

- The sky really is the limit.

- [Narrator] Modern navigation depends on exact timekeeping

and accurate measurement of position.

But the machines that make that precision possible

would never have been invented

without the engineering brilliance

of the ancient world.

(waves crushing)

1100 BC,

the wild and wind-swept Pacific.

The first civilization to successfully navigate

its treacherous waters

were the Polynesians.

Without even basic seafaring maps,

they sent sail

on the most extraordinary voyages of discovery.

Traversing the vast expanse of the Pacific Ocean,

from the west of Polynesia to New Zealand in the south,

and Hawaii, and Easter Island in the east.

- It's hard to imagine

what it would've been like

out there in the middle of the sea,

with the wind and the waves

in very simple vessels.

- They were true explorers

who set out with one mission and one mission only,

to find new lands.

- [Narrator] They faced rough seas

in handcrafted catamarans.

And navigated using charts made from palms and shells,

which showed natural indicators

like sea swells and wave patterns.

- They used these techniques

to travel thousands of miles,

even 2,000 miles from Tahiti to the Hawaiian Islands.

- [Narrator] And like other early explorers,

the Polynesians relied on

the greatest natural navigational tool of all,

the sky's above.

- They looked up to the heavens

to help them understand exactly where they were.

- [Narrator] Navigation relies on knowing two coordinates,

latitude and latitude.

Latitude is positioned north or south of the equator,

represented by horizontal lines around the globe.

Longitude is east/west position,

and is represented by vertical lines called meridians,

which radiate from the polls.

Ancient mariners didn't have these grid lines,

but they knew that latitude could be gauged

by measuring the angle between the horizon and a star.

Most stars, including the sun,

change position depending on time of day.

One, Polaris,

the North Star is fixed.

Navigators used it to figure latitude,

but their tools were basic

so measurements were imprecise.

- With no reliable instrumentation to help them,

readings would always been quite prone to inaccuracies

due to the movement of the ship.

- A difference of a degree or so

could result in disaster.

Explorers needed a leap force in technology.

- [Narrator] And the breakthrough

that first brought precision to navigation

would come from one of the great civilizations

of the ancient world.

(water rushing)

(suspenseful music)

Greece, one of the most advanced societies of antiquity

and the birthplace of a precision device

that set navigation on a new course.

- It was the smartphone of the era.

- They are a work of art.

They're a beautiful-looking thing.

- The largest was said to be able to perform

up to a thousand mathematical equations.

- [Narrator] The device was an astrolabe,

meaning star taker in Greek.

It was a navigational breakthrough

because it could accurately measure angles,

and therefore latitude.

- It was the first scientific instrument

to come into production,

which actually gave sailors an accurate measurement.

Astrolabes were really important in the world of navigation.

- [Narrator] An exquisite example of precision engineering,

the astrolabe was crafted in flawless detail,

usually from brass.

It consisted of a base called the mater.

On top, went removable plates

with lines representing celestial coordinates.

Then an open pattern disc,

the rete, featured a map of the stars.

Finally, there was a ruler at the back,

called an alidade.

It was aligned with a celestial body,

usually the North Star.

And a reading of the angle of latitude

was taken from a scale at the bottom of the astrolabe.

Navigators now had a tool

that could calculate the angle of a star and horizon

more precisely than before,

eliminating much of the guesswork

when measuring latitude.

- This is something

that really hadn't been available before.

- It really was an incredible leap forwards

in our ability to find our way around the world.

- [Narrator] The astrolabe, born in Greece,

was refined in the Arab world.

And by the 12th Century,

use of the improved Islamic model

had spread from the Arabian Peninsula,

right across Europe,

helping travelers navigate further

and better than before.

- It revolutionized sailing,

and navigation, travel, exploration, more widely.

And astrolabes remained one of

the only type of engineered instruments

available to sailors

right up until the 1600s and 1700s.

- [Narrator] The astrolabe improved navigational accuracy,

but when it came to way-finding on an ocean voyage,

it did have one fatal flaw.

- The astrolabe requires a steady hand to hold it,

and a fixed point

from which to take the angle between your position

and the celestial body.

- For all the benefits that the astrolabes brought,

if you were on a boat in a stormy sea,

it would've been impossible to use.

- [Narrator] Ancient engineers

created a mariner's astrolabe.

Much heavier than the original,

it was also sturdier and more streamlined.

But in the eye of a storm,

it still wasn't accurate enough.

A new instrument was needed to deliver exact measurements,

even in the roughest weather conditions.

It finally arrived in the 18th Century.

- The history of navigation

is actually a continual quest for increasing accuracy.

And there were key moments of technological innovation

in that process.

- [Narrator] One of those pivotal moments

came in the 1700s

with the invention of a new precision tool,

the sextant.

It was developed simultaneously

by inventors in England and the United States.

And it determined latitude in the same way

as the astrolabe,

by gauging the angle between the horizon and the sun,

or a known star,

but it was up to 90 times more accurate.

- It's the kind of accuracy

that ancient navigators would've only dreamed of.

It's an enormous step forward

in terms of engineering feat and also navigation precision.

- [Narrator] How did the sextant achieve

this vastly improved accuracy?

With clever engineering.

It measures the angle between the horizon

and a celestial body, like the North Star.

But rather than taking a direct reading

as the astrolabe did,

it uses a telescope and two mirrors.

The lower mirror is half silvered

and the horizon is viewed through it using a telescope.

The higher mirror is attached to a moveable arm,

its positioned so the light from the star,

reflected in the top mirror,

is also reflected off the bottom one

and into the telescope.

The image of the star and horizon

are then aligned in the eye piece.

And the angle between them

is read off a scale at the bottom of the sextant.

Optics and brilliant engineering

meant latitude readings were now more accurate

in any weather conditions.

- Even if you're out in a ship

and there's some movement on the ship,

the horizon to the star,

the relative positions of those remain fairly static.

So it means you can get a much more accurate reading

of where you are than you would do using an astrolabe.

So it was one of the go to tools for our ancestors.

- [Narrator] The sextant

didn't fix every navigational problem.

The other key metrics,

direction of travel and longitude,

require different engineering solutions.

But it did solve one major piece of the puzzle,

measurement of latitude.

And it's rock steady reliability

meant it was used right up to the 20th Century.

Eventually guiding explorers

on the greatest adventure in human history.

Apollo 11,

the first manned mission to ever land on the moon.

(rocket thrusters blasting)

One of the greatest navigational triumphs of all time.

- It's 1969,

and you are going to space,

you're landing on the moon.

- [Narrator] The human effort was monumental,

but space travel was fraught with real and present danger.

- You've got 240,000 miles to traverse

from here to the moon,

you have to get there safely.

- [Narrator] The flight path of Apollo 11,

trace an extraordinary figure of a trajectory

plotted to maximize the impact of the gravitational pull

of both the Earth and the moon on the spacecraft.

But navigating to their destination

was just the beginning

of the challenges the astronauts faced.

- Landing on the moon

has so many dangers involved in itself.

The moon is moving over 2,000 mph,

the surface is unknown.

It was an incredible challenge to land.

- [Narrator] Apollo 11 used a computer less powerful

than a modern pocket calculator

to control its guidance system.

And it was prone to inaccuracy.

The extraordinary solution,

an onboard sextant and space telescope could be used

when other measurements proved unreliable.

- It was the most futuristic flight of its time,

there still needed to be a low-tech backup option

that can ensure worst-case scenario

that had a way of navigating.

So using sextants actually is just a fail safe.

We know it works, and it always works,

and we can trust it.

And I guess when you go into the moon,

you want some technology that you can trust.

- [Narrator] And the sextant's reliability

would be proven beyond doubt in April, 1970.

Apollo 13 was to be NASA's third lunar landing mission.

(fireball blasting)

But days after launch,

an explosion crippled the spacecraft.

With navigational systems rendered useless,

craft and crew were left floating in space

with no way to get back to Earth.

But the onboard sextant gave a glimmer of hope.

- [Mission Command] Okay, stand by 13, we're looking at it.

- [Narrator] A line that delineates night from day on Earth

is visible from space.

It's known as the terminator line.

And captain James Lovell used it

and the onboard sextant to plot re-entry.

- Jim Lovell relied on

his skill to be able to use the sextant

to bring them back safely.

- [Narrator] Lovell used a landmark he could rely on,

the terminator line, to guide him and his crew safely home,

a way-finding technique first used in centuries past.

(waves crashing)

Early mariners in Europe hugged the shoreline

and depended on coastal landmarks to find their way.

But as voyages grew ever more ambitious,

sailors needed extra reference points to guide them.

So the ancients built the first manmade structures

to aid navigation,

the lighthouse.

- Lighthouses didn't necessarily mark dangerous navigation,

rocks and reefs.

In fact, they were landmarks

which marked safe harbors.

- [Narrator] The most iconic of antiquity

was a monumental landmark that helped sailors

navigate the Mediterranean Sea,

the Lighthouse of Alexandria.

One of the seven wonders of the ancient world,

it was up to 460 feet tall,

second only in height to the Pyramid of Giza.

It's thought that a light from a fire at its top

was reflected out to sea by a polished bronze mirror,

helping to guide sailors to the safe Harbor of Alexandria.

- Undoubtedly, it projected not just light,

but a symbol of status.

It showed extraordinary engineering prowess.

- [Narrator] Creating a stable structure

capable of withstanding the wild coast of the Mediterranean

with no small feat.

It's thought the lighthouse was built in three sections

on foundation stones of granite.

But its thick walls

were made from enormous blocks of limestone.

And when it came to holding those gargantuan slabs together,

the engineers of ancient Alexandria

deployed an extraordinary building technique.

- Instead of mortar, as you might suspect,

this enormous structure was actually held together

with molten lead.

- This is a common technique

of jointing stones in the ancient world.

Mortar takes time to cure.

So the smart thing to do

is to use molted lead.

- [Narrator] To fasten the stones together,

channels were drilled in adjacent blocks.

A little molten lead was then poured in.

An iron bolt could then be added for extra strength

before more molten lead secured it.

Stone slabs laid above

would then be held in place

with staple-shaped clamps,

secured with tar, bitumen, or perhaps lead.

Using a malleable material like lead

was smart structural engineering.

- Buildings always move to some degree.

Lead molds around the stone

and has the ability to just take a little bit of movement

when the stone moves.

- Thanks to the clever techniques used in its construction,

the lighthouse of Alexandria guided navigators

to safe harbor for an extraordinary 1,600 years

before being destroyed by Earthquakes

in the early 1300s.

A jaw dropping example of ancient architecture.

It's inspired engineering

has cast its beam right through to the modern era.

Today, even in the age of satellite technology

and GPS navigation,

there are over 20,000 lighthouses dotted around the globe,

all acting as reliable reference points

to passing navigators.

Some are so powerful

that their light travels for almost 40 miles.

These incredible beam distances are achieved,

not with bronze mirrors,

like those in the Lighthouse of Alexandria,

but with powerful lenses,

first developed by French physicist, Augustin Fresnel,

in the 1820s.

- Before the Fresnel lens, lighthouse lenses

were really rather large, big, and quite deep.

So they were quite unwieldy.

- [Narrator] The thickness of traditional lenses

meant that much of the light

was absorbed by the glass itself.

Fresnel's solution to this problem,

to create a lens that was thinner and lighter

than any that had gone before.

- Fresnel's genius was that

he concentrated and intensified the light source.

So what that meant

was that you could project that light,

both further and more accurately.

- [Narrator] His understanding

of how light bends or refracts

was key to his game-changing invention.

He realized that light traveling through glass,

air, and back through glass

will exit at the same angle as it enters,

therefore removing the thick center of a lens

will have no effect on the light's behavior,

but it does result in a weaker lens.

Fresnel's solution was to collapse the sides

to create a jagged profile.

He then flattened one side

before spacing the grooves of the lens apart,

allowing air to pass through,

helping to reduce the heat within.

His ingenious engineering produced a streamlined lens

that dissipated the ferocious heat of lighthouse fires

and utilized more of the light they produced.

- What we saw was a drastic improvement

of the way in which the light sources used

because the traditional lenses

was soaking up around about 50% of the light.

But what Fresnel's lens did

was actually use 98% of that light.

- [Narrator] Fresnel's clever use of refraction

made lighthouses more powerful,

preventing a vast number of shipwrecks.

- It would've saved countless lives,

not thousands,

but I think hundreds of thousands of lives.

- [Narrator] Fresnel's lens was a monumental leap forward

that changed navigation forever.

But a discovery in the Middle East

proved that harnessing the power of the lens

is nothing new.

(dramatic music)

Northern Iraq,

it was here amongst ancient Assyrian ruins

that an extraordinary find,

hinted at just how much our ancestors understood optics,

the Nimrud lens.

Ground from a piece of rock crystal

almost 3,000 years ago,

it's the first known lens in the world.

- And it's such a fascinating discovery

because it hints at knowledge

that many of us would not even conceive

that the ancient world had.

- [Narrator] The oldest lens ever found,

the Nimrud is small in size,

but great care had been taken in its production.

A strong indication that

the ancient Assyrians appreciated the power of the lens.

- This could be the birth of optics,

the moment when we could start to understand

the properties of light,

we could start to manipulate light.

- [Narrator] From its ancient beginnings,

the lens would ultimately prove pivotal

in the development of precise navigational instruments,

including the emergence of the world's first telescopes

in the 1600s.

- In 1608,

the Dutchman, Hans Lipperhey,

announced a new lens-based seeing instrument.

And he claimed it could magnify objects up to three times.

- [Narrator] After Lipperhey's initial invention,

the telescope reached new Heights of sophistication

thanks to work of

the brilliant Italian mathematician, Galileo.

- Within days of hearing about Lipperhey's invention,

Galileo designed his own,

and his could magnify objects

20 times greater than they really were.

- [Narrator] Galileo trained his telescope on the skies,

making many heavenly discoveries,

including craters and mountains on the moon,

and a band of diffused light

that we now know as the Milky Way.

Thanks to him and to others

like German astronomer, Johan Kepler,

the telescope grew in power,

helping the human race navigate our own planet too.

- Before the telescope,

vision relied purely on the human eye,

but suddenly you could see further than ever before.

You could almost see beyond the horizon.

- [Narrator] And the reflecting telescope,

first invented by Isaac Newton,

brought the cosmos even closer.

Using mirrors rather than lenses to capture light,

reflecting telescopes have grown in size and range

over the centuries,

opening our eyes to the skies above,

and eventually sewing the seeds of human exploration

beyond our own solar system.

The Hubble Telescope,

for the last three decades,

it has been orbiting in space,

340 miles above Earth.

Its mission,

to see stars billions of light years away.

- One of the big problems

with having a telescope here,

down here on Earth,

was that you've got to see

through this soup of gas and dust in the atmosphere.

So the solution lay

in actually getting the telescope on the other side

of the atmosphere.

And that's what Hubble was all about.

- [Narrator] Launched in 1990,

Hubble was designed to capture distant stars

using two mirrors.

It is powerful enough

to detect the light of a firefly

at a distance of some 7,000 miles.

A perfect marriage of optics

and cutting edge engineering,

it promised unimagined insights

into the universe we live in.

But then disaster struck.

- When those first pictures come back,

they were slightly blurred

and there was a problem with this telescope.

- [Narrator] The Hubble images

were too unclear to be useful.

With a multi-billion dollar project in jeopardy,

engineers needed to find a solution, fast.

- When you've got a piece of technology this sophisticated,

what you really wanna do

is bring it back into the garage or the workshop

and to be able to work on it there, don't you?

But this was just simply not an option.

- [Narrator] Tests revealed

that the edges of the telescopes primary mirror

were too flat by the width of

just one 50th the thickness of a human hair.

This tiny imperfection

was responsible for the telescopes blurred images.

- The unfortunate thing

was that the problem part, the primary mirror,

wasn't replaceable.

And this created a huge problem for NASA.

- [Narrator] With no hope of repairing

or replacing the faulty mirror,

scientists engineered an extraordinary solution.

They built a corrective lens

which could compensate for the mirror's flaw.

- It's remarkable really,

instead of actually fixing the primary mirror,

what they did is in effect

provide it with a pair of reading glasses.

- [Narrator] But making the corrective lens

was just one challenge,

fitting it was another.

- The real Marvel of this whole episode

was the fact that the astronauts had to do

what I would call a roadside fix.

They had to take the kit up there

and fix this thing in outer space.

And that's what they did.

- [Narrator] One of the most complex tasks

ever completed in space,

it took astronauts 10 days to refit the telescope.

But when the corrective lens was opened,

Hubble's true potential was finally revealed.

- When the images came back,

we could see stars,

13 billion light years away.

That's almost the age of the universe.

It's up there with putting the first man on the moon.

- [Narrator] Hubble has now spent

over three decades in space

and undergone a total of five manned repair missions.

- The Hubble Telescope

was an amazing feat of space engineering,

but for me,

the fact that it was fixed in outer space

is the really, really remarkable feat of engineering.

- [Narrator] The telescope

has made an incredible 1.5 million observations,

helping us to understand, more fully,

the universe we may one day explore.

But it's not the first groundbreaking piece

of precision engineering

to change our comprehension of the world around us.

To find their way,

ancient navigators depended on known landmarks

and observation of the sun and stars.

The Astrolabe, and eventually the sextant,

made measuring latitude, location on the north/south axis,

more accurate.

But for early adventurers,

a precise calculation of the direction of travel

was impossible.

- It was all very well roughly knowing

where north or south was,

but over huge distances.

Any tiny inaccuracy

could lead to a massive error.

- [Narrator] Sailors desperately needed to engineer a tool

that could reliably show direction of travel.

But the seeds of that navigational breakthrough

wouldn't be found aboard a wind blown ship,

but in the serene mysticism of the ancient orient.

China, 2nd Century BC,

this was the moment

when the human race first discovered the tool

which would go on to transform navigation forever.

The magnetic compass.

- At its simplest form,

a compass is a magnetized piece of metal or a needle

that can spin.

And because it's magnetized,

it will align with the Earth's magnetic field

and point north/south.

- [Narrator] The planet's giant magnetic field

is created by electrical currents

produced by the movement of molten iron

below the Earth's crust.

A compass works by aligning along this magnetic field

to show a north/south direction.

From this, navigators can also calculate

the direction of east and west.

But the compasses in China 2,000 years ago

looked nothing like the way-finding instruments

we use today.

- The very first compasses

were magnetized piece of rock,

essentially naturally occurring magnets,

called lodestones.

- [Narrator] The ancient Chinese discovered that

a lodestone suspended so it could turn freely

would always point in the same direction.

Seeing this in 200 BC,

would've been an astonishing experience.

- I can't imagine what it would've felt.

First discovering these new properties,

that metals could align itself

with the same direction,

time and time again.

They would've thought it was magic.

- [Narrator] The lodestones of ancient China

were regarded as mystical.

Fashioned into spoon-shaped compasses,

they were used for fortune telling and divination.

Their potential as a navigational tool

was only realized 1,200 years later,

around 1000 AD.

But it wasn't until the 1300s

when the compass reached Europe,

that it underwent a major transformation.

- A key moment in the development of the compass

was the invention of the compass rose.

It was a card which went with the compass

and it marked out direction.

- [Narrator] The rose was usually placed

below the compass needle.

Originally used to indicate the directions of the winds,

by the 14th century,

it featured more reliable cardinal directions,

north, south, east, and west.

It was a game-changing moment for navigation.

- Suddenly the mariner could actually understand

in which direction he was traveling

with a degree of accuracy.

- [Narrator] Navigators no longer depended solely

on landmarks and observation of the stars to find their way.

And the trailblazing mariners of the era

used it to explore new territories.

From Vasco da Gamma's trip from Europe to India,

to the expedition led by Ferdinand Magellan

that circumnavigated the globe,

and Christopher Columbus' journey to the Americas.

- The compass gave these navigators

the competence they needed to explore uncharted territories.

It's up there with those step-change innovations

like the wheel,

really taking the human race forward.

- [Narrator] The compass combined a natural phenomenon,

magnetism, with the little engineering ingenuity

to make way-finding much more accurate.

But it also brought incredible improvements

in another key area of navigation,

mapmaking.

For thousands of years,

humans have known that

having a physical representation of the world

could be an incredible tool.

- Maps give you a huge advantage over your enemy.

You know where your resources are,

you know where you can trade,

you know where the dangers are.

- [Narrator] The first attempt to make an accurate map

came in the 2nd Century AD

with mathematician and geographer, Claudius Ptolemy.

- Ptolemy mapped his known world,

featuring over 8,000 locations on a grid system,

which laid the foundation for latitude and longitude.

- [Narrator] After the time of Ptolemy

and the fall of the Roman empire,

the accuracy of mapmaking dwindled.

It wasn't until the Renaissance Period

that the quest for accurate cartography

was revived by the expansion of trade,

fueled by the invention of the compass.

- We're really in need of some kind of navigation aids

to make sure we can get from A to B safely.

And this is where our first maps,

proper maps as we would expect them to be,

start to appear.

- [Narrator] The first of these

were Portolan charts,

they featured rough outlines of coastline,

and crucially, rhumb lines,

which radiated out in the directions of a compass.

These allowed sailors to chart a course,

but they weren't perfect.

- Now the problem with these rhumb lines

is they don't account for the curvature of the Earth.

- [Narrator] Sailors using rhumb lines

had to take bearings at regular intervals to stay on course.

The problem for cartographers

was the difficulty of representing a spherical shape,

the Earth, on a flat piece of paper.

A cleverly engineered solution

to this navigational conundrum

arrived in 1569 with the Mercator projection.

It accounts for the curvature of the planet

by projecting the map of the Earth onto a cylinder.

Once flattened out,

this makes lines of latitude equidistant from each other

and lines of longitude parallel,

turning a map of curved lines

into a regular flat grid.

The Mercator projection

did distort the sizes of land masses,

making countries closer to the poles seem larger.

But this was vastly outweighed

by the huge advantages it brought to navigation.

- What it allowed you to do

was to steer on a constant bearing.

And what that meant

is you weren't constantly taking readings,

like you would be with rhumb lines,

trying to get from A to B.

You could just take that constant bearing.

It guaranteed arrival.

And that's what was crucial for early merchants.

- [Narrator] It used basic mathematical principles

to bring precision to mapmaking and navigation.

And even today,

450 years after its creation,

mapmakers still use methods similar

to the timeless brilliance of the Mercator projection.

(ship hooting)

By the 1700s,

the sextant was used to accurately calculate latitude.

And using dependable compasses and maps

helped sailors charter reliable course,

but navigating their planned route

remained an imprecise and often treacherous undertaking.

- There was a huge piece of the puzzle still missing,

and that was how to find your longitude,

your east to west navigation.

- Without an accurate position of longitude,

you still don't really know exactly where you are.

- [Narrator] Longitude is east/west position

and is measured in degrees.

Zero degrees longitude or the prime meridian

runs through Greenwich in London.

For every 15 degrees traveled east or west,

time changes by one hour,

jumping ahead to the east of Greenwich,

falling behind to the west.

And because of this direct relationship,

time can be used to determine longitude

to make the necessary measurements,

sailors needed a clock that kept good time at sea.

But a reliable enough time piece

just didn't exist in the 18th century.

So clock makers of the day raced to engineer one.

But the seeds of their inventiveness

lay way back in the ancient world.

(birds chirping)

Our nomadic hunter-gatherer ancestors didn't measure time

in the same way we do today.

But all that began to change around 12,000 years ago

with one of the most monumental advances in human history,

agriculture.

The changing seasons dictated life as never before

and measuring time became a necessity.

- The year became split into smaller and smaller segments.

First looking at season by season,

then month by month.

And then suddenly we were looking at

jobs that needed to be done on a daily basis.

- [Narrator] The ancient Egyptians

were amongst the first farmers of antiquity,

helped by rich fertile soil,

and a reliable water supply from the mighty River Nile.

And the Egyptians, along with the Greeks,

were also one of the early civilizations to record time,

using obelisks and sundials.

- Sundials were our ancestors' first attempt

to break down the day into smaller segments.

- If you set it up correctly,

you should be able to tell, accurate within five minutes,

your local time.

- [Narrator] The tower of the winds in Athens,

built in the 1st or 2nd Centuries BC,

it contained nine sundials.

But it also housed another revolution in timekeeping,

a water clock.

Water clocks were made of a large barrel

with a stoppered hole or spout at the bottom.

Working a little like a giant egg timer,

they were designed to take exactly 12 hours to empty.

Lines inside the barrel

would then mark out the hours

as the water drained away.

- The advantages of a water clock over a sundial

is that it can be used indoors,

it can be used 24/7,

and it can be used regardless of the weather outside.

- [Narrator] Water clocks were a significant leap forward

in the recording of time,

but the flow of water was impossible to regulate precisely.

So time could never be measured consistently.

It would take one of the great engineering minds

of the ancient world

to introduce mechanization.

And new levels of accuracy to time keeping.

11th Century China,

the reign of the mighty Song dynasty.

- The Song dynasty was a period

of astonishing cultural invention.

They developed porcelain,

gunpowder, paper money, tea.

- [Narrator] This was also an era

when the water clock

would undergo an extraordinary transformation.

The emperor ordered his minister of justice,

a polymath called Su Song

to create a world-beating time piece.

- Su Song was asked to make the most extraordinary clock

that had ever been built.

It had to display the lunar cycle,

it had to map the heavens,

and of course, it had to tell the time.

- [Narrator] The problem was that

a traditional water clock

could never be precise enough or powerful enough

to meet the emperor's exacting demands.

Su Song's solution,

a 40-foot, five-story high mechanical clock

with a series of automatons

whose movements told the time.

This replica in modern day China

hints at its impressive scale.

- An absolutely incredible piece.

The likes of which had never been seen before.

- [Narrator] But Su Song's clock didn't just look different,

it was also engineered to function

in a completely new way.

- Su Song's water clock

was different to a traditional water clock in that,

instead of using water to tell the time,

it used water as its power source.

- [Narrator] Previous water clocks

had used falling water level

to indicate time.

Su Song used water to power

a giant, precisely-engineered wheel,

which in turn, controlled the clock's gears.

The wheel was regulated by water flowing evenly

into cups attached to it.

Once each cup was heavy enough,

it would trip a mechanism and fall,

carrying forward the one behind it,

thus propelling the wheel.

- A water clock without those precision elements within it

would never have been able to carry out

the number of functions

that Su Song wanted for their clock.

- An incredible work of engineering for its day,

it was revolutionary.

- [Narrator] Su Song had come up with an ingenious way

to power the clock.

But for accurate timekeeping,

the whole mechanism needed to be carefully controlled.

He achieved this with a feat of extraordinary engineering,

one of the world's first ever clock escapements.

- And that's the really precise part

that actually controls the release of power,

step by step through the mechanism itself.

- Even today,

the escapement in any mechanical clock

works by stopping and starting motion

in a regulated way.

On Su Song's clock,

this meant precisely controlling the movement

of the cups on the water wheel

and therefore the rotation of the wheel itself.

It was achieved by using connected beams

called steelyards.

One, at the bottom,

regulated the movement of the cups,

the other at the top,

controlled the action of the wheel.

As each cup filled,

the steelyard at the bottom, tilted down,

pulling one end of the beam at the top, down,

but raising the other end.

This disengaged it from the teeth of the wheel,

allowing it to move forward.

- The escapement is the part that causes the tick.

To witness the first sound of ticking,

to ever be brought to life in the world,

must have been an incredible experience.

- This was a good 200 years

before we saw any kind of mechanical clock in the west.

So incredibly advanced for its time.

- [Narrator] Su Song's masterpiece

was a first step towards the mechanization of the clock.

And it was the automation of timekeeping

that would ultimately improve the accuracy of navigation.

But the next great leap forward

would emerge not in China,

but thousands of miles away.

On the other side of the globe.

(clock ticking)

Medieval Europe,

it's here, around 200 years

after Su Song's hybrid mechanical water clock,

that the first fully mechanized escapements

known as verge escapements appear.

- The verge escapements

was first developed for use in tower clocks

that we'd see in public spaces.

Unlike Su Song's clock,

where the escapement was power by the movement of water,

the verge escapement was entirely mechanical.

- [Narrator] Powered by a winding mechanism,

the verge escapement

built on the principles of Su Song's clock.

An escape wheel with teeth

is attached to the gear mechanism.

A metal rod called a verge

is set perpendicular to the wheel.

Two pallets on the verge

engage and disengage the wheel

in an oscillating motion.

Above, a beam with weights on either end,

known as a foliate, twists back and forth

controlling the movement of the mechanism.

- The verge escapement was an absolute game-changer.

It revolutionized timekeeping.

And this was because for the first time,

we were not reliant on an external force,

such as water,

to keep our mechanisms running.

What we relied on instead

were weights within the escapement itself

to keep transferring power

in a regular, mechanized, controllable way.

- [Narrator] But the mechanization of the clock

didn't just change timekeeping forever.

It would also solve the final navigational puzzle,

reading longitude accurately at sea.

- Early navigators

could work out their latitude quite easily

with a sextant,

and they could also work out their direction with a compass,

but they couldn't accurately work out their longitude.

So half of the calculation was simply missing.

- [Narrator] The solution lay in accurate timekeeping.

Imagine a ship sales west, from Europe to America.

For every 15 degrees of longitude traveled,

time shifts back by one hour.

So by comparing time on board

with time at a known longitude,

like home port,

navigators could, in theory,

work out their longitude.

Ship's time was read by measuring the position of the sun.

But time at home port

could only be determined by setting a clock before departure

and hoping it kept true at sea.

The problem was

that the pendulum clocks popular back then

were accurate on land,

but completely unworkable at sea.

- Clocks at that time were very sensitive to movement.

So having a clock at sea

where you're being thrown around,

would've made the accuracy of these clocks pretty useless.

- [Narrator] Desperate for a solution,

the government in London took decisive action.

- They've set up a competition for inventors

and engineers to find a way

to keep that accurate time at sea,

to enable sailors, to find longitude.

- [Narrator] The British Government

offered a reward of £20,000,

equivalent to several million dollars today

to anyone who could solve the longitude problem.

No one came close,

until more than 20 years after the prize was raised.

Self-taught clockmaker John Harrison invented a time piece

that offered the faintest glimmer of hope.

- His first invention, H1,

tried to compensate for the movement of the ship

by having two separate barrels

to balance the movement, one from the other.

It wasn't particularly successful.

(page flipping)

- [Narrator] Undeterred, Harrison spent almost 30 years

on further experimentation.

And after two unsuccessful attempts

at improving his original design,

he finally hit the jackpot.

His era-defining invention

was a ship's chronometer,

a maritime time piece named H4.

- It was really an advancement in timekeeping

because it could work at sea very accurately.

It wasn't affected as much by the movement of the boat.

- [Narrator] Harrison's genius

was that he replaced the clock's pendulum

with a modified verge escapement

featuring an oscillating balance wheel and hairspring.

The movement of the wheel

is controlled by the regulated coiling

and uncoiling of the hairspring.

This mechanism was much lighter than a pendulum

and its motion wasn't affected by movement onboard ship.

- An enormous, enormous improvement

in terms of both precision engineering,

and precision navigation as well.

- [Narrator] Using the clock-making concepts

of his ancestors,

Harrison had finally cracked an age old problem.

His incredible invention

allowed sailors to calculate accurate longitude.

- It's like everything has come together at once now

and we have all the ingredients we need

to be able to navigate successfully.

- [Narrator] A turning point in the course of human history,

his engineering accomplishments

have shaped the world as we know it today.

- By demonstrating

just how accurate a mechanical timekeeper could be,

Harrison triggered a revolution in the way we tell time.

There hasn't been another change,

quite like the advent of the chronometer

until the advent of GPS.

- [Narrator] Today, 50,000 ships

(airplane engine roaring)

and 20,000 aircraft

help keep international trade, worth $28 trillion a year,

moving around the globe.

And the way-finding tools of old

are no match for our complex world.

Now navigation relies on three simple letters,

G-P-S.

- GPS is the biggest advance in navigation

since the sextant and the chronometer.

- [Narrator] Controlled by satellites

and super-precise atomic clocks

that lose just one second in up to 100 million years,

the technology is so sophisticated

that a GPS enabled smartphone

can give accurate location within a radius of just 16 feet.

- Satellites orbit the Earth twice a day,

and they beam out a unique signal

and that allows devices on Earth

to read that signal and pinpoint their exact location.

- [Narrator] The technology would've stunned our ancestors,

but it was their ingenuity

that sewed the seeds of modern high tech navigation.

- In our mobile phone,

we have the power, the knowledge, the ingenuity

of all of those thousands of years of development,

of navigation at our fingertips.

- It wouldn't have been possible to do what we do now.

Had it not been for the contributions of our ancestors.

(helicopter rotor blades rattling)

- [Narrator] From the Dawn of time,

the human race has had a burning desire to explore.

It's the spark that inspired the great minds of antiquity

to create navigational tools

that changed the world.

And today, it drives us to venture beyond our planet.

But our lofty ambitions

and our astonishing accomplishments

would be impossible without the sheer engineering brilliance

of our ancestors in the ancient world.

(upbeat music)