All language subtitles for Ancient.Engineering.S02E04.1080p.AMZN.WEB-DL.DDP2.0.H264-chr00t_track3_[eng]

- [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)