All language subtitles for Ancient.Engineering.S02E02.1080p.AMZN.WEB-DL.DDP2.0.H264-chr00t_track3_[eng]

(dramatic music)

- [Narrator] The world's
greatest structures

push the boundaries
of engineering.

All fueled by a constant
desire to innovate.

- Without engineering, there
would 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 their genius

laid the foundations for
everything we build today.

(gentle music)

It's the most luxurious
element on the planet.

A metal like no other.

The ultimate symbol of wealth

and success.

(crowd cheering)

Gold.

It obsesses us and has
captivated cultures

around the world
throughout history,

inspiring legends of lost cities

and kings with the Midas touch.

- It's beautiful.

It's burnished.

There's a warmth to gold.

Something that draws
human beings towards it.

Almost like it sort
of warms human nature.

- Gold's the most
wonderful material.

It's malleable,
it doesn't decay.

So it's very useful, as
well as very attractive.

- [Narrator] And what makes gold

especially valuable
is it's rarity.

- It's that sort
of Goldilocks thing

of being rare enough to
tempt people to want it,

but not so rare that
nobody can have it.

- [Narrator] In fact,
it's estimated that

all the gold extracted
from the earth so far

would fit into a 65 foot cube.

Only a few times bigger
than a semi-detached house.

Since ancient times,
the pursuit of gold

has driven engineers to
devise new techniques

to mine,

process

and refine it.

- The desire for gold
actually led to huge

technological and
engineering advancements.

- [Narrator] Their inventions
have shaped modern society.

- They've established the
global markets we have today.

It changed the world forever.

- [Narrator] And these
ancient breakthroughs

are still prompting
us to cross frontiers,

building the deepest mines,

creating the latest
technology...

- [Announcer] Three, two...

- [Narrator] Even venturing-

- [Announcer] Zero.

- [Narrator] Into space.

But how did these
ancient engineers

first discover gold's
unique properties?

There's no clear evidence

for when gold was
first discovered.

The earliest surviving
objects in the world

date from over 6,000 years ago

from sites in the Black
Sea and the near east.

But earlier humans may have
found gold long before this.

It simply washed
up at their feet.

- If it's in a riverbed,
you'll see the gold glinting.

It doesn't rust,

it doesn't dissolve in
water or do anything.

So it's there and
it's lying there.

It's getting rounded
and bumped around a bit,

but it's in the river bed.

- [Narrator] It's likely that
this river, or alluvial, gold

would've caught the
eye of ancient peoples,

who began to experiment with it.

- One could imagine that
the very first discovery,

when someone picked
it up and said,

"Hey, look, I can hammer
this into a nice object."

Would have been an alluvial
nugget, it's obvious.

- [Narrator] But how
did it get there?

Gold can only be created
by extreme energy

produced inside rare supernova

or the collision
of neutron stars.

All of the gold on
Earth, therefore,

likely comes from outer space.

Much of it from
meteorites and boulders,

which slammed into its
surface billions of years ago.

Most of this gold
is buried deep,

but some has been brought
closer to the Earth's surface

around tectonic plates
through volcanic activity.

Super heated water transports
dissolved elements,

including gold, up
through the crust

where they solidify
into hard veins.

Over time, as water
erodes these veins,

tiny pieces wash into rivers.

And as gold is one of the
least reactive metals,

it will not corrode and
can stay here indefinitely.

- When it comes out the ground

it's as shiny as the day
it went in, you know,

and I think there is
an element of that

that's captured the imagination

of past societies
going way back.

- [Narrator] Early
gold gathering

may simply have
been done by hand.

But to find gold hidden deeper
among the river deposits

required a more
specialized solution.

- And the natural progression
is to try a basin,

whether it was of wood, pottery,
early bronze or whatever.

You swirl it round
and, if you're lucky,

there'll be few little
bits of gold glinting

in the bottom of the
bowl at the end of it.

And that's gold panning.

- [Narrator] Gold
panning was likely

ancient man's main
extraction method.

And alluvial gold is
estimated to have provided

two thirds of what
was ever produced.

Because the panning
process is so simple,

it has remained a widely
used method to this day.

(gentle music)

Facilitating some
of the greatest gold
rushes of all time.

- [Male] There was gold for all.

Gold seekers were
stirred to a frenzy

by tales of glory holes
and rich diggings.

- [Narrator] In 1848, gold
was found in California,

sparking the famous
American Gold Rush.

In just over a year,
California's population

increased from 14,000

(upbeat music)

to almost 100,000.

- Once the news gets out,
all hell breaks loose

'cause people want to
get it and go for it.

It's this optimism and
greed going for it.

- [Narrator] In their
haste to find gold,

these prospectors even
abandon their ships

in the Bay of San Francisco.

The remnants still lie buried
under the financial district.

To look for gold, they
headed to the mountains and,

initially at least, just use

simple panning
methods to find it.

- Panning for gold is an
incredibly democratic method.

You don't need many resources,

you don't need much
training or skill.

- [Narrator] But this
technique is labor intensive,

time consuming, and it
doesn't get you much gold.

To find more, the
ancients needed

to follow the trail underground.

(dramatic music)

To reach the motherload.

Few ancient cultures are
more associated with gold

than the Egyptians.

Famed for their elaborate
engineering projects,

gold was central to
Egyptian culture.

Used for opulent decoration,
jewelry and statues.

In fact, the hieroglyph for gold

first appeared with the
beginning of Egyptian writing

in the very first dynasty.

The Egyptians believed that gold

was the flesh of the sun god Ra.

So were not far off about
its stellar origins.

- For the Egyptians, gold
was associated with divinity.

It was associated with creation.

It was literally the most
significant, powerful object

you could imagine.

- [Narrator] The
ultimate luxury material,

gold was coveted in life.

But it was just as
important in death.

- Whether you're a pharaoh
or quite an average person,

you wanted to have goods to
take into the afterworld.

You'd need things.

Because gold doesn't decay,

it was the perfect material
to cover a body with

'cause it would
last for maternity,

which is what they
hoped the body would.

- [Narrator] Egypt's
geology meant that

it naturally had large
quantities of gold.

But the amounts the
Egyptians desired

couldn't be found
in a river alone.

So they opted for a
different solution,

(dramatic music)

mining.

While they weren't the
first to mine gold,

the Egyptians certainly took
it to a new industrial level.

And without modern prospecting
methods, like remote sensing,

locating this so-called
gold of the mountain

was all down to a
simple realization.

- Finding gold for the Egyptians

rested on the
observation that gold

was often associated
with quartz.

So if you followed the quartz,

you were more than
likely to find the gold.

- [Narrator] To access it,
these ancient engineers

developed tools to help
them smash open the rock.

If a vein went deeper,
they would follow it,

digging tunnels and shafts.

- This would've been laborious,

backbreaking and
terrifying work.

- [Narrator] And the
scale of Egyptian

gold production
was unprecedented.

- One of the most
remarkable survivals

connected with gold
from the ancient world

is not a gold object,
but it's a map

that actually shows
the gold mines.

- [Narrator] One of the oldest
surviving maps in the world,

the Turin Papyrus.

(gentle music)

It predates equivalent
modern geological maps

by almost 3000 years and
is one of the first maps

to represent real
geographical content.

But it's what it reveals about

the organization of
Egyptian gold mining

which makes it
particularly incredible.

Created during the reign of
Rameses IV in around 1150 BC,

it records many places
in the Eastern Desert

where the Egyptian state was
mining and processing gold.

- Rather than it was
a case of sort of,

this is how you
get to the mines,

I think it was some sort of
bureaucratic use for the map

to keep a record of the
mines and maybe their output

or how many slaves
you had working.

- [Narrator] And when
archeologists in the 1980s

started to map ancient
Egypt's gold mines,

what they found was staggering.

Up to 250 of them scattered
across the Eastern Desert.

(dramatic music)

While today mechanical diggers

bear the brunt of mining work,

in ancient times, this
process was labor intensive,

requiring thousands
of paid workers,

or sometimes slaves to mine and
process the gold laden rock.

Over time, they
developed millstones

to crush small pieces of
quartz ore to a fine powder.

And, once ground, the
Egyptians devised various ways

to separate the
gold from the rock.

One of these was a technique
known as winnowing.

The finely ground gold ore was
shaken inside a dry blanket

to create pulses of air,

which separated the
rock from the gold.

This movement also
created a static charge,

which stuck the
gold to the fabric.

So when the blanket was opened,

the rock dust would blow
away, leaving just the gold.

- This is something they'd
used anyway with crops.

What you would use is
either a blanket or a basket

and you'd throw them up
and you'd just throw it up.

And the wind would
carry away the chaff

and you'd be left
with the wheat.

And it's the same principle
that they're using

to separate out really,
really small particles of gold

from small particles of dust.

- [Narrator] But winnowing
wasn't the only way.

Where water was accessible,
the Egyptians engineered

another even more effective
method, washing tables.

The ground powder
and water would be

poured down a slanting table.

Materials like sheep's
wool spread over it

would catch the
heavier gold particles,

while lighter rock
would be washed away.

And, to ensure no
gold was missed,

over time, sophisticated
circulation systems
were developed

to feed the runoff
back to the start.

- Wool has sort of residual
oils and lanolin in it.

So, as you are
washing in the wool,

what's happening in that
process is that the heavier gold

is being trapped
within the wool.

Now, once you've achieved that,

it's a very simple
step to drying it out

and then burning off the wool
to leave the gold residues.

- [Narrator] Also used
to catch gold in streams,

it's possible that the
use of sheep's wool

may even have inspired
the famous Greek myth

of Jason and the Golden Fleece.

(dramatic music)

Today, electric
powered machines now do

what thousands of
Egyptian workers once did,

crushing the rock and
washing it on shaker tables

capable of processing
up to two tons

of gold laden rock per hour.

The Egyptians' thirst
for gold was so great,

from as early as 2000 BC,
they even sought to control

their neighbors to the
south, in modern day Sudan.

Known in ancient times as Nubia,

it was the gold center
of the ancient world.

It's opulent objects reflecting
its wealth of natural gold.

Wall paintings record
how wars were fought

to control these
gold rich territories

and how Nubians
were made to bring

tributes of gold to the pharaoh.

- And we have one vulnerable
thing with the pharaoh saying

basically, he commanded the
chiefs of Nubia to mine gold.

I think he just couldn't
get enough of it.

- [Narrator] Almost 3000 years
ago, during the 12th dynasty,

the Egyptians even
built a system

of highly fortified mud
brick strongholds on the Nile

to police this trade and
ensure a constant supply.

- It was a huge enterprise,

from both ensuring you had
the access to the mines,

ensuring that the locals
were playing ball with it

and then the bureaucracy to
cope with it and deal with it.

- [Narrator] But to turn
raw gold into objects,

ancient engineers
needed to melt it

into more workable forms.

And there was a problem.

- So, to melt gold, you
need to be able to create

these really high
temperatures, right?

Now, if you're burning with
just a standard wood fire,

you wouldn't get
that temperature.

- [Narrator] An
ordinary wood fire burns

at only around 1100
degrees Fahrenheit.

Whereas gold's melting point

is several hundred
degrees higher.

So, to increase the heat,

the ancient engineers
turn to even older methods

devised for producing
another metal entirely.

(dramatic music)

From at least as early as
the sixth millennium BC,

in societies across the eastern
Mediterranean and near east,

techniques had been developed
for pottery production

and to melt other
metals, such as copper.

For these purposes, ancient
smith's created furnaces and,

instead of wood, they
powered them using charcoal.

- Charcoal is a
very, very good fuel.

Awful lot of heat in it

and it's very pure too so
it doesn't contaminate.

- [Narrator] As this
technology spread,

soon charcoal was
used to melt gold too.

Egyptian reliefs reveal
how the process was refined

using blowpipes to increase
the heat even further.

The first pipes were
likely just hollow reeds,

but, as these burned easily,

fire resistant clay tubes
began to be used instead.

However, they were still
not particularly efficient

and often required several
people all blowing at once.

- The problem with
using your own lungs

is that actually you
are already extracting

some of the oxygen from the
air that you're blowing out

and what the fire
needs is oxygen.

So just sitting
there with blowpipes

trying to get the heat up,

actually isn't the
most effective way

within which you want to
actually roast down that gold.

- [Narrator] So, for large
scale gold production,

the ancients hit upon a
better idea, the pot bellow.

To make the bellow,
animal hide was stretched

over a wide clay pot.

When the surface of the
hide was pushed down,

it forced air out
into the furnace.

To replenish the supply,
the hide was lifted

and air flowed in
through a valve.

Pot bellows could be
operated by alternate feet,

meaning that only a
single operator was needed

to produce a
continuous air supply.

- It's a very effective
way of doing it.

I mean the later
versions like the bellows

you used to see
beside every fireplace

with the sort of two
bits of wood you pumped,

I mean, that's just a
later version of it.

So it is not complicated,
but it's very effective.

I mean, I feel like
it's engineering

with very simple materials.

- [Narrator] Bellows
were major development.

Whereas blowpipes
could supply around

4.5 gallons of air per minute,

pot bellows could deliver
around 10 times that.

- The more air you
can get into the fire,

the hotter the flame.

- [Narrator] This greater
efficiency meant that

more and more gold
could be extracted

on an industrial scale.

Furnaces and bellows have
evolved through history but,

without these early inventions,

it's fair to say the
developments which shaped

modern industry may
never have happened.

- These early
breakthroughs directly led

to the invention of the
coke-fueled blast furnace,

which allowed you to smelt
iron and turn it into steel,

powering the
industrial revolution.

- In a sense, you could look at

the sort of a modern
motorcar factory

and sort of draw
a line right back

to the first guy with
a furnace for pottery

in wherever it was.

- [Narrator] Now the ancient
engineers could melt gold.

This opened up brand new
design possibilities.

(gentle music)

Melted gold could be made

or cast into
different solid shapes

through a technique known
as the lost wax method.

This involved first
making a model out of wax

and then entirely
covering it in clay,

except for a single hole.

When the object was
baked, the clay hardened

and the wax drained away.

Molten metal could
then be poured into it,

creating an exact
replica of the original.

Once the ancient
engineers could cast gold,

they could let their
imaginations run wild.

Gold could now be
made into jewelry,

created into objects to
adorn palaces and temples,

and even placed in tombs.

But, incredibly, the earliest
known example of cast gold

is from a tomb which
predates even the pharaohs.

Recent analysis of
finds discovered in
Bulgaria in the 1970s

could rewrite the history books.

Varna on the Black Sea is
home to the oldest surviving

funerary hoard of gold
objects on the planet.

Dating to around 4,550
BC, these were created

by a mysterious society
only a few centuries

after the first farmers came
to Europe from the east.

And it's unprecedented in scale,

with over 3000 gold artifacts.

- Little is actually
known about this society,

but the majority of the
objects were discovered

in just five graves
and that suggests

that they had an elaborate
social hierarchy.

- [Narrator] Although
Varna's gold objects

were long thought to
have been hammered

from raw gold nuggets,
recent analysis suggests

that some were in fact
cast from melted gold,

making it potentially the
earliest known example

of this technique
anywhere on the planet.

Many ancient cultures,

particularly in south
and central America,

where gold was abundant,

also produced gold
objects this way,

giving rise to legends
of entire golden cities,

which enticed
European explorers.

It's a method still widely
used in the modern world

with applications
in many industries,

not least gold
crowns in dentistry.

And it's one of the
most common ways

of mass producing jewelry.

Though now there's a twist,

instead of laboriously
carving wax by hand,

3D printers are now
often used to sculpt

the master mold in resin,

a modern update on
an ancient method.

- Today you go down
the high street,

the vast majority of jewelry
is produced by casting

'cause it's quick, it's
easy, it's efficient

and you can do it
on a huge scale.

- [Narrator] But to cast larger

solid objects out of
gold is expensive.

So, to make this precious
material go further,

the ancient engineers
turn to another

of gold's unique properties,
it's malleability.

- Pure gold is
infinitely malleable.

In other words, you
can carry on hammering,

bending, hammering,
and it never breaks.

- You can squash it, you can
take your little ingot of gold,

you can wallop it with a hammer

and it'll spread
out into thin sheet.

(gentle music)

- [Narrator] Ancient
Egyptian wall paintings

illustrate how
workers beat the gold

with a round stone
to make it flat.

And such gold had
a number of uses.

Famously, in one of
the 20th century's

most incredible
archeological discoveries.

Uncovered in 1922
by Howard Carter,

the tomb of boy
pharaoh Tutankhamun

was one of the most
lavish of all time,

containing over 5,000
objects, many of them gold.

But his funerary mask is
its glorious centerpiece,

only made possible because
of gold's malleability.

- Of course, one of the great
benefits of using sheet gold

to create something is
that it can be hollow.

So when I think of it, I mean,

Tutankhamun's mask is
obviously thin gold.

It's not solid head.

So you've got this
hollow inside.

So it looks more than it is.

- [Narrator] Created
from two sheets

softly hammered into shape,
the mask perfectly enclosed

the pharaoh's head
and shoulders,

giving him the golden skin
of a god for eternity.

- Only with gold could they
create such unparalleled detail.

The finest of facial features.

- [Narrator] But such
extravagant use of gold

was not practical
for anything less

than a pharaoh's funeral.

So, to make it go even further,

the ancient engineers
came up with a plan.

They simply kept hammering it.

- It's a very simple
mathematical progression.

The thinner you hammer the gold,

a bigger area you
can cover with it.

There must have been
a push to get the gold

thinner and thinner and thinner.

- [Narrator] The ancient
engineers discover

that hammering sheet
gold for long enough,

produced a gold foil, roughly
as thin as a newspaper page,

which they could then pin

or stick to an object
using an adhesive.

- You can pick it
up and wrap it round

whatever it is you are
trying to gild, so to speak.

- [Narrator] But
gold's malleability

could take it even further.

If this foil was beaten
between sheets of animal hide,

to stop it cracking, it
could be made so thin

it could create a
brand new material,

gold leaf.

(gentle music)

Gold this thin could be used
to gild much larger surfaces,

making objects appear as
if made of solid gold.

- Because it is so soft,
it is able to go into

every little interstice and
this makes it self adhering.

The two surfaces so
intimately bonded together,

they are becoming cohesive.

- [Narrator] The Roman
author, Pliny the Elder wrote

that a single ounce of pure gold

could be beaten out
into 750 leaves or more.

That's the equivalent of
under one micron in thickness,

over 70 times thinner
than a human hair.

Today, with modern methods,
gold can be made even thinner

for yet more diverse
purposes, such as makeup,

or even to decorate food.

- Goodness knows why
people would eat gold leaf

other than for
issues of prestige,

but it's an inert substance.

It's relatively safe to eat,

provided it's in
small enough particles

and it will pass out
the other end, I guess.

- [Narrator] In several
Eastern religions,

including Buddhism,
gold is believed

to symbolize knowledge or purity

and gold leaf is still
produced the traditional way

to cover many sacred objects,

from statues to
giant holy rocks.

It can even be used to
coat entire buildings

and make them appear as
though made of solid gold.

(dramatic music)

The Shwedagon Pagoda.

This Buddhist stupa,
or sacred ornament,

is believed to contain the
relics of Buddha himself.

And at over 300 feet high,

it towers above the city
of Yangon in Myanmar.

Whereas gold in other
ancient cultures

was often found inside temples,

this building is thought to be
solid and cannot be entered.

It's gold is likely all
displayed on the outside.

- The Shwedagon
Pagoda in Myanmar

is one of the most revered
shrines in Buddhism.

There's a legend
that golden nuggets

rained down from the sky

and they were used
to build the pagoda.

But, in reality, only its
surface is made of gold.

It is almost entirely
covered in gold leaf.

And as this material can't be
produced in very large sheets,

creating this effect
was a challenge.

Small copper tiles,
12 inches squared,

had to be individually covered.

Over 22,000 of
these gilded tiles

were then attached
to the pagoda,

creating the effect of a
single solid gold building.

But this presents a major
conservation issue today.

- The use of gold on
the Shwedagon Pagoda,

it isn't particularly effective.

I mean, it looks
absolutely amazing

and it glistens under the sun,

but it isn't
particularly resistant
to weather and climate.

So it does need replacing
quite regularly.

- [Narrator] The gold leaf
flakes off at such a rate,

it actually needs replacing
every four to five years,

But this is not a
problem at another,

more state of the
art, golden building.

The Metrimandir opened in
2008 in Auroville, India.

It's an edifice dedicated
to yogic philosophy.

Here, the architects
made their tiles

by sandwiching gold leaf
between plates of glass,

thus creating a more
lasting golden structure.

As goldsmithing spread
through the ancient world,

the innovation of
ancient engineers

led to even more breakthroughs.

Some of which are still
impacting us today.

- A lot of the ingenuity
in ancient jewelry

comes in things like how
it was fastened together.

And so you start getting some
quite interesting techniques

that are fundamental in
the history of engineering.

- [Narrator] The chain

and a spring.

Vital in almost every
modern industry.

But there's growing evidence
to suggest that these,

and other inventions,
may owe their origin

to ancient jewelry
manufacturing.

- The earliest examples I know
of the nut and bolt screw.

Which is fundamental if
you want to build a bridge

or a motor car or
anything these days.

That dates back to
probably late Roman times

when they're using
exactly the same principle

as a way to fasten some gold
bracelet, the screw thread.

- All these innovations actually

are so crucial to our world
today, but they only came about

because they wanted to find
new ways of wearing gold.

(dramatic music)

- [Narrator] But
the pursuit of gold

has not only been about
jewelry and decoration.

The real game changer came
with the invention of money.

And it was ancient engineers

who transformed
the element of gold

into the world's first
coinage currency.

- In the earliest days
there wasn't coinage.

I mean, in human history,

it's a relatively late
introduction, coinage.

There was obviously barter.

I make a loaf of
bread and I swap it

for the person next
door's cabbage.

And this sort of thing went on.

- [Narrator] But, as societies
became more sophisticated,

bartering systems
weren't enough.

- Bartering and
exchange is very limited

because it depends on both
sides wanting the same thing,

but money itself
changes everything

because it has its
own intrinsic value.

- [Narrator] Over time,
valuable metals started

to become a means
of basic exchange.

In Egypt, payments were often
made with large gold rings

and some cultures simply used
pieces of broken up metal.

But these early currencies
had their drawbacks.

- The problem with this was

is that the purity
of gold varied,

according to where
it had been mined.

It's important to remember that,

when gold is discovered
in the ground,

it's never pure,
it's always an alloy.

It contains other
metals such as silver.

So there was no standardization.

There was no way of guaranteeing

the content of the gold
that was being exchanged.

- [Narrator] Most
gold in circulation

until the end of the Bronze Age

varied between 70
and 85% purity.

So ancient engineers
began to develop

new ways of refining
gold to make it pure.

- Now we begin to find
references to gold

that's described as gold
of one or two times,

or three times in one case.

Because, if you melt gold, a
little bit of the other metal

will oxidize and go away.

So every time you melt gold,
it gets a little bit purer.

- [Narrator] To confirm
a piece of gold's value

before a transaction,
various methods

were also devised
to check its purity.

One method was a touchstone.

When drawn on with
a sample of gold,

these would show a
clear streak of color,

which could then be compared
to a reliable sample of gold.

Touchstones are quick,
easy, and portable

but, as they only check
the surface of an object,

they're also limited.

- If the surface has
been enhanced, then
you'll not find out

what the true composition
of the interior is.

- [Narrator] Fire assaying
was a more reliable method.

Like refining, it also involved

heating the gold to
draw out impurities,

which could determine
the actual gold content.

But fire assaying
also had drawbacks

as melting it destroyed
the original gold object.

Neither method was perfect.

But in approximately 550 BC,

around the time of
the ancient Greeks,

in a region of modern day
Turkey known as Lydia,

a local ruler in its capital,
Sardis, found a solution.

Creating the world's first
standardized currency.

Earlier Lydian Kings had
created a basic coinage

using electrum, an alloy
containing both gold and silver.

But a king called
Croesus created a new,

more reliable monetary system

consisting of gold
and silver coins

with a standardized purity.

- This was crucial for the
development of gold coinage

because you knew exactly how
much gold each coin contained.

- At first, Croesus
used fairly pure gold

panned in nearby rivers.

But when this ran out, he
started to import less pure gold

and turned to his engineers

to find an effective
way to refine it.

- He hasn't got any
intrinsic, pure gold anymore.

So he has to call in the
lads and sort of say,

we've got a problem, we've
gotta get to a constant purity.

- [Narrator] In order
to remove the silver,

Croesus' engineers developed
a more sophisticated

way of refining,
known as salt parting.

(dramatic music)

A dry cement of brick
dust mixed with salt

was laid inside a
pottery container,

thin sheets of impure
gold were then laid on top

and layered with the cement
until the pot was full.

It was then heated at a low
temperature for several days.

During the heating, salt vapors
would attack the impure gold

and remove the silver content.

The result, almost
99% pure gold.

Coins were then
produced at a set weight

of just under 0.3 ounces.

And with each coin punched
with a lion, Lydia's emblem,

this currency could be
traded with confidence.

By harnessing money,
Croesus became

one of the richest
men in the world.

Giving rise to the
expression as rich as Croesus

and turning Lydia into the
business capital of the world.

- I think Croesus' sort
genius, if you like,

was to realize that,
if you refine this gold

before you made the coinage,
you would have a standard

and other countries
would recognize it.

- [Narrator] Over time,
coinage allowed bigger

and more sophisticated
trading markets to develop.

- The invention of money
absolutely transformed society.

It changed the way
we go about business.

It changed the way that
we relate to each other.

(gentle music)

- [Narrator] The
invention of money created

the modern financial
world as we know it.

Gold and silver were
the basis for currencies

around the planet for centuries.

Nowadays, they have largely
been replaced by coins

with lower intrinsic value.

But many countries still
have a gold reserve

kept under lock and
key just in case.

- It's a finite resource
and, in that sense,

it always holds its value.

I mean, in times of political
and financial crisis,

that's what you want
in your reserves.

You don't want pieces of paper
with money stamped on them.

You want bars of gold.

- [Narrator] Today, gold
is often exchanged online

by people who have
never even seen it.

It's closer to cryptocurrency
than real money.

But unlike some crypto coins,

digital gold retains its worth.

While monetary values fluctuate.

But real gold was what
counted most in ancient times.

(dramatic music)

For the ancient Romans,
gold coinage was vital.

As the empire, expanded the
Roman emperors needed money

for a number of reasons,
for paying soldiers

and to create a unified empire

trading under a single currency.

But coinage also had
another function.

- Coinage became really
important as a propaganda tool.

You could actually put
your face on the coinage.

And that was so important
because it reminded everyone

who was in charge.

- [Narrator] And gold coinage
had a very exclusive purpose.

- It's the value of this coin,

which enables the Roman
Republic and later,

the Roman emperors to
bribe, effectively,

anybody they want to
bring within the empire.

- [Narrator] With demand
for gold increasing,

the Romans took
it from anywhere.

Often seizing it from conquered
peoples and melting it down.

But they also came up
with inventive ways

to get their hands on
greater supplies of gold

from the ground.

In the newly conquered territory

of northwest Spain,
at Las Medulas.

Brilliant Roman engineers
supercharged their mining.

Using a technique
called hushing.

Where water power was
used to blast away

vast quantities of earth.

- Water can do a
huge amount of damage

to any hillside, mountainside.

You know, its power of
pressure, its surge power,

it can destroy large
forms of land mass.

Which is, of course,
what miners want.

They want to kind of
remove all of that material

so you can extract
the metal ores.

- [Narrator] To ensure a
large enough supply of water,

the Roman engineers used

one of their most
famous innovations.

- The Romans were
outstanding water engineers,

and one of their
finest inventions of
all was the aqueduct.

- [Narrator] Aqueducts
were vital for Roman cities

transporting fresh water

for drinking, bathing
and sanitation.

To ensure a constant flow
of water at Las Medulas,

the Romans expertly
designed several aqueducts

to transport it from as
far away as 90 miles.

Built to hug the contours
of the mountains,

they maintained a very
gradual downward gradient,

bringing the water
to holding tanks

above areas of
rich gold deposits.

These aqueducts
could deliver between

1.7 and 3.2 billion cubic
feet of water a year,

the volume of over 20,000
Olympic swimming pools.

(gentle music)

To reach gold deep
inside the rock,

a network of shafts and tunnels
would be dug down into it.

And, when all was ready, the
sluice gates were opened,

releasing water into
the shafts and tunnels.

Which blew the rock face
clean off through sheer force.

- The Romans were masters
of controlling water.

They understood the
volume, the velocity.

They knew exactly how to
use it and, in effect,

this is the equivalent of
blasting in a modern quarry.

- [Narrator] But
the Romans didn't

only use water for mining.

They also used it to pioneer
new ways to process gold.

At another ancient
Roman gold mine,

in Dolaucothi, west Wales,

a unique monolith has
long caused a mystery.

- It's called the Pumsaint
Stone, Five Saints Stone,

'cause the story is, you know,

that these five saints,
sort of, feeling tired

went to sleep against this stone

and created these
five depressions.

- [Narrator] But clues in
the surrounding landscape

revealed its possible function.

Telltale water channels
and the remains

of a probable water wheel.

Archeologists realized the
stone had to be the base

of an early type of trip hammer,

a device used to grind
gold bearing rocks.

In order to power a trip hammer,

flowing water would
rotate a water wheel,

which in turn drove a cam shaft.

The cam shaft turned
rotational movement

into vertical power,
driving a series of stamps,

which pounded the
rock into tiny pieces

against a stone anvil.

The basis for the
modern car engine,

cam shafts were always assumed
to be a much later invention.

But the discovery of
the Pumsaint Stone

turns that theory on its head.

- Up until its discovery,
we always thought

that kind of technology
was only around

in the medieval period.

But this stone
serves as an anvil

and it dates firmly
to the Roman period.

I mean they really
were innovators

in the use of water power.

- [Narrator] Such
sophisticated methods led to

a massive expansion of the
gold industry in Roman times.

- Roman gold mining was
of an industrial scale

and you can find it across
the entire Roman empire,

all the way from
Britain through to Syria

and north Africa, in
Greece and Turkey.

- [Narrator] But this
came at a great cost.

(gentle music)

The legacy of these
hydraulic mining methods

is laid bare in the
landscape of Las Medulas.

During its 250 year
operation, to reach gold,

the Romans removed almost 18
billion cubic feet of rock.

- The water had been released
by the Romans is such velocity

and in such volume,
it's carved canyons

through the mountain side.

- [Narrator] This
process made Las Medulas

Rome's principle goldmine.

But it devastated the landscape.

It's easy to see why the
Romans may have named this

ruina montium, or the
wrecking of mountains.

(gentle music)

Today, some modern
mining practices can be

just as catastrophic for the
environment and for mankind.

Heap leaching is a processing
technique using cyanide

to dissolve out particles
of gold from its host rock.

It can process millions of tons

of gold laden rock every year,

but it has the
potential to cause

devastating environmental issues

as the cyanide is
prone to leaking,

polluting rivers and poisoning
human water supplies.

Throughout history,
we've sought to mine gold

from deeper and
deeper underground.

Often at huge human expense.

An ancient technique
called fire setting

was used right up
to the Middle Ages.

It involved a minor having
to light a fire underground,

it's heat would then
weaken and crack the rock.

(dramatic music)

But it was dangerous
and unpredictable,

often leading to
sudden collapse.

An invention of the 19th century

revolutionized mining, dynamite.

The brain child of Swedish
chemist, Alfred Nobel,

dynamite used 19th
century advances

in chemical engineering
to blow apart rock.

It was more controllable
than fire setting,

allowing miners to
lay the explosives

and then detonate them
from a safe distance.

And it allowed them to access
more gold than ever before.

Gold mines could now run so
deep that, in South Africa,

the miners of the 1886 gold rush

could access the
Witwatersrand Basin,

the world's largest
known gold field.

These mines have since become

some of the most
productive on Earth,

turning Johannesburg into the
gold capital of the world,

allowing South Africa to create

the deepest mines on the planet.

- The Mponeng mine
in South Africa

is the deepest gold
mine in the world.

It is ridiculously deep.

It is four and a
half times the height

of the tallest building in
the world, the Burj Khalifa.

(dramatic music)

- [Narrator] But
such a wealth of gold

has not always been
possible to find.

Despite sophisticated
mining methods,

gold was still rare and
valuable in ancient times.

So, to satisfy high demand,

engineers came up with another
solution, gold plating.

To make this, the
ancient engineers
turned to another metal

with a very unique
property, mercury.

Also known as quicksilver,
mercury's speed and fluidity

were why the Romans named it
after their messenger god.

But it was what
happened when it came

into contact with gold
which most intrigued them.

- When liquid
mercury touches gold,

it literally eats the gold and
it binds chemically with it.

- It amalgamates.

So what you wind up
with is what is known as

butter of mercury
or butter of gold.

- [Narrator] Ancient
engineers discovered

that this pliable
butter could be used

to coat other cheaper metals
like silver or copper.

When heated to 650
degrees Fahrenheit,

the mercury burned away,
leaving just the gold,

now bound to the other
metal underneath.

- This was the first
form of gold plating

and it was so effective
that it was widespread

right up until the 19th century.

- [Narrator] But mercury
carries many health risks

for those exposed to it.

Nowadays, new, safer
and more sophisticated

plating techniques have
gradually been introduced.

- Modern gold plating
is extraordinary.

It's high science and
there's even debate

whether you should actually
be able to call it gold plate

'cause there's so little
actual gold there.

- [Narrator] These plating
advancements means that gold

is now finding brand
new applications,

vital ones for our
changing world.

It's flexibility and
high conductivity

make it a useful material for
key electrical components,

like circuit boards
and contacts.

- It can be used on connection
boards, in SIM cards,

in laptops, in so many
devices and gadgets.

- [Narrator] Its ability
to be coated very thin

keeps manufacturing costs low,

while it's non corrosiveness
means our electronic devices

are less likely to let us down.

- What many people don't realize

is that gold is
used in just about

every electronic device
that we use today.

So we need gold to live
the lives that we lead.

- [Narrator] And, as it's
also highly reflective,

such thin gold has become
vital for space exploration.

Used since the first men
stepped foot on the moon,

it protects sensitive equipment
from the sun's radiation.

- It's now possible
to get gold so thin

that you can see through it.

So it's even used to
coat astronauts' visors.

- [Narrator] And
gold's reflectivity

has also made it vital for
a very special mission.

(gentle music)

1.69 ounces of the purest
gold now coats the mirrors

of the James Webb telescope,

which launched in
December, 2021.

- This is not a
normal telescope.

This is the most sophisticated
engineering you can imagine.

They're going to the
very depths of space.

- [Narrator] Gold's
exceptional ability to reflect

should allow this honeycomb of
mirrors to focus enough light

to image some of the
earliest stars ever created.

Perhaps even the very stars
which once formed gold itself.

(dramatic music)

Gold has come a long way
since ancient peoples

first panned for it
in rivers and streams

with their bare hands.

Modern advancements in gold
mining and manufacturing

stand on the shoulders of
these ancient engineers.

Their innovations have
prompted us to dig deeper,

to purify and refine

and to explore gold's
infinite possibilities.

Without them, and this
most mesmerizing metal,

the world economy, our societies
and deep space exploration

may not exist as we know it.

(dramatic music)