All language subtitles for Star.Clock.BC.Antikythera.Mechanism.1080p.HDTV.x264.AAC.MVGroup.org.eng

These men have a challenge,

build a computer that uses no electricity,

only metal and wood.

And it must do the seemingly impossible,

calculate the movements of the heavens,

the waxing and waning moon, the sun, the planets.

Predicting these complex patterns

requires sophisticated calculations,

but it's already been done.

Over 2,000 years ago in Greece,

someone invented a hand-cranked computer

that could decode the solar system.

The ancient device isn't much larger than a shoebox

but it holds dozens of interlocking gears

and carries multiple synchronized pointers

on its front and back.

Our main four spoke wheel, where we have--

Chris Weisbart and Maris Ensing

have decided that the best way to understand

this 2,000-year-old astronomical computer

is to build one like it.

It might be really interesting

to make it slightly larger and really expand it out

so people can really see how the gears mesh together.

Okay, how much time do we have for this thing?

Thinking two weeks.

Oh, come on. (laughs)

Get real.

I know, I know.

It's probably gonna--
Have you seen,

have you seen this diagram?

You say how long?

Two weeks.

Chris is the tech guru

for the Natural History Museum of Los Angeles county.

Mesh with that 127.

Maris Ensing is president of Mad Systems,

a Los Angeles-based company that builds exhibitions

for museums all over the world.

They're going to base their model

on X-rays from the original

and diagrams founded on decades of research,

studying its complexities.

Its precisely-meshing gear teeth...

We need to sandblast these wheels

and see if we can clean 'em up.

And the understanding of the skies

encoded in them.

The ancient Greeks were hungry for knowledge.

They produced sophisticated art

and architectural masterpieces like the Parthenon,

great thinkers like Socrates and Aristotle,

and important advances in trigonometry,

geometry, and astronomy.

What was important for them was gaining knowledge,

gaining an understanding of the cosmos,

using technology to elevate the spirit by getting closer

to the gods and closer to the nature of things.

Their pantheon of gods

ruled over a perfectly-ordered universe

and the gears in this ancient computer

were a mechanical celebration of it,

a way to understand the planets, stars, and moon

as they swirled above.

Within a few hundred years, though,

ancient Greek civilization would die out

and the knowledge that made this computer

would die out with it.

(mystical music)

Only one of these devices exists

and it was found completely by accident.

110 years ago, Greek sponge divers anchor

near a small, barren island in the Aegean Sea, Antikythera.

One man puts on his diving helmet and drops down.

He soon surfaces, horror-stricken and ranting.

Apparently terrified, gabbling about a pile

of dead naked women that he'd seen on the sea bed.

So the captain went down to have a look for himself

and realized that these were not naked women but statues,

bronze and marble statues from the ancient world.

It turned out that this was an ancient wreck that held

one of the most important hoards of ancient treasure

that had ever been discovered up until that point.

the priceless artifacts are proudly displayed

at the National Archeological Museum of Athens in Greece,

but hidden among them is something odd.

It looked like just a piece of battered rock

but inside, there were gear wheels, pointers, inscriptions.

This looked like some sort of clockwork machine,

which just shouldn't have existed in the ancient world,

according to historians of the time.

These were the earliest such gears ever found,

by over 1,000 years.

The ancient Greek device is now known as the

Antikythera Mechanism after the island where it was found.

Now, more than a century after its discovery,

researchers are still trying to understand what it does.

Now comes the clever bit

where the machine calculates a tool path--

The best way to understand

the mechanism is to build one.

And see how this cut is progressing.

See it?

Oh, wow.

That's the nozzle right there, moving along.

They'll build what's called

a space model out of wood and acrylic

to get a better handle on the design.

They're using tools that craftsmen 2,000 years ago

couldn't have imagined.

So what's happening right now is water

shooting out of the nozzle at 50,000 psi,

getting fed with sand is shooting through the plywood

that's making the cuts, really precise.

Having the right tools makes all the difference.

Yeah.

Put that in and we'll start building that space model

so we get a feel for what's actually going on.

This sheet of blue acrylic

will support the model.

Wooden parts will wear out quickly,

but they provide a cheap and quick way to figure out

the spacing between more than 50 interlocking gears.

So we have to make sure that the distance are accurate

or else the gears won't match properly.

(low, intense music)
(machinery humming)

All right, let's see how this thing runs.

Hopefully that will fit.

Look at that.

Nice.

It's a little bit wobbly, but it should be fine

for what we're doing.

So here's our first gear.

The center wheel runs along a central shaft

and has 64 teeth.

As it turns, it sets of a chain of gears

that run the entire mechanism.

With only three gears completed,

they've got a long way to go.

So now we have three gears.

How do we move onto the larger device.

(chuckles) To the next 40?

Yes.

Um... (chuckles)

Even with this high-tech equipment,

creating complex meshing gears is an arduous task.

But without these gears and people

with the patience and skill to create them,

our world would not be the same as it is today.

Gears are important because it was

this kind of mechanism that drove not just the invention of,

obviously, clocks and watches, but a lot of the machinery

that was fundamental to the Industrial Revolution.

Without gears, we'd have no cars, trains,

planes, factories, or machines, from giant assembly lines

to fine focus adjustments on telescopes.

Before the discovery of the Antikythera Mechanism,

the oldest known complex gear trains were found in

European clocks from the 1400s, when the Middle Ages

were just giving way to the Renaissance.

But this ancient Greek computer is 1,000 older

and made up of gears that are just as complex

as those found in Medieval clocks.

The link is absolutely direct

because this is a clock-like machine, this computer.

It was Dr. Derek Price of Yale University

who first called the world's attention

to the Antikythera Mechanism's true historical importance.

Price is the pioneer to whom we all owe a huge debt.

Price is the first man who really looked at this instrument

closely and with some understanding of what it could do.

Before Price, very few people were prepared

to think seriously about the Antikythera Mechanism

because it was just too far removed

from what scholars were comfortable with.

A scholar studying the history of science,

he sets out in 1958 to analyze those ancient Greek gears

and learn their purpose.

Inscribed on the front of the device,

Dr. Price discovers the word hil-ay, meaning claws.

This is the Greek names for one of the zodiac signs, Libra.

Further around the dial, two letters are legible

from the Greek name for Virgo.

Price soon realizes that one of the front rings is divided

into the 12 constellations that make up the zodiac.

There are many constellations in the sky,

but the 12 in the zodiac serve as the background

for what's known as the ecliptic,

the sun's path in the sky over the course of a year.

If you very systematically track the sky,

you can figure out that the sun appears to be traveling

around the sky and through some of the constellations

that we map up there.

Price's team creates a series

of X-ray images so he can see

the inner-workings of the device without destroying it.

By examining the X-rays, he deduces

that five turns of a side handle

would have moved a pointer, symbolizing the sun,

through one full cycle or one year.

(mysterious music)

Having worked out the gear spacing in wood,

Maris and Chris switch to metal for the final model.

So the first thing we have is the rotation of the sun.

So we put the pointer onto the sun

so that we can show the rotation of the sun.

It goes through the zodiac,

so you get one rotation for one year.

The main drive wheel

pushes the sun pointer around the zodiac dial

and also sets in motion a series of gears

that calculate the movement of the moon,

represented by a second pointer.

Then the second one you put on is the moon pointer

and this is something called a coaxial shaft.

And what we have here is an outer sleeve

and then here we have an inner shaft.

So the outer shaft, the sleeve is on the sun,

and then the inner shaft, which is this guy,

is being rotated by this gear over here

and this shows the moon.

The mechanism computes

the movement of the moon in relation to the sun.

Turning one side handle moves both pointers

at their proper speeds around the zodiac dial.

Like virtually every other early civilization

around the world, the ancient Greeks

paid close attentions to the comings and goings of the moon.

Everybody counts the days by the moon.

They bundle the days by the moon.

Everybody measures the rhythms of nature

in conjunction with what they see the moon doing.

The moon operates as a basic timekeeper.

But predicting when and where in the sky

the moon will appear is not simple.

That's because the moon circles the Earth

while the Earth orbits the sun,

each on its own independent schedule.

The trouble is, these two different cycles don't mesh.

You don't get a whole number

of moon cycles in a single year.

That makes calendars that incorporate both messy.

A primary goal of ancient Greek astronomy

was to reconcile the lunar and solar patterns

and create a sensible calendar.

It takes approximately 27 days and eight hours

for the moon to appear at the same point in the sky

when compared to the constellations in the zodiac behind it.

This is called the tropical month.

But it takes approximately 29 days and 12 hours

for the moon to go from full moon back to full again,

which happens when the Earth,

sun, and moon, are all in a line.

A Greek astronomer named Meton from the fifth century, BC,

is credited with figuring out that the sun and moon

will return to the same points in the sky

relative to one another and the constellations of the zodiac

every 19 years.

It's called the Metonic cycle.

And correlated to that, in every 19 solar years,

we have 254 tropical months.

That is the formula,

and it's embedded in the Antikythera Mechanism.

So the Greeks were trying to get this ratio

of 254 to 19, and here's one way to do it.

It's 254 teeth on this large gear

and 19 teeth on this small gear.

This is how gears can do math.

Every 19 rotations of the big wheel

produces 254 rotations of the small wheel.

It's the movements of the sun and moon, rendered in metal.

This needs to mesh correctly all--

It's easy in theory, but not in practice.

'Cause with these large gears, getting it correctly set

on the shaft, you get a little bit of sideways motion,

and before you know it, you're no longer

mating with your other gear.

There is a better way of getting this same ratio

that actually looks a little bit more complex,

and this is one of the interesting thing

about the Antikythera Mechanism, is that they really thought

about how to make it small enough and how to make this work.

The Antikythera Mechanism

doesn't contain one gear with 254 teeth and another with 19.

It uses a much more sophisticated way

of representing the Metonic cycle.

(relaxed classical music)

X-rays of the crusty metal reveals

six small gears connected to the main drive gear,

what's known as a gear train.

(relaxed classical music)

The 64 drives this wheel

which sits on the same shaft as that one

which drives this guy over here.

So you're saying the combination of the 64-toothed gear

driving the 38-tooth gear, which then drives this gear,

which then drives this gear, which outputs

the same ratio as the 254--

So basically, it's very similar to simple math.

Instead of doing one division, you can do it in chunks.

Starting with the

64-toothed gear wheel at the center,

the Antikythera mechanism used six gears

to create the ratio of 254 over 19.

Together, these ratios create the formula,

254 months in 19 years.

(relaxed classical music)
(gears clicking)

And you can see that we're now using

multiple gears to get to the same ratio on the Antikythera.

So by keeping it compact,

you're making life a lot easier for yourself.

The ancient Greeks

made their computer portable.

Not only were these people craftsmen,

which in itself is an amazing build,

but when you see things like that happen, it's stunning.

A compact calendar computer

over 1,000 years before its time.

Some have argued that it's so complex,

the Greeks couldn't have made it at all.

There are even some who say it must have been created

by aliens.

(mysterious music)

When the Antikythera Mechanism was first discovered

in a 2,000-year-old shipwreck,

people thought there must have been a mistake.

Some people just thought it was a hoax, you know,

it couldn't possibly be from the ancient world.

Or perhaps it had been accidentally dropped

on the wreck sites much, much later on by chance.

A bestselling book in the '60s

suggested that highly advanced aliens

must have brought it to Earth from outer space,

an assertion dismissed by other scholars.

This business of Erich von Daniken and other people

like him, hypothesizing that anything interesting or complex

from antiquity was brought by aliens is just ridiculous.

You've substituted a more complex hypothesis,

these aliens, for which there's really no other evidence,

for a less complex hypothesis which is,

ancient people were smart and hardworking.

Why not go with the simpler hypothesis?

But the sophistication of the ancient device

still comes as a shock to modern engineers.

We're thinking of them as primitives.

They were not.

There were people, there were people there

that had an incredible mind in order to be able to

conceptualize a solution to some of these problems.

Chris and Maris are using

modern tools to make an oversized model.

They want it to function like the original,

not necessarily look like it.

Michael Wright on the other hand,

has built two models of the Antikythera Mechanism

that are the same dimensions

and use similar materials to the original,

and he made them by hand,

as the original craftsmen would have done.

(mellow techno music)

Wright is an accomplished clock maker,

as well as a historian of technology

and former curator of Mechanical Engineering

at the Science Museum in London.

He's probably done more than any other individual

to bring the Antikythera Mechanism back to life.

More than 30 years ago, Michael Wright read a book

by Dr. Derek de Solla Price...

That wheel is the one you see here.

Who first drew the world's attention

to the ancient Greek computer.

But Wright does not agree with all of Price's conclusions.

There were points in which he contradicted himself.

There were points in which he stated things in writing

which were clearly, which clearly did not match

with what I saw in his photographs.

There were things that just didn't make sense at all,

certainly didn't make sense to me as a practical person

imagining building the instrument.

On a cold spring day, author Jo Marchant

meets with Michael Wright in his London studio.

My modern hand tools are probably a little quicker

and easier to use than the Hellenistic mechanic's tools.

In particular, I have the benefit of using

a screw vise to hold work still and he probably didn't.

Once a circle of brass has been cut,

Wright uses Euclidean geometry,

invented by the ancient Greek mathematician, Euclid,

to divide the circle into even segments.

Once he divides the circle, Wright makes marks,

which he then files into teeth.

(metal squeaking)

Building the mechanism by hand

requires a huge investment of time.

What it seems to me is they've gone to so much trouble.

All of this work has gone into this

and it just gets across the importance of the heavens

to them, the importance it must have played

in their lives of understanding how things were arranged.

And this isn't something you'd just knock off

in a few hours on a whim, is it?

Well, no.

My 1,000 hours probably translates into

the best part of a year's work

for a man with less efficient tools.

In other words, it's quite an investment in labor

and it's quite an investment in materials,

making this thing, so somebody really wanted it.

In the 1990s, Wright goes to Athens

and takes pictures of the mechanism

using a technique called linear tomography.

This involves a device that he has made himself

which moves X-ray focus just 1/10 of a millimeter at a time.

He takes over 700 separate X-ray images

of the Antikythera's inner-workings,

each photo showing a separate slice.

These images provide much more detail

than the radiographs taken by Dr. Derek Price's team.

Once he downloads them onto his computer,

Wright notices something astonishing,

the 2,000-year-old gears in the Antikythera Mechanism

show no alterations, no modifications.

Wright is a skilled craftsman,

but making his model is a learning process.

When you look at custom build clockwork,

you very often find alterations have been made

as the clockmaker went along.

I'm talking of 17th, 18th century clockwork.

But in this, there's nothing like that.

The maker knew exactly where he was going.

Whoever made the Antikythera Mechanism

got it right the first time.

He must have had years of practice.

This means there must have once been many similar devices.

But now there is only one.

One explanation could be the fact

that it was made mostly of bronze.

Bronze was a valuable metal.

It could have been used for weapons or cooking pots

or statues or jewelry or all sorts of different things

and it was often, through various periods of history,

very scarce, so anything that was made of bronze,

would, over the centuries, have been melted down

and reused and made into something else.

In the same tradition,

Michael Wright has used recycled metal to make his model.

You can see that I made this model

out of scrap metal.

Somebody--
It's a door plate.

Somebody or other's registered office.

Well, that would be traditional, wouldn't it,

using recycled metal?

Recycled materials, yes.

Wright's experience making models

of the Antikythera Mechanism has given him

another theory as to why more originals cannot be found.

So this would have required quite a bit of maintenance

to keep it running?

I believe so, and I think that's part of the argument

for why no others survive.

You can only use a gadget like this for so long

before it breaks down and then you take it to the mechanic

and he'll be just like your motor mechanic.

He'll go, (sighs) and he'll fix it up for so many times

and then finally, he'll say, I can't do it anymore.

I'll take it in part exchange.

Buy a new one.

But back in Los Angeles,

Chris and Maris aren't trying to reproduce

the original gear making techniques.

So let's try and get this thing in here.

That shaft comes forward, yeah.

They're more interested in figuring out

how the thing worked, the way it used gears

to mathematically process useful information

about events in the night's sky.

(mumbles) gearing short about that

and I cut the plate based on all the different

gearing cycles that we had to have.

They've already reproduced the gears

that calculate the movements of the moon,

but simultaneously calculating the moon's changing phases

adds a whole other layer of engineering complexity.

Not only did they have the sun and moon pointer,

but they put another part of mechanism on there

that requires a miter gear, which I have here.

To display the waxing and waning moon,

the Antikythera Mechanism used gears on the sun pointer

to rotate the moon pointer.

Maris uses a modern solution, a miter gear,

to get the same result.

As a museum curator, Michael Wright has seen

the phases of the moon represented on astronomical clocks

from the late Middle Ages, but the Antikythera Mechanism

seems to have used the concept some 1,400 years earlier.

This miter gear controls the speed at which

that guy rotates and then there's a couple of other

really interesting effects that are minute

but really matter if you want to get this absolutely right,

and that is something we'll get to in a minute.

Chris and Maris have completed

less than 1/3 of their analog computer

based on a design from 2,000 years ago.

The original hardware is from ancient Greece.

But the software that runs this computer

comes from an even earlier culture.

(hammer tapping)

Good enough on the first gear is good enough.

Good enough on the first gear when you're driving

30 other gears, believe me,

it's not that easy to accomplish.

With each additional gear,

the need for precision increases.

You learn right away what you can slop

and what you can't slop.

The original Antikythera Mechanism

isn't just an impressive feat of ancient engineering,

it's based upon hundreds of years

of astronomical observation.

Thousands of years ago, Babylonian priest astronomers

carefully recorded what they saw in the night's sky.

Centuries later, those records passed to Greek astronomers

who used that knowledge to create

geometric models of the solar system

and predict future alignments of the planets and stars.

One thing we find in the Antikythera Mechanism

is a kind of blending of these two traditions.

Greek concern with geometrical structures

and mechanical representation,

but the basic mathematical periods,

which are borrowed from Babylonian astronomy.

Dr. James Evans believes

the Antikythera Mechanism was created

in the period when Greeks were borrowing ideas

from Babylonian astronomy, about the second

and early first centuries, BC.

Some believe it's possible the mechanism

may have been created just after this period,

when one of the most famous Greek thinkers

was alive and working, Archimedes.

Archimedes wasn't just a theoretician,

but a practical inventor.

He built water screws and huge imaginative war machines,

like a giant claw that capsized enemy ships.

Recent research suggests that there are clues

linking Archimedes to the Antikythera Mechanism.

For example, the names of seven of the months

used on the device come from Sicily,

which is in the same region as Archimedes' home province.

Different calendars were used in different parts of Greece

and these month names do seem to be quite similar

to those that were used in Sicily at the time.

Also, we know that Archimedes was interested

in gears and how they inter-meshed,

and his father was an astronomer.

So perhaps he had an interest in the heavens.

There is even a written account

stating that Archimedes built a device

that had some of the same functions

as the Antikythera Mechanism,

but Archimedes was hardly the only genius of ancient Greece.

There are others who could have created

the revolutionary device.

I know that a lot of people think that

Archimedes himself might have made this, but I have

this argument that he couldn't possibly have done so,

not because he wasn't smart enough.

Archimedes was clearly smart enough

and he clearly had the math,

but because at the time of Archimedes,

nobody had yet developed the planetary models

upon which this device is based.

In particular, the Antikythera Mechanism

accounts for the constantly changing speed of the moon.

It's a subtle effect that few casual observers

in the 21st century even notice.

Over the course of a single month,

the moon gradually speeds up and slows down

in its path across the sky.

The geometrical formula to describe the moon's

variable speed was worked out by a man named Hipparchus,

the founder of trigonometry.

He worked in the second century, BC,

100 years after Archimedes.

Without Hipparchus or somebody like him,

the thing could not have existed.

Hipparchus played the key role

in taking the translated Babylonian data,

transforming it into a set of models

that actually worked to actually predict

the positions of the sun and the moon.

The moon moves at changing speeds.

How would they have done that in gearing

and program that into--

That's the interesting thing, isn't it?

It's one of the most intricate sections

of the entire device, so intricate

that Chris and Maris decide to go back to wood

before attempting to make it in aluminum.

Now, we start to get towards

the first complex part, and that is

this whole mechanism of these quad 50 gears.

There's something weird going on there.

They're trying to understand

a cluster of four 50-toothed gears

that Maris calls the quad 50.

Okay, so what is happening is

if we're driving the 64, which drives...

The 38, over here, which drives the 223 gear wheel,

so we've got four of these 50 gear trains

that is going to run somewhere behind here.

Why would you have gears with the same amount of teeth

meshing with each other?

Well, that was something that I've been thinking about.

And from the various references that I've found,

what it would appear to do is to offset that second gear.

The first and the second gear

move at a one to one ratio, but the second gear has a pin,

which fits into a slot on the third gear,

which is not on center.

We should be able to get that offset,

which means that we can approach an elliptical movement.

In other words, for part of the rotation, it will speed up,

and for part of the rotation, it will slow down,

like the track of the moon around the Earth,

with is pretty incredible,
Yeah.

Not only that they thought of doing it,

that they had the measurements,

but that they actually figured out

a mechanical way of doing this,

and now we find this year, this has got a big hole in,

and we drop that on here,

and this one should mesh nicely with this center gear.

See it?

Mm-hmm.

Nicely might be an exaggeration on this model,

but it's close enough.

Now what we do is we drop this gear onto this shaft

and we take this pin and let it drive it with this pin.

So what we now do is we bang the center gear in

on the center shaft and now what you're going to see on

this gear is that these teeth go slower

at the top at the moment and then now out of alignment,

so you can see these teeth move with respect to each other,

so now we no longer have a regular rotation.

We now have a rotation that has

a higher speed and a lower speed on ever cycle.

And if we shove this on where we are here at the moment,

here we go.

I think we got that part licked.

We're good.

Great, let's try it out of metal.

Let's do the real thing.

(upbeat music)

Having worked out the puzzle in wood,

they attempt to remake the complex lunar gear train

in aluminum and then integrate it into the final model.

It's a loop, but at the other side of the loop,

you're getting the speed change that you need.

That's right.

So what is happening is that you are putting

circular motion on here and continuous circular motion,

and here you're getting an advance and a retard,

and that's what the clever thing is about this mechanism.

Thanks to the pin and slot mechanism,

continuous motion goes in a steady crank of the crown wheel,

and irregular motion comes out, a moon pointer

that speeds up and slows down as it circles the dial.

It's an ingenious solution to a tricky mathematical problem.

I can't even imagine how somebody wakes up

2,100 years ago and goes, like,

I know what I'm doing, I'm gonna take two of these gears

and I'm gonna run one in front of the other

and put a pin and a hole, a pin and a slot in between,

and I'm just gonna make it work and that'll be fine.

How do you get there?

How does anybody get there?

The Antikythera Mechanism accurately computed

the moon's variable speed over the course of a month,

even though the Greek astronomers didn't understand

what was actually happening in the heavens.

They believed the heavenly bodies moved

in perfect circles around the Earth.

Today, we know that's not true.

Only the moon orbits the Earth,

which spins on its own axis while orbiting the sun.

The orbits of the Earth and moon are not

perfectly circular, but slightly stretched.

Its rate of motion changes because the moon's orbit

is not circular, it's actually an ellipse,

a little bit out of round, and that means

there are times in its orbit

where it's moving a little bit faster

and times when it's moving a little slower.

The closer an orbiting object is

to its parent body, the faster it moves.

This is true not only for the moon

as it moves around the Earth, but also for the Earth,

which speeds up as its orbit nears the sun.

From our Earthly vantage point, however,

its seems it's the sun that's speeding up and slowing down

over the course of a year.

Dr. James Evans of the University of Puget Sound

in Washington State has studied

high resolution photos of the mechanism.

He believes he knows how the Greeks

represented this so-called solar anomaly,

the sun's changing rate of travel across the sky,

in their original design.

It turns out there's a very clever and simple way

to represent the non-uniform speed zones.

You can, in one part of the zodiac,

just put the degree marks closer together,

and in another part of the zodiac, spread them out.

So when your sun pointer is going around at a constant speed

it will go through more degrees in a month

on one part of the zodiac than it does on the other.

James Evans and his colleague, Alan Thorndike,

were captivated by the Antikythera Mechanism

and decided to make their own model.

The maker of the Antikythera Mechanism

chose to represent the fact that the sun

speeds up and slows down on the zodiac

just by appropriately changing the spacing

between the marks on the zodiac scale.

The Greeks came up with elegant ways

of incorporating the variable speeds of the sun and moon

into their calendar computer.

But there are other objects in the sky

whose movements are even more complicated and mysterious,

the planets.

The Greek word for planet is plan-ee-tees, meaning wanderer.

It's an apt name because these objects

seem to move almost randomly across the sky.

The Greeks could see five planets with the naked eye,

all traveling along the zodiac,

the same narrow path that the sun travels past the stars.

Like the moon, planets speed up and slow down

but sometimes, planets appear to go backwards.

The planets are a whole different trip.

They're all over the map.

Some of the planets are just continuing to progress

in a sense forward through the sky

and then they seem to back up,

and then they go forward again, totally off the wall,

as far as the astronomers seemed to be concerned.

Somehow, they must have figured out

how to do all of those ratios,

and unfortunately, that whole part of the mechanism is lost.

And therefore, I think we ought to start

with the Evans model and see what we can do

to couple those on there, because don't forget,

this is only half of the machine.

Chris Weisbart and Maris Ensing

have reached the toughest part of their challenge,

making a hand-cranked computer that will calculate the

movement of all five planets known to the ancient Greeks.

Yeah, 64 goes backwards, goes the other way around.

And back on this shaft?

No, that goes onto a separate shaft,

so we need to get a shaft in there for that.

It's back to the drawing board.

The planets are different.

That's how they stood out to the ancient Greeks.

They don't follow the rest of the stars.

They kind of go back, sometimes back and forth.

They move at different speeds.

How would you drive this, all these different movements

from a single cranking motion like the Antikythera does?

To display the planets correctly,

the gearing will have to display retrograde motion.

Retrograde is simply a word that means backwards.

It just means that an object is moving

in the unaccustomed direction.

But the planets aren't actually moving backward

it just looks that way from Earth.

It's like driving next to a car on the highway.

There is continuous forward motion,

but varying speed gives one car

the appearance of moving backward.

He catches up and overtakes me

and here is where you get retrograde motion.

(upbeat music)

From the sun's perspective, all the planets

move forward continuously, but because the Earth

is also moving, from our perspective,

the other planets appear to slow down

or even travel backwards at times.

And because the Greeks thought the Earth was at the center,

they had to come up with other theories

to explain why the planets would move forward and backward

while still traveling in perfect circles.

Greek astronomers thought they knew the answer,

the planets must move in what they called epicycles.

And this is really just in a sense a circle on a circle,

or a sphere on a sphere.

If you imagine that a sphere is turning

and there's an object on it turning that way

but it's also attached to another smaller sphere

that's going in the opposite direction,

that means that now and then, it goes backwards.

(upbeat music)

It's like a teacup ride at an amusement park,

small circular orbits on top of a large spinning platter.

Sometimes, it appears as though

the teacups are moving backwards.

The Greeks thought the five visible planets

must move in similar patterns.

And it's likely that was represented

in the Antikythera Mechanism,

but there's no way of knowing for sure.

Any planetary gears are missing,

possibly still at the bottom of the Aegean Sea.

But Michael Wright believes he has solved the mystery.

He sees evidence that epicyclic gearing

was once part of the device.

There's a feature on the frame plate,

which nobody's ever talked about,

and nobody's understood it.

In his X-rays, he sees details

suggesting that blocks on the mechanism

supported a spindle that would have carried motion

out to the superior planet assemblies.

Each of the five planets known to the Greeks

would be represented by an epicycle

and a pointer at the front.

It's the combined motion of the epicycle itself

and the disc carrying the epicycle forward

that gives us the peculiar motion of the planet.

I can't guess exactly how the maker fashioned the pieces,

but the principle, I'm sure, is right.

But James Evans and his team have

a different hypothesis as to how the Antikythera Mechanism

might have represented the movement of the planets.

It could well be that the planetary display

is the way Michael Wright would have it,

with a full on epicyclic display.

In our conjecture, there's a separate dial for each planet,

and the dial just represents the key events

in each planet's cycle.

Pointers on these dials will indicate

when the planets go into retrograde motion

and the five dials fit within the zodiac dial

on the front of the mechanism.

It doesn't model retrograde motion

in a sort of cinematic way,

but it does announce when retrograde motion begins and ends.

But without additional evidence

to prove their theories, this mystery remains unsolved.

Chris and Maris decide to make their model

using Evans' concept, a series of separate dials,

partly because it's simpler.

The first thing we're going to do here

is to build the main part of the mechanism

onto this plate and once we've done that,

we'll build the planetary gear sets separately

and we'll make 'em work.
Okay.

(upbeat music)
(indistinct chatter)

Okay, so here we are.

We've got Evans' gear mechanism together for the planets.

I cut the plate based on all the different gearing cycles

that we had to have, so we have Mercury,

Venus, Mars, Jupiter, and Saturn,

and these are the main output shafts where the pointers

are gonna be on this side of the mechanism.

The more and more I look at this,

I just keep thinking about the original people who made it.

Who were they and how did they do it?

Incredible.

Really incredible.

Those are the kind of people that you'd love to meet.

Just the skill set and knowledge

that these people must have had, so early,

and it was so unexpected, it's...

Absolutely stunning.

(upbeat music)

Making a replica of the Antikythera Mechanism

can give insight into the mind of its maker.

The ancient mechanic was clever and able

and willing to make elaborate instruments.

I think we're looking at a very early form of geek,

for sure. (laughs)

People who really enjoyed what they were doing,

because otherwise, you can only do this for so long.

Both Michael Wright and Maris Ensing

believe the technology took years to perfect.

There's a level of detail and a level of craftsmanship

and knowledge, a body of knowledge, that you need to have

to even start working on these kind of things.

After we cut one of the first big gears

and the metal wasn't straight,

there are some oh dear moments in the middle of that

where all the sudden you start to look back

and you wonder how these guys would have dealt

with a similar problem.

Maris and Chris are inching toward their goal

of creating a working model of the Antikythera Mechanism

in two weeks' time, but they've hit a snag.

(metal clanging)

Bloody hell.

The planets aren't fully aligning.

Give me the tool, here.

With over 50 gears meshing,

alignment has to be perfect.

Oh, I see what's happening.

You know what?

This gear here is fouling.

We've got a little bit too close, chaps.

Even with a team of skilled workers

and the latest technology at their disposal,

they're finding it difficult.

And they're learning that the Greeks

had at least one advantage.

They work on a smaller scale.

The ratio between the thickness of the wheels

and the size of the wheel was better

so that even if the wheels aren't

as straight as you'd like 'em to be,

they would come together better,

even if your material wasn't 100% flat.

It's clear the culture that created

the Antikythera Mechanism had

a broad understanding of science.

The Antikythera Mechanism reminds us

that technology and the mathematics behind it

were already carried to a very high level

by the second century, BC.

But that knowledge seems to have been lost.

After the decline of Greece and Rome,

Europe went through a long period

with little technological progress, the Middle Ages.

It reminds us that forward progress

isn't something that's guaranteed.

It's possible to lose it.

Did the knowledge die out

or merely take a detour?

I don't think it all died out.

We know in many fields, learning was preserved

in the Middle East.

Through the study of scientific texts

and astronomical instruments from western Asia,

scholars are developing a different understanding

of technological history.

One very exciting topic right now

is the debt of European civilization

to the pre-modern Islamic World.

Long before there was a civilization

in western Europe, ancient Green and Roman scholarship

was adopted by cultures to the east.

The knowledge from Greece and Rome

which got translated into Arabic finally came back to us

in western Europe with the Islamic conquests

through northern Africa and up into Spain.

During the centuries that

Arab conquerors were occupying Spain,

Islamic scholars were advancing the science of astronomy

and building new geared devices

believed by some to be inspired by the Greeks.

In the 12th century, Muslim scholars

developed water clocks with gear technology.

In particular, a Muslim scholar named

Al-Jazari developed clocks, gates,

and useful gadgets for the home.

Muslim scholars adopted Greek scientific knowledge

and then helped inspire the European scientific renaissance

of the 15th century.

There was a large marketplace

of scientific ideas out there

when the European scientific renaissance was getting going.

Some of them came from Europe.

Some of them came from the Islamic world.

James Evans sees Greek knowledge

being preserved by Islamic astronomers.

The techniques of construction and representation

in the Antikythera Mechanism are things

that influenced the making of instruments for 1,000 years.

And those ancient techniques

are still inspiring engineers today.

At the Mad Systems workshop in Los Angeles,

Maris and Chris are close to finishing their model.

They're getting a better idea

of how the Antikythera device functions

and what it's capable of.

And they can't help but wonder,

what was it originally used for?

Did it help Greek sailors navigate by the stars?

Was it a calendar used by government officials?

Or was it merely a plaything?

What a spectacular machine.

I just love that this whole thing goes together.

Look at it.
That's incredible.

The transparency, now, where you can see

each of the gears and how they interface with each other.

Oh my god what a beast.

Unless you make one of these,

I don't think you'll ever get it.

No.

To understand how the Antikythera Mechanism

was built, it helps to build a model.

But to understand why it was built,

it's necessary to look at history.

For thousands of years, humans have

looked up at the night's sky

and tried to make sense of what they were seeing.

(ethereal music)

Stonehenge in England, the Egyptian pyramids,

Chichen Itza in Mexico, all were designed

to mark celestial observations,

the solstice, true north, or the equinoxes.

But 2,000 years ago, humans used a different way

to mark the movements of the heavens, with gears.

The Antikythera Mechanism wasn't monumental in scale

like the pyramids, but it was

a monumental achievement nonetheless.

The desire to turn celestial observations

into geared mechanisms continues today

in observatories and planetariums around the world.

This machine behind me is the

Zeiss Mark IV Planetarium Projector.

The Zeiss Mark IV is a sophisticated

planetarium projector that replicated

the movements of the stars and planets for audiences.

The Antikythera Mechanism didn't do projection

but in a sense, it was collecting and presenting

the same kind of information.

It was telling its audience what is happening in the sky

whether it's the past, the present, or even the future,

just as this instrument could do.

Just like a modern high tech planetarium,

the Antikythera Mechanism was built

to astonish and amaze its viewers.

This would have been something to enable them

to understand the cosmos and to display

and demonstrate that to other people.

It's quite possible that this was an educational too,

perhaps within a school of philosophy or astronomy,

for a teacher to show to students how things were working.

To hold the Antikythera Mechanism

in your hand was to hold the cosmos.

The gears are all hidden inside.

Somebody turns a little crank and the pointers go around.

So it must have been extremely amazing and impressive.

Of all the astronomical events

visible to the naked eye, perhaps none

is more awe-inspiring than an eclipse.

An eclipse happens when three objects are exactly in line.

The three objects are, as far as we're concerned,

the sun, the moon, and the Earth.

And what kind of an eclipse you get

depends on where the Earth is,

compared to these other two objects,

but of course we have solar eclipses and lunar eclipses

and both are spectacular events.

An eclipse can be breathtaking

but also terrifying if you didn't know it was coming.

But ancient astronomers discovered

that eclipses can be predicted.

If you have an eclipse today, for example,

there'll be another eclipse of the same circumstance

223 months later.

That's a cycle that's now called the Saros.

It was discovered by the ancient Babylonians.

This ancient pattern

is reflected in the Antikythera Mechanism.

Deep within it lies a gear wheel

with 223 teeth that serves two purposes.

It's part of the lunar mechanism,

but also, it's part of the eclipse prediction gear train.

This dial here shows eclipse predictions

so as we're rotating it and cranking the handle,

there are 223 months shown on this thing

and as I'm rotating it, you can see this needle point.

By combining information

from the eclipse dial and the front dial,

the mechanism can predict the possibility of an eclipse.

(ethereal music)

All we need to do now is to spend

the next while calibrating the machine

and fully understanding how we need to get this thing set up

but by the time we get this dial aligned

and the spiral working, we should be able to

figure it out and come up with

an appropriate eclipse prediction.

(mysterious music)
(electricity humming)

A check of the calendar reveals

that an eclipse is due soon.

Chris Weisbart heads north of Los Angeles to a place

where he will be able to observe the lunar eclipse

if it happens as predicted.

(mysterious music)
(electricity humming)

And there it is, a lunar eclipse, right on time.

What worked 2,000 years ago still works.

An eclipse is one of the most

dramatic events in the night's sky.

Mysterious and confusing, it's also orderly.

It happens at regular intervals,

and it's satisfying to create a working model

of the universe.

I think I know how the Greeks felt.

The audacity of sitting down

and thinking you're gonna build something that emulates

all of these movements as accurately as it does,

this is extraordinary.

The machine that dazzled people 2,000 years ago

is still awe-inspiring.

(mysterious music).