Antikythera mechanism working model.mov

NARRATOR: This is a reconstruction

of a 2,000-year-old computer.

The original battered pieces were found in a shipwreck more than a century ago,

and Michael Wright, a museum curator from London, spent decades studying them

in order to work out what the device was for.

He built this model in his home workshop,

with techniques similar to those that the Greeks might have used.

WRIGHT: This is my model of the Antikythera Mechanism.

The mechanism is a box full of gear wheels,

driving indications on dials, one at the front, and one at the back,

which we'll look at in a moment.

And it's all driven by --

working from the hand knob here.

On the front dial, we've got two scales.

The inner ring is the Zodiac, divided into degrees.

The outer ring is an annual calendar scale.

365 days.

NARRATOR: The device is a machine

for predicting the motions of the heavens.

When you turn the handle on the side, pointers move around the front dial,

showing the movements of the sun, moon, and the five planets that the Greeks knew.

The fastest pointer here is for the moon,

going around the sky once a month,

while the white and black ball

shows its changing phase.

Inside, a sophisticated setup of wheels riding around on other wheels

models the varying motions of the planets, according to the Greeks' astronomical theories.

As the side handle turns, the planet pointers sometimes move forwards

and sometimes backwards.

Meanwhile, the sun and moon pointers vary in speed, just as the actual sun and moon do

when seen from Earth.

WRIGHT: Now we look at the back.

We've got two sets of --

two displays together here.

The upper one is basically a calendar.

The spiral scale is divided into months, each of which is named,

and this is a cycle of months -- 235 months, which fit into 19 years.

These are months measured by the moon.

NARRATOR: An extendable pointer with a little needle on the end

tracks the spiral groove, just like the stylus on a record player.

When it gets to the end, you can lift the pointer up to reset it.

One of the little dials just inside the spiral

shows the dates of the Ancient Greek games, including the Olympics, on a four-year cycle,

while the other tracks a much longer

76-year cycle.

WRIGHT: The lower display is giving the times at which there may be eclipses.

Again, it's graduated into months,

and the markings are just in those months in which we expect there to be an eclipse,

either of the moon or of the sun, or of both.

The thing about eclipses is that they happen according to a pattern,

which repeats after 223 months.

So here we have a four-turn spiral scale,

with 223-month divisions.

NARRATOR: This dial is one of the most exciting parts of the mechanism.

It was used to predict

eclipses of the sun and moon,

according to a repeating 18-year cycle.

The Greeks probably got the data from Ancient Babylonian astronomer-priests,

who had been observing eclipses for centuries.

Inside the mechanism, you can see the gear trains that drive the pointers on the back dial.

This shot also reveals that this model was made of recycled metal plates,

just like the original would have been.

This is the first model of the Antikythera Mechanism to incorporate

all of its known features.

Thanks to Michael Wright, it's working again for the first time in 2000 years.