Building a 10,000-Year Clock

Inside this mountain in West Texas, a clock is being built to

tick for ten thousand years. That's about twice as long as all of

recorded history. The Long Now Foundation is building it.

Jeff Bezos put forty-two million dollars into the project and

provided the mountain. From outside, you would never know it's here.

The only visible sign is a small sapphire dome on the summit.

Let's cut the mountain open.

A tunnel leads to the foot of a vertical shaft, five hundred feet

tall and twelve feet wide. A spiral staircase is

carved into the rock around it. The machinery fills the lower part of the

shaft. Above it, the stairs keep climbing all the way to

the

summit.

Getting here takes a rugged hike almost two thousand feet above the

valley floor. Set into the cliff is a door of jade, rimmed in

stainless steel.

Behind it waits a second steel door and then a tunnel a few hundred feet

long into the dark. At its end, look straight up, and a

tiny dot of daylight shines five hundred feet above you.

The first part of the clock you meet is the drive weight.

It's a stack of stone discs about the size of a small car, weighing ten

thousand pounds. As it sinks, it releases the energy that

moves the display and rings the bells.

Depending on when the clock was last wound, you may climb up to

seventy-five feet before you reach it.

Above it is the winding station, a capstan like the ones on

old sailing ships. It takes two or three people to push it around and lift

those stones. Here's the strange part.

The clock always knows the correct time, but to save energy, it

won't move its dials until a visitor powers them.

So every visitor first sees the date of the last visit.

Then the calendar wheels whirl forward until they stop at the present with a

chime.

Higher up, twenty Geneva wheels rise through the

shaft, each eight

feet across and weighing a thousand pounds.

Together, they form the chime generator, a mechanical

computer that rings ten bells in a different order every day the clock is

visited.

That's more than three and a half million melodies,

enough for ten thousand

years. The musician Brian Eno composed the melody

generator.

At the top of the machinery stands the heart of the clock.

Here it takes its look from Long Now's first prototype, now in London's

Science Museum. Brushed steel, brass, and a black dome of

stars. One weight tower stores the energy the sun

provides each

day. The other, crowned by a spinning governor, keeps the

display and the bells moving at a steady pace.

Its heartbeat is the pendulum. In the mountain clock, it's a

six-foot titanium assembly with weights the size of footballs,

sealed in quartz glass. It doesn't swing.

It twists slowly back and forth once every ten seconds.

Each twist lets the escapement release the gears by a single step.

Instead of long chains of gears, the clock calculates in binary.

Its designer, the computer scientist Danny Hillis,

gave it a mechanical

computer made of levers. Each lever is a bit, a one

or a zero. By adding the same binary number again

and again,

it can follow the moon's phases or any other cycle more

precisely than a train of gears.

And this is what visitors climb all the way up to see.

The dial is eight feet across. Its black dome carries the

stars, turning with the sky once a day and slowly drifting

with the precession of the zodiac.

On the brass ring, the sun and the moon move through the day,

and the moon

turns to show its phase. Even the year has five digits,

so the clock is ready for the year ten thousand.

Off the main cavern are five anniversary chambers.

For one year, ten years, a hundred, a thousand, and ten thousand

years. The first holds an orrery, a mechanical model of

the planets, along with the space probes launched in

the twentieth

century. Once a year, at solar noon, the clock sets it

in motion. The last three rooms are left for future generations

to fill.

So what powers the timekeeping? The sun.

In the sapphire cupola on the summit, sunlight heats a chamber of air.

Each day, the air expands in the heat and contracts in the cold of night,

pushing a graphite cylinder, and a ratchet turns that breathing into

winding force. Long Now says it's enough to keep the

pendulum

running for five hundred years without a single human hand.

But a pendulum slowly drifts, so the clock checks itself against the

sky. At solar noon, a prism in the cupola sends a

beam of sunlight down the shaft onto the solar synchronizer, which

resets the clock to true noon. If clouds hide the sun, the

pendulum simply carries on until the next clear day, and a cam

shaped by the equation of time keeps sun time and clock time

in step through the seasons.

Now look up.

Earth's axis wobbles like a spinning top, tracing a slow

circle among the stars about every twenty-six thousand years.

That's why the pole star changes. When the pyramids were built, it was

Thuben. Today, it's Polaris. Watch ten thousand

years go by.

Around the year 2600, the March equinox slides out of

Pisces into Aquarius. The pole moves on through Cepheus.

Around the year 10000, it comes close to Deneb, and Vega takes

over a few thousand years later. Over its lifetime, this

clock will record nearly forty percent of one full wobble.

The clock is still being built. The shaft was finished in 2011,

and the bells first rang in 2022. No opening date has

been announced. When it opens, reaching it will take a full day's

hike. It's a symbol of long-term thinking, built for

people who won't be born for thousands of years.

This is the clock of the Long Now.