The 10,000-year clock will mark time with astronomic and calendric displays and a chime generator designed with the help of Brian Eno that can produce over 3.5 million unique bell chime sequences — one for every day the clock is visited for the next 10,000 years.

Ten thousand years is about the age of modern civilization, so the clock will measure out a future of civilization equal to its past. This assumes our civilization is in the middle of whatever journey we are on — an implicit statement of optimism.

To see the clock you need to start at dawn, like any pilgrimage. It will require a day’s hike to reach its interior gears.

The first monument-scale 10,000-year clock still being assembled, deep inside a mountain, in West Texas.

The Clock provides a rare invitation to think and engineer at the timescale of civilization. It offers an enduring symbol of our personal connection to the distant future.

Why would anyone build a Clock inside a mountain with the hope that it will ring for 10,000 years?

Part of the answer: just so people will ask this question, and having asked it, prompt themselves to conjure with notions of generations and millennia. If you have a Clock ticking for 10,000 years what kinds of generational-scale questions and projects will it suggest? If a Clock can keep going for ten millennia, shouldn’t we make sure our civilization does as well? If The Clock keeps going after we are personally long dead, why not attempt other projects that require future generations to finish?

The larger question is, as virologist Jonas Salk once asked, “Are we being good ancestors?”

— Kevin Kelly, from Clock in the Mountain

Ten thousand years — the life span I hope for The Clock — is about as long as the history of human technology. We have fragments of pots that old. Geologically, it's a blink of an eye. When you start thinking about building something that lasts that long, the real problem is not decay and corrosion, or even the power source. The real problem is people. If something becomes unimportant to people, it gets scrapped for parts; if it becomes important, it turns into a symbol and must eventually be destroyed. The only way to survive over the long run is to be made of materials large and worthless, like Stonehenge and the Pyramids, or to become lost.

Just as Stonehenge and the Pyramids help us imagine our long past, The Clock invites us to image our long future.

— Danny Hillis, from The Millennium Clock

Ten thousand years from now: can you imagine that day? Okay, but do you? Do you believe “the Future” is going to happen? If The Clock works the way that it’s supposed to do — if it lasts — do you believe there will be a human being around to witness, let alone mourn its passing, to appreciate its accomplishment, its faithfulness, its immense antiquity? What about five thousand years from now, or even five hundred?

Can you extend the horizon of your expectations for our world, for our complex of civilizations and cultures, beyond the lifetime of your own children, of the next two or three generations?

— Michael Chabon, from The Future WIll Have to Wait

Civilization is revving itself into a pathologically short attention span. The trend might be coming from the acceleration of technology, the short-horizon perspective of market-driven economics, the next-election perspective of democracies, or the distractions of personal multi-tasking. All are on the increase. Some sort of balancing corrective to the short-sightedness is needed — some mechanism or myth which encourages the long view and the taking of long-term responsibility, where ‘long-term’ is measured at least in centuries.

The Clock presents both mechanism and myth.

It would be charismatic to visit, interesting to think about, and famous enough to become iconic in the public discourse. Ideally, it would do for thinking about time what the photographs of Earth from space have done for thinking about the environment. Such icons reframe the way people think.

— Stewart Brand, from The Clock of the Long Now

I cannot imagine the future, but I care about it. I know I am a part of a story that starts long before I can remember and continues long beyond when anyone will remember me. I sense that I am alive at a time of important change, and I feel a responsibility to make sure that the change comes out well. I plant my acorns knowing that I will never live to harvest the oaks.

— Danny Hillis, from The Millennium Clock

It’s one thing for a monument to endure for ten millennia, but 10,000-year clocks also have to keep accurate time.

Over ten thousand years, performing even the most basic functions of a clock: gathering energy, keeping time, and converting it into a meaningful display, becomes interestingly complex. As 10,000-year clock inventor Danny Hillis considered each of these functions, a set of design principles emerged which are generally useful to consider when designing anything to last a long time:

Longevity

10,000-year clocks should display the correct time for the next 10,000 years

• Go slow
• Minimize sliding friction
• Stay clean and dry
• Expect bad weather and earthquakes
• Expect non-malicious human interaction
• Don’t tempt thieves

Maintainability

It should be possible to maintain a 10,000-year clock with little maintenance, using bronze-age technology

• Use familiar materials
• Make it easy to build parts
• Include the manual

Transparency

It should be possible to determine the operational principles of a 10,000-year clock with close inspection

• Allow inspection
• Allow rehearsed motions
• Expect restarts

Evolvability

It should be possible to improve a 10,000-year clock over time

• Separate functions
• Provide simple interfaces

Scalability

It should be possible to build working models of a 10,000-year clock from table top to monumental size using the same design

• Make all parts similar size

You will see all these principles reflected throughout the design of the 10,000-year clock.

The 10,000-year clock is entirely mechanical, made of long-lasting materials, including titanium, ceramics, quartz, sapphire, and 316 stainless steel. Even the most accurate mechanical clocks eventually drift off of the correct time, so the clock synchronizes with the noontime sun. The clock counts oscillations of the pendulum for day to day time, sunlight falling on the solar synchronizer to account for long-term drift, and a precomputed correction to solar time to accommodate for the orbital and rotational changes of Earth (rendered by the iconic Equation of Time Cam). Outputs include a depiction of the sky in the form of an orrery, a display of the Gregorian calendar date, and the chimes.

A visit to the 10,000-year clock begins several hours before you reach the main winder. Just reaching the entrance tunnel, situated 1,500 feet above the high scrub desert, will leave some visitors out of breath, nicked by thorns, and wondering what they got themselves into. Once you enter the underground space , you will eventually encounter a set of metal doors. These act as a kind of crude airlock, keeping out dust and wild animals. Once through the doors you head into the darkness of a long tunnel. At the end, there’s the mildest hint of light ahead that you slowly find your way to. You look up. There is a faint light filtering down to you through giant gears illuminating the beginning of a spiral staircase.

You start climbing the staircase, winding up the outer rim of the tunnel, rising toward the gears and faint light overhead. The stairs are carved out of the rock. To cut the spiral staircase, a special stone cutting robot was invented, which crept downward from the top of the shaft, grinding out a few stairs per day for nearly two years. After climbing about 100 feet, the first clock part you encounter is the driveweight of the clock’s power system. This is a large bronze egg filled with concrete, about the size of a small car, and weighing 10,000 pounds.

After you pass the weights, you arrive at a winding station. It is a horizontal windlass or capstan, like one that might raise the anchor of an old sailing ship. It takes two or three visitors to turn the capstan easily and slowly lift its 10,000-pound weight. Together you spin the winder until the weight reaches the top of its travel beneath your feet.

You keep climbing, past a multitude of giant gears, some over 8 feet in diameter and weighing 1,000 pounds. And past those you start to see large Geneva wheels that form the chime generator. This mechanical computer uses a progressive algorithm to determine which of the millions of possible sequences the chimes will play on a given day. The chimes will not repeat for over 10,000 years. This is the world’s slowest computer.

On days when visitors are there to wind it, the calculated sequence rings each of the ten bells.

Fellow traveler and musician Brian Eno named our organization “The Long Now Foundation” to indicate the expanded sense of time the clock provokes — not the short now of next quarter, next week, or the next five minutes, but the “long now” of centuries. Eno also worked with Danny Hillis on the chime generator’s progressive algorithm. His album, January 07003: Bell Studies for The Clock of the Long Now, provides a preview of the chimes that will ring inside the mountain over the millennia.

The clock always knows the correct time, but to save energy, it won’t update its display dials unless a visitor is present to provide the necessary power. Another hand-turned wheel awaits your effort. This one winds more easily — moving display dials requires less power than ringing bells. As you wind, the calendar wheels whirr until it stops and it shows the current date and orientation to the heavens.

So how does the clock keep going if no one visits it for months, or years, or perhaps decades to wind it? A pathway continues up to the outside summit of the mountain and you can see the answer. That faint light seen from the bottom has resolved into a 12 foot cupola with a sapphire glass window covering the top of the shaft. This and a partially buried cylinder are the only parts of the clock visible from the outside. Sunlight enters the cupola and is focused down into the solar synchronizer, heating up a chamber of air which can be harvested as a mechanical signal for solar noon. This signal is adjusted by the Equation of Time Cam, which accounts for the +/- 15 minute difference of solar-to-absolute-time due to the eccentricity of the Earth's orbit (and a few other slow effects like the precessional cycle and rotational speed).

Thermal power has been used for small mantel clocks before, but it has not been done before at this scale. As long as the sun shines and night comes, the clock can keep time by itself, but it can’t ring its chimes for long or show the time it knows without visitors.

There is more than just technology in the mountain. The ticks of time are a very human invention. Astronomical calendars are among the first relics of culture, and often the mark of civilizations. the clock in the mountain not only plays the music of an ever-changing slow melody, but it will collect cultural expressions of time, ticks to mark the passage of decades and centuries. Off to the side of the main cavern of the clock are a series of small niches to explore and collect these notices of time. Their contents will be a surprise.

The journey to the clock in the mountain ends on the summit in light. It is the sun that powers its ringing below. Like a heart beating while we sleep, the clock in the mountain keeps time even when we pretend the past did not happen and the future will not come.

Almost any kind of artifact can last 10 millennia if stored and cared for properly. We have examples of 5,000-year-old wood staves, papyrus, and leather sandals. On the other hand, modern metal can corrode in a few years of salt and rain. For longevity, the environment is often more important than material. The mountain top in Texas is a high dry desert, and in the clock shaft below, the temperature is a stable 55 degrees fahrenheit regardless of time or season. This avoids freeze and thaw cycles, which can be as corrosive as water. It’s an ideal world for a ceaseless Clock.

Still, the clock is a machine with moving parts, and parts wear down and lubricants evaporate or corrode. Most of the clock will be made in a marine grade 316 stainless steel. One of the main worries of the clockmakers is that elements of a 10,000-year clock — by definition — will move slowly. The millennial dial creeps so slowly it can be said to not move at all during your lifetime. Metals in contact with each other over those time scales can fuse — defeating the whole purpose of an ongoing timepiece. Dissimilar metals in contact can eat each other in galvanic corrosion. To counteract these tendencies, all of the clock’s bearings are ceramic.

Ceramics will outlast most metals as they can be diamond hard and do not corrode or rust. We have found shards of clay pots over 17,000 years old. Because these engineered ceramic bearings are so hard, and rotate at very low speed, they require no grit-attracting lubrication.

The biggest problem for the beating clock will be the effects of its human visitors. Over the span of centuries, valuable stuff of any type tends to be stolen, kids climb everywhere, and hackers naturally try to see how things work or break. But it is humans that keep the clock's bells wound up, and humans who ask it the time. The clock needs us. It will be a long, out of the way journey to get inside the clock ringing inside a mountain. But as long as the 10,000-year clock ticks, it keeps asking us, in whispers of buried bells, “Are we being good ancestors?”

In 02024, Danny Hillis answered frequently asked questions about the 10,000-year clock.

In 02022, the bells of the monument-scale 10,000-year clock pealed for the first time. This footage is from the new documentary We Are As Gods, which explores the many legacies of Long Now cofounder Stewart Brand.

In 02018, with underground excavation complete, the first enormous timekeeping components were assembled underground, including the drive weight, winder and main gearing.

In 02012, the monument-scale power storage system was shop tested for the first time. This assembly of gears winds up the three sided rack gear in the center that resembles a vertebrae. While only about 20 feet of it are employed here in the shop, it will eventually be over 75 feet tall.

In 02011, we completed the raise bore excavation of the 500 foot deep vertical clock shaft. Instead of drilling down from the top, a large diameter reamer was pulled up from the bottom to the surface. It's more efficient than a top-down drill because the rubble isn't fighting gravity. Following this work, we began to cut the spiral stairway into the walls of the shaft using a robotic stone-cutting saw and continued manufacture and testing of several monument-size clock components.