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The Millennium Clock
By Alexander Rose

The Idea
Sometimes an idea is big enough to bring lots of people together to make sure it happens. Thatās how it is with the Millennium Clock. Danny Hillis had this idea for a clock that would last 10,000 years. It would tick once a year and bong once every 100 years. The cuckoo would come out once every millennium.
Danny had helped design one of the fastest computers in the world. He worries that the world is changing so fast that most people donāt think past tomorrow. Many of us feel this way. We have trouble imagining the future, even a future just five years away, because it will be so different.
I have been working with Danny for the last three years to build this clock. We hope that it will help people slow down and think more deeply about the future, a future that goes far beyond our own lifetimes.

The Clock
These are the goals for the design of the Millennium Clock:
The clock has to last. It must display the correct time for the next 10,000 years.
It should be easy to maintain.
People should be able to figure out how the clock works just by looking closely at it.
People should be able to interact with the clock.
The same clock design should work at different clock sizes, small or large.

The three main parts necessary for any clock are power, timing, and a display. Danny and his friends brainstormed a list of all the different ways these three parts could work. Next, they compared these lists to the design goals above. If an idea for the power, timing, or display did not meet the guidelines, it was thrown out.
What was left were several ideas that we are now using to build a complete, working clock about 2.44 meters tall (about 8 feet). This clock will serve as a model for a giant clock that will be carved into a mountain of solid rock.

The Power
Visitors to the Millennium Clock will create the power. They will wind a huge weight so that it rises to the top of a tower. This weight will slowly descend on a screw that turns and powers the clock. We want people to interact with the clock, and we want the clock to need people for it to work.

The Timing
The timing source will come from two places. The first source, called a torsional pendulum, is a special kind of pendulum that twists instead of swings. The second timing source will be the sun. The clock will use the sun to reset itself. The noontime sunlight will heat up a piece of metal so it expands and flips a latch, resetting the clock.

The Display
We wanted to display natural events, like the sunset and moonrise, while also showing the date as it is seen on a calendar. We had to build a type of computer to keep track of both natural time and calendar time.
Most clocks use gears to track time. We realized that gears would not work because we needed so many large calculations.
So Danny designed a mechanical computer that works like electronic computers. But instead of using electricity passing through microscopic chips, it uses actual levers and wheels. These levers and wheels add numbers each time the clock ticks so the dials on the clock will turn correctly.

  If this idea does its job (for it is the idea, even more than the clock), you may now be wondering: How will the world be 1,000 years from now, or 1,000 years after that, or 1,000 years after that?

A Timely Idea
During our design process, we came up with many different ideas for the 10,000-year clock. Some are as simple as predicting how fast a mountain will erode and marking it so that each year can be seen as it washes away. One idea was to have a family pass down the knowledge of the clock from generation to generation.
What are your ideas for a 10,000-year clock? Send ideas and drawings to The Long Now Foundation, P.O. Box 29462, San Francisco, California 94129. We may publish them on our Web site!

Alexander Rose is the Executive Director of The Long Now Foundation and project manager for The Millennium Clock. Visit the Web site,, to watch us build the first small version of the Clock!
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