Most clocks are built to keep time on fairly short timescales: windup watches may run a few days between windings, torsion pendulum clocks go about a year between windings, battery-powered watches often go several years on a given battery, and of course electrical clocks plugged into mains power run as long as that power is provided. All of these inventions require continuous human intervention to operate, and even more attention to keep the clocks accurately set to the current time. But what if you're thinking long-term...really long term? In 1986, Danny Hillis (previously mentioned here) envisioned a clock that would autonomously keep time for 10,000 years. Hillis said, "I want to build a clock that ticks once a year. The century hand advances once every one hundred years, and the cuckoo comes out on the millennium. I want the cuckoo to come out every millennium for the next 10,000 years. If I hurry I should finish the clock in time to see the cuckoo come out for the first time." Although the first prototype of the clock doesn't have a cuckoo per se (it made a "bong" sound), it was up and running for the millennium transition in 2000. (It's pictured at left.)

Now known alternately as The 10,000 Year Clock or The Clock of the Long Now, this "world's slowest computer" is intended to foster long-term thinking. It's an interesting notion, and its proponents at The Long Now Foundation have even taken to referring to years with a leading zero, like 02008...emphasizing the notion that history's sweep encompasses many thousands of years, and thus long-term thinking is critical to humanity's long-term survival. Here's a quote from Hillis's original article on the clock:

I think of the oak beams in the ceiling of College Hall at New College, Oxford. Last century, when the beams needed replacing, carpenters used oak trees that had been planted in 1386 when the dining hall was first built. The 14th-century builder had planted the trees in anticipation of the time, hundreds of years in the future, when the beams would need replacing. Did the carpenters plant new trees to replace the beams again a few hundred years from now? ...

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. The Dead Sea Scrolls managed to survive by remaining lost for a couple millennia. Now that they've been located and preserved in a museum, they're probably doomed. I give them two centuries -- tops.

If ultra-long-term thinking interests you, check out The Long Now Foundation's page on the clock. There's also a good Wikipedia page which summarizes many design considerations. Tomorrow I'll have some trivia on designing art that will be placed in the chamber with the clock.