San Rafael, Calif., 2002—A NIST Web site boasts that an atomic chronometer it has constructed “would neither gain nor lose one second in about 3.7 billion years.” Atomic horologists often speak as if their timepieces could run continuously for thousands of centuries. Balderdash—a typical cesium clock lasts no more than 20 years. A decent wristwatch runs longer.

But at facilities in California and Seattle, a small group of futurists and engineers have begun building a mechanical clock meant to tick through 1,000 decades. The Clock of the Long Now, as its chief designer, Danny Hillis, calls it, is as much a sociological experiment as a functional chronometer.

“A clock is a symbol of continuity; one that lasts a really long time might give people a sense of perspective, help them think about the year 3000 as more than just an abstraction,” Hillis says. “Our record of civilization extends back roughly 10,000 years, so that struck me as a good interval to look forward.”

Hillis may seem like an unlikely leader of a movement to reverse society's preoccupation with the fast and soon. In the 1980s he designed supercomputers; in the 1990s it was theme park rides. He can spare an hour for an interview only if half of it is done on the trip to Silicon Valley for his next meeting.

Nevertheless, Hillis, with help from writer Stewart Brand, musician Brian Eno and others, is trying to craft an artifact that will not just endure but will also inspire. The clock will have to be wound once a year. “And when you first come up to it, it will only display what time it was when the last person was there,” Hillis explains. “It will track the current time, but you will have to wind it—put some energy into it—to get it to advance to show what time it is now.”

Brand and Hillis co-chair a foundation (www.longnow.org) that has been given use of a mountain in Texas (and purchased its own peak in Nevada), inside which they hope the final, monument-size clocks will sit. Through a slit in the cavern ceiling, rays of the noon sun will focus onto a bimetallic strip, triggering a weight to resynchronize the clock in case its time has drifted.

Although this all may sound quite spiritual, “we don't want to create a religion,” Brand avers as he stands next to a mock-up of the second prototype. This version is twice the size of the first, on exhibit at the Science Museum in London. In place of a circular dial, however, the clock is now crowned with a large orrery indicating planetary positions.

Below the “face” sits a stack of seven metal rings, each about 75 centimeters in diameter and fringed with levers. Vertical pins stuck into the rings engage the levers as the rings rotate, working as a mechanical binary computer to count the hours and compute the date. Because the clockwork is strictly mechanical and is open to inspection, “you can figure out how to restart it if it hasn't been on in 100-odd years,” Hillis says. But whether his idea gathers enough currency to get a 10,000-year clock started in the first place, only time will tell.