7 of 7

Clock of the Long Now, Texas

Inventor and scientist Danny Hillis conceived of the Clock of the Long Now—also called the 10,000-Year Clock—as a way to promote long-term thinking. The full-scale clock, which will stand nearly 200 feet tall and is designed to keep time for 10,000 years, is currently being constructed inside a mountain in western Texas as a project of the Long Now Foundation, a nonprofit established in 1996. Though there's no word as to when the clock will be completed, the original 8-foot-tall protype is currently on loan to and display at the Science Museum of London.



Hillis has had to get creative to build a timepiece that keeps ticking for 10,000 years. The clock will undoubtedly require maintenance, so he decided that it should require human winding—it's unlikely that any other power source would be around for 10,000 years. As he couldn't find a timing mechanism that would be both reliable and accurate, Hillis used two—one that's reliable but not accurate, and the other vice versa—linked together in what's called a phase-locked loop: a type of electronic circuit that matches the phase of an input signal with the one derived from its output oscillator to keep the two in balance. To calculate time, the 10,000-year clock will use binary digital logic that's mechanically (rather than electronically) implemented through a sequence of stacked binary adders, and time will be displayed using five digits (i.e., 02013) instead of the standard four.



The forward-thinking timepiece—which will be displayed on land open to the public—will include astronomical elements as well.