The Clock of the Long Now is an ambitious, monumental project from the Long Now Foundation, headed up by Stewart Brand, Danny Hillis, and musician Brian Eno. The clock is meant to last 10,000 years, and the purpose of the clock is to promote long-term thinking.
Housed inside a mountain, the clock was built according to 5 core principles:
Longevity: The clock should be accurate even after 10,000 years, and must not contain valuable parts (such as jewels, expensive metals, or special alloys) that might be looted.
Maintainability: Future generations should be able to keep the clock working, if necessary, with nothing more advanced than Bronze Age tools and materials.
Transparency: The clock should be understandable without stopping or disassembling it; no functionality should be opaque.
Evolvability: It should be possible to improve the clock over time.
Scalability: To ensure that the final large clock will work properly, smaller prototypes must be built and tested.
The clock is powered by the temperature fluctuations inside the mountain and is kept accurate by both pendulum movements and a solar phase lock system. It ticks only once per day and turns over once a millennium.