The Clock of the Long Now, also called the 10,000-year clock, is a mechanical clock under construction that is designed to keep time for 10,000 years. It is being built by the Long Now Foundation. A two-meter prototype is on display at the Science Museum in London. , two more prototypes are on display at The Long Now Museum & Store at Fort Mason Center in San Francisco.
The project was conceived by Danny Hillis in 1986. The first prototype of the clock began working on December 31, 1999, just in time to display the transition to the year 2000. At midnight on New Year's Eve, the date indicator changed from 01999 to 02000, and the chime struck twice.
The manufacture and site construction of the first full-scale prototype clock is being funded by Jeff Bezos's Bezos Expeditions, with $42 million, and is on land which Bezos owns in Texas.
Purpose
In the words of Stewart Brand, a founding board member of the foundation, "Such a clock, if sufficiently impressive and well-engineered, would embody deep time for people. It should be charismatic to visit, interesting to think about, and famous enough to become iconic in the public discourse. Ideally, it would do for thinking about time what the photographs of Earth from space have done for thinking about the environment. Such icons reframe the way people think."
Design
The basic design principles and requirements for the clock are:
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.
Whether the clock will actually receive continued care and maintenance for such a long time is debatable. Hillis chose the 10,000-year goal to be just within the limits of plausibility. There are technological artifacts, such as fragments of pots and baskets, from 10,000 years in the past, so there is some precedent for human artifacts surviving this long, although very few human artifacts have been continuously tended for more than a few centuries.
Power considerations
Many options were considered for the power source of the clock, but most were rejected due to their inability to meet the requirements. For example, nuclear power and solar power systems would violate the principles of transparency and longevity. In the end, Hillis decided to require regular human winding of a falling weight design for updating the clock face because the clock design already assumes regular human maintenance.
However, the clock is designed to keep time even when not being wound: "If there is no attention for long periods of time the Clock uses the energy captured by changes in the temperature between day and night on the mountain top above to power its time-keeping apparatus."
Timing considerations
The timing mechanism for such a long lasting clock needs to be reliable and robust as well as accurate. The options considered but rejected as sources of timing for the clock included:
Self-contained clocks
Most of these methods are inaccurate (the clock will slowly lose the correct time), but are reliable (that is, the clock will not suddenly stop working). Other methods are accurate but opaque (meaning that the clock is difficult to read or understand). gravity pendulum (inaccurate over the long term, and requires many ticks, which creates wear) torsion pendulum (fewer ticks, but less accurate) balance wheel (more inaccurate than pendulum) water flow (inaccurate) solid material flow (inaccurate) wear and corrosion (very inaccurate) rolling balls (very inaccurate) diffusion (inaccurate) tuning fork (inaccurate) pressure chamber cycle (inaccurate) inertial governor (inaccurate) atomic oscillator (opaque, difficult to maintain) piezoelectric crystal oscillator (opaque, difficult to maintain) atomic decay (opaque, difficult to measure precisely)