![]() Many of these methods are accurate (some external cycles are very uniform over huge stretches of time) but unreliable (the clock could stop working completely if it failed to track the external event properly). atomic decay (opaque, difficult to measure precisely)Įxternal events that the clock could track or be adjusted by.piezoelectric crystal oscillator (opaque, difficult to maintain).atomic oscillator (opaque, difficult to maintain).balance wheel (more inaccurate than pendulum).torsion pendulum (fewer ticks, but less accurate).gravity pendulum (inaccurate over the long term, and requires many ticks, which creates wear).Other methods are accurate but opaque (meaning that the clock is difficult to read or understand). 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). The options considered but rejected as sources of timing for the clock included: Self-contained clocks The timing mechanism for such a long lasting clock needs to be reliable and robust as well as accurate. 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 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. For example, nuclear power and solar power systems would violate the principles of transparency and longevity. Many options were considered for the power source of the clock, but most were rejected due to their inability to meet the requirements. 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. Hillis chose the 10,000-year goal to be just within the limits of plausibility. ![]() Whether the clock will actually receive continued care and maintenance for such a long time is debatable. Scalability: To ensure that the final large clock will work properly, smaller prototypes must be built and tested.Evolvability: It should be possible to improve the clock over time.Transparency: The clock should be understandable without stopping or disassembling it no functionality should be opaque.Maintainability: Future generations should be able to keep the clock working, if necessary, with nothing more advanced than Bronze Age tools and materials.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.The basic design principles and requirements for the clock are: Danny Hillis, "The Millennium Clock", Wired Scenarios, 1995 If I hurry I should finish the clock in time to see the cuckoo come out for the first time. ![]() I want the cuckoo to come out every millennium for the next 10,000 years. The century hand advances once every one hundred years, and the cuckoo comes out on the millennium. I want to build a clock that ticks once a year. Such icons reframe the way people think." Design Ideally, it would do for thinking about time what the photographs of Earth from space have done for thinking about the environment. It should be charismatic to visit, interesting to think about, and famous enough to become iconic in the public discourse. 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.
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