These are the principles that Danny Hillis used in the initial stages of designing a 10,000 Year Clock. We have found these are generally good principles for designing anything to last a long time.
Longevity
With occasional maintenance, the clock should reasonably be expected to display the correct time for the next 10,000 years.
Maintainability
The clock should be maintainable with bronze-age technology.
Transparency
It should be possible to determine operational principles of the clock by close inspection.
Evolvability
It should be possible to improve the clock with time.
Scalability
It should be possible to build working models of the clock from table-top to monumental size using the same design.
- Longevity:
- Go slow
- Avoid sliding friction (gears)
- Avoid ticking
- Stay clean
- Stay dry
- Expect bad weather
- Expect earthquakes
- Expect non-malicious human interaction
- Dont tempt thieves
- Maintainability and transparency:
- Use familiar materials
- Allow inspection
- Rehearse motions
- Make it easy to build spare parts
- Expect restarts
- Include the manual
- Scalability and Evolvabilty:
- Make all parts similar size
- Separate functions
- Provide simple interfaces
Examples:
| Clepsydra (water clock) | Atomic Clock | |
|---|---|---|
| Power | potential energy supplied by human | electricity |
| Time | flow rate of water | oscillation of cesium atom |
| Convert | lever with e.o.t. adjustment | electronic frequency divider |
| Display | pointer, gong | numeric display, radio |
Options considered for powering the Clock:
| Atomic | Poor maintainability&transparency |
|---|---|
| Chemical | Poor scalability |
| Solar Electric | Poor maintainability |
| Pre-stored potential energy | Poor scalability |
| Water flow | Exposure to water |
| Wind | Exposure to weather |
| Geothermal | Poor scalability |
| Tidal gravitational changes | Poor scalability |
| Temperature change | … |
| Pressure change | Need for bellows or seal |
| Seismic and plate tectonic | Poor scalability |
| Human winding | Fosters responsibility |
Conclusion: My current favorite is human winding because it fits with goals of clock. Temperature change is also a viable alternative.
Options considered as sources of timing for clock:
| pendulum | inaccurate |
|---|---|
| spring and mass | inaccurate |
| water flow | inaccurate and wet |
| solid material flow | inaccurate |
| daily temperature cycle | unreliable |
| seasonal temperature cycle | imprecise |
| tidal forces | difficult to measure |
| earths rotating inertial frame | difficult to measure accurately |
| stellar alignment | unreliable (clouds) |
| solar alignment | unreliable (clouds) |
| atomic oscillator | too high tech, difficult to maintain |
| piezoelectric oscillator | too high tech, difficult to maintain |
| atomic decay | difficult to measure precisely |
| wear and corrosion | very inaccurate |
| marble roll | very inaccurate |
| diffusion | inaccurate |
| tectonic motion | difficult to predict and measure |
| orbital dynamics | difficult to scale |
| audio oscillator | inaccurate and difficult to measure |
| pressure chamber cycle | inaccurate |
| inertial governor | inaccurate |
| human ritual | too much dependence on humans |
Conclusion: Since no single source does the job, use an unreliable timer to adjust an inaccurate timer, creating a phase locked loop. My current favorite combination is to use solar alignment to adjust a slow mechanical oscillator.
Options considered for the part of the Clock that
converts time source to display units:
| Electronics | Poor maintainability&transparency |
|---|---|
| Gears | Need for rational approximation |
| Pre computed display | Lots of calendar pages |
| Levers | Require very slow timing source |
| Hydraulics | High power |
| Mechanical Digital Logic | … |
Conclusion: Mechanical digital logic.
Options for how to display time:
| chimes | Poor maintainability&transparency |
|---|---|
| flutes or whistles | cannot sound too often |
| sweeping hand | fragile, confusing for many hands |
| concentric rotating rings | … |
| balls in holes | creates collectibles |
| shadows, beams of light | … |
| animation | high power |
Conclusion: This is the one I have thought about the least. Note that there can be multiple displays, and that some display can have independent power sources.
Some options for what to display:
| Display | Days per cycle |
|---|---|
| Time of Day | 1 |
| Phase of moon | 29.5305882 |
| Lunar eclipses | -6793.504897308 |
| Season | 365.242 |
| Positions of visible planets | mercury 87.969 venus 224.701 earth 365.256 mars 686.980 jupiter 4331.772 saturn 10759.22 |
| Procession of zodiac | 9417404.8533435 |
| Christian Calendar | approximates solar years |
| Moslem Calendar | approximates lunar years |
| Jewish calendar | … |
| Chinese calendar | … |
| Mayan calendar | 360 |
| day count | 1 |
| moon count | 29.5305882 |
| year count (centuries, millennia) | 365.242 |
| historical events (past and future) | … |
Other information to display: (library functions)
| future time scales | … |
| astronomical ephemeris | … |
| maintenance manual | … |
| visits to the clock | … |
| weather records | … |
| earthquake records | … |
| calendar systems | … |
| general useful knowledge | … |
The design principles for the clock were primarily the work of Daniel Hillis with additional thoughts brought about by discussion with the other founding board members.