These are the principles that Danny Hillis generated to guide the design of the Clock.
• 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.
Some rules that follow from the design principles:
- 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
Basic Clock Modules:
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 | innacurate |
|---|---|
| spring and mass | innacurate |
| water flow | innacurate and wet |
| solid material flow | innacurate |
| 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.
