These guys are currently building a prototype of their clock inside a mountain in Texas near the border with New Mexico. And today, Danny Hillis at the foundation and a few pals, outline the way in which it will keep time.
Keeping time over such a period generates numerous challenges. First is ensuring the mechanical integrity of the machinery, which they achieve with long-lasting materials such as titanium, ceramics, quartz and sapphire.
Just as important is the environment: a series of tunnels carved into a mountainside in the high desert. Inside the mountain, the conditions are dry and the temperature constant.
Outside, however, the temperature varies between dessert extremes of hot and freezing. Hillis and co plan to exploit this temperature difference to power the clock using metal rods that change in length as the temperature varies. Human visitors will also be able to wind it.
As for time, the heart of the clock is a titanium pendulum with a 10 second cycles. Pendulum Time advances one unit once every 30 cycles, in other words every five minutes.
The rest of the clock is a digital computer using Pendulum Time as an input and generating analogue outputs in the form of various displays of time.
The mechanism first calculates Uncorrected Solar Time using a straightforward equation of time, which has been precomputed for the next ten thousand years to within the accuracy of the Earth’s variable rotation.
Next, the clock calculates Solar Time using a correction provided by a solar sychroniser: a vertical chamber that heats up when the sun is directly overhead and shines into it. This can add or take away a tick if the clock is out of sync. “The correction is positive if the Sun is detected before the just-before-noon tick, and negative if it is detected after the just after-noon tick,” say Hillis and co.