Any description of the clock must begin and end with that ridiculous projected working life, that insane, heroic, incomprehensible span of time during which it is expected to serenely tick.

Ten thousand years.

The span of time from the invention of agriculture to the present. Twice as long as the Great Pyramid of Giza has stood. Four hundred human generations.

Hillis's plan for the final clock has it built inside a series of rooms carved into white limestone cliffs, 10,000 feet up the Snake Range's west side. A full day's walk from anything resembling a road will be required to reach what looks like a natural opening in the rock. Continuing inside, the cavern will become more and more obviously human made. Closest to vast natural time cycles, the clock's slowest parts, such as the zodiacal precession wheel that turns once every 260 centuries, will come into view first. Such parts will appear stock-still, and it will require a heroic mental exertion to imagine their movement. Each succeeding room will reveal a faster moving and more intricate part of the mechanism and/or display, until, at the end, the visitor comprehends, or is nudged a bit closer to comprehending, the whole vast, complex, slow/fast, cosmic/human, inexorable, mysterious, terrible, joyous sweep of time and feels kinship with all who live, or will live, in its embrace.

Or so Hillis hopes.

Incidentally, I see that there is finally an iCal feed for the usually-awesome Long Now lecture series.