From Discover:
SOMETIMES, WHEN THINGS GET SUFFICIENTLY WEIRD, SUBTLETY NO longer works, so i’ll be blunt: The gleaming device I am staring at in the corner of a machine shop in San Rafael, California, is the most audacious machine ever built. It is a clock, but it is designed to do something no clock has ever been conceived to do—run with perfect accuracy for 10,000 years.
Everything about this clock is deeply unusual. For example, while nearly every mechanical clock made in the last millennium consists of a series of propelled gears, this one uses a stack of mechanical binary computers capable of singling out one moment in 3.65 million days. Like other clocks, this one can track seconds, hours, days, and years. Unlike any other clock, this one is being constructed to keep track of leap centuries, the orbits of the six innermost planets in our solar system, even the ultraslow wobbles of Earth’s axis.
Made of stone and steel, it is more sculpture than machine. And, like all fine timepieces, it is outrageously expensive. No one will reveal even an approximate price tag, but a multibillionaire financed its construction, and it seems likely that shallower pockets would not have sufficed.