Variation of the Equation of Time with the Precession of the Equinoxes

The Clock of the Long Now is a mechanical computer designed to keep accurate time for 10,000 years. The Clock relies on the constancy of the length of a day to keep it in sync via an optical trigger that fires at local solar noon. The equation of time converts between local solar time and the Earth's rotational period. The version of the equation of time implemented here accounts for the variation of sidereal time with the precession of the equinoxes over a period of 26,000 years. The cylindrical plot of the equation of time shown here in 3D is implemented as a mechanical cam that adjusts the timing of the optical sync trigger.