It has a differential gear arrangement with over 30 gears, with teeth formed through equilateral triangles. When past or future dates were entered via a crank (now lost), the mechanism calculated the position of the Sun, Moon or other astronomical information such as the location of other planets. The use of differential gears enabled the mechanism to add or subtract angular velocities. The differential was used to compute the synodic lunar cycle by subtracting the effects of the sun's movement from those of the sidereal lunar movement.
Interesting.
34 posted on 11/29/2006 11:44:06 AM PST by The G Man
(The NY Times did "great harm to the United States" - President George W. Bush 6/26/06)