A mechanical device invented by George Graham around 1710 which illustrates the motions of the planets around the sun. The first working example was built by John Rowley, a London instrument maker. Like all subsequent models, it consisted of metal arms which were powered by gears radiating out from a central clockwork-driven mechanism. At the end of each arm was a ball representing one of the planets. Once the mechanism was set in motion, each of the arms turned around the center, which represented the sun, thus describing the orbits of the planets they represented. It was generally a slow mechanism, with the Earth taking about 10 minutes to complete its orbit. Despite this painfully slow pace, the orrery became a favorite amusement and teaching device of the time.
The orrery takes its name from the fact that Rowley made one for Charles Boyle, the fourth Earl of Orrery, and named it for him. | 
