An orrery is a mechanical device that illustrates the relative positions and motions of the planets and moons in the solar system in a heliocentric model. They are typically driven by a clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of the arms.
The first orrery was conceived by English clockmaker and inventor George Graham (c.1674-1751) around 300 years ago. This initial model only showed the earth-moon system which orbits our Sun. Graham gave the design of this original model to the celebrated London instrument maker John Rowley, who was commissioned to make one for his patron Charles Boyle (1674-1731). Boyle's patronage of Rowley soon led to the elaboration of Graham's invention so that it included all the known planets and some moons of the solar system. The origin of the term "orrery" is explained when we consider the title Boyle held - the fourth Earl of Orrery (Orrery being the old name for a part of Co. Cork).