An orrery [awr-uh-ree] 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 modern orrery was built circa 1704 by George Graham and Thomas Tompion. Eisinga’s ‘Planetarium’ (actually, an orrery) was built from 1774 to 1781 by Eise Eisinga in his home in Franeker, in the Netherlands. It displays the planets across the width of a room’s ceiling, and has been in operation almost continually since it was created.

According to Cicero, the Greek philosopher Posidonius constructed an orrery that exhibited the diurnal motions of the sun, moon, and the five known planets. Cicero’s account was written in the first century BCE. The Antikythera mechanism is one of the first orreries. It is an ancient mechanical calculator designed to calculate astronomical positions. It was discovered in an ancient shipwreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to about 150-100 BC. Technological artifacts of similar complexity would not be common for a thousand years.


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