What is Orrery?
[[File:orrery small.jpg|thumb|upright=1.6|A small orrery showing earth and the inner planets]] An '''orrery''' is a mechanical [[model]] of the [[Solar System]]. It shows the relative positions and motions of the [[planet]]s and [[natural satellite|moon]]s. It is usually a [[heliocentric]] model.<ref>King, Henry C. & Millburn, John R. 1978. ''Geared to the stars : the evolution of planetariums, orreries, and astronomical clocks''. Toronto: University of Toronto Press. pp. 28–41. {{ISBN|0-8020-2312-6}}</ref> The Greeks had working [[planetaria]]. The first orrery that was a planetarium of the modern era was produced in 1704.<ref>Calvert, H.R. 1967. ''Astronomy: globes, orreries and other models''. London: H.M.S.O.</ref> One was presented to [[Charles Boyle, 4th Earl of Orrery]] – hence the name. They are usually driven by a [[clockwork]] mechanism. The globe in the centre represents the Sun, and a planet is at the end of each arm. The first known orrery was the [[Antikythera mechanism]], variously dated from 60 to 150 [[BC]]. == References == {{reflist}} [[Category:Scientific modeling]] [[Category:Machines]] [[Category:1704]]