© Science Museum / Science & Society Picture Library
This planetary model was made by the London instrument makers Newton and Company. Called an orrery or planetarium, it is a demonstration model to show the motions of the Earth, Moon and planets around the Sun. This example has a wooden base with paper calendar scales and eight planets (Mercury to Neptune - the ninth, Pluto, was not discovered until 1930) on long rod-arms. Such devices became popular during the 17th century, especially after Sir Isaac Newton published his universal theory of gravity. To reproduce the motions of the solar system, this model employs a hand crank to drive the gear wheels. Models of this sort were commonly used in schools and colleges to teach astronomical principles.