Pen and ink drawing of a planetary model made by Thomas Wright of Fleet Street, London. An orrery or planetarium is a demonstration model to show the motions of the Earth, Moon and planets around the Sun, in this example, using clockwork. Such devices became popular during the 17th century, especially after Sir Isaac Newton (1642-1727) published his universal theory of gravity in 1687. Thomas Wright made such extensive modifications in 1733 that this model has since been referred to as Wright's grand orrery.
© Science Museum / Science & Society Picture Library