'The Ptolemaic, Tychonic, and Copernican Sytems', 1798.
© Science Museum / Science & Society Picture Library
Engraving showing the solar system according to three astronomers. Ptolemy's (c 90-168 AD) theories of the universe dominated western ideas on astronomy until the time of Nicolaus Copernicus (1473-1543). The Ptolemaic system put the Earth at the centre of the universe with the planets revolving around it. Copernicus proposed a sun-centred universe, in which the Earth is merely one of the planets revolving around the Sun and rotating on its axis. Tycho Brahe (1546-1601) did not believe the Earth moved around the Sun, but thought that all the planets orbited the Sun, which rotated round a stationary Earth. Illustration from 'Encyclopaedia Londinensis, or, Universal Dictionary of Arts, Sciences, and Literature' published in London, 1810-1829.