A view of the universe in which the sun is taken to be at its centre. The model was first proposed by Aristarchus of Samos (310–230 bc) but dropped in favour of the geocentric universe proposed by Ptolemy (c.90–168 ad). Copernicus revived an essentially heliocentric view, which was upheld by Galileo Galilei against strong opposition from the church on the grounds that if the earth was not at the centre of the universe man’s position in it was diminished. In the modern view the sun is at the centre of the solar system, but the solar system is one of an enormous number of stars in the Galaxy, which is itself one of an enormous number of galaxies.