Galileo Galilei (1564-1642), Italian astronomer & physicist. Galileo is best known for his work Dialogue on the Two Chief World Systems in which he opposed the Ptolemic system that the Earth is at the centre of the Universe & supported the Copernican view that the Earth revolved around the Sun. He was brought before the Inquisition on charges of heresy & on June 22nd 1633 was made to recant. Galileo invented the pendulum clock & the thermometer. He also discovered 4 of the 14 satellites of Jupiter (the Galilean satellites) using a telescope devised by himself but based on theoretical work by earlier scientists.