Galileo Galilei. Coloured historical artwork of Galileo Galilei (1564-1642), Italian astronomer and physicist. In 1610 he became the first person to use a telescope for astronomical studies. He discovered mountains on the Moon and the four largest moons of Jupiter. He found that all the swings of a pendulum have the same time period. He showed that heavy and light objects fall at the same rate. He supported the Copernican theory that the Sun was at the centre of the solar system rather than the Earth. This belief was judged heretical by the Inquisition in 1633 and he was held under house arrest for the rest of his life. Artwork based on a portrait by Ottavio Leoni.