Galileo is called as the father of modern science because of his discoveries in astronomy and physics. He was sent to study medicine by his father, but he chose his career in science and mathematics and made the first telescope to observe stars and planets. He also discovered the law of pendulum as he watched a chandelier swing in the cathedral of Pisa. He also discovered that the surface of moon was not smooth but contained burrows and holes to what he called crater. He also discovered 4 revolving moons around Jupiter which are named after him. He proved what Copernicus said about sun being the center of the solar system. Galileo became blind in his old days and died in the year 1642. Galileo Galilei was an Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him. Telescopic Discoveries In the spring of 1609 Galileo heard that in the Netherlands an instrument had been invented that showed distant things as though they were nearby. By trial and error, he quickly figured out the secret of the invention and made his own three-powered spyglass from lenses for sale in spectacle makers' shops. Others had done the same; what set Galileo apart was that he quickly figured out how to improve the instrument, taught himself the art of lens grinding, and produced increasingly powerful telescopes. In the fall of 1609 Galileo began observing the heavens with instruments that magnified up to 20 times. In December he drew the Moon's phases as seen through the telescope, showing that the Moon's surface is not smooth, as had been thought, but is rough and uneven. In January 1610 he discovered four moons revolving around Jupiter. He also found that the telescope showed many more stars than are visible with the naked eye. These discoveries were earthshaking, and Galileo quickly produced a little book, Sidereus Nuncius ( The Sidereal Messenger), in which he described them. He dedicated the book to Cosimo II de Medici (1590-1621), the grand duke of his native Tuscany, whom he had tutored in mathematics for several summers, and he named the moons of Jupiter after the Medici family: the Sidera Medicea, or "Medicean Stars." Galileo also had discovered the puzzling appearance of Saturn, later to be shown as caused by a ring surrounding it, and he discovered that Venus goes through phases just as the Moon does. Although these discoveries did not prove that the Earth is a planet orbiting the Sun, they undermined Aristotelian cosmology: the absolute difference between the corrupt earthly region and the perfect and unchanging heavens was proved wrong by the mountainous surface of the Moon, the moons of Jupiter showed that there had to be more than one centre of motion in the universe, and the phases of Venus showed that it (and, by implication, Mercury) revolves around the Sun. As a result, Galileo was confi rmed in his belief, which he had probably held for decades but which had not been central to his studies, that the Sun is the centre of the universe and that the Earth is a planet, as Copernicus had argued. Galileo's conversion to Copernicanism would be a key turning point in the scientifi c revolution.