Galileo, (Galileo Galilei), 1564-1642, Italian astronomer, mathematician, and physicist. At the age of 19 he discovered the principle of isochronism-that each oscillation of a pendulum takes the same time despite changes in amplitude. Soon thereafter he became known for his invention of a hydrostatic balance and his treatise on the center of gravity of falling bodies. He found experimentally that bodies do not fall with velocities proportional to their weights, a conclusion received with hostility because it contradicted the accepted teaching of ARISTOTLE. Galileo discovered that the path of a projectile is a parabola, and he is credited with anticipating Isaac NEWTON's laws of motion. In 1609 he constructed the first astronomical telescope, which he used to discover the four largest satellites of Jupiter and the stellar composition of the Milky Way, and in 1632 he published his Dialogue Concerning the Two Chief World Systems, a work that upheld the COPERNICAN SYSTEM rather than the PTOLEMAIC SYSTEM and marked a turning point in scientific and philosophical thought. Brought (1633) before the INQUISITION in Rome, he was made to renounce all his beliefs and writings supporting the Copernican theory. His last book, Dialogues Concerning Two New Sciences (1638), contains most of his contributions to physics.
In 1638, Galileo in his _Discourses Concerning Two New Sciences_, associated pitch with vibrational frequency and asserted the existence of "sympathetic vibrations or resonance"; in other words, the vibrations of one body can produce similar vibrations in another distant body.