who came up with the idea of gravity
History of gravitational theory In the 4th century BC, the Greek philosopher Aristotle believed that there is no effect or motion without a cause. The cause of the downward motion of heavy bodies, such as the element earth, was related to their nature, which caused them to move downward toward the center of the universe, which was their natural place. Conversely, light bodies such as the element fire, move by their nature upward toward the inner surface of the sphere of the Moon. Thus in Aristotle's system heavy bodies are not attracted to the earth by an external force of gravity, but tend toward the center of the universe because of an inner gravitas or heaviness.[1][2]
History of ballooning Following Robert Boyle's Boyle's Law which had been published in 1662, and Henry Cavendish's 1766 work on hydrogen, Joseph Black proposed that if the gaseous element filled a balloon, the inflated object could rise up into the air. Jacques Charles, whose study of gases led to his namesake law of volumes, had studied the works of Cavendish, Black, and Tiberius Cavallo,[13] and also thought that hydrogen could lift a balloon.