Isaac Newton discovered that the same phenomenon that caused apples to fall from trees, was also the reason that the planets orbited the Sun. He was able to use mathematics, even inventing Calculus in the process, to accurately describe the motions of the planets. He was also fundamental in developing physics.
Newton determined that all objects in orbit around the Earth and Sun were in fact falling. The reason that they do not hit the Earth, is that they are traveling so fast that they fall all the way around the Earth or Sun. This explained the ellipse shape, and Kepler's Third Law.