Gravity and Gravitational Fields of Force
Until the time of Galileo science had been the servant of philosophy. Galileo gave it independence, and this act science has rewarded by being subsequently of much greater service to philosophy than ever before. But the problem of gravity remained a puzzle for a long time. The fact that it acts upon all bodies at the earth's surface was not understood for many years. It was Newton, in 1687, who first enlightened us concerning these phenomena, when he showed that gravity is only a special case of an attractive force which exists between all bodies wherever situated. Newton proved that the motion of the planets around the sun, as expressed by the three laws of Kepler which were deduced from careful experimental observations, was an immediate consequence of his assumption that the planetary motions were regulated by a mutual attraction between these and the sun.