The gravity is the attraction force between the Earth and everything on it. It is known to be the weakest nature force, but it not only holds the thing on the Earth, but also it manages to keep together the galaxies and the whole solar system. In the ancient times the Greek philosophers were convinced that all the motions of the planets and stars were completely independent from the events happening on the Earth. The heaven was the kingdom of their gods and there existed the perfection. One of Greek philosophers was Aristotle, who thought that all the planets and the stars followed the "natural" motion. The force, that was believed to make them available to move, also made the contact between all these heavenly bodies.
Today we know the described force is the gravity and it works untouched the other objects. The idea of the Greeks remained to the 16th century. Then the understanding of the force of gravity was completely changed by such scientists as Galileo and Newton.
