Gravity, or gravitation, is a phenomenon that makes masses move towards one another or makes one move around the other in a circular or elliptical path. This includes atomic particles like electrons and atoms to cosmic masses like planets, Sun and stars. On Earth, weight is a consequence of gravity and the Moon causes the tides on Earth. Gravity, as we will learn in the lessons is proportional to the product of masses of interacting body and inversely to the square of the distance between them.($25)