You have read that the each is round. However you do not fall off the earth even if you are at the sides or the poles. Why? This is because the earth pulls you towards itself. The earth has a power of attraction through which it pulls objectu towards itself. This power is called earth gravita ty ional force or gravity. All heavenly bodies likes the moon planets are stars have a force of gravity. Solar system the family of heavenly bodies around the sun is called the solar system.