See the end of the article for reproduction restrictions. We experience gravity every day and are familiar with its effects, yet many people don't have a clear understanding of what it is. With this article I'll try to clarify the concepts of gravity by examining three usages of the word itself. All objects with mass exert an attractive force on other objects of mass. This force, strictly speaking, is called gravitation.
Folks often refer to it as gravity, however.
The attraction is almost imperceptible, however, until you're dealing with a mass the size of a planet or larger. Widely separated bodies feel a lot less attraction than bodies that are close together. The equation contains references to two masses. For multiple masses, however, the two-mass equation can simply be used again and again. Remember, however, that an attractive force between masses requires at least two masses.