Gravity: You think you know it.

We all know exactly what the force of gravity is, or do we? Gravity is classically defined as an attraction between any two physical objects of a particular mass. Discovered by Sir Isaac Newton in 1687, the mathematician explained his findings in his book Principia. This article might help clear up any misconceptions you may have about gravity.

http://science.howstuffworks.com/environmental/earth/geophysics/question232.htm

For more advanced concepts on gravity, refer to this video from this YouTube called MinutePhysics.