From the earliest discoveries of gravity and when students first learn about gravity, they are told it's a force. The force of gravity is equal to mass times the acceleration due to gravity or Fg=(m1m2/r^2. That is just a fact. Or is it? Gravitational forces are actually much more interesting than just the relationship between one mass and another. Gravity is the act of changing space-time. Gravity causes space-time to curve into a bowl like shape pulling masses into the center of it. As a planet is a massive object, its core pulls the space-time surrounding it toward itself, pulling the atoms of the planet toward its core as well as holding surrounding objects on the surface. As one goes onto the outer edges of the bowl, however, the force pulling them in decreases, because the slope of space-time is less. For this reason, Einstein's theory of relativity makes sense. As masses change the shape of space and time according to their size and mass, time and distance on one planet would differ from that of another.