As the radial distance between two objects increases, the gravitational force which pulls the two towards each other decreases following the inverse square law. This is based on Newton's Law of Universal Gravitation, which as an equation states [tex]F_{g} = \frac{Gm_{1}m_{2}}{r^2}[/tex]. If the distance between the two is doubled, the force of gravity is only 1/4 as strong. If it is tripled, it is only 1/9 as strong, and so on.
