The distant gravity object generates a constant gravity field that does not depend on the distance. It is useful when simulating real world gravity effects i.e. when the scale of events is so small that the gravity can be considered constant.
A distant gravity object includes two points, which define the direction of the gravity field. The length of the gravity line is irrelevant: the Strength of the gravity is controlled using the value at the property window's Spec tab. The default value 9.82 m/s^2 is approximately the gravity on the earth surface.