An analogy of this interaction can be made by referring to the masses as two circular hovercrafts operating on a circular lake, surrounded by cannons that are constantly firing shot towards the centre of the lake. Each craft also has cannons that surround the periphery of the hulls and are constantly firing shot radially outwards. The craft are already in motion and the reaction and action of the cannons and shot are in equilibrium, thereby having a zero net propulsive or directional effect on their motion. However, as the craft approach, they begin to shield each other from some of the shot being fired from the periphery of the lake, thereby reducing the impact on the approaching areas of the crafts. Shot fired from these approaching areas of the crafts cannons, increasingly impact each other in flight with decreasing proximity, deflecting off each other and thereby reducing the impact on the craft. The net effect resulting from these factors is to reduce the impact forces acting between the approaching areas of the crafts, thereby allowing them to be pushed together with a force that is inversely proportional to the square of the separation between the two craft.