> Now add a third body, and yes, in some sense this system is still described by the simultaneous relationship between pairs of bodies, but it's not really usab

> Now add a third body, and yes, in some sense this system is still described by the simultaneous relationship between pairs of bodies, but it's not really usable in that form. The third body makes the system nonlinear and non-analytic, so the equations can only be investigated via numerical simulation. But the number of symbols is still small. It may be the case that most of the universe is nonlinear and we only pay attention to the linear parts because they're easy. It might also be the case that a lot of the universe requires a lot of symbols to describe but we only pay attention to the other part.