I like the ping pong balls over the surface of a pool, that's a neat analogy. However, I am also not a physicist, but my impression is that this is something c

I like the ping pong balls over the surface of a pool, that's a neat analogy. However, I am also not a physicist, but my impression is that this is something closer to how a http://en.wikipedia.org/wiki/Lagrangian_point http://en.wikipedia.org/wiki/Lagrangian_point (in particular, the L4 or L5 lagrange point) works. In fact, I think the size difference thing they describe in the article is probably very similar to how gravity, and relative object positions work out based on their mass ratios. Kind of an equilateral force balance, with a self stable state that things will naturally gravitate towards if the background energy level is low enough. Course, then that makes me wonder if there's a 4-body version with a stable tetrahedron formation?