Here is another variation of the spherical gravity concept. Once again rendered in Blender. This scene uses the special physics system written by coder, Aligorith. This system offers Blender users some of the features found in Cinema4D MoDynamics.
The “saturn balls” are not particles, instead they are rigid body physics participants. The two larger spheres each contain an Empty which has a force field applied to it. The force field strength is modulated by an f-curve modifier. Both spheres have the same modifier, except one sphere is set to SIN wave generation and the other sphere is set to COS wave generation. This phase differential in strengths creates a beat pattern and causes the saturn balls to move back and forth between the spheres. There is also a larger invisible sphere around the whole setup. This larger invisible sphere is also a physics participant. If any of the smaller saturn balls escape the oscillating force fields they encounter the invisible ball which has it’s surface set to a “rubber” setting which causes the escapee to bounce back into the range of the oscillating fields.
Here is a link to the development thread, which contains BLEND files and a link to Aligorith’s special build of Blender which rendered this video: