add custom forces

[entropyqueen]

It would be amazing to be able to add custom forces to make new interesting configurations. It could be use to simulate a stellar engine for exemple (by applying a constant force in a given direction on the sun)...

[Chelsea486MHz]

There are many ways to define forces. The 4 fundamental forces can be expressed as a coupling constant factoring a product of "charges" divided by the square of the distance between them.

Applying a constant force to specific bodies would be better achieved by transitioning the force computation model to force fields, and force fields could be manually specified by the user through formulas.