Hi.
Gravity is not the only fundamental force which rules in this universe.
One of the other fundamental forces you will recognize is Electromagnetism.
I stumbled upon some nice java based demonstrations of the Electrostatic
and Magnetostatic forces some months ago and I would like to share it with you:
Electromagnetic Waves2D Electrostatic Field Lines3D Electrostatic Field with Particles3D Magnetostatic Field with ParticlesThere are actually also some more pretty interesting applets on this site.
I especially love the demonstration of the kinetic gas theory.
Anyways, here's the full page:
http://www.falstad.com/mathphysics.htmlBy the way:
The formulas for the Gravitational force and the Electrostatic force are pretty much similiar. The big difference however is that the Coulomb constant is much greater than the Gravity constant. And of course the formula for the Electrostatic force works with charges, instead of masses.