okay lats think this through. For the sake of an accurate depiction of an unstoppable force and an immovable object, lets take A sphere for the unstoppable force and a wall for the unmovable object, of our hypothetical cosmic material. I call it cosmic material only in the sense that our civilization has yet to discover anything that could be rendered as either immovable or unstoppable. We then need to consider the medium that its traveling through, air, water or space. Assuming that to move through rock would possibly cause then destruction of the planet and make the whole conversation pointless. If our object travel through the air then the object by the laws of physics would heat itself by friction; whatever the outcome of striking the immovable object the release of the built up heat energy would be intense. and water would be little better because of the speed of which that we are assuming that they are traveling at. So, let us assume then that the object and the force are traveling through space at a high rate of speed. The immovable object needs to be truly immovable and I am not going to be able to even speculate on what it could be. But, given that the nature of the universe is just that, nature, everything must die. Therefore it would most probably be a built object. For the sake of argument I will use a giant metal wall as the immovable object and a giant metal sphere for the unstoppable force. So what would happen then? The Sphere would come hurtling through space and strike the metal wall, and assuming their unstoppability and unmovability one would assume for the sake of argument that these things where industructable as well. So, the sphere hits and what happens? the impact would send the sphere hurtling of in a different direction and both objects would remain unchanged,one immovable and one unstoppable. Though there could be a large release of energy upon the impact in space. But one would have to assume that the impact of two such things would inevitably create some sort of energy discharge, some sort of shockwave or concussive blast....Either that or it happens on a small scale and thats how planets are made...just a stoned ass thought