second act: Adding gravity: to simulate the gravity I added a N-variable node and multiplied that with color node by a colormath node. The N-variable node defines the direction of the normal vector of a point on the sphere, I only need the Y-value which points in the opposite direction of the ground, so the x and the z value are set to zero and the y-value to -3. So if a normal vector points up  (in case of the upper side of the sphere) the displacement  will be negative and if he points downwards, the displacement will be positive.

-How can you improve things when you don't make mistakes?