Since Newton's times, many people (including Newton himself, I think) have felt dissatisfaction with the theory of gravity because there was no explanation of the cause of gravity and of how it can act at distance. Forces that do not act by direct contact between the objects (for example: I kick a ball and the contact force makes ball move away from my foot) seemed mysteroius to many people. It is often claimed that Einstein solved this problem when he explained gravity as a consequence of the geometry of spacetime. I will in no way dispute the correctness of Einstein's General Theory of Relativity, but I never understood the problem with action at distance. For if we think a little, we realize that all forces must act at distance, including direct contact forces! The reason is that there must be a distance between any two objects, including objects which appear to be in direct contact with each other. Two objects cannot occupy exactly the same locations in space. In the example with me kicking a ball, there must be a distance, albeit very small, between the parts of my foot and the ball that we consider as in direct contact with each other, for otherwise those parts of my foot and the ball would occupy the same location in space, which is imposible. In fact, it is the electric repulsion between the electron clouds in my foot and the ball respectively, that constitutes the apparent contact force, and this replusion acts at a (very small) distance. It is analogous to when we try to bring the north poles of two magnets together with our hands. Then we can feel the magnetic repulsion in our hands and still see that it acts at dustance. So, since all forces must act at distance, I see no reason that we should be particularly skeptical against newtonian gravity or electrostatic and magnetic forces acting et distance, etc.