One of the most profound by-products of the general theory of relativity is the discovery that gravitational “force,” which we had so long taken to be a real and independently existing thing, is actually our mental creation. There is no such thing in the real world. The planets do not orbit the sun because the sun exerts an invisible gravitational force on them, they follow the paths that they do because those paths are the easiest ways for them to traverse the terrain of the space-time continuum in which they find themselves.
