One of the great works of science is the “Philosophiæ Naturalis Principia Mathematica” by Sir Isaac Newton (1643-1727) first published on 5 July 1687. This tome described the motion of physical bodies inventing a new scientific discipline called “physics.” It also gave the first mathematical description for the phenomena of gravity. Newton assumed invisible force acting at a distance between any two bodies which diminished in proportion to the inverse square of their separation.
This allowed him to derive the three laws planetary motion empirically discovered by Johannes Kepler (1571-1630) from fundamental principles. To accomplish this feat Newton employed mostly geometrical arguments but also invented the early mathematics of calculus.
A CLOCKWORK UNIVERSE
This result was that cannonballs on earth and the movement of the heavens could be precisely predicted assuming the same simple and orderly laws of nature. Indeed, all motion throughout the universe appeared to be determined and only a function of their initial or starting conditions, at least in principle. Mysterious forces of nature or cosmic karma had been entirely banished. This reinforced the earlier view of a “clockwork universe.”
Since this included our brains, it removed in a theoretical sense the possibility of a mind or soul which was previously imagined to have self awareness and free will. Since we are apparently not made in the likeness of God, the thought was that perhaps any supernatural entities were also non-existent.
The planet Mercury is not entirely predicted by Newtonian gravity.
Imagine two astronauts in heavy spacesuits suddenly teleported to outer space some distance apart. Initially they are at rest with respect to the other and wave hello. But even though they are stationary, they are also moving forward in time.
According to General Relativity each one warps the space around them by virtue of their mass. This expansion and compression of space propagates outward at the speed of light until it reaches the other in a “gravity” wave which each can sense using delicate instrumentation built into their space suits. And this warping is bigger close by each one and less so further away.
But the effect of this warp is that the distance between them is now less. Because of this change of separation, each astronaut now experiences a bigger warping because they are closer to the other one. And each notes the "wave" or distortion in space time from the other getting bigger.
Neither astronaut feels any force. From their point of view they both feel they are floating weightless in space but the distance between them is mysteriously getting smaller all the time.
Eventually they slam into each other and are stopped because two masses can't occupy the same space at the same time. Each apologizes even though they think the other one is at fault because they did nothing to cause the collision.
There is no mysterious force of “gravity” as envisioned by Newton, just a warping of space.
And energy warps the space around it as well…