Neither Einstein nor Newton explained or proved how masses cause the observed motions of the phenomenon we call gravity. Are such motions caused by gravitational waves or particles? None have ever been observed. Are they caused by gravitational lines of force similar to those of a magnetic field? None have ever been observed. Is gravity the result of the energy content of matter; an undetectable source or field of energy that pulls and propagates at a distance? Is it caused by something else? No one really knows.
The closest Einstein came to answering these basic questions was his generalizations of a “Newtonian field of attraction,” the “geometrical modification (‘curvature’) of space,” and his analogy to magnetic fields. Newton never really made an attempt to explain gravitational attraction, other than his conclusion that: “the force of gravity is of a different kind from the magnetic force.” Thus, De Sitter was led to conclude, “In the course of history a great number of hypotheses have been proposed in order to “explain” gravitation, but not one of these has ever had the least chance, they have all been failures.”
In prior sections of this treatise we have already empirically explained how and why the accelerating motions of opposing gravitational masses occur. These concepts are referred to as Relative Gravitational Acceleration and the Relativity of Gravity. But there are still at least three fundamental questions about gravity remaining to explore, and (by deduction and speculation) to attempt to answer:
1. Is the gravitational attraction phenomenon of a mass really caused by a force?
2. What is the root cause of the force of gravitational attraction?
3. How is gravitational force transmitted or activated?
Let us now explore and discuss these fundamental questions in the reverse order of their difficulty.