1. IntroductionEither space has mass or it doesn't. A space without mass is a massless space. Massless space is the mathematical limit as a massy space's density goes to zero. The usefulness of this idea and the insights to be gained from it were shown in a previous paper.  This paper will show how this can lead to a new understanding of Newton's universal gravitation.
In that paper we showed that treating space as a "body" in the framework of Newton's laws was entirely consistent with those laws. We also showed that the three laws of Newton are really only one.
2. The Problem Won't Go AwayPrevious attempts to cope with the problem of space was to deny its existence as a physical entity. Descartes filled it with material "ethers" consisting of physical "stuff" of various kinds with specific material properties.  Newton's "action at a distance", an idea many called "occult" at the time, won out, and has prejudiced our thinking about physics ever since. 
But Newton himself was troubled by this, as revealed in a letter:
That gravity should be innate, inherent and essential to matter, so that one body should act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their force may be conveyed from one to another, is to me so great an absurdity that I believe no man who has, in philosophical matters, a competent faculty of thinking, can ever fall into it. Gravity must be caused by an agent, acting constantly according to certain laws, but whether this agent be material or immaterial, I leave to the consideration of my reader.Clearly Newton was admitting that the agent responsible for gravity might actually be immaterial, or massless. Yet physicists continued to assume that space was filled with a "material" substance, the luminiferous ether, and they fully expected it to have at least some small mass density that could be experimentally detected.
In the 18th century physicists discovered electric and magnetic fields, and light as an electromagnetic phenomenon that could propagate through space. That was troublesome, and attempts were made to revive the idea of an ether-filled space to give light something to "wave in". It also provided a medium for fields, that could now be interpreted as stresses and strains in the ether. 
Physicists abandoned the ether when relativity theory was adopted. They had enough to do just trying to understand and test the predictions of relativity. But the nagging question "How can bodies exert forces through intervening nothingness" persisted. Independent thinkers tinkered with the ether idea, but were ignored or ridiculed by the larger scientific community. [5, 6, 7]
3. Let's Get Real About SpaceThe answer, it seems to me, is to treat space itself as a legitimate physical entity or "thing", on an equal basis with other concepts of physics, such as mass, energy, momentum, photons, etc. For too long mainstream science has dismissed space as "nothing", and hasn't bothered to investigate the properties of space itself. An example of the confusion this cases in student minds is illustrated by these textbook definitions: "Space is the absence of matter" and "Matter is that which fills space." Very enlightening!
The virtually unknown physicist, Konrad Finagle (1858-1936) explored this notion in his "Theory of the Void". In that work we find this perceptive comment:
Consider what would happen if you took away the space from between matter. Everything in the universe would scrunch together into a volume no larger than a dust speck. We notice that hasn't happened. Why not? Something prevents it. That something is space itself... Space resists being pushed about. Space is what keeps everything from happening in the same place. We should finally admit that even empty space is every bit as real as anything else we talk about in physics. Space is just matter with zero density.
4. Pushing Space AroundFig. 1 was schematic only. Actually space completely surrounds objects. Consider a single object isolated in space. Assume that space exerts force on the body and the body exerts forces on space, in accord with Newton's third law. If space is symmetrically distributed around the body its net force on the body is zero by vector addition.
But now introduce into this picture a second body, B, some distance from the first. The presence of this body destroys the symmetry of space by pushing aside a volume of space equal to its own volume. Now there's a net force on each body due to this asymmetry. Again, Newton's third must be satisfied.
5. The vacuum abhors matterAristotle taught that "Nature abhors a vacuum". Perhaps it is the other way around. Suppose that "The vacuum abhors matter." When a body, like a planet, intrudes into space, pushing space aside, space reacts by trying to re-enter the volume occupied by the planet. This exerts a force all around the planet's volume that only serves to push the matter of the planet more firmly together. This inward rush of space toward the center of the earth is also responsible for the fall of the apple, and all other motion we attribute to "the force of gravity". It also sweeps nearby objects, such as the moon, toward the earth, balancing its centripetal force, and keeping the moon in a stable orbit.
The so-called mutual attraction of the earth and moon is really due to the fact that each body "gets in the way" of part of the inrushing vacuum, lessening its force on each body on the side nearest the other body.
On the grander cosmic scale, we see that this tendency of space to reclaim territory occupied by material objects is responsible for the motion of everything, every where. It's a grand tug of war between the vacuum and intrusive matter, and neither one wins in the short run.
6. Much Ado About
Look around in the universe and what do you see? Well, you see lots of
aggregates of stars called galaxies, that often look like rotating pinwheels.
Of course the rotation is glacially slow, but the evidence is overwhelming that
the most universal feature of the universe is that everything is in rotation.
That's just what our theory would predict. Look at water flowing down a
sink drain. It forms a rotating vortex. In the universe, vacuum flowing toward
masses also forms vortices, or whirlpools as a result of centrifugal forces.