Concerning any and all phenomena which we catagorize under "attraction/repulsion" or "gravitation/levitation"; the things we associate with the four invisible forces, the most objective observation that can be made is that the space, the distance separating the two (or more) bodies, is either deflating or inflating. No net change is observed in the bodies themselves. Only their apparent positions in space have changed as a result of the deflation (in the case of gravity) of the space between them. The position-change observation is secondary to the deflation-of-space observation because any of the "participating" bodies can easily regard themselves as standards of rest. Either any of them can or none of them can. But without regard to frame of reference, all observers must agree on either an inflation of space (in the case of a "repulsive" force) or a deflation of space (in the case of an "attractive" force) between the bodies involved. The degrees of spatial deflation (we're talking about gravity from here on out) may vary from vantage point to vantage point, but there is obviously no vantage point in the universe from which it appears that the Earth is "repelling" the apple instead of "attracting" it. Written more precisely, there is no reference frame in space-time from which it appears that the space separating the Earth and the apple, or the skydiver, is inflating. Falling is falling is "falling". There is a fourth spatial dimension and if we had to give it a name like up/down, right/left, or front/back, it would have to be in/out. It is the dimension through which motion is represented three-dimensionally as omnidirectional expansion or contraction. There is no qualitative difference between an object whose surface is perpetually expanding and an object whose center is perpetually shrinking. In both cases, the distance separating the center and the surface is increasing. Fourth dimensional motion is just as relative as three-dimensional motion. Say two bodies are floating in empty space and they are both expanding omnidirectionally (in "all" six directions simultaniously and proportionally) at identical rates of expansion. Relative to one another, they would regard each other as maintaining constant, unchanging size. Both bodies would, however, register a deflation of space, on account of their actual expansions. They observe no net expansion on their parts because they naturally regard themselves as standards of fourth dimensional rest. Indeed, they are probably not even aware of this fourth spatial dimension through which they move. (It is actually an over-simplification to say that both bodies would observe no net expansion. In fact, body A would observe the expansion of body B along with the deflation of space between them, and vice versa. We think that our minds are tricking us when they use size to represent distance, but the objective line between size and distance turns out to be more blurry than that.) Proceding with the over-simplification for now, all bodies A and B think they see (observers on their surfaces) is the deflation of space between two seemingly unchanging bodies; bodies whose positions seem to be changing as a result of the spatial deflation between them. But in all actuality, the positions of the two bodies' centers of gravity is never changing. The centers of gravity of the two objects are at rest relative to each other while in "free fall". Only their surfaces are accelerating toward each other. Remember that the above two-body example was in empty space with no local markers to reference. The two bodies were not expanding at identical rates right next to a third body which was not expanding at all. But let's just say for a second that there was some third body there which was "maintaining constant size". To bodies A and B, naturally regarding themselves as fourth dimensional standards of rest, the third body would not be maintaining constant size, it would be shrinking. If the observers on bodies A and B were particularly insightful, they might question whether body C was really shrinking or getting farther away from them, but they would hardly jump to the comclusion that they were expanding and that body C was not. It is just as natural to assume that we are maintaining constant size as it was to assume that the Earth was at three-dimensional rest while the Sun and stars revolved around us. Both assumptions, however natural, are incongruent with observation. In truth, the expanding objects are expanding and the shrinking objects are shrinking, just as the Earth, Sun and stars are all in constant motion. Returning to the over-simplified two-body example, assuming that there is nothing around to spoil the illusion, both bodies (as long as their rates of expansion are identical) would regard themselves and each other as maintaining constant, unchanging size. Now imagine an entire universe of "nothing to spoil the illusion"; a universe inwhich every single object was expanding at the same rate. Observers on every one of those objects would be tricked into thinking that they were maintaining constant size, while the space between them mysteriously got smaller. "All bodies attract!" one of them might say, mistakenly. Let us now say that in this imaginary universe the space itself was constantly inflating due to some biggish bangish sort of thing. There would be two equally valid ways to visualize this sort of universe. We could see it as a four-dimensional bubble of space-time whose boundary conditions are unchanging. In that case, it is a universe whose center is perpetually contracting. We could, instead, regard the center of the space-time bubble as a standard of rest, in which case it is a universe whose edge is perpetually expanding. Speaking most objectively, the distance between its center and its edge would be increasing. Now make space inflate at a constant rate (c?) and matter expand at an accelerated rate determined by the object-in-question's fourth dimensional kinetic energy (mass) and you have a working model for our observable universe. Bodies in our universe do not expand at identical rates but at varying rates dependent on the bodies' individual masses. Any center of "gravity" can be regarded as an inertial frame of reference and therefore, can be identified with the center of the expansion of the universe (the center of the four-dimensional universe's expanding three-dimensnional surface). Regarding the Earth's center of "gravity" as a standard of rest, it's surface is speeding away from it. That surface then strikes other objects (feet, basketballs, anvils, meteorites) and pushes them into accelerated retreat as well. Even objects which the Earth's surface does not strike are retreating on account of the constant inflation of space. To sum it up, distant objects are retreating from the Earth's center of "gravity" at the constant rate of spatial inflation while objects that reside on the Earth's surface are retreating at the accelerated rate of matter. The universe is an expanding four-dimensional sphere and any inertial reference frame; any body's center of "gravity", can be regarded as an arbitrary "pole" its three-dimensional surface. Any center of "gravity", even that of a neutron, is speeding away from its surface (or its surface is speeding away from it) at the accelerated rate characteristic of its mass. Since all bodies are conglomerates of uniformly expanding particles, the bodies themselves expand uniformly, as well. While space is only one part space, all matter is always some part matter and some part space. Even a neutron star must have some infinitesimal amount of space separating the neutrons that comprise it. For this reason, all bodies expand at both the constant spatial rate of inflation and the accelerated rate of matter itself. This is why matter can overcome spatial inflation when the ratios of matter to space in the "gravitational transaction" allow it. We can divide atoms into protons and neutrons and we can divide those into six different quarks. I believe that we will always be able to divide matter thusly because the space will always be there. There are six quarks instead of any smaller quantity of quarks specifically because space separates six different types. If there was no space separating two individual quarks, then there would not be two quarks but one quark instead. TANGENT - We are accustomed to imagining that our minds employ the "convention" of representing distance through size. Something that is far away from us "looks" smaller than it would "look" if it were closer. But we have begun to see that the distinction between distance and size has a less objective mode of existence than commonly thought. Picture two bodies a lightyear apart. Light leaves body A at time interval T1 and arrives at body B one year later at T2. According to our thoery, both body A and body B have expanded quite a bit since T1. Since the observers on body B are seeing body A as it was at T1, body A must look very small to them. The stars in the night sky look pretty small to me. I know that claim sounds crazy but consider the following. I see a computer monitor in front of me. Intuitively, I know that if it occupied the position in space that I am currently occupying; if we both hypothetically occupied the same position in space simultaniously, it would be a two foot cube. But it looks smaller than that when it is in front of me. Trusting my depth perception and operating on probably reasoning, I assume that the monitor is still two feet by two feet by two feet, but that it is now three feet away from me. Two eyes are two vantage points, two separate frames of reference, that our minds somewhat "artificially" combine to produce one image. But the universe should most properly be viewed through only one eye. Depth perception is, at least, partly illusory. With only one eye open, the computer monitor could just as easily be a two foot cube residing three feet from my retina as it could be a two millimeter cube residing three millimeters from my retina. It could, in fact, be any size-distance combination in between those two extremes. The rule is: size decreases by the square of the distance. It is an inverse-square law just like "gravity". Objects which we assume are large yet far away are in fact smaller and closer than we believe. There is no absolute standard of size just as there is no absolute standard of space or time. The actual size of something is as relative to your particular frame of reference as motion and rest are.