Thank you for your reply. Your arguments forced me to have a look on some texts that came to my mind while reading you. Namely, I though about some of the ideas of Spinoza as you argued about space and time, for the Dutch philosopher thinks that thought and extent are the attributes of the one substance (which is infinite in itself, with an infinite number of attributes, each one of them being infinite), so that nothing is "outside" of it since, in fact, there does not exist any "outside". Well, I suppose that your own idea of space as an irreducible entity gets very close to Spinoza's conception. And referring to the concept of time as pure action, Spinoza says in the same tenor that action is the deployment of the substance (as a matter of fact, God, in the philosophical system of Spinoza) by means of the temporal unity of man. Ergo, time precedes existence, and human action needs time as a backdrop.
Indeed, information travels not at infinite speed, as we have a limit, c. Now, this reminds me that whatever we say, we pretend to know or to describe, we must have an irremovable referent, i.e. a frame of reference with respect to which we can say whatever: Ptolemy (Earth), Copernicus (Sun), Protagoras (man), sound (air), light (ether...or light itself), many human beings (God), etc., even this writing I am doing right now needs the referent of alphabet, language, syntax, and so on. Apparently infinite can only fit in human spirit; I think that is so for simultaneity as well. To will, more than to determine, is to get an idea of possibility: reality is the complex of possibilities. You remind me, once again, Spinoza when you say that free will is a sort of oxymoron, and I agree with you: we are not simply actors on the stage of space-time, but we rather create the stage being there and acting. But once this process begins, not only do we make the stage, but the stage makes us too. The main problem I see with determinism is not being simply false, because it is not, but that it pretends that everything is exclusively fixed by previous conditions, not allowing the appearance of novelty, of the radically unexpected, of emergence. Now, in fact, nature provides us with so many examples of emerging systems, proving that structures are not the ensemble of parts, but the collection of possible correlations between those parts, so far that even after the disappearance of them, correlations stay (e.g. fossils). That is why I think space as the trace of time (which is not duration), not as an effect coming out from a cause, unless we accept this view as the price to pay for our particular way on perceiving the phenomenal world.
About expanding universe, I do agree with you, provided they are not confused space and time as simple degrees of freedom. Physics has very often assumed homogeneity and isotropy of space, in an attempt to fulfill the conditions for solving non-linear equations, and that's understandable; however, we in general forget pretty soon that such conditions were exceptional and oversimplifying, so we entangle the feet with our own games. This is why I would like to talk about your phrase: "when we measure time, we measure actions, but when we measure space, be it distance, area, or volume, we are measuring space." What measuring is? Measuring is comparing couples of systems, assuming that one of them is, at least for a while, fixed. The "landing" or "shoulder" not in time, but in our understanding, are an indispensable condition for measuring anything. When we measure time we compare actions and when we measure space we compare historical moments, this is to say, places of the past. Of course, void is not the carbon copy of nothingness, since the former is actually something whilst the later cannot simply be, otherwise it wouldn't be nothingness. Light needs a propagation medium, which is light itself. Einstein spent almost twenty years before he realized that although it is true that ether as such doesn't exist, light does need a medium. I think that medium, light, is a direct property of the geometrical structure of space, this is to say, of time (from there the particular metrics of space-time).
I don't think there is a single center of the universe, i.e. it is nowhere or, equivalently, it is everywhere; as you assert right, each one is a fortiori the center of the universe; I'd rather prefer to say that each one is the center of his or her own universe. I am not quite sure though that either the presence or the absence of gravity is the only explanation of contraction or expansion, respectively, of space. I suppose science still has a very long way to go. However it is puzzling too the fact of remembering those old models (Greek atomists like Democritus, Descartes, etc.) praising vortices organizing reality; I am afraid that, for the time being, these are more philosophical than scientific subjects. Nevertheless, I hope scientific thought will eventually dig in them.
Thanks John and excuse me for the delay answering your deep reply.