"As I understand it, the space into which the cosmos is expanding is not metaphysical, in the philosophical sense of the word; it is just not physical." ~Revl.
I understand you're not playing word-games. There are some ideas that are difficult to understand and articulate. This is almost certainly one of them. I suspect that few if any physicists would consider this "space" non-physical.
Definitely not 3 (or 4 dimensional) "Riemannian Space" or "Minkowski Space;" and possibly not even "Hausdorff Space" (in which any two distinct points can be separated by a function). More likely it is something like "de Sitter Space" (the inside of a black hole?).
...but look at this about "our 3-D space." I knew it was an artifact...."Dimensionality and fractals" ( doi:10.1016/S0960-0779(02)00028-0 )
Chaos, Solitons & Fractals, Volume 14, Issue 6, October 2002, Pages 831-838
B. G. Sidharth
Abstract
In this paper we first show that the usual three dimensionality of space, which is taken for granted, results from the spinorial behaviour of Fermions, which constitute the material content of the universe. It is shown that the resulting three dimensionality rests on two factors which have been hitherto ignored, viz., a Machian or holistic property and the stochastic underpinning of the universe itself.
However the dimensionality is scale dependent in the sense that at very large scales, or at very small scales, we encounter a different dimensionality, as indeed is borne out by observation and experiment. For example the large scale structures in the universe are cellular in nature on the one hand, and we encounter fractional charges and handedness at very small scales.
Finally it is shown how fractal dimensions can emerge and as an illustrative example it is shown how this could explain the magnetism of objects like Planets on the one hand and White Dwarf stars and Pulsars on the other.
