Hoku said:
... I tend to incorrectly say that when the proper phrase I should be using is "emergent spacetime view". From an emergent spacetime view, spacetime IS irrelevant before the big bang because, based on that view, it did not yet exist.
I don't see how that follows. There are theories where geometry emerges from some more fundamental degrees of freedom, which however can also exist before the beginning of expansion. I'm not sure what you mean by "emergent". It is a buzzword that people use various different ways. I don't see any reason why if spacetime emerges after the BB moment it could not emerge before the BB moment. No rational reason to believe that the same underlying stuff doesn't exist before. Fact is we don't know.
I'm not disrespecting James Overduin. As I say he's just not very prominent. In no way would I take him as an authority. And of course those two 2001 articles are different. I looked at the Springer sample too
The free one is a long review article with lots of references and my guess is that it gives a good idea of what he thought and said around that time.
You cite a general audience outreach 2007 article by him at the GravityProbeB website.
http://einstein.stanford.edu/SPACETIME/spacetime2.html
I don't altogether agree with it, but heck! Why not copy a sample excerpt here and see if anyone else has questions or objections?
==quote Overduin 2007==
Relational or Absolute?
In 1918, Einstein described Mach's principle as a philosophical pillar of general relativity, along with the physical principle of equivalence and the mathematical pillar of general covariance. This characterization is now widely regarded as wishful thinking. Einstein was undoubtedly inspired by Mach's relational views, and he hoped that his new theory of gravitation would "secure the relativization of inertia" by binding spacetime so tightly to matter that one could not exist without the other. In fact, however, the equations of general relativity are perfectly consistent with spacetimes that contain no matter at all. Flat (Minkowski) spacetime is a trivial example, but empty spacetime can also be curved, as demonstrated by Willem de Sitter in 1916. There are even spacetimes whose distant reaches rotate endlessly around the sky relative to an observer's local inertial frame (as discovered by Kurt Gödel in 1949). The bare existence of such solutions in Einstein's theory shows that it cannot be Machian in the strict sense; matter and spacetime remain logically independent. The term "general relativity" is thus something of a misnomer, as pointed out by Hermann Minkowski and others. The theory does not make spacetime more relative than it was in special relativity. Just the opposite is true:
the absolute space and time of Newton are retained. They are merely amalgamated and endowed with a more flexible mathematical skeleton (the metric tensor).
Nevertheless, Einstein's theory of gravity represents a major swing back toward the relational view of space and time, in that it answers the objection of the ancient Stoics. Space and time do act on matter, by guiding the way it moves. And matter does act back on spacetime, by producing the curvature that we feel as gravity. Beyond that, matter can act on spacetime in a manner that is very much in the spirit of Mach's principle. Calculations by Hans Thirring (1888-1979), Josef Lense (1890-1985) and others have shown that a large rotating mass will "drag" an observer's inertial reference frame around with it. This is the phenomenon of frame-dragging, whose existence Gravity Probe B is designed to detect. The same calculations suggest that, if the entire contents of the universe were to rotate, our local inertial frame would undergo "perfect dragging" — that is, we would not notice it, because we would be rotating too! In that sense, general relativity is indeed nearly as relational as Mach might have wished. Some physicists (such as Julian Barbour) have gone further and asserted that general relativity is in fact perfectly Machian. If one goes beyond classical physics and into modern quantum field theory, then questions of absolute versus relational spacetime are rendered anachronistic by the fact that even "empty space" is populated by matter in the form of virtual particles, zero-point fields and more. Within the context of Einstein's universe, however, the majority view is perhaps best summed up as follows:
Spacetime behaves relationally but exists absolutely.
==endquote==
