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Dr Bortz,

I have to take issue with you on one point. However heuristic Einstein’s thought experiment for the development of the field equations, the experiment describes an equivalence that’s purely mathematical, limited to the equivalence of the two trajectories. The astronaut, if inside a windowless craft, will be unable to detect an acceleration of her reference frame. The observer in the lab will experience a resistance to her gravitational acceleration toward the earth’s center of mass, and therefore will be continuously accelerated out of her gravitational path in spacetime. Thus, rather than say “a gravitational field is equivalent to an accelerated frame of reference”, it’s more accurate to say something like “the unobstructed gravitation of a body accelerates relative to other reference frames, whereas obstructed gravitation is absolute.”

Jim