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David,

[I wrote the following before I noticed your more recent, most interesting post. I’ll have to address it later.]

You may be disappointed. I wonder if you’re more disappointed than I am. You’re asking me to consider multiple universes and giant rings of dark matter that may undermine my position in some unspecified way (who could say?), before you’ll consider the behavior of two test particles in a box to be persuasive. Forgive my frivolity, but time may run backwards in Universe D11, gravity may be Newtonian on the Planet of the Apes, but I’m absolutely convinced that scientists in those places are primarily concerned with their own physical laws. I just wish they would jump in here at ScienceBlog with some learned advice on methodology – or ygolodohtem no ecivda, as the case may be.

You mentioned Occam's razor. I’d like to say to everyone, among whom you are just the most patient and articulate representative: Why don’t we proceed with just our one empirical world, with one set of empirically-established physical laws, before imagining how they might be effected if it turns out we’re just, say, the lint in some higher being’s navel (pierced with a safety pin of dark matter). I think I’m right about this: It’s the way good scientific methodology is supposed to be practiced.

I’ve argued that there is no controlled experiment in this world of accepted science where test bodies moving in geodesics in a gravitational field (with non-zero curvature) can be observed to behave like test bodies being accelerated (directly or indirectly) by a force. It’s a testable claim. By scientific standards, it prevails against un-testable models or hypotheses. But no one, it seems, wants to confront the issue, no one wants to give up a cherished doctrine.

Moving on to your earlier post, I think everyone’s concern, and aversion to “looking through Galileo’s telescope”, is expressed in your question: “Are you aware that if we can never detect gravitational waves that the theory of General Relativity may be in real trouble?”

I think you mean energy-bearing waves, because I’m not claiming that changes in curvature aren’t propagated as waves of changing curvature. I’m not an expert on the field equations, but I believe the stress-energy tensor can be simply dropped, leaving the rest of the structure intact, leaving the association of gravitation with force and energy behind. If not, some modification of the remainder should be possible. My belief in this stems from the coherence of the concept of gravitation as a curvature or distortion of spacetime, and of its affects on geodesic motion. So yes, I am taking issue with an aspect of GR, but no, I don’t think it’s life-threatening.

You wrote: “You appear to accept that ‘as the tides make clear’ that a moving mass can, indeed, cause motions that can be quite energetic (when integrated over the very significant volumes affected, at least in the case of the tides). Whether one wishes to use the term ‘energy’ in this regard is semantics. The reality is that energetic processes ‘happen’, and are well associated with the movement of at least a nearby object.”

This isn’t semantics. The orbit of the moon would require a great deal of energy if it weren’t for a geometric effect that makes it a curved geodesic path. No one seems to be attributing the moon’s orbit to force anymore. The changes in the local geodesics on earth produced by the changes in the relative position of the moon are no different, except they stress molecular binding energies, and in aggregation, produce massive dislocations of large fluid bodies. The effect is wave-like. Given a clear distinction between gravitation and force, by the application of Occam’s razor there is no need (and certainly no evidence) to support an additional wave-like, energy-bearing effect from cosmological sources. Is it justifiable to continue to look for such an effect? I suppose it depends on the budget.

“I could certainly understand a ‘layman’ like explanation using an ‘energy’ (and maybe even a ‘force’) like argument in order to try and convey the concept of gravitational waves, but I have yet to see a truly General Relativistic argument made in such terms. I don't know, I'm just trying to make sense of where you actually stand.”

Given the seminal concept of gravitation in GR, of the geometric effects of mass, in view of the inability to demonstrate an equivalence of gravitation with force and energy when they are considered in isolation, the aspect of GR that presumes an association of gravitation with force and energy can be seen as a legacy of the previous paradigm. To drop that aspect of GR is a simplification of physical theory, it brings theory back in line with empirical evidence. It could re-direct theoretical energies in productive directions. It could be good.