Chronos said:
GR is an ad-hoc mathematical model? Going out on a limb is one thing, going out on a twig is another. Your reluctance to buy into a standard, or concordant model is acknowledged. Asserting GR is an ad-hoc mathematical model is not only outrageous [in my opinion], it is a reckless disregard for empirical evidence and a slap in the face to real scientists [i.e., those who have made the personal sacrifices and effort required to gather facts and make informed, rational conclusions]. Apologies for being blunt.
No need to apologize. It is not my intent to hurt your feelings, nor the feelings of anybody who subscribes to the "curved space-time" model of gravitation in GR. I do not use the term "ad-hoc" as a perjorative. I use it because the model does not explain how gravitation arises. Instead of explaining the mechanics of gravitation, Einstein modeled its behavior - there is nothing wrong with that, as long as we do not elevate his mathematical model to the status of "reality". Curved space-time is a mathematical model that works well in some circumstances. MOND is a mathematical model that seems to be a lot more predictive on galactic scales and larger. Neither model explains the mechanics of gravitation - they only model the
effects of gravitation.
Why should we want to know the mechanics of gravitation? Discovering the mechanics of gravitation is essential, if gravitation is going to be united with the other fundamental forces of nature. I repeat, GR's curved space-time and Milgrom's MOND are mathematical models that predict the effects of gravitation - they do not address the cause of gravitation.
I do not have a "reckless disregard for empirical evidence", nor is my investigation into the mechanics of gravitation a "slap in the face to
real scientists" (emphasis mine). There are
real scientists all over the world who support themselves in other jobs, and who may nevertheless make real contributions. In fact, observational astronomy is one of the most democratic of the sciences, and amateurs routinely make discoveries that are valuable to
real scientists (yes, emphasis mine). For my part, I try to sort through the various interpretations of observational evidence to determine where the problems lie that make the unification of GR and quantum theory difficult. That might not seem like much of a contribution to you, but it is interesting and compelling work.
If we are at a point where any particular theory cannot be questioned or subjected to falsification, then science is dead. I do not believe that this is the case, although in some instances, science may be on life-support.

We have to be especially careful about what you refer to as "empirical evidence", since all observations are filtered though our perceptions and prejudices. When a statement is prefaced by "obviously" or "as everybody knows", the warning flags should go up. We are only human after all, and despite our advances, we are no more objective and open-minded as a group than the peers of Kepler, Newton, and Einstein.