Gee, I just ranted in another thread about the low quality of knowledge exhibited by most of the posters in forums like BAUT in discussions of gtr, but I can see this thread might develop in interesting ways.

I'm new here, so I don't have solid impression of what math/physics background you two have, and this is pretty subtle stuff so I should probably try to come back when I have more time.

Ken, is it possible that you might want to ask about any or all of the following topics?

1. Newtonian limit (aka weak-field slow motion limit, giving the "correspondence" between gtr and Newtonian gravity),

2. Weak-field limit (aka "linearized gtr", often used for elementary theory of gravitational waves and early discussion of mass/momentum of isolated objects like rotating stars in gtr), or slightly more generally, linearized perturbations of more interesting exact solutions than Minkowski vacuum,

3. Ways in which nonlinearity manifests itself in gtr, e.g.

a. e.g. in the class of Weyl vacuums, all axisymmetric static vacuum solutions, it is not hard to work out a way to isolate the nonlinear contribution to the "superposition" of two Weyl vacuums to obtain a third Weyl vacuum,

b. symmetries of the field equations themselves, with or without conditions, e.g. for Weyl vacuum they reduce to a familar PDE, and then applying symmetries to Weyl vacuum solutions exhibits a notion of "mass" which varies from place to place,

c. etc.,

4. How can one try to build a mathematical model in gtr of an idealized situation in which two massive objects, or a massive object and a nongravitational field, "interact"? Given that this interaction will almost always create gravitational radiation? Given that the EFE provides a consistency check on a possible solution, i.e. a spacetime equipped with tensor fields representing various nongravitational forms of energy and momentum as appropriate, but by itself doesn't provide a prescription for finding such possible solutions?

5. When we write m and r in 1-2m/r in the most common way of writing down the Schwarzschild solution, what does this parameter m really mean and what does the coordinate r really mean? E.g. in comparision to another popular radial coordinate, the one which appears in so-called "isotropic" coordinates?

(Publius: sorry for the loss of your aunt.)