Quote:
Originally Posted by George
However, I think we disagree here, just maybe. A causal foundation to any model has to be superior to one that offers little or no causal explanation if both models give the same predictions.
|
I think you are asking the key questions, but there may be one thing you haven't recognized, which is that GR largely removes the issue of causality from all levels of motion other than the most deeply geometric. In other words, in GR we only ask what is "causing" the curvature of spacetime-- the motion within that spacetime is 100% purely a question of reference frame. So there is a spacetime with all the right geometry (caused by the Sun's gravity) in which the Earth is stationary and the Sun orbits the Earth. In that spacetime, the motion of the Sun derives from the coordinate chart we have chosen to give values to the quantities that describe the positions of things-- which is completely arbitrary once the geometry is fixed.
You can think of this like taking your favorite vase from your living room, and deciding on a way to specify quantitatively the location of every point on the vase. You can put a "coordinate chart" on the vase to do that, and you can do the chart any way you like. However, once done, if you ask questions like how tired does an ant get crawling between various points, the answer will depend on some things that are special to your coordinates, and other things that are special to the shape of the vase. The former is arbitrary, the latter is the only thing in need of a "cause" (the shape of the vase).