If we use only rest mass as the source of gravity, but use the rest of general relativity. What are the differences with observations. Excluding cosmology and dark energy. I mean real observations, not just theory. I exclude from the question, cosmology, dark matter and dark energy. In my opinion 30% dark mater and 90% dark energy are a bit too suspicious. Gravity is so weak, that rest mass alone should still be good enough for 99% of observations. What are the 1% that fail? Of observations, and not cosmology!!! Don't tell me about the gravitational attraction between photons... we can't measure that. If you don't understand my exclusion criteria, just state all the differences you can think off, i'll just sort out what interest me. Can we detect differences in the solar system? Observed system of twin neutron stars close together? Just ignore the insides of the neutron stars, we can just assume theres more matter inside ( a difference i know of). Is there a difference in the way there orbit decays as they radiate gravity waves? About stars, only neutron stars would be affected in an observable fashion? We never observed a twin system of black holes right? My guess, that in general only very energetic phenomena are problematic. Of witch, only a few are observable.