There appears to be a basic dichotomy going on. The difference between the manner in which a solid and a liquid object spin, is part of human mythology, it has been used to tell apart boiled eggs from raw eggs for literally Millenia. Some particularly gifted persons can even tell apart well boiled eggs from partially boiled eggs by the act of spinning them. The point is that the difference in spins between objects with a solid core and those with a liquid core is based on observable, discernible, measurable, empirical facts. The question that then arises is this; when there is a choice between two options; one based on empirical facts and the other based on reasoned but invisible and (essentially) undetectable facts; which option is preferable? It has been reasoned here in this thread, that given the comparative mass of the sun and mercury, it is only the mass of the sun that determines the orbit of mercury. Obviously, this is not true for were it true, Mercury’s orbit would have been far less elliptical than it is, other unknown but ponderable reasons must be responsible for Mercury’s orbit. As regards its precession it appears that there is a general ignorance of the magnitudes involved. One arcsecond amounts to 1/3600 th of a degree. That is small, to say that a variation of 43 arc seconds per century is incredibly small is therefore no exaggeration. Given that this is so, isn’t it possible, if not probable, that this difference in the precession of the perihelion of Mercury is due to the movement of the partially solid core rather than to some fantastically complicated calculation involving the bending of space and time. Further, it should be considered, that this fact about Mercury’s core being partially liquid has only recently come to light through sophisticated probes and calculations and was not known at the time of Einstein’s General relativity explanation in 1915. n.b. Many thanks for link posted by Helio