John, It might have more to do with fluidity than size. The earth is extremely small and insignificant compared with our own galaxy. However, it is fluid enough at the core to become noticeably oblate due to the spinning. (Actually, the magma is pretty sloshy.) A glass marble will also become oblate if measured with precise enough instruments (glass is a liquid, rather than a solid, it is just a stiffish liquid). A solid metal ball, or anything crystalline with rigid and well-structured packing of molecules, would be even more resistant to shape changing... but I think that would be due to the bonds holding the arrangement together. So a black hole would be dense... but wouldn't it also be fluid if all those bonds have been broken? Carolly