This is a "Theoretical Question" so go easy on me. Since an atom is mostly empty space is a Neutron also mostly empty space or just space? In other words, in the case of a Neutron star we start with a Star with a diameter of 1,000,000 miles and since the distance ratio between the electron and the nucleus is 100,000 to 1 we end up with a Neutron Star that is 10 miles in diameter. Now if the Neutron has the same empty space ratio, you would expect a Black Hole to have a diameter of 10 miles divided by 100,000 or approximately .528 feet then we get: V = 4/3 x pi x r3 then volume = 0.077 cu/ft. But if a Singularity has Infinite Mass in Zero Volume that would have to mean the Neutron was made up of nothing but space. Or would it maybe be "Quantum gravity will "probably" replace the zero volume of the singularity with some finite volume, but we don't have a theory of quantum gravity yet."?