I never understood why a vacuum isn't considered a superconductor. Surely there's nothing to resist the motion of an electron in a vacuum. Would anyone be able to explain that to me?
A vacuum isn't even a conductor, so it can't be a superconductor. Sure, the electors are unimpeded, but you have to boil them off something to get them into the vacuum. Conductors have a sea of electrons that moves very easily along the material. Which brings up a second point: once in the vacuum, the electrons travel in a straight line (except in the presence of electric fields). In a conductor, they follow the surface, which often bends.
Furthermore, a super-conductor excludes magnetic fields; vacuums do not exclude magnetic fields (otherwise Earth wouldn't have the Van Allen Belts).
