The only thing I’ve been able to find about this is that in superconductivity, you get surface currents the exactly cancel the field that would otherwise penetrate, and yes I know sometimes it penetrates slightly, London penetration depth, etc... but this doesn’t explain much. A normal conductor also has surface current so why doesn’t that expel magnetic fields? I know how super conductors work, there is cooper pairing due to phonon exchange which is allowed due to lack of thermal energy, hence why there is a critical temperature. But what is actually going on to expel magnetic fields that doesn’t happen in normal conductors? Is it really due to the location of where the actual current is? I.E surface current in superconductors versus evenly distributed current density in normal conductors. If so, what is it about superconductors that leads them to have all the current at the surface? Is that just the geometry of cooper pairing?