Why can a magnet levitate over a superconductor?

Superconductors behave differently from ordinary materials when they are cooled below a critical temperature. They can expel magnetic fields through the Meissner effect, and in many materials magnetic flux lines become pinned in tiny defects, stabilizing a levitating magnet. Because of this, a magnet can hover above a cooled superconductor without mechanical support. The effect is dramatic in demonstrations using materials such as yttrium barium copper oxide, discovered in the 1980s as part of the high-temperature superconductivity revolution. This is not ordinary magnetism; it is a quantum state of matter with zero electrical resistance.