Levitating Superconductors

The reason Levitation of Superconductors works is something called the Meissner effect and magnetic flux pinning. The Meissner effect dictates that a superconductor in a magnetic field will always expel the magnetic field inside of it, and thus bend the magnetic field around it. The problem is a matter of equilibrium. If you just placed a superconductor on top of a magnet, then the superconductor would just float off the magnet, sort of like trying to balance two south magnetic poles of bar magnets against each other.

When a superconductors is placed on a magnetic track, the effect is that the superconductor remains above the track, essentially being pushed away by the strong magnetic field right at the track's surface. There is a limit to how far above the track it can be pushed, of course, since the power of the magnetic repulsion has to counteract the force of gravity.

A flat disk-like superconductor will demonstrate the Meissner effect in its most extreme version, which is called "perfect diamagnetism," and will not contain any magnetic fields inside the material. (There is video to describe this more in depth to the right). It'll levitate, as it tries to avoid any contact with the magnetic field. The problem with this is that the levitation isn't stable. The levitating object won't normally stay in place. (This same process has been able to levitate superconductors within a concave, bowl-shaped lead magnet, in which the magnetism is pushing equally on all sides.)