It looks like something out of a magic show, where the magician is able to defy gravity and float or levitate an object in midair with no apparent explanation. Check out this really cool video which is not a Vegas show, but an example of something called quantum levitation:
It’s not magic at all, but a very cool demonstration from the Association of Science-Technology Centers. It’s a demo from Tel-Aviv University on what happens when a superconductor gets trapped in a magnetic field. What you’re witnessing is something similar to the Meissner Effect.
The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. [...] The samples, in the presence of an applied magnetic field, were cooled below what is called their superconducting transition temperature. Below the transition temperature the samples canceled nearly all magnetic fields inside. They detected this effect only indirectly; because the magnetic flux is conserved by a superconductor, when the interior field decreased the exterior field increased. The experiment demonstrated for the first time that superconductors were more than just perfect conductors and provided a uniquely defining property of the superconducting state.
Diagram of the Meissner effect. Magnetic field lines, represented as arrows, are excluded from a superconductor when it is below its critical temperature.
Superconductivity and magnetic field do not like each other. When possible, the superconductor will expel all the magnetic field from inside. This is the Meissner effect. In our case, since the superconductor is extremely thin, the magnetic field DOES penetrates. However, it does that in discrete quantities (this is quantum physics after all! ) called flux tubes.
Inside each magnetic flux tube superconductivity is locally destroyed. The superconductor will try to keep the magnetic tubes pinned in weak areas (e.g. grain boundaries). Any spatial movement of the superconductor will cause the flux tubes to move. In order to prevent that the superconductor remains “trapped” in midair.