Physic Circus is based upon a quantum property named superconductivity.
Superconductivity occurs in many metals at very low temperatures. When a metal becomes superconducting, it conducts electric current perfectly with no more resistance nor heating. In addition, if a magnet is approached, the superconductor generates electric currents that expel the magnet which make him levitate ! Discovery in 1986 of a new type of ceramic which exhibit superconductivity at much higher temperature than metals has opened a new field of research, one of the most active nowadays. But the origin of superconductivity in these ceramics is still one of the greatest scientific mysteries.
In the Physic Circus, many effects allow to discover superconductivity: levitation, pinning, symetries, temperature effect... To understand them, you have to explore the physics in the levitation, cryogenics, vortex and pinning, and magnets.