Superconductivity is one of the parts of Physics creating major problems to theoreticans. Discovered in 1911 for mercury in 4K temperature, it waited until 1957 for an explanation (J. Bardeen, L. Cooper and J.R. Schrieffer, BCS theory, do not mix with the crazy cows desease ). Shortly after BCS received the Nobel Prize (1972) , brand new class of materials was discovered (1986): metal oxides which superconduct in temperatures of liquid air (77K).
Expected revolution however did not come, because materias made from copper, barium and ytterbium oxides are delicate and expensive to produce. Recently, a new shuttle between Shanghai and its airport was opened, using a levitating train, with semiconductors instead of wheels.
But new surprises are at the door: in 2001 at Kyoto University, a new alloy was discovered (or rather an inter-metallic molecule MgB 2) superconducting in temperature 39 K.
Superconductors shows extraordinary properties when placed in very low temperature. In the film below you will see levitating superconductor over the magnet, "perperuum mobile" made with use superconductors. You will see also so far unexplained phenomena - rotating superconductor independently on its positron.
There is no end for the surprises - a year ago (2002)
it has been found that pure lithium is also a superconductor, but only at
high pressures.
We are waiting for
a superconducting solid hydrogen!
* N.W. Ashcroft, Putting squeeze on lithium, Nature, Vol. 419 (10 October 2002) p.569