What is super conductivity?

							






















Early in 1947 all the newspapers carried reports of the breakthrough in superconductivity. For the first time the phenomenon had been observed at temperatures above that of liquid nitrogen, a substance variously described (depending on the audience) as cheaper than milk or cheaper than beer. M.K.Wu, in whose laboratory at the University of Alabama yttrium barium copper oxide had just been shown to be superconducting at these record temperatures was asked how long it might be before the new material would find widespread applications. He thought a year or two would be enough time.
Finally, three quarters of a century after its discovery, was this the time when superconductivity would emerge into the world of technology and cease t obe a laboratory curiosity and physicist’s plaything.
The first surprise was the discovery itself in 1911 by H.Kamerlingh Onnes and his assistant Gilles Holst at the University of Leiden in the Netherlands. 
In spite of the considerable cost and complexity of the refrigeration, hoth high field and low field applications of superconductivity were being developed even before superconductivity was found to exits also a much higher temperatures. The applications ranged from the superconducting magnets of the accelerator at the Fermi National Laboratory, which accelerated elementary particles to the highest energies, to the “SQUIDS” that record the magnetic fields generated by the human brain.