Superconductivity

A number of people have indicated they would like to learn about superconductivity. Perhaps on Monday we can discuss that.  In superconductor there electrons near the fermi surface pair with each other. This is pretty surprising.  (Electrons typically repel each other.  Why would electrons pair?)    

Anyway, these pairs of electrons are bosons and a superfluid bose condensate can form that is able to transport  current (charge) with no resistance. Superconductivity is an unusual and completely unexpected phenomenon. The idea that "more is different" in physics are partly motivated by the emergence of the superconductivity and the difficulty of explaining it in a reductionist manner.