Although the exclusion principle prevented the atoms within each half from colliding with each other, it permitted them to collide with atoms in the other half. So each half of the sample was able to cool the other. Finally the researchers removed one half. The remaining 780,000 atoms quit evaporative cooling and displayed the distribution of energy levels demanded by quantum mechanics and the exclusion principle, rather than the classical gas laws that govern large collections of atoms. If a condensate were observed, it would be an extremely important finding.
Superconductivity involves pairing of electrons, which are fermions.
The gas on the left contains about 2.5 million atoms at a temperature of 2.4 millionths of a degree above absolute zero. Make either of them so cold that they are nearly motionless, and they start to behave in two different, but equally weird, ways. Bosons collapse into a conglomerate called a Bose-Einstein condensate in which all the atoms occupy the same physical state. But an inviolable law of nature prevents two fermions from being in the same state. So instead of clustering, they arrange themselves into layers of successively higher energies.