How Scientists Created The Fifth State of Matter

Most people learn four states of matter in school — solid, liquid, gas, plasma — and come away with the impression that the list is complete, that science has categorized every form matter can take and the question is settled. In 1995, two physicists at the University of Colorado used a laser and a magnetic trap to cool a cloud of rubidium atoms to a temperature so close to absolute zero that something happened that Einstein had predicted seventy years earlier and nobody had ever managed to produce: the atoms stopped behaving as individual particles and collapsed into a single quantum entity, all occupying the same ground state simultaneously, moving as one, described by a single wave function — a form of matter so strange and so unlike anything that exists anywhere in the natural universe that it required an entirely new category to describe. This explainer traces the full story of the Bose-Einstein condensate: the theoretical prediction that Satyendra Nath Bose and Albert Einstein assembled in 1924 and 1925 from a radical new way of thinking about quantum statistics, the seventy-year gap between prediction and experimental realization during which the physics community argued about whether it could ever actually be done, the laser cooling and magnetic evaporation techniques that Eric Cornell and Carl Wieman developed to reach temperatures just billionths of a degree above absolute zero, and what the condensate actually is — a macroscopic quantum object large enough to see, behaving according to rules that normally only apply at the scale of individual particles. It's the story of how science created something that does not exist anywhere in the universe without human intervention — a fifth state of matter conjured from extreme cold and quantum mechanics — and what it has already taught us about the deepest nature of reality.