In the 1990s, many research groups pushed small samples of gas to lower and lower temperatures with laser cooling and trapping. Then magnetic fields confine the cold gas while the most energetic atoms are allowed to evaporate away, cooling the sample further—just like the way that water evaporating on the skin cools the body. The image shows the velocities of trapped atoms as they enter the BEC state. The sharper the peak, the greater the number of atoms in the BEC.

This graphic shows how a system of ultracold atoms approaches the Bose-Einstein Condensate. As the peak becomes taller and more sharply defined, more and more atoms have “condensed” into the same state. (graphic courtesy of NIST)

Magneto-0ptic Trap at MIT (photo courtesy of the MIT BEC group)

In making the first BEC in 1995, a team led by Carl Wieman, of the University of Colorado at Boulder, and Eric Cornell, of the National Institute of Standards and Technology, trapped about 2,000 rubidium atoms in a space about 20 microns in diameter (20 x 10^-6 m, or about one-tenth the thickness of a human hair). A few months later, a team led by Wolfgang Ketterle at MIT achieved a BEC with half a million sodium atoms. These three physicists shared the Nobel Prize in Physics 2001.