A new way of controlling the expansion of matter in a freely-falling Bose-Einstein condensate (BEC)has produced the coldest effective temperature ever measured: 38 pK (10 K) above absolute zero. The method, which allowed researchers in Germany and France to image the condensate’s evolution for more than two seconds, opens the door to enhanced measurements of the gravitational constant g and photon recoil, and could even offer an alternative means of detecting gravitational waves.
