Bose–Einstein condensates are trapped atoms that are cooled to low temperatures and occupy the same quantum state. They are ideal for studying and manipulating quantum effects such as solitons and vortices as they occur on the macroscopic rather than the microscopic scale. In both of the new experiments the soliton waves moved through the BECs at velocities less than the speed of sound, confirming that the effect was not sound waves. Indeed as soon as the solitons reached the speed of sound, they disappeared. "The ability to imprint phase profiles onto a condensate and the resolve the profile using a separate technique is a lovely advance," says Keith Burnett an atomic physicist from Oxford University.