Physicists aboard China's Tiangong orbital station have achieved a record-low temperature for a cloud of rubidium atoms — 9.7 picokelvin, the website infohub.kz reports.
The results of the experiment have been published in the journal Science. In the station's laboratory module, researchers captured about 20,000 rubidium atoms in laser traps and brought them to a Bose-Einstein condensate state. In this form of matter, the cooled particles essentially stop moving and begin to behave in sync, like a single giant quantum object.
The temperature achieved was just 9.7 trillionths of a degree above absolute zero — the theoretical limit of cold in the Universe.
On Earth, such experiments are complicated by gravity: when the laser traps are weakened to cool the matter further, heavy atoms rapidly fall downward and collide with the walls of the chamber. In weightlessness in orbit, scientists were able to observe the free expansion of the ultracold cloud for seven seconds. By comparison, on the planet's surface a similar drop of particles would require a vacuum tower about 250 meters tall.
The new result surpassed previous records for cooling matter — 38 picokelvin, obtained in a ground-based drop tower in Germany, and 52 picokelvin, recorded on the International Space Station. Such research makes it possible to measure quantum effects more precisely, model the properties of complex materials and test fundamental laws of physics.