DgcityIn a laboratory module orbiting 400 kilometers above the Earth, Chinese physicists have made one of the coldest places in the universe. A team working aboard the Tiangong space station cooled a cloud of rubidium atoms to 9.7 picokelvin, the lowest temperature humanity has ever achieved and held for observation.
A picokelvin is one trillionth of a degree above absolute zero, the theoretical point at which all thermal motion ceases. At 9.7 picokelvin, the atoms drift with a slowness almost impossible to imagine. The team managed to keep the ultra-cold cloud stable and observable for seven seconds, an eternity in a field where samples often vanish in the blink of an eye.
Doing the experiment in space is what made the record possible. On Earth, gravity tugs constantly at cooled atoms, pulling them downward and out of the trap holding them before physicists can study them carefully. In orbit, the atoms float weightlessly inside a vacuum chamber, suspended by lasers and magnetic fields, giving researchers the long, quiet observation window they need.
At such temperatures, ordinary rules of motion blur into quantum behavior. The atoms can form a Bose-Einstein condensate, an exotic state of matter in which individual particles lose their separate identities and move as a single coherent whole. Studying these condensates lets physicists probe the boundary between quantum weirdness and classical physics, and may one day feed into ultra-precise sensors for gravity, rotation and timekeeping.
The experiment was carried by the Mengtian module, Tiangong’s primary cabinet for fluid physics, combustion science and ultra-cold atomic research. The apparatus, called the Cold Atom Experiment Rack, was built so that scientists on the ground could run cooling sequences and collect data without astronauts handling the hardware directly.
The result places China among the leaders in a small field. NASA’s Cold Atom Lab has operated on the International Space Station for years, and German and French teams have run their own ground and sounding-rocket experiments. Tiangong’s new figure sets a fresh benchmark, while also underlining how space stations have become tools for fundamental physics rather than merely destinations for human spaceflight.
Future runs will push for even lower temperatures and longer observation. In that near-motionless cloud, researchers hope to catch glimpses of phenomena that could rewrite details of the standard models of physics.
