Physicists at the University of Bremen, Germany produced the coldest temperature ever recorded, an incredibly precisely measured 38 trillionths of a degree above absolute zero. They did so as part of an experiment involving dropping a quantum gas and slowing its motion with magnets, a report from New Atlas explains.
Absolute zero is measured as -459.67 °F (-273.15 °C) and it is the coldest possible temperature on the thermodynamics scale. For an object to reach that temperature, there would have to be zero atomic motion or kinetic energy in its atoms, meaning it is impossible for scientists to ever truly reach absolute zero. However, experiments such as those conducted aboard the International Space Station's Cold Atom Lab have been as cold as 100 nanoKelvin, or 100 millionths of a degree above absolute zero.
The lowest temperature ever recorded
The team from the University of Bremen have smashed previous records, however, by recording a temperature of 38 picoKelvin, or 38 trillionths of a degree above absolute zero, during their experiments. In a press release, the team explained that "while researching the wave properties of atoms, one of the "coldest places in the universe" [was] created for a few seconds at the Center for Applied Space Technology and Microgravity (ZARM) at the University of Bremen."
For their experiments, the team trapped a gas cloud composed of 100,000 rubidium atoms in a magnetic field in a vacuum chamber. This was then cooled down to turn it into a quantum gas called a Bose-Einstein Condensate (BEC). As quantum gases act uniformly, as if they were one big atom, scientists use them in experiments to observe unusual quantum effects on the macro scale, with a view to expanding their knowledge of quantum mechanics.
Future space experiments may be written in the stars
In order to reach the required temperature, the researchers dropped the BEC at the Bremen Drop Tower research facility. While they dropped the gas 393.7 feet (120 meters) down the tower, they also switched the magnetic field containing the gas on and off several times. When the magnetic field is turned off the gas starts to expand and when it is turned back on its contracts. The switching slows the expansion of the gas to an almost complete standstill, greatly lowering its temperature due to the reduced molecular speed.
The researchers were only able to sustain the record-breaking temperature for 2 seconds, though they carried out simulations suggesting it could be maintained for approximately 17 seconds in a weightless environment such as the International Space Station. In space, scientists can confine atoms using much weaker forces, as they don't have to be supported against the effects of gravity. This means that further investigation may eventually take place in the ISS's Cold Atom Lab (CAL), where astronomers last year reported the creation of a "fifth state of matter" during BEC experiments. The CAL was transported to space by a SpaceX rocket in 2018 and it has since been used to observe quantum phenomena that would be undetectable on Earth.