German physicists have cooled atoms to the lowest temperature in the history of scientific observation: they conducted an experiment with the quantum free fall of gas.
Physicists from Germany recorded the coldest temperature ever recorded. It is 38 trillion degrees above absolute zero. During the experiment, physicists dropped the quantum gas and turned on and off the magnetic field in order to bring its atoms to an almost complete stop.
Absolute zero is -273.15 ° C, the lowest temperature on the thermodynamic scale. This is the point at which there is no atomic motion or heat at all. It was believed that scientists will never be able to reach this mark, since it is impossible to remove all kinetic energy from the atoms in the system.
But the authors of the new work in the study recorded a temperature of 38 picokelvin or 38 trillion degrees above absolute zero.
To achieve this, the authors started with a cloud of 100,000 rubidium atoms that was captured by a magnetic field in a vacuum chamber. They then cooled it to form a quantum gas called Bose-Einstein Condensate (BEC). In it, the atoms start to act like one big atom.
But the temperature was not cold enough, so the team conducted an experiment in which they dropped a Bose-Einstein condensate trap 120 m. During free fall, the team turned on and off the magnetic field containing the gas several times.
When the magnetic field is turned off, the gas begins to expand, and when it is turned on again, the gas is forced to contract again. This switching slows the expansion of the gas almost to a complete stop, and a decrease in molecular velocity lowers the temperature.
As a result, the authors managed to reach record temperatures in just two seconds. Simulations have shown that it can be maintained for up to 17 seconds in zero gravity, for example, on board a satellite.