Physicists in Germany have produced the coldest temperature ever recorded in a lab.
By dropping a gas down a 120-metre tower and switching a magnetic field on and off to bring its atoms to an almost complete standstill, the team managed to achieve a temperature 38 trillionths of a degree above absolute zero, or minus 273.15 degrees Celsius.
Absolute zero is the coldest temperature possible on the thermodynamic scale. At this point, there’s no atomic motion or heat at all. But it is not actually possible to reach that mark since kinetic energy from atoms cannot be removed completely.
This experiment is the closest that scientists have ever gotten to absolute zero.
They used a cloud of 1,00,000 atoms of rubidium (a silvery-white metallic element) trapped in a magnetic field in a vacuum chamber. The cloud was cooled down to form what is known as the Bose-Einstein Condensate, where the element begins to show strange quantum properties that are usually not observable.
Physicists then dropped the experiment over 120 metres, during which the magnetic field was switched off and on repeatedly.
When the magnetic field is off, the gas begins to expand, and when it’s turned back on, the gas is forced to contract again. This switching slows the expansion of the gas, bringing the atoms to an almost complete stop. Reducing this molecular speed effectively reduces the temperature.
While the experiment only managed to achieve this record-breaking temperature for up to two seconds, simulations showed that it should be possible to maintain it for up to 17 seconds in a weightless environment, such as aboard a satellite.