Scientists have broken the record for the coldest temperature ever measured in a lab. They achieved the bone-chilling temperature of 38 trillionths of a degree above absolute zero, -273.15 Celsius, by dropping magnetized gas 120 meters down a tower.
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The team of German researchers was investigating the quantum properties of a so-called fifth state of matter: Bose-Einstein condensate (BEC), a derivative of gas that exists only under ultra-cold conditions. While in the BEC phase, matter itself begins to behave like one large atom, making it an especially appealing subject for quantum physicists who are interested in the mechanics of subatomic particles.
In scientific terms, temperature is a measure of molecular vibration. In other words, the more a collection of molecules moves, the higher the collective temperature. Absolute zero, then, is the point at which all molecular motion stops — minus 459.67 degrees Fahrenheit, or minus 273.15 degrees Celsius. When we get down to these temperatures, we use the Kelvin scale, with absolute zero being measured as 0 degrees Kelvin and it follows the same scale as Celsius.
In this record-breaking experiment, scientists trapped a cloud of around 100,000 gaseous rubidium atoms in a magnetic field inside a vacuum chamber. Then, they cooled the chamber way down, to around 2 billionths of a degree Celsius above absolute zero.
But this wasn’t quite frigid enough for the researchers, who wanted to push the limits of physics; to get even colder, they needed to mimic deep-space conditions. So, the team took their setup to the European Space Agency’s Bremen drop tower, a microgravity research centre at the University of Bremen in Germany. By dropping the vacuum chamber into a free fall while switching the magnetic field on and off rapidly, allowing the BEC to float uninhibited by gravity, they slowed the rubidium atoms’ molecular motion to almost nothing. The resulting BEC stayed at 38 picokelvins – 38 trillionths of a Kelvin – for about 2 seconds, setting “an absolute minus record”.
