Scientists Create ‘Coldest Temperature Ever’ by Dropping Experiment From a Building

As far as we can tell from modern science, there’s no upper limit to temperature. There sure is a lower limit, though. We call that absolute zero, measured as -273.15 °C (-459.67 °F). Scientists have yet to reach that limit in any experiment, but they’re getting close. A team of physicists in Germany has gotten closer than ever before, reaching a temperature of 38 trillionths of a degree from absolute zero, according to New Atlas.

This news might sound familiar because it is — scientists have inched closer to absolute zero on numerous occasions. A few years ago, MIT created what was at the time the coldest spot in the universe with sodium and potassium atoms. The International Space Station has also conducted experiments within a fraction of a degree of absolute zero. The problem is that no matter how well insulated your testing setup is, a tiny amount of energy always sneaks in from the environment. When that happens, you can’t reach absolute zero and halt all atomic motion.

The team from the University of Bremen broke the record once again by dropping the experiment (above) from the top of a very tall tower. Yes, really. They started with a cloud of 100,000 rubidium atoms, which were confined inside a magnetic field. When cooled, the atoms clump together and form a mysterious state of matter known as a Bose-Einstein condensate. In this state, the atoms act like one giant atom, making quantum effects visible at the macroscopic scale.

That process is common in research of this nature, allowing scientists to create extremely cold conditions about two billionths of a degree above absolute zero. To break the record, the team ran the experiment at the Bremen Drop Tower research facility. They dropped their Bose-Einstein condensate from the top of the 120-meter tower, flipping the magnetic field off and on as it fell. When the field is off, the atoms start to expand, but then they snap back when it’s switched on. The team found that atomic motion almost completely stopped during free fall as a result of the magnetic field toggling. That’s how they reached the lowest temperature ever, a mere 38 picoKelvin.

So, the University of Bremen was home to the coldest known spot in the universe during this test but not for very long. Because the experiment required free fall to completely isolate the sample, it only lasted for two seconds. However, simulations show that it’s theoretically possible to maintain this temperature for about 17 seconds with current technology. Something like that may be possible on the ISS.