Reaching absolute zero is physically impossible.

The team at the University of Cambridge, however, monitors energy on a more extreme level as they try to approach absolute zero—the coldest temperature allowed by the laws of thermodynamics. Absolute zero, technically known as zero kelvins, equals −273.15 degrees Celsius, or -459.67 Fahrenheit, and marks the spot on the thermometer where a system reaches its lowest possible energy, or thermal motion. There’s a catch, though: absolute zero is impossible to reach. The reason has to do with the amount of work necessary to remove heat from a substance, which increases substantially the colder you try to go. To reach zero kelvins, you would require an infinite amount of work. And even if you could get there, quantum mechanics dictates that the atoms and molecules would still have some irreducible motion. Quantum mechanics also means that the closer these researchers creep toward absolute zero, the weirder a substance’s properties become. At low enough temperatures, liquid helium, for example, morphs into a superfluid—a liquid that flows without the resistance of friction. As a result, it can spontaneously flow upwards and out of a container; seep through molecule-thin cracks; remain perfectly still while spinning at high speeds; and—most surprising to physicists—coalesce into one “super-atom,” known as a Bose-Einstein condensate. Working at around just 1 to 10 millikelvins, or thousandths of a kelvin, the Cavendish team is in the process of surveying a variety of other materials that also show funky quantum behavior. And the technology that the group uses to reach such frigid temperatures is almost as complicated as the behavior it’s trying to induce.