Particle physicists working at an underground laboratory underneath Italy’s Gran Sasso mountain cooled an 880-pound mass of copper to -273.144°C/—459.659°F, a mere .006°C away from absolute zero (0°K/-275.15°C/-459.67°F). For about two weeks, it was the coldest object in the observable universe—and by that I mean the coldest object ever found in the observable universe, anywhere, at any time. As io9’s George Dvosky explains:
The feat happened at the Cryogenic Underground Observatory for Rare Events (CUORE), a particle physics lab in Italy where an international group of scientists are working, including those from the U.S., China, Spain, and France. The copper was encased in a cryostat container, which according to the researchers is "the only one of its kind in the world, not only in terms of its dimensions, extreme temperatures and cooling power, but also for the selective materials and for the building techniques that both guarantee very low levels of radioactivity."
There are several caveats that come along with this, of course, the biggest being that we haven’t really observed very much of the universe as a whole and aren’t in a position to speak with any authority about what the coldest parts of it might be. But when we look at the parts of it we’ve actually observed, the very coldest could briefly be found under a mountain in central Italy, surrounded by more than four tons of low-radioactivity ancient Roman lead.
And CUORE didn’t just superfreeze copper to get bragging rights; it’s a particle physics laboratory, and these extremely low temperatures allow scientists to slow down matter and energy to an extent nature doesn’t allow so we can get a good look at it. Actual absolute zero is out of the question, but we can get so close to absolute zero that really freaky stuff starts to happen to the subatomic particles they’re studying—potentially giving us insight into the behavior of neutrinos, among other things.