If you thought winters in Antarctica were cold or liquid nitrogen was fascinating for instantly freezing things, it might be time to think again. Scientists have created something so cold that it is difficult to even comprehend.
In 2022, scientists from Kyoto University in Japan and Rice University in Houston, Texas, cooled matter in a laboratory in Kyoto to within a billionth of a degree of absolute zero, the temperature when all motion stops and nothing can be colder. The temperature achieved was three billion times colder than the deepest, darkest recesses of interstellar space, making this matter the coldest in the universe.
The researchers in Kyoto started with fermions of the atoms of the volatile rare-earth metal ytterbium. Fermions are subatomic particles that include protons, neutrons, electrons, neutrinos, and quarks. They cooled the matter with lasers by restricting the motion of 300,000 atoms within an optical lattice. An optical lattice is composed of crystals made of light that are used to trap atoms at low temperatures.
Cooling atoms to such mind-boggling temperatures helps scientists understand the physics that occurs at such extreme temperatures and when the physics starts to become more quantum mechanical. These quantum mechanics would never be able to be seen under normal temperatures and conditions. Think of it like hitting pause on a movie to examine the scene. You can pick out and discover all sorts of things that would have flown right by at normal speeds.
This matter is the coldest in the universe because interstellar space never gets this cold. Interstellar space is filled with cosmic microwave background (CMB), which is radiation (and heat) that was left over shortly after the Big Bang took place during the initial rapid expansion of the universe. This allowed photons to be spread evenly throughout the universe. The temperature of these photons is 2.73 Kelvin or 2.73 degrees above absolute zero (-454.76 degrees Fahrenheit and -270.42 degrees Celsius), making all of space warmer than what was achieved in the Kyoto lab.
But one spot in the known universe is colder than the rest of the universe. It is the Boomerang Nebula in the constellation of Centaurus, about 5,000 light-years from Earth, and a cool 1 Kelvin (-457.6 degrees Fahrenheit or -272 degrees Celsius). It is believed this area is being cooled by cold gases ejected from a dying star at the center of the nebula.
More Facts About Really Cold Things
This isn’t the first time researchers have achieved incredibly cool things. In 2015, a team at the Massachusetts Institute of Technology (MIT) cooled individual molecules of sodium potassium gas to a temperature as low as 500 nano-Kelvin, which is only 500 billionths of a degree above absolute zero.
The scientists achieved this feat by using lasers to remove the heat from the individual gas molecules of the sodium-potassium gas. This was the first time in history that anything chemically bound had been made this cold. The result was a molecule that lasted only 2.5 seconds, but in the realm of physics, that was an extraordinary duration.
On the International Space Station, there is a lab called the Cold Atom Lab that has been used to research the quantum properties of atoms in microgravity. Experiments in the lab have reached 100 nano-Kelvin, or one ten-millionth of one Kelvin above absolute zero, which is colder than interstellar space.
In 2017, physicists offered a mathematical proof of the third law of thermodynamics, which declared that a temperature of absolute zero (0 Kelvin) cannot be physically achieved because it’s impossible for the disorder (entropy) of a system to reach zero. In simpler terms, it would take infinite steps and an infinite reservoir where heat could be deposited to reach absolute zero. The thing trying to be cooled would always be taking in heat from its surroundings because of the second law of thermodynamics.
When helium is cooled to a level of 4 Kelvin (-452.2 degrees Fahrenheit, -269 degrees Celsius), it takes on a liquid form, and when cooled further to 2.17 Kelvin (really cold), it behaves like a superfluid.
A superfluid is matter that behaves like a fluid with zero viscosity. In this strange form, liquid helium can appear to self-propel itself and defy the forces of gravity and surface tension. Liquid helium is used in superconducting magnets such as MRI machines, silicon wafer production, arc welding, and cryogenics.
The U.S. produces 75% of the world’s helium, and 30% of that is held in the U.S. Federal Helium Reserve near Amarillo, Texas. The panhandle of Texas is the prime helium production point in the U.S. and the world, and it comes about as a byproduct of natural gas production.
Liquid oxygen is also extremely cold, although not near the levels of liquid helium. Its freezing point is 54.36 Kelvin (-361.82 degrees Fahrenheit), and it causes anything it touches to become very brittle. It’s also a strong oxidizer, which means organic material will burn rapidly in liquid oxygen. Liquid oxygen is used extensively in the space program as a propellant and in the medical field.
Liquid nitrogen boils at 77 Kelvin (-195.79 degrees Fahrenheit). We’ve all probably seen liquid nitrogen in action (think of a banana in liquid nitrogen that is later smashed to pieces). The slow boiling of liquid nitrogen allows it to hold its very low temperature. Liquid nitrogen is used in many applications, such as refrigerant, cryotherapy for medical applications, fire prevention systems, and cryogenics.
To put all this in perspective, the coldest spot ever encountered on Earth occurred at Vostok Station in Antarctica on July 21, 1983. The temperature was -128.6 degrees Fahrenheit or -89.2 degrees Celsius (184 Kelvin). Other slightly colder temperatures have been remotely sensed by satellites over Antarctica, but these are believed to be below the ice.
Sources: Space, Popular Science, Live Science, MIT, Science Alert, Scientific America, Arizona State University, Ferrovial , Colorado State University
