A team of researchers has cooled matter down to a billionth of a degree from absolute zero, colder even than the deepest depths of space, far from any star.
Interstellar space never gets that cold due to the fact that it is uniformly filled with the cosmic microwave background (CMB), a form of radiation left over from an event that occurred shortly after the big Bang when the universe it was in his childhood. The cooled matter is even colder than the coldest known region of space, the Boomerang Nebulalocated at 3,000 Light years of the Earth, which has a temperature of just one degree above absolute zero.
The experiment, conducted at Kyoto University in Japan, used fermions, which is what particle physicists call any particle that makes up matter, including electrons, protons and neutrons. The team cooled their fermions, atoms of the element ytterbium, to about a billionth of a degree above absolute zero, the hypothetical temperature at which all atomic motion would cease.
“Unless an alien civilization is doing experiments like these right now, every time this experiment takes place at Kyoto University, it is producing the coldest fermions in the universe,” the University researcher said in a statement. of Rice, Kaden Hazzard, who participated in the study. statement (opens in a new tab).
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The team used lasers to cool matter by restricting the movement of 300,000 atoms within an optical lattice. The experiment simulates a model of quantum physics first proposed in 1963 by theoretical physicist John Hubbard. The so-called Hubbard model allows atoms to demonstrate unusual quantum properties, including collective behavior between electrons such as superconducting (the ability to conduct electricity without loss of energy).
“The reward of having this cold is that the physics really change,” Hazzard said. “Physics starts to become more quantum mechanical and allows you to see new phenomena.”
The ‘fossil’ radiation that keeps space warm
Interstellar space can never be that cold due to the presence of the CMB. This uniform, evenly distributed radiation was created by an event during the initial rapid expansion of the universe shortly after the Big Bang, the so-called last scattering.
During the last scattering, electrons began to bond with protons, forming the first atoms of hydrogen, the lightest element in existence. As a result of this formation of atoms, the universe rapidly lost its loose electrons. And because electrons scatter photons, the universe had been opaque to light before the last scattering. With the electrons bound to the protons in these early hydrogen atoms, photons could suddenly travel freely, making the universe transparent to light. The last scattering also marked the last time that fermions like protons and photons had the same temperature.
As a result of the last scattering, photons filled the universe at a specific temperature of 2.73 Kelvin, which is equivalent to minus 454.76 degrees Fahrenheit (minus 270.42 degrees Celsius), which is only 2.73 degrees above from absolute zero: 0 Kelvin or minus 459.67 degrees F (minus 273.15 degrees C).
There is a region in the known universe, the Boomerang Nebula, a cloud of gas that surrounds a dying Star in the constellation Centaurus, which is even cooler than the rest of the universe: about 1 Kelvin or minus 457.6 ⁰F (minus 272⁰ C). Astronomers believe that the Boomerang Nebula is being cooled by cold, expanding gas spewed out by the dying star at the nebula’s center. But even the Boomerang Nebula can’t compete with the temperatures of the ytterbium atom in the latest experiment.
The team behind this experiment is currently working on developing the first tools capable of measuring behavior that arises a billionth of a degree above absolute zero.
“These systems are quite exotic and special, but the hope is that by studying and understanding them, we can identify the key ingredients that must be present in the real materials,” Hazzard concluded.
The team’s research is published on September 9. 1 in physics of nature (opens in a new tab).
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