A team of researchers has cooled matter to within a billionth of absolute zero, colder than even the deepest parts of space, far from any stars.
Interstellar space has never been so cold because it fills evenly cosmic microwave background (CMB), a form of radiation that was left over from an event that occurred shortly after the event. big Bang when. . .when universe Still in its infancy.The icy material is colder than even the coldest known region of space Boomerang Nebulaat 3,000 light years From Earth, its temperature is only one degree above absolute zero.
The experiment, conducted at Kyoto University in Japan, uses fermions, which 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 a billionth of a degree above absolute zero, the hypothetical temperature at which all atomic motion would cease.
Kaden Hazzard, a Rice researcher involved in the study, said: “Unless an alien civilization is doing such an experiment right now, just doing this experiment at Kyoto University would make the most Cold fermions.” statement (opens in new tab).
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The team used a laser to cool matter by confining the motion of 300,000 atoms within an optical lattice.The experiment simulates a model quantum physics First proposed in 1963 by theoretical physicist John Hubbard.The so-called Hubbard model allows atoms to exhibit unusual quantum properties, including collective behavior between electronic Like superconductivity (the ability to conduct electricity without energy loss).
“The great thing about a cold is that the physics really change,” Hazzard said. “Physics is starting to become more quantum mechanical, and it lets you see new phenomena.”
The ‘fossil’ radiation that keeps space warm
Interstellar space has never been so cold because of the CMB. This uniformly distributed and uniform radiation was produced 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 begin to combine with protons to form the first atoms of the lightest existing element, hydrogen. Due to the formation of such atoms, the universe quickly lost its loose electrons. And because electrons scatter photons, the universe is opaque to light until the last scattering. As electrons combine with protons in these first hydrogen atoms, photons can suddenly travel freely, making the universe transparent to light. The last scattering also marks the last moment when fermions like protons and photons have the same temperature.
Due to the last scattering, photons filled the universe at a specific temperature of 2.73 Kelvin, which is equal to minus 454.76 degrees Fahrenheit (minus 270.42 degrees Celsius), just 2.73 degrees above absolute zero — 0 Kelvin or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius).
There is one region in the known universe, the Boomerang Nebula, a cloud of gas surrounding a dying Star In Centaurus, it’s colder 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 ejected from the dying star at the center of the nebula. But even the Boomerang Nebula can’t match the atomic temperature of ytterbium in the latest experiment.
The team behind the experiment is currently developing the first tool capable of measuring behavior that occurs at one-billionth of a degree above absolute zero.
“These systems are very exotic and idiosyncratic, but hopefully by studying and understanding them, we can identify key ingredients that need to be present in real materials,” Hazzard concluded.
The team’s research was published Sept. 1 in physical physics (opens in new tab).
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