Scientists create coldest matter in the universe in a lab
科学家在实验室中研制出宇宙中最冷的物质
A team of researchers has cooled matter to within a billionth of a degree of absolute zero, colder than even the deepest depths of space , far away from any stars.
研究人员已经将物质冷却到绝对零度的十亿分之一以内，甚至比远离任何恒星的太空最深处温度还要低。
Interstellar space never gets this cold due to the fact that it is evenly 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 was in its infancy. The chilled matter is even colder than the coldest known region of space, the Boomerang Nebula, located 3,000 light-years from Earth, which has a temperature of just one degree above absolute zero.
星际空间从来不会如此寒冷，因为它均匀地充斥着背景辐射，这是宇宙大爆炸后不久宇宙处于萌芽状态时发生的事件遗留下来的辐射形式。这个冰冷的物质甚至比已知最冷的太空区域--回旋镖星云还要冷，回旋镖星云位于距离地球3000光年的地方，其温度仅高于绝对零度一度。
The experiment, run at the University of Kyoto in Japan and 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 around a billionth of a degree above absolute zero, the hypothetical temperature at which all atomic movement would cease.
这项实验在日本京都大学进行，使用了费米子，即粒子物理学家所说的任何组成物质的粒子，包括电子、质子和中子。研究小组将他们的费米子--镱元素的原子--冷却到绝对零度以上十亿分之一度左右，在绝对零度以上的假设温度下，所有原子的运动都将停止。
"Unless an alien civilization is doing experiments like these right now, anytime this experiment is running at Kyoto University it is making the coldest fermions in the universe," Rice University researcher Kaden Hazzard, who took part in the study, said in a statement (opens in new tab).
参与这项研究的莱斯大学研究员卡登·哈扎德在一份声明中说：“除非外星世界现在正在做这样的实验，否则不管京都大学何时进行这项实验，都在制造宇宙中最冷的费米子。”
Related: Did this newfound particle form the universe's dark matter?
相关：这个新发现的粒子形成宇宙的暗物质？
The team used lasers to cool the matter by restricting the motion 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 like superconduction ( the ability to conduct electricity without energy loss).
研究小组使用激光通过限制30万个原子在一个光晶格内的运动来冷却物质。该实验是理论物理学家约翰·哈伯德于1963年首次提出的量子物理模型的模拟。所谓的哈伯德模型允许原子展示不寻常的量子特性，包括电子之间的集体活动，如超导（在没有能量损失的情况下导电的能力）。
"The payoff of getting this cold is that the physics really changes," Hazzard said. "The physics starts to become more quantum mechanical, and it lets you see new phenomena."
“获得这个冷却物质的回报是物理真的发生了变化，”哈扎德说。“物理学开始变得更加趋向量子力学，让你看到新的现象。”
Interstellar space can never get this cold because of the presence of the CMB. This evenly spread and uniform radiation was created by an event during the initial rapid expansion of the universe shortly after the Big Bang, the so-called last scattering.
由于背景辐射的存在，星际空间永远都不会变得如此寒冷。这种均匀扩散和均匀辐射产生于大爆炸后不久宇宙最初快速膨胀时发生的一件事，即所谓最后一次散射。
During the last scattering, electrons started to bond with protons, forming the first atoms of the lightest existing element hydrogen. As a result of this atom formation, the universe rapidly lost its loose electrons. And because electrons scatter photons, the universe had been opaque to light before the last scattering. With electrons bound up with protons in these first hydrogen atoms, photons could suddenly travel freely, making the universe transparent to light. The last scattering also marked the last moment at which fermions like protons and photons had the same temperature.
在最后一次散射中，电子开始与质子结合，形成了现有最轻元素氢的第一个原子。由于这种原子的形成，宇宙迅速失去了它的松散电子。由于电子会散射光子，所以在最后一次散射之前，宇宙对光是不透明的。当电子与第一批氢原子中的质子结合时，光子突然可以自由传播，使宇宙对光透明。最后一次散射也标志着像质子和光子这样的费米子最后一次具有相同温度。
As a result of the last scattering, photons filled the universe at a specific temperature of 2.73 Kelvin, which equals minus 454.76 degrees Fahrenheit (minus 270.42 degrees Celsius) which is just 2.73 degrees above absolute zero — 0 Kelvin or minus 459.67 degrees F (minus 273.15 degrees C).
最后一次散射的结果是，光子在2.73开尔文的特定温度下充斥着宇宙，相当于零下454.76华氏度（零下270.42摄氏度），比绝对零度-0开尔文或零下459.67华氏度（零下273.15摄氏度）高出2.73度。
There is one region in the known universe, the Boomerang Nebula, a cloud of gas that surrounds a dying star in the constellation of Centaurus, which is even colder than the rest of the universe — around 1 Kelvin or minus 457.6 ⁰F (minus 272⁰ C). Astronomers believe the Boomerang Nebula is being cooled by cold, expanding gas spat 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.
在已知的宇宙中有一个区域，即回旋镖星云，它是围绕半人马座中一颗垂死恒星的气体云，比宇宙其他地方还要冷--大约1开尔文或零下457.6华氏度（零下272摄氏度）。天文学家认为回飞棒星云正被星云中心垂死的恒星喷出的膨胀气体冷却。但在最新的实验中，即使是回旋镖星云也无法与镱原子的温度竞争。
The team behind this experiment is currently working on developing the first tools capable of measuring the behavior that arises a billionth of a degree above absolute zero.
这个实验团队目前正在研发第一个能够测量绝对零度以上十亿分之一度的活动的工具。
"These systems are pretty exotic and special, but the hope is that by studying and understanding them, we can identify the key ingredients that need to be there in real materials," Hazzard concluded.
哈扎德总结说：“这些系统非常奇特和特殊，但希望通过研究和理解它们，我们可以确定真正材料中必须存在的关键成分。”
The team's research is published on Sept. 1 in Nature Physics (opens in new tab).
该小组的研究发表在9月1日的《自然物理学》（在新标签中打开）上。
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