Scientists Create the Littlest Big Bang to Study the Universe’s Origins

科学家制造出“微型大爆炸”以研究宇宙起源

In the very first moments of the universe, matter didn’t exist as we know today. A millionth of a second or so after the big bang, the universe was a dense, hot soup scientists call quark-gluon plasma (QGP). For several years, particle colliders—which smash molecules together at nearly the speed of light—have been able to replicate this state, but often using heavy elements like lead. 在宇宙最初的时刻，物质并不像我们今天所知的那样存在。在大爆炸发生后约百万分之一秒，宇宙处于一种科学家称之为“夸克-胶子等离子体”（QGP）的致密热汤状态。多年来，粒子对撞机——通过将分子以接近光速的速度撞击在一起——已经能够复制这种状态，但通常使用的是铅等重元素。

Now, a recent experiment by the European Organization for Nuclear Research (also known as CERN from its French acronym) has demonstrated this plasma can be produced by much smaller collisions. Since there’s no longer an accessible natural source of this primordial sludge, these micro big bangs can help reveal what happened in the first few minutes of our universe. 现在，欧洲核子研究中心（CERN）最近的一项实验表明，这种等离子体可以通过规模小得多的碰撞产生。由于目前已没有可获取的原始物质自然来源，这些“微型大爆炸”有助于揭示宇宙最初几分钟内发生的事情。

First, a little context. Quarks are what make up protons and neutrons, which, in turn, are the building blocks of atoms and thus all matter. Meanwhile, gluons—as their name suggests—stick quarks together. 首先，介绍一些背景知识。夸克是构成质子和中子的基本粒子，而质子和中子又是原子的基石，进而构成了所有物质。与此同时，正如其名，胶子负责将夸克“粘”在一起。

During the first microseconds of the universe, quarks and gluons were not yet confined within protons and neutrons but instead formed an extremely hot plasma. As the universe expanded, the matter cooled, and the quarks condensed into larger particles. 在宇宙最初的几微秒内，夸克和胶子尚未被束缚在质子和中子内部，而是形成了一种极热的等离子体。随着宇宙膨胀，物质冷却，夸克凝结成了更大的粒子。

After decades of studying QGP in large nuclear collisions, physicists are now trying to understand the limits of this strange state of matter. In particular, they are exploring just how much they can scale down a collision and still observe a collection of particles that behaves like a drop of fluid. 在对大型核碰撞中的夸克-胶子等离子体进行了数十年的研究后，物理学家们现在正试图了解这种奇异物质状态的极限。特别是，他们正在探索碰撞规模可以缩小到什么程度，同时仍能观察到表现得像液滴一样的粒子集合。

According to a recent article in Physical Review Letters, CERN and an international team of collaborators were able to generate the substance using oxygen-16 and neon-20. Both are less than a tenth of the weight of a lead atom, which was previously considered one of the lightest elements capable of generating QGP. 根据《物理评论快报》最近的一篇文章，欧洲核子研究中心和一个国际合作团队利用氧-16和氖-20成功产生了这种物质。这两种元素的重量都不到铅原子的十分之一，而铅此前被认为是能够产生夸克-胶子等离子体的最轻元素之一。

“We have pushed the boundary for how small the atomic nuclei can be while still re-creating this primordial matter—what you could call a ‘little big bang.’ We now know more about the fundamental conditions required for matter to transition into this extreme state,” You Zhou, a researcher at the Niels Bohr Institute in the Netherlands and a coauthor of the study, explained in a press release. “我们突破了原子核在重现这种原始物质时所能达到的最小尺寸界限——你可以称之为‘微型大爆炸’。我们现在对物质转化为这种极端状态所需的基本条件有了更多了解，”荷兰尼尔斯·玻尔研究所的研究员、该研究的合著者周游（You Zhou）在新闻发布会上解释道。

The scientists found that, despite the small size of the oxygen and neon nuclei, the collisions produced signals consistent with the behavior they expected to find in QGP. For an instant, the generated matter appeared to expand collectively like a fluid before cooling and reverting to particles. 科学家们发现，尽管氧核和氖核的尺寸很小，但碰撞产生的信号与他们预期在夸克-胶子等离子体中发现的行为一致。在瞬间，生成的物质似乎像流体一样集体膨胀，随后冷却并还原为粒子。

“Hopefully, this will help us better understand how the plasma behaved during the first moments of the universe—and how it later evolved into the forms of matter that everything around us is made of,” Zhou added. “希望这能帮助我们更好地理解等离子体在宇宙最初时刻的表现，以及它后来是如何演变成构成我们周围一切事物的物质形态的，”周游补充道。