Bubbling up(浮出水面)
关键词：
气候,Climate
Climate change
气候变化
Oct 26th 2006
From The Economist print edition
A new experiment to test the role of cosmic rays in global warming
一项新试验旨在检测宇宙射线对全球变暖的作用
SIR WILLIAM HERSCHEL, an 18th-century astronomer, is credited with being the first person to notice the effect of variations in the sun's activity on the Earth. In 1801 he observed that when the sun had many spots on its surface, the price of wheat fell—a connection he attributed to the weather being more temperate. Over the next 200 years scientists tried, without much success, to understand exactly how these transient sunspots might affect the climate. Now an experiment has begun that could explain what is going on.
18世纪的天文学家——威廉·赫歇尔爵士（William Herschel）[1]被誉为观测到太阳活动变化对地球影响的第一人。1801年他通过观测发现：每当太阳表面有许多黑斑，即太阳黑子（sun-spot）时，小麦的价格就要往下走——他将这种联系归到此时的气候更为温和这个因素上。此后的200多年间，科学家们试图确切掌握这些稍纵即逝的太阳黑子究竟怎样影响地球的气候，但是收效甚微。现在一项试验已经启动，它可以告诉我们究竟发生了什么。
The Earth is continually bombarded by streams of particles that come from outside the solar system. These cosmic rays, as they are called, consist mostly of protons. They strike the gases of the Earth's atmosphere at great speeds, creating showers of debris including streams of electron-like particles called muons. An international team of physicists led by Jasper Kirkby, who works at CERN, the European particle physics laboratory near Geneva, has devised an experiment to find out how this process might affect the climate.
地球始终受到来自太阳系外各种粒子流的攻击。这些宇宙射线（粒子流的名称）的主要成分是质子。它们以惊人的速度撞击地球大气层中的气体，并产生各类残存的粒子雨，其中包括一种类似电子、被成为μ子（muon）的微粒。一个国际性的物理学研究小组已经设计了一个实验，其目的就是为了找出这一撞击过程如何影响气候的答案。该研究小组由供职于欧洲核子研究中心（CERN）[2]，即欧洲粒子物理实验室（位于瑞士日内瓦附近）的贾斯珀·柯克比（Jasper Kirkby）领导。
When scientists first turned their attention to subatomic particles, including cosmic rays, they used a device called a cloud chamber to study them. These are boxes containing air that is super-saturated with water vapour. When a charged particle zips through the chamber, the vapour condenses into a trail of droplets showing the particle's path and, if the box is placed in a magnetic field, its electrical charge.
当科学家们首次把研究的焦点放到亚原子粒子（包括宇宙射线）[3]上时，他们使用一种称作“云室”的装置进行观察。这是一些装有水汽过饱和空气的容器。当一个带电粒子快速穿越云室时，水汽会凝结形成一串小液滴，这样便标识出了该粒子的路径；若将容器置于一个磁场中，还能知道粒子所带电荷的性质。
In an updated version of a cloud chamber the researchers are recreating the Earth's atmosphere. They fill the container with pure air made by evaporating liquid nitrogen and liquid oxygen, and add water vapour and some trace gases. They adjust the temperature and pressure of the mix to mimic conditions at various heights above sea level. Then they zap the results with a stream of particles from the laboratory's elderly proton synchrotron. Ideally, they would use muons but, in practice, they are using a close cousin, the pion.
在一个改进后的云室里，研究人员们正在重塑地球的大气层。他们往云室里填充了由液态氮和液态氧经气化后制成的纯净空气，并添加了水汽和一些痕量气体。为了模拟各种海拔条件，他们还调整了温度以及混合气体的压强。等一起就绪，他们便用实验室里的老式质子加速器产生某种粒子流，轰击云室中的大气层。μ子是粒子流的理想候选，但实际上他们用π子——μ子的“同胞兄弟”——做试验。
The theory is that when a muon encounters a gas molecule, it can knock off an electron, leaving a positively charged ion in its wake. The electron soon attaches itself to another molecule, making a negatively charged ion. These ions are thought to help create new particles called aerosols and, when aerosols grow above a certain size, they become the seeds around which cloud droplets form.
有理论认为：当一个μ子遇到一个气体分子时，它会电离出一个电子，剩下的部分则形成一个正离子。这个电子会立即同其他气体分子耦合并形成一个负离子。人们认为这些离子有助于产生被称作气溶胶的各种新微粒，而且当气溶胶的体积增大到一定规模，它便成了云滴形成的“温床”。
The experiment is testing this theory. If it is correct, then cosmic rays may create clouds with more small droplets than would otherwise be the case. Such clouds would persist for an unusually long time because small water droplets are less likely than big ones to turn into rain. Physicists also think that such clouds would be brighter and more reflective than normal clouds. So they would cool the Earth by hanging around and by reflecting more heat from the sun back into space.
此项试验正是在验证这个理论。如果该理论正确，那么宇宙射线形成的云同其他方式形成的云相比，小云滴的数量更多。这类由较多小云滴组成的云所能维持的时间之久异乎寻常，因为大云滴比小云滴更容易转变为雨滴。物理学家们也认为这类云层比起普通云层更明亮、反射性更强。因此，他们打算把来自太阳的热量更多地阻隔或反射回太空，借此给地球降温。
The link between the sun's activity and climate involves another lot of particles streaming past the Earth. The planet and its neighbours are bathed in the solar wind, a stream of charged particles ejected from the upper atmosphere of the sun. The magnetic field associated with these particles helps protect the Earth from cosmic rays by deflecting them from the planet.
太阳活动同气候之间的关联还牵涉另一类穿越地球的粒子流。地球及其邻居都受到太阳风——一股从太阳最外层的大气（日冕）喷射出来的带电粒子流——的侵袭。地磁场同这些粒子相结合令宇宙射线发生弯曲，从而帮助地球避开来访的宇宙射线。
When the sun is at its most active, which is when it is spotty, the solar wind is stronger and fewer cosmic rays penetrate. Conversely, when solar activity is less intense, more cosmic rays get through. A study using data on cloud cover taken from satellite images dating from 1979 found that 65% of the world's skies were covered by cloud when cosmic rays were weakest and 68% when they were strongest.
当太阳活动进入最活跃的时期，太阳黑子数最多，太阳风也更强，从而穿透大气层闯入地球的宇宙射线也越少；反之，太阳活动的强度较低，更多的宇宙射线可以穿透大气层。一项研究发现，当宇宙射线最弱和最强时，地球上空为云层所覆盖的区域比例分别是65%和68%。此项研究所需的云层数据由1979年以来的卫星航片所提供。
Scientists modelling climate change have ignored cosmic rays up to now because there was not enough evidence about how they might work. However, the results of this experiment, expected by summer 2007, could show how nature periodically sticks her oar in. The experiment on cloud formation also seems likely to undermine the particle physics laboratory's reputation for pursuing only blue skies research.
迄今为止，从事气候变化建模的科学家们都忽略了宇宙射线的作用，因为还未有足够的证据说明宇宙射线如何起作用。但是，本次试验的结果（试验结果预计到2007年夏得出）可以告诉我们自然界如何对此进行周期性地操控；同时，此项云层形成的试验可能有损欧洲粒子物理实验室的声誉，因为该实验室素来以纯理论研究而著称。
注释：
[1] 威廉·赫歇尔，英国天文学家，恒星天文学的创始人，被誉为恒星天文学之父。他于1781年发现了天王星，1816年，英国国王乔治三世册封他为爵士。
[2] CERN是欧洲核子研究机构（European Organization for Nuclear Research），即西欧中心的代称，而CERN四个字母的最初由来则是出自其法语名称的缩写（Conseil Européen pour la Recherche Nucléaire）；到了当代，CERN已经被更广泛的解释为欧洲粒子物理研究所或实验室（European Laboratory for Particle Physics），即本文提及的欧洲粒子物理实验室。
[3] 亚原子粒子也叫基本粒子（elementary particle）：泛指比原子核为小的物质单元。包括电子、中子、质子、光子以及在宇宙射线和高能原子核实验中发现的一系列粒子。翻译 by edenbahamut