How cosmic rays help us understand the universe - Veronica Bindi

宇宙线如何帮助我们了解宇宙 - Veronica Bindi

翻译人员: Xinyi Zhang 校对人员: Tianyu Wang

How much can we really know about the universe beyond our galaxy?

我们对银河之外的宇宙了解多少？

The Hubble Telescope has enabled us to see

哈勃望远镜使我们能够看到远至宇宙空间中13000000000光年的东西。

objects in space as far 13,000,000,000 light years away.

But this still doesn't give us the answers to all our questions,

但这仍然不足以给出我们的问题的全部答案，

questions like, "What is the universe made of?"

像这样的问题，“宇宙是由什么组成的？”

"Which elements are the most abundant?"

"宇宙中含量最丰富的元素是什么？"

"Does space contain undiscovered forms of matter?"

“空间是否包含着尚未被发现的物质形态？”

"Could there be antimatter stars or galaxies?"

“是否有反物质星或星系存在？”

Some of these questions cannot be answered solely from visual images,

仅仅通过视觉图像（指哈勃望远镜）来回答其中一些问题是不够的，

but what if we had messengers bringing us physical data

但是如果我们有一些信使能带给我们遥远宇宙空间的信息，

from distant parts of the cosmos,

beyond the reach of explorers or satellites?

甚至超越了探月器和卫星可以到达的尺度？

In a way, we do, and these "space messengers" are called cosmic rays.

在某种程度上，我们有这种“空间信使”，即宇宙线。

Cosmic rays were first discovered in 1912 by Victor Hess

宇宙线在1912年由维克特 赫斯 首先发现，

when he set out to explore variations in the atmosphere's level of radiation,

当时他着手研究大气中辐射的变化

which had been thought to emanate from the Earth's crust.

这种辐射被认为是源自地壳。

By taking measurements on board a flying balloon during an eclipse,

通过在日食期间在热气球上的进行的测量，

Hess demonstrated both that the radiation actually increased

赫斯展示了辐射随着海拔的增高而增高，从而排除了太阳作为辐射源的情形。

at greater altitudes and that the sun could not be its source.

The startling conclusion was that it wasn't coming from anywhere

令人吃惊的结论是辐射并不来自地球大气层以内的任何地方而是来自太空。

within the Earth's atmosphere but from outer space.

Our universe is composed of many astronomical objects.

我们的宇宙由很多天体组成，

BIllions of stars of all sizes, black holes, active galactic nuclei,

数以亿计、各种大小的恒星、黑洞、活动星系核、卫星、行星，等等。

astroids, planets and more.

During violent disturbances, such as a large star exploding into a supernova,

在剧烈的扰动，比如一个大恒星演化至爆炸成一个超新星时，

billions of particles are emitted into space.

数以亿计的粒子辐射到宇宙空间。

Although they are called rays,

尽管也被叫做“线”（rays），

cosmic rays consist of these high energy particles

宇宙线是由一些高能粒子组成，

rather than the photons that make up light rays.

而不是像光线由光子组成。

While the light from an explosion travels in a straight line

当爆炸产生的光子沿直线以它著名的速度（光速）传播，

at its famous constant speed,

the particles are trapped in extraordinary loops

宇宙线中的高能粒子却被束缚在

by magnetic shockwaves generated by the explosion.

一些由爆炸产生的冲击波形成的圈中。

Crossing back and forth through these magnetic field lines

反反复复在这些磁力线之间穿梭，

accelerates them to almost the speed of light before they escape.

这些粒子被加速，到逃离这些圈时速度已经接近光速。

There are lots of cosmic rays in space, and some of these particles have traveled

大气中有很多的宇宙线，

for billions of years before reaching Earth.

其中的一些粒子在到达地球前已经传播了几十亿年。

When they enter our atmosphere, they collide with the molecules there,

当它们进入地球大气层，就会和大气中的分子碰撞，

generating secondary cosmic rays,

产生次级宇宙线，

lighter particles with less energy than the original.

由更轻的、具有更少能量的粒子组成。

Most of these are absorbed into the atmosphere,

大部分粒子被大气吸收，

but some are able to reach the ground, even passing through our bodies.

但也有部分粒子能够到达地表，甚至穿过我们的身体。

At sea level, this radiation is fairly low.

在海平面上，辐射粒子已经非常慢了。

But people who spend a lot of time at higher altitudes,

但是对于在更高海拔停留更久的人们，

such as airline crews, are exposed to much more.

比如航线的机组人员，会受到更多的辐射。

What makes cosmic rays useful as messengers

使宇宙线能够作为“信使”的特质，

is that they carry the traces of their origins.

是它们带着产生它们的源的信息。

By studying the frequency with which different particles occur,

通过研究不同粒子出现的频率，

scientists are able to determine the relative abundance of elements,

科学家能够区别不同元素在宇宙中的相对丰度，

such as hydrogen and helium, within the universe.

比如氢元素和氦元素。

But cosmic rays may provide even more fascinating information

其实宇宙线还可以提供更有趣的信息

about the fabric of the universe itself.

关于宇宙本身的组成。

An experiment called the Alpha Magnetic Spectrometer, A.M.S.,

有一个叫做阿尔法磁谱仪（A.M.S.）的实验装置，

has recently been installed on board the International Space Station,

最近被安装在国际空间站，

containing several detectors that can separately measure

它包含多个探测器

a cosmic ray particle's velocity, trajectory, radiation, mass and energy,

可以分别测量宇宙线粒子的速度、径迹、辐射、质量和能量，

as well as whether the particle is matter or antimatter.

以及分辨这个粒子是物质粒子还是反物质粒子。

While the two are normally indistinguishable,

尽管二者通常是不可区分的，

their opposite charges enable them to be detected with the help of a magnet.

它们相反的荷使我们可以通过磁铁区别它们的行为。

The Alpha Magnetic Spectrometer is currently measuring 50 million particles per day

阿尔法磁谱仪现在每天测量五千万个粒子，

with information about each particle being sent in real time from the space station

并实时地将每个粒子的测量信息

to the A.M.S. control room at CERN.

从空间站发送到位于欧洲核子中心（CERN）的阿尔法磁谱仪实验控制室。

Over the upcoming months and years,

在未来的几个月到几年的时间，

it's expected to yield both amazing and useful information about antimatter,

我们期待它能给我们更多更惊奇而有用的关于反物质的信息，

the possible existence of dark matter,

关于可能存在的暗物质的信息，

and even possible ways to mitigate the effects

甚至找到减轻在太空旅行时受到宇宙线辐射的可能方式。

of cosmic radiation on space travel.

As we stay tuned for new discoveries, look to the sky on a clear night,

我们对新发现怀抱希望，

and you may see the International Space Station,

在晴朗的夜晚仰望星空，你或许会看到国际空间站，

where the Alpha Magnetic Spectrometer receives the tiny messengers

阿尔法磁谱仪就在那里接收微小的宇宙信使，

that carry cosmic secrets.

而这些信使携带着宇宙的秘密。