Why neutrinos matter - Sílvia Bravo Gallart

翻译人员: Gabriella Hu 校对人员: yuan longquan

They're everywhere, but you will never see one.

他们无处不在，但是你永远都看不到它们

Trillions of them are flying through you right this second,

此时此刻，它们数以万亿从你身体中飞过，

but you can't feel them.

但是你感觉不到它们的存在

These ghost particles are called neutrinos and if we can catch them,

这些幽灵粒子叫做中微子， 如果我们能抓到它们的话，

they can tell us about the furthest reaches

他们能够告诉我们宇宙中最遥远，

and most extreme environments of the universe.

最极端的环境

Neutrinos are elementary particles,

中微子是基本粒子,

meaning that they can't be subdivided into other particles the way atoms can.

也就是说它们不能像原子那样被分成更小的粒子

Elementary particles are the smallest known building blocks

基本粒子是已知的最小的粒子，

of everything in the universe,

是构造宇宙中一切的建筑材料，

and the neutrino is one of the smallest of the small.

而且中微子是最小的

A million times less massive than an electron,

比电子还要小一百万倍，

neutrinos fly easily through matter, unaffected by magnetic fields.

中微子能够轻易穿透物体，不受磁场影响

In fact, they hardly ever interact with anything.

实际上，它们几乎不与任何东西接触

That means that they can travel through the universe in a straight line

这意味着它们能够沿直线穿越宇宙

for millions, or even billions, of years,

长达数百万年，甚至数十亿年，

safely carrying information about where they came from.

携带着它们的来源地的信息

So where do they come from?

那么它们到底从哪里来呢？

Pretty much everywhere.

几乎到处都是

They're produced in your body from the radioactive decay of potassium.

你的体内的钾的放射性衰变会产生中微子

Cosmic rays hitting atoms in the Earth's atmosphere

宇宙射线在地球大气层中撞击原子

create showers of them.

能够创造出一大波中微子

They're produced by nuclear reactions inside the sun

太阳中的核反应和

and by radioactive decay inside the Earth.

地球内部的放射性衰变都能产生中微子

And we can generate them in nuclear reactors

而且，我们也能够在核反应堆和

and particle accelerators.

粒子加速器中生成中微子

But the highest energy neutrinos are born far out in space

但是最高能量的中微子来源于太空深处

in environments that we know very little about.

来自我们知之甚少的环境中

Something out there, maybe supermassive black holes,

宇宙中某个深处，或许有一个巨大的黑洞，

or maybe some cosmic dynamo we've yet to discover,

或者有一个我们还未发现的“宇宙发电机”，

accelerates cosmic rays to energies over a million times greater

把宇宙射线加速成动能的速度

than anything human-built accelerators have achieved.

比任何人造加速器快超过一百万倍

These cosmic rays, most of which are protons,

这些宇宙射线，大多是都是质子，

interact violently with the matter and radiation around them,

与它们周围的物质和辐射产生剧烈反应

producing high-energy neutrinos,

创造出带有高能量的中微子，

which propagate out like cosmic breadcrumbs

它们像面包屑一样，在宇宙中传播

that can tell us about the locations

它们能够告诉我们宇宙中

and interiors of the universe's most powerful cosmic engines.

最强大的发动机的所在地和内部构造

That is, if we can catch them.

前提是，我们必须先抓到它们

Neutrinos' limited interactions with other matter

中微子与别的物体的有限的接触

might make them great messengers,

使它们成为极好的信使，

but it also makes them extremely hard to detect.

但是同时也使它们很难被发现

One way to do so is to put a huge volume of pure transparent material in their path

一种办法是在它们的路线上放置大量的纯透明物质

and wait for a neutrino to reveal itself

然后等待中微子撞击原子核

by colliding with the nucleus of an atom.

自现原形

That's what's happening in Antarctica at IceCube,

这就是南极洲上IceCube观测站试图做的事：

the world's largest neutrino telescope.

世界上最大的中微子望远镜

It's set up within a cubic kilometer of ice

它被设置在一立方千米的冰内

that has been purified by the pressure

这些冰被几千年

of thousands of years of accumulated ice and snow,

累积下来的冰雪的压强纯化了，

to the point where it's one of the clearest solids on Earth.

以至于变成地球上最纯净的固体之一

And even though it's shot through with boreholes holding over 5,000 detectors,

尽管用装有超过5000个侦测器的钻孔钻入冰面，

most of the cosmic neutrinos racing through IceCube will never leave a trace.

大多数中微子依旧飞过IceCube，不留下一丝痕迹

But about ten times a year,

但是每年大约有十次，

a single high-energy neutrino collides with a molecule of ice,

一个高能量的中微子撞击一个冰分子，

shooting off sparks of charged subatomic particles

带点亚原子粒子如火花一般弹射出来

that travel faster through the ice than light does.

穿越冰层的速度比光速还快

In a similar way to how a jet that exceeds the speed of sound

好比一架超音速飞机

produces a sonic boom,

会产生音爆，

these superluminal charged particles leave behind a cone of blue light,

这些超光速的带电粒子会留下蓝色的光椎

kind of a photonic boom.

像光爆一样

This light spreads through IceCube,

这种光传遍IceCube，

hitting some of its detectors located over a mile beneath the surface.

击中层面下一英里多深的探测器

Photomultiplier tubes amplify the signal,

光电倍增管将信号放大，

which contains information about the charged particles' paths and energies.

里面包含带电粒子的途径和能量信息

The data are beamed to astrophysicists around the world

这些数据被传输给世界各地的天体物理学家，

who look at the patterns of light

他们观察光的规律，

for clues about the neutrinos that produced them.

寻找产生这些光的中微子

These super energetic collisions are so rare

这种超级能量撞击特别罕见，

that IceCube's scientists give each neutrino nicknames,

IceCube科学家们甚至给每一个中微子起昵称，

like Big Bird and Dr. Strangepork.

比如 ”大鸟“，还有 ”Strangepork博士“

IceCube has already observed

IceCube已经观测到

the highest energy cosmic neutrinos ever seen.

已见的最高能量的宇宙中微子

The neutrinos it detects should finally tell us where cosmic rays come from

侦测到的中微子终于可以告诉我们宇宙射线从哪里来

and how they reached such extreme energies.

还有它们如何达到如此高的能量

Light, from infrared, to x-rays, to gamma rays,

光，从红外线，到x射线，到伽马射线，

has given us increasingly energetic

已经给了我们日益强大，

and continuously surprising views of the universe.

和不断令人吃惊的宇宙视角

We are now at the dawn of the age of neutrino astronomy,

我们现在已经能看到中微子宇宙学时代的曙光，

and we have no idea what revelations IceCube

我们还不知道IceCube和其它的

and other neutrino telescopes may bring us

中微子望远镜能够给我们带来怎样的启示

about the universe's most violent, most energetic phenomena.

关于宇宙中最猛烈，最强大的现象