Why neutrinos matter - Sílvia Bravo Gallart

譯者: Remy Liu 審譯者: willy 尉齊

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

它们无处不在，你却视而不见。

Trillions of them are flying through you right this second,

就在此刻，它们正数以万亿地穿透你的身体，

but you can't feel them.

而你却浑然不觉。

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

这些鬼魂般的粒子叫做中微子，如果我们可以捕获中微子，

they can tell us about the furthest reaches

就会告诉我们关于宇宙中最遥远，

and most extreme environments of the universe.

最极端的环境（是什么样子）。

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.

意思是它们不能像原子那样再被裂分成其他的粒子。

Elementary particles are the smallest known building blocks

基本粒子是宇宙中已知的构建万物的

of everything in the universe,

最小建筑材料。

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

而中微子则是小中之最。

A million times less massive than an electron,

比电子要小上几百万倍的中微子

neutrinos fly easily through matter, unaffected by magnetic fields.

可以轻而易举穿透物质，不受磁场影响。

In fact, they hardly ever interact with anything.

实际上，它们几乎不与任何其它东西发生互动。

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

这就意味着它们可以在宇宙中沿直线

for millions, or even billions, of years,

运动数百万，甚至几十亿年，

safely carrying information about where they came from.

安全地带着出发地的信息。

So where do they come from?

那么它们来自哪里呢？

Pretty much everywhere.

基本上来自四面八方。

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

你的身体里钾的放射性衰变就会产生中微子。

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.

会制造出细雨般的中微子群。

They're produced by nuclear reactions inside the sun

太阳内部的核反应也会产生中微子，

and by radioactive decay inside the Earth.

地球内部的放射性衰变也会产生中微子。

And we can generate them in nuclear reactors

我们可以在核反应堆中，

and particle accelerators.

和粒子加速器中制造出中微子。

But the highest energy neutrinos are born far out in space

但是最高能量的中微子诞生在遥远的太空深处

in environments that we know very little about.

那里的环境我们知之甚少。

Something out there, maybe supermassive black holes,

那里，有可能是超级巨大的黑洞，

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

也有可能是我们尚未发现的宇宙动能，

accelerates cosmic rays to energies over a million times greater

把宇宙射线加速到携带着百万倍于

than anything human-built accelerators have achieved.

任何人造的加速器产生的动能。

These cosmic rays, most of which are protons,

这些宇宙射线，大部分是质子，

interact violently with the matter and radiation around them,

和其他物质激烈反应，质子周围的辐射

producing high-energy neutrinos,

产生高能中微子，

which propagate out like cosmic breadcrumbs

它们像宇宙中的面包屑一样裂殖出来，

that can tell us about the locations

可以告诉我们宇宙中最强进的发动机

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

的位置和内部状况。

That is, if we can catch them.

假如，我们能够捕捉到那些中微子的话。

Neutrinos' limited interactions with other matter

中微子与其他物质有限的互动，

might make them great messengers,

可能让其成为伟大的信使，

but it also makes them extremely hard to detect.

但是同时也让它们极其难以被检测到。

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

一个方法是在它们的必经之路上放置巨量的纯透明物质，

and wait for a neutrino to reveal itself

等待中微子通过撞击原子核

by colliding with the nucleus of an atom.

自己现出原形。

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

这就是南极洲上“方冰”，世界上最大的

the world's largest neutrino telescope.

中微子望远镜里面发生的情形。

It's set up within a cubic kilometer of ice

它建在一个千米级的冰立方内部

that has been purified by the pressure

这些冰已经被压力

of thousands of years of accumulated ice and snow,

和几千年来累积的冰雪纯化，

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

成为地球上最纯净的固体。

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

尽管穿透装有5000多个监测器钻孔的冰体，

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

大部分宇宙中微子全都杳然穿过，不着痕迹。

But about ten times a year,

但是一年大概有十余次，

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

会有一个高能中微子撞击冰分子，

shooting off sparks of charged subatomic particles

射出带电的亚原子粒子火花

that travel faster through the ice than light does.

那火花会比光速更快穿透冰。

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

就像喷气飞机超越音速时

produces a sonic boom,

会产生音爆一样，

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

这些超光速带电粒子会留下一个蓝色的光锥

kind of a photonic boom.

类似于某种光爆。

This light spreads through IceCube,

种种光在“方冰”中穿透，

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

击中表层下面一英里深的一些监测器

Photomultiplier tubes amplify the signal,

光子倍增管增强信号，

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

包含着带电粒子的路径和能量信息

The data are beamed to astrophysicists around the world

数据会射送给世界各地的天体物理学家

who look at the patterns of light

他们观察光的形态

for clues about the neutrinos that produced them.

寻找产生它们的中微子的线索

These super energetic collisions are so rare

这些超级能量的撞击如此稀少

that IceCube's scientists give each neutrino nicknames,

以至于“方冰”的科学家给每一颗中微子都起了昵称，

like Big Bird and Dr. Strangepork.

比如“大鸟”或者“斯特朗哥博格博士”

IceCube has already observed

“方冰”已经观测到了

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

监测到的中微子终究将会告诉我们宇宙射线来自哪里

and how they reached such extreme energies.

以及为什么它们能够达到如此的极高能量

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

已经给了我们愈发能量充沛的

and continuously surprising views of the universe.

和不断令人吃惊的，宇宙的视角

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

我们现在正处于中微子宇宙学时代的黎明中，

and we have no idea what revelations IceCube

我们还不甚了解“方冰”的和其他的

and other neutrino telescopes may bring us

中微子望远镜可以给我们带来的启示

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

关于宇宙中最狂野，最高能的现象。