Could we create dark matter? - Rolf Landua

翻译人员: Ethan Ouyang 校对人员: Echo Yang

85% of the matter in our universe is a mystery.

宇宙中有 85% 的物质神秘莫测。

We don't know what it's made of, which is why we call it dark matter.

我们不知道它们是什么， 所以我们称它们为“暗物质”。

但是我们知道它们的存在，

But we know it's out there because we can observe its gravitational attraction

因为我们可观测它们作用在 众多星系与天体间的引力。

on galaxies and other celestial objects.

We've yet to directly observe dark matter,

虽然我们还无法直接观测暗物质，

but scientists theorize that we may actually be able to create it

但是科学家推测， 人类也许可以用世上最强大的

in the most powerful particle collider in the world.

粒子对撞机来创造暗物质。

That's the 27 kilometer-long Large Hadron Collider, or LHC,

那就是位于瑞士日内瓦， 长达 27 公里

in Geneva, Switzerland.

的大型强子对撞机，简称 LHC。

So how would that work?

那么它的工作原理是什么呢？

在 LHC 里，两个质子向反方向运动，

In the LHC, two proton beams move in opposite directions

and are accelerated to near the speed of light.

并被加速至接近光速。

At four collision points, the beams cross and protons smash into each other.

在四个撞击点上， 质子束相交， 质子相互碰撞。

Protons are made of much smaller components called quarks and gluons

质子是由更小的夸克和胶子组成的。

In most ordinary collisions, the two protons pass through each other

在一般情况下，两个质子穿过彼此

without any significant outcome.

不会产生重大影响。

However, in about one in a million collisions,

但有一百万分之一的概率，

two components hit each other so violently,

两个质子的强烈碰撞，

that most of the collision energy is set free

会释放出爆炸级的碰撞能量，

producing thousands of new particles.

生成上千个新的粒子。

It's only in these collisions that very massive particles,

理论上只有在这种碰撞中才会生成

like the theorized dark matter, can be produced.

像暗物质那样的超大粒子。

The collision points are surrounded by detectors

碰撞点的四周都有探测器，

containing about 100 million sensors.

里面有约 1 亿个感应器，

Like huge three-dimensional cameras,

就像一个大型的 3D 照相机，

they gather information on those new particles,

可以收集那些新粒子的信息，

including their trajectory,

包括它们的轨道，

electrical charge,

电荷，

and energy.

和能量。

Once processed, the computers can depict a collision as an image.

在处理完这些信息后， 电脑可以形成撞击图像。

Each line is the path of a different particle,

每条线都是不同粒子的轨迹，

and different types of particles are color-coded.

不同种类的粒子会标为不同的颜色。

Data from the detectors allows scientists to determine

探测仪记录的数据可以 让科学家们判断

what each of these particles is,

这些粒子的种类，

things like photons and electrons.

比如是光子还是电子。

Now, the detectors take snapshots of about a billion of these collisions per second

探测器每秒对撞击进行 大约十亿次的拍摄，

to find signs of extremely rare massive particles.

以寻找极其稀有的超大粒子的踪迹。

To add to the difficulty,

更加困难的是，

the particles we're looking for may be unstable

我们寻找的粒子很可能极不稳定，

and decay into more familiar particles before reaching the sensors.

以至于在到达探测器前 就衰变为常见的粒子。

Take, for example, the Higgs boson,

以希格斯玻色子为例，

a long-theorized particle that wasn't observed until 2012.

这个长期存在于理论上的粒子 直到 2012 年才被观测到。

The odds of a given collision producing a Higgs boson are about one in 10 billion,

在一次特定碰撞中产生希格斯玻色子 的几率仅为百亿分之一。

and it only lasts for a tiny fraction of a second

并且只存在了短短的一瞬，

就发了生衰变。

before decaying.

But scientists developed theoretical models to tell them what to look for.

但科学家们研制出了理论模型 来确定寻找的对象。

For the Higgs, they thought it would sometimes decay into two photons.

科学家一开始认为希格斯玻色子 会衰变为两个光子。

So they first examined only the high-energy events

所以他们起初只检测，

包含两个光子的高能量事件。

that included two photons.

But there's a problem here.

但有个问题。

There are innumerable particle interactions

有无数种粒子的相互作用

that can produce two random photons.

可以产生两个随机的光子。

So how do you separate out the Higgs from everything else?

那么应该如何将希格斯玻色子 与其他物质进行区分？

The answer is mass.

答案就是质量。

The information gathered by the detectors allows the scientists to go a step back

探测器收集的数据让科学家 能够退一步思考，

and determine the mass of whatever it was that produced two photons.

并检查产生两个光子的物质的质量。

They put that mass value into a graph

他们用这些数据制图，

and then repeat the process for all events with two photons.

然后重复产生两个光子的过程。

The vast majority of these events are just random photon observations,

大多数情况下只能观察到 随机产生的光子，

what scientists call background events.

科学家们称之为背景事件。

But when a Higgs boson is produced and decays into two photons,

但当希格斯玻色子产生并 衰变为两个光子的时候，

the mass always comes out to be the same.

这两个光子的质量通常都是相同的。

Therefore, the tell-tale sign of the Higgs boson

因此，辨识希格斯玻色子 出现的最好迹象，

would be a little bump sitting on top of the background.

就是背景图上的一个小小的隆起。

It takes billions of observations before a bump like this can appear,

这样的隆起需要经过 数亿次的观测方能出现，

and it's only considered a meaningful result

而且也只有当隆起部分 显著的高出背景图时，

if that bump becomes significantly higher than the background.

这个结果才有意义。

In the case of the Higgs boson,

在希格斯玻色子的例子中，

the scientists at the LHC announced their groundbreaking result

尽管要观测到背景图上的隆起，

when there was only a one in 3 million chance

只有区区三百万分之一的几率， 可能仅仅是统计学上的巧合，

this bump could have appeared by a statistical fluke.

LHC 的科学家们 还是得出了开创性的结论。

So back to the dark matter.

那么回到暗物质上来。

If the LHC's proton beams have enough energy to produce it,

如果 LHC 的质子束有足够的 能量来制造暗物质，

that's probably an even rarer occurrence than the Higgs boson.

成功的几率将比希格斯玻色子还小。

So it takes quadrillions of collisions combined with theoretical models

它将需要百万之四次方 的碰撞与理论模型相结合，

to even start to look.

方能初具雏形。

That's what the LHC is currently doing.

而那正是 LHC 现在在做的事。

By generating a mountain of data,

通过生成堆积如山的数据，

we're hoping to find more tiny bumps in graphs

我们希望能在图像中找到更多的隆起，

that will provide evidence for yet unknown particles, like dark matter.

那些便是未知粒子，例如暗物质， 存在的最好证明。

Or maybe what we'll find won't be dark matter,

也许我们找到的未必是暗物质，

but something else

而是其他的一些

that would reshape our understanding of how the universe works entirely.

将会改变我们对整个宇宙 的看法的物质。

That's part of the fun at this point.

那也是当前研究的乐趣之一。

We have no idea what we're going to find.

我们并不确定将会找到什么。