How to build a dark matter detector - Jenna Saffin

譯者: Lilian Chiu 審譯者: Helen Chang

More than two kilometers below the surface of northern Ontario,

在北安大略的表面下方 兩公里以下的地方，

suspended in 345,000 liters of ultra-pure water,

懸浮在 345,000 公升超純水中的

there’s a perfect sphere.

是一個完美的球體。

It contains 3600 kilograms of liquid argon,

它含有 3,600 公斤的液態氬，

cooled to -180 degrees Celsius.

冷卻到攝氏零下 180 度。

Scientists continuously monitor this chamber from above ground,

科學家從地面上持續監看這個球室，

looking for a glimmer of light in the darkness.

在黑暗中尋找一線曙光。

Because down here,

因為在下面這裡，

deep beneath the Earth’s surface and cocooned in a watery shield,

在地球表面下很深處且 被水屏障給包住的地方，

that light would indicate the presence of one of the universe’s greatest mysteries:

那一線曙光指的就是， 這裡可能存在著宇宙最大的謎之一：

dark matter.

暗物質。

All the matter we can see, planets, stars and galaxies,

所有我們能看見的物質， 星球、星星、銀河，

doesn’t create enough gravitational pull

它們所產生出的引力並不足以

to explain the universe’s larger structure.

解釋宇宙更大的結構。

It’s dark matter, which is estimated to make up 25% of the known universe.

估計，已知宇宙的 25% 是由暗物質構成。

But despite its prevalence,

但，儘管它很普遍，

so far we haven’t been able to detect it directly.

目前為止，我們無法直接偵測到它。

It’s no small challenge.

這挑戰並不簡單。

Dark matter was so named because it doesn’t interact with any type of light,

暗物質會被這樣命名，是因為它 不會和任何類型的光交互作用，

visible or otherwise,

不論是可見光或其他光，

which means our usual observation tools

也就是說，我們一般的觀察工具

simply don’t work when trying to observe it.

就是無法用來觀察它。

But while dark matter may not be visible in the electromagnetic spectrum,

但，雖然暗物質可能 無法在電磁頻譜上看見，

it’s still matter,

它還是物質，

so we should be able to measure its interactions with other matter.

我們應該有辦法可以測量 它和其他物質的交互作用。

And if our current model of physics is correct,

如果我們目前的物理模型是正確的，

billions of sub-atomic dark matter particles

每秒鐘會有數十億暗物質

are passing through the Earth every second.

亞原子粒子通過地球。

Despite the prevalence of dark matter,

儘管暗物質很普遍，

its interactions are predicted to be rare and extremely weak.

我們預測它的交互作用 很稀少，且極微弱。

To detect these interactions,

若要偵測這些交互作用，

dark matter experiments need to be incredibly sensitive.

暗物質的實驗就必須非常靈敏。

With such sensitive equipment,

若設備夠靈敏，

the ever-present background radiation on Earth’s surface

在地球表面上經常存在的背景輔射

would create so much noise in the data

會在資料中產生出非常多的噪音，

that any dark matter particles would be completely overwhelmed.

任何暗物質粒子都會完全被淹沒。

It would be like trying to hear a pin drop on a busy city street.

就像是在繁忙的街道上試圖 聽到針落在地上的聲音一樣。

To solve this problem,

為了解決這個問題，

scientists have had to dig deep into the Earth.

科學家得要深入地球。

Dark matter experiments are set up in specialized underground labs,

他們在特製的地下實驗室中 進行物質實驗，

either in mines or inside mountains.

可能是在礦坑中或是山的內部。

The rock that makes up the Earth’s crust works like a filter,

形成地球外殼的岩石， 就像是過濾器一樣，

absorbing radiation and stopping disruptive particles.

能吸收輻射，阻擋擾亂的粒子。

The ultra-pure water in which the detector is suspended

偵測器懸浮在超純水中，

adds an additional layer of radiation filtering.

超純水又增加了一層輻射過濾。

This shielding ensures that only the particles scientists are looking for

這層屏障能確保只有 科學家想研究的粒子

can make their way into the detectors.

才能進到偵測器內。

Once these particles reach an experiment’s inner vessel,

一旦這些粒子到達實驗的內部容器，

scientists have a chance of detecting them.

科學家就有機會可以偵測到它們。

The detector media are chosen because they’re exquisitely sensitive detectors

偵測器介質之所以會被選中， 是因為它們是非常靈敏的偵測器，

that can be purified extremely well.

能被極端地純化。

These could be a liquid noble gas,

用的有可能是液態的惰性氣體、

germanium

鍺、

and silicon crystals,

矽結晶、

a refrigerant,

冷媒，

or other materials.

或其他材料。

When radiation interacts, it leaves tell-tale signs,

輻射交互作用時，會留下徵象，

such as light or bubbles,

比如光或是泡泡，

which can be picked up by the sensors inside the detector.

可被偵測器內部的感測器測量到。

The detector media are held in a central chamber made of glass

偵測器介質被放在一個 中央室裡面，材質是玻璃，

or a special type of acrylic.

或是一種特殊的丙烯酸。

These chambers have to be able to hold the substance inside

這些存放室必須要 能夠將物質維持在其中，

without interacting with it

且不會和它發生交互作用，

while withstanding incredible pressure from the water outside.

同時還要能承受 來自外部的強大水壓。

The inner vessel is surrounded by powerful sensors

容器的內部圍繞著強大的感測器，

designed to detect even the tiniest blips of light,

設計來偵測最微小的光點，

or the sound vibrations caused by a single bubble.

或是單一個泡泡造成的聲音振動。

Each sensor records data 24/7,

每個感測器都全年無休做記錄，

and experiments run for months and years at a time,

這些實驗一次就要進行 數個月甚至數年，

generating terabytes of data every day.

每天產生出的資料量 有數萬億位元組。

Building dark matter detectors is as much a feat of engineering

打造暗物質偵測器， 不僅是非凡的物理，

as it is a feat of physics.

也是非凡的工程。

By the time an experiment is ready to start collecting data,

當一項實驗準備好開始收集資料時，

years or decades of work and investment have already gone into it,

其實就已經經過了數年 甚至數十年的努力和投資，

to the tune of tens of millions of dollars.

耗資可能高達數千萬美元。

As of 2017, no dark matter particles have been directly detected.

截至 2017 年，尚未 直接偵測到暗物質粒子。

That’s not entirely surprising.

那其實並不全然讓人訝異。

Physicists expect these interactions to be incredibly rare and difficult to detect.

物理學家預期這類交互作用 非常罕見，且很難偵測到。

In the meantime,

同時，

scientists continue to develop new technologies

科學家持續開發新科技，

and increase detector sensitivity,

增加偵測的靈敏度，

closing in on where dark matter is hiding.

把焦點更集中在暗物質隱藏的地方。

And when they find it,

一旦找到，

we’ll finally be able to bring the universe’s darkest secrets into the light.

我們就能夠把宇宙 最黑暗的秘密揭開了。