Name: 【TED-Ed】全世界最冷的東西是什麼？ (What is the coldest thing in the world? - Lina Marieth Hoyos)
Uploaded: 2022-07-20T21:01:10.000Z
Duration: 4 min 26 s

The coldest materials in the world aren't in Antarctica; they're not at the top of Mount Everest or buried in a glacier.

全世界最冷的東西不是在南極，也不是在珠穆朗瑪峰上，更不是被埋在冰河裡。

程度副詞

Clouds of gases held just fractions of a degree above absolute zero.

由氣體形成的雲層只比絕對零度高一點點的一團氣體。

That's 395 million times colder than your refrigerator, 100 million times colder than liquid nitrogen, and four million times colder than outer space.

那比你的冰箱還要冷 3.95 億倍，比液態氮還冷 1 億倍，比外太空的溫度還低了 400 萬倍。

Temperatures this low give scientists a window into the inner workings of matter, and allow engineers to build incredibly sensitive instruments that tell us more about everything from our exact position on the planet to what's happening in the farthest reaches of the universe.

如此低溫的溫度給科學家一個窗口來探討物質內部的運作，也讓工程師們可以製造出極為敏感的儀器，好讓我們知道更多資訊——關於我們在地球上所在的位置，一直到離我們最遠的宇宙所發生的事。

How do we create such extreme temperatures?

In short, by slowing down moving particles.

簡單來說，就是把移動中的粒子速度減緩。

When we're talking about temperature, what we're really talking about is motion.

當我們講到溫度時，我們在說的其實是運動。

The atoms that make up solids, liquids, and gases are moving all the time.

這些組成固體、液體、和氣體的原子則不停地在運動。

When atoms are moving more rapidly, we perceive that matter as hot.

當原子快速移動時，我們會感覺到熱。

When they're moving more slowly, we perceive it as cold.

當原子移動緩慢時，我們接受到冷。

To make a hot object or gas cold in everyday life, we place it in a colder environment, like a refrigerator.

生活中，如果要將一個物體或液體變冷的話，我們會把它們放到一個相對冷的環境，像是冰箱。

Some of the atomic motion in the hot object is transferred to the surroundings, and it cools down.

有些在熱的物體裡的原子會轉移到環境當中，進而使物體冷卻。

But there's a limit to this: Even outer space is too warm to create ultra-low temperatures.

但這樣的冷卻還是有極限的，要創造極度低溫，連外太空的環境都太熱。

So instead, scientists figured out a way to slow the atoms down directly – with a laser beam.

所以呢，科學家想出了一個辦法能夠直接使原子減速——使用雷射光。

Under most circumstances, the energy in a laser beam heats things up.

在大部分的情況下，雷射光會加熱物體。

But used in a very precise way, the beam's momentum can stall moving atoms, cooling them down.

但如果使用得很精準的話，雷射光可以使移動中的原子減速，進而降低溫度。

That's what happens in a device called a magneto-optical trap.

這就是磁光陷阱 (MOT) 的運作原理。

Atoms are injected into a vacuum chamber, and a magnetic field draws them towards the center.

原子被注入真空的空間中，而磁場會把它吸引到正中間。

A laser beam aimed at the middle of the chamber is tuned to just the right frequency that an atom moving towards it will absorb a photon of the laser beam and slow down.

鐳射光會瞄準空間中的正中心，調到正確的頻率，這樣就能使移動中的原子吸收雷射光的光子，然後減緩速度。

The slow down effect comes from the transfer of momentum between the atom and the photon.

這個減速的效果來自動力的轉變，介於原子與光子之間。

A total of six beams, in a perpendicular arrangement, ensure that atoms traveling in all directions will be intercepted.

六條垂直排列的光束，確保移動的原子都會被攔截下來。

At the center, where the beams intersect, the atoms move sluggishly, as if trapped in a thick liquid — an effect the researchers who invented it described as "optical molasses."

在正中間，也就是光束的交界處，原子的移動會變得很遲緩，就像是被困在黏稠的液體中，發明這個方法的人稱之為「蜜糖光學」。

A magneto-optical trap like this can cool atoms down to just a few microkelvins — about -273 degrees Celsius.

這樣的磁光陷阱可以把原子冷卻至絕對溫標，大約是負 273 度攝氏。

This technique was developed in the 1980s, and the scientists who'd contributed to it won the Nobel Prize in Physics in 1997 for the discovery.

這項技術在 1980 年代被開發，而有貢獻的科學家們在 1997 年贏得了諾貝爾物理學獎。

Since then, laser cooling has been improved to reach even lower temperatures.

從此之後，雷射冷卻就一直經過改良，可以達到更低的溫度。

But why would you want to cool atoms down that much?

但是為什麼要冷卻原子到如此低溫呢？

First of all, cold atoms can make very good detectors.

首先，低溫的原子可以當一個很好的偵測者。

With so little energy, they're incredibly sensitive to fluctuations in the environment.

有著極低的能量，他們對於環境中的波動是異常的敏感。

So they're used in devices that find underground oil and mineral deposits, and they also make highly accurate atomic clocks, like the ones used in global positioning satellites.

所以他們會被用在找尋地底的石油及礦物的儀器上，而且他們也是非常精準的原子鐘，像是用於全球定位的衛星當中。

Secondly, cold atoms hold enormous potential for probing the frontiers of physics.

再者，低溫的原子有著極大的潛能來探測尚未被開發的物理學。

Their extreme sensitivity makes them candidates to be used to detect gravitational waves in future space-based detectors.

他們極佳的敏銳性使他們成為在未來太空中引力探測器的絕佳候選人。

They're also useful for the study of atomic and subatomic phenomena, which requires measuring incredibly tiny fluctuations in the energy of atoms.

他們在原子與次原子的現象研究中有絕佳的幫助，因為這類研究需要測量原子中極微小的能量波動。

Those are drowned out at normal temperatures, when atoms speed around at hundreds of meters per second.

這些波動在正常的溫度下是看不出來的，尤其是當原子的速度達到每秒 100 公尺時。

Laser cooling can slow atoms to just a few centimeters per second— enough for the motion caused by atomic quantum effects to become obvious.

雷射冷卻可以把原子的速度降到每秒只有幾公分——這足夠使原子量所形成的運動變得顯而易見。

Ultracold atoms have already allowed scientists to study phenomena like Bose-Einstein condensation, in which atoms are cooled almost to absolute zero and become a rare new state of matter.

極度低溫的原子已經讓科學家能夠研究像是玻色-愛因斯坦凝聚，原子被降到幾乎絕對零度，進而變成一個全新的物質。

So as researchers continue in their quest to understand the laws of physics and unravel the mysteries of the universe, they'll do so with the help of the very coldest atoms in it.

只要研究人員持續在物理學中調查和解開宇宙的奧妙，他們還是會繼續受到極度低溫原子的幫助。