They inhabit the dark and vast space between the stars.

它們位於恆星之間的廣大空間與黑暗中

Drifting alone through eternal darkness, no light warms their surfaces,

它們在永恆的黑暗中獨自的漂流 沒有任何的陽光照射在它們的表面上

and they're exposed to the freezing cold of outer space.

只能暴露在寒冷的外太空

They know no seasons, no days, and no nights, which could give away the passing of time.

在上面沒有四季、沒有白天、也沒有夜晚 讓你感覺不到時間的流逝

And yet, rogue planets might carry alien life

然而，流浪行星上可能存在外星生命

to all corners of the galaxy.

並帶著這些生命到宇宙的各個地方

How would that work?

怎麼會這樣？

And how does a planet become a rogue anyway?

而流浪行星又是怎麼誕生的？

[Music]

*開場音樂*

There are several very different things that get called rogue planets.

有幾個截然不同的星體被稱作流浪行星

For example, sub-brown dwarfs -- gas giants that form from collapsing gas clouds

舉個例子：次棕矮星 一個由星雲塌縮而成的巨大氣體

and are the boring little brothers of brown dwarfs.

也是棕矮星的小兄弟

They're a sort of failed star,

它們是一種失敗的恆星

and we'll now stop talking about them.

但我們現在先不討論它們

A far more interesting sort of rogue, are terrestrial planets, similar to Earth,

一種更有趣的流浪是像是地球的類地行星

that got kicked out of their planetary system.

被它的行星系統給踢出去了

Young star systems are dangerous places,

年輕的星系是一個很危險的地方

where protoplanets are battling for the available mass,

那邊的原行星在爭奪可以取得的質量

guzzling up as much material as possible.

並盡可能的吞掉所有的物質

In this fight for dominance, they collide with each other,

在爭奪的過程中，它們會碰撞對方

or get dangerously close to each other's orbits.

或是危險地靠近對方的軌道

If a very massive planet moves its orbit closer to the star,

如果有一個質量非常大的行星離恆星很近時

it can kick smaller planets out of the system.

它會將比較小的行星踢出這個行星系統

But just because a planet has survived the growing pains of formation,

但是僅僅因為一顆行星在生長的痛苦中倖存下來

doesn't mean it's safe.

並不意味著它是安全的

Planetary systems can be disrupted by flybys from stars,

行星系統會在任何時候被經過的恆星

or black holes, at any point.

或是黑洞給干擾

Up to half of all planets born could end up as rogues.

在所有誕生的行星中，有一半最後會變成流浪行星

Scientists don't agree on the numbers,

科學家們不同意這個比例

but it's likely that, at the very least,

但保守估計

there are billions of rogue planets in the Milky Way alone.

在銀河系中有數十億的流浪行星

Most rogues will share the same depressing fate,

大部分的流浪行星都有相同的悲慘命運

as their star becomes smaller, day by day,

當它們的太陽隨著日子不斷變小

the planet's surface quickly cools down to minus 270 degrees Celsius.

行星表面的溫度將會快速地掉到零下270℃

If they have oceans, they'll freeze and become as hard as bedrock.

海洋會結冰，而且變得像是基岩一樣硬

Their atmospheres will sink down to the surface and eventually freeze, too.

大氣層會下沉到表面，最終也會結冰

But, weirdly enough,

但奇怪的是

some of these frozen, dark deserts could harbor life.

這些冰凍的黑暗沙漠可能蘊藏生命

To understand how, let's imagine a planet similar to Earth,

為了理解原因，我們先想像一顆像是地球的行星

in the same order of magnitude in terms of mass and composition.

質量及成分都跟地球相同

If we put it into deep space, how could it still support life?

如果我們把它丟到太空的深處，它怎麼還能孕育生命？

As far as we understand the nature of life,

就我們目前對生命的了解

there is one indispensable ingredient it needs: liquid water.

有一個是不可或缺的成分：液態水

Water is important because it mixes things,

水之所以重要是因為它可以將物質或是能量結合

both matter and energy,

讓有趣的化學反應發生，像是生命

which lets interesting chemistry happen, like life.

所以我們的星球需要足夠的能量

So our planet needs enough energy

讓至少一部分的海洋能夠溫暖到足以將水維持在液態

to keep at least a part of our oceans warm enough

令人討厭的是，大約地球99.97%的能量都是來自太陽

to sustain liquid water.

因此我們想像的流浪行星只能夠使用剩下0.03%的能量

Annoyingly, about 99.97% of Earth's energy budget comes from the Sun.

而這些能量幾乎全部是來自它中心的熱

So our imaginary rogue earth needs to work

地球的內核是一顆巨大的鐵球

with the 0.03 percent of energy it has left,

與太陽的表面一樣熱

which almost exclusively comes from its hot center.

並被由液態金屬所組成的外核給包圍

Earth's inner core is a giant metal ball,

這些液態金屬非常緩慢地凝固

about as hot as the surface of the Sun,

而在這過程中會釋放出大量的熱

that's surrounded by the outer core made up of liquid metals

只要這個過程持續發生

that are very, very slowly solidifying

地球就會處於地質活躍的狀態

releasing a lot of heat in the process.

固體及液體的物質將會四處流動

As long as this process is ongoing,

並將能量輸送到地表

our planet will be geologically active

在地表就會做為地熱能來利用

with solid and liquid material moving around

雖然每顆行星的熱核心最終都會冷卻下來

and transporting energy to the surface

但這會花費數十億年

where it can be harnessed as geothermal energy.

對生命來說，有足夠的時間來生存與生長

While the hot core of every planet will cool off eventually,

甚至還有一種情況能夠讓像是地球的行星 還有尚未結冰的海洋

this process takes billions of years.

如果該行星有著密度極高、壓力極大的氫大氣

Enough time for life to come into existence and thrive.

則氣體就不會結冰

There's even one scenario that could allow

並且能夠困住足夠試圖離開行星的熱量

an Earth-like planet to have oceans that are not frozen over.

使海洋一路延伸到地表

If the planet had an extremely dense and high-pressure hydrogen atmosphere,

還有一個保持溫暖的可能：衛星

the gas would not freeze

如果流浪行星帶著一顆或更多的衛星一起流浪的話

and could trap enough of the heat trying to escape the planet

那麼足夠大的衛星能夠透過潮汐力 將額外的能量注入到系統中

to enable oceans that extend all the way to the surface.

這些潮汐力每天都像是在揉麵團一樣

And there's another possible way to stay warm: moons.

拉長和擠壓著行星，使星球保持溫暖

If a rogue planet brings a moon or more along with them,

但流浪生命最可能會遇到的情況

a large enough moon could inject additional energy into the system

是在一個一公里厚的水冰層下的海洋中生存

via tidal forces.

這不是個無稽之談，因為在太陽系中 已經有幾個這樣的例子了

These forces stretch and squeeze the planet a little bit every day,

所以生命要怎麼在一片漆黑又寒冷的海底生存呢？

like kneading dough, keeping it warm.

地球上，在完全黑暗的海底

But the most likely scenario for a rogue bearing life

於火山活躍的地區中

is one with sub-glacial oceans

有著叫做黑色煙柱的海底熱泉

under a kilometer thick layer of mostly water ice.

這些煙柱會噴出一團黑色的物質和熱水

These are not completely absurd, since we already have a few of them in the Solar System.

讓地函能提供穩定的礦物質

So how could life sustain itself at the bottom of a completely dark, cold ocean.

細菌會攝取這些礦物質，並製造有機物質

On Earth, deep down in our oceans in complete darkness,

這些有機物質會吸引甲殼動物、雙殼動物、蝸牛

in volcanically-active areas,

魚類、章魚，甚至長達2公尺的管蟲

there are hydrothermal vents called black smokers.

海底噴泉不只是各式各樣生物的家鄉

They spew out a cloud of black material and hot water

在數十億年前，也是最初地球上的生命互相競爭的場所

providing a constant flow of minerals from Earth's mantle.

在流浪行星的漆黑海洋中，類似的情況或火山活動

Bacteria feed on the minerals and produce organic materials,

或許是我們目前能夠想像的複雜生態系統的起點與基礎

which attracts crustaceans, bivalves, snails,

流浪行星的海洋中的生態系統有一個優點

fish, octopus, and tube worms up to 2 meters long.

就是它的環境非常的穩定

Not only are hydrothermal vents home to an incredibly diverse group of living beings,

厚冰蓋能夠保護它免於各類型的滅絕事件

but also a contender for the place where life could have begun on Earth

並且只要地核持續提供能量

billions of years ago.

一切基本上就跟以前沒什麼兩樣

In the dark ocean of a rogue planet, similar events or volcanic activity,

生命最有可能以細菌或是微生物的形式出現

could be the starting point and basis

但只要經過足夠的時間

for complex ecosystems we can only imagine right now.

更多複雜的外星生物可以進食更小的生物並成長

One upside an ecosystem in a rogue planet ocean has,

智慧生物在這種的環境中誕生並不是不可能

is that the environment is extremely stable.

如果真的誕生了，他會發現他處在一個很奇怪的世界

The thick ice sheet protects it from all sorts of extinction events,

被頂部無法通過的冰層

and, as long as the energy from the core keeps on coming,

以及底部的基岩給困住

things stay pretty much the same.

沒有任何的植物來儲存能量

The most likely forms of life are bacteria and other microorganisms.

就不會有任何的木頭、石油或煤炭

But, given enough time,

就算真的有，在海中你也不可能會發現火

more complex alien animals could feed on the smaller beings and thrive.

沒有了火，就無法將金屬鍛造成更有用的工具

It's not impossible that intelligent life could emerge in such an environment.

我們的外星人朋友或許永遠都無法打破這層冰

If it did, it would find itself in a pretty weird world.

他們不會理解什麼叫做「外面」

Constricted by an impassable wall of rock-hard ice at the top,

甚至認為這個小世界就是一切了

and bedrock at the bottom.

數百萬的世代在這個漆黑的海洋中生老病死

Without any plants to store star energy,

而他們永遠不會知道在冰層外的宇宙有多麼的大

there would be no wood, oil, or coal.

直到他們行星的核心冷卻

Even if there were, it's not like you'd discover fire at the bottom of an ocean.

所有生命都消失殆盡

Without this energy, metals may never be forged into useful things.

當海洋完全結冰之後

Our intelligent alien friends might never break through the ice.

殘存下來的文化與生態系統

They might never realize that there is such a thing as outside,

將會永遠的埋葬在這個冰凍墳墓之中

and assumed that their small world is all there is.

仔細想想，或許不知道這件事情會比較好

Millions of generations might live and die in these dark oceans,

這個消息讓人不安，但同時又讓人興奮

ignorant of the unbelievably big universe above the ice.

宇宙中或許有豐富的生命

Until the core of their planet cools off,

但都被囚困在不可能離開的行星上

and all life vanishes.

像這樣的世界可能經常經過太陽系 只是我們不知道而已

As the oceans completely freeze,

或許有一天，在遙遠的未來

the remnants of cultures and ecosystems

人類將踏上這些冰凍世界

will be trapped in an icy grave forever.

並向他們打聲招呼

If you think about it, it might be better not to be aware of all that.

我們滿喜歡陰沉的未來場景

But the concept is disturbing and exciting.

但我們回到現在，有個不一樣的驚喜

The universe might be teeming with life,

許多觀眾想要知道我們是怎麼做影片的

trapped on planets that are basically impossible to leave.

因此，我們製作了一個影片來講解

Worlds like this could frequently pass the Solar System, without us even knowing.

Kurzgesagt 與我們最喜歡的 創作者線上學習社區 Skillshare 合作

Maybe one day, in the far future,

製作了三部的系列課程來讓你學習

humans will set foot on one of these frozen worlds

我們特別的動畫風格，以及影片中的場景

and try to say "hello."

不過並不是只有我們告訴你一些指點和技巧

Okay, so we love gloomy future scenarios,

Skillshare 的高級會員可以 不受限制的觀看超過25,000部各式各樣的課程

but let's go back to the present for a different kind of surprise.

包括了：寫作、設計、還有動畫

Many of you want to know how we make our videos,

並都是由該領域的專家來授課

so we made a video about that.

每個月只需支付10美元就可以成為高級會員

Kurzgesagt teamed up with Skillshare,

好康的來了

our favorite online learning community for creators,

點擊在資訊欄中的網址的前1,000人

to make a three-part series of classes where you can learn

前兩個月將會是免費的

our unique animation style, with scenes from our videos.

如果你常常想知道我們是如何製作這些影片的

But we're not the only ones telling you our tips and tricks there.

並自己動手學習

A Skillshare Premium Membership gives you unlimited access to more than 25,000 classes

那麼這就是你的機會

in all kinds of skills like, writing, design, and animation

from experts who know their stuff.

The Premium Membership is as low as $10 a month.

But as a treat,

the first 1,000 people to use the link in the description

will get their first two months for free.

If you've always wanted to see how we animate our videos,

and learn to do it yourself,

this is your chance.