與宇宙同齡的古老生命：英語精讀講義

Life has existed on one planet for about 4 billion years as far as we know, 片語搭配

據我們所知，生命在一顆星球上已經存在了大約40億年，

but it might have started right after the Big Bang, 文法

但它可能在宇宙大爆炸之後就立刻開始了，

when the universe was much stranger and more fantastic than today.

那時的宇宙比今天更奇特、更不可思議。

A universe that might have allowed life to develop absolutely anywhere.

那樣的宇宙或許允許生命在任何地方發展。

The cosmos might be full of the seeds of life, 慣用語

宇宙可能充滿了生命的種子，

sleeping in a dead desert,

沉睡在死寂的沙漠中，

waiting for a few drops of rain to explosively bloom and grow.

等待著幾滴雨水，便能爆炸般地綻放和生長。

Tiny and not so tiny aliens might be everywhere.

無論微小還是龐大的外星生物，可能無處不在。

In this video,

在這部影片中，

we're going to put together two highly speculative,

我們將結合兩個高度推測性，

yet scientifically grounded possibilities. 片語搭配

但有科學依據的可能性。

Check out the scientific papers in our sources.

請查看我們來源中的科學論文。

To properly explain it,

為了恰當地解釋它，

let's first look at the paradox of life on Earth.

讓我們首先看看地球上生命的悖論。

The life paradox.

生命悖論。

For its first few hundred million years,

在它最初的數億年裡，

Earth was a magma hell,

地球是一個岩漿地獄，

constantly bombarded by asteroids.

不斷遭到小行星的轟擊。

But basically,

但基本上，

the second things calmed down and the first oceans formed, 文法

在一切平靜下來、第一片海洋形成的那一刻，

life just appeared and zillions of microbes settled every nook and cranny they found. 慣用語

生命就出現了，無數的微生物佔據了它們所能找到的每個角落。

This is kind of strange.

這有點奇怪。

Life on Earth seems to be almost as old as the planet itself, 文法

地球上的生命似乎幾乎和這顆星球本身一樣古老，

as if it was waiting around for an opportunity. 文法

就好像它一直在等待機會一樣。

But life didn't only appear extremely quickly.

但生命不僅出現得極快。

In that tiny time window,

在那個極小的時間窗口內，

it also crossed a huge gap. 慣用語

它還跨越了一個巨大的鴻溝。

To qualify as living things, 片語搭配

要稱得上是生物，

even microbes need to eat,

即使是微生物也需要進食、

poop,

排泄、

grow,

生長，

and multiply.

以及繁殖。

To do that,

要做到這些，

they need a genome,

它們需要基因組，

the biological instruction manual that sets the inner workings of an organism. 表達脈絡

也就是設定生物體內部運作機制的生物學指令手冊。

How dead things with no genome became living things with genomes 文法

沒有基因組的死物是如何變成有基因組的生物的，

is one of the biggest riddles of science.

這是科學界最大的謎團之一。

Simplifying a lot,

簡單來說，

the problem is that to have a functioning genome,

問題在於，要想擁有一個運作正常的基因組，

you need proteins,

你需要蛋白質，

and to make those proteins,

而要製造這些蛋白質，

you need a functioning genome.

你需要一個運作正常的基因組。

Both proteins and genomes are super long molecules made of pretty complex blocks

蛋白質和基因組都是由相當複雜的模塊組成的超長分子，

that are extremely difficult to assemble by chance.

純靠偶然幾乎不可能組裝成功。

It's a chicken-egg paradox with several chickens and eggs. 慣用語

這是一個有著好幾隻雞和好幾個蛋的「雞生蛋還是蛋生雞」悖論。

Once you have a finished cell,

一旦你擁有了一個完整的細胞，

the whole system works efficiently.

整個系統就能高效運轉。

But starting from simple dead stuff and reaching that level of sophistication by pure chance,

但是從簡單的死物開始，純粹依靠偶然達到那種複雜的程度，

should require an amazing amount of time for trial and error. 片語搭配

應該需要驚人的試錯時間。

So,

那麼，

how did the first living things manage to cross that gap

最早的生物是如何在短短的幾億年內，

in just a few hundred million years?

跨越那個鴻溝的呢？

Most theories about the origin of life try to explain that gap by theorizing how some primitive soup of prebiotic molecules 慣用語

關於生命起源的大多數理論，都試圖通過推論前生源分子的原始湯，

could have efficiently produced the first self-replicating entities. 用詞

是如何高效地產生出第一個自我複製的實體，來解釋這一鴻溝。

But we still don't know how exactly this would have worked.

但我們仍然不知道這一過程究竟是如何進行的。

Maybe we need to think backwards. 表達脈絡

也許我們需要逆向思考。

The clock of evolution.

演化之時鐘。

Think of genomes as a book telling the history of life. 文法

把基因組看作是一本講述生命歷史的書。

As time passed and life evolved,

隨著時間的推移和生命的演化，

more characters were introduced.

更多的角色被引入了進來。

Amoebae,

變形蟲、

fish,

魚類、

amphibians,

兩棲動物、

dinosaurs,

恐龍，

and mammals.

以及哺乳動物。

Over billions of years,

經過了數十億年，

the story of life got more and more complex. 文法

生命的故事變得越來越複雜。

A genome can be viewed as a long string of letters with biological instructions.

基因組可以被看作是一長串帶有生物學指令的字母。

And from microbes to us today,

從微生物到今天的我們，

functional genomes seem to have been increasing in size at a fairly constant rate.

功能性基因組的大小似乎在以相當恆定的速率增加。

The functional genome of fish is more than twice that of worms. 文法

魚類的功能性基因組是蠕蟲的兩倍多。

Our functional genome is about twice bigger than that of fish,

我們的功能性基因組大約是魚類的兩倍大，

and so on. 片語搭配

以此類推。

It is a bit more complicated,

實際情況要稍微複雜一點，

but for now,

但現在，

let's run with this. 慣用語

我們先以此為基礎。

When we put all these clues together, 片語動詞

當我們把所有這些線索放在一起時，

it seems that genomes have been doubling in size on average every 350 million years or so. 片語搭配

基因組的規模似乎平均每3.5億年左右翻一番。

As if evolution had been following an exponential inner clock.

就好像演化一直遵循著一個指數級的內在時鐘。

But it gets even stranger.

但這變得更加奇怪了。

The very first microbes that emerged on Earth,

地球上出現的最早的微生物，

even if they look simple, 文法

即使它們看起來很簡單，

already seem to have had pretty long and complex genomes.

似乎就已經擁有相當長且複雜的基因組了。

But how could life have achieved that level of complexity

但生命怎麼可能在如此短的時間內，

in such a short time?

達到那樣的複雜程度呢？

There may be an interesting way to solve this riddle.

或許有一個有趣的方法能解開這個謎題。

We just take our exponential clock and extrapolate it back in time to the simplest conceivable life form. 用詞

我們只需拿我們的指數時鐘，將其向過去推算，一直推算到可以想像的最簡單的生命形態。

Something equivalent to a being with a genome containing just a few letters.

相當於一個基因組裡只有幾個字母的生物。

But if we do that,

但如果我們這樣做，

we end up 10 billion years in the past, 片語動詞

我們最終會回到100億年前的過去，

more than twice the age of Earth,

這是地球年齡的兩倍多，

which means,

這意味著，

if life actually evolved like this,

如果生命確實是這樣演化的，

it didn't start here,

它就不會是在這裡開始的，

but somewhere out there, 語氣意圖

而是在外面的某個地方，

in space.

在太空中。

This would explain why life started to thrive so quickly on our young planet.

這就解釋了為什麼生命在我們年輕的星球上如此迅速地繁衍開來。

If it was already present in space like a seed, 慣用語

如果它就像一顆種子一樣早已存在於太空中，

it just needed water and warm temperatures

它所需要的只是水和溫暖的溫度，

to wake up and go on evolving. 片語動詞

就能甦醒並繼續演化。

And it would also explain the high degree of sophistication

這同時也解釋了地球上最早的生命形態，

of the first life forms on Earth.

為何具有高度的複雜性。

They could have been complex already because they might have been evolving for billions of years somewhere else in the universe.

它們可能已經很複雜了，因為它們可能已經在宇宙的某個角落演化了數十億年。

But could life really be that old?

但是生命真的有那麼古老嗎？

Maybe,

也許，

yes.

是的。

Actually,

實際上，

life could have started shortly after the universe itself was born.

生命可能在宇宙本身誕生後不久就開始了。

A Goldilocks baby universe. 文化背景

恰到好處的嬰兒期宇宙。

At its most basic level, 表達脈絡

在最基本的層面上，

life needs two things:

生命需要兩樣東西：

the right chemical elements to form complex molecules

用來形成複雜分子的合適化學元素，

and a liquid medium, 用詞

以及一種液體介質，

like water,

比如水，

in which those molecules can move and interact.

在其中，這些分子可以移動並相互作用。

The liquid medium needs to stay warm enough to remain,

液體介質需要保持足夠的溫度，以維持在

well,

呃，

liquid.

液態。

So,

因此，

when we search for life in space,

當我們在太空中尋找生命時，

we focus on Earth-like planets at just the right distance from their star, 片語搭配

我們會專注於距離恆星距離剛剛好、類似地球的行星，

warm enough to sustain liquid water.

溫度要足以維持液態水。

But there was actually a time when almost all of the universe might have been habitable. 文法

但實際上曾經有一個時期，幾乎整個宇宙都可能是宜居的。

Right after the Big Bang,

就在大爆炸之後不久，

the universe was extremely hot.

宇宙極度熾熱。

But as the cosmos expanded,

但隨著宇宙膨脹，

it cooled.

它冷卻了下來。

And between about 10 and 17 million years after the Big Bang,

在宇宙大爆炸後約1000萬到1700萬年間，

when the universe was a thousand times younger than today,

當時宇宙比今天年輕一千倍，

it was between 100°C and 0°C,

它的溫度在100°C到0°C之間，

the temperature at which water is liquid. 文法

正是水呈液態的溫度。

So,

因此，

for this window of time,

在這個時間窗口，

more than 13.7 billion years ago,

即137億多年前，

the whole universe absolutely every inch of it had the right temperature to support life. 慣用語

整個宇宙——絕對是每一寸地方——都擁有支持生命的適宜溫度。

Of course,

當然，

the right temperature alone is not enough for life. 文法

僅有合適的溫度對生命來說是不夠的。

We also need chemical elements like carbon and oxygen,

我們還需要像碳和氧這樣的化學元素，

which are forged in the cores of stars. 用詞

它們是在恆星的核心裡鍛造出來的。

But were there stars in super early cosmic times?

但是在極早期的宇宙時期有恆星嗎？

Maybe,

也許，

yes.

有的。

In regions of the universe where matter was especially dense.

在宇宙中物質特別密集的區域。

Such stars would have been very massive and gone supernova in just 3 million years, 片語搭配

這樣的恆星會非常巨大，並會在短短300萬年內變成超新星，

seeding the baby universe with the chemical elements needed to form dust, 慣用語

為嬰兒期的宇宙播下形成塵埃、

asteroids,

小行星、

planets,

行星、

and the ingredients of life.

以及生命成分所需的化學元素。

Maybe the first ancestors of life were more exotic and didn't even need water,

也許最早的生命祖先更奇異，甚至不需要水，

but thrived in substances like ammonia or ethane that can stay liquid at temperatures far below 0°C.

而是繁衍在氨或乙烷等在遠低於0°C的溫度下仍能保持液態的物質中。

They could have been sustained by the lingering warmth of the Big Bang for tens of millions of years longer, 用詞

它們可能依靠大爆炸殘存的溫暖繼續存活了幾千萬年，

well into a time when we know for sure there were stars and all the chemical elements. 片語搭配

一直持續到我們確知有恆星和所有化學元素存在的時期。

The real magic of this idea is that while the universe today is extremely deadly and hostile, 表達脈絡

這個想法真正的神奇之處在於，雖然今天的宇宙極度致命且充滿敵意，

back then,

但在那個時候，

the conditions for life might have been basically everywhere.

適合生命存在的條件可能無處不在。

For a period that may have lasted several dozen million years,

在那個可能持續了數千萬年的時期裡，

primordial life might have been able to emerge on any rock,

原始生命可能出現在任何一塊岩石上，

even between the stars,

甚至是在星際之間，

sowing the universe with the seeds of what, 文法

在宇宙中播撒下生命的種子，

billions of years later,

數十億年後，

would become bacteria,

它們會演變成細菌、

trilobites,

三葉蟲、

dinosaurs,

恐龍，

and finally us.

最終成為我們。

At some point,

在某個時刻，

the universe cooled down below the right temperature for life to thrive, 片語動詞

宇宙的溫度降到了適合生命繁衍的溫度之下，

but some of those ancestral life forms may have continued to exist in the internal warmth of the first planets,

但那些古老的生命形態中，有些可能繼續存在於早期行星內部的溫暖之中，

frozen in asteroids,

冰凍在小行星裡，

or hibernating in cosmic dust.

或者在宇宙塵埃中休眠。

Tiny seeds roaming the cosmos,

微小的種子在宇宙中遊蕩，

waiting for new hospitable places to continue evolving. 用詞

等待著新的宜居地以繼續演化。

If they did,

如果它們確實如此，

life now might be everywhere in the universe.

那麼現在的生命可能在宇宙中無處不在。

Will we ever know?

我們究竟會知道嗎？

All this makes for a nice story, 片語動詞

所有這些聽起來像是個不錯的故事，

and while both the habitability of the baby universe and our exponential clock of life are reasonable ideas, 文法

雖然嬰兒期宇宙的宜居性和我們的生命指數時鐘都是合理的想法，

they're still speculative.

但它們仍然只是推測。

One more possibility among many others trying to explain our existence today. 表達脈絡

這是許多試圖解釋我們今天存在的可能性中的另一種。

But if life came to Earth from outer space, 文法

但如果生命是來自外太空才到了地球，

then it should have seeded other places in the solar system too.

那麼它也應該在太陽系的其他地方播下了種子。

Maybe there are fossils in dry riverbeds on Mars.

也許火星乾涸的河床裡有化石。

Maybe we'll soon find life in the warm underground oceans of Enceladus or Europa. 文化背景

也許我們很快就會在土衛二或木衛二溫暖的地下海洋中發現生命。

Titan has seas, 文化背景

土衛六擁有著由乙烷和甲烷構成的海洋、

rivers,

河流，

and lakes of ethane and methane as warm as the universe when it was 90 million years old.

和湖泊，其溫度就和宇宙在9000萬年時的溫度一樣溫暖。

So,

所以，

finding exotic life on Titan would support the idea that life could have originated in the weird baby universe.

在土衛六上發現奇異生命將支持生命可能起源於奇異的嬰兒期宇宙這一觀點。

So far, 表達脈絡

到目前為止，

when we look out into the cosmos,

當我們望向宇宙深處，

we don't see anyone like us.

我們並沒有看到任何像我們一樣的存在。

But maybe that's because life needed 10 billion years or more to reach the level of complexity 文法

但也許那是因為生命需要100億年或更長的時間才能達到那種複雜的程度，

that allows for a technological species.

從而允許技術物種的誕生。

Maybe there are millions of worlds filled with microbes, 表達脈絡

也許有數以百萬計的世界裡佈滿了微生物，

oceans full of exotic fish,

海洋裡游滿了奇異的魚類，

and continents of bizarre animals.

大陸上遍佈著奇異的動物。

And maybe even others like us that just recently gained consciousness

甚至可能還有其他像我們一樣的生物，剛剛獲得了意識，

and are beginning to look at the sky,

正開始仰望星空，

wondering if they're alone. 文法

想知道他們是否是孤獨的。

Life could be flourishing right now in uncountable forms

生命此刻可能正在以無數種形式，

and in all kinds of cosmic environments.

在各種宇宙環境中繁衍生息。

And if many of us share a common cosmic origin, 文法

如果我們在很大程度上共享一個共同的宇宙起源，

we would all be part of a great cosmic family.

我們都將是一個龐大宇宙家族的一部分。

The answer may lie in our cosmic backyard. 慣用語

答案也許就在我們的宇宙後院裡。

Let's go and find out.

讓我們去尋找答案吧。