But why? And how? And will the universe be dead forever?

但為何？如何？而且宇宙會永遠死亡嗎？

And how do we know that?

況且，我們是怎麼知道的？

First of all, the universe is expanding.

首先，宇宙正在膨脹。

And not only that, the rate of its expansion is accelerating.

應該說不只是膨脹，宇宙正在加速膨脹。

The reason: dark energy.

原因：暗能量。

Dark energy is a strange phenomenon that scientists believe permeates the universe.

科學家相信宇宙被這個稱為暗能量的奇異現象支配。

Until 1998, we thought that the universe must work a bit like a ball that you throw into the sky.

一直到1998年，我們終於了解到，宇宙就像一個拋向天空的小球。

The ball moves up, but at some point it has to come down again.

球向上飛行，但總是會在某個時間再次落下。

But the expansion of the universe is actually speeding up.

但宇宙的膨脹速度實際上是在加速。

That’s like throwing a ball up and watching it fly away faster and faster and faster.

就像把小球丟向空中，然後看著它飛得越來越快。

Where is this acceleration coming from?

那加速度究竟來自何處？

Well, we don’t know, but we call it "dark energy".

這個嘛，我們不知道，但我們叫他 [ 暗能量 ]。

Einstein thought of it first and then decided it was stupid.

愛因斯坦首先意識其存在，但他認為暗能量很蠢。

Now, astrophysicists have decided it is plausible.

現在的天文學家認為它的存在可能性很高。

Trouble is, this is all very theoretical, and we don’t actually know what the properties of dark energy are.

問題是，它是個理論，而我們實際上也並不知道暗能量的性質。

But there are various theories and they lead us to three scenarios for the end of the universe.

但有多種理論闡述宇宙的三種可能終點。

One: the Big Rip.

第一種：[ 大撕裂 ]。

Since its birth, the universe has been expanding.

自誕生起，宇宙從未停止膨脹。

For unknown reasons new spaces created everywhere equally.

而基於某種未知的理由， 膨脹所產生的空間在各處平均分配著。

The space between galaxies expands, so they move apart.

由於星系與星系間的空間擴張， 所以它們的距離越來越遠。

The space inside galaxies also expands, but here, gravity is strong enough to keep them together.

雖然而在星系內的空間也在擴張， 但是重力的強度依然足夠維持星系的完整。

In the Big Rip scenario, the expansion accelerates up to a point where space expands so fast that gravity can’t compensate for this effect anymore.

在大撕裂模型中，空間膨脹的速度變得極端的快速，快到重力再也無法抵銷它的效果。

The result is a Big Rip.

結果就是 [ 大撕裂 ]。

At first, only large structures like galaxies are torn apart, since space between the single objects expands very fast.

首先，像星系一樣的大型結構遭到撕裂，成因自然是因為空間的快速膨脹。

Next, big bodies like black holes, stars, and planets die.

接著，像黑洞，恆星和行星一樣的大型天體死亡。

Their gravity isn’t strong enough to keep them together, so they dissolve into their components.

因為他們的重力再也沒能力將他們聚在一起，所以他們溶解成其組成物質。

In the end, space would expand faster than the speed of light.

最後，空間擴張的速度會追過光速。

Atoms would now be affected, and they would just disband.

原子會被其影響而無法形成鍵結（原子的畫像僅為示意圖）。

Once space is expanding faster than light, no particle in the universe can interact with any other particle anymore.

當擴張速度超越光速，宇宙中的任何粒子將再也無法產生任何交互作用。

The universe would dissolve into countless lonely particles that won’t be able to touch anything else in a strange, timeless universe.

宇宙將溶解成無法相互接觸的無數孤單粒子，而他們會在這個奇異，沒有時間的空間中永遠漂流。

Hmm, and you thought you felt lonely!

嗯.......而你說你很孤單？

Two: Heat death or a Big Freeze.

第二種： [ 熱寂 ] 或 [ 冷寂 ]。

In a nutshell, the difference between the Big Rip and heat death is that in a heat death scenario matter stays intact and is converted over an incredibly long but finite period of time into radiation, while the universe expands forever.

簡單來說，熱寂和大撕裂的不同處在於，在熱寂中大多物質維持其原本樣貌而且穩定，有耐性的耗費無限長的時間衰變成放射線，而同時，宇宙也會永遠的擴張。

But how does this work? Let’s talk about entropy.

怎麼做到? 我們得先談談 [ 熵 ]。

Every system tends towards the state of highest entropy, like when we have a latte macchiato.

所有系統總是傾向變成於最高熵的形態，就像這杯咖啡一樣。

Initially, it has different regions, but over time, they will cool down and disintegrate, until it’s uniform.

雖然在一開始時，存在著不同的溫度，但隨時間過去，它總是會降溫和瓦解，直到所有區域都統一。

And this also applies to the universe.

這觀點也適用於宇宙。

So, while the universe gets bigger and bigger, matters slowly decays and spreads out.

所以，當宇宙變的越來越大，物質也慢慢的衰變與分散。

At some point, after lots of generations of stars, all the gas clouds necessary to form stars will be exhausted, so the universe will turn dark.

在未來某時，數代的恆星凋亡後，而所有可以用於形成恆星的氣體雲耗盡後， 宇宙將開始轉入黑暗。

The remaining suns will die;

最後一代恆星將會死亡；

black holes will slowly degenerate and evaporate over trillions of years due to what’s known as Hawking radiation.

由於所謂的霍金輻射，黑洞也將慢慢的縮小，最終蒸發殆盡。

When this process is complete, only a dilute gas of photons and light particles remains, until even this decays.

在黑洞蒸發殆盡後， 宇宙中僅會殘存少量的光子與輕粒子存在，直到那些粒子也衰變。

All activity in the universe ceases at this point;

所有宇宙中的活動終於止息；

entropy is at its maximum and the universe is dead forever.

熵終於到達最大值，宇宙也正式完全死亡。

Unless… theoretically, it might be possible that after an incredibly long amount of time,

除非......理論上，在一段無限長的時間過後，

there might be a spontaneous entropy decrease as a result of something called "quantum tunneling", leading to a new Big Bang.

熵可能會自然的減少，並引發一個稱為[ 量子穿隧 ] 的效應，而再一次出現大霹靂。

Three: Big Crunch and Big Bounce.

第三種：[ 大擠壓 ] 和 [ 大反彈 ]。

This is the most uplifting scenario.

這個是所有理論中最正向的。

If there is less dark energy than we think or it decreases over time, gravity will be the dominating force in the universe one day.

如果暗能量比我們所想像的要少， 或如果暗能量會隨著時間減少，重力將會再次稱霸宇宙。

In a few trillion years, the rate of expansion of the universe will slow down and stop.

在數兆年內，宇宙的擴張速率將會減速，甚至停止。

After that, it reverses.

在那以後，一切會反向進行。

Galaxies will race at each other, merging as the universe becomes smaller and smaller.

星系會隨著宇宙的縮小而慢慢融合，宇宙也會變的越來越小。

Since a smaller universe also means a hotter universe, temperatures rise everywhere all at once.

由於較小的宇宙也意味著較高溫的宇宙，溫度會在宇宙各處同時上升。

One hundred thousand years before the Big Crunch, background radiation would be hotter than the surfaces of most stars, which means that they would be cooked from the outside.

在大擠壓發生千年前，背景輻射會變的比大多恆星都高，這也代表他們會被從外往內加溫。

Minutes before the Big Crunch happens, atom cores are ripped apart before supermassive black holes devour everything.

在大擠壓發生幾分鐘前，原子核會被撕裂，超巨大黑洞會在不久後吞噬一切。

Finally, all black holes would emerge into a supermassive mega-black hole that contains the entire mass of the universe,

最後，所有的黑洞會融合成一個非常巨大的黑洞，它擁有整個宇宙的質量，

and in the last moment before the Big Crunch it would devour the universe, including itself.

而它會在大擠壓前幾秒吞噬整個宇宙，甚至吞噬掉它自己。

The Big Bounce theory states that this has happened a lot of times and that the universe goes through an infinite cycle of expansion and contraction.

大反彈理論認為這個過程已經發生很多次了，而宇宙也因此經歷過了無數次的爆脹和收縮。

Well, wouldn’t that be nice?

這樣不是也很好嗎？

So what will actually happen to the universe in the end?

所以宇宙壽命的終點究竟會發生什麼事呢？

At the moment, heat death seems the most likely, but we at Kurzgesagt hope that this "dead forever" stuff is wrong and the universe will start over and over again.

從現在看來，熱寂似乎是最有可能的結局，但我們Kurzgesagt希望這個永遠的死亡是錯的，而宇宙將一次又一次的重新開始。

We don't know for sure either way, so let’s just assume the most uplifting theory is true.

既然我們完全不知未來的發展， 不如就假設最正向的理論是正確的吧。

By the way, we have a Twitter account.

喔，對了，我們有推特帳號喔。

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