nearly fourteen billion years ago,

宇宙的生命，開始於大爆炸，

and has been expanding ever since.

大約發生在 140 億年前，

But what is it expanding into?

且從此之後就不斷擴張。

That's a complicated question.

但，它會擴張到哪裡去？

Here's why:

那是個複雜的問題。

Einstein's equations of general relativity

原因如下：

describe space and time as a kind of inter-connected

愛因斯坦的廣義相對論方程式

fabric for the universe.

把空間和時間描述成

This means that what we know of as space and time

一種相互連結的宇宙構造。

exist only as part of the universe and not beyond it.

意思就是說，我們對於 空間和時間所知的一切，

Now, when everyday objects expand, they move out

都只是宇宙的一部分， 存在於宇宙中，不是宇宙外。

into more space.

當日常的物品擴張的時候，

But if there is no such thing as space to expand into,

它們會向外移動到更多的空間中。

what does expanding even mean?

但如果沒有更多的空間 可以擴張下去，

In 1929 Edwin Hubble's astronomy observations

那擴張又是什麼意思呢？

gave us a definitive answer.

1929 年，愛德溫哈伯的天文觀察

His survey of the night sky found all faraway galaxies

給了我們決定性的答案。

recede, or move away, from the Earth.

他對於夜空的調查發現 所有的遙遠銀河

Moreover, the further the galaxy, the faster it recedes.

都會後退，或是說遠離地球。

How can we interpret this?

此外，越遠的銀河， 後退的速度越快。

Consider a loaf of raisin bread rising in the oven.

我們要如何詮釋這項觀察？

The batter rises by the same amount in between each

想想看，有一條葡萄乾 麵包在爐中發酵。

and every raisin.

麵糊的發酵依據的就是

If we think of raisins as a stand-in for galaxies,

每兩個葡萄乾之間的量。

and batter as the space between them,

如果我們把葡萄乾比喻成銀河，

we can imagine that the stretching or expansion

麵糊是銀河之間的空間，

of intergalactic space will make the galaxies recede from each other,

我們就可以想像， 兩個銀河之間的空間

and for any galaxy, its faraway neighbors will recede a larger

若延伸或擴張，就會讓 這兩個銀河退開遠離彼此，

distance than the nearby ones

對任何銀河而言，在同樣的 時間內，比起相近的鄰居，

in the same amount of time.

遙遠的鄰居會退開的 距離就比較大。

Sure enough, the equations of general relativity predict a cosmic

當然，廣義相對論的方程式預測

tug-of-war between gravity and expansion.

在引力和擴張之間 會發生宇宙拔河。

It's only in the dark void between galaxies where expansion wins out,

只有在銀河之間的黑暗空間內，

and space stretches.

擴張才會勝出，空間才會延伸。

So there's our answer.

所以，我們的答案是：

The universe is expanding unto itself.

宇宙會擴張到它自己裡面。

That said, cosmologists are pushing the limits of mathematical models

然而，宇宙學家還在 將數學模型的極限向外推，

to speculate on what, if anything, exists beyond our spacetime.

來推斷在我們的空間時間之外 有什麼存在（如果有的話）。

These aren't wild guesses, but hypotheses that tackle

這些不是瞎猜， 而是假設，為了處理

kinks in the scientific theory of the Big Bang.

大爆炸科學理論中的 扭曲而做的假設。

The Big Bang predicts matter to be distributed evenly across the universe,

大爆炸預測物質會平均地 分佈到整個宇宙，

as a sparse gas --but then, how did galaxies and stars come to be?

以稀疏氣體的形式散播，

The inflationary model describes a brief era

但，這樣的話，銀河 和星星又是怎麼生成的？

of incredibly rapid expansion

膨脹模型就描述了

that relates quantum fluctuations in the energy of the early universe,

一個非常快速擴張的簡短時代，

to the formation of clumps of gas that eventually led to galaxies.

讓早期宇宙能量中的 量子擾動與氣體塊的形成

If we accept this paradigm, it may also imply our universe represents

拉上關係，最終， 這些氣體塊造成了銀河。

one region in a greater cosmic reality that undergoes endless, eternal inflation.

如果我們接受這個範式， 那可能也意味著我們的宇宙代表

We know nothing of this speculative inflating reality,

一個更大的宇宙現實 當中的一個區域，

save for the mathematical prediction that its endless expansion

而這個更大的宇宙正在 經歷無盡、永恆的膨脹。

may be driven by an unstable quantum energy state.

我們完全不了解這個 推測出來的膨脹現實，

In many local regions, however, the energy may settle by random

我們只有數學預測， 預測這無止境的擴張

chance into a stable state, stopping inflation and forming bubble universes.

可能是由一個不穩定的 量子能量狀態所驅動的。

Each bubble universe —ours being one of them

然而，在許多當地的區域， 能量可能會隨機地安頓下來，

—would be described by its own Big Bang and laws of physics.

進入穩定的狀態，不再膨脹， 也不再形成泡泡宇宙。

Our universe would be part of a greater multiverse,

每一個泡泡宇宙—— 我們的宇宙是其中之一——

in which the fantastic rate of eternal inflation makes it impossible

可以用它自己的大爆炸 和物理法則來描述。

for us to encounter a neighbor universe.

我們的宇宙只是更大的 多重宇宙的一部分，

The Big Bang also predicts that in the early, hot universe, our fundamental forces

在多重宇宙中， 永恆膨脹的驚人速度

may unify into one super-force.

讓我們沒機會遇到 任何一個鄰接的宇宙。

Mathematical string theories suggest descriptions of this unification,

大爆炸也預測，在早期高溫的 宇宙中，我們的基本「力」

in addition to a fundamental structure for sub-atomic quarks and electrons.

可能會統一成一股超級力。

In these proposed models, vibrating strings are the building blocks of the universe.

數學弦理論中，除了亞原子夸克

Competing models for strings have now been consolidated into a unified description,

和電子的基礎結構之外， 也描述了這種統一。

and suggest these structures may interact with massive, higher dimensional surfaces called branes.

在這些被提出的模型中， 震動的弦是建造宇宙的積木。

Our universe may be contained within one such brane,

其他競爭的弦模型現在已經 被整合成了統一的描述，

floating in an unknown higher dimensional place, playfully named “the bulk,” or hyperspace.

指出這些結構 可能會和「膜」互相影響，

Other branes—containing other types of universes—may co-exist in hyperspace,

膜就是更高質量高維度的表面。

and neighboring branes may even share certain fundamental forces like gravity.

我們的宇宙可能就是 在一個這樣的膜當中，

Both eternal inflation and branes describe a multiverse,

漂浮在一個更高維度的未知之地，

but while universes in eternal inflation are isolated, brane universes could bump into each other.

它有個有趣的名字 叫「體」，或超空間。

An echo of such a collision may appear in the cosmic microwave background

其他的膜—— 內含其他類型的宇宙——

—a soup of radiation throughout our universe, that's a relic from an early Big Bang era.

可能也共同存在於超空間中，

So far, though, we've found no such cosmic echo.

而相鄰的膜可能還會共享 某些基礎的力，比如引力。

Some suspect these differing multiverse hypotheses may eventually coalesce into a common description,

永恆的膨脹以及膜， 都是在描述一個多種宇宙，

or be replaced by something else.

但，雖然永恆膨脹的 宇宙是孤立的，

As it stands now, they're speculative explorations of mathematical models.

膜宇宙則有可能會相撞。

While these models are inspired and guided by many scientific experiments,

每一次這類的碰撞的回響都可能會 出現在宇宙微波背景中——

there are very few objective experiments to directly test them, yet.

也就是從早期大爆炸時殘留下來， 遍及我們的整個宇宙中的輻射。

Until the next Edwin Hubble comes along,

不過，目前我們還沒有 找到這種宇宙回響。

scientists will likely be left to argue about the elegance of their competing models…

有些人懷疑 這些不同的多種宇宙假設

and continue to dream about what, if anything, lies beyond our universe.

最終可能會結合成一個共同假設，