This rock?

這塊石頭？

That cow?

那頭牛？

Your heart?

你的心？

Not the things themselves, mind you, but what they're made of:

不是物體本身，你知道的， 而是組成物體的東西

the atoms that are the fabric of all things.

原子為萬物最小結構

To answer that question, we look to the law of conservation of mass.

要回答這個問題， 我們來看看質量守恒定律

This law says take an isolated system

這個定律的內容是： 找一個封閉系統

defined by a boundary that matter and energy cannot cross.

物質跟能量都不能通過其邊界

Inside this system, mass, a.k.a. matter and energy,

在這個系統中， 質量，也就是物質與能量

can neither be created nor destroyed.

不能被創造，也不能被毀滅

The universe, to the best of our knowledge,

宇宙，就我們所知

is an isolated system.

正是一個封閉的系統

But before we get to that, let's look at a much smaller and simpler one.

但談宇宙之前，咱們來看看 一個既小、又簡單得多的東西

Here we have six carbon atoms, 12 hydrogen atoms,

這裡有6個碳原子，12個氫原子

and 18 oxygen atoms.

以及18個氧原子

With a little energy, our molecules can really get moving.

若有些許能量存在， 分子會開始運動

These atoms can bond together to form familiar molecules.

這些原子可以結合在一起， 形成很熟悉的分子

Here's water,

那就是水分子

and here's carbon dioxide.

以及二氧化碳

We can't create or destroy mass.

我們不能創造或摧毀質量

We're stuck with what we've got, so what can we do?

我們得到的東西卡住我們了， 那我們能作什麼呢？

Ah, they have a mind of their own.

哈，他們有自己的主意

Let's see. They've formed more carbon dioxide and water, six of each.

瞧瞧！他們形成了更多的二氧化碳、水， 各有六個

Add a little energy, and we can get them to reshuffle themselves to a simple sugar,

添加一些能量，可使他們重新混合 變成一個單醣(葡萄糖)

and some oxygen gas.

以及一些氧氣

Our atoms are all accounted for: 6 carbon, 12 hydrogen, and 18 oxygen.

這些原子總共是： 6個碳，12個氫，18個氧

The energy we applied is now stored in the bonds between atoms.

我們提供的能量， 儲存在原子間的鍵結中

We can rerelease that energy

我們可以釋放能量

by breaking that sugar back into water and carbon dioxide,

藉由把單醣分解為 水和二氧化碳的方式

and still, same atoms.

還剩下一些原子

Let's put a few of our atoms aside and try something a little more explosive.

把一些原子放到一旁， 試試有點爆炸性的東西

This here is methane, most commonly associated with cow flatulence,

這是甲烷， 最常與牛胃部的脹氣聯想在一起

but also used for rocket fuel.

但也可用作火箭燃料

If we add some oxygen and a little bit of energy,

如果加上一些氧氣和少許能量

like you might get from a lit match,

就會像火柴一樣

it combusts into carbon dioxide, water and even more energy.

燃燒成為二氧化碳、水， 以及一些能量

Notice our methane started with four hydrogen,

注意，甲烷是從4個氫開始的

and at the end we still have four hydrogen captured in two water molecules.

而最終4個氫被2個水分子所捕捉

For a grand finale, here's propane, another combustible gas.

壓軸的是，丙烷， 另一個易燃氣體

We add oxygen, light it up, and boom.

我們添加一些氧氣，點火， 轟~

More water and carbon dioxide.

更多的水和二氧化碳

This time we get three CO2s

這次有3個二氧化碳

because the propane molecule started with three carbon atoms,

這是因為丙烷是由3個碳原子開始的

and they have nowhere else to go.

而他們無處可去

There are many other reactions we can model with this small set of atoms,

還有許多其他化學反應， 是可以用一些原子來模擬

and the law of conservation of mass always holds true.

而質量守恒定律總是真確的

Whatever matter and energy go into a chemical reaction

無論化學反應加了什麼物質與能量

are present and accounted for when it's complete.

反應完成時，都會存在且能被解釋

So if mass can't be created or destroyed,

所以，如果質量不能被創造或摧毀

where did these atoms come from in the first place?

最初，這些原子來自何方？

Let's turn back the clock and see.

咱們倒轉時間來看看

Further, further, further, too far.

倒轉，倒轉，倒轉，太多了

Okay, there it is.

就是這！

The Big Bang.

宇宙大爆炸

Our hydrogen formed from a high-energy soup of particles

氫原子從一團高能量的微粒而來

in the three minutes that followed the birth of our universe.

就在宇宙誕生後的三分鐘內

Eventually, clusters of atoms accumulated and formed stars.

最終，一團團的原子集結並且形成星體

Within these stars, nuclear reactions fused light elements,

在這些星體中，核反應熔合了輕的元素

such as hydrogen and helium,

例如氫和氦

to form heavier elements, such as carbon and oxygen.

形成較重的元素，例如碳和氧

At first glance, these reactions may look like they're breaking the law

乍看之下， 這些化學反應似乎違反定律

because they release an astounding amount of energy,

因為他們釋放驚人的能量

seemingly out of nowhere.

似乎是無中生有

However, thanks to Einstein's famous equation,

然而，謝謝愛因斯坦最有名的方程式

we know that energy is equivalent to mass.

我們知道能量正比於質量

It turns out that the total mass of the starting atoms

可解讀成初始原子的總質量

is very slightly more than the mass of the products,

略高於化學反應產物的質量

and that loss of mass perfectly corresponds to the gain in energy,

而這個質量的損失， 恰好等同於獲得的能量

which radiates out from the star as light, heat and energetic particles.

從星體發散出的光、熱、以及基本的微粒

Eventually, this star went supernova

最終，這個星體變成超新星

and scattered its elements across space.

它的元素散落在太空中

Long story short, they found each other and atoms from other supernovas,

長話短說，這些元素從其他超新星 找到了其他元素和原子

formed the Earth,

形成地球

and 4.6 billion years later got scooped up to play their parts

46億年後，這些微粒被挑選出來， 扮演自己的角色

in our little isolated system.

在我們小小的封閉系統中

But they're not nearly as interesting as the atoms that came together to form you,

但是， 他們並不如組成人體的原子那麼有趣

or that cow,

不如組成牛的原子

or this rock.

也不如組成這個石頭的原子

And that is why, as Carl Sagan famously told us,

這也是為何有名的卡爾薩根告訴我們 （美國天文學家、科幻、科普作家）

we are all made of star stuff.

我們全都是星塵作成的