Where does all this stuff come from?
所有这些东西都是从哪来的？
This rock? That cow? Your heart?
这块石头？那只牛？你的心脏？
Not the things themselves, mind you, but what they're made of: the atoms that are the fabric of all things.
提醒一下，不是这些东西本身而是它们的构成：原子组成了所有的物质。
To answer that question, we look to the law of conservation of mass.
要回答那个问题，我们得指望质量守恒定律了。
This law says take an isolated system defined by a boundary that matter and energy cannot cross.
这个定律说的是一个孤立系统被物质与能量都无法穿越的边界所定义。
Inside this system, mass, a.k.a. matter and energy, can neither be created nor destroyed.
在这个系统中，质量，也叫做物质和能量，既不能被产生，也无法被摧毁。
The universe, to the best of our knowledge, is an isolated system.
这个宇宙，尽我们所知，就是这样一个孤立系统。
But before we get to that, let's look at a much smaller and simpler one.
但是在分析它之前，我们先来看一个更小和更简单的系统。
Here we have six carbon atoms, 12 hydrogen atoms, and 18 oxygen atoms.
在这里，我们有六个碳原子，十二个氢原子，还有十八个氧原子。
With a little energy, our molecules can really get moving.
只要有一点能量，我们的分子就可以开始移动了。
These atoms can bond together to form familiar molecules.
这些原子可以结合在一起组成我们所熟悉的分子。
Here's water, and here's carbon dioxide.
这是水，这是二氧化碳。
We can't create or destroy mass.
我们无法创造或是摧毁质量。
We're stuck with what we've got, so what can we do?
我们受限于我们所拥有的，所以我们能做什么呢？
Ah, they have a mind of their own.
啊，它们有自己的想法。
Let's see. They've formed more carbon dioxide and water, six of each.
我们来看。它们组成了更多的二氧化碳和水，各有六个。
Add a little energy, and we can get them to reshuffle themselves to a simple sugar, and some oxygen gas.
加一点能量，我们就可以让它们重新组成一个简单的糖，还有一些氧气。
Our atoms are all accounted for: 6 carbon, 12 hydrogen, and 18 oxygen.
所用到的所有原子就是那6个碳，12个氢，还有18个氧。
The energy we applied is now stored in the bonds between atoms.
我们所用的能量现在被储存于原子间的化学键中了。
We can rerelease that energy by breaking that sugar back into water and carbon dioxide, and still, same atoms.
我们可以通过将那糖还原为水与二氧化碳来释放能量，而原子依然是同样的。
Let's put a few of our atoms aside and try something a little more explosive.
现在，让我们先撇开一些原子，尝试一些更加有趣的事情。

This here is methane, most commonly associated with cow flatulence, but also used for rocket fuel.
这个是甲烷，一般与牛的胃肠气胀有关，但同时也用作火箭燃料。
If we add some oxygen and a little bit of energy, like you might get from a lit match,
如果我们加一些氧和一点能量，就像你从一根点亮的火柴上获得的那样，
it combusts into carbon dioxide, water and even more energy.
它燃烧变成了二氧化碳、水甚至还有能量。
Notice our methane started with four hydrogen,
注意我们的甲烷刚开始有四个氢，
and at the end we still have four hydrogen captured in two water molecules.
到了最后我们仍旧还有四个氢，被两个水分子所携带。
For a grand finale, here's propane, another combustible gas.
最后来一个厉害的，这是丙烷，另一种可燃气体。
We add oxygen, light it up, and boom. More water and carbon dioxide.
我们加入氧气，点燃，然后，嘣！再加更多的水和二氧化碳。
This time we get three CO2s because the propane molecule started with three carbon atoms, and they have nowhere else to go.
这次我们得到了三个CO2，因为丙烷分子开始就有三个碳原子，它们无处可走。
There are many other reactions we can model with this small set of atoms,
还有很多其他的反应我们可以用这一小组原子来模拟，
and the law of conservation of mass always holds true.
而质量守恒定律永远成立。
Whatever matter and energy go into a chemical reaction are present and accounted for when it's complete.
任何物质和能量经过一个化学反应，依然还会存在并呈现。
So if mass can't be created or destroyed, where did these atoms come from in the first place?
所以，如果质量既不能被创造也无法被毁灭，那么这些原子最初都是从哪来的呢？
Let's turn back the clock and see.
让我们回调时钟来看。
Further, further, further, too far. Okay, there it is. The Big Bang.
远一点，再远一点，再远一点，太远了。好了，就是这了。宇宙大爆炸。
Our hydrogen formed from a high-energy soup of particles in the three minutes that followed the birth of our universe.
在宇宙出生后的三分钟内，我们的氢从一组高能量的微粒中生成。
Eventually, clusters of atoms accumulated and formed stars.
最终，一团团的原子积累并构成了星体。
Within these stars, nuclear reactions fused light elements, such as hydrogen and helium,
在这些星体内，核反应会融合轻的元素，像是氢和氦，
to form heavier elements, such as carbon and oxygen.
去组成更重的元素，像是碳和氧。
At first glance, these reactions may look like they're breaking the law
乍看之下，这些反应似乎像是违反了质量守恒定律，
because they release an astounding amount of energy, seemingly out of nowhere.
因为它们释放一堆似乎不知道从哪里来的惊人的能量。
However, thanks to Einstein's famous equation, we know that energy is equivalent to mass.
不过，幸好有了爱因斯坦著名的公式，我们知道了能量是等同于质量的。
It turns out that the total mass of the starting atoms is very slightly more than the mass of the products,
结果就使得原始原子的总质量比生成物的质量稍稍多一点，
and that loss of mass perfectly corresponds to the gain in energy,
失去的质量与获得的能量完美吻合，
which radiates out from the star as light, heat and energetic particles.
以光、热还有能量粒子的形式传播出去。
Eventually, this star went supernova and scattered its elements across space.
最终，这个星体变成了超新星，将自己的元素散布到宇宙空间。
Long story short, they found each other and atoms from other supernovas, formed the Earth,
长话短说，它们找到了彼此，并和来自其他超新星的原子一起组成了地球，
and 4.6 billion years later got scooped up to play their parts in our little isolated system.
46亿年后，在我们这个小小的孤立系统中扮演起自己的角色。
But they're not nearly as interesting as the atoms that came together to form you, or that cow, or this rock.
但是它们一点都不如一起组成你，或那只牛，或这块石头的原子们那般有趣。
And that is why, as Carl Sagan famously told us, we are all made of star stuff.
这也就是为什么就像卡尔·萨根那句名言所述，“我们都是由星际物质组成的”。