Just How Small is an Atom?

Just How Small is an Atom?

翻译人员: Li Huayang 校对人员: Xiaoou Chen

（音乐）

你也许已经知道所有的东西

You probably already know

everything is made up of little tiny things called atoms

都是由微小的原子组成。

or even that each atom is made up of even smaller particles

你可能还知道每一个原子是由更小的

叫做质子，中子和电子的微粒组成

called protons, neutrons and electrons.

And you've probably heard that atoms are small.

也许你听说过原子很小。

But I bet you haven't ever thought about how small atoms really are.

我打赌，你从未想过它究竟有多小。

答案是，它们非常非常非常小。

Well, the answer is that they are really, really small.

So you ask, just how small are atoms?

你提出问题了，到底原字有多小呢?

To understand this, let's ask this question:

为了去理解它，让我们先提出一个问题：

一个柚子包含多少原子？

How many atoms are in a grapefruit?

Well, let's assume that the grapefruit is made up of only nitrogen atoms,

首先我们假设柚子完全由氮原子构成，

虽然不准确，但柚子中确实有氮原子。

which isn't at all true, but there are nitrogen atoms in a grapefruit.

To help you visualize this, let's blow up each of the atoms

为了便于观察，我们把原子放大到

to the size of a blueberry.

一个蓝莓大小。

And then how big would the grapefruit have to be?

那总体柚子又会是多大呢？

It would have to be the same size of -- well, actually, the Earth.

它会跟地球的个头差不多。

That's crazy!

天啊！难道地球装满蓝莓的数量

You mean to say that if I filled the Earth with blueberries,

I would have the same number of nitrogen atoms as a grapefruit?

会和柚子中的氮原子一样多？

That's right!

的确如此！那么原子究竟有多小？

So how big is the atom?

它小到

Well, it's really, really small!

超出了你的

And you know what? It gets even more crazy.

想象。

Let's now look inside of each atom -- and thus the blueberry, right? --

现在让我们看看原子内部，也就是蓝莓。

What do you see there?

你会发现

In the center of the atom is something called the nucleus,

原子有一个核心。

which contains protons and neutrons,

其中包含着质子和中子，

and on the outside, you'd see electrons.

外围的是电子。

So how big is the nucleus?

如果原子是地球中的蓝莓，

If atoms are like blueberries in the Earth,

那么原子核又有多大呢？

how big would the nucleus be?

你可能在物理书上看过原子的描绘，

You might remember the old pictures of the atom from science class,

原子核是箭头所指的小点。

where you saw this tiny dot on the page with an arrow pointing to the nucleus.

这些图不是按比例画的，

Well, those pictures, they're not drawn to scale,

so they're kind of wrong.

所以并不准确。

那么真实的原子核多大呢？

So how big is the nucleus?

如果你在蓝莓的内部

So if you popped open the blueberry and were searching for the nucleus ...

搜索原子核，

结果是一无所获。

You know what? It would be invisible.

It's too small to see!

因为我们看不到它！

OK. Let's blow up the atom -- the blueberry --

如果我们把原子，也就是蓝莓

to the size of a house.

放大到房子的尺寸。

So imagine a ball that is as tall as a two-story house.

想象下有两层房屋那么高。

Let's look for the nucleus in the center of the atom.

我们在其中寻找原子核，

And do you know what? It would just barely be visible.

它就如一粒尘埃。

所以想要真正看清原子核，

So to get our minds wrapped around how big the nucleus is,

we need to blow up the blueberry, up to the size of a football stadium.

还要把蓝莓放大到橄榄球场大小。

So imagine a ball the size of a football stadium,

想象一下，橄榄球场大小的原子。

and right smack dab in the center of the atom,

在它的正中间，

you would find the nucleus, and you could see it!

你终于找到了原子核！

而它只有玻璃弹子大小。

And it would be the size of a small marble.

如果现在你都没有被震撼到，

And there's more, if I haven't blown your mind by now.

Let's consider the atom some more.

那再来设想下原子中的质子，中子，电子。

It contains protons, neutrons and electrons.

The protons and neutrons live inside of the nucleus,

质子和中子组成了原子核，

几乎占了原子全部比重。

and contain almost all of the mass of the atom.

在原子边缘的是电子。

Way on the edge are the electrons.

So if an atom is like a ball the size of a football stadium,

一个橄榄球场大小的原子，

with the nucleus in the center, and the electrons on the edge,

原子核在中心，而电子在边缘，

what is in between the nucleus and the electrons?

那么两者之间又是什么呢？

虚空。

Surprisingly, the answer is empty space.

（风声）

(Wind noise)

没错，空无一物！

That's right. Empty!

Between the nucleus and the electrons, there are vast regions of empty space.

在原子核和电子之间存在着大片空洞区域。

严格的说来还有电磁场，

Now, technically there are some electromagnetic fields,

but in terms of stuff, matter, it is empty.

但从物质的角度看，还是空洞。

Remember this vast region of empty space is inside the blueberry,

而这空洞区域正是在

蓝莓之中，而蓝莓又是在

which is inside the Earth,

如地球大小的柚子之中。

which really are the atoms in the grapefruit.

OK, one more thing, if I can even get more bizarre.

更奇异的是，

Since virtually all the mass of an atom is in the nucleus --

事实上原子的大部分质量集中在原子核，

虽然电子也有一定质量，

now, there is some amount of mass in the electrons,

但是可以忽略。

but most of it is in the nucleus --

那么原子核的密度是多少？

how dense is the nucleus?

Well, the answer is crazy.

你会觉得不可思议。

The density of a typical nucleus

典型的原子的密度是

is four times 10 to the 17th kilograms per meter cubed.

4乘以10的17次方千克/立方米。

But that's hard to visualize. OK, I'll put it in English units.

很难设想，那么换作英制单位是

2.5 times 10 to the 16th pounds per cubic feet.

2.5乘以10的16次方

磅/立方英尺。

OK, that's still kind of hard to figure.

如果还是很难想象，

OK, here's what I want you to do.

那么打个比方。

Make a box that is one foot by one foot by one foot.

一个30厘米立方的盒子，

一辆重两吨的汽车，

Now let's go and grab all of the nuclei from a typical car.

我们需要多少量汽车的原子核

Now, cars on average weigh two tons.

How many cars' nuclei would you have to put into the box

装在一个盒子里

才能达到一个原子核的密度？

to have your one-foot-box have the same density of the nucleus?

一辆，两辆，还是一百辆？

Is it one car? Two?

How about 100?

都不是。

Nope, nope and nope.

The answer is much bigger.

结果大得多。

It is 6.2 billion.

需要62亿辆。

这差不多是世界人口总数。

That is almost equal to the number of people in the Earth.

所以如果每个人都拥有一辆车，

So if everyone in the Earth owned their own car --

and they don't --

我们假象，

(Cars honking)

把这些车都装进盒子里，

and we put all of those cars into your box ...

就差不多相当于一个原子核的密度。

That would be about the density of a nucleus.

把世界上每一辆车都装进一30厘米立方的盒子中，

So I'm saying that if you took every car in the world

and put it into your one-foot box,

你才得到原子核的密度。

you would have the density of one nucleus.

我们回顾一下。

OK, let's review.

The atom is really,

原子极其渺小。

really, really small.

柚子中的原子是地球中的蓝莓。

Think atoms in a grapefruit like blueberries in the Earth.

原子核更是出奇的小。

The nucleus is crazy small.

把蓝莓放到大橄榄球场大小，

Now look inside the blueberry,

and blow it up to the size of a football stadium,

原子核就是其中的玻璃弹子。

and now the nucleus is a marble in the middle.

原子内存在广阔的虚空。

The atom is made up of vast regions of empty space.

很不寻常。

That's weird.

The nucleus has a crazy-high density.

原子核有极高的密度。

Think of putting all those cars in your one-foot box.

想想盒子里装的那些车。

我洗洗睡了。

I think I'm tired.

（打哈欠）