You might even know that each atom is made up of even smaller particles called protons, neutrons and electrons. 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

　　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. 但我打赌，你从未想过它究竟有多小。

　　Well, the answer is that they are really, really, really small. 答案是，它们非常非常非常小。

　　So you ask, just how small are atoms? 你提出问题了，到底原子有多小呢?

　　To understand this, let's ask this question: How many atoms are in a grapefruit? 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？

　　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，

　　which isn't at all true, but there are nitrogen atoms in a grapefruit.  虽然不准确，但柚子中确实有氮原子。

　　Well, to help you visualize this, let's blow up each of the atoms to the size of a blueberry. 为了便于观察，我们把原子放大到一个蓝莓大小。

　　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! You mean to say that if I filled the Earth with blueberries, 天啊！难道地球装满蓝莓的数量

　　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! So how big is the atom? 的确如此！那么原子究竟有多小？

　　Well, it's really, really small! And you know what? It gets even more crazy.  它真的非常非常小，小到超出了你的想象。

　　Let's now look inside of each atom -- and thus the blueberry, right? What do you see there? 现在让我们看看原子内部，也就是蓝莓。你看到了什么？

　　In the center of the atom is something called the nucleus, 你会发现原子有一个核心，叫原子核。

　　which contains protons and neutrons, and on the outside, you'd see electrons. So how big is the nucleus?  其中包含着质子和中子，外围的是电子。那么原子核有多大？

　　Well, if atoms are like blueberries in the Earth, how big would the nucleus be? 如果原子是地球中的蓝莓，那么原子核又有多大呢？

　　You might remember the old pictures of the atom from science class, 你可能在物理书上看过原子的描绘，

　　where you saw this tiny dot on the page with an arrow pointing to the nucleus. 原子核是箭头所指的小点。

　　Well, those pictures, they're not drawn to scale, so they're kind of wrong. 这些图不是按比例画的，所以并不准确。

　　So how big is the nucleus? 那么真实的原子核多大呢？