英语听力文摘 English Digest 723 我们为何不能穿墙？

Why We Can’t Walk Through Walls

Shadowcat! She’s one of the X-Men, and she can walk through walls!

Unfortunately, however, Shadowcat can’t be real. This is because she violates a basic law of physics that says two things can’t share the same space.

But aren’t atoms mostly empty space? Couldn’t she just slip into that space? Unfortunately, no.

It’s true that atoms are mostly empty space. (If a helium atom were the size of the earth, the electrons would be out in earth’s atmosphere, and the protons and neutrons¹ would be the size of a basketball at the core.) But atoms can’t overlap² because only a limited amount of electrons can be in the same orbit.

The reason for this is what’s called the Pauli Exclusion³ Principle. Electrons have ‘spin’. Picture a screw. Its threads go in one direction, right? So imagine the screw turning in the direction of its threads, like how it screws into a board. Now picture placing two screws side by side, but pointing in opposite directions. Their spins are the reverse of the other, and you can get them close together.

But the Pauli Exclusion Principle only applies to particles like the ones in atoms. There are other types of particles, such as the ones that make up light, which can be in the same place at the same time.

 

1 neutrons   

n.中子( neutron的名词复数 )

参考例句：

• The neutrons and protons form the core of the atom. 中子和质子构成了原子核。 来自《简明英汉词典》
• When an atom of U235 is split,several neutrons are set free. 一个铀235原子分裂时，释放出几个中子。 来自《简明英汉词典》

2 overlap   

v.重叠，与…交叠；n.重叠

参考例句：

• The overlap between the jacket and the trousers is not good.夹克和裤子重叠的部分不好看。
• Tiles overlap each other.屋瓦相互叠盖。

3 exclusion   

n.拒绝，排除，排斥，远足，远途旅行

参考例句：

• Don't revise a few topics to the exclusion of all others.不要修改少数论题以致排除所有其他的。
• He plays golf to the exclusion of all other sports.他专打高尔夫球，其他运动一概不参加。