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电子是波的真正含义

Electrons aren’t actual waves

You might have heard explanations of quantum mechanics that go like this:
你或许听过这样的量子力学解释
quantum objects can’t make up their minds,
“量子物体具有不确定性
sometimes they behave like particles: localized and small,
有时候它们表现为粒子特性——定域和微小
and sometimes they behave like waves: spreading out everywhere.
有些时候又表现为波的特性——四处传播”
But you should be careful not to take that statement too literally.
但你不应该仅从字面上来理解上述说法
To be clear, I’m not saying that the wave story of quantum mechanics is wrong.
明确一点 我不是说电子力学中波的特性这一说法是错的
It’s not, if you crack open a quantum mechanics textbook,
任意翻开一本关于量子力学的教材
you’ll see wave stuff all over.
你会发现到处都是关于波的内容
But when a physicist says an electron is acting like a wave,
但是当物理学家说电子表现得像波时
the actual meaning of this statement is quite subtle both mathematically and philosophically.
从数学和哲学的角度来看 这种说法非常微妙
Whereas when most people hear the statement: the electron is acting like a wave,
然而当大多数人听到“电子表现得像波”时
they of course imagine something much more concrete.
会不由自主地联想到一些更加具体的现象
That the object stops being in one localized spot,
例如 物质不会一直停留在局域的某一点上
and literally spreads out in space, and waves about.
而是会像波一样在空间中传播
I’m going to explain why this straightforward interpretation can’t be right.
下面我会解释为什么这种直接的字面理解是错误的
You’re not gonna have to take my word for it either, you’ll see it for yourself.
你也不必相信我所说的 大可以自己去体会
Let’s look at all of this in terms of the classic double slit experiment,
让我们从经典的双缝干涉实验中来理解
which is probably the context, in which you’ve heard the wave particle duality.
这一实验和你听过的波粒二象性相关
It’s an experiment where you have an electron coming in this side,
在这个实验中 电子首先从这一侧出发
then there are two slits that the electron can go through,
然后从前方的两个缝隙中通过
and finally it hits the back wall, where we mark where it lands.
最后到达实验屏 落在我们标记的位置上
Normally we’d imagine the electrons doing something like this,
通常我们会认为电子就是这样运动的
so that the electrons that make it through our all clumping up into spots.
因此 通过所有聚从的电子会集中为某一个点
But when we do the experiment, that’s not what we see.
但是当我们做实验时 发现结果并非如此
Instead, we see this pattern,
反而看到这样的图案
which looks kind of like a wave interference pattern.
这看起来像是波的干涉图样
The standard explanation says that in this experiment, the electrons act like waves.
关于双缝干涉实验的标准解释是电子表现得像波
The obvious way to interpret that is the material of the electron is made of,
关于这点 合理的解释是组成电子的粒子
physically spreads out in space, and half goes through each slit.
在空间经过物理扩散 一半进入狭缝之中
As in half the actual mass of the electron goes through this side, and half through the other.
进入狭缝之中的电子 一半通过这一侧 一半通过另一侧
Then these two waves can interfere with each other,
然后这两个波就可以进行相互干涉
and this interaction causes the interference pattern.
而这种相互作用就会产生干涉图样
Here’s the first problem though with thinking of the electrons as literal waves.
简单将电子看做波 便出现了第一个问题
If the electron is in fact spreading out like this,
如果电子真是以这样的方式传播
then where does it touch the back wall? In one spot?
那么电子究竟会在实验屏的哪里显示?会聚集在哪一点?
Not right, it’s smeared over the whole thing.
并不是 电子会分布在整个实验屏上
But that’s not at all what the data says,
但是实验结果并非如此
each electron turns up in just one spot on the wall.
每个电子只会出现在实验屏的某个点上
But there’s a way to explain that in the wave-particle duality story as well.
尽管如此 我们依然有办法来解释波粒二象性
The electron was a wave when it wasn’t being observed,
当电子未被测量时 它是一种波
but then when it gets observed, it becomes a particle again,
当电子被测量时 它又再次变成粒子
and therefore it shows up in just one spot on the wall.
所以电子仅在实验屏的某点出现
But think of what that would mean:
我们想想这意味着什么
the electron before it’s measured is spread out everywhere,
未被观测到时 电子向四处传播
but as soon as it’s at the wall,
一旦接触实验屏
it has to pick up its mass and pull it all back together.
它必须恢复它原有的粒群并且聚集在一起
Moving mass takes energy, where’s that energy gonna come from?
移动粒群需要能量 能量从何而来?
Not to mention other issues like,
更不要说其他问题了
if the electron has physically spread out far away the space,
如果电子已经在空间传播了一段距离
and it needs to pull back into the spot very quickly,
并且需要尽快返回到实验屏上的某点上
then this is potentially breaking speed-of-light constraints.
那么这很有可能会打破光速的限制
The point is the electron is not physically splitting up and spreading out,
问题的关键在于电子并没有分裂和四处扩散
but then what exactly is it doing?
那么电子到底是怎样运动的?
The theory of quantum mechanics is supposed to answer that question,
量子力学理论本应该回答这个问题
but it kind of doesn’t.
但并没有
The maths of quantum mechanics doesn’t talk about what the electron itself is doing at all.
量子力学数学没有涉及电子的运动问题
Instead, it talks about something called the wave function of the electron.
相反 它讲述的是关于电子的波函数问题
This is a mathematical function that spreads throughout space,
这是一个遍及整个空间的数学函数
and in this experiment happens to look very wave-like.
而在双缝干涉实验中 该函数碰巧呈波浪状
But it’s important to remember that the wave function isn’t the electron itself,
但是要记得波函数不是电子本身
and it’s not a physical wave.
也不是物质波
When a physicist says that an electron is acting like a wave in an experiment,
当物理学家说电子在实验中表现出波的特性时
what they mean is that the wave function looks wave-like.
实际上是说波函数呈波浪状
If you can calculate what the wave function of an electron is,
如果能计算出每个电子的波函数
then you can figure out where the electron is likely to turn up.
那你就能计算出电子可能在哪里出现
But what is the wave function? And how is it related to the electron at all?
但是什么是波函数?它和电子又有什么关联?
Does the electron just disappear when it’s not being measured?
电子在未被测量时是处于消失状态吗?
And only the wave function exists?
或者只有波函数的存在吗?
These questions that quantum mechanics doesn’t yet have the answer for,
关于量子力学的这些问题目前还没有确切答案
which is why this part of physics has so much philosophers debate around it.
这也是为什么有这么多哲学家会围绕量子力学进行辩论
We don’t fully understand what quantum mechanics is trying to say about how the world works.
我们还不完全了解 量子力学是如何解释世界运作的
Whatever it is, it’s not as simple as saying
无论其中的原理是什么 都不会像
that objects are sometimes acting like waves and sometimes like particles.
“物体有时表现得像波 有时表现得像粒子”这样简单
Hey, so thanks for watching.
感谢大家观看
I know I didn’t go into too much detail on things like
我在本视频中并没有深入讲解关于
the wave function and just quantum mechanics in general.
波函数的内容 只是大概讲解了一些关于量子力学的内容
But hopefully, I’ll be making more videos about that,
但我希望以后可以制作更多关于波函数的视频
and hopefully soon, if my PhD goes better this month than I did last.
并且是尽快 如果这个月的博士学位课程开展得比上个月顺利
We’ll see.
看情况吧

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视频概述

该视频是一个关于电子具有波粒二象性中“电子有时具有波的性质”的科普,作者提出了问题,提出了质疑,可惜的是也并未作出解释。作者后续可能会制作关于波函数的视频,敬请期待~

听录译者

www

翻译译者

YXG-e0359

审核员

审核员Y

视频来源

https://www.youtube.com/watch?v=XV46ALr3OMg

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