What is the Heisenberg Uncertainty Principle? - Chad Orzel

什么是海森堡（德国物理学家）不定性原理？--查德 · 奥泽尔

翻译人员: Francis Ma 校对人员: Cindy Ma

The Heisenberg Uncertainty Principle is one of a handful of ideas

海森堡不确定性原理 是少数可以从量子物理领域

from quantum physics to expand into general pop culture.

拓展到普罗大众文化的物理原理之一。

It says that you can never simultaneously know the exact position

它指出人不能既知道一个物体的具体位置，

and the exact speed of an object and shows up as a metaphor in everything

又同时知道这个物体的运动速率。 它在各个领域被作为隐喻使用，

from literary criticism to sports commentary.

无论是从文艺评论，还是到体育评论中都有它的身影。

Uncertainty is often explained as a result of measurement,

不确定性常常被认为是测量时产生的，

that the act of measuring an object's position changes its speed, or vice versa.

因为对于一个物体位置的测定会改变该物体的速度， 反过来也是一样。

The real origin is much deeper and more amazing.

但是真正的原理要更加深奥，并且更加奇妙有趣

The Uncertainty Principle exists because everything in the universe

不确定性原理之所以存在 是因为宇宙中的任何东西

behaves like both a particle and a wave at the same time.

都同时表现出「粒子」和「波」的两种性质。

In quantum mechanics, the exact position and exact speed of an object

在量子力学中， 一个物体的确切位置和速度

have no meaning.

没有任何意义。

To understand this,

要理解这一点，

we need to think about what it means to behave like a particle or a wave.

我们需要知道表现的像「粒子」 或是像「波」究竟是什么意思。

Particles, by definition, exist in a single place at any instant in time.

粒子按照其解释，存在于任意瞬间的一个单独的空间里。

We can represent this by a graph showing the probability of finding

我们可以用像一张鞋钉一样的图案表现它，

the object at a particular place, which looks like a spike,

从中我们可以发现要在特定的空间里找到一个物体的概率。

100% at one specific position, and zero everywhere else.

在某一个特定地点，概率是 100%， 在别处则都是 0%。

Waves, on the other hand, are disturbances spread out in space,

而波则是「扰动」在空间中的传播，

like ripples covering the surface of a pond.

就像是湖面上荡起的涟漪。

We can clearly identify features of the wave pattern as a whole,

我们可以很容易的将「波」作为一个整体， 然后确立它的一些特性。

most importantly, its wavelength,

其中最重要的，就是波长。

which is the distance between two neighboring peaks,

波长是相邻两个波峰之间，

or two neighboring valleys.

或者两个相邻波谷之间的距离。

But we can't assign it a single position.

但是我们并不能给他分配一个特定的位置。

波有很大概率处于各种不同的位置。

It has a good probability of being in lots of different places.

Wavelength is essential for quantum physics

波长是量子物理的基础。

because an object's wavelength is related to its momentum,

因为一 个物体的波长 和它的动量是息息相关的：

mass times velocity.

动量 = 质量乘以速度。

A fast-moving object has lots of momentum,

一个快速运动的物体有很大的动量，

which corresponds to a very short wavelength.

所以波长也就很短。

一个很重的物体本身具有很大的动量， 即使它并没有快速运动。

A heavy object has lots of momentum even if it's not moving very fast,

which again means a very short wavelength.

同样的，也代表了它的波长很短，

这也是为什么我们观察不到 日常用品的波的性质的原因。

This is why we don't notice the wave nature of everyday objects.

If you toss a baseball up in the air,

如果你将一个棒球投掷于空中，

its wavelength is a billionth of a trillionth of a trillionth of a meter,

它的波长是一米的亿分之万亿分之万亿分之一。

far too tiny to ever detect.

实在是太小了，基本不可能检测到。

Small things, like atoms or electrons though,

然而，更小的物质 比如说原子或者电子，

can have wavelengths big enough to measure in physics experiments.

则有一个足够大的 能在物理实验中测量出的波长。

So, if we have a pure wave, we can measure its wavelength,

所以如果我们有一个纯粹的波， 我们就能测量它的波长，

and thus its momentum, but it has no position.

从而得到它的动量。 但是却得不到它的位置。

我们可以很容易知道一个粒子的位置，

We can know a particles position very well,

but it doesn't have a wavelength, so we don't know its momentum.

但它却并没有波长， 所以我们也不知道它的动量。

To get a particle with both position and momentum,

为了同时得到一个粒子的位置和动量，

we need to mix the two pictures

我们需要融合两个图像。

to make a graph that has waves, but only in a small area.

来创造一个有波的图， 然而尽在很小的区域里。

How can we do this?

我们如何来做呢？

By combining waves with different wavelengths,

通过将不同波长的波进行融合。

which means giving our quantum object some possibility of having different momenta.

这就意味着我们的量子物体 具有不同动量的可能性。

When we add two waves, we find that there are places

当我们让两个波相加时， 我们发现有些地方

where the peaks line up, making a bigger wave,

两个波的波峰对齐 并且组成了一个更大的波。

然而在另外一些地方，一个波的波峰 却叠到了另一个的波谷里。

and other places where the peaks of one fill in the valleys of the other.

The result has regions where we see waves

结果就是有些地方我们看得到波，

separated by regions of nothing at all.

另一些地方，则什么都没有。

If we add a third wave,

如果我们再加上第三个波，

the regions where the waves cancel out get bigger,

那些波被消减的区域就变大了。

a fourth and they get bigger still, with the wavier regions becoming narrower.

加上第四个，依旧变大， 但波的区域逐渐变窄。

If we keep adding waves, we can make a wave packet

如果我们持续添加更多的波， 我们能得到一个波包：

with a clear wavelength in one small region.

在一个很小的区域里 有一个确定的波长。

That's a quantum object with both wave and particle nature,

这就得到了一个同时拥有波的属性 和粒子的属性的量子物体。

but to accomplish this, we had to lose certainty

但是为了完成这一点， 我们得到的位置和动量

about both position and momentum.

就都不具备确定性了。

The positions isn't restricted to a single point.

而且它们位置并非规定在一个单独的点上。

There's a good probability of finding it within some range

我们有很高的概率 在波包内的范围里

of the center of the wave packet,

的任何地方找到它。

and we made the wave packet by adding lots of waves,

我们通过多个波相加的办法 得到了这个波包，

which means there's some probability of finding it

于是我们就有可能找到 其中一个位置的量子物体，

with the momentum corresponding to any one of those.

拥有与之相应的动量。

Both position and momentum are now uncertain,

所以位置和动量现在就都是不确定的了。

and the uncertainties are connected.

并且这种不确定性是相关联的。

If you want to reduce the position uncertainty

如果你想降低位置的不确定性，

by making a smaller wave packet, you need to add more waves,

就得用更多的波相加， 构造一个更小的波包，

which means a bigger momentum uncertainty.

从而导致了一个更大的动量不确定性。

If you want to know the momentum better, you need a bigger wave packet,

如果你想更明确的得到动量值， 就需要一个更大的波包，

which means a bigger position uncertainty.

这样就导致了更大的位置的不确定性。

That's the Heisenberg Uncertainty Principle,

这就是海森堡不确定性原理。

first stated by German physicist Werner Heisenberg back in 1927.

最初被德国物理学家 Werner Heisenberg 早在 1927 年提出。

This uncertainty isn't a matter of measuring well or badly,

这种不确定性和测量的好与坏无关，

but an inevitable result of combining particle and wave nature.

是一种结合波和粒子 两种性质之后的不可避免的结果。

The Uncertainty Principle isn't just a practical limit on measurment.

不确定性并不仅仅是 测量上的实际限制，

It's a limit on what properties an object can have,

它是一种对于物体只能有一种性质的限制，

built into the fundamental structure of the universe itself.

并建立在宇宙本身的基本构成之上。