3 Mysteries of the Universe — and a New Force That Might Explain Them | Alex Keshavarzi | TED

翻译人员: Jinnie Sun 校对人员: Yanyan Hong

So today, I’m really here to talk to you all about one thing:

所以今天， 我真的只想和大家谈一件事：

the universe.

宇宙。

In the world of particle physics,

在粒子物理学的世界中，

the ultimate goal is to be able to describe

终极目标是能够描述

all the particles and forces that make up our universe.

构成我们宇宙的所有粒子和力。

And while we've made an extraordinary amount of progress in this

尽管在过去的 100 年中， 我们在这方面

over the past 100 years,

取得了非凡的进步，

we're doing it still,

我们仍在继续，

because there are big mysteries about what the universe is made of

因为仍然有巨大的谜团， 关于宇宙是由什么组成的，

and how we came to be here.

我们又是如何来到这里的。

So let me start by introducing you

所以请让我首先向你们介绍

to three of the big mysteries about our universe.

有关我们宇宙的三个大谜团。

First, we know that the universe is expanding.

首先，我们知道宇宙正在膨胀。

So astrophysical evidence suggests

有天体物理学证据表明，

that the universe started as a very dense, very hot Big Bang,

宇宙从一个非常密集、非常炎热的 宇宙大爆炸起始，

and has since been expanding outwards from that point.

从那时起它一直在向外扩张。

However, as a complete shock, in the late '90s,

但是，令人震惊的是， 在 90 年代后期，

physicists discovered that the expansion of the universe

物理学家发现宇宙的膨胀

isn't slowing down, as you might expect --

并没有那样减速，像你可能预期的那样，

it's actually accelerating,

它实际上在加速，

and we have absolutely no idea as to why this is.

而我们完全不明白为什么会这样。

All that we know is that some unknown source or force of nature

我们所知道的只是， 某种未知的自然的来源或力量

is stretching the universe out in every direction,

正在沿各个方向延展宇宙，

at an ever-increasing rate.

以不断加快的速度。

And because we don't know what that source is,

因为我们不知道那个来源是什么，

we've just called it "dark energy."

所以我们只是称之为“暗能量”。

Now, what we do know about dark energy

现在，我们对暗能量的了解是，

is that it makes up roughly 74 percent of the energy content of our universe.

它约占宇宙总能量的 74 ％。

So straight off the bat,

所以说，

that's 74 percent of our universe that we know absolutely nothing about.

我们竟对 74% 的宇宙一无所知。

Second, we know that 85 percent of all the matter in our universe

第二，我们知道宇宙中 85 ％的物质

is made up of something called dark matter.

是由一种叫做暗物质的东西组成的。

Now, this photo that you're looking at here

现在，你在这里看到的这张照片

is a picture from the Hubble Space Telescope,

是哈勃太空望远镜拍摄的一张照片，

which shows a cluster of galaxies

它展示了一个星系团，

four billion light years away from the Earth.

这个星系团距离地球 40 亿光年。

And what's interesting here

这张照片有趣的是

is the left and right parts of this photograph,

它的左右部分，

because they're actually the same photo.

因为它们实际上是同一张照片。

But what you're looking at in the right photo

但是你在右边的照片中看到的是

is that it's had a blue filter applied to it,

它使用了一个蓝色滤镜，

to emphasize the light that's coming towards us

以强调这些射向我们的光线

from the distant universe.

是来自遥远的宇宙的。

And what you can see is a dark ring,

而你能看到的是一个暗颜色的环，

indicating a clearly reduced amount of light coming towards us.

表明射向我们的光明显减少了。

Now we believe that this ring is a halo of dark matter.

现在我们认为这个环是暗物质光环。

Now we have no idea what dark matter is,

现在我们还不知道什么是暗物质，

and we've never observed it in experiments here on Earth,

也从未在地球上的实验中 观测到过暗物质，

but we know from several corroborating astrophysical observations

但是从几次确凿的天体物理学观测中 我们可以得出

that it has to be there.

暗物质肯定存在。

Importantly, another thing that we know about dark matter

重要地， 关于暗物质我们了解的另一件事是，

is that it makes up another 21 percent of the energy content of our universe.

它占宇宙能量的另外 21 ％。

So that, coupled with the dark energy problem,

所以，再加上暗能量的问题，

means that we only know what five percent of our universe is made of,

这意味着我们只知道 宇宙的 5 %是由什么构成的，

and the rest is totally dark to us.

而其余对我们来说完全是黑暗的。

The third problem concerns how we've come to exist at all.

第三个问题关系到 我们究竟是如何存在的。

Now, fundamental particles of matter have their own antimatter particles,

现在，物质的基本粒子 有自己的反物质粒子，

which are the same as their normal matter counterparts,

它们与普通的物质粒子相同，

except they have opposite positive or negative charge,

唯一的不同是它们具有相反的 正或负电荷，

just like the two ends of a normal, everyday battery.

就像一节普通的电池的两端一样。

Now together, this charge is equal and balanced.

加起来，这些电荷是相等且平衡的。

The electron, for example,

例如，电子，

which we're a bit more familiar with -- it gives us electricity in our homes --

我们都更熟悉的电子—— 在家里它为我们提供电力——

is negatively charged.

带负电荷。

But it has an antimatter partner called the positron,

但是它有一个 叫做正电子的反物质伙伴，

which is positively charged.

这个正电子带正电荷。

Now to ensure this balance,

现在，为了确保这种平衡，

matter and antimatter are always created and destroyed equally and in pairs.

物质和反物质总是同等地、成对地 被创造或摧毁。

This is what all of our theories predict,

这是我们所有的理论所预测的，

and this is what we observe in all of our experiments.

也是我们在所有实验中所观察到的。

And so in the Big Bang,

因此，在宇宙大爆炸中，

we would [have] expected that matter and antimatter

我们估计物质和反物质

would have been created in equal amounts,

产生的量是相同的，

and so we would expect to see equal amounts of matter and antimatter

所以我们也预计在现在的宇宙中

in the universe today.

物质和反物质的量也相等。

However, nearly every structure of matter,

但是， 我们宇宙中几乎每一种物质结构，

every natural structure of matter in our universe --

物质的每种自然结构——

you, me, the Earth, the stars --

包括你、我、地球、恒星——

are made almost entirely of normal matter,

几乎全都是由普通物质构成的，

leaving a lot of antimatter missing from the balanced equation.

导致我们建构的平衡方程中 缺少了很多反物质。

For all you Marvel and Avengers fans out there,

对于你们中 漫威和复仇者联盟的粉丝来说，

it's a bit like someone's just snapped their fingers,

这有点像某个人只是打了个响指，

and half of all the natural stuff in the universe has disappeared.

接着宇宙中所有的、自然的东西 一半都消失了。

There literally should be

所以真的，

another universe's worth of stuff all around us,

我们周围应该存在着 相当于另一个宇宙的东西，

but somehow, it's not there.

但不知何故，它并不在。

And one of the greatest challenges in particle physics today

当今粒子物理学最大的挑战之一

is to figure out what happened to all the antimatter

是弄清楚所有的反物质是怎么回事，

and why we see an asymmetry between matter and antimatter at all.

以及为什么我们在物质和反物质之间 会看到这种不对称性。

So those are three of the big mysteries about our universe.

因此， 这是关于我们宇宙的三个大谜团。

And that's a lot of what we don't know.

而我们还有很多不知道的东西。

Now, what this means

这意味着

is our current understanding of the universe, up until this point,

我们现在对宇宙的理解，到目前为止，

can't tell us why the universe is the way it is,

还无法告诉我们 为什么宇宙是它现在的样子，

or what 95 percent of it is made of.

也无法告诉我们宇宙 95% 的部分 是由什么组成的。

But importantly, each of these mysteries --

但重要的是， 所有这些谜团——

what is dark energy, what is dark matter

什么是暗能量，什么是暗物质

and the matter-antimatter asymmetry in the universe --

以及宇宙中 物质-反物质的不对称性——

could all be solved by finding a new particle

都可以通过寻找一种新的粒子

or a new force of nature.

或新的自然力量来解开。

So now, let me introduce you

因此，现在，让我向你们介绍

to our current understanding of the universe.

我们目前对宇宙的理解。

This is it.

就是这个。

The standard model of particle physics,

粒子物理学的标准模型，

the mathematical equation, which I’m sure you’re all very used to.

数学方程， 这些我相信你们都已经很习惯了。

(Laughter)

（笑声）

Which describes how our universe works.

它描述了我们的宇宙是如何运作的。

You can think of it as the recipe

你可以把它看作一个配方，

for how all the particles and forces in the universe

描述宇宙中所有粒子和力量

interact and result in the structures of matter

如何相互作用， 以形成那些物质结构，

that we see around us.

在我们周围看得到的物质。

Now this equation represents a huge level of achievement

现在，这个方程代表了一个巨大成就，

over the past 100 years,

在过去 100 年内的成就，

and in its full form, it's much longer, but simplified,

其完整形式要长得多，但简化后，

like this,

像这样，

you see a very elegant, I think,

我想，你能看到一个非常优雅的，

elegant representation of the structure of matter.

优雅的对物质结构的描述方式。

And then, if that equation is the recipe,

然后，如果这个方程是配方，

then these are the ingredients.

那么这些就是原料。

Just 17 ingredients, 17 fundamental particles,

只有 17 种原料， 17 种基本粒子，

where "fundamental" here means they're not known to have a substructure,

这里“基本”的意思是 我们目前没发现它们有子结构，

they're not known to be composed of any smaller particles.

也没发现它们是由 任何更小的粒子组成的。

And together with the equation on the previous slide,

与上一张幻灯片上的等式一起，

they make up the standard model of particle physics.

它们构成了粒子物理学的标准模型。

And it is our best, most tested and globally accepted theory

并且它是我们最好的、测试过最多次的、 全球接受度最高的理论，

of all the known particles and forces in the universe.

关于宇宙中所有已知粒子和力的理论。

And it's given rise to much of what we take for granted

并且它催生了许多 我们现在认为理所当然的事情，

in the modern world of today.

在当今的现代世界中。

A good example would be our ability now to harness the energy from the Sun,

一个很好的例子是我们现在 能够利用来自太阳的能量，

where our ability to use solar power and our moves towards nuclear fusion

我们使用太阳能的能力， 以及核聚变的发展

couldn't be possible

都无法实现，

without understanding the particles and forces of the standard model.

要是没有理解 标准模型中的粒子和力的话。

Now, whilst the standard model has been so successful

现在，尽管标准模型成功地

at testing the phenomena that we can test here on Earth,

吻合了我们可以在地球上测试的现象，

it cannot accommodate and has no explanation for

但它无法容纳也无法解释

those big mysteries about our universe.

那些关于我们宇宙的大谜团。

And so it's at this point that I'd like to introduce you

所以，现在我想要想你们介绍

to a particular particle,

一种特别的粒子，

and the hero of our story, the muon.

它也是我们故事的主人公，μ子。

Now, muons may seem unfamiliar to you all,

现在，大家似乎都不熟悉μ子，

but actually, they’re around us all the time.

但实际上，它们一直都在我们身边。

Cosmic rays that hit the Earth's atmosphere

撞击地球大气层的宇宙射线

result in showers of muons that constantly bombard the Earth.

会产生不断轰击地球的μ子阵雨。

You may be surprised to learn, for example,

例如，你可能会惊讶地发现，

that there are, on average, 30 muons

平均每秒有 30 个μ子

traveling through each and every one of you every second.

穿过你们每一个人。

Now, muons can be thought of, quite simply,

现在，可以简单地将μ子视作

as the heavy cousin of the electron,

电子胖壮的表弟，

and they sit next to the electron in this picture,

在这张照片中， 它们就坐在电子旁边，

and they're about 200 times heavier.

而它们比电子重约 200 倍。

But importantly, they’re an ideal tool for physicists to use

但重要的是， 它们是物理学家的理想工具，

to search and look for new particles and forces

以搜索寻找新的粒子和力量。

to explain those big mysteries.

以解释那些巨大谜团。

And so why is that?

那么这是为什么呢？

Well, let's assume for a second that we can represent a muon

让我们暂时假设我们可以用这个陀螺仪

by this gyroscope.

代表μ子。

When you spin a gyroscope,

当你旋转陀螺仪时，

it wobbles around its axis, just like that.

它会围绕轴线摆动， 就像这样。

And muons have an identical behavior

而μ子具有相同的行为，

when you place them in a magnetic field, they spin and they wobble.

当你将μ子置于磁场中时， 它们会旋转，会摆动。

Now whilst they're doing this,

现在，当它们这样做时，

the muon will come into contact

μ子将与

with any and all other particles in the universe,

宇宙中的 任何一种、所有其它的粒子接触，

standard model or otherwise.

无论是根据标准模型还是其它模型。

And in fact, it's the interaction of the muon with those other particles

事实上， 正是μ子与其他粒子的相互作用

that defines how fast it wobbles.

决定了它的摆动速度。

In essence, the more different particles

本质上，在μ子摆动时

that bounce off the muon whilst it is wobbling,

从μ子上反弹的不同粒子越多，

the faster it will wobble.

它摆动的速度就越快。

And so then this is what we want to measure --

因此，这就是我们要测量的——

how fast muons wobble in a magnetic field

μ子在磁场中的摆动速度，

due to their interaction with all the particles and forces

由于它们与宇宙中 所有的粒子和力的相互作用

in the universe.

而产生的摆动的速度。

Now so far, no new particle or force outside of the standard model

到目前为止，在标准模型之外，

that could explain those big mysteries about our universe

还没有发现任何新的粒子或力 可以解释宇宙的

has ever been discovered.

那些巨大谜团。

But the point to reemphasize

但需要再次强调的是，

is that the rate or the speed by which muons wobble

μ子摆动的速度或速率，

when we place them in a magnetic field

当我们将μ子置于磁场时的速度，

is directly defined by all the particles and forces in the universe

是由宇宙中与之接触的所有粒子和力

that it comes into contact with.

直接决定的。

And so, if we can measure very precisely how fast they wobble,

因此，如果我们能非常精确地 测量它的摆动速度，

we can then compare that to the theoretical prediction

我们就可以将其与理论预测的

of how fast they should wobble

μ子摆动速度，

from just the particles and forces of the standard model.

仅根据标准模型中的粒子和力的速度 做比较。

And then, if the measurement was found to be different and larger and disagree,

接着，如果发现测量的结果 不同、更大且存在差异，

then it would be an indication of new particles or forces

则表明在标准模型之外

outside of the standard model

存在着新的粒子或力，

that could explain those big mysteries about our universe.

它们可能可以解释 宇宙中的那些大谜团。

An experiment I work on has done just that.

我参与的一个实验就是这样做的。

This is the Muon g-2 experiment located at Fermilab,

这是一个μ子 g-2 实验， 在费米实验室中进行，

on the outskirts of Chicago.

位于芝加哥郊区。

This ring, which you can see here,

这里你可以看到这个圆环，

is about 20 meters in diameter,

它的直径约为 20 米，

and it's what's called a storage ring magnet.

这就是所谓的储存环磁铁 （一种环形粒子加速器）。

It's a ring in which we store muons inside a magnetic field,

这是一个我们在磁场中储存μ子的环，

which causes them to wobble.

磁场会导致它们摆动。

We then make our measurements of how fast they wobble

然后，我们测量它们的摆动速度，

and compare that to the theory.

并将其与理论值进行比较。

Now, this experiment released its first result in April of 2021,

这个实验在 2021 年 4 月 发布了第一个结果，

and the take-home message of this talk

这次演讲最主要的信息也是

is that the result I am presenting to you here today,

我要在这向大家介绍的

from the Muon g-2 experiment,

来自μ子 g-2 实验的结果，

is the closest glimpse that we've had to seeing a new particle or force

这是我们在地球实验室看到的

here in a laboratory on Earth.

关于新粒子或新力的 最近的一瞥。

And this is that result here.

这就是那个结果。

So let me take some time to explain to you what this graph is showing.

所以让我花点时间 向你们解释一下这张图显示了什么。

On the x-axis are the values for how fast muons wobble

x轴上是μ子摆动速度的值，

when we place them in a magnetic field.

当我们把μ子放入磁场时的摆动速度。

The green marker on the left

左边的绿色标记

is the theoretical prediction for how fast they wobble,

是对它们摆动速度的理论预测值，

from just the particles of the standard model,

该预测仅根据标准模型内的粒子。

and the green band defines the uncertainty on that prediction.

绿色区间描述了该预测的不确定度。

The orange marker on the right is the new experimental measurement

右边的橙色标记是新的实验测量结果，

from the Fermilab Muon g-2 experiment,

该结果来自费米实验室的μ子g-2实验，

and the orange band defines the uncertainty on that measurement.

橙色区间描述了该测量的不确定度。

And by uncertainty, I mean we're statistically certain

我所说的不确定度是指， 从统计学上讲，我们确信

that both the prediction and the measurement,

预测和测量的值

the value for each should be inside their respective bands.

都应在各自的不确定区间内。

And what you can see is not only do those bands not overlap,

你可以看到的是， 这些区间不仅没有重叠，

but they differ by quite a large amount,

而且相差很远，

that white gap in the middle indicating a clear disagreement

中间的白色间隙表明这两个值之间

between the two values.

存在明显的差异。

What this means is that when muons are placed in a magnetic field,

这意味着， 当μ子被置于磁场中时，

they wobble faster than what the theory predicts.

它们的摆动速度比理论预测的要快。

So all the known particles and forces of the standard model

因此，标准模型内的 所有已知的粒子和力

have failed to predict how fast muons have wobbled.

都无法预测μ子的摆动速度。

And what does this suggest?

这说明了什么？

Well, it suggests that there are new particles or forces

这表明存在着新的粒子或力，

that aren’t part of that globally accepted theory

它们还不是那个 全球公认的理论之内，

interacting with the muons and causing them to wobble faster.

它们与μ子相互作用 导致测μ子更快地摆动。

Now, a reason why physicists are so excited about this result

物理学家对这一结果 如此兴奋的一个原因是，

is that the chance that this result is a fluke, statistically,

从统计学上讲， 这个结果只是偶然的几率

is one in 40,000.

是四万分之一。

So that's the same as saying that there's a 99.9975 percent chance

所以也就是说有 99.975% 的概率

that we've seen the influence of a new particle or force

我们看到了新粒子或力产生的影响，

here, in a laboratory on Earth.

就在这，一个地球实验室里。

But a word of caution.

但要谨慎一点。

Physicists actually set a much stricter threshold

实际上， 物理学家设定了更严格的阈值，

by which they can claim a discovery,

限制他们能否称之为一个发现的阈值，

and that is the chance the result is a fluke

这个限制是 结果是个巧合的概率

cannot be more than one in 3.5 million.

不能超过 350 万分之一。

And so we haven't reached that discovery threshold yet,

因此， 我们还没有达到那个发现阈值，

and so we can't definitively say

所以我们无法确切地说

that we've seen the influence of a new particle or force.

我们已经看到了 一种新的粒子或力造成的影响。

And the reality is that,

而现实是，

to reach the one-in-3.5-million threshold,

要达到 350 万分之一的阈值，

there's a lot of work to be done.

还有很多工作要做。

But that work is being done right now

不过这项工作 目前正在被逐步完成

and will continue to be done over the coming years.

并将在未来几年中继续被完成。

So what does this all mean?

那么这一切意味着什么？

Well, first, any result from the Muon g-2 experiment,

首先， 由μ子 g-2 实验得出的任何结果，

even a result that says there were no new particles or forces,

即使是一个表明 不存在新粒子或力的结果，

would be a good result.

它也是一个不错的结果。

That is science, right?

那是科学，对吧？

Sometimes, it's not discovering new things,

有时候，它不是在发现新东西，

sometimes, it's just confirming old things.

有时候，它只是在证实旧东西。

And even if that were the case,

即使是这样，

the by-products of particle physics experiments

粒子物理实验的副产品

have been advancing human civilization for much of the past 100 years.

一直在过去 100 年的大部分时间里 推动着人类文明的发展。

Modern electronics, the internet, satellite navigation --

现代电子设备、互联网、卫星导航——

these are all by-products of particle physics experiments or endeavors.

这些都是 粒子物理实验或努力的副产品。

And there's no telling

而且没有人知道

what experiments like the Muon g-2 experiment

像μ子 g-2 这样的实验

could do for us in the future.

未来还能为我们带来什么。

But if that were the case, and we found no new particle or force,

但是，如果真是这样， 我们没有发现新的粒子或力，

then we wouldn't be able to explain those big mysteries about our universe --

那么我们将无法解释宇宙中的 那些大谜团——

what is dark energy, what is dark matter

什么是暗能量，什么是暗物质，

and where did all the antimatter go?

所有的反物质都去了哪里？

Whatever the outcome,

无论结果如何，

the Muon g-2 experiment will keep releasing results,

μ子 g-2 实验将持续发布结果，

in the next few years,

在未来几年中继续，

that will continue to test our understanding

这将继续检验我们

of the fabric of reality.

对现实的构造的理解。

I, for one, am really excited about it,

首先，我个人对此感到非常兴奋，

and I really hope you stay tuned with us

我也真的希望你能继续关注我们，

to find out if we've definitively discovered a new particle or force,

来看看我们是否能 确凿地发现一种新的粒子或力，

for the first time.

将会是有史以来的第一次。

Thank you very much.

非常感谢你们。

(Applause)

（掌声）