Why our universe might exist on a knife-edge | Gian Giudice

翻译人员: Xiangli Wang 校对人员: Bighead Ge

So last year, on the Fourth of July,

去年七月四日

experiments at the Large Hadron Collider

通过在大型强子对撞机上进行实验

discovered the Higgs boson.

我们发现了希格斯玻色子

It was a historical day.

这是历史性的一天

There's no doubt that from now on,

毫无疑问

the Fourth of July will be remembered

从此以后 七月四日将被人铭记

not as the day of the Declaration of Independence,

我们记住它 不是因为这天发表了《独立宣言》

but as the day of the discovery of the Higgs boson.

而是因为在那天 我们发现了希格斯玻色子

Well, at least, here at CERN.

好吧 至少在欧洲核子研究中心是这样的

But for me, the biggest surprise of that day

但对我来说 那天最大的惊喜

was that there was no big surprise.

是没有惊喜

In the eye of a theoretical physicist,

在理论物理学家看来

the Higgs boson is a clever explanation

希格斯玻色子能灵活地解释

of how some elementary particles gain mass,

一些基本粒子是如何获得质量的

but it seems a fairly unsatisfactory

但它似乎是一个不太完整

and incomplete solution.

且难令人满意的解答

Too many questions are left unanswered.

有许多问题仍然未被解决

The Higgs boson does not share the beauty,

希格斯玻色子不具备

the symmetry, the elegance,

和其他基本粒子一样的

of the rest of the elementary particle world.

简洁 美感和对称性

For this reason, the majority of theoretical physicists

从这点上说，大多数的理论物理学家

believe that the Higgs boson could not

认为希格斯玻色子

be the full story.

并非一个完整的解释

We were expecting new particles and new phenomena

基于希格斯玻色子的发现

accompanying the Higgs boson.

我们期待与之有关的新粒子和现象

Instead, so far, the measurements

然而 就目前来看

coming from the LHC show no signs of new particles

大型强子对撞机的实验表明

or unexpected phenomena.

并没有发现新粒子或新现象

Of course, the verdict is not definitive.

当然 这一结论并非板上钉钉

In 2015, the LHC will almost double

到2015年 大型强子对撞机

the energy of the colliding protons,

将使碰撞的质子能量翻倍

and these more powerful collisions

更强烈的质子碰撞

will allow us to explore further the particle world,

能让我们进一步地探索粒子世界

and we will certainly learn much more.

我们也一定会了解更多

But for the moment, since we have found

截至目前 我们尚未发现新现象

no evidence for new phenomena, let us suppose

让我们用已知的粒子

that the particles that we know today,

做一个假设

including the Higgs boson,

包括希格斯玻色子在内的粒子

are the only elementary particles in nature,

是自然中唯一的基本粒子

even at energies much larger

而其能量比我们目前发现的

than what we have explored so far.

要大上许多

Let's see where this hypothesis is going to lead us.

让我们看看 这个假设会带我们发现什么

We will find a surprising and intriguing result

我们会发现在宇宙中存在一个令人惊讶而有趣的结论

about our universe, and to explain my point,

为解释我的观点

let me first tell you what the Higgs is about,

首先 我想解释一下什么是希格斯粒子

and to do so, we have to go back

让我们先回到

to one tenth of a billionth of a second

宇宙大爆炸后的

after the Big Bang.

一亿分之一秒

And according to the Higgs theory,

根据希格斯的理论

at that instant, a dramatic event took place

在那一刻 宇宙中发生了

in the universe.

一件重要的大事

Space-time underwent a phase transition.

时空经历了相变过程

It was something very similar to the phase transition

相变是非常类似于

that occurs when water turns into ice

水在零摄氏度下结冰的

below zero degrees.

一种物理过程

But in our case, the phase transition

但在刚才的例子中

is not a change in the way the molecules

相变不是物体内部分子排列

are arranged inside the material,

发生变化

but is about a change

而是时空的构造

of the very fabric of space-time.

发生了改变

During this phase transition, empty space

在相变过程中

became filled with a substance

空间被物质所填充

that we now call Higgs field.

我们称之为希格斯场

And this substance may seem invisible to us,

这种物质具有不可见性

but it has a physical reality.

但拥有物理的现实性

It surrounds us all the time,

它一直环绕着我们

just like the air we breathe in this room.

就好像我们在房间里呼吸的空气一样

And some elementary particles interact

一些基本粒子与这种物质接触

with this substance, gaining energy in the process.

在此过程中形成质量

And this intrinsic energy is what we call

这一固有的我们称之为

the mass of a particle,

粒子的质量

and by discovering the Higgs boson, the LHC

通过发现希格斯玻色子 大型强子对撞机

has conclusively proved that this substance is real,

确实证明了这种物质是真实存在的

because it is the stuff the Higgs bosons are made of.

因为它是生成希格斯玻色子的原材料

And this, in a nutshell, is the essence of the Higgs story.

总而言之 它是发现希格斯粒子的关键

But this story is far more interesting than that.

但故事比这要有趣得多

By studying the Higgs theory,

通过研究希格斯的理论

theoretical physicists discovered,

理论物理学家发现

not through an experiment

他们以数学推演

but with the power of mathematics,

而非物理实验的方法发现

that the Higgs field does not necessarily exist

希格斯场并非必然

only in the form that we observe today.

以我们如今观测到的形式存在

Just like matter can exist as liquid or solid,

正如物质能以液态或固态存在

so the Higgs field, the substance that fills all space-time,

同理也适用于希格斯场

could exist in two states.

填充整个时空的物质能以两种状态存在

Besides the known Higgs state,

除了已知的希格斯场之外

there could be a second state in which the Higgs field

第二种状态

is billions and billions times denser

比我们现在观察的希格斯场的密度要高出

than what we observe today,

几十亿倍

and the mere existence of another state

希格斯场的另一种状态的存在

of the Higgs field poses a potential problem.

提出了一个潜在的问题

This is because, according to the laws

因为 根据量子力学

of quantum mechanics, it is possible

两种状态下的转化

to have transitions between two states,

是可以实现的

even in the presence of an energy barrier

即使是处在能量屏障出现

separating the two states,

分割两种状态的情况下

and the phenomenon is called,

而这种现象

quite appropriately, quantum tunneling.

被恰如其分地称为量子隧道

Because of quantum tunneling,

由于量子隧道的存在

I could disappear from this room

我可以在这里消失

and reappear in the next room,

重新在下一间房子里出现

practically penetrating the wall.

可以说 我能穿墙而过

But don't expect me to actually perform the trick

不过别指望我能真的能在大家面前

in front of your eyes, because the probability

表演这个把戏

for me to penetrate the wall is ridiculously small.

我能穿墙而过的可能性微乎其微

You would have to wait a really long time

大家不得不在我成功之前

before it happens, but believe me,

等上好长一段时间 但是相信我

quantum tunneling is a real phenomenon,

量子隧道是一种真实的现象

and it has been observed in many systems.

许多领域都已观测到了它

For instance, the tunnel diode,

例如 隧道二极管

a component used in electronics,

一种在电子工业里使用的元件

works thanks to the wonders

它的工作机制就得归功于

of quantum tunneling.

量子隧道的奇妙原理

But let's go back to the Higgs field.

让我们再回到希格斯场

If the ultra-dense Higgs state existed,

如果超密度希格斯场确实存在

then, because of quantum tunneling,

那么 由于量子隧道效应

a bubble of this state could suddenly appear

在这一状态下 气泡会在

in a certain place of the universe at a certain time,

某一时间和宇宙的某一地点突然出现

and it is analogous to what happens when you boil water.

这就好像你烧一壶水

Bubbles of vapor form inside the water,

水从内部产生水蒸气气泡

then they expand, turning liquid into gas.

然后它们膨胀 从液体变成气体

In the same way, a bubble of the ultra-dense Higgs state

同样 超密度希格斯场

could come into existence because of quantum tunneling.

会因为量子隧道而产生

The bubble would then expand at the speed of light,

这种气泡会以光速急速膨胀

invading all space, and turning the Higgs field

扩张到所有空间 并把希格斯场

from the familiar state into a new state.

从通常状态变成新的状态

Is this a problem? Yes, it's a big a problem.

这有什么问题呢？ 这是一个大问题

We may not realize it in ordinary life,

在普通日常生活中 我们也许不会意识到

but the intensity of the Higgs field is critical

希格斯场的强度

for the structure of matter.

对物质的结构非常重要

If the Higgs field were only a few times more intense,

如果希格斯场的强度仅仅高上几倍

we would see atoms shrinking, neutrons decaying

我们看到原子正在萎缩

inside atomic nuclei, nuclei disintegrating,

中子正在衰减 原子核将会分裂

and hydrogen would be

而氢元素将成为

the only possible chemical element in the universe.

宇宙中唯一的一种化学物质

And the Higgs field, in the ultra-dense Higgs state,

而在超密度状态下的希格斯场

is not just a few times more intense than today,

其密度不是仅仅比今天的大了几倍

but billions of times,

而是大了几十亿倍

and if space-time were filled by this Higgs state,

如果时空被这种状态下的希格斯场填充

all atomic matter would collapse.

那么所有的原子级物质都会崩塌

No molecular structures would be possible, no life.

分子结构也不可能形成 没有生命

So, I wonder, is it possible

所以 我猜想

that in the future, the Higgs field

在未来 希格斯场是否会经历

will undergo a phase transition and,

相变的过程

through quantum tunneling, will be transformed

通过量子隧道

into this nasty, ultra-dense state?

转化为这种糟糕的超密度状态呢？

In other words, I ask myself, what is the fate

换句话说 我问自己

of the Higgs field in our universe?

希格斯场在宇宙中的命运将是如何？

And the crucial ingredient necessary

要回答这个问题的

to answer this question is the Higgs boson mass.

关键信息是希格斯玻色子的能量

And experiments at the LHC found that the mass

大型强子对撞机的实验发现

of the Higgs boson is about 126 GeV.

希格斯玻色子的能量是1260亿电子伏特

This is tiny when expressed in familiar units,

如果传递能量给相同单位 这个数字很小

because it's equal to something like

因为两者等于

10 to the minus 22 grams,

10克和-22克的关系

but it is large in particle physics units,

但这一数字在粒子的物理单位上很大

because it is equal to the weight

因为 这相当于整个

of an entire molecule

DNA分子组成结构的

of a DNA constituent.

重量

So armed with this information from the LHC,

在获得强子对撞机实验信息之后

together with some colleagues here at CERN,

我和几位在欧洲核子研究中心的同事

we computed the probability

合作用电脑计算

that our universe could quantum tunnel

我们的宇宙通过量子隧道转化成

into the ultra-dense Higgs state,

超密度希格斯场的可能性

and we found a very intriguing result.

我们发现了一个有趣的结果

Our calculations showed

计算结果显示

that the measured value of the Higgs boson mass

希格斯玻色子能量的测定值

is very special.

非常特殊

It has just the right value

它的数值恰好能使

to keep the universe hanging

整个宇宙

in an unstable situation.

在一种不稳定的状态下摇摆

The Higgs field is in a wobbly configuration

希格斯场就是在这样一种不稳定的设置中

that has lasted so far

持续到了现在

but that will eventually collapse.

但它终将瓦解

So according to these calculations,

因此 通过这些计算

we are like campers

我们就像露营者

who accidentally set their tent

一不小心把帐篷

at the edge of a cliff.

搭在了悬崖边上

And eventually, the Higgs field

最终 希格斯场

will undergo a phase transition

将会经历相变

and matter will collapse into itself.

物质将会崩塌

So is this how humanity is going to disappear?

所以 这就是人类最后灭绝的方式吗？

I don't think so.

我并不这样认为

Our calculation shows that quantum tunneling

我们的数据显示

of the Higgs field is not likely to occur

希格斯场的量子隧道效应

in the next 10 to the 100 years,

不太容易在接下来的10年到100年内发生

and this is a very long time.

这是相当长的一段时间

It's even longer than

它甚至比意大利

the time it takes for Italy to form a stable government.

组织一届稳定的政府所花的时间还要长

(Laughter)

（笑声）

Even so, we will be long gone by then.

即使如此 到那时 我们早已不复存在

In about five billion years,

大约50亿年后

our sun will become a red giant,

太阳将变成红巨星

as large as the Earth's orbit,

膨胀程度大到地球的轨道

and our Earth will be kaput,

地球将被吞噬

and in a thousand billion years,

而在一万亿年之后

if dark energy keeps on fueling

如果暗能量继续获得补给

space expansion at the present rate,

空间扩张仍保持现在的速率

you will not even be able to see as far as your toes,

你会根本看不到自己的脚趾头

because everything around you

因为环绕你的一切

expands at a rate faster than the speed of light.

都在以比光速快的速度膨胀

So it is really unlikely

所以 我们不大可能

that we will be around to see the Higgs field collapse.

看到希格斯场的崩塌

But the reason why I am interested

但我对希格斯场的转化

in the transition of the Higgs field

萌发兴趣的原因在于

is because I want to address the question,

我想问这个问题

why is the Higgs boson mass so special?

为什么希格斯玻色子的能量如此特殊？

Why is it just right to keep the universe

为什么它能正好让宇宙平衡在

at the edge of a phase transition?

发生相位的临界点？

Theoretical physicists always ask "why" questions.

理论物理学家经常问“为什么”

More than how a phenomenon works,

问得比某种现象是如何产生的更多

theoretical physicists are always interested in

理论物理学家常对于

why a phenomenon works in the way it works.

某种现象为何遵循着某规律而呈现感兴趣

We think that this these "why" questions

我们认为这些“为什么”的问题

can give us clues

可以带来一些

about the fundamental principles of nature.

自然中基本原则的线索

And indeed, a possible answer to my question

事实上 解释我问题的答案

opens up new universes, literally.

开辟了全新的许多宇宙

It has been speculated that our universe

可以推测到 我们的宇宙

is only a bubble in a soapy multiverse

仅仅是多元宇宙肥皂泡下的一个小泡泡

made out of a multitude of bubbles,

而这个多元宇宙由千千万万个小泡泡组成

and each bubble is a different universe

每个气泡里都是一个不同的宇宙

with different fundamental constants

其中蕴含着不同的物理常数

and different physical laws.

和不同物理定律

And in this context, you can only talk about

在此背景下 你只能讨论

the probability of finding a certain value of the Higgs mass.

发现希格斯粒子能量为常量的可能性

Then the key to the mystery

这一神秘事件的关键

could lie in the statistical properties

在于多元宇宙下的

of the multiverse.

统计特性

It would be something like what happens

这就如同在海滩的沙丘上

with sand dunes on a beach.

发生的事情一样

In principle, you could imagine to find sand dunes

一般而言 你会猜想在沙丘上可以找到

of any slope angle in a beach,

不同大小的斜角角度

and yet, the slope angles of sand dunes

然而 沙丘所形成的角度

are typically around 30, 35 degrees.

基本上都在30度到35度左右

And the reason is simple:

道理很简单：

because wind builds up the sand, gravity makes it fall.

因为 风力塑造了沙丘 重力使沙子滑落

As a result, the vast majority of sand dunes

结果就是 大部分的沙丘

have slope angles around the critical value,

形成的斜角角度都在临近坍塌的

near to collapse.

临界值左右

And something similar could happen

类似的事情也发生在

for the Higgs boson mass in the multiverse.

多元宇宙下的希格斯玻色子

In the majority of bubble universes,

在大部分气泡宇宙中

the Higgs mass could be around the critical value,

希格斯粒子的能量会围绕某个临界值

near to a cosmic collapse of the Higgs field,

这个值临近希格斯场发生宇宙坍塌

because of two competing effects,

这是因为有两个相互竞争的因素

just as in the case of sand.

就如同在沙丘例子中提到的那样

My story does not have an end,

我的故事没有结局

because we still don't know the end of the story.

因为我们还是不知道这个故事的结局

This is science in progress,

科学在发展

and to solve the mystery, we need more data,

为找到答案 我们需要更多的数据

and hopefully, the LHC will soon add new clues

可喜的是 大型强子对撞机

to this story.

为这个故事加入了新的线索

Just one number, the Higgs boson mass,

仅仅一个数字 希格斯玻色子的能量

and yet, out of this number we learn so much.

我们就从它身上研究了如此之多

I started from a hypothesis, that the known particles

我从一个假设出发：

are all there is in the universe,

已知的粒子遍布整个宇宙

even beyond the domain explored so far.

更分布在我们已探索到宇宙的更远处

From this, we discovered that the Higgs field

据此 我们挖掘出

that permeates space-time may be standing

渗透在时空中的希格斯粒子可能正站在

on a knife edge, ready for cosmic collapse,

刀刃上 随时准备宇宙坍塌

and we discovered that this may be a hint

我们发现这可能是一个提示

that our universe is only a grain of sand

暗示着我们的宇宙只是广袤的沙漠中的一粒

in a giant beach, the multiverse.

或者只是多元宇宙中的一个

But I don't know if my hypothesis is right.

但我不知道自己的假设是否正确

That's how physics works: A single measurement

这就是物理的发展：一个简单的测量结果

can put us on the road to a new understanding

能指引我们

of the universe

通向全新地理解宇宙的光明大道

or it can send us down a blind alley.

或者带着我们走进一条死胡同

But whichever it turns out to be,

但不论结果如何

there is one thing I'm sure of:

但有一点我可以肯定

The journey will be full of surprises.

探索的旅程将充满惊喜

Thank you.

谢谢

(Applause)

（掌声）