Have we reached the end of physics? | Harry Cliff

翻译人员: Joe Yhin 校对人员: Yolanda Zhang

A hundred years ago this month, a 36-year-old Albert Einstein

在一个世纪前的这个月， 36岁的阿尔伯特•爱因斯坦

stood up in front of the Prussian Academy of Sciences in Berlin

站在柏林的普鲁士科学院门口，

to present a radical new theory of space, time and gravity:

发布着一个有关空间， 时间和引力的激进的新理论：

the general theory of relativity.

广义相对论。

General relativity is unquestionably Einstein's masterpiece,

广义相对论毫无疑问 是爱因斯坦的杰作，

a theory which reveals the workings of the universe at the grandest scales,

它将宇宙在宏观空间下的运作规律

capturing in one beautiful line of algebra

描绘成了一个美丽的线性公式,

everything from why apples fall from trees to the beginning of time and space.

从苹果为什么会从树上掉落 直到时间和空间的起源。

1915 must have been an exciting year to be a physicist.

1915年一定是科学家们 最兴奋的一年。

Two new ideas were turning the subject on its head.

两个崭新的观点 完全改变了当时的物理界。

One was Einstein's theory of relativity,

一个是爱因斯坦的广义相对论，

the other was arguably even more revolutionary:

另一个可以说是更加革命性的：

quantum mechanics,

量子力学，

a mind-meltingly strange yet stunningly successful new way

它是一种极其难以理解 却又出奇地成功的

of understanding the microworld, the world of atoms and particles.

理解微观世界，也就是原子和 微观粒子的世界的新方法。

Over the last century, these two ideas have utterly transformed

在上一个世纪中， 这两种思想已经完全改变了

our understanding of the universe.

我们对宇宙的理解。

It's thanks to relativity and quantum mechanics

多亏了相对论和量子力学，

that we've learned what the universe is made from,

我们才能学到宇宙是由什么组成的，

它是如何开始并且持续演化的。

how it began and how it continues to evolve.

A hundred years on, we now find ourselves at another turning point in physics,

经过了一百年，我们发现 我们现在正处在物理的另一个转折点，

but what's at stake now is rather different.

但是我们现在的处境却截然不同。

The next few years may tell us whether we'll be able

接下来的几年也许会 告诉我们是否能够

to continue to increase our understanding of nature,

继续加深我们对自然的理解，

or whether maybe for the first time in the history of science,

或者我们将在科学史上首次

we could be facing questions that we cannot answer,

面临我们无法回答的问题，

not because we don't have the brains or technology,

这并不是因为我们不够聪明 或者科技不够先进，

but because the laws of physics themselves forbid it.

而是因为物理学的定律 自己束缚了自己。

This is the essential problem: the universe is far, far too interesting.

这是一个非常重要的问题： 宇宙非常，非常有趣。

Relativity and quantum mechanics appear to suggest

相对论和量子力学都阐述了

that the universe should be a boring place.

宇宙应该是一个很无聊的地方。

It should be dark, lethal and lifeless.

它本应该是黑暗，致命和死气沉沉的。

But when we look around us, we see we live in a universe full of interesting stuff,

但是当我们往周围看去时， 会发现我们生活在一个充满有趣事物，

full of stars, planets, trees, squirrels.

充满闪烁的恒星，行星， 植物和动物的宇宙中。

The question is, ultimately,

那么最终问题来了，

why does all this interesting stuff exist?

为什么这些有趣的事物存在着呢？

Why is there something rather than nothing?

为什么这里不是一片空旷呢？

This contradiction is the most pressing problem in fundamental physics,

这个矛盾是基础物理学 面临的最紧迫的问题，

and in the next few years, we may find out whether we'll ever be able to solve it.

而且在接下来的几年里，我们会知道 我们是否有能力去解决这个问题。

At the heart of this problem are two numbers,

在这个问题的核心处，有两个数字，

two extremely dangerous numbers.

两个极其危险的数字。

These are properties of the universe that we can measure,

这就是我们所测量的宇宙的两个性质，

and they're extremely dangerous

它们及其危险，

因为一旦它们有变化， 哪怕是一个细微的变化，

because if they were different, even by a tiny bit,

then the universe as we know it would not exist.

我们所熟知的宇宙将会不复存在。

The first of these numbers is associated with the discovery that was made

第一个数字是关于人类自己的发现，

一个距这里几公里远的， 位于欧洲粒子物理研究所的机器，

a few kilometers from this hall, at CERN, home of this machine,

the largest scientific device ever built by the human race,

人类建造的最大的科技设备，

the Large Hadron Collider.

大型强子对撞机。

The LHC whizzes subatomic particles around a 27-kilometer ring,

大型强子对撞机在周长27公里的环形场中 对亚原子粒子进行加速，

getting them closer and closer to the speed of light

将它们加速到接近光速，

before smashing them into each other inside gigantic particle detectors.

然后让粒子在巨大的 粒子探测器中进行相撞。

On July 4, 2012, physicists at CERN announced to the world

在2012年7月4日， 欧洲粒子物理研究所向世界宣布

that they'd spotted a new fundamental particle

他们发现一个新的基本粒子

being created at the violent collisions at the LHC: the Higgs boson.

在大型强子对撞机中被创造出来了： 希格斯波色子。

Now, if you followed the news at the time,

如果你看了那个时候的新闻后续，

you'll have seen a lot of physicists getting very excited indeed,

你会发现很多物理学家 感到了由衷的兴奋，

and you'd be forgiven for thinking

而且如果你像我们以往

we get that way every time we discover a new particle.

每次发现新粒子时那样兴奋， 是非常可以理解的。

Well, that is kind of true,

确实，从某种意义上说这是真实的，

but the Higgs boson is particularly special.

但是希格斯波色子非常与众不同。

We all got so excited because finding the Higgs

我们如此兴奋是因为找到了希格斯，

proves the existence of a cosmic energy field.

就证明了宇宙能量场是存在的。

Now, you may have trouble imagining an energy field,

现在，你可能很难想象一个能量场，

but we've all experienced one.

但是我们都在经历它。

If you've ever held a magnet close to a piece of metal

如果你曾经让一个磁体靠近一块金属，

and felt a force pulling across that gap,

并且感觉到一种把磁体推向金属的力，

then you've felt the effect of a field.

那么你就感受过场的影响。

And the Higgs field is a little bit like a magnetic field,

希格斯场有一点儿类似磁场，

except it has a constant value everywhere.

不过希格斯场在任何地方 都有同样的值。

It's all around us right now.

它现在就在我们周围。

We can't see it or touch it,

我们虽然不能看见或者触摸它，

but if it wasn't there,

但是如果它不在那儿，

we would not exist.

那我们也就不存在了。

The Higgs field gives mass

希格斯场将质量递给

to the fundamental particles that we're made from.

组成我们的基本粒子。

If it wasn't there, those particles would have no mass,

如果它不存在，这些粒子将不会有质量，

那么没有原子会被组成， 我们也就不可能存在了。

and no atoms could form and there would be no us.

But there is something deeply mysterious about the Higgs field.

但是关于希格斯场 还存在一些很深的谜团。

Relativity and quantum mechanics tell us that it has two natural settings,

相对论和量子理论告诉我们 它有两个自然属性，

a bit like a light switch.

有点儿像电灯的开关。

It should either be off,

它可能是关，

so that it has a zero value everywhere in space,

那么在空间的任何地方的值都为零，

or it should be on so it has an absolutely enormous value.

或者是开，那么在空间的 任何地方的值都是巨大的。

In both of these scenarios, atoms could not exist,

在这两种场景下，原子都不可能存在，

and therefore all the other interesting stuff

其他在宇宙中围绕着我们的

that we see around us in the universe would not exist.

一切有趣的东西也将不复存在。

In reality, the Higgs field is just slightly on,

在现实中，希格斯场只是 处于一个细微的开启状态，

not zero but 10,000 trillion times weaker than its fully on value,

并不等于零，但是只有全开状态下的 1万万亿分之一，

a bit like a light switch that's got stuck just before the off position.

就像灯的开关在 即将关闭的位置被卡住了一样。

And this value is crucial.

这个值是至关重要的。

If it were a tiny bit different,

如果这个值有一点点的改变，

then there would be no physical structure in the universe.

那么宇宙将会失去一切的物理结构。

So this is the first of our dangerous numbers,

因此这是第一个至关重要的数字，

the strength of the Higgs field.

希格斯场的强度。

Theorists have spent decades trying to understand

理论家们花费了数十年去尝试理解

why it has this very peculiarly fine-tuned number,

为什么它有如此异常的数字，

and they've come up with a number of possible explanations.

并且他们提出了一些可能的解释。

They have sexy-sounding names like "supersymmetry"

包括有一些听起来 很性感的名字比如“超对称”，

or "large extra dimensions."

或者“巨大额外维度”。

I'm not going to go into the details of these ideas now,

我现在并不打算深入去探讨这些，

but the key point is this:

但是重点在于：

if any of them explained this weirdly fine-tuned value of the Higgs field,

如果它们其中有能够 解释希格斯场的诡异调整值，

then we should see new particles being created at the LHC

那么我们应该能够看到新的粒子 随着希格斯波色子

along with the Higgs boson.

一起被创造出来。

So far, though, we've not seen any sign of them.

然而迄今为止，我们并没有看到 任何有关它们存在的迹象。

But there's actually an even worse example

不过这儿甚至有更糟糕的

of this kind of fine-tuning of a dangerous number,

关于这个诡异调整值的例子，

and this time it comes from the other end of the scale,

而且这次它来自于 这个范围的另外一个边缘，

from studying the universe at vast distances.

来自于对于从广袤距离上 对宇宙的学习。

One of the most important consequences of Einstein's general theory of relativity

爱因斯坦的广义相对论带来的 最重要的结果之一,

was the discovery that the universe began as a rapid expansion of space and time

就是对于空间与时间从138亿年前

13.8 billion years ago, the Big Bang.

开始急速膨胀的发现， 也就是宇宙大爆炸。

Now, according to early versions of the Big Bang theory,

如今，根据宇宙大爆炸理论 最早的版本来看，

the universe has been expanding ever since

宇宙一直都在膨胀，

with gravity gradually putting the brakes on that expansion.

并且伴随着与之相对的引力。

But in 1998, astronomers made the stunning discovery

不过在1998年， 天文学家们得到了一个惊人的发现，

that the expansion of the universe is actually speeding up.

那就是宇宙的膨胀速度正在逐步上升。

The universe is getting bigger and bigger faster and faster

宇宙在一个神秘的排斥力， 被称为暗能量的作用下，

driven by a mysterious repulsive force called dark energy.

正在变得越来越大 而且膨胀地越来越快。

Now, whenever you hear the word "dark" in physics,

现在，当你在物理学上 听到“暗”这个词的时候，

you should get very suspicious

你应该表示怀疑，

because it probably means we don't know what we're talking about.

因为它可能表示 我们并不知道我们所谈论的东西。

（笑）

(Laughter)

我们并不知道暗能量是什么，

We don't know what dark energy is,

but the best idea is that it's the energy of empty space itself,

不过最好的想法是暗能量就是 空旷的宇宙本身，

the energy of the vacuum.

真空能量。

Now, if you use good old quantum mechanics to work out

现在，如果你用老式的量子力学来解释

how strong dark energy should be,

暗能量有多强的时候，

you get an absolutely astonishing result.

你绝对会得到一个震惊的结果。

You find that dark energy

你会发现暗能量的强度

should be 10 to the power of 120 times stronger

比天文学观测到的值

than the value we observe from astronomy.

要强上10的120次方倍。

That's one with 120 zeroes after it.

这是一个1后面跟了120个0。

This is a number so mind-bogglingly huge

这个数字是如此的大，

that it's impossible to get your head around.

以至于已经超出了你的理解范围。

We often use the word "astronomical" when we're talking about big numbers.

当我们在讨论很大的数字时， 我们经常用“天文数字”这个词。

Well, even that one won't do here.

但即便是那个词， 也无法描述这个数字。

This number is bigger than any number in astronomy.

这个数字比天文学上的任何数字都要大。

It's a thousand trillion trillion trillion times bigger

它比整个宇宙所含有的原子数还要大

than the number of atoms in the entire universe.

1000万亿万亿万亿倍。

So that's a pretty bad prediction.

因此那是一个很差劲的预测。

In fact, it's been called the worst prediction in physics,

事实上，它被称为物理界上 最不准确的预测，

and this is more than just a theoretical curiosity.

并且这不仅仅是出于 一个理论上的好奇心。

If dark energy were anywhere near this strong,

如果暗能量真的有那么强，

then the universe would have been torn apart,

那么整个宇宙早就被扯开了，

stars and galaxies could not form, and we would not be here.

星星和银河系不会成形， 我们也不可能会在这儿。

So this is the second of those dangerous numbers,

所以这是第二个危险的数字，

the strength of dark energy,

暗能量的强度，

and explaining it requires an even more fantastic level of fine-tuning

而且对它的解释需要达到比希格斯场

than we saw for the Higgs field.

更加奇妙的等级。

But unlike the Higgs field, this number has no known explanation.

不过不像希格斯场， 这个数字并没有已知的解释。

The hope was that a complete combination

现在的希望是能够将

of Einstein's general theory of relativity,

爱因斯坦的广义相对论，

which is the theory of the universe at grand scales,

也就是宏观宇宙的理论，

with quantum mechanics, the theory of the universe at small scales,

还有量子力学，微观世界的理论 进行统一，

might provide a solution.

也许能够让我们得出一个结论。

Einstein himself spent most of his later years

爱因斯坦白白花费了 他晚年的大部分时间

on a futile search for a unified theory of physics,

来寻找一个统一的物理理论，

and physicists have kept at it ever since.

并且物理学家们从那之后 也一直致力于同样的事。

One of the most promising candidates for a unified theory is string theory,

最有希望的候选者之一就是弦理论了，

and the essential idea is,

它的核心思想就是，

if you could zoom in on the fundamental particles that make up our world,

如果你能够放大组成我们的世界的粒子，

you'd see actually that they're not particles at all,

你会发现它们事实上根本就不是粒子，

but tiny vibrating strings of energy,

而是微小的正在震动的能量弦，

with each frequency of vibration corresponding to a different particle,

每个不同频率的震动 代表着不同的粒子，

a bit like musical notes on a guitar string.

有点类似于吉他弦上的音符。

So it's a rather elegant, almost poetic way of looking at the world,

因此这是一个相当优美， 而且很有诗意的看待这个世界的方式，

but it has one catastrophic problem.

不过它有一个很严重的问题。

It turns out that string theory isn't one theory at all,

那就是弦理论并不只是一个理论，

but a whole collection of theories.

而是很多个理论的集合。

It's been estimated, in fact,

据估计，实际上，

that there are 10 to the 500 different versions of string theory.

弦理论一共有10到500种不同的版本。

Each one would describe a different universe

每一种都能够描述一个不同的宇宙，

with different laws of physics.

还有其伴随着的物理定律。

Now, critics say this makes string theory unscientific.

现在，反对者们说 这让弦理论变得不科学。

You can't disprove the theory.

因为你不能反驳这个理论。

But others actually turned this on its head

不过其他的人却并不同意，

and said, well, maybe this apparent failure

并且说道，也许这个很明显的错误，

is string theory's greatest triumph.

而它恰恰也是弦理论最大的成功。

What if all of these 10 to the 500 different possible universes

要是这10到500种不同的宇宙

actually exist out there somewhere

真的存在于多元宇宙中的

in some grand multiverse?

某些地方呢？

Suddenly we can understand

瞬间，我们就能够理解

the weirdly fine-tuned values of these two dangerous numbers.

这两个危险数字的诡异调整值了。

In most of the multiverse,

在大部分的多元宇宙中，

dark energy is so strong that the universe gets torn apart,

暗能量将整个宇宙扯碎，

或者是希格斯场的强度弱到 不允许任何原子的成形。

or the Higgs field is so weak that no atoms can form.

We live in one of the places in the multiverse

我们生活在其中一个 多元宇宙中的某个地方，

where the two numbers are just right.

在这个地方这两个数值恰好合适。

We live in a Goldilocks universe.

我们住在金发歌蒂的宇宙中 （译注：意为各种条件刚刚合适）。

Now, this idea is extremely controversial, and it's easy to see why.

现在，这个想法非常容易引起争议， 并且我们很容易明白为什么。

If we follow this line of thinking,

如果我们跟随着这种想法，

then we will never be able to answer the question,

那么我们将永远也无法回答这个问题，

"Why is there something rather than nothing?"

“为什么这儿不是一片空旷呢？”

In most of the multiverse, there is nothing,

在多元宇宙中的大多数宇宙里， 那儿什么也没有，

and we live in one of the few places

而且我们生活在少数的

where the laws of physics allow there to be something.

存在物理定律， 并且不是一片空旷的宇宙中。

Even worse, we can't test the idea of the multiverse.

更糟的是，我们甚至不能 测试多元宇宙这个想法。

We can't access these other universes,

我们无法访问其它的宇宙，

so there's no way of knowing whether they're there or not.

因此我们无从得知 其它的宇宙是否存在。

So we're in an extremely frustrating position.

所以我们正处在一个很沮丧的位置。

那并不表示多元宇宙并不存在。

That doesn't mean the multiverse doesn't exist.

There are other planets, other stars, other galaxies,

还有其它的行星， 其它的恒星和其它的银河系，

so why not other universes?

那么为什么不能有其它的宇宙呢？

The problem is, it's unlikely we'll ever know for sure.

问题在于，这并不像我们最终能够 得出准确结论的其它事一样。

Now, the idea of the multiverse has been around for a while,

现在，多元宇宙的思想 已经提出有一段时间了，

but in the last few years, we've started to get the first solid hints

不过在过去的几年里， 我们才开始得到可靠的迹象

that this line of reasoning may get born out.

来证明这个解释能够行得通。

Despite high hopes for the first run of the LHC,

不管我们对大型强子对撞机的 第一次测试

what we were looking for there --

抱有多大的希望——

我们正在寻求物理学上的 一个新的理论：

we were looking for new theories of physics:

超对称性或者是大型额外维度，

supersymmetry or large extra dimensions

能够解释希格斯场诡异的调整值。

that could explain this weirdly fine-tuned value of the Higgs field.

But despite high hopes, the LHC revealed a barren subatomic wilderness

不过不管我们抱有多高的希望， 大型强子对撞机只显示出了一个贫瘠的，

populated only by a lonely Higgs boson.

只含有希格斯波色子的荒漠。

My experiment published paper after paper

我的实验数据已经 发表了一篇又一篇文章，

where we glumly had to conclude that we saw no signs of new physics.

显示我们并没有看到 任何有关新的物理现象的迹象。

The stakes now could not be higher.

我们现在的处境已经 前所未有地危险了。

这个暑假，大型强子对撞机 开始了第二次运行，

This summer, the LHC began its second phase of operation

它的能量将近是第一次的两倍。

with an energy almost double what we achieved in the first run.

What particle physicists are all desperately hoping for

量子物理学家们不顾一切地希望着

are signs of new particles, micro black holes,

新粒子，微型黑洞的迹象，

or maybe something totally unexpected

或者是任何意料之外的现象

emerging from the violent collisions at the Large Hadron Collider.

能够出现在大型强子对撞机的碰撞中。

If so, then we can continue this long journey

如果真的出现了， 那么我们就能够继续这个

that began 100 years ago with Albert Einstein

100年前由爱因斯坦开始的

towards an ever deeper understanding of the laws of nature.

更深入探索自然界定律的漫长旅程。

But if, in two or three years' time,

不过如果，在两到三年后，

when the LHC switches off again for a second long shutdown,

当大型强子对撞机再次结束时，

we've found nothing but the Higgs boson,

我们除了希格斯波色子之外 还是什么也没发现，

then we may be entering a new era in physics:

那么我们也许会进入 物理史上的新纪元：

an era where there are weird features of the universe that we cannot explain;

一个拥有我们无法解释的 诡异现象的宇宙的纪元；

一个提示着我们有着令人沮丧的

an era where we have hints that we live in a multiverse

that lies frustratingly forever beyond our reach;

无法到达的多元宇宙的纪元；

一个我们永远也无法回答这个问题，

an era where we will never be able to answer the question,

“为什么这儿不是一片空旷呢？” 的纪元。

"Why is there something rather than nothing?"

Thank you.

谢谢大家。

(Applause)

（掌声）

Bruno Giussani: Harry, even if you just said

Bruno Giussani （BG）: 哈利，尽管你刚提到

the science may not have some answers,

科学也许无法回答这些问题，

I would like to ask you a couple of questions, and the first is:

我还是想问问你几个问题， 第一个问题是：

建造大型强子对撞机 是一个世代的工程。

building something like the LHC is a generational project.

I just mentioned, introducing you, that we live in a short-term world.

当我介绍你的时候， 我提到了我们住在一个短周期的世界里。

How do you think so long term,

那么跳出来看， 对于这一代人花了这么久的时间

projecting yourself out a generation when building something like this?

建造这样一个东西，你是怎么想的？

Harry Cliff: I was very lucky

Harry Cliff （HC）: 我非常幸运

能够在2008年加入到 大型强子对撞机的这个实验中，

that I joined the experiment I work on at the LHC in 2008,

just as we were switching on,

当时这个项目刚刚开始，

and there are people in my research group who have been working on it

我的研究组里就有人 已经从事这个方向的研究

长达三十年了， 他们的整个生涯都在这个机器上。

for three decades, their entire careers on one machine.

因此我认为第一次关于大型强子对撞机的 对话是在1976年，

So I think the first conversations about the LHC were in 1976,

and you start planning the machine without the technology

而且在你需要的科技还并不存在时，

就开始计划去建造它。

that you know you're going to need to be able to build it.

因此当开始认真设计时的90年代，

So the computing power did not exist in the early '90s

计算水平还远远不够。

when design work began in earnest.

One of the big detectors which record these collisions,

在打造能记录这些碰撞的 大型探测器其中之一时，

他们并不认为科技能够先进到

they didn't think there was technology

that could withstand the radiation that would be created in the LHC,

让它承受大型强子对撞机 可能产生的辐射，

so there was basically a lump of lead in the middle of this object

因此在这些探测器中间

有一块铅块，

with some detectors around the outside,

不过随后我们发展了科技。

but subsequently we have developed technology.

因此你必须依靠人们的心灵手巧来 解决这些问题，

So you have to rely on people's ingenuity, that they will solve the problems,

不过这也许会花费10年甚至更长的时间。

but it may be a decade or more down the line.

BG: 中国就在两到三个礼拜前刚宣布

BG: China just announced two or three weeks ago

that they intend to build

他们计划建造

一个大型强子对撞机两倍大小的 超级对撞机。

a supercollider twice the size of the LHC.

我想知道你和你的同事 是如何看待这条新闻的。

I was wondering how you and your colleagues welcome the news.

HC: Size isn't everything, Bruno. BG: I'm sure. I'm sure.

HC：大小并不代表任何东西， Bruno。 BG：那是当然。那是当然。

(Laughter)

（笑声）

It sounds funny for a particle physicist to say that.

HC：这从一个粒子物理学家嘴里 说出来也许很滑稽。

But I mean, seriously, it's great news.

不过很严肃地说， 这是个好消息。

So building a machine like the LHC

建造一个像大型强子对撞机的机器

requires countries from all over the world to pool their resources.

要求全世界的国家来汇集它们的资源。

没有哪个国家能够 单独建造如此大的机器，

No one nation can afford to build a machine this large,

apart from maybe China,

也可能中国是个例外，

because they can mobilize huge amounts of resources,

因为他们能够动员大量的资源，

manpower and money to build machines like this.

劳动力和资金来建造这个。

So it's only a good thing.

因此这只能是一件好事。

他们将要计划去做的事是建造一个机器，

What they're really planning to do is to build a machine

that will study the Higgs boson in detail and could give us some clues

然后深入学习希格斯波色子 并且提供我们一些线索，

as to whether these new ideas, like supersymmetry, are really out there,

就像超对称一样，真实地存在于那儿，

so it's great news for physics, I think.

所以我认为这对于 物理学家来说是一件好事。

BG：哈利，谢谢你。 HC：非常感谢你。

BG: Harry, thank you. HC: Thank you very much.

（掌声）

(Applause)