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

譯者: Candie Lin 審譯者: Yuexin Gao

So last year, on the Fourth of July,

去年7月4號

experiments at the Large Hadron Collider

在大型強子對撞機(LHC)的實驗裡

discovered the Higgs boson.

希格斯玻色子被發現了

It was a historical day.

那是歷史性的一刻

There's no doubt that from now on,

無庸置疑地,從現在開始

the Fourth of July will be remembered

7月4號不再被認為是 美國獨立紀念日

not as the day of the Declaration of Independence,

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

而是發現希格斯玻色子的重要日子

Well, at least, here at CERN.

至少對歐洲核子研究組織是這樣的

But for me, the biggest surprise of that day

但是對我而言,那天最大的驚喜

was that there was no big surprise.

就是沒有太大的驚喜

In the eye of a theoretical physicist,

在物理理論學家的眼中

the Higgs boson is a clever explanation

希格斯玻子是一個很絕妙的解釋

of how some elementary particles gain mass,

它解釋了一些基本粒子如何獲得質量

but it seems a fairly unsatisfactory

但是這看來就是個不盡滿意

and incomplete solution.

而且不夠完整的解答

Too many questions are left unanswered.

太多問題都無法回答

The Higgs boson does not share the beauty,

希格斯玻色子不夠美麗

the symmetry, the elegance,

不夠均稱,不夠優雅

of the rest of the elementary particle world.

不足以和基本粒子世界相比

For this reason, the majority of theoretical physicists

因此,大多數理論學家

believe that the Higgs boson could not

不相信希格斯玻色子就是所有的真相

be the full story.

We were expecting new particles and new phenomena

我們希望新的粒子和新的現象

accompanying the Higgs boson.

能隨著希格斯玻色子出現

Instead, so far, the measurements

但目前從LHC對撞機得來的測量 卻沒有顯示什麼新的粒子和新的現象

coming from the LHC show no signs of new particles

or unexpected phenomena.

Of course, the verdict is not definitive.

當然,目前的論斷並不是絕對的

In 2015, the LHC will almost double

2015年,LHC對撞機將會加倍

the energy of the colliding protons,

質子撞擊的能量

and these more powerful collisions

這些更強烈的撞擊

will allow us to explore further the particle world,

能讓我們進一步了探索粒子世界

and we will certainly learn much more.

我們一定能從中知道更多

But for the moment, since we have found

但當下我們還沒找到新現象的證據

no evidence for new phenomena, let us suppose

讓我們假設我們今天知道的粒子

that the particles that we know today,

including the Higgs boson,

包含希格斯玻色子

are the only elementary particles in nature,

是自然界中僅有的基本粒子

even at energies much larger

即使它們能爆發的能量 比我們今天所知的多上更多

than what we have explored so far.

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

我們來看看這個假設會帶來什麼事

We will find a surprising and intriguing result

我們會發現宇宙驚奇又迷人的結果

about our universe, and to explain my point,

在我繼續解釋之前

let me first tell you what the Higgs is about,

先讓我說明希格斯玻色子是什麼

and to do so, we have to go back

要說明的話,我們必須回到

to one tenth of a billionth of a second

宇宙大爆炸之後的百億分之一秒

after the Big Bang.

And according to the Higgs theory,

根據希格斯理論

at that instant, a dramatic event took place

在那瞬間 一件非常戲劇化的事件在宇宙中發生

in the universe.

Space-time underwent a phase transition.

時空經歷轉變期

It was something very similar to the phase transition

這個轉變期 和水在零度以下結冰的過程非常像

that occurs when water turns into ice

below zero degrees.

But in our case, the phase transition

但這個例子裡

轉變期不是分子在物質裡的重新排列

is not a change in the way the molecules

are arranged inside the material,

but is about a change

而是時空結構的改變

of the very fabric of space-time.

During this phase transition, empty space

在這段轉變期,空間充滿物質

became filled with a substance

that we now call Higgs field.

就是我們說的希格斯場

And this substance may seem invisible to us,

這種物質我們可能看不見

but it has a physical reality.

但卻擁有物理性質

It surrounds us all the time,

它隨時環繞我們

just like the air we breathe in this room.

就像我們在這房間內呼吸的空氣一樣

And some elementary particles interact

有些基本粒子和這種物質互動 從過程中獲得能量

with this substance, gaining energy in the process.

And this intrinsic energy is what we call

這種內在的能量 就是我們今天說的粒子質量

the mass of a particle,

and by discovering the Higgs boson, the LHC

而藉由發現希格斯玻色子

LHC對撞機證實這種物質是真的

has conclusively proved that this substance is real,

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

因為希格斯玻色子正由這種物質組成

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

簡單來說,這就是希格斯故事的梗概

But this story is far more interesting than that.

但更有趣的在後頭

By studying the Higgs theory,

研究希格斯理論的同時

theoretical physicists discovered,

理論學家發現

not through an experiment

並非經由實驗,而只是數學演算

but with the power of mathematics,

that the Higgs field does not necessarily exist

他們發現希格斯場並不是 只以我們今日發現的形式存在

only in the form that we observe today.

Just like matter can exist as liquid or solid,

就像物質可以有液態和固態兩種狀態

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

所以希格斯場 也就是那填滿時空的物質

could exist in two states.

可以存在於兩種狀態下

Besides the known Higgs state,

除了已知的希格斯場之外

there could be a second state in which the Higgs field

希格斯場還可能比現在 所知的高出幾十億密度存在

is billions and billions times denser

than what we observe today,

and the mere existence of another state

光是另一種希格斯場的可能存在

of the Higgs field poses a potential problem.

就帶來了潛在的問題

This is because, according to the laws

因為根據量子力學定律

of quantum mechanics, it is possible

兩種狀態之間的轉變是有可能的

to have transitions between two states,

even in the presence of an energy barrier

即使兩個狀態之間有能量差間隔

separating the two states,

and the phenomenon is called,

詞如其名,這個現象被稱為量子穿隧

quite appropriately, quantum tunneling.

Because of quantum tunneling,

因為量子穿隧效應

I could disappear from this room

我可以從這間房間消失

and reappear in the next room,

再從另外一個房間出現

practically penetrating the wall.

簡單來說就是穿越牆壁

But don't expect me to actually perform the trick

但別期待我會真的在你們面前表演

in front of your eyes, because the probability

for me to penetrate the wall is ridiculously small.

因為讓我能穿越牆壁的機率十分渺小

You would have to wait a really long time

在這發生之前你們得等上好一陣子

before it happens, but believe me,

但相信我 量子穿隧是一個真實存在的現象

quantum tunneling is a real phenomenon,

and it has been observed in many systems.

且已經被很多機制發現

For instance, the tunnel diode,

例如,穿隧兩極真空管 一個在電子學中常用的組件

a component used in electronics,

works thanks to the wonders

因為量子穿隧效應而被製造出來

of quantum tunneling.

But let's go back to the Higgs field.

但讓我們再回到希格斯場

If the ultra-dense Higgs state existed,

如果超濃度的希格斯場存在

then, because of quantum tunneling,

那,因為量子穿隧效應

a bubble of this state could suddenly appear

在這狀態下的泡泡 可以突然出現在宇宙中的特定時空

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

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

就和我們煮滾水的時候一樣

Bubbles of vapor form inside the water,

蒸氣泡泡從水中蒸發

then they expand, turning liquid into gas.

然後膨脹,從液態變成氣態

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

同理,一顆泡泡在超濃度的希格斯場

could come into existence because of quantum tunneling.

可以因為量子穿隧效應而出現

The bubble would then expand at the speed of light,

泡泡會以光速膨脹,佔領空間

invading all space, and turning the Higgs field

將希格斯場從熟悉帶到全新的狀態

from the familiar state into a new state.

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

這是個問題嗎?

是,很大的問題

We may not realize it in ordinary life,

在日常生活中可能難以理解

but the intensity of the Higgs field is critical

但希格斯場的密度 對於物質構造非常重要

for the structure of matter.

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

如果希格斯場密度只是比一般高一點

we would see atoms shrinking, neutrons decaying

我們就會看到原子核中原子收縮

中子衰變,核子解體

inside atomic nuclei, nuclei disintegrating,

and hydrogen would be

氫會變成宇宙中 唯一可能存在的化學元素

the only possible chemical element in the universe.

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

而超濃度的希格斯場

is not just a few times more intense than today,

並不是只比今天的希格斯場 密度高上幾倍

but billions of times,

而是幾十億倍

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

如果時空被這個希格斯場填滿

all atomic matter would collapse.

所有原子物質都會崩解

No molecular structures would be possible, no life.

沒有任何分子結構能夠存在 沒有生命

So, I wonder, is it possible

所以我想

未來希格斯場有可能會經歷轉變期

that in the future, the Higgs field

will undergo a phase transition and,

through quantum tunneling, will be transformed

和量子穿隧效應

into this nasty, ultra-dense state?

進入這個恐怖,高濃度的狀態嗎?

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

換句話說,我問自己

希格斯場在宇宙中的命運是什麼?

of the Higgs field in our universe?

And the crucial ingredient necessary

而回答這個問題的關鍵 在於希格斯玻色子的質量

to answer this question is the Higgs boson mass.

And experiments at the LHC found that the mass

在一次LHC的實驗裡發現

of the Higgs boson is about 126 GeV.

希格斯玻色子的質量 是1260億電子伏特

This is tiny when expressed in familiar units,

用我們熟悉的單位表示的話其實不多

because it's equal to something like

差不多是10的負22次方公克

10 to the minus 22 grams,

but it is large in particle physics units,

但是對粒子單位來說很大

because it is equal to the weight

它就等於是整個DNA分子的重量

of an entire molecule

of a DNA constituent.

So armed with this information from the LHC,

有了從LHC得到的資料

together with some colleagues here at CERN,

再加上從歐洲核子研究組織得到的

we computed the probability

我們試著計算

that our universe could quantum tunnel

宇宙經過量子穿隧 進入高濃度希格斯場的可能性

into the ultra-dense Higgs state,

and we found a very intriguing result.

結果非常有趣

Our calculations showed

我們的計算顯示

that the measured value of the Higgs boson mass

希格斯玻色子的質量非常特別

is very special.

It has just the right value

它的質量剛剛好

to keep the universe hanging

可以讓宇宙處在一個不安定的狀態

in an unstable situation.

The Higgs field is in a wobbly configuration

希格斯場的結構至今為止 仍處於搖擺不定的狀態

that has lasted so far

but that will eventually collapse.

但最終還是會崩塌

So according to these calculations,

根據我們的計算

we are like campers

我們就像露營的人

who accidentally set their tent

不小心將帳篷搭在懸崖邊

at the edge of a cliff.

And eventually, the Higgs field

最後,希格斯場會經歷轉變期

will undergo a phase transition

and matter will collapse into itself.

然後所有的物質會自我毀滅

So is this how humanity is going to disappear?

所以人類文明就是這樣消失的嗎?

I don't think so.

我不這樣覺得

Our calculation shows that quantum tunneling

我們的計算顯示

of the Higgs field is not likely to occur

希格斯場的量子穿隧

在接下來的10年到100年 不太可能會發生

in the next 10 to the 100 years,

and this is a very long time.

這是一段很長的時間

It's even longer than

甚至比義大利成立穩定的政府還要長

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

(Laughter)

Even so, we will be long gone by then.

即使發生了,我們也已經不在了

In about five billion years,

在約50億年後

our sun will become a red giant,

太陽會變成紅巨星

as large as the Earth's orbit,

和地球繞日的軌跡一樣大

and our Earth will be kaput,

地球會毀掉

and in a thousand billion years,

1兆年之後

if dark energy keeps on fueling

如果黑暗能量還在供給

space expansion at the present rate,

太空依現在的速度膨脹

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

你連到腳趾頭這麼短的距離都看不到

because everything around you

因為你身邊的事物

expands at a rate faster than the speed of light.

都在以比光速還要快的速度膨脹

So it is really unlikely

所以要我們看到希格斯場膨脹 真的不怎麼可能

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

But the reason why I am interested

我對希格斯場轉換感興趣的原因是

in the transition of the Higgs field

is because I want to address the question,

因為我想問:

why is the Higgs boson mass so special?

為何希格斯玻色子的質量如此特別?

Why is it just right to keep the universe

為何它剛剛好讓宇宙

at the edge of a phase transition?

處於轉變的邊緣?

Theoretical physicists always ask "why" questions.

理論學家永遠喜歡問"為什麼"

More than how a phenomenon works,

不只是想要知道現象的成因

theoretical physicists are always interested in

理論學家更感興趣的是

why a phenomenon works in the way it works.

為何一個現象會以現在這個方式運作

We think that this these "why" questions

我們覺得這些"為什麼"可以給我們線索

can give us clues

about the fundamental principles of nature.

找尋自然的基本定律

And indeed, a possible answer to my question

而能解答我問題的可能答案

opens up new universes, literally.

開啟了整個宇宙 真的是字面上的開啟

It has been speculated that our universe

一直有人懷疑

我們的宇宙只是 眾多宇宙泡沫堆中的一個泡泡

is only a bubble in a soapy multiverse

made out of a multitude of bubbles,

眾多宇宙裡有數以萬計的泡泡

and each bubble is a different universe

每個泡泡都是一個不同的宇宙

with different fundamental constants

擁有不同的內容物

and different physical laws.

還有不同的定律

And in this context, you can only talk about

在這個假設下

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

我們只能討論確定希格斯質量的可能性

Then the key to the mystery

那麼解開謎團的關鍵

could lie in the statistical properties

就在這眾多宇宙中的統計特性

of the multiverse.

It would be something like what happens

它可能類似沙灘上的沙丘

with sand dunes on a beach.

In principle, you could imagine to find sand dunes

基本上你可以想像 在沙灘上的任何坡度找到沙丘

of any slope angle in a beach,

and yet, the slope angles of sand dunes

但是沙丘的坡度通常都在30到35度左右

are typically around 30, 35 degrees.

And the reason is simple:

原因很簡單

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

因為風堆起沙子,重力讓沙子掉下來

As a result, the vast majority of sand dunes

所以大部分的沙丘

have slope angles around the critical value,

都擁有剛好接近崩塌的斜度

near to collapse.

And something similar could happen

類似的事情也可能 發生於眾多宇宙中的希格斯玻色子

for the Higgs boson mass in the multiverse.

In the majority of bubble universes,

在眾多宇宙的泡泡中

the Higgs mass could be around the critical value,

希格斯的質量 可能也在希格斯場接近崩塌的邊緣

near to a cosmic collapse of the Higgs field,

because of two competing effects,

就像在沙丘的例子裡 有兩個互相抗衡的效應一樣

just as in the case of sand.

My story does not have an end,

我的故事不會結束

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

因為我們還不知道故事的結局

This is science in progress,

科學一直在前進

and to solve the mystery, we need more data,

為了解開謎團,我們需要更多數據

and hopefully, the LHC will soon add new clues

希望LHC不久後 又會為這個故事提供更多新線索

to this story.

Just one number, the Higgs boson mass,

光是發現希格斯玻色子的質量

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

就讓我們知道這麼多

I started from a hypothesis, that the known particles

我一開始假設 已知的粒子都在宇宙之中

are all there is in the universe,

even beyond the domain explored so far.

甚至超出我們所知的宇宙

From this, we discovered that the Higgs field

從這我們發現能跨越時空的希格斯場

that permeates space-time may be standing

可能處在刀鋒 隨時可能引起宇宙崩塌

on a knife edge, ready for cosmic collapse,

and we discovered that this may be a hint

我們發現這可能提醒我們

that our universe is only a grain of sand

我們的宇宙 只是眾多宇宙沙灘中的一顆沙粒

in a giant beach, the multiverse.

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

但我並不知道我的假設正不正確

That's how physics works: A single measurement

這就是物理學的運作方式

一套測量可將我們推向認識宇宙的新路

can put us on the road to a new understanding

of the universe

or it can send us down a blind alley.

也可以送我們進死胡同

But whichever it turns out to be,

但不論結果如何

there is one thing I'm sure of:

有一件事我很確定:

The journey will be full of surprises.

這趟旅程將會充滿驚喜

Thank you.

謝謝

(Applause)