A hundred years ago this month, a 36-year-old Albert Einstein stood up in front of the Prussian Academy of Sciences in Berlin to present a radical new theory of space, time and gravity: the general theory of relativity.
百年前的此月, 36 歲的愛因斯坦 在柏林普魯士科學院前 發表有關時空與重力的 開創性理論: 廣義相對論。
General relativity is unquestionably Einstein's masterpiece, a theory which reveals the workings of the universe at the grandest scales, capturing in one beautiful line of algebra everything from why apples fall from trees to the beginning of time and space.
這無疑是愛因斯坦的傑作, 揭露大尺度世界的運行法則, 以一則優美的公式囊括一切, 從為何蘋果會從樹上掉落 到時空的起源。
1915 must have been an exciting year to be a physicist. Two new ideas were turning the subject on its head. One was Einstein's theory of relativity, the other was arguably even more revolutionary: quantum mechanics, a mind-meltingly strange yet stunningly successful new way of understanding the microworld, the world of atoms and particles.
1915 年是令物理學家 興奮的一年, 兩個嶄新的觀念 在物理界掀起革命。 一是愛因斯坦的相對論, 另一個可說是 更革命性的量子力學。 這是一個十分艱深 但有效的新方法, 讓我們理解 原子與粒子的小尺度世界。
Over the last century, these two ideas have utterly transformed our understanding of the universe. It's thanks to relativity and quantum mechanics that we've learned what the universe is made from, how it began and how it continues to evolve. A hundred years on, we now find ourselves at another turning point in physics, but what's at stake now is rather different. The next few years may tell us whether we'll be able to continue to increase our understanding of nature, or whether maybe for the first time in the history of science, we could be facing questions that we cannot answer, not because we don't have the brains or technology, but because the laws of physics themselves forbid it.
上個世紀這兩個理論 完全顛覆我們對宇宙的認知。 多虧這兩個理論, 我們得以了解宇宙的 構成、形成與演進。 百年後的今日, 我們站在物理學新的轉捩點, 但情況與當時卻相當不同, 未來幾年或許會告訴我們 是否可以進一步加深 對自然的認知, 抑或將是科學史上首次 人類面臨無法解釋的問題, 不是因為缺乏足夠才智或科技, 而是物理定律阻止了我們。
This is the essential problem: the universe is far, far too interesting. Relativity and quantum mechanics appear to suggest that the universe should be a boring place. It should be dark, lethal and lifeless. But when we look around us, we see we live in a universe full of interesting stuff, full of stars, planets, trees, squirrels. The question is, ultimately, why does all this interesting stuff exist? Why is there something rather than nothing? This contradiction is the most pressing problem in fundamental physics, and in the next few years, we may find out whether we'll ever be able to solve it.
以下是主要問題: 宇宙實在太多采多姿, 相對論與量子力學卻暗示: 宇宙應該是很空寂的, 應該是黑暗、致命、無生氣的。 但當我們環顧四周, 會發現我們處於一個充滿 恆星、行星、樹木與 動物的新奇世界 。 最終,問題是: 為什麼有這些有趣的萬物存在? 為什麼是「有」,而不是「虛無」? 這個矛盾在基礎物理中 是最迫切的問題。 而在未來幾年, 我們也許會知道 是否有能力解決它。
At the heart of this problem are two numbers, two extremely dangerous numbers. These are properties of the universe that we can measure, and they're extremely dangerous because if they were different, even by a tiny bit, then the universe as we know it would not exist. The first of these numbers is associated with the discovery that was made a few kilometers from this hall, at CERN, home of this machine, the largest scientific device ever built by the human race, the Large Hadron Collider. The LHC whizzes subatomic particles around a 27-kilometer ring, getting them closer and closer to the speed of light before smashing them into each other inside gigantic particle detectors. On July 4, 2012, physicists at CERN announced to the world that they'd spotted a new fundamental particle being created at the violent collisions at the LHC: the Higgs boson.
在這問題的核心是兩個數字, 兩個極端危險的數字, 關乎兩項可以量測的宇宙特質。 它們非常危險, 因為假若它們之值 與現今有絲毫差異, 那我們所熟知的宇宙 便不復存在。 第一個數字與在 距此數公里之外的 歐洲核子研究組織(CERN)裡, 人類所建造最大的科學儀器── 大強子對撞機(LHC) 所做的發現有關。 LHC 在長達 27 公里的環中, 加速次原子粒子直至接近光速, 再使它們在巨型粒子探測器中對撞。 2012 年 7 月 4 日, CERN 的物理學家 向全世界宣告, 探測到新的基本粒子。 在 LHC 的一場 劇烈對撞中產生:
Now, if you followed the news at the time,
希格斯玻色子。
you'll have seen a lot of physicists getting very excited indeed, and you'd be forgiven for thinking we get that way every time we discover a new particle. Well, that is kind of true, but the Higgs boson is particularly special. We all got so excited because finding the Higgs proves the existence of a cosmic energy field. Now, you may have trouble imagining an energy field, but we've all experienced one. If you've ever held a magnet close to a piece of metal and felt a force pulling across that gap, then you've felt the effect of a field. And the Higgs field is a little bit like a magnetic field, except it has a constant value everywhere. It's all around us right now. We can't see it or touch it, but if it wasn't there, we would not exist. The Higgs field gives mass to the fundamental particles that we're made from. If it wasn't there, those particles would have no mass, and no atoms could form and there would be no us.
如果你當時有關注這個消息, 你會發現許多物理學家十分興奮。 而你也會覺得, 每次物理學家 發現新粒子都是如此, 沒錯。 但希格斯玻色子格外特別, 我們如此興奮是因為 發現希格斯玻色子, 意味著宇宙能量場的存在。 你可能無法想像一個能量場, 但我們都有這種經驗: 如果你拿一個磁鐵靠近金屬片, 會感覺到之間有一股無形的拉力, 那麼你就是感受到場的效應。 希格斯場有點類似磁場, 但它在任何地方都是常數, 它就在我們四周, 我們無法看或感受它, 但倘若它不存在, 我們便不存在。 希格斯場給予構成 我們的基本粒子質量, 如果它不存在, 這些粒子便沒有質量, 原子無法形成, 也就不會有你我。
But there is something deeply mysterious about the Higgs field. Relativity and quantum mechanics tell us that it has two natural settings, a bit like a light switch. It should either be off, so that it has a zero value everywhere in space, or it should be on so it has an absolutely enormous value. In both of these scenarios, atoms could not exist, and therefore all the other interesting stuff that we see around us in the universe would not exist. In reality, the Higgs field is just slightly on, not zero but 10,000 trillion times weaker than its fully on value, a bit like a light switch that's got stuck just before the off position. And this value is crucial. If it were a tiny bit different, then there would be no physical structure in the universe.
但關於希格斯場有個謎團, 相對論與量子力學說 它有兩種自然狀態。 有點像是電燈開關, 不是關── 也就是說它到處的值都是零, 就是開── 也就是說它到處都是個巨大定值。 在這兩個情況下原子都無法存在, 也因此這世上我們所見 一切有趣事物將不存在。 事實上 希格斯場是稍稍打開的, 不是零,而是 開的值的一萬兆分之一, 有點像是卡在 「關」前面一點的電燈開關。 這個值十分重要, 若它與此值有絲毫不同, 在宇宙中將不會有任何物理結構,
So this is the first of our dangerous numbers, the strength of the Higgs field. Theorists have spent decades trying to understand why it has this very peculiarly fine-tuned number, and they've come up with a number of possible explanations. They have sexy-sounding names like "supersymmetry" or "large extra dimensions." I'm not going to go into the details of these ideas now, but the key point is this: if any of them explained this weirdly fine-tuned value of the Higgs field, then we should see new particles being created at the LHC along with the Higgs boson. So far, though, we've not seen any sign of them.
這就是第一個危險的數字, 希格斯場的強度。 理論學家花了 幾十年的時間嘗試理解, 為何是如此詭異精微的數值? 他們提出許多可行的解釋, 它們有酷炫的名字如 超對稱或巨大額外維度。 我不會討論這些想法的細節, 但重點是: 若它們真的解釋 怪異的希格斯場強度。 那麼在 LHC 中我們應會觀察到 新粒子伴隨希格斯玻色子產生, 但至今為止我們一無所獲。
But there's actually an even worse example of this kind of fine-tuning of a dangerous number, and this time it comes from the other end of the scale, from studying the universe at vast distances. One of the most important consequences of Einstein's general theory of relativity was the discovery that the universe began as a rapid expansion of space and time 13.8 billion years ago, the Big Bang. Now, according to early versions of the Big Bang theory, the universe has been expanding ever since with gravity gradually putting the brakes on that expansion. But in 1998, astronomers made the stunning discovery that the expansion of the universe is actually speeding up. The universe is getting bigger and bigger faster and faster driven by a mysterious repulsive force called dark energy.
然而還有關於這種 精細危險數字的更慘例子。 這次它來自另一個極端尺度: 大尺度下的宇宙學。 愛因斯坦廣義相對論, 最重要的結論之一是 發現在 138 億年以前, 因時空急速膨脹而生成宇宙, 這就是大霹靂。 根據大霹靂學說的早期版本, 宇宙一直在膨脹, 而重力使其膨脹速逐漸減緩。 但在 1998 年, 天文學家發現一件驚人的事實: 宇宙正在加速膨脹! 宇宙之所以加速擴張, 乃是受一種稱為暗能量的 神祕斥力所驅使。
Now, whenever you hear the word "dark" in physics, you should get very suspicious because it probably means we don't know what we're talking about.
在物理學當你聽到「暗」時, 你要有警覺心, 因為這很可能意味著 我們不知道自己在說什麼。
(Laughter)
(笑聲)
We don't know what dark energy is, but the best idea is that it's the energy of empty space itself, the energy of the vacuum. Now, if you use good old quantum mechanics to work out how strong dark energy should be, you get an absolutely astonishing result. You find that dark energy should be 10 to the power of 120 times stronger than the value we observe from astronomy. That's one with 120 zeroes after it. This is a number so mind-bogglingly huge that it's impossible to get your head around. We often use the word "astronomical" when we're talking about big numbers. Well, even that one won't do here. This number is bigger than any number in astronomy. It's a thousand trillion trillion trillion times bigger than the number of atoms in the entire universe.
我們不知道什麼是暗能量, 但最好的解釋是: 它是空無空間的能量、 真空的能量。 如果你用舊的量子力學 計算暗能量的強度, 你會得到驚人的結果。 你會發現它的值應該是 我們在天文學觀察到的值, 再乘以10 的 120 次方。 就是 1 後面加 120 個 0。 這個數字如此龐大, 以至於你的腦袋會當機。 我們常用「天文數字」 來描述巨大數字, 但在這兒卻不管用, 因為它比天文學裡的任何數字還大。 它是整個宇宙原子數量的 一千兆兆兆倍,
So that's a pretty bad prediction. In fact, it's been called the worst prediction in physics, and this is more than just a theoretical curiosity. If dark energy were anywhere near this strong, then the universe would have been torn apart, stars and galaxies could not form, and we would not be here. So this is the second of those dangerous numbers, the strength of dark energy, and explaining it requires an even more fantastic level of fine-tuning than we saw for the Higgs field. But unlike the Higgs field, this number has no known explanation.
所以這是個很差勁的預估。 事實上它被稱為 物理史上最糟的預估。 而這不單是理論上的事, 若暗能量到處都是如此強, 宇宙早就被撕碎了, 星星與星系也不會形成, 我們也不會存在。 這就是第二個危險的數字: 暗能量強度。 解釋它需要比我們在 希格斯場見到的 更加精細的微調。 但與希格斯場不同的是, 對於這個數字 沒有任何已知的解釋,
The hope was that a complete combination of Einstein's general theory of relativity, which is the theory of the universe at grand scales, with quantum mechanics, the theory of the universe at small scales, might provide a solution. Einstein himself spent most of his later years on a futile search for a unified theory of physics, and physicists have kept at it ever since.
而希望繫於: 愛因斯坦的相對論── 即大尺度描述宇宙的理論, 與量子力學── 小尺度描述宇宙的理論, 兩者的大一統可以提供解答, 愛因斯坦晚年大多時間致力於 大一統論的尋找,但並未成功。 而往後的物理學家也是如此。
One of the most promising candidates for a unified theory is string theory, and the essential idea is, if you could zoom in on the fundamental particles that make up our world, you'd see actually that they're not particles at all, but tiny vibrating strings of energy, with each frequency of vibration corresponding to a different particle, a bit like musical notes on a guitar string.
其中一個較有希望的候選者是弦論, 它的主要思想是: 如果你能極近觀察 構成世界的基本粒子, 你會發現它們根本不是粒子, 而是細小振動的能量弦。 不同的振動頻率對應不同的粒子。 有點像是吉他弦的音階,
So it's a rather elegant, almost poetic way of looking at the world, but it has one catastrophic problem. It turns out that string theory isn't one theory at all, but a whole collection of theories. It's been estimated, in fact, that there are 10 to the 500 different versions of string theory. Each one would describe a different universe with different laws of physics. Now, critics say this makes string theory unscientific. You can't disprove the theory. But others actually turned this on its head and said, well, maybe this apparent failure is string theory's greatest triumph. What if all of these 10 to the 500 different possible universes actually exist out there somewhere in some grand multiverse? Suddenly we can understand the weirdly fine-tuned values of these two dangerous numbers. In most of the multiverse, dark energy is so strong that the universe gets torn apart, or the Higgs field is so weak that no atoms can form. We live in one of the places in the multiverse where the two numbers are just right. We live in a Goldilocks universe.
這是以極高雅甚至如詩的方式 來看這個世界。 但它有個致命傷: 弦論根本不是一個理論, 而是許多理論的集合, 事實上估計約有 十至五百個不同的弦論, 每一個都描述不同的宇宙 與不同的物理定律。 批評者表示這使弦論不科學, 你無法證明它的對錯。 但有人腦筋一轉說: 或許這顯見的失敗是 弦論最大的成功。 若這十至五百個理論描述的宇宙, 確實在多重宇宙的某處存在, 剎那間我們就可以解釋 那兩個怪異精細的危險數字。 在多重宇宙大多地方, 暗能量太強以致宇宙會被撕裂, 或希格斯場太弱以致原子無法形成。 我們在多重宇宙的一隅, 剛好這兩數字是恰當的。 我們住在「金髮宇宙」 (適當的宇宙)。
Now, this idea is extremely controversial, and it's easy to see why. If we follow this line of thinking, then we will never be able to answer the question, "Why is there something rather than nothing?" In most of the multiverse, there is nothing, and we live in one of the few places where the laws of physics allow there to be something. Even worse, we can't test the idea of the multiverse. We can't access these other universes, so there's no way of knowing whether they're there or not.
這個想法十分具爭議性, 原因十分簡單, 如果我們順著這條思路, 那我們永遠無法回答以下問題: 為什麼是「有」而不是「虛無」? 在多重宇宙大多處什麼也沒有, 我們住在其中一個少數地方, 剛好物理定律允許存在物質。 更糟的是我們無法 檢驗多重宇宙的想法, 我們無法去其他宇宙, 所以無法得知它是否存在。
So we're in an extremely frustrating position. That doesn't mean the multiverse doesn't exist. There are other planets, other stars, other galaxies, so why not other universes? The problem is, it's unlikely we'll ever know for sure. Now, the idea of the multiverse has been around for a while, but in the last few years, we've started to get the first solid hints that this line of reasoning may get born out. Despite high hopes for the first run of the LHC, what we were looking for there -- we were looking for new theories of physics: supersymmetry or large extra dimensions that could explain this weirdly fine-tuned value of the Higgs field. But despite high hopes, the LHC revealed a barren subatomic wilderness populated only by a lonely Higgs boson. My experiment published paper after paper where we glumly had to conclude that we saw no signs of new physics.
所以我們處於一種令人氣餒的狀況。 但那不代表多重宇宙不存在, 既然有其他行星、恆星與星系, 為何其他宇宙不行? 問題是我們不太可能 證實它的真實性。 多重宇宙的想法已經出現一陣子。 在最近幾年 我們開始有幾個較具體的跡象, 顯示這條思路或許行得通。 儘管對第一次 LHC 運行的高度期待, 我們在尋找新的物理理論: 超對稱或巨大額外維度, 以解釋詭異精細的希格斯場強度。 但儘管高度期待, LHC 顯示出只有希格斯波色子的 荒涼次原子世界。 我的實驗報告 一篇接著一篇都寫著, 我們遺憾宣布沒有新物理的跡象。
The stakes now could not be higher. This summer, the LHC began its second phase of operation with an energy almost double what we achieved in the first run. What particle physicists are all desperately hoping for are signs of new particles, micro black holes, or maybe something totally unexpected emerging from the violent collisions at the Large Hadron Collider. If so, then we can continue this long journey that began 100 years ago with Albert Einstein towards an ever deeper understanding of the laws of nature.
危機指數已經到達頂端。 這個夏天 LHC 開始第二次運作, 能量幾乎是第一次的兩倍。 粒子學家迫切希望的 是新粒子、微型黑洞 或完全意料之外的訊號, 從 LHC 激烈碰撞中產生。 倘若如此,我們便可以繼續這趟 由愛因斯坦開始的、 超過百年的旅程, 朝著對自然律更深刻的認知邁進。
But if, in two or three years' time, when the LHC switches off again for a second long shutdown, we've found nothing but the Higgs boson, then we may be entering a new era in physics: an era where there are weird features of the universe that we cannot explain; an era where we have hints that we live in a multiverse that lies frustratingly forever beyond our reach; an era where we will never be able to answer the question, "Why is there something rather than nothing?"
但若兩三年下來, 在 LHC 第二次長期關機前, 我們除了希格斯玻色子外一無所獲。 那麼我們或許 就進入新的物理紀元: 一個有我們無法解釋現象的時代。 一個有跡象顯示我們活在 我們能力範圍外的多重宇宙時代。 一個我們永遠無法回答 為什麼是「有」 而不是「虛無」的時代。
Thank you.
謝謝!
(Applause)
(掌聲)
Bruno Giussani: Harry, even if you just said the science may not have some answers, I would like to ask you a couple of questions, and the first is: building something like the LHC is a generational project. I just mentioned, introducing you, that we live in a short-term world. How do you think so long term, projecting yourself out a generation when building something like this?
布魯諾:哈利,即使你剛有說 科學或許有無法解釋的事情, 我還是想問你幾個問題: 第一個是 建造像 LHC 是一個世代的計畫, 剛介紹你時我有提到, 我們活在短週期的世界裡, 你對這個世代的人花這麼多時間 建造這樣的機器有什麼看法?
Harry Cliff: I was very lucky that I joined the experiment I work on at the LHC in 2008, just as we were switching on, and there are people in my research group who have been working on it for three decades, their entire careers on one machine. So I think the first conversations about the LHC were in 1976, and you start planning the machine without the technology that you know you're going to need to be able to build it. So the computing power did not exist in the early '90s when design work began in earnest. One of the big detectors which record these collisions, they didn't think there was technology that could withstand the radiation that would be created in the LHC, so there was basically a lump of lead in the middle of this object with some detectors around the outside, but subsequently we have developed technology. So you have to rely on people's ingenuity, that they will solve the problems, but it may be a decade or more down the line.
哈利:我很幸運在 2008 年 當一切剛開始起步時, 便加入這個研究團隊。 這個團隊中有研究它 超過三十年的人, 他們人生全投入在這機器上。 我想第一次有關 LHC 的談話 是在 1976 年。 在沒有所需科技來建造它的狀況下, 人們開始設計它。 90 年代初期 設計工作認真開始時 電腦運算能力還嚴重不足, 其中一個偵測這些碰撞的偵測器, 當時他們不認為有科技 可以抵抗 LHC 內部 形成的輻射, 所以原本在這中間有一塊鉛, 偵測器則散佈四周, 但後來我們有發展出新科技。 我們必須依賴人們的聰慧, 一切問題會被解決, 只是可能是十年或更久之後。
BG: China just announced two or three weeks ago that they intend to build a supercollider twice the size of the LHC. I was wondering how you and your colleagues welcome the news.
布:兩三個星期前中國宣布 他們計畫建造一個 比 LHC 大兩倍的超級對撞機, 我想知道你與同事們 對這新聞的看法。
HC: Size isn't everything, Bruno. BG: I'm sure. I'm sure.
哈:布魯諾,大小不代表一切。
(Laughter)
布:我知道、我知道。
It sounds funny for a particle physicist to say that. But I mean, seriously, it's great news. So building a machine like the LHC requires countries from all over the world to pool their resources. No one nation can afford to build a machine this large, apart from maybe China, because they can mobilize huge amounts of resources, manpower and money to build machines like this. So it's only a good thing. 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 as to whether these new ideas, like supersymmetry, are really out there, so it's great news for physics, I think.
(笑聲) 聽粒子物理學家這樣說蠻有趣的。 不過認真地,它是個好消息! 建造像 LHC 的機器 需要全世界國家的投入, 沒有國家可以負擔如此的花費, 或許除了中國。 因為他們可以動用 大量資源、人力、金錢 來建造這樣的機器。 所以這是好消息吧! 他們計畫建造的是 可以詳細研究 希格斯玻色子並給我們 像是超對稱的新想法 是否為真的線索。 所以我想對物理界來說是好消息。
BG: Harry, thank you. HC: Thank you very much.
布:謝謝 哈:謝謝
(Applause)
(掌聲)