And there are some really big questions that we need answers to. Our current theory of what the world is made from down at the fundamental level is known as the “standard model” of particle physics—a deceptively boring name for one of humankind’s greatest intellectual achievements. Developed over decades through the combined efforts of thousands of theorists and experimentalists, the standard model says that everything we see around us—galaxies, stars, planets, and people—is made of just a few different types of particles, which are bound together inside atoms and molecules by a small number of fundamental forces. It’s a theory that explains everything from why the Sun shines to what light is and why stuff has mass. What’s more, it’s passed every experimental test we’ve been able to throw at it for almost half a century. It is, without a doubt, the most successful scientific theory ever written down.
All that said, we know that the standard model is wrong, or at the very least seriously incomplete. When it comes to the deepest mysteries facing modern physics, the standard model simply shrugs or offers up a bunch of contradictions instead of answers. Take this for starters. After decades of painstakingly peering into the heavens, astronomers and cosmologists are pretty well convinced that 95 percent of the universe is made of two invisible substances known as “dark energy” and “dark matter.” Whatever they are—and to be clear we haven’t got much of a clue about either of them—they’re definitely not made from any of the particles in the standard model. And as if missing 95 percent of everything wasn’t bad enough, the standard model also makes the rather startling assertion that all the matter in existence should have been wiped out in a cataclysmic annihilation with antimatter in the first microsecond of the big bang, leaving a universe with no stars, no planets, and no us.
So it’s pretty obvious that we are missing something big, most likely in the form of some as-yet-undiscovered fundamental particles that could help explain why the universe is the way it is.
How to Make an Apple Pie from Scratch: In Search of the Recipe for Our Universe, from the Origins of Atoms to the Big Bang
by Harry Cliff
In How to Make an Apple Pie from Scratch, Harry Cliff—a University of Cambridge particle physicist and researcher on the Large Hadron Collider—sets out in pursuit of answers. He ventures to the largest underground research facility in the world, deep beneath Italy’s Gran Sasso mountains, where scientists gaze into the heart of the Sun using the most elusive of particles, the ghostly neutrino. He visits CERN in Switzerland to explore the “Antimatter Factory,” where the stuff of science fiction is manufactured daily (and we’re close to knowing whether it falls up). And he reveals what the latest data from the Large Hadron Collider may be telling us about the fundamental nature of matter.
Along the way, Cliff illuminates the history of physics, chemistry, and astronomy that brought us to our present understanding—and misunderstandings—of the world, while offering readers a front-row seat to one of the most dramatic intellectual journeys human beings have ever embarked on.
A transfixing deep dive into the origins of our world, How to Make an Apple Pie from Scratch examines not just the makeup of our universe, but the awe-inspiring, improbable fact that it exists at all.
物質は何からできているのか アップルパイのレシピから素粒子を考えてみた
by ハリー クリフ
translated by 熊谷 玲美
著者は、自らが子どものころに行ったアップルパイの分析実験から始まり、元素とは何かについて古代ギリシャの考え方を紹介し、18世紀のラヴォアジエが化学元素（当時は物質の構成要素は物理学ではなく化学の扱う分野だった）の概念を生み出したことを説明する。その当時は古代ギリシャの元素である土、水、空気、火からなる四元素（と熱さ、冷たさ、乾き、潤いという四つの質の概念があった）という考え方が主流であり、それぞれがお互いに変化するものという認識だった。つまり水（冷たく湿っている）に熱を加えれば空気（熱く湿っている）になるというような相互変換である。これは18世紀になるまで引き継がれており、この考えを否定するところから新しい化学は始まることになった。具体的には水から土への変換はしないというようなことである（それまでは水を煮詰めると黒いものが残り、これが土であるという認識）。それからフロギストン（火をつけると発生すると思われていたもの）の話、水素に酸素を加えて水になる話（これでギリシャ時代の水から土は否定される）などと展開していく。あとの章では元素は分子ではなく原子であることを証明していくアインシュタイン、さらに小さな原子核や電子の発見、その振る舞い、もっと分解して陽子、素粒子とどんどん小さくなっていく。こうして物質が何からできているのか、今わかっていること、わからないことをつまびらかに述べる。こうした話を身近な話題に関連して取りあげつつ、これらの発見を誰がして、当初どのように受け入れられ、あるいは無視されながら事実に近づきつつ証明されてきたのか、その経緯を歴史的に、その前後の人々の認識を絡めて段階的（年代的にも物質の大きさ的にも）に語る形式を取っている。
弦理論の問題点とは？ 自然の基本法則を完全に理解できるのか？ スファレロンとは何か？ ヒッグス粒子どうやって見つかったか？ ヒッグス場とは何か？ 反物質はどうやって作るのか？ 超対称性とは何か？ などこの分野の最新の成果を盛り込みつつ、素粒子物理学というとっつきにくい内容を、身近な物質とその成分の発見の歴史をとおして、肉眼世界からミクロの世界へと、最新の研究成果をわかりやすく語っていく。ちなみに素粒子物理学は宇宙の基本的物質の探求（ニュートリノの反粒子の研究など、ノーベル賞の小柴さんや梶田さんが関連する研究）や、その終わりにかかわるダークマターやダークエネルギーなどの最新の宇宙研究にもつながっていることがわかる。
… glory days of physics were over, the quantum revolution was done, and the time wasn’t yet ripe for new breakthroughs. If the ambitious young man wanted to make his mark on science, he should look elsewhere. So Fred Hoyle turned his attention to the stars. During his long and eclectic career, Hoyle became famous for his contrarian, sometimes wacky scientific views, bitter disputes with fellow academics, and as a talented writer of science fiction, including the smash-hit BBC television series A for Andromeda. Today, he’s probably best known as a die-hard opponent of the big bang theory, which he dismissed as pseudoscience thanks to its inability to explain what actually caused it to happen in the first place.
Have we reached the end of physics?
Harry Cliff
https://www.ted.com/talks/harry_cliff_have_we_reached_the_end_of_physics
Why is there something rather than nothing? Why does so much interesting stuff exist in the universe? Particle physicist Harry Cliff works on the Large Hadron Collider at CERN, and he has some potentially bad news for people who seek answers to these questions. Despite the best efforts of scientists (and the help of the biggest machine on the planet), we may never be able to explain all the weird features of nature. Is this the end of physics? Learn more in this fascinating talk about the latest research into the secret structure of the universe.
Transcript:
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.
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.
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.
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.
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.
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.
Now, if you followed the news at the time, 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?”
Thank you.
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?
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.
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.
HC: Size isn’t everything, Bruno. BG: I’m sure. I’m sure.
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.
2024年5月3日（金）
物理学は終わったのか？
今週の書物/
『How to Make an Apple Pie from Scratch』
Harry Cliff 著、Doubleday、2021年刊
物理学から「わくわく」が消えたような気がする。
私たちの住むこの世界は4次元（3次元空間＋時間）ではなく、実は10次元（9次元空間＋時間）だったと言われても、素直に「はい、そうですか」とは言えない。理論とか仮説とかが次から次へと現れては消えてゆく。
今週は、そんな物理学の現状を整理する一冊。『How to Make an Apple Pie from Scratch』（Harry Cliff 著、Doubleday、2021年刊）だ。『In Search of the Recipe for Our Universe, from the Origins of Atoms to the Big Bang』という副題がついている。日本語訳も出版されている。『物質は何からできているのか』（ハリー・クリフ著、熊谷玲美訳、柏書房、2023年刊）で、こちらには『アップルパイのレシピから素粒子を考えてみた』という副題がついている。