기초 물리학의 위기: 아름다움의 딜레마

### 기초 물리학의 아름다움의 위기: 방법론적 개혁에 대한 요구
* 🔬 제네바의 대형 강입자가속기(LHC)는 **2012년 입자 물리학 표준 모델에서 마지막으로 사라진 입자인 힉스 입자**를 발견해 화제가 된 바 있습니다.
* 🎉 LHC를 둘러싼 흥분에도 불구하고 많은 사람들이 **초대칭 입자나 평행 우주와 같은 추가 현상**을 발견할 것으로 기대했지만 결국 실현되지 않았고, 이러한 예측에 대한 물리학자들의 신뢰도에 의문을 제기했습니다.
* 📉 일반 상대성 이론과 표준 모형이라는 두 가지 주요 이론이 탄생한 이래로 크게 발전하지 못하면서 많은 의문이 풀리지 않고 **"위기"로 인식**되는 등 기초 물리학의 정체는 분명합니다.
* 🌀 양자역학과 일반 상대성 이론 사이의 단절은 물리학자들이 입자의 양자 특성과 중력 효과를 조화시키기 위해 고군분투하면서 **양자 중력 이론의 필요성**을 강조하는 중요한 과제를 제시합니다.
* ⚖ 물리학에서 아름다움을 추구하는 것은 역사적으로 이론 발전에 영향을 미쳤으며, 많은 물리학자들은 **"아름다운 이론이 맞을 가능성이 높다"**고 믿었지만 이러한 접근 방식은 지난 40년 동안 수많은 잘못된 예측과 발전의 부재로 이어졌습니다.
* 🔍 과학 이론 개발의 기준으로서 아름다움을 비판적으로 검토한 결과, **기존 이론의 근본적인 모순을 해결하기보다는 주관적인 해석과 미적 문제에 초점**을 맞추는 경우가 많다는 사실이 밝혀졌습니다.
* 💡 진정한 발전을 도모하기 위해 물리학자들은 **수학적 불일치를 해결하는 데 우선순위**를 두고, 과학적 방법에는 일반적인 규범을 고수하기보다는 객관적인 분석이 필요하다는 점을 인식하여 **아름다움에 대한 의존을 원칙으로 재평가**해야 합니다.
* 📊 궁극적으로 기초 물리학의 방법론을 개혁하는 것은 침체의 고리를 끊고 **획기적인 발견으로 이어질 수 있는 새로운 가설에 대한 탐구**를 장려하는 데 필수적입니다.

이론 물리학자들은 새로운 이론을 개발할 때 결함이 있는 미적 기준에 의존해 정체기에 갇혀 있습니다.

The Large Hadron Collider in Geneva is currently the largest particle accelerator in the world. I assume you all have already heard about it. In the year 2012, the so-called Higgs boson was discovered there. The Higgs boson is the last missing particle in the so-called Standard Model of particle physics. You can probably remember the headlines in the newspapers - The physicists were very happy, there were celebrations, champagne was opened. Many of you probably also remember that before the Large Hadron Collider was turned on, we heard a lot about other things that it was supposed to find; besides the Higgs boson, for example, the so-called super-symmetric partner particles (sparticles). Other people talked about small black holes that it might have created, or gravitons. These were some of the things people talked about; additional dimensions of space were mentioned. Others noted that we might make contact with parallel universes. None of these came true.

One wonders why so many physicists, in particular the theoretical physicists, were so convinced that the Large Hadron Collider should have seen other things besides the Higgs boson. The answer is that they thought the universe should be beautiful in a particular way. And in my talk today, I hope to explain to you exactly what went wrong. Before I do anything else, I have to say exactly what I'm talking about. Physics is a very large area; it has many subsections. There is solid-state physics, statistical mechanics, nuclear physics, atomic physics, physics of condensed matter, optics, quantum optics, and so on and on. These are all areas that I will not talk about today. I will only talk about the very basics of physics. In fundamental physics, we deal with those laws of nature that cannot be derived from some more basic theories. We currently have two theories in this area. This is, on the one hand, the general relativity theory which was derived from Einstein.

General relativity theory describes the curvature of space and time, and thereby the gravitational force is produced. The other theory we have is the so-called standard model of particle physics that describes the elementary building blocks of matter and their interaction. The standard model of particle physics has 25 particles - the Higgs boson was, as mentioned before, the last missing particle. To understand this talk, you do not have to know exactly what this standard model is about, but these are the two theories that we use at the moment in these areas. What has happened in basic physics in the last decade? Not a lot. They talk about a crisis there, a crisis at the edge of physics. This has something to do with supersymmetry, crisis at the foundations of physics... Could there be a crisis in physics? Another crisis in physics? Is there a crisis in theoretical physics? Well, by now I have the impression that there is, and this one I like the most. This is a new article.

published in the New Scientist in January this year - We'll die before we find the answer. This is a quote from Neil Turok, currently the director of the Perimeter Institute in Canada, one of the world's most famous institutes where research on the topic of the foundation of physics is done. I don't particularly like it when this is called a crisis because crisis sounds so optimistic, as if the physicists had understood that something has gone wrong and are rethinking now. But that is not the case, so I prefer to talk about a stagnation. Simply nothing is happening. General relativity theory is more than 100 years old. The development of the standard model was completed in the seventies. Since then, of course, more has been done on the experimental side. As said, the Higgs boson was the last particle that we found. In the nineties, some more particles were added to the standard model. We also found in the late 90s

that the so-called cosmological constant is not zero, which was long assumed. They have noticed that the neutrinos have mass, but the theories that correspond to this, they have been around for more than 40 years. The cosmological constant was originally introduced by Einstein, the theory of the Higgs boson is from the 60s, the theory for the neutrino mass from the 50s. Since the 70s, the mathematical structure of these theories has not changed. But it's not that we say okay, we're done with the basics of physics, bye, let's go home. We know that's not the case. We still have questions for which we want answers. As you probably noticed, on the first slide I had general relativity theory next to the standard model and not together. That is because these two theories do not work together. Seeing the problem is relatively easy, but to solve it is very difficult.

The problem briefly summarized is that we know that all the particles in the standard model have quantum properties. In particular, they are subject to the Heisenberg uncertainty principle and can do strange things like be in two places at the same time. We also know that all particles that have mass or energy generate a gravitational field. Then the question arises, when you have two particles in two places at the same time, where does the gravitational attraction go? Now you could say okay the gravitational attraction should also be in both places at the same time... But you cannot do that with general relativity theory because this theory has no quantum properties. To answer this question you therefore need a theory of quantum gravitation, that gives quantum properties to gravitation, or, because Einstein told us, gravitation actually is the curvature of space and time itself, we need a theory for the quantum properties of space and time. This problem is known since the 30s. We have no solution yet.

but there are other problems with the basics of physics. For example, there is the so-called dark matter. There are plenty of observations from astrophysics that we are not understanding something in the cosmos as a whole. One way to explain these observations is to postulate that there are additional particles that are not included in the standard model, particles of the so-called dark matter. Dark, because you cannot see it. That is one possibility to explain our observations. Especially particle physicists like the idea that dark matter is made of particles. The other possibility to explain the observation is to change something about general relativity theory so that the gravitation of known masses is larger. Then we have other questions. For example, how did the universe begin the story with the Big Bang, you probably occasionally hear lectures about it here. So we know we are not finished yet and yes they are difficult questions. That is very clear, physics is one of the oldest areas of science, and the simple things

have just been done. It is therefore expected that progress slows; that is not too surprising. There is also another reason why I do not find these talks about a crisis very helpful. How do we actually know if we are in a crisis? We have no parallel universe with which we could compare to. Actually, I think a better question is: Are the physicists doing the best they could do? And the answer to that is, in my opinion, NO, because they focus on the wrong problems. What happened? I will do my best to give you a short historical summary. I am not a historian, but since my book has been published, I have had many conversations with philosophers and historians who told me I did a decent job, so I am relatively confident that it is not complete nonsense what I am about to tell you. We'll start here with Newton. For Newton, the beauty of the laws of nature was a sign of divine influence. For example, he wrote

This beautiful system of the Sun, planets, and comets could only originate from the counsel and reign of an intelligent being. For the scientists at that time, the idea was commonplace that God, of course, has created everything, and God is good, and that is why nature is beautiful, and of course, the laws of nature must also be beautiful. Over time, this reference to God fell out of the sciences. I skip now 300 years and come to Henri Poincaré. For him, the beauty of the laws of nature was a bonus of his profession. He wrote: The scientist studies nature not because it is useful. He studies it because he enjoys it, and he enjoys it because it is beautiful. The next step was made by Hermann Weyl. For him, the beauty of the laws of nature was a guide. Hermann Weyl was not really a physicist but was a mathematician, but he has made a lot of contributions to general relativity theory and also to Gauge theory, which is

still used in the Standard Model. He wrote, My work always attempts to unite the true with the beautiful, but if I had to choose one of them, I usually would choose the beautiful. Then we have Paul Dirac. He won a Nobel Prize for the so-called Dirac equation. He made beauty a prescription for the physicist. He wrote, The researcher, in his endeavor to express the fundamental laws of nature in mathematical form, should primarily strive for mathematical beauty. And the more successful the physicists were, the more convinced they became that they can understand nature through self-analysis. Physicists got this impression that when they rely on their own sense for beauty, they can guess the laws of nature. For example, here we have Albert Einstein, who of course must not be missed here. I am convinced that through pure mathematical construction, we are able to find those terms and those lawful connections between them that are the key to understanding the natural phenomenon.

In a sense, I therefore consider it true that pure thought is able to capture truth, as the old ones have dreamed. This is a bit unfair to Einstein, as in other places he clearly pointed out that one needs contact with observations in science. With that, I leave those that have already died behind and come to those that are still alive. I will begin with Anthony Zee. And Anthony Zee is a professor of physics at the University of California in Santa Barbara. He wrote a book in the 80s about the use of symmetries in theoretical physics, and in this book he writes, My colleagues and I are the intellectual offspring of Albert Einstein. We like to think that we also search for beauty. So here you see how this idea that beauty is a good path for the development of natural laws is passed from one generation to the next. Steven Weinberg has won a Nobel Prize for the co-development of the Standard Model.

of particle physics. In the 90s years, he wrote a book called Dreams of a Final Theory. In the book, he tells a story of a horse breeder who looks at a horse and says, this is a beautiful horse. Hereby, he might express a purely aesthetic impression, but I think there is more to it. The horse breeder has seen many horses and knows from experience that such a horse wins races. What he explains here is that this trust in our sense of beauty in theory development is actually based on experience. We have already learned from the theories we already met what works, and this we now see as beautiful, and we can then continue in the future. That's true in principle, of course, but only works as long as the theories that you want to develop use the same math; otherwise, this sense of beauty derived from experience will not help you further. Here we have another Nobel Prize winner, Murray Gell-Mann.

He won a Nobel prize for the development of the quarks mode. Quarks are also elementary particles not included in the Standard Model, and he said the following in one TED Talk you can find online: What is especially noticeable and remarkable is that in fundamental physics, a beautiful and elegant theory has a greater probability to be correct than an inelegant one. What I find especially noticeable and remarkable is that a scientist makes such statements without any evidence whatsoever. And then I have here one last quote from Robert Dijkgraaf. Robert Dijkgraaf is currently the director of the Institute for Advanced Study in Princeton. He is a theorist and has written the following: Once you understand the language in which the Universe is written, it is extremely elegant, beautiful, powerful, and natural. The universe wants to be understood, and that's why we all are driven by the urge to find an all-encompassing theory. Yes, very well now before I say anything else, I have to

first of all, tell you what the theoretical physicists mean when they talk about beauty. For my book, I traveled around the world and have interviewed many theoretical physicists. Many of these interviews you can find in the book. The most interesting thing I learned is that theoretical physicists are, to a large extent, unanimous in what makes a theory beautiful. I want now to summarize what the people have told me, what they mean when they call a theory beautiful. I do not want to define here what you should understand by beauty. I want to say that very clearly, just my summary of what I picked from these interviews. I have brought a little picture of small flower arrangements which my children have done in the garden. This is not a prize-winning work of art, but I think it summarizes an intuitive understanding of beauty which we all bring along. The first thing which immediately catches the eye: it is simple, it also has many symmetries you can immediately see, and of course, it is obvious that it was made from natural elements.

but also in the sense that it is not too orderly; it has certain inherent probabilistic distribution. Random distribution, I would say. OK. Let's start with the term simplicity here. There is a criterion of relative simplicity in science that says about different theories that the simplest is the best. This is a good scientific criterion, and it's not what I'm talking about. But the simplicity of which I talk is an absolute simplicity. This absolute simplicity is postulated by theories, and quite concretely, this is typically done in a way that one wants to have in a theory as few as possible assumptions. This is often done in the form of symmetries or in the form of standardization. A good example is the Standard Model of particle physics. The Standard Model of particle physics describes three different forces: that's the electromagnetic force, and then we have the weak ones and the strong nuclear force. Many physicists would rather have only one force from which these three other forces could be derived.

Why? Because that would be easier, and because it is considered more beautiful. This desire for simplicity is partly based on the method, in the sense that we have certainly seen in the past unifications which were successful, for example, the electromagnetic force, is as the name suggests one unification of the electric and the magnetic force. But if the same is true when we look further into the structure of matter, is completely hypothetical. There is also one basic problem with this idea that one of absolute simplicity can start, and that is that the Universe could be simpler mathematically speaking. One can theories come out clearly easier than what we have here see in the universe, for example, by there is no matter in it, certainly mathematically simpler, but does not describe what we do see. If you want something less realistic, Quantum Gravity can be done in two dimensions, much easier quantify as in four dimensions. So I mean one of my three space dimensions.

time dimension we just live easy. Not in two dimensions, so if you construct a theory, want and catch on this criterion of absolute simplicity. Then that does not help them anymore. A stone has already said it should be. Make it as easy as possible but not easier, and I have him here too. Brought with him what this influence of illustrating simplicity in art. This is a photography style called Minimalism, is the second criterion. The beauty is the so-called native people with the. Basics of physics not much to do usually have natural. The aspect of beautiful beauty, the most difficult to understand, is around. I have to illustrate this to him, photo brought by one. Sunflower field, what I have with us in the area. They probably have already a few sunflower fields seen. That looks so very typical of them because many sunflowers are all. About the same size, they all have about the same size. Not so exactly the same size, but about that. If you would take a relationship. From the sizes.

of those sunflowers then that would be so nearby. He is not exactly 1 but about 1. Yes, they are maybe all so 12 meters high. So, what around the turning around when they are at one sunflower field pass by, and she then sees a sunflower that is a hundred thousand kilometers high. Then they would say that is unnaturally there. We need one explanation for it. And it is exactly this impression, the natural and the physicists. This is what to say if you have a number. She is very tall or very small. That needs an explanation. That is this general concept of naturalness. It is all about the numbers without units. We in theories have in physics, in high energy, in high energy physics especially. There is one more special aspect of the naturalness, that the so-called technical naturalness, which says some small numbers are if there is an explanation for it. Gives such an explanation could be, for example, be an additional symmetry. And that was why so many physicists have thought that one at the large

hadron collider. The so-called super-symmetrical particles should see that argument. Thus goes the standard model of particle physics. It is not technical. Naturally, that's why it's ugly when they do that. Want to make it pretty again. Technically, of course, they can do that. Make an extra. Introduce symmetry which explains why then one small number in it is this extra symmetry. The supersymmetry and the says before that there are new particles. This only has to work if those particles have the masses in the near the Higgs boson. Are and therefore you would have this on the large hadron collider to see additional particles. Is but does not happen. Standard model is so ugly. These two criteria of the general native in the technical. Native are related by that they both try improbable. To avoid parameters. If you agree with my example think with the sunflower field. Then they think that this is unnatural when you see such a big sunflower. Simply because there are already many.

Data has been collected from fields. Know what sunflowers are doing. Have already seen other fields. You have certain expectations. The problem is when you have this intuition from her observations in nature, want to transfer on the parameters in the basic laws of nature. Then you just have no experience they can apply here. We only have this one collection of parameters in our basic theory, and we have no art to find out if that is likely or not. We just do not have any data that we can collect there. We can yes not at different universe pass by and look around us, determine what distribution of parameters we find there, and without this probability distribution is the naturalness, is simply a beauty criterion. So the third point of view of the beauty is what I often as elegance was explained. That's a theory too. If unexpected, she brings new insights or what we typically call the understand aha effect. This is essentially based on that we would like to have a theory. It is simple, but it should be again.

not too easy because that would be boring. That means you want to stop some surprise, have a good one. An example of a very elegant theory is the general relativity theory. The theory of relativity is actually one very simple theory that would be stone might surprise you if you say so because he is very has long plagued this equation deriving. But that was because Einstein was then the whole of the whole mathematical. The equipment you need around this to develop the theory with understanding. Nowadays, you have to learn that as a student. If you know something about differential geometry and topology, then you can use Einstein's field equation within a few deduce lines. So, it's a lot in that sense. Simple theory, but it leads to many surprising insights. Example tells you the general relativity theory. It should be something give like black holes. It should give it gravitational waves. Should light deflection in the sun give. That's all you can see that one equations without further notice takes, and therefore we say that the

general relativity theory. A very elegant theory. Another example of an elegant theory is the string theory. You have surely heard about it. Also, string theory is based on one actually very simple idea, that everything is made of strings. But if they attempt to formulate it mathematically, then that says that in this theory does not always work. That mathematics develops for your own sake. For example, the string theory tells you, if you want these strings to work, then you need additional dimensions of space. We need 10 dimensions for the theory to work. You do not need the supersymmetry anymore in the string theory. How we came up to these surprising insights, this idea, that all is made of strings, is not clear. That is why many people hold the string theory for a very elegant theory. I have here again a picture from the fine art area to illustrate how elegant, how elegance in other fields looks like. This is a picture of one of the artistic forms called fluid art.

You can find that on the internet. There are videos showing how it is made. It's very interesting. One takes different acrylic colors; they are poured onto a glass with different chemicals, and then this glass is drawn over canvas. Pull the glass away, and the substance is then mixing up and produces this beautiful picture we have here. So, here we had also a very simple idea, which leads to surprising results. The problem with elegance is that what you find surprising depends on your prior knowledge. That is also a problem with the simplicity. Many of you probably would not agree that general relativity theory is a simple theory. It depends on what you already know, what you have already learned, and the more you know and learn, the more tolerance one develops for the complications which can bring a theory with it. That means an elegance is evidently a subjective criterion. Together, I call these three criteria: Simplicity, Naturalness, and Elegance.

the hidden rules of physics. Why? Because they are used by many physicists today when they try to construct new theories, but they usually do not write explicitly what they actually did and why they did it. These criteria have become concretely expressed in practice by mathematical terms, and many physicists have simply forgotten that to postulate a certain beauty of the laws of nature is purely hypothetical. Now they could say, well if it works... It worked at least in the past. Well, from some point of view, it worked not so greatly. In the history of physics, there were many beautiful ideas that simply did not work. The best-known example is probably the so-called platonic bodies. You can see it in this picture. The Platonic bodies are regular polyhedra. Kepler has nested inside one another, and from the proportion between the radii, he tried to derive the radii of the orbits of the planets. There are five of these so-called

Platonic bodies, at that time, five planets were known. That fit so well together. Unfortunately, it is wrong. Firstly, because the planets do not move on circles, and also we know today that there are more than five planets. The circular orbits of planets itself, that was also a thing that the astronomers until Kepler times considered as very beautiful. As Kepler then has proved that elliptical orbits work considerably better, the people found it not so great. They said then no no, it has to be a circle because the circle is the most perfect object you can think of, and if God had any choice, he would have chosen circles instead of ellipses. Let's make a circle around the circle around and then maybe in the circle and the circle that was this idea with the epicycles. That, too, does not worked. If you today ask an astronomer if elliptic orbits are ugly, he would probably just tap on the head.

There was also a very interesting episode in the fundamentals of physics around the turn of the nineteenth century into the twentieth. 20 years or so was around a theory called vortex theory; it was very much popular. The historian Helge Kragh has written a lot about it. The idea with vortex theory was that the atoms that were then known, the chemical elements, were actually all knots in the invisible Ether, in which many people still believed at that time. I have here for you this picture of such a knot. From what the mathematicians provided, knots have no ends; we can say it was not like as the thing we usually call knots. These mathematical knots were classified, and the idea at that time was as fast as that of the structure in the periodic table of the chemical elements. In fact, it was not possible to predict anything with it, but people have written a lot of scientific articles about it. At the end of the day, we did not follow it any further, because then we have the

developed the quantum mechanics, and the quantum mechanics explains the structure of the periodic system. Another theory originally was considered nice, but finally, it was not working, the idea that the universe is unchanging in time, is that it was just beautiful, always as it is, and always will be like that. We once perceived it as beautiful, but it just does not work out. The general theory of relativity shows that the universe expands, and it is too in agreement with our observations. And then there are a whole series of ideas to the great unification, which were followed by prominent physicists in their late years. For example, here is a quote from Werner Heisenberg, he wrote in one letter to his sister, That these relationships correlate with all mathematical abstraction, have an unbelievable degree of simplicity which would not have been more beautifully dreamed by Plato, it is a gift we can just only accept. You cannot just invent those relationships.

they have been there from the beginning of the world. Heisenberg made significant contributions to the development of quantum mechanics. He is known and famous for this, what he wrote about here is however not the quantum mechanics, which, by the way, many people find as very ugly, but his approach to a big unified theory which he followed in the fifties. In fact, he was pretty sure then that he's on the right track and have also given lectures about it. In one of these lectures, he has to talk to a journalist. He then explains to this journalist that they have basically understood everything and he just need to work on some details... Then his colleague Wolfgang Pauli written a postcard to his friend George Gamow, he has painted an empty rectangle on it and written: This is to show the world, that I can paint like Tizian. Only technical details are missing. Why have you never heard anything about Heisenberg's great unified theory?

The theory worked very badly, and after his death, it has no other followers. So, on one side, we have all those beautiful ideas that do not work; on the other side, we have ugly ideas that work. The best example of what we got into is this flytrap. Obviously, the ugly works. Also, a very good example is quantum mechanics. Quantum mechanics is perceived by many people as ugly because it is counterintuitive. Do not count me personally into this group. I am from the mathematical corner, and I find the whole mathematical apparatus of quantum mechanics very beautiful, but by many people, it was criticized since the beginning, and it is still. Then we have the quantum field theory, which we use in the Standard Model of particle physics in a procedure called the regularization. That's the way it is with these theories; what you want to calculate and measure is very often infinite. It is not that great. We never really measure infinity. That's a mathematical problem we have with these theories.

What we do then is that we have to apply a procedure with which we subtract infinity from infinity so that the result is finite. That does not sound so much kosher, but it works quite good. The results we gain in this way match with the observations quite excellently. Many people do not like this regular regularization procedure at all; in particular, Dirac was very much against it, and he has originally considered regularization in the quantum electrodynamics so ugly that this theory must be wrong. But it is correct, and we still use it today. Then there are those elliptical orbits about which I had already talked briefly, originally considered very ugly, and there is the idea of Big Bang, that the universe has its origin in very concentrated matter, which then has expanded and cooled down. It is also what was originally considered as ugly. What can be seen is not only that ugly ideas exist and work but also that our ideals of beauty are changing in time.

I actually think that many astronomers today find considerably nicer that the universe is dynamic and that it is changing from one to another epoch, than that if it would stay the same forever. So yes, what's the point or the bottom line with the beauty sometimes it works sometimes it just does not work. There is also no reason why beauty arguments should work because our sense of beauty is certainly to a certain level genetic. For example, this impression that symmetry is beautiful, that is generally accepted. It happens that symmetrical organisms are more likely to be healthy, so here you can somehow assume that there are certain genetic foundations. But also our sense of beauty grows certainly greatly from our cultural and social backgrounds. Either way, the natural selection does not affect any knowledge other than to survive. There is also no reason to assume that neither the genetic preconditions nor the cultural or social conditions tell us anything about how the laws of nature should work for the elemental building blocks of matter.

Beauty criteria certainly had a certain part in the Standard Model of particle physics and also the general theory of relativity creation, being based strongly on symmetry principles. It is certain that we are trying to find beauty in the principles of matter even more. But this experience approach is just not helpful if you want to develop new theories which consist of completely new mathematical structures, for this simply we cannot apply this experiential approach anymore. Aesthetic criteria... the summary is based on experience but we do not know if they apply to new theories. The scientific approach would therefore be to use aesthetic criteria only as hypotheses, and then test if they work. We already have aesthetic criteria as hypotheses used, whether they work or not, and they have not worked for 40 years, yet we keep using them. And I think that's the reason why we see this stagnation in the fundamental physics we've created a vicious circle of theories as already stated, in fundamental physics simple things have been made.

that means we need more and more time these days and also more money to test new hypotheses, send various satellites in orbit around the Earth. We need to build new particle accelerators. We need big telescopes. That just takes decades, and it can cost billions of euros. But that also means we have to choose the hypotheses we test very carefully. What happens if we make an experiment to test new hypotheses is that with great probability we get negative experimental results. That means we only verify the theories which are already known. We find no hints of new phenomenons. And of course, it is natural that negative results are also results. Yes, this can rule out hypotheses, but if you want to develop a new theory, it is not a particularly helpful result. What you really want is to have some data for any new effects which you can then describe with your theories. But that does not happen, and because we lack this data, we stay sitting on the unmotivated hypotheses. Then we get back negative experimental results and so on and so forth.

Here is an example of such false predictions. In the Standard Model in particle physics, there is a parameter that is small, but for the parameter, there is no explanation. This is the so-called Theta parameter. In order to explain why this parameter is small, there was a definite solution proposed in the 70s. It was then quickly discovered independently by both Steven Weinberg and Frank Wilczek that should mean that there is a new particle. This new particle was called axion. This axion was so quickly forgotten, how it was discovered, and indeed in the 70s. What happened then was not that the theoretical physicists said, Okay, let's forget the thing with the axion. That did not work. Instead, they changed the theory with the axion to make it harder to measure. This is called the invisible axion. That is the resume. We have not found any. The problem is they are invisible. They were designed to be hard to measure.

Here you can see a picture of one of these experiments that measure axions. There are many other particles that physicists have come up with. You did not see them all. For example, there is a whole class of particles so-called WIMPs (Weakly Interacting Massive Particles). This is a whole class of particles that allegedly make up the dark matter. That was motivated by the so-called WIMP miracle, this is a numerical coincidence to which the physicists have given a lot of meaning and which has been widely held to be a convincing argument and sometimes still becomes. How does it work with the WIMP miracle? Roughly speaking, it works like that, if you accept that the mass of these WIMP particles is around what LHC measured, that's not the case, but that was the argument then, and you assume that these WIMP particles are interacting with the weak nuclear force, then you can calculate out how many of these particles were produced in the early universe.

you should get the number of particles, and the amount of it agrees approximately with the observations that we of the dark matter have. Thus, a purely numerical coincidence has been ruled out meanwhile, because we know there are no such particles in the energy sector of the LHC collider. And also, the interaction probability is increasingly limited by experiments. For example, with the experiment you will see in a moment on a picture. This is the so-called Xenon Monti experiment. That's an upgrade from the Xenon 100, and that's an upgrade from Xenon 10, and that's an upgrade from the original Xenon Experiment. Every time this experiment did not find these WIMP particles, then the theorists go and say, Yes, maybe that's the sign that the WIMP particle interaction is even a little bit weaker... Then there were all the wrong predictions for LHC. I talked about them at the very beginning. There was the talk about super symmetric particles, about higher dimensions, about small black holes, parallel universes, graviton, and so on.

There were tens of thousands of predictions. These predictions were all wrong. Every one of these predictions was wrong. The people are often shocked when I say that tens of thousands, they say my god, where does this number come from. It is quite simply scientific publication which turned up to each of these theories. There were a lot of bills where people introduced additional details. There were additional additional particles or the extra dimensions were somehow twisted a bit or there were still some under variety in this extra dimension you can go without end when thinking out mathematical constructions and now they can publish everything in scientific journals, and everything is false. The only new particle we have seen is the Higgs boson and this prediction is very important, it dates back to the sixties and it was NOT based on a beauty argument. What was the difference? The false predictions all tried to solve aesthetic problems for instance the unnatural mass of the Higgs boson that was the reason why these supersymmetric particles were introduced.

There is the small value of the cosmological constant. I did not comment on that yet. This small value of the cosmological constant is explained by introducing additional fields. This is the so-called dark energy. There were a lot of experiments made, and nothing was found. The small electric dipole moment of neutrons, that's the story with the axions. I have talked about it already. The three different symmetry groups of the Standard Model, I had mentioned that briefly. You do not want to have three different groups and just want to have one group, a great symmetry which these three forces can unify. People tried that in the eighties, there were also theories proposed. The consequence of this is that the protons, one of the elementary parts of the matter, is sort of instable. It should break up. Then it was researched and found nothing. This disproved some of these theories, and the result is, the theoretical physics brought up other theories which are hard to disprove.

Yes, and then there are more such aesthetic problems, as weak force of gravitation and so on. These are all things where you can say, maybe it is just like that. Maybe the Universe just is like that; there is actually no problem with it. The cosmological constant, maybe it's just a natural constant which just has this value. Finished, end of story. You can look at which problems have led to historical breakthroughs. That was always the case when physicists solved mathematical consistency problems; that is, the theory had an internal contradiction. For example, Einstein noticed that in Galilean invariance of space and time, space and time are treated differently, not matching with Maxwell's equations. That is why Einstein's original paper is called On the Electro-Dynamics of Moving Bodies. He did not understand how the movement of the bodies matches up with Maxwell's equation. When he tried to solve this contradiction, he found the special theory of relativity.

Then Einstein also noticed that the special theory of relativity does not match together with Newtonian theory of gravitation. How so? In the special theory of relativity, the speed of light is an upper limit. All information must move maximally with the speed of light. It can be slower, but surely not faster. In Newtonian gravitation, interactions happen instantly. And here Einstein said, No, this cannot be so. How he tried to solve this contradiction is now the general theory of relativity. It also turns out further that the special theory of relativity does not match up with quantum mechanics. Dirac noticed that, and he has solved this contradiction with the Dirac equation. If you have the Dirac equation, you need to make a couple of steps, but you eventually come to quantum field theory. These are the theories we still use in the standard model, and as I said before, the Higgs particle was not predicted on the basis of the beauty argument. The Higgs was introduced

for mathematic consistency of the standard model. When you have the standard model without the Higgs particle, it just does not work at the energy level which was tested on LHC. That means we knew even before the device was turned on that something must happen because the theories we had just could not make any predictions for what should happen there. It would not necessarily mean the Higgs particle must exist. It could have been something else, but we knew something new had to happen there. So here is my suggestion for progress. In the past, physicists made progress by solving contradictions, and therefore I suggest when physicists try to solve a problem, first make sure that there really is a problem. A perceived lack of beauty is not a contradiction and therefore not a real problem now. It's not that I'm the first to point it out that the beauty criterion is not objective; rather, it is subjective. Of course, the physicists that absolutely know too, they also like to say that beauty is naturally

subjective, and we should not use it as a criterium, but we will do it anyway. The big question is, therefore, if beauty arguments work so bad, why do physicists use them then? They have not been working for 40 years now. But still doing the same thing. I think a plausible reason for that is they just make it simply just because everyone else does it. It's just general accepted practice in fundamental physics that one uses these beauty arguments; no one pulls up his eyebrows. In the current organization of academic research, scientists are rewarded when they work on topics that are productive and popular. The beautiful theories are popular, and if they also produce many bills, then they are also productive, and these are exactly the theories which we see that they are spreading further and further. On the other hand, thorough methods and careful conclusions are neither productive nor popular. This problem you can naturally see not only in physics. You can also see that in psychology and sociology, where many people use measures for statistical relevance.

Even though we have known for decades that it is not reliable, there is the so-called p-value of which you may have heard about. Jessica Utts, president of the American Statistical Association (ASA), has written about the topic something: Statisticians and other scientists have been writing on the subject for decades. That's what she said in 2016. This problem has been around for 30 years. And these psychologists, they have commented on the matter as follows: Everyone realized that it was wrong, but we thought it was wrong, as it is wrong to go across the street at the red light. That brings up the question, why do we see that right now if that was not also in the past? That scientists there looked at what other people do and it somehow forced these groups to do it. That, of course, has always been so, but science has changed and that has this pressure became much stronger. There are apparent ways how the science has changed. At the first place, we have today

more scientists. The number of scientists is rising exponentially. These scientists are in better contact with each other through great progress in information technology. The contracts of scientists are getting shorter and shorter. Here you can see in this statistic, the number of people with permanent employment continues to go down. Much research is nowadays going on short-term projects, that are typically two or, when you have luck, three years. It is essentially a public contract. But science has not adapted to this change. What can we do? One thing we can do is we can cure the symptoms we see, we can follow specific guidelines to prevent wrong methodics. This is partially already done. For example, you can establish better criteria for statistical significance. You can, for example in the life sciences, encourage scientists to register the studies before they are performed. That means you do not change the hypothesis after you have collected data. In the same way, one could, of course, one could ask the theoretical physicists to not use any beauty criteria.

and that probably would solve the acute problem, but sooner or later it would come back in another form. The real problem which they have lies much deeper, in the organization of scientific research in general. That's why I think what we should do is to cure the disease. The peer review of scientific hypotheses needs objectivity, and scientists have to take into account how their membership in some group can affect the objectivity, and that's just not easy at the moment. This brings me to my conclusion. The application of beauty criteria to select from scientific hypotheses is a bad methodology, but such bad methodology becomes the accepted norm if many scientists reassure each other that they are doing the right thing. Thank you for your attention.

Sabine Hossenfelder: Was läuft falsch in der gegenwärtigen Physik?

Universität Stuttgart

대형 강입자 충돌기와 기초 물리학의 위기

제네바의 대형 강입자 가속기는 세계 최대의 입자 가속기로, 2012년 입자 물리학의 표준 모델에서 마지막으로 사라진 입자인 힉스 입자를 발견하는 데 기여했습니다.

기대와 달리 이 충돌기는 예상했던 다른 입자나 현상을 발견하지 못해 기초 물리학의 정체로 이어졌습니다.

이 분야의 두 가지 주요 이론인 일반 상대성 이론과 표준 모형은 서로 맞지 않아 1930년대 이후 미해결 상태로 남아 있는 복잡한 문제를 야기하고 있습니다.

암흑 물질은 우주를 이해하는 데 있어 중요한 도전 과제로서, 입자의 추가 또는 일반 상대성 이론의 수정이라는 두 가지 주요 설명이 있습니다.

자연 법칙에서 아름다움을 추구하는 것은 뉴턴부터 현대 과학자들에 이르기까지 역사적으로 물리학자들의 기본 원칙이었습니다.

자연 법칙을 밝혀내는 아름다움의 힘에 대한 믿음은 여러 세대에 걸쳐 이어져 이론 물리학의 발전에 영향을 미쳤습니다.

이론 물리학의 아름다움에 대한 탐구

표준모형에 포함되지 않았던 쿼크의 개발로 노벨상을 수상한 물리학자들은 이론의 아름다움과 우아함의 중요성을 강조합니다.

이론 물리학자들은 절대적 단순성, 대칭성, 자연스러움 등 아름다운 이론의 특징에 대해 만장일치로 동의합니다.

여러 현상을 설명할 수 있는 통합된 힘에 대한 열망은 단순성에 대한 추구에서 비롯되지만, 우주의 복잡성은 이러한 이상에 도전하고 있습니다.

물리학에서 대칭과 우아함의 역할

입자 물리학의 표준 모델은 힉스 입자의 질량을 설명하기 위해 대칭 및 초대칭 입자를 도입하려고 합니다.

일반 상대성 이론이나 끈 이론과 같은 이론의 아름다움과 우아함은 놀라운 통찰력과 새로운 차원으로 이어질 수 있습니다.

그러나 이론을 구성할 때 단순성, 자연스러움, 우아함의 기준은 주관적이며 물리학의 역사에서 항상 성공적인 결과로 이어지지는 않았습니다.

과학 이론에 담긴 아름다움의 역설

플라톤 천체는 한때 행성의 운동을 설명하는 것으로 여겨졌지만, 타원 궤도와 5개 이상의 행성이 발견되면서 이 이론에 도전장을 내밀었습니다.

원자가 보이지 않는 에테르의 매듭이라고 제안한 소용돌이 이론은 인기가 있었지만 결국 양자역학에 의해 포기되었습니다.

하이젠베르크와 같은 물리학자들의 통합 이론 추구는 아름다운 아이디어가 실패한 반면, 양자역학이나 정규화처럼 직관적이지 않고 '추악한' 이론은 성공한 것으로 입증되었습니다.

이론 물리학에서 아름다움의 역할

많은 천문학자들은 우주의 역동적인 성질과 변화하는 시대를 높이 평가합니다.

유전학과 문화적 배경의 영향을 받은 인간의 미적 감각은 입자 물리학 및 상대성 이론의 발전에 중요한 역할을 해왔습니다.

그러나 미적 기준을 새로운 이론의 가설로 사용하면서 기초 물리학이 정체되고, 실험 결과가 부정적으로 나오고 가설에 동기가 부여되지 않는 악순환이 반복되고 있습니다.

윔프 입자와 이론 물리학에 대한 검색

암흑 물질과 관련이 있는 것으로 여겨지는 윔프 입자에 대한 탐색은 여러 번의 실험에도 불구하고 성공하지 못했고, 이론가들은 더 약한 상호작용을 제안했습니다.

초대칭성 및 여분의 차원을 포함한 새로운 입자와 이론에 대한 수많은 예측은 모두 틀린 것으로 판명되었으며, 힉스 입자는 유일하게 관측된 새로운 입자입니다.

이론 물리학은 서로 다른 힘을 통합하고 내부 모순을 해결하는 데 어려움을 겪으며 아인슈타인의 상대성 이론과 양자장 이론의 발전과 같은 중요한 돌파구를 마련했습니다.

물리학에서 힉스 입자의 역할과 아름다움의 기준

표준 물리학 모델은 힉스 입자 없이 예측하는 데 어려움을 겪었고, 이는 새로운 무언가가 필요하다는 것을 의미했습니다.

과학 이론에서 아름다움의 주관적인 특성에도 불구하고 물리학자들은 아름다움의 인기와 학술 연구의 압박으로 인해 계속해서 이를 기준으로 삼고 있습니다.

과학자의 기하급수적인 증가와 단기 프로젝트의 증가는 과학 연구에 결함이 있는 방법론을 수용해야 한다는 압박을 가중시켰고, 이는 과학 연구에 있어 결함이 있는 방법론의 수용으로 이어졌습니다.