When this receives energy, it gets excited. To calm down, it needs to follow the law of energy conservation. It has to go home while getting rid of the energy it received. The form of getting rid of that energy comes out as light. It fell off the stage here. Normally, it makes a sound like uh when that happens. However, if it falls from a high stage like a club, it jumps and disperses the energy. People, it's the same thing. I've even seen time to greet you. It may be slow, but it's a fun science meet. Nice to meet you, professors. Nice to meet you. Nice to meet you. We have the third presenter, Professor No Chang-dong from Sungkyunkwan University, here to talk about gamma rays. Wow, today he came to be a gamma ray man. Finally, it's really happening today. But earlier, you asked me if it's possible. No, from the beginning when you sent me the materials, implicitly, I've seen it four times.

I can feel a strong determination to do this, so many graduate students have come here to get some funding. It's like this, it's quite good. Shall we start with a review? We will go through the review really quickly. But first, can I talk a little bit from here? It seems like I've seen it three times, yes, it's the same. The lab I belong to is called Hawk Experiment Lab. The logo on the left corner is the Hawk logo, and the one on the top right is SWG. Now, we are trying to start as the second batter of Hawk, but until last time, there were 14 countries, and as of last Friday, it became 15 countries. Did South Korea join? No, France joined. South Korea was already in there. It was in there originally, and France joined this time, making it 15 countries. Finally, the one who brought this hidden clothes has arrived wearing the Hawk logo. So, I thought I should wear this clothes around the time we start the gamma rays. So, this time, it's 100% gamma rays.

I started, so I came to wear this. Do you remember seeing this? In my field, I am now in physics, specifically in astrophysics, and within that, in high-energy astrophysics. High-energy astrophysics would probably be the highest energy within astrophysics. Among high-energy astrophysics, the highest energy is gamma-ray astrophysics. Among gamma-ray astrophysics, I am studying very high-energy gamma-ray astrophysics. Therefore, it can be said that I am studying the observation of photons, light, or electromagnetic waves in the highest energy range. We have seen this a lot now. When we observe the universe, there are friends who bring us information from the universe, and they are called messengers. As of now, humanity knows these friends.

It's telling the story in reverse order. Gravitational waves, neutron stars, spacecraft, electron beams, like this, there are five friends, and now, the most recent direct observation was made by gravitational waves, and the reason for the delayed direct observation is because it is so weak, and that is important again. Because saying it's so weak means that when we see this, it means an incredibly powerful event has occurred. For example, a collision of neutron stars, a collision of black holes and neutron stars, a collision of black holes, it's about this level. That's why just by seeing waves, it causes a stir. Therefore, it is now playing an important role, and now, in the case of neutron stars, it is important to confirm the celestial bodies that can be created. The reason for this will be explained later. In fact, there are so many neutron stars, and they don't interact with each other, like our fingernails.

Billions of particles pass by every second, but they don't interact much, they just go through. That's the issue. Next, in the case of mediation, particles made up of pre-existing particles come from all directions towards Earth. These particles, like the other two, are observed to be huge, even more than the other two. It has been over a hundred years since these numerous particles have been observed, but we don't know where they come from. So, remember this. Now, what's important here is that most of the things that make up spacecraft are the nuclei of atoms, right? But for convenience, we'll just call them protons. Protons make up the largest proportion from the start, so when I talk about protons, you can think about them. Lastly, there was an electron beam on the top left, or an electron beam, light, or photon. I will talk about this.

We are going to talk about mixing it up, and you should think that everything is the same. I kept saying that astronomy using electromagnetic waves is like human history because humans were born with eyes, and ultimately, observing celestial bodies due to sunlight, starlight, and moonlight is the significance of astronomy. We have been doing astronomy since the moment we were born with eyes. So, in part two, we looked at this type of electromagnetic radiation. As I mentioned before, it is divided into parts based on the human eye, and when you look at it, yes, that's right. This electromagnetic radiation is represented above as a wavelength. So, the waves are drawn like this, just continuously decreasing or increasing, having a spectrum. We have divided it according to the characteristics tailored to our convenience. The left side is the wavelength.

Long-wave friends are on the right, meaning that on the left are low-energy photons, and as you go to the right, the energy increases. Starting from the left, it will be radio waves, so it will be radio waves. Radio waves are further divided because microwaves play such an important role. So, within radio waves, there are actual microwaves. As the energy increases a bit more, it becomes infrared. As the energy goes up more, it becomes visible light, which is the most important for us. As the energy goes up again, it becomes ultraviolet rays. From here, as I mentioned last time, the energy increases enough to start causing harm to our bodies, so we work hard to block it. We also block ultraviolet rays, and then as the energy goes up more, it becomes rays.

I know it might sound a bit strange when the first photographers hide, but they go into another room to take pictures. It can be dangerous as the energy increases. Finally, gamma rays, which I am working on, are really difficult for us to control. When ordinary people hear about it, it is the most unfamiliar compared to the other six, and therefore can be considered the most dangerous. Now, I am studying the field of observing this. In the case of gamma rays, no matter how much energy rises, gamma rays are divided into seven categories here. Among them, gamma rays have the highest energy. If you remember this, it will be enough. Now, let's start the actual review from here. It's not really official yet, but now, when it comes to energy, which unit is the most familiar to you? Calories, right? Because we consume energy by eating.

It's about what goes into the body, and when you exercise, you burn energy. So, it's indicated in calories. But here it says, it's in electron volts, which is one of the units that indicates energy. So, it has the same meaning as calorie amount, but you just have to think that the values are different. When K is attached, it's like K, indicating that it is a thousand times bigger. Then, me is like mega, meaning it's a hundred thousand times bigger. Next is giga, and then tera. But you might be familiar with this because it's related to computers. So far, we've been using electron volts for TVs outside the picture. So why did we use electron volts now? Well, we are familiar with calories, so why didn't we use calories? Because calories are a familiar unit in our world, as humans consume.

It's like the level of exercise, right? But my body is made up of many particles, so we need to use units tailored to those particles. So, it's okay to use electron volts as calories because they both represent the same energy. However, when using calories, one electron volt becomes 10 to the power of 22, like that. Physicists would see this and think something is wrong. So, they converted it to units that match, making it easier to understand. From now on, I will continue to talk in electron volts. Speaking of scientific matters, when an electron at rest in a vacuum receives one volt, it becomes the kinetic energy that a particle can have.

Do you understand? Next, the y-axis represents how bright it is. What does bright mean? It means how much light is emitted. So, when you look at the energy spectrum on the x-axis, it shows how much light is emitted. Then, it is indicated on the y-axis. So, if you look at the seven types of electromagnetic waves I mentioned earlier, starting from radio waves, then microwaves are included because they have high energy. After that, it goes from infrared to visible light, ultraviolet, and finally gamma rays. Now, looking at the x-axis, we have temperature. How hot does an object need to be to emit light energy? There is a formula for this, so the corresponding values are drawn on the x-axis. This allows us to see how hot the celestial bodies are. If you look at this diagram, regarding the axes.

I kept explaining in detail because I clearly stated that I created units with the energy that a single particle could have. If you look, it goes up to giga, electron volts, and even tera, peta. So, isn't it a mistake in creating the units? Right? Also, looking to the left, it goes down to very small units, but I don't think there is a problem with the system. My thought is that as the electron waves change so much, and if we understand the large energy range well, it shows how outstanding humanity is. It's evidence of that. I slightly think like this, right? People say it's because of the family, but I don't. I see a problem with the units themselves. The electron volt is a very good unit. But now, for those working with waves, infrared, or radiation, they often don't use electron volts. So, I saw this too, and now.

How poorly does the brown part penetrate our atmosphere, and this is now flipped opposite to the picture just now, so the right side is low energy, meaning gamma rays are on the left, very long radio waves, I will ignore it. If you look at the far right, you can see a part that is now pierced all the way. Waves penetrate well there and come down, so humans could rapidly advance in radio astronomy. That's why we could observe waves very easily. Moving up a bit, there are infrared rays. If you think there are some parts that are slightly pierced, most parts are blocked. So, going out into space, James Webb, as if opening an umbrella, is observing diligently now. The reason is that they made something so expensive, but not going out into space.

When it rises, everything is absorbed, so it is not visible. Because the atmosphere is all correct, so you have to go up, and then you can see the ultraviolet rays well. So, now we can see the day brightly, right? Then, if you go to the left, there are harmful ultraviolet rays, but luckily our atmosphere blocks them well. However, from the perspective of a gamma-ray astrophysicist, it's not good because they are not visible. If they were visible, they would be harmful to us. So, now, if I talk about high-energy astrophysics, what does high energy mean? I didn't know at first either. So, I asked the high energy physicist. When I was a student, I asked about the 13.6 electron volts. He explained the importance of high-energy astrophysics. So, what is the significance of this 13.6 eV energy for ionization?

In an atom, there is an electron that can escape from the nucleus, and the minimum energy that an electron needs to fall is what we call ionization. The minimum energy to drop this is 13.6 volts, but the energy itself is not that high. So why is this important? From the moment it escapes, these particles can exist on their own, not as part of an atom. Protons can exist as protons, and electrons can exist as electrons. This is because they can exist independently. Since it has escaped, the energy becomes the energy at which we start to see light corresponding to it. Through interactions between particles, for example, when particles collide, this process allows us to see light. Energy higher than this can make all this possible. Therefore, of course, 13.6 eV is a very low energy, so it is sufficient.

Hot friends can also make light. Because, for example, the sun also creates a lot of heat. The important point is that there is enough energy. From here, we can see the light that comes from the interaction between particles, not the light caused by heat. That's why it is divided into high-energy astrophysics. This is what I am doing, high-energy astrophysics. I will explain the ultimate goal of studying gamma-ray astrophysics and talk about gamma-ray astrophysics. I think there are three reasons. The first reason is obvious. It will be a new science field. In fact, science is to find new science. Of course, because it has the highest energy, it cannot be done with other experiments.

We can find things, especially as we go up with this high energy, we think that things similar to the initial state of our universe will happen. As we go back to the initial state, the energy was high. The more we see this high-energy generation, the more we can explore things we didn't know before. That's why we think about new science. The second thing, which may seem a bit obvious, is the discovery of high-energy celestial bodies. By looking at the highest energy moments, it means that we are studying the celestial bodies that create them. These possible celestial bodies will be seen later. Then we can think about why only these friends can create this. Do we really need to spend money to create this? It might be enough to just look at the stars. We can have this kind of conversation. However, by observing gamma rays,

Before, when you looked at the line, you could see thousands or tens of thousands, but now you can only see dozens. Where does this kind of energy come from? So, when I looked, there were some really strange celestial bodies that I didn't know about. I didn't know there were these celestial bodies. So how do these unknown celestial bodies produce such high energy? What process creates this? I want to find this out. The final third goal is to find out where the spacecraft comes from. We didn't know where the spacecraft came from. Do you remember the Amaterasu particle experiment? It's an experiment where a particle brings back the energy of dropping a brick from your waist. We traced it diligently and found that with gamma rays, we can indirectly confirm where all these spacecraft are coming from. I will consider the green line as the spacecraft. What accelerates these spacecraft?

When we talk about celestial bodies, if we say it's in the left corner, the spaceship is created from there. So, while flying straight, there are so many magnetic fields in various galaxies that the path of those particles gets twisted. So, by the time it reaches Earth, if we try to trace it, it will point to a completely different place. That's why we don't know where it comes from. But when we look at gamma rays, if the particles from the spaceship interact with other particles, gamma rays can be created there. However, gamma rays don't have a phone, so they fly in a straight line. So, when we see those gamma rays, we can say, Oh, this friend created gamma rays; this is the friend who created the spaceship. The reason is that the phenomenon that can create gamma rays is not just one thing; it can be created in several ways. So, just because we saw gamma rays, it doesn't mean that they came from the spaceship.

I can't just say I'm here. Gamma rays, after all, are not created by light, but by three main mechanisms. I've divided them into three main categories. The first one is called thal mission, which means it's a way to create light by nuclear fusion. However, in the celestial bodies known to mankind so far, there are no celestial bodies hot enough to produce TV gamma rays. They need to be extremely hot. But we are watching gamma rays. That means they must not be thm missions. So, number one is eliminated. This one below is a quantum mechanical explanation. I'll just briefly explain it in a simple way. When particles receive energy, they get excited. We also get excited and play around for a while and then calm down.

When it comes back home, it goes back to where it originally was, it goes down to regain composure. In order to calm down again, the energy conservation law applies. It has to go home while releasing the energy. The form of discarding the energy it received comes out as light. If it falls from this table, usually it makes a sound, right? However, if it falls from a high stage like a club, it jumps off, how do people react? It's the same thing. This is what we call emission line. It's difficult to create TV gamma rays in cans. Then we have three left, it says non-thm mission. It means it's not the first one. In the end, it won't be just one thing, right? There are many processes that can produce a lot of light, and they are all included in those three. I will explain only two things. If you think of these two as the main mechanisms for creating TV gamma rays.

The first thing is the process of inverse Compton scattering. It's the opposite of Compton scattering. So, I mentioned earlier that the interaction between particles is important. This is the moment when we are looking for light here. Below, it says electron. It means a single electron. If you look above, a low-energy photon comes down in an arrow like this. When these two collide in a low-energy photon state, what happens is that the electron gives a significant portion of its energy to the photon. So, it's like the photon is absorbing light and energy. Then, the light will increase in energy. So, this can even go up to TV gamma rays. Where do these low-energy photons come from? There are a lot of low-energy photons because we have cosmic microwave background radiation.

In the microwave region, the name itself has background in it, so it can be found anywhere. Therefore, there are many of them. Also, there are many emissions coming from stars like Thal. There are infrared and ultraviolet rays as well, coming out a lot. So, you should think of those friends as low-energy photons. So, when watching TV gamma rays, among my ultimate goals earlier, there was the second one, which is being able to find high-energy celestial bodies. The reason why that is important is because when we see TV gamma rays, it means we saw the orange color on the right. Then, it means that there were very high-energy electrons present. So, where did those high-energy electrons come from? That's why when we see t, it means the sun is twinkling like that, not just emitting TV gamma rays, they are friends specialized in particle acceleration, extraordinary high-energy particles.

It's emitting and the photons around it collide with it, changing into TV gamma rays, which fly out. This is what I showed you in the second mechanism. On the left side, there is a celestial body where protons are created. Protons are accelerated there. So, it is written like that. Those are protons, in short. So, what is written at the beginning is receiving energy transactions and protons come out. Those protons collide with other protons nearby. Then, you can ask like this: Where did the proton above come from? The one below came from the celestial body, and the one above came from the protons around. Friends around are usually full of hydrogen, dust, or interstellar material, so there is a lot of hydrogen. So, ultimately, if an electron falls from hydrogen, it becomes a proton. So, you should think of it like that. Accelerated protons with energy, around them.

It shows what happens when wandering protons collide. So, when they collide, what happens? It's written as pp. Two protons collided, and two protons came out. But if you look closely, there is another particle below, written as pi. It's a neutral pion that comes out with the protons that went in initially with lower energy. And with the remaining energy, this neutral pion is created. This neutral pion is unstable, so shortly after, it decays into two or more gamma rays. Ultimately, that's why gamma rays are emitted. So, for those curious about why it's two or more, you can think of the special theory of relativity. So, in the end, from our friend who creates cosmic rays in space, gamma rays can come out. That's what it is. Protons are accelerated in space, and when they collide, this is how it happens.

Ultimately, it emits gamma rays. However, earlier it was electrons, so just because we saw gamma rays, we can't necessarily say that it was created by protons. It could also be electrons. When we observe gamma rays, it could be a celestial body creating a spaceship or a celestial body accelerating electrons. So, in cases where good papers are published, we can still calculate this through our modeling. Therefore, we can say that the probability of it being produced as protons is high. Then, these become more important and now they are becoming papers. These celestial bodies could be celestial bodies that can create protons, helping us get closer to solving the mystery of where the spaceships come from. So, even if we just saw gamma rays now, we don't know if there are protons or electrons.

There is a way to know right away, which is just below that red arrow. When you look at that, it's the same. Protons are being accelerated again, so protons collide. But this time, there are cases where neutral pions are created. They are now pions carrying a charge, so even if the same particles collide, there are many possible outcomes, like having many TV channels. So, it all happens probabilistically. That's what quantum mechanics is. So, when a pi-zero appears above, below, you can see only pi-plus, but pi-minus can also appear. Whether it's plus or minus, they are also unstable. Muons decay into particles. In order for muons to decay into particles, muons have a family called leptons, and that's where it belongs.

Because it's a particle, a neutral muon should come out. However, a muon is also unstable, so if you look there, it's labeled as e plus. That's a positron, right? Positron will now decay. If my muon was just an electron, it will decay. Then, while decaying, two neutral muons will come out again. Three neutral muons come out when you see a neutral muon. So, by observing neutral muons, we can confirm the existence of the universe accelerator. Thank you for your time. It was a slow but cool Science Lab Meeting. Thank you, professors. Thank you.

우주의 미스터리를 해결한다?! 고에너지를 만드는 천체의 정체는 무엇일까? 감마선천체물리 3탄 1부! [성균관대학교 노창동 교수]

과학의 대중화를 위해 박사급 아재들이 직접 만든, 
될 과학 “안될 과학” 다 만드는 본격 과학 채널

안될과학과 함께 세상을 바꿀 과학자 및 과학기술 분야 전문가+덕후분들을 항상 기다립니다.
과학의 경이로움을 보여주실 수 있는 본인의 연구분야나 전문적인 지식이 있다면,
아래 메일주소로 내용을 보내주세요! 협업 절차에 대해 안내해드리겠습니다. (원고료 지급)

*안될과학 콘텐츠 카테고리
[1] 랩미팅 : 매주 화요일, 목요일 밤 10시 라이브로 진행되는 역수직 과학 토크쇼 (카페 공지 일정 참고) 
[2] 긴급과학 : 하나의 주제에 대하여 방대한 자료와 함께 빠르게, 깊이있게
[3] 초긴급과학 : 긴급과학보다 시의성이 있는 최신 주제를 더 긴급하게
[4] 언박싱사이언스 : 초최신 과학 논문을 언박싱하여 쉽게 설명
[5] 과학자열전 : 과학자의 잘 알려지지 않은 삶과 그들의 업적
[6] 안될과학TMI : 일상의 궁금증을 과학적으로 풀어내는 콘텐츠
[7] 떠날과학 : 직접 현장으로 떠나 전하는 과학 이야기 
[8] 랩무비 : 영화 안의 과학을 다룹니다. 단, 억과주의! 
[9] 게임속과학 : 게임인가요? 과학인가요? 게임속과학
[10] 과학적리뷰 : 무엇이든 과학적으로 리뷰합니다!
[11] 긴급홍보 : 과학관련 주제를 굉장히 빠르게 홍보
[12] 카테고리 없어도 결국 과학과학, 과학은 사랑입니다♡

- 쉬는 중 -
[-] 브이로그 : 일상 콘텐츠. 아재들에 맞지 않는 것 같아 한편 만들고 잠시 중단 
[-] 안될실험 : 과학적인 설명이 가미된 과학 실험 꽁트 콘텐츠. 잘 만들진 않음 

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