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  1. The reason why I fall a love with the particle physics ... (1)

      When I was an elementary school student, I had been really interested in making the scientific mechanical models and mini radio kits which has four transistors. Once I concentrated on these working, I spent a lot of time to make it up even if I couldn't sleep at all. The more the knowledges are accumulated in my head, the bigger the ambitions which I want to study in physics are drawn in my dream. These are the reasons why I am studying in physics now. I had not made any specialized major that I will work on having a great passion before I took this introductory particle physics. However, It is a pretty good opportunity for me to think about my future life in the science. There are many research areas in the physics. However, I will focus on the particle physics from now, because I think the particle physics will give the answer our ultimate question on the origin of the universe. Now, I would talk about several topics that I have studied through the elementary particle physics class. 

      First, I would like to talk about symmetries. There are several operators which can explain a symmetry of the physical system. The first operator is the charge-conjugation which can converse the particles into the anti-particles. The second is the parity conversion which can inverse the space. The third is the time-inversion. I mentioned three operators above. But, does the nature conserve C, P and T ? If we answer "yes", then the particles and anti-particles should have the same numbers. However, there are more particles exist than anti-particle in the nature. Actually, anti-particle is not easy to find by using technical instruments. How could we explain this phenomenon? There is one theory that could explain the reason why the nature has more particle than anti-particle. it is the CP violation which is one of the best theorical research area of the professor C.S. Kim in the world. He teached ma a importance of the symmetry in his first lecture. 

      Second, I was very impressed about that the elementary particles, which are called point particles, could make a matter which has a size (i.e. not a point particle). A quark is a point particle. But, it could construct a matter like a baryon. For examples, two up quarks having +2/3 charge and one down quark having -1/3 charge can make a proton having +1 charge in total. Similarly, one up quark and two down quarks can make a neutron which is electrically neutral. Isn't is amazing? It is hard to understand for me at the first time because I think the elementary particle is a just zero-dimensional point. Furthermore, my physical knowledges more close to the classical point of view. All particles have their sizes in the classical mechanics. Therefore, It takes me for a long time to accept the fact that point particles can make a material. 

      Thirdly, I want to talk about several interactions. The first is strong interaction. I had haven't known about what hold the color charges together before I study particle physics. But, now I know that the baryon, which is consisted of three quarks, exists because the force carrier particles (i.e. gluons) interact (i.e. strong interaction). The second is the weak interactions which are responsible for the decay of massive quarks and leptons into lighter quarks and leptons. Although the total mass and energy are conserved, some of the original particle's mass is converted into kinetic energy, and the resulting particles always have less mass than the original particle that decayed. Therefore, the stable matters around us are made up of the quarks and leptons which cannot decay any further. 

      Lastly, I can not help surprising at the grand unification theory (GUT). Strangely enough, current experimental data and theory suggests that the various fundamental forces merge into one force when the particles being affected are at a high enough energy which is GUT scale. There is no doubt that the history of the particle physics was started to unify the fundamental forces. The fact that the various fundamental forces merge into one force made my blood run cold all over. Furthermore, it give me a life direction. So, I seriously think about studying in the particle physics. 

      So far, I mentioned about what I learned and what I was impressed through the particle physics class. I have a great passion to study on the theorical particle physics after I took this class. If I got a chance to study on the particle physics, I would have made a beautiful equation which could offer an elegant understanding of the organization of the universe. Thank you professor.