Yang prospects and learning physics

 Yang: Prospects and learning physics
:2005-02-05 Author: Source: Science and Technology of China
mm lecture at Qinghua Yang
Dear students, I was moved to 1929, when seven Tsinghua to live. my father was then a professor in the Department of Physics, Tsinghua University. Tsinghua University and Peking University are much smaller then than now. I guess Tsinghua Park area of only one-tenth now. two gates south of the river, Tsinghua University was the boundary. from Xizhimen, the zoo until the middle of Beijing University and Tsinghua University, basically the house some farmland and farmers, and some small town. then movie theaters are in town, so I remember very clearly, each a week in the auditorium of Tsinghua play a movie, so for this auditorium I was very familiar. I Tsinghua total from seven to fifteen-year-old lived for eight years. I had just walked into the auditorium, pushing open the door came in, I smell the auditorium of the taste, the taste more than seventy years ago with the smell I smell is the same. So you can think of many places I have very cordial Tsinghua feeling.
Of course, the world has changed much of the .1938 to 1942 I read in the Southwest when the undergraduate physics, the whole system together, and even graduate students, including less than 50 people. I think it should be a time scale times or even twenty times. That was when the war, the conditions we live, classroom equipment, library case, are incredibly simple. But perhaps the biggest difference with you today, is not this, but the atmosphere is not the same. At that time is at war, often Japanese planes to bomb, the future is very optimistic, the future of each of us are shrouded sense of urgency. In contrast, the era of your life today is really a great era, I I believe each one of you has to be some understanding of this point.
physics I then went to the United States, here I go I talk more about the Institute of American Studies of the physical and your face today between the physical significant difference. I went to the United States in 1945, from the perspective of the development of physics, the first four decades of the 20th century is the history of a golden age. At that time we all know, the 19th century Maxwell [1], Boltzmann [ ,],[inside there are some natural cloud sky [4]. If you have seen in 1904 in St. Louis opened the records of an international seminar, you can know that when the danger of the collapse of the whole of physics are. because in the 19th century, although people know a lot, especially in electromagnetism and statistical mechanics, but still can not explain the phenomenon. The most important of the two phenomena I think we all know, one is the Michelson and Morley [5] experiment with the concept of ether has direct conflict. The other is an electronic transfer in atoms around the nucleus, it is at all times acceleration, an acceleration of the body should always have the electric radiation, so the energy is getting reduced. In this case, the electrons around the nucleus Go inside to be more, because its energy is smaller, and finally will hit the nucleus up. and then experiment with this phenomenon is completely inconsistent with. People do not know anything at this issue. This was is an obsession, but appears to be an opportunity today. What chance? this phenomenon is that people can create out of the new, revolutionary principles. We all know that the first 30 years in the 20th century produced the new, previously unimaginable things developed, so I'm at home and abroad to lecture some students often say that the history of physics is concerned, the first three years of the 20th century was a golden age; I went to the United States after that is, three decades after World War II is a Silver Age. Silver Age can not be compared with the golden age is not as golden age that produced can do many things, such as nuclear physics, atomic, structure of elementary particles, solid-state physics and other areas of new discovery and invention of the laser are 1945, three decades after the achievements.
After understanding the above these, we can ask the students present here today facing the prospect of Physics What is it? three decades after what direction will the development of physics? I think this issue is for you very, very important, because you will work with the answer to this question is closely related. of course, no one can speak for the future out entirely accurate language. but I think can see that, after three decades of physics The nature and just talked about the development of the golden age, silver age are not the same. Why is not the same? because frontier of physics now becomes very wide. why change widespread, because just about the golden age and silver Time to expand the frontier of physics. This broad is bad for you is also good. bad is it? will make a very wide area that you know what to do, do not know what direction to develop. What are the benefits? If you are in many in the direction of the path chosen for you, you can do a lot. can do today, compared to the early 20th century, compared to when I make post-doctoral, much more, and today the relationship between academic and social even closer. speak it plainly, then the opportunity is now much more rich. Golden Age and Silver Age open new avenues for a very, very much. if you found it at a certain opportunities, can make great achievements, and create a lot of wealth. This is an obsession, but it also brings opportunities. The most important is that everyone must understand this point, know that today the development of cutting-edge physics, with the 20th century, not the same 80 years ago. < br> If you do not understand this point, then choose your future path for the negative; if you accept what I have said, they would draw an inference. The inference is that, you have to pay attention to ways of learning, which traditional The method is not the same. we all know, Einstein wrote a few revolutionary 1905 article. He then focused on several things, each thing that he later made a revolutionary contribution. One is the photon ; one is special relativity. Now we know that Einstein and his first wife in 1900, still in love during their correspondence, it was found, and published. If you read the words of these historical materials , you will find, as early as 1899, when Einstein had an interest in the dynamics of power. forefront of the issue at that time relatively specific, relatively small, plus he has the ability, insight, and chose this subject So there will be a great achievement. Today is not the case today, could not speak to the field of physics in the next decade or two decades will be a huge development in a certain direction. So, as I just said the same, and this is your Select a troubled future. But know this, they you will know what kind of measures should be taken that interest must take place widely relaxed. If you have only one or two opposite direction, then You will have few opportunities.
at this point in the learning of Chinese and Western, especially American way of learning is fundamentally different. Methods of study in China by the Chinese philosophy of education has been to children to the professional direction. This tradition with the United States are very different. American Comparative faire, let the children to develop. such a difference to the college will clearly see the future. U.S. college students, first year students, Their interest is very broad average, something they know everything that. They have relatively wide net scattered, result is that they will not test, it is known. and China will test the students are, and why ? example, secondary school students in China triangle will do a lot of exercises. Although the United States high school students know the definition of sine and cosine, but they will not do exercises. they receive is a relatively broad knowledge, but not depth. You have to understand the results of both methods of education in their own short-long. From the perspective of the examination, of course Chinese education is very good. We all know that from China to the United States students studying very good, like I heard that American students at Berkeley home after a parent asked what course he chose, asked him if he did not choose a very important lesson, he said that did not choose, the parents asked him why he did not choose, he Course places that I see in three Chinese students chose this course, I knew I should not be re-elected on. But they know something is very much aware that many areas of some things. this I also have some personal experience, and not from the beginning today, when I went to study in America to have seen this phenomenon. I remember very clearly, I live in Chicago in early 1946 called International House (student apartments), There were many graduate students live in it. University of Chicago, near a skating rink, ice skating in winter. When I go skating met a mathematics students, called Le Nick. slip finish after we had an ice speculation. So he would go to my house, and the results we have been talking about the next morning. he was gone, I think this man is simply amazing, he knows I've never heard of a lot of mathematics and physics in the latest things. If you go to the United States, students often see this. But I soon discovered that he was speaking for himself those things as clearly and logically, simply do not understand, that was quite superficial, so wait until later Examination of the time, Chinese students accepted the benefits of rigorous training that come. then should not they absolutely wrong about this approach? Otherwise, this approach is also good. and this benefit under the current situation is Like I mentioned earlier a lot of doors open, the intersection of different disciplines can produce important results and more incredible circumstances, learning to U.S. students had advantages. I'll give you a few examples, I think If we have not done their own CAT-scan (layered scanning, commonly known as to medicine is also very interested in, and studied the theory of X-ray effect, put together these types of studies, and later developed a CAT-scan, and received the Nobel Prize. Another example is last year by the Nobel Prize is the NMR (Nuclear Magnetic Resonance Nuclear Magnetic Resonance, NMR), now known as MRI (magnetic resonance imaging Magnetic Resonance Imaging, MRI), the MRI of a person called Lao Tebo winning (Lauterbur), he told me at Stony Brook (New York University Stony Brook) is a colleague. he younger than me, is the Department of Chemistry, a young assistant professor. of course, because he is a chemist, so the MRI technology that very clearly. but he is also very interested in the calculation, and he absorbed the basic concepts of CAT-scan, so he wanted to why I could not have done a scan, the MRI can scan cancer cells. So he thought a very clever way is to use a gradient magnetic field. This is a Interestingly, opinion, and if you do not understand, you can easily find a teacher, five minutes, the gradient magnetic field scan can solve this problem why do you understand. He used only a small test tube and a magnetic field, The results of today's MRI was born. This story tells you that plenty of today, a little wide if your interest, you can put several things combined, and then get out of things that never had or views. So In today's circumstances, everyone should go to the general direction of development, which is under the Chinese education system is particularly important to young people growing up.
Professor Zhu talked about just one thing, I heard later very surprised. He said the department is now ready to set up an academic report class, hope that every graduate student is to listen, I heard that some students opposed to, I think this is simply incredible. because if there are ten times a semester, academic reports, even if you go listen to ten times and spent twenty hours, and twenty hours of investment is very small. I know that in the United States also has such a phenomenon, many students do not like to attend an academic meeting. For example, in Stony Brook, every week have an academic report, many Chinese students do not, I asked them why they do not, they said I went to did not understand. I said I went to often do not understand, but this does not matter, you did not this time understand, after three months again, and hear another speak a little different, continuous listening to on several occasions, it will be harvested, and this gain is very important. I got up this approach to learning name, called immersion learning. Chinese traditional educational methods do not focus on immersion learning, and indoctrinating value of learning, which is the onslaught, which of course has its benefits, but the permeation study is also very important. You see a child, why language learners faster? not because he understood every word, but because he listened to a word, after a few hours and listened to a word, he came to the end of each all together, then, to understand. The age of learning to a larger time to gradually lost. and I think this is a very important learning method. particularly in the more widely the knowledge required cases, this method is very important for graduate students. So I think every graduate to their own, should be very willing to listen to each lesson, each academic report. do not know does not matter, after hearing a lot of naturally there will be some gains, it is very important. As you are not to be subject to the provisions of the department to hear, I think to spend twenty hours a semester to go to is not a great investment. On this point, the the United States and various parts of speech in the country, I have repeatedly say. I think has a lot to see Popular Science Writings, I especially recommend the Scientific American (translation, you have to look at this I think is very useful. read this book you will encounter the same problem, because it is more than content, including physical, there are many biological knowledge. in a field of articles you may today do not understand, but after six months then you do not read another one, and watched a couple of years, you will of that area a little more understanding of things. All in all, I want to say is, today, is to the forefront of academic broad direction, the direction of the cross-disciplinary. Each student must understand the situation and try to broaden their interests. I know that Tsinghua students academic performance is very good, so I believe that you are here after graduation, the degree obtained degree, a master's degree or PhD later, in the decades ahead, as you recall, the Tsinghua students will feel very memorable time. A part of the students asked:
Q: I am a graduate student instructors how to deal with differences? Specifically, their research interests without the support of instructors, himself a separate study that can not afford their own interest, at this time how to deal with?
A: The students have some problems, he not the first encounter troubled students, I think all students, or graduate students doing most of the time students will encounter some problems. just read part of Professor Zhu Huang Kun wrote me a letter. He gave me the reason why write a long letter, because before that I wrote him a letter a long letter. I do not have a copy, so I do not remember clearly his letter to write something. But to this from the Huang Kun the tone of the letter point of view, obviously I was not too happy, and feel a bit disappointed. then I certainly remember my time doing that thing in 1947. I had to ship to the United States, I to the direction of the United States to do it. I said to myself, I did not learn in the country of Experimental Physics, so I'm going to write to the U.S. after a paper on experimental physics. to the United States a few months later, I to a professor's lab named Allison, when he is engaged in a four hundred thousand electron volts of the accelerator. I spent in the laboratory one and a half or so. year and a half I did not succeed, written in 1947 to Huang Kun When the letter was when I was a bit anxious. Now I see Kun Huang's reply that he was also some loss of place. now get the consent of Huang Kun, I made it out in particular, because as I have the last word in writing, as is the hope that today's students to a letter from me and Huang Kun get some encouragement and inspiration. what inspired it? disappointed the original era of graduate students, less happy, the feeling of loss is normal, do not think it is to the end of the world.
and mentor if the relationship is not good, how to solve it? this I think there is no fixed way. I do not know the rules in this regard Tsinghua University in the United States, if a student with the tutor relationship is not good, then the student can go to choose another mentor, no teacher can hold the students. did not say if he does not agree with the original mentor, he can not change instructors. If the students do research in peacetime, the time has for a year's course, but also learn better, then he went to another teacher, another teacher is also very good impression on him, then it may have been willing to accept him, so often the case everywhere. I For graduate students for the past know, on the instructor, for professional, even for very complex systems have many rules, I always think of these regulations is appropriate to relax. I taught at Stony Brook books for decades, to see some students doing not happy, but after the very successful for instructors.
I have a graduate student, called Yu Li-hua. He is about to Stony Brook in 1980. He is very successful. he went to do after I graduate, he feature is that they have very strong self-study habits. I soon discovered that I let him do his job is not interested, he wanted to study the problem is the interpretation of quantum mechanics is the measurement right. So he to come and talk to me, that the Cultural Revolution in China when he was sent to rural areas, had been thinking about this problem, so that very much. I told him you could write a paper on this issue, but this area is too cold. If you do the research in this direction, I can agree with you in the future, obtaining his Ph.D., but may eventually find a job, I do not you study this. I remember when he was very upset, we adhere to for a long time . Later, thanks to him for other things and interested in, is on the accelerator design, and received a doctorate in that area. This is what I very much agree, and he has made in that respect is a very important work. He design of free electron laser, it is most likely to truly achieve the X-ray free electron laser is one of two ways, and I think his method is better. I think it may be another five years or eight years, if the world The first X-ray free electron laser, then there is the so-called Li-hua Yu HGHG (high-gain harmonic generation free electron laser) methods. Today, I asked him then I will not let you do the measurement in quantum mechanics is not right, he also admit that my opinion is right.
I have talked about my own laboratory in Allison's successful year and a half. I would not disagree, and Allison has a place, and the year and a half to I have brought significant benefits, first of all let me know I should not do experimental physics, because many of my classmates as from the experiments easier, but I made it very difficult, but I began to be much better than they exercise to . Finally, Taylor (Teller) to help me solve the problem, he was a professor of Physics. we all know he was famous because he invented the principle of the U.S. hydrogen bomb. He told me one day to listen to that you do not experiment a success. At that time there are two hundred graduate students, Department of Physics, we are familiar with the teacher for the students very well, I was a graduate student in physics is well known, because the Chinese students suddenly come theoretical learning was very good, so we are aware of me. He asked me hear you do not succeed, I said. He said, why should you have to do a paper about the experiment? You have selected a articles, Take this article as your thesis, you can get doctorate. I say thank you, but this not the same as my mind, I have to think about. The results to two days, I think we should accept his recommendations. and made the decision, I relieved. Why relieved? Because I know that my future is not in the development of experimental physics aspects. just not my year and a half on the white out? not, because it Although there is no one and a half make me an experimentalist, but the values for an experimental physicist, that is what they all want, what difficulties they face, I have a personal experience. This is my work later a great help. I received a doctorate in 1948, 50 years later, I often go to the laboratory of experimental physics and those who do talk, knowing what they are doing experiments, what results have been obtained. This and I am 50 years of research done by a very close relationship. Therefore, the students asked me how they deal with the above, I do not think Yigai answer, if we can go to one closer to their own ideas and the direction of course very good. but can not and mentors to talk about it? analysis of why there might be another way to dispute. you ask this question is very important, but I do not think a general answer.
Q: that in the next three decades, similar to relativistic physics would be such a revolutionary breakthrough? If so, you think the most likely to occur in any place?
A: This is a good question, I have a very direct answer, I think this possibility is very small, of course, can not say absolutely impossible.
Why do I say? Because the theory of relativity arise, that is, 100 years ago, there are several major must not understood. If those things are not understood, the physics of the past to collapse. and in fact especially in quantum mechanics to the 1923-1924 years, when, Heisenberg [6] in the 70s when he was older There are some description, he said that time we were very disappointed that the humans have been impossible to know the structure of atoms. This is evidence that they are very disappointed, but now we know what the outcome is concerned, they catch up with the best opportunities. The more severe difficulties, the greater the chances. Well, today we have no such difficulties? course, there are, say, dark matter (dark matter) is a very troubled human thing.
today, when not the same with that where it is difficult to do experiments, not you spend tens of thousands of dollars, hundreds of thousands of dollars can make a new spectral aspects of the experiment. 20 years in Germany, so that quantum mechanics developed, mainly because Germany was the spectral learn very advanced. They did some new experiments, these new experiments in this appears to have only few thousand dollars of the experiment, it is very easy to do, a professor with a graduate student can do. and today need to experiment As just about the dark matter, not one or two people is not even a country can do. Therefore contrast, can achieve a breakthrough today, a very low probability. you ask me such a breakthrough might occur in any place I think that after three decades in the field of physics, made an important contribution to the most likely place to be is the application of direction, I can not believe that the fundamentals of being found out. and now the direction of application of a very, very much like the last seven eight years, the hottest subject is BEC (Bose-Einstein condensates m), BEC inside the changes are very much of it to the laser have a significant role in the promotion. So I think in this field the possibility of a breakthrough is relatively large.
Q: For the physics theory of physics students, particularly students should first have the math or the math skills of thinking? A: This question is like this, mathematical skills and mathematical thinking is divided not open. If a student wants to do a good theoretical physicist, learning a lot of mathematical knowledge is very natural. such as a very important field of physics today is an issue of group theory, so I know that many engage in theoretical physics graduate students to learn group theory of knowledge. read a lot of group theory, you can easily be attracted by the mathematical way of thinking, because the group some ideas on the inside is really admirable. but if your desire is to do theoretical physics scientist, then you read a lot of mathematics there is a danger that you will gradually transfer your values to the values of mathematics up. transferred to the mathematical values is flawed, which is from several decades of mathematical physics literature can be seen. because they are too many values like mathematics, physics, there can not give full attention to the tendency of the values. so this is a problem. Of course, if you are attracting the values of mathematics can do in mathematics the important contribution is good, but this and that you wish to make a difference in theoretical physics have a different idea.
Q: I am a sophomore, is now very confused like us What do people how basic scientific research to consolidate their interests, strengthen our ambitions do?
A: I think the sophomore students are obviously very hard. Generally speaking, China's university students and the same grade American college students than can be said that much effort. and feel the pressure by parents, school stress and social pressure than the average American student to be more. so I answer for his sophomore is: Maybe you should relax, too tight is not necessarily a good thing for you. I go to school in Chicago when my mentor was Taylor (Teller). just go when I did months of research and his work, he has five or six graduate students, We go out every week to eat a lunch, he just like to talk about each graduate, and asked each of us doing in the research. I soon found that his words were frequently asked Are you having fun? This species concept in the Chinese education system is not under the Chinese pay attention to willing to discuss with anyone. way I meet you tell you he will catch you a certain symmetry of a molecule, we put it all wrong, and he'd tell you a pass. His speech is often justified, but Often there are mistakes. If you point out his mistakes, he is willing to accept, he will go with you to continue the discussion, so you can write an article. This attitude and the Chinese people's concept is not the same, China people often say that the thought and clearly do not make the opening. He learned attitude is that scholarship is a very interesting thing, is a time to discuss with anyone. And I think that today's University of China should focus on the establishment of this concept.
[1] James. Clark. Maxwell (James Clerk Maxwell ,1831-1879), British mathematician and physicist, founder of electromagnetic theory.
[2] Ludwig. Boltzmann (Ludwig Boltzmann ,1844-1906), Austrian physicist, the energy equilibrium distribution of gas molecules by law established.
[3] Gibbs, (Josiah Willard Gibbs, 1839 -1903), American theoretical physicist, statistical ensemble theory pioneer.
[4] 19 century, the last day of the famous European scientists together. At the meeting, British physicist W. Thomson (that is, Kelvin Lord) published a New Year message. He recalled the great achievements of physics, said that the physical building has been completed, just some modification of the remaining work. Meanwhile, the prospect of 20th century physics in his prospects sermon: theory of heat and light is definitely a movement in two ways, and now it's beautiful and sunny skies clouded been two, two dark clouds appear on the equipartition of Maxwell - Boltzmann theory. The first flower that cloud, mainly refers to A. Michelson and ether drift experiments that contradict the second duo clouds, mainly refers to the thermal energy equipartition in the set and the specific heat in the gas potential of radiation theoretical interpretation of spectra obtained with the experimental results ranging, particularly in emerging theory of blackbody radiation, affect the authority of physics, he says points to the development of physics to the basic situation the late 19th century, reflecting the physics community at that time the main trend.
[5] 1887, the United States two experimental physicist m Qieer Sen and Molly (Michelson-Morley) completed a famous experiment to prove that walking and carrying light along the Earth's speed of walking the earth exactly the same speed no matter which direction are the same.
[6] Weiner. Carl. Heisenberg (Werner Karl Heisenberg ,1907-1976) German theoretical physicist, the first effective form of quantum mechanics (matrix mechanics) of the founder.
speaker biography
Yang (Zhen Ning Yang) , Master in Physics, Nobel Laureate .1957 and Lee proposed in the gauge field theory, then in 70 years to become stronger integration and understanding of elementary particles, the weak, and electromagnetic interaction of three basis; addition and has worked in statistical physics, condensed matter physics, quantum field theory, mathematical physics and other fields to make more a significant contribution to the outstanding items.