What does "physical" mean?

This is a very basic question. Open any physics textbook, it is not difficult to find such a definition: physics is the study of the structure of matter, the interaction of matter and the laws of motion of the natural sciences. But this is only for the science of physics in the academic sense of a definition. And we are facing the "physics", it is also a course, so it is necessary to go from the level of educational significance to carry out some re-understanding, re-analysis, in order to explore the richness of the connotations embedded in it.

First, physics is a science.

Physics is a natural science based on experiments, it is the most mature development, highly quantitative precision science, but also has a methodological nature, is recognized as the most important basic science. The results achieved by physics have greatly enriched people's understanding of the material world and strongly contributed to the progress of human civilization. As stated in the resolution of the 23rd Congress of the International Union of Pure and Applied Physics (IUPAP), "The Importance of Physics for Society", physics is an international endeavor that plays a key role in the future progress of mankind: to explore nature, to drive technology, to improve life, and to cultivate human talent.

The establishment of the theory of relativity and quantum mechanics at the beginning of the last century gave wings to the rapid development of physics and achieved unprecedented success, so much so that the 20th century has been called "the century of physics". What is the 21st century? There is a popular saying: the 21st century is the century of life science. In fact, a more accurate expression of this sentence should be: the 21st century is the century of physical science fully involved in the life sciences. Life sciences only with the combination of physics, it is possible to achieve greater development.

The future of physics is full of opportunities and challenges. Mr. Li Zhengdao, in his article "The Challenge of Physics," has put forward four major problems facing the field of physics in the 21st century: Why are some physical phenomena theoretically symmetrical but the experimental results asymmetrical? Why half of the elementary particles cannot exist alone and are invisible? Why is more than 90% of the matter in the universe dark matter? Why is the energy of each quasar 1015 times that of the Sun? These questions have greatly inspired people's courage and enthusiasm for tireless exploration. It is foreseeable that once these dark clouds in the sky of physics are removed, physics will show a brighter future.

Secondly, physics is a kind of intelligence.

Sincerely, as the Nobel Prize winner in physics, the German scientist Bohne said: "If it is because my published work contains a discovery of a natural phenomenon, it is better to say that it is because it contains a foundation of scientific thought and method about natural phenomena." Physics is recognized as an important science not only because it has made a profound revelation of the laws of the objective world, but also because it has formed a set of unique and fruitful system of thought and method in the process of development and growth. Because of this, making physics deservedly become the crystallization of human intelligence, the treasure of civilization.

A large number of facts show that physics ideas and methods are not only valuable to physics itself, but also have an important contribution to the development of the whole natural sciences, and even social sciences. It has been calculated that more than half of the winners of the Nobel Prizes in Chemistry, Biology and Medicine, and even Economics since the middle of the 20th century have had a background in physics; -- which means that they have drawn their intelligence from physics, and turned to success in non-physical fields. -- In turn, no instance has ever been found of a scientist with a non-physics background asking for the Nobel Prize in Physics. This is the power of physical intelligence. No wonder some foreign experts have pointed out very pointedly that a nation without physical training is a stupid nation!

Today, the tentacles of physics has been extended to many fields, and has made more and more achievements, so that we can hardly use the traditional vision to distinguish what is physics. 1995 in Xiamen, China, held the nineteenth International Congress of Statistical Physics, the exchange of papers on a very wide range of topics, such as plant inflorescences, the DNA drug system, the traffic flow of traffic, the text of the storage, and so on, just look at these titles, and so on. Just by looking at these papers, none of them seemed to be much like physics. What, exactly, is physics? A few years ago, the American magazine Physics Today, asked its readers for their opinions on this question. In the end, the answer they pushed was that what physicists do is physics. This may sound biased at first, but it is not unreasonable. For today it seems that physics is more of an embodiment of intelligence, "representing a set of effective steps and methods for acquiring knowledge, organizing and applying it, and applying this set of methods to whatever problem that problem becomes physics." (Kaihua Zhao)

Once again, physics is also a culture.

Broadly speaking, culture refers to the sum of material and spiritual wealth created in the course of human historical practice. It includes both scientific and humanistic culture. Similarly, a large number of material and spiritual products created by physicists in the course of long-term scientific practice constitute physical culture. Physical culture is an important part of scientific culture.

As we all know, physics is a science based on experiments, its basic research method is to practice, and therefore in the objectivity of the "true"; physics to create the results of the end is to benefit mankind, it reflects the purpose of the "good"; In addition, physics is also to benefit mankind, it embodies the "good"; In addition, physics is also to create the "good". "In addition, physics also reflects the "beauty" in human emotion, consciousness and other aspects. Because physics itself has the threefold attributes of truth, goodness and beauty, we have every reason to say that physics is not only a culture, but also a high-level, high-grade culture.

Physics is true. Physics is most concerned about evidence, physicists in scientific research activities in the most basic attitude is to seek truth from facts, adhere to the "practice is the only standard for testing the truth" principle. As the physicist Feynman said: "No matter how beautiful your ideas, no matter what you smart, no matter how big your reputation, as long as the experiment is not consistent with the wrong, simple, this is science". It can be said that the history of the development of physics, is a continuous correction of errors, constantly approaching the truth of the "truth" history.

Physics is from the good. Physics is committed to freeing people from nature, from the Kingdom of necessity to the Kingdom of freedom, to help people constantly know themselves, and promote human life tends to be noble. This is the value orientation and ultimate goal of physics, and thus the essence of physics is from the good; in addition, the behavior of physicists is also from the good. Albert Einstein once commented on Mrs. Curie and the outstanding physicists represented by her: "The significance of the first-rate people to the time and the course of history is perhaps greater in its moral aspect than in its mere intellectual achievement." Their rigorous and realistic attitude, dedication to science, love of the people and so on, is undoubtedly a particularly valuable human wealth for future generations.

Physics is the most beautiful. German physicist Heisenberg said: beauty is the light of truth; Roman philosopher Plotin said: good is the origin of beauty. From this, physics is beautiful because of the truth, good and beautiful is very natural. The beauty of physics belongs to the beauty of science, mainly embodied in the simplicity, symmetry and unity; symmetry is unity, unity is simplicity, and they constitute the basic aesthetic norms of physics.

Turning over the chapter of physics, can be found everywhere jumping with the note of beauty, reflecting people's pursuit of beauty and creation. Just take unity as an example. The development of contemporary physics is extending in two opposite directions of study: the grandest universe and the tiniest particles. Surprisingly, with the deepening of the research, they are not going their separate ways and getting farther and farther away from each other, but on the contrary, they show a lot of signs of returning to the same place and becoming the opposite of each other. For example, some of the research results of particle physics are often borrowed by astrophysicists, used to explore the image of the early evolution of the universe; (because of this, particle physics in a sense is also known as "cosmic archaeology".) In turn, the study of cosmic physics provides particle physicists with abundant information and evidence. Thus, two opposite branches of physics have been brought together in a marvelous way -- like a python biting its own tail.

As another example, the British physicist Sallack first discovered the following striking relationships between certain physical quantities in nature:

Universe radius/electron radius ≈ 1040, age of the universe/lifetime of strongly decaying particles ≈ 1040,

electricity of a hydrogen nucleus and an electron/gravitational pull of a hydrogen nucleus and an electron ≈ 1040, and

electricity of a hydrogen nucleus and an electron ≈ 1040, and

electricity of a hydrogen nucleus and an electron ≈ 1040. ......

In the above ratios, the universe, the largest system, and the elementary particles, the smallest system, have reached such a perfect unity, allowing us to once again appreciate the beauty of the physical world, a kind of heart-stopping and magnificent beauty. It is this many beautiful examples, inspire people to nature's heartfelt admiration and awe, no wonder Einstein would say: "the universe is the most incomprehensible, is the universe is comprehensible".

Through the above analysis, we have a more comprehensive understanding of physics: it is a science, but also an intelligence, but also a culture. As a physics teacher, can teach their own physics for a comprehensive review and analysis, which is very necessary. On the one hand, we can see that physics has such a rich connotation, which will be more consciously and consciously to dig and develop its function of educating people, and comprehensively improve the quality of teaching; on the other hand, we can see that physics has such a beautiful endowment, which will be more love physics, more passionate to engage in physics teaching. I think, only the real love of physics physics teacher, can do not only teach students to understand physics, application of physics, but also to further guide them to understand physics, appreciate physics.

Two, why teach physics

This is a seemingly simple but very fundamental question, to answer correctly is not easy. The author's understanding of this issue has gone through a tortuous and gradual process from "knowledge-based" to "subject-based" and finally back to "student-based".

For a long period of time, I have locked the goal of physics teaching on the knowledge level, thinking that teaching physics is to pass on as much physics knowledge as possible to students for their future life. Because I believe that "knowledge is power". However, it is puzzling that what physics knowledge we give to our students, many of which are extremely important such as "F=ma", seldom show any direct utility in their future life and work. So much so that after a number of years, many students have forgotten almost everything they learned about physics, in their words, "all back to the teacher". I feel y disappointed; but whenever I ask them "three years of high school is not a waste of time," when cross-examined, these students who have left school for many years, but will be the same voice to make a negative answer, agreed that the high school stage of learning, for their growth plays an important role in laying the foundation, but can not say what exactly the specific knowledge plays a role. But they can't say which specific knowledge plays a role. I think this is probably like dinner, no one will deny the significance of eating for survival, but no one can say, eat this meal is in the body of what place to grow a piece of meat.

A student who graduated more than 20 years ago talked to the author about his "deepest impression" of a physics class. It turns out that the class was about gravitational potential energy. At that time, in order to illustrate the relativity of gravitational potential energy, I had raised this question to the students: someone standing on the window sill of the fifth floor to jump down, do you think it is dangerous? At first we all thought it was too dangerous, but then we thought about it carefully and were all happy: don't jump out of the window, jump in the window and you'll be fine. The student found the example so interesting that he never forgot it; but when asked what physics the example illustrated, he said he had forgotten it. As I was looking on with regret, what he said immediately afterward was reassuring: "This example taught me that everything is relative, and that different perspectives can lead to different results." Although the student had forgotten all the physics knowledge imparted in this class, the ideas and methods condensed through the learning of the relevant knowledge were y engraved in his heart. In this sense, isn't this physics class from more than twenty years ago also extremely valuable to him? After students graduate from high school, most of them will probably say goodbye to physics, and the physics knowledge they have learned will eventually be forgotten, and then they will look back and see: what else does physics teaching leave them? If in their bodies, do not reflect the talent and enlightenment given by physics, it will be the failure of physics teaching. From this point of view, specific knowledge is usually only used as a vehicle for teaching, and there are more things behind the knowledge that are worth pursuing. As our senior scientist Prof. Qian Weichang said, "I studied physics in the university, ....... With physics as the object I learned the ability to investigate and research, collect information, analyze information and logical thinking, the knowledge of physics is sometimes very useful, but these abilities learned through physics are more useful than the knowledge of physics." It was through the vehicle of "physics" that Mr. Qian acquired many abilities that are more important than knowledge of physics when he was a student. Therefore, the view that the teaching of physics is equivalent to the teaching of physical knowledge is biased, and the practice of "knowledge-based" to establish the goal orientation of physics teaching is also short-sighted.

With the deepening of teaching practice, teachers generally become more familiar with the subject they teach, and thus love it. Perhaps because of this professional sentiment, I also once set the goal of physics teaching as "to train as many students as possible to become physicists or physicists". Especially when I was transferred from a rural middle school to a major high school, I was faced with a bright and studious students, this desire is more and more strong. But I soon realized that teachers of other subjects, probably due to their own professional preferences, had similar expectations of their students. As a result, we all cleaned up after ourselves and sang our own tunes, failing to bring together the different disciplines into a single force, and the actual results were of course far from satisfactory. Particularly frustrating to me is that those who are good at physics in the class, "the best students", and then directly engaged in the physics profession is very little. Just when I was at a loss, an example from Mr. Yang Fujia, the former president of Fudan University, gave me great enlightenment. Fudan University had conducted a survey on the destination of nuclear physics graduates, and found that less than one-tenth of the students were engaged in nuclear physics-related work after graduation, while the rest had changed their professions and were active in finance, business or administrative positions. In this regard, most people assert that this is the failure of the Department of Physics, but Yang Fujia believes that this is the success of "Fudan". Because, through the four years of undergraduate physics education, the students have a good quality, laying a solid foundation for their future development, so that after graduation, they can quickly adapt to a variety of different fields of work. This also confirms the words of Mr. Zhao Kaihua: "A person can do anything after learning physics, his physics learning is not in vain. In my opinion, it doesn't matter for people who study physics to 'change their career' ......."

After the above twists and turns in the course of understanding, so that I gradually see the focus of the ultimate goal of physics teaching, neither in the knowledge of the native, nor in the discipline of the native, but should be implemented in our education object - the native of the students.

The question of "why teach physics" can also be asked in turn: "If we don't teach physics and students don't learn physics, what shortcomings will be left in their future development?" One obvious answer is that students will not learn much important physics. This is true, but not comprehensive enough. Because in addition to this, students will also lose the more important training and inculcation of the scientific method and scientific spirit, which will ultimately affect the improvement of their scientific literacy. At present, physics has penetrated into all aspects of society, and has become the knowledge that every educated citizen must know. For most students, I am afraid that the purpose of his study of physics today is not to further the study of physics tomorrow, but rather to help him face or make decisions about the large number of non-physical problems he encounters, and to lay the foundation for a civilized, healthy, and high-quality life throughout their future lives. As stated in Science for All Americans, "The highest goal of education is to prepare people for a self-actualized and responsible life." Accordingly, the most accurate answer to the question, "Why teach physics?" is to teach it to improve the scientific literacy of all students. --This should be our view of physics teaching.

It is well known that biological genes play an important role in the evolution of living things, and that small genetic differences often lead to huge differences between organisms. Inspired by this, many social scholars have been working to find out what are the core elements in the process of human cultural inheritance and development, and thus put forward the concept of "cultural genes", which is defined as the "genetic code" of the human cultural system. The core of cultural genes is the way of thinking and values. The evolution of human beings is more complex than the general biological evolution, and it has a dual evolution mechanism, in addition to the biological gene evolution mechanism, there is also a cultural gene evolution mechanism. Education is precisely an important way to promote the mechanism of cultural genes. The essence of school education is not only the display and interpretation of cultural phenomena, but also the inheritance and development of cultural genes. Physics education is certainly no exception. What, embedded in the physics teaching "cultural genes" in the end some what? The author thinks that it is mainly embodied in three aspects, i.e. scientific knowledge, scientific method and scientific spirit, because these three are the most basic elements of scientific literacy. If scientific literacy is compared to a pyramid, what scientific knowledge is like the base of the tower, the scientific method is the body of the tower, the spirit of science is the tip of the tower. The highest purpose of physics teaching is to add bricks and mortar to build this magnificent tower of scientific literacy. In other words, the core value of physics teaching lies in promoting students to realize three transformations: one is to transform the accumulated knowledge of human society into students' individual knowledge, so that they can know what the world is like and become an objective person; the second is to transform the ideas and methods of the previous generation engaged in intellectual activities into students' cognitive ability, so that they can understand why the world is the way it is and become a rational person; and the third is to transform concepts, attitudes, etc., which are embedded in knowledge into a rational human being. The third is to transform the concepts and attitudes embedded in knowledge into students' code of conduct, so that they know how to make the world a better place and become a creative person.