What is physics?

What is "physics"? This is a very basic topic in the history of science and technology, especially in the history of physics. In recent years, the evolution of the concept of physics has attracted people's attention. Understanding this aspect will give some guidance and enlightenment to professors and learners.

1, the western origin of physical concepts

"Physics" (that is, "physics" in English) first appeared in the book Physics written by Aristotle in ancient Greece. Mr. Zhang, the Chinese translator of the book, pointed out that the book Physics is a philosophy with nature as its specific object. It is different from our present physics, but it includes present physics, including chemistry, biology, astronomy, earth science and so on. In short, it involves the whole natural science, only studies the general principles of nature, and is a kind of natural philosophy "[1]. In view of Aristotle's physics, there are many wrong conclusions in physics, so george gamow, an American physicist who is famous for putting forward the 1949 Big Bang theory of the origin of the universe in the former Soviet Union, once pointed out that Aristotle's "most important contribution in the field of physics may only be to create the name of this subject", which is derived from the word "nature" in ancient Greece [2].

2. The origin of the word "physics"

1900, Japanese Fujita Toyohachi translated "Physics" by Inamori Tingzao into Chinese and published it by Shanghai Jiangnan Manufacturing Bureau. This book is the first Physics in China named after modern physics.

Therefore, it does not mean that there was no "physics" in China before 1900. Modern oriental science, including China, was introduced from the west, but the fact is that it was introduced from the west to China much earlier than to Japan. However, before 1900, the translation of western physics works in China did not adopt the translation method of "physics", and most of them were translated into "physical science" or "practical science" 1883. American missionary Ding Weiliang (Ding Weiliang, English name Martin, 1888) came to China to preach.

A large number of historical data show that "Gewuxue" or "Gewuzhixue" is an early Chinese free translation of "physics" and an abbreviation of the word "Gewuzhixue". The word "knowledge comes from things" comes from Confucianism, which holds that knowledge is based on things and then knowledge is obtained.

It should be emphasized that Japanese scholars pointed out: "It is particularly worth writing that China's modern Chinese translation works have become the basis for Japan to translate western scientific vocabulary." [3] Sang Mu or Xiong Xiong, a Japanese researcher in the history of early physics, said: "Physics was originally called' poor science' in China. During the Chongzhen period of the Ming Dynasty, he wrote a book called Little Knowledge of Physics, including astronomy, meteorology, medicine and so on.

In April, 2002, China International Symposium on Retrospect and Prospect of Modern Science and Technology was held in Beijing. At the meeting, some scholars still think that translating "physics" into "physics" is more in line with China culture than translating it into "Wu Ge" or "Gezhi". However, the word "physics" is gradually accepted by China people. 1902, Shi Jing University opened a physics course in Gezhi. 19 12 years was changed to science and physics was set up. In the same year, Jinling University opened a physics course, and in 19 18, the Commercial Press published Huang Chen's Physics, which was the first book named after physics in China. It can be seen that the translation of "physics" into "physics" in China is still relatively late. 1900, Planck, Germany, put forward the energy quantization hypothesis, which marked that physics crossed the modern door and opened the prelude of quantum mechanics.

It must be pointed out that the word "physics" appeared in China not too late, but its meaning is different from that of "physics". Lv Kun in Ming Dynasty (1536- 16 18) wrote Groans, in which the second part of the sixth volume is called "Physics", which is generally related to physicalism and is used to extend some views on human nature and the world. Zhu in Song Dynasty (1 130-65438) In fact, Yang Quan, Wu Ren, wrote a book "On Things" in the Outline of the History of China Philosophy (Zhonghua Book Company) co-edited by the Institute of Philosophy of China Academy of Sciences and the Department of Philosophy of Peking University, which was a work to study and comment on astronomy, geography, technology, agriculture and medical knowledge at that time. Earlier, in the book "Lan Mingxun of Huainanzi" written in the second century BC, there was: "The fire in the tunnel is in the sun, and the stone absorbs iron, and the sunflower is facing the sun. Although intelligent, natural, so the eyes and ears are not enough to distinguish physics; The theory of mind and nature is not enough to decide right or wrong. China's ancient "physics" should mean everything.

3. General traditional understanding of "physics"

According to most general physics textbooks or dictionaries, physics is a theory to study the most general laws of material movement and the basic structure of material. Specifically, it involves mechanics, acoustics, thermal and molecular physics, electromagnetism, optics, atomic and nuclear physics, elementary particle physics, solid state physics, gas and liquid research, etc. Physics includes experiment and theory. Theoretical physics proved to be reliable by practice includes: theoretical mechanics, thermodynamics and statistical physics, electrodynamics, relativity, quantum mechanics and quantum field theory. Of course, these theories can only be relative truths and have their own limitations. Using the basic theories and experimental methods of physics to study various special problems, various new branches of physics are constantly emerging and forming, such as fluid mechanics, elasticity, radio electronics, metal physics, semiconductor physics, dielectric physics, superconductor physics and so on. With the wide application of physics, some frontier disciplines have been formed, such as chemical physics, biophysics, astrophysics and marine physics.

As a discipline, the existence of physics must be based on the following elements:

1) Understand and explain the descriptive view of nature through the interrelationship between natural phenomena. This view of nature is based on two beliefs: first, nature has rational laws that can be recognized and understood by people. "It is the basis of all scientific work to think that the world is orderly and identifiable in essence." Einstein's words; Second, I believe that nature is real and almost constant, not an idealistic dream or an illusion of the conceptual world.

2) There is a quantitative method system suitable for the above-mentioned natural view to deal with the phenomenon, especially allowing approximate quantitative treatment. Specifically, it is axiomatic logic and practical and operable mathematical system, which can be said to be the skeleton of scientific theory.

3) Pay attention to experiment, which is not only the source of theory, but also the judge of trial theory. Without the element of experiment, even if science can be born, it can only be a closed theoretical framework. Although it may be logically self-consistent, due to the lack of verification or falsification mechanism, it is easy to become a fantasy and lose the vitality of further development.

4) Social and cultural needs.

4. Interpretation of "Physics" in Encyclopedia of Physics

The American McGraw-Hill Book Publishing Company published the Encyclopedia of Physics edited by Parker for the fifth time in 1983 (Science Press,1August 996). The main points about physics in the book are as follows:

Physics used to be called natural philosophy. Physics involves some aspects of nature and can be understood in a basic way, that is, according to some basic principles and laws. With the passage of time, different special disciplines have separated from physics and formed their own research fields. (Typical differential theory, author's note) In this process, physics keeps its true colors: understanding the structure of nature and explaining natural phenomena.

The most basic parts of physics are mechanics and field theory. Mechanics involves the motion of particles or objects under a certain force. Field physics involves the origin, essence and characteristics of gravitational field, electromagnetic field and nuclear force field. Mechanics and field theory together constitute the most basic way to understand natural phenomena in science, and the ultimate goal is to understand all natural phenomena through these two aspects.

The ancient or classical division of physics is based on some general types of natural phenomena. At that time, people already knew that these natural phenomena were particularly suitable for studying by physical methods. According to this classification, there are classical mechanics and its branches, celestial mechanics, fluid mechanics and ballistics. Heat and thermodynamics; Gas motion theory and statistical mechanics; Optics, acoustics; Electricity and electromagnetism. This division is still popular now, but many of them tend to be included in the branch of applied physics or technology, which is increasingly divorced from the inherent branch of physics itself.

Mathematical physics uses mathematics to study physical phenomena, which includes all the more mathematical parts of physics and most of the contents of statistical mechanics, quantum mechanics, relativity and field theory. Generally, the difference between mathematical physics and theoretical physics is that although the latter is both mathematics in form, it is considered to be closer to experimental physics. However, neither mathematical physics nor theoretical physics can really be divorced from experimental physics, because a complete understanding of nature can only be applied at the same time.

In all fields of physics, its characteristics depend not so much on the content of the subject involved as on the accuracy and depth of the understanding of the explored content. The purpose of physics is to establish a unified theoretical system through mathematics, and its structure and behavior should reproduce the whole nature as widely as possible. Other sciences are only satisfied with describing and connecting various phenomena with the special and limited concepts of this discipline. On the other hand, physics always tries to understand the same phenomenon as a special form of expression as the basic unified structure of the whole nature. According to this purpose, physics is characterized by precise instruments and equipment, accurate measurement and mathematical expression of results.

There is obviously something wrong with this characteristic theory of Encyclopedia of Physics. It is said that characteristics should be unique, but can you distinguish physics from chemistry by this? Chemist Hirsch Bach's words help us to distinguish between physics and chemistry in a sense:

"A typical chemist's overriding desire is to understand why the behavior of one substance is different from other substances; On the other hand, physicists usually expect to discover laws other than specific substances. "

5. Asanaga Ichiro's view of "physics"

Ichiro Asanaga (1906- 1979) is a Japanese theoretical physicist who won the 1965 Nobel Prize in Physics for his contribution to quantum electrodynamics.

1977 10 is the anniversary of the establishment of the Japanese Society of Mathematical Physics 100. At the commemorative meeting, Chao made a report entitled "What is physics" [5]. But he only talked a few paragraphs about the history of physics and the relationship between physics and technology, and did not directly answer this question (at least from the Chinese translation). He said, "However, it seems that it only started in the period of Kepler, Galileo and Newton." Kepler mainly studies the motion of planets around the sun, but Galileo, unlike Kepler, studied phenomena on the ground. Newton concentrated their achievements, conducted in-depth research and established Newton's three laws and the law of universal gravitation.

Chao believes that modern physics has two properties: one is to adopt the method of observation or experiment; Second, use mathematics to express the law.

He believes that we should use physics to understand the laws that exist in the depths of nature. When considering what physics is, this idea cannot be ignored. Chao emphasized that the further development of physics not only expanded its scope, but also developed from mechanics to light, heat, electromagnetism, atoms and molecules, and even chemistry. There is a tendency to unify all phenomena and synthesize all disciplines. We might as well call it unity theory, not differentiation theory. The famous physicist Rutherford also famously said, "All sciences are either physics or stamp collecting." [6] This can be regarded as the simplest definition of the theory of physical unity.

6. The viewpoint of Copenhagen school.

Although the above viewpoints are different, they do not violate Newton's statement: "The purpose of natural philosophy is to discover the structure and function of nature, and to reduce them to some universal laws and general laws as much as possible-to establish these laws through observation and experiment, so as to deduce the cause and effect of things. [7] In other words, the purpose of science is to discover objective natural laws or truths that have nothing to do with people.

This idea has been impacted in the micro field.

In this field, the influence of observation on phenomena can not be ignored. Therefore, the Copenhagen school of quantum mechanics represented by Bohr (N.Bohr) and Heisenberg (w.Heisenberg) asserts that the task of physics is to find out what is wrong with nature. Physics involves what we can say to nature. "The purpose of describing nature is not to prompt the true nature of phenomena, but to put all aspects of various experiences into it as much as possible." Natural science is not nature itself, but a part of the relationship between man and nature, so it depends on man and is branded with man "(Heisenberg) [8]; "When you seek the harmony of life, you must never forget that in the drama that exists, we are both actors and audiences. , (Bohr) [8]. Obviously, the scientific view of quantum mechanics has changed greatly compared with its pre-physics.

7. "What kind of physics will we choose in the future?" Related ideas of the article

Nan M.Gruner and J.S.Langer published an article entitled "What kind of physics should we choose in the future" in Physics Today 12 and 195, arguing that the evolutionary definition of physics concepts is becoming narrower and narrower. In order to save physics, physicists now define physics not according to those specific majors and fields, but based on those different periods and fields.

L) Advanced training in a series of core disciplines, such as mechanics, electricity, magnetism, thermodynamics, statistical mechanics and quantum mechanics.

2) Mastered the quantitative methods for studying physical phenomena and the methods for sorting out data.

3) Strong abstract ability, courage and spirit to break away from convention, go beyond the insight of specific research objects and grasp the essence of the problem.

These conceptual tools can distinguish physicists from other scientists more than any other features and standards. The most obvious difference between physicists and other scientists lies not in their fields and research problems, but in the research methods they adopt and the characteristics of the information they seek. Astronomers study pulsars, biologists study life systems, and physicists care about both, so both are the research objects of physics.

8. Mr Zhao Kaihua's point of view.

Looking at the expansion of the research object of physics in the 20th century, from macro to micro, from traditional physical process to chemical process (quantum chemistry), from inanimate to living ... From different angles, there are both differentiation and unified integration of disciplines, and the differentiation theory and unified integration theory are both reasonable and based on facts. They are by no means either or, nor are they mutually exclusive. The development of unified and differentiated disciplines in breadth and depth marks the maturity and unity of local scientific development. A foreign physicist humorously asked himself: What is physics? Physics is the work of physicists. Logically, people should continue to ask: What is a physicist? The answer can be given by referring to the physicist * * * isomorphism concept of Gruner and Langer mentioned above.

Mr Zhao Kaihua said [9]: "I want to add a note to this sentence. How can the research done by physicists be considered as physical work? It is a sufficient condition that the paper can be accepted by internationally recognized physics magazines or physics academic conferences. " 1995 The 9th International Conference on Statistical Physics was held in Xiamen, China. In the summary of the meeting, there are words that are not like the physical terms in the traditional concept. Such as bacterial growth, biological evolution, biofilm, verticillium cells, cytochrome C, El Ni? o, Southern Oscillation, red blood cells, heart rate, why birds fly together, immune network, winding river, neural network, sand table model, traffic flow, etc. "Visible, today can't use the research object to define what physics is. Physics is the theoretical basis of all natural sciences and engineering technology. Physics represents a set of effective steps and methods to acquire, organize and use knowledge. When this method is applied to any problem, the problem becomes physics. " [9] This is similar to Gruna's and Langer's spiritual views.

There is another phenomenon that has influenced people's views on physics for many years.

Nowadays, many physics majors do not engage in physics after graduation, which requires that physics must be changed accordingly. 1996 international college physics education seminar was held in the university of Maryland, USA. Statistics released at the conference show that more than 60% physics graduates in the United States have entered various industrial sectors, and more than two-thirds of those who have obtained bachelor's degrees do not work in physics. Statistics in Britain are generally similar to those in the United States. This phenomenon also exists in China. According to the traditional view, this is a waste of talent training. Mr. Zhao Kaihua thinks this is normal. He said: "A person can do anything after learning physics, and his physics is not for nothing ... In my opinion, it doesn't matter if he studies physics, ..." [9]. China Daheng Group. People who can master the four mechanics will achieve success in any profession as long as they work hard. Physicists are especially suitable for high-tech development and innovation. "[10] The statements of Mr. Zhao and Mr. Song Er can only be correctly understood on the basis of breaking the past understanding of physics specialty and thoroughly establishing a new view of physics methodology.

9. Enlightenment

Previous views on "physics" have similarities and differences, but what is certain is that the concept of "physics" has been and is evolving. If physics has benefited mankind well both materially and spiritually, all kinds of brilliant achievements can't be achieved without the courage and exploration spirit of physicists. People today and tomorrow will further realize that physics is an effective way to acquire, organize, apply and explore knowledge, which is of great significance. This understanding should be the guiding principle for those who study physics and those who teach physics. Once the methodology of physics is really mastered by people, people who study physics are no longer satisfied with memorizing conceptual formulas to do a few problems. But pay more attention to the understanding of physical ideas and methods on a certain basis, which can be applied in many fields. Of course, physical methods can not be mastered by empty words, but can only be formed on the basis of good physical professional quality, which requires the majority of physics teachers to devote themselves to quality education. Good physical professional quality is mainly reflected in clear, comprehensive and accurate physical thinking, solid mathematical application ability and good experimental ability. In short, it has good theoretical and experimental quality and is good for students. On June 20, 2002, Mr. Ding Zhaozhong put it well in CCTV's "Son of the East" column: "If you do well in school, you must do theory; If you have strong hands-on ability, you should do experiments. This view is completely wrong. Many successful experimental physicists are proficient in theory. The most important thing in doing experiments is to find a topic, and ability and practice are secondary. "

On the other hand, the history of physics tells us that first-class theoretical physicists often have a solid experimental foundation. Newton did many famous experiments, and Einstein did experiments energetically in college, which was crucial to his great success in theory.

"Physics is a real science, a science that has stood the test of time, and a great and arduous science. Those short-lived theories, theories and physics are incomparable, and those small moves decorated with demagogic language in the wave of reform are not worth mentioning. The development of physics is endless like the evolution of the universe [1 1].

This statement is very emotional, but it makes sense.