Physics is a basic science which studies the fundamental laws of motion of matter. Different forms of motion have different laws of motion, and therefore have to be dealt with in different ways, based on which physics is divided into various parts such as mechanics, thermology, electromagnetism, optics and atomic physics. According to the historical development of physics can be divided into two parts: classical physics and modern physics. Modern physics is relative to classical physics, referring to the 20th century physics based on the theory of relativity and quantum theory. Since the laws studied in physics are very fundamental and universal, its basic concepts and fundamental laws are the basis for many fields of natural science and engineering technology. Because knowledge of physics constitutes a complete picture of the material world, it is also the foundation on which the worldview and methodology of science are built.
1, physics is the leading discipline of natural science
Physics as a rigorous, quantitative natural science of the leading disciplines, has been in the development of science and technology plays an extremely important role. It is closely linked to mathematics, astronomy, chemistry and biology, which interact with each other to promote the development of physics and other disciplines.
Physics and mathematics have a deep intrinsic connection. Physics is not satisfied with the qualitative description of the phenomenon, or simply record the facts in writing, in order to be as accurate as possible from the quantitative relationship to grasp the physical laws, mathematics has become an indispensable tool for physics, and the rich and colorful physical world for mathematical research has opened up a vast world. The relationship between physics and mathematics is close and has a long history. Many famous scientists in history, such as Newton, Euler, Gauss, etc., have made important contributions to these two sciences, and some great mathematicians in the late 19th and early 20th centuries, such as Pangale, Klein, Hilbert, etc., are well versed in theoretical physics in spite of their different academic tendencies. The study of chaos phenomenon in modern physics is also the result of the mutual combination of physics and mathematics.
The relationship between physics and astronomy is even more inextricably linked, and it can be traced back to the early studies of planetary motion by Kepler and Newton. The bands that now provide astronomical information have been extended from the visible light band to the broad band of electromagnetic waves, from radio waves to X-rays, and a variety of probes provided by modern physics have been employed. On the other hand, astronomy provides extreme conditions not found in laboratories on earth, such as high temperatures, high pressures, high-energy particles, strong gravitational forces, etc., and constitutes an ideal laboratory for testing theories of physics. Thus, almost all the evidence for general relativity comes from astronomical observations. Both positrons and muons were first observed in cosmic ray studies and contributed to the creation of particle physics. The theory of thermonuclear reactions was first proposed to explain the solar energy problem, the neutron star theory was confirmed by the discovery of pulsars, and the standard model of modern cosmology, the Big Bang theory, is based entirely on particle physics theory.
Physics and chemistry are inherently interdependent and closely related. Chemistry in the atomic theory, the development of molecular theory for the establishment of physics in the kinetic theory of gas laid the foundation for the thermal, mechanical, electrical properties of matter to make a satisfactory explanation; and physics in the development of quantum theory, the establishment of the structure of the electron shell layer of the atom and from the essence of the nature of the various elements of the law of periodic changes. The birth of quantum mechanics and the subsequent development of solid state physics, so that the object of physics and chemical research increasingly in-depth to the more complex structure of the level of matter, semiconductors, superconductors research, more and more need to cooperate with and assist chemists, in liquid crystal science, polymer science and molecular membrane science to make progress in the chemists, physicists * * * with the results of the efforts. On the other hand, the theory of modern physics and experimental techniques and promote the development of chemistry.
The contribution of physics in the development of biology is reflected in two aspects: one is for the life sciences to provide modern experimental means, such as electron microscopy, X-ray diffraction, nuclear magnetic **** vibration, scanning tunneling microscope, etc.; the second is for the life sciences to provide theoretical concepts and methods. Since the 19th century, biologists have carried out a great deal of research work in biological heredity and put forward the genetic hypothesis. The question of the material basis of genes, however, remained a question mark. In the 1940s, the physicist Schr?dinger, interested in the fundamental questions of life, proposed the idea that the genetic code is stored in non-periodic crystals, which became widely known due to the fact that in his pamphlet "What is Life? In the 1940s, the Cavendish Laboratory at the University of Cambridge, England, carried out an X-ray structural analysis of myoglobin, and after a long period of effort finally determined the crystal structure of DNA (deoxyribonucleic acid), revealing the nature of the genetic code, which was the most significant breakthrough in the biological sciences of the 20th century. Molecular biology has constituted a frontier field in the life sciences, and biophysics is clearly promising as well.
2, physics is the modern technological revolution of the precursor
Generally speaking, the relationship between physics and technology, there are two basic modes: one is due to the needs of production practice and the creation of technology, such as the 18th century to the 19th century steam engine and other heat engine technology, and then improve to the theory, the establishment of thermodynamics, and then feedback to the technology, to promote the further development of technology; the other is the first in the laboratory to reveal the essence of genetic code, which is the most significant breakthroughs in the 20th century biophysics. is to first reveal the basic laws and establish a more complete theory in the laboratory, and then develop it into a completely new technology in production. the development of electromagnetism in the 19th century provides an example of the second model. Based on Faraday's discovery of electromagnetic induction and Maxwell's establishment of a system of equations for the electromagnetic field, today's generators, electric motors, telegraphs, televisions, and radars were produced, creating modern power engineering and radio technology. As Chinese-American physicist Li Zhengdao said, "Without yesterday's basic science there would be no technological revolution today."
The importance of the second model is even more pronounced in today's world, where physics has become the precursor and foundational discipline for the development of modern high technology. In turn, the development of high technology places new demands on physics, while also providing advanced research conditions and tools. The so-called high technology refers to those contemporary cutting-edge technologies that play a great role in promoting social and economic development. The following is a brief introduction to the prominent role played by basic research in physics in the current high-technology, namely nuclear energy technology, superconducting technology, information technology, laser technology, and electronics technology.
The acquisition and utilization of energy is the top priority of industrial production, and one of the major contributions of physics in the 20th century lies in the utilization of nuclear energy, which can be said to be a brand-new technology grown out of basic research. 1905 Einstein's mass-energy relation was put forward, which established the theoretical basis for the utilization of nuclear energy. In 1932, physicists discovered neutrons, and in 1939, they found that energy could be released during the fission of uranium nucleus caused by neutrons, and more neutrons were emitted at the same time, so they put forward the concept of obtaining atomic energy by utilizing the "chain reaction"; in the 1940s, according to the principle of releasing energy from the fission of heavy nuclei, atomic reactors were set up, which made the utilization of fission energy become a reality. In the 1950s, controlled fusion reactors were designed based on the principle of energy release during fusion of light nuclei. Fusion energy is not only abundant, but also safe and clean. Research on controlled thermonuclear fusion energy will open the way to solving the energy problems of the 21st century.
In terms of energy and power, the widespread use of superconductors, which can transmit current without loss, could also lead to a revolution. 1911 Dutch physicist Onners found that the resistance of pure mercury samples suddenly disappeared near 4.2K, and then found that some other metals also had such a phenomenon, which opened a new field of superconducting physics. In 1957, the BCS theory further revealed the microscopic mechanism of superconductivity, and in 1962, the discovery of the Josephson effect extended the application of superconductivity to the field of quantum electronics. Coils wound by conventional superconductors operating in the temperature region of liquid helium (1K to 5.2K) have been used in gas pedals, magnetohydrodynamic power generators, and large-scale experimental equipment to generate strong magnetic fields, which can save large amounts of electricity; and the application of superconductors to power generators and motors has resulted in experimental prototypes approaching a practical scale. As a result of these successful applications, coupled with superconducting energy storage, superconducting power transmission and levitation trains and other applications, it can be seen that high-temperature superconductors have a broad application prospects. Since the discovery of high-temperature superconductors in the temperature region of liquid nitrogen (63K to 80K) by Chinese-American physicist Zhu Jingwu and Zhao Zhongxian of the Chinese Academy of Sciences in 1987, the practicalization of superconducting materials has made great progress, and the prospect of its application in high-current technology is the most exciting.
Information technology is becoming increasingly important in modern industry, computing technology, communication technology and control technology has fundamentally changed the face of contemporary society. If the first industrial revolution is the revolution of power or energy, the second industrial revolution is the revolution of information or negative entropy. As mankind moves towards the information age, faced with the increasingly value-added information of complicated content, huge quantity and diverse forms, the technology of information processing, storage and transmission is urgently required to shift from the original behavior of relying on "electricity" to the behavior of "light", thus promoting the development of "photonics" and "photonics". "Photonics" and "photonics" rise. The most outstanding achievements of photonics are in optical communication, optical holography, and optical computing. Optical communication was proposed in the 1960s and developed rapidly in the 1970s, which is characterized by large capacity, strong anti-interference, high confidentiality and long transmission distance. Optical communication uses laser as the light source and optical fiber as the transmission medium, which is 1 billion times larger than the capacity of electric communication. A hair-thin optical fiber can transmit tens of thousands of telephone calls and thousands of television channels, and a fiber-optic cable composed of 20 optical fibers can talk up to 76,000 times a day. Optical communication opens up a new way of communication that is highly efficient, inexpensive and lightweight. The information storage technology represented by optical disk has the advantages of large storage capacity, long time, easy operation, good confidentiality and low cost, and the storage capacity of optical disk is 1,000 times of the general magnetic storage capacity. A new generation of optical computer research and development has become another hot spot of international high-tech competition. 21st century, mankind will enter the information age from the industrial age.
Laser is a new science and technology emerged in the early 1960s. 1917 Einstein put forward the concept of stimulated radiation, pointed out that the photons produced by stimulated radiation have the same frequency, phase, polarization state and direction of propagation of the characteristics of the same, and stimulated radiation of the light to obtain the amplification of light. He also pointed out that the main condition for the realization of light amplification is to make the number of atoms in the high-energy state larger than the number of atoms in the low-energy state, forming the inverse distribution of the number of particles, thus laying the theoretical foundation for the birth of the laser. 50's in the electrical engineers and physicists to study the problem of radio microwave bands when the generation of quantum electronics. 1958 Towns and others put forward to the quantum amplification technology for millimeter-wave, infrared, as well as the possibility of the visible light band, thus establishing the concept of the laser. The concept of laser was established in 1960, when the world's first laser was developed by Meyman in the United States. After 30 years of efforts, laser devices have been developed to a fairly high level: the laser output wavelength almost covers from X-ray to millimeter wavelengths, the pulse output power reaches 1019W/cm2, and the shortest optical pulse reaches 6×10-15s, etc. The laser has successfully penetrated into modern science and technology. Laser successfully penetrated into various fields of modern science and technology. The use of laser high brightness, good monochromaticity, good directionality, good coherence, in materials processing, precision measurement, communications, medical, holographic photography, product testing, isotope separation, laser weapons, controlled thermonuclear fusion and so on have gained a wide range of applications.
Electronic technology is based on the development of electronics. 1906, the first three-pole electron tube appeared, is the beginning of electronic technology. 1948 physicists invented the semiconductor transistor, which is a physicist to recognize and master the semiconductor in the law of electronic motion and successfully use the results of the invention of a new era of electronic technology. the end of the 50's invented the Integrated circuits were invented in the late 50's and then developed in the direction of miniaturization. 1967 saw the creation of large-scale integrated circuits and 1977 saw the birth of ultra-large-scale integrated circuits. In the 30 years from 1950 to 1980, the graphic size (line width) of transistors was reduced by a factor of 1,000, thanks to the deepening of physical knowledge and advances in process technology. Today's ultra-large-scale integrated circuit chips can be prepared with about 40 transistors in a hair-thin cross-sectional area. The rapid development of microelectronics technology makes the information processing capacity and the capacity of electronic computers continue to grow. 40 years built the first large-scale electronic computer, weighing up to 30t, power consumption of 200kW, covers an area of 150m2, computing speed of a few thousand times per second, and in today's a laptop computer performance can be more than it. In the face of the fact that the size of the graphics in ultra-large-scale circuits is constantly shrinking, people have seen that the semiconductor devices based on microelectronics technology has approached its physical and technical limits. Physicists are required from the study of microstructure physics, to create new devices that can meet the requirements of higher information processing capacity, so that microelectronics technology is further developed.
3, physics is the foundation of the scientific worldview and methodology
Physics depicts a complete picture of the material world, which reveals the interconnectedness and mutual transformation of various forms of motion, fully embodies the materiality of the world and the unity of the material world, the law of conservation of energy discovered in the middle of the nineteenth century, known as the great fundamental law of motion by Engels, which was one of the three major discoveries of natural science in the 19th century and one of the most important discoveries of the natural sciences in the nineteenth century. The law of conservation of energy, discovered in the middle of the 19th century, was called the great fundamental law of motion by Engels, and it is one of the three major discoveries of natural science in the 19th century, as well as the natural scientific foundation of material dialectics. The famous physicists Faraday and Einstein had a strong belief in the unity of the forces of nature, and they worked consistently throughout their lives to confirm the universal connection between various phenomena.
The history of physics tells us that the establishment of new physical concepts and physical concepts is a leap in the history of human understanding, and only by breaking through the old traditional concepts of the boundaries can be introduced. For example, Planck's energy hypothesis, because of the breakthrough of the traditional concept of "continuous change of energy", and was opposed by the physics community at the time. Planck himself was bound by traditional concepts, and for many years after he put forward the hypothesis of energon, he was anxious for a long time, and always wanted to go back to the position of classical physics. Similarly, the special theory of relativity was established by Einstein on the basis of his breaking through the bondage of Newton's absolute view of space-time and forming the relativistic view of space-time. As for Lorentz, because he was bound by the absolute view of space-time, he proposed the correct coordinate transformation formula, but did not recognize the time in the transformation formula as the real time, and has not been able to propose the special relativity theory. This shows that the establishment of a correct view of science and worldview plays an important role in the development of science.
Physics is a science in which theory and experiment are closely integrated. Physics in many major discoveries, important principles of the proposed and the development of the dialectical relationship between experiment and theory: experiment is the basis of theory, the theory of the correctness of the experiments to accept the test, and the theory of the experiments have an important role in guiding the combination of the two to promote the forward development of physics. Physicists in general epistemologically adhere to the scientific theory is the description of the objective reality, the famous theoretical physicist Schr?dinger claimed that physics is "the carrier of absolute objective truth".
In summary, through the physics teaching to cultivate students' correct worldview is the characteristics of the physics discipline itself, is a kind of advantage of physics teaching. To give full play to this advantage, improve self-awareness, the cultivation of worldview into the teaching.
The formation process of a scientific theory cannot be separated from the guidance of scientific thinking and the application of scientific method. Correct scientific thinking and scientific method is in the human cognitive pathway to realize the bridge from phenomenon to essence, from contingency to necessity, from the unknown to the known. Scientific method is the key for students to open the door of the discipline in the learning process, in the future to engage in scientific and technological work for scientific and technological innovation of the sharp weapon, the teacher in the transfer of knowledge to the students to enlighten and guide the students to master the methodology of the course, which is necessary to cultivate creative talents.
The methodology of this course includes the following three aspects.
Logical thinking is an important form of scientific abstraction, it is the natural sciences in the long-term development of the formation of a more rigorous logical reasoning. There are two methods of thinking usually used in physics: analysis-synthesis method, induction-deduction method. In thermodynamics often use the inverse method.
(1) analysis - synthesis method analysis is the whole is broken down into parts; synthesis is the object of the combination of parts, it is the opposite of the analysis of a thinking process. For example, the projectile motion can be decomposed into the vertical direction of uniform acceleration and horizontal direction of uniform motion, the synthesis of the two is the projectile motion. The meta-process method in physics is a special method of analysis, such as Newton attributes the attraction between all objects to the gravitational force between particles, Ampere attributes the force between electric currents to the force between current elements and so on.
(2) induction - deduction method induction method is from individual to general knowledge method, deduction method is the opposite, it is from the general to individual knowledge method, that is, from the known general principles to examine a particular object, so as to deduce the conclusions about the object of the method. Induction and deduction are two independent and interdependent methods of thinking in the process of scientific understanding, are indispensable in the process of scientific understanding.
Induction plays an important role in the process of scientific discovery and theory building. For physicists, the really exciting factor comes from the process of induction. For example, Newton discovered the law of gravity by exploring the laws of force in nature through his study of motion. Ampere established the law of meta-interaction of electric currents through experiments observing interactions between electric currents. The discovery of Neptune is an outstanding example of the use of deduction to make clear predictions from the known laws of force, which in turn played a huge role in supporting the theory of gravity.
2. Basic Methods Linked to the Fundamental Principles of Physics
Through the study of this book, we can master the basic methods derived from the concept of principles. For example, the energy approach derived from the principle of conservation of energy, precisely because we insist that the law of conservation of energy should hold in any physical process, and can even predict a new form of energy. A striking example of this is Pauli's prediction of the existence of neutrinos in order to insist on the conservation of energy when analyzing the energy spectrum of beta rays. In molecular kinematics there is the statistical averaging method derived from the statistical averaging principle, in electromagnetism there is the symmetry analysis method derived from Gauss's theorem and Ampere's loop law, and the analysis method derived from the principle of superposition, and in mechanics there is the analysis method of the force of isolation derived from Newton's law, and so on.
3. Creative thinking in scientific discovery
In the actual scientific discovery, there is no strict logical channel, the creation of science is often due to the scientists unique creative thinking results. In the past, most of the teaching is to teach only the results of previous research, but for the predecessor of how to get these results of the ideas and research methods are rarely mentioned. This is like only giving students the gold of "turning stones into gold" without making them practice this "finger". The importance of learning the methods of scientific inquiry is, as the French physicist Laplace said, "To know the methods of a giant is no less useful to the progress of science than the discovery itself, and the methods of scientific research are usually the most interesting part. " The methods commonly used in scientific research are listed below.
(1) Physical Models A physical model is a highly abstract ideal object reflecting the essential characteristics of a thing that is built to facilitate research. People use physical models to facilitate computational reasoning, to explore the laws of motion, and to establish physical equations. In the construction of physical models, the complexity of things to be abstracted and simplified, highlighting the main features of the object of study. For example, Newton in the discovery of the law of gravity in the process, the use of abstraction and simplification of the establishment of an ideal model of the method: from circular motion to elliptical motion, from the mass to the sphere, from the single-body problem to the two-body problem. He compared the ideal model with the real thing, then corrected it appropriately, and finally made the physical model basically conform to the physical world.
There are many instances in physics where physical equations are established through physical models, such as the ideal gas model proposed by Clausius, which deduced the formula for gas pressure; the proposal of the molecular model of van der Waals, which led to the establishment of the real gas equation; the ideal heat engine model and the ideal cyclic process proposed by Karnow, which led to the establishment of Karnow's Theorem; the molecular current model proposed by Ampère, which explained the nature of the material magnetism; and Maxwell's use of molecular vortexes, which explained the nature of the material magnetism. explanation; Maxwell used the mechanical model of molecular vortex, derived the magnetic force formula, magnetic energy formula, explaining the phenomenon of electromagnetic induction. Physics also has a point, rigid body, pendulum, point charge, absolute black body and various atomic models are physical models. Analyzing the basis and ideas of previous generations who built models in the course of their research helps to improve understanding of scientific ideas.
(2) Ideal Experimentation Ideal experimentation is a process of intellectual reasoning that unfolds according to a model of an experiment, a method and form of logical reasoning. It avoids many difficulties in real experiments, and provides an easy way to expose the flaws of old theories and explore new ones. For example, Galileo to illustrate the principle of inertia proposed by the ball along the smooth slope down and up the theory of experiments, Newton in order to reveal the unity of celestial motion and the movement on the ground and the conception of the top of the mountain for the parabolic motion of the ideal experiment and so on. In the history of the development of physics, in the process of generating some major concepts, or the important moment of the alternation of old and new theories, the ideal experiment plays an important role. For example, Einstein for the description of simultaneous relativity "train", for the description of equal acceleration force field and gravitational field equivalence, inertial mass and gravitational mass equivalence of the "elevator", as well as for the description of the laws of thermodynamics is a statistical law of the "Maxwell's Demon" and so on. These ideal experiments are image, vivid, concrete, so that people are more receptive to new physical ideas, easier to understand new physical concepts.
(3) Physical Analogies The method of physical analogies is to utilize the partial similarity between one law of science and another law of science, and use one of them to illustrate the other. Analogies are based on the fact that the two types of laws are similar in mathematical form. Analogies can bridge research methods in different fields, can provide a medium between analytic abstract forms and hypotheses, and can inspire new physical ideas that help to recognize and develop physical processes and laws that have yet to be investigated. For example, Maxwell found a mathematical description of Faraday's lines of force by analogizing the lines of force with the flow lines of an incompressible fluid; De Broglie introduced the concept of wave-particle duality through an analogy between mechanics and optics, and put forward the hypothesis of "matter waves"; Schr?dinger created wave dynamics through an analogy between mechanics and optics; and Priestley created wave dynamics through an analogy between electricity and gravity. Electricity and gravity analogy, according to the metal container on the inner surface of the surface without any electric charge, in the interior of the electric force and has long been made in a uniform spherical shell of zero gravity argument, as early as Coulomb's law was proposed 18 years ago, put forward a witty conjecture: the attraction of electricity to follow the same law of gravity, that is, with the square of the distance is inversely proportional to the square of the force.
(4) Physical Hypotheses A hypothesis is a hypothetical view and description of a problem under study based on certain scientific facts and scientific theories. Hypothesis has a very important role in the process of scientific development. Engels in the Dialectics of Nature clearly pointed out that "as long as natural science is thinking, its form of development is hypothesis." Hypothesis is both the main method of scientific research and a necessary part of the development of scientific understanding. For example, Maxwell, in order to explain the phenomenon of induced electric current generated on the conductor loop in the changing magnetic field, put forward the hypothesis of induced electric field; in order to solve the difficulties encountered in the Ampere's law of loops in the conduction current discontinuity, put forward the hypothesis of displacement current. These two hypotheses play an extremely important role in the establishment of electromagnetic field theory. Another example is a series of major discoveries in physics at the beginning of the 20th century: X-rays, radioactivity, the discovery of electrons, and so on, and the doctrine of the indivisibility of the atom in conflict, and then produced a variety of hypotheses on the structure of the atom. Another example is Planck in order to explain his derivation of the radiation formula with the experimental results fully consistent with the quantization of energy hypothesis. Another example is the light quantum hypothesis proposed by Einstein to explain the photoelectric effect experiment. De Broglie put forward the hypothesis of material waves from the dual properties of waves and particles exhibited by X-rays, inspired by the idea of wave-particle duality of light.
Physics research methods and feints, such as Einstein's paradox of chasing light, Galileo's falling body feints, as well as scientific imagination, trial and error speculation and scientific intuition and other creative methods of thinking, which play an important role in the establishment of physical principles.