Formula -Physics describes the "sentence" of nature

| Author: Chen Zheng 1, 陈 陈 | 2

(1 School of Physics and Engineering, Beijing Jiaotong University)

(2 Middle School Affiliated to Renmin University of China)

01

introduction

"Simple History of Time" is one of the best -selling physics science books in the 20th century. Many critics often mention such a sentence when they talk about their best -selling reasons: "There is no formula in this book." In the field of popular science creation, such a sentence also spreads: "A formula appears in the content of popular science, which will lose half of the audience; two formulas will lose more than two -thirds of the audience; and when the third formula appears, the audience will be the audience, the audience Basically run away. " The "formula" seems to be a gap, and it is stunned in front of many physics learners and enthusiasts, making physics look high and far away (Figure 1).

Figure 1 The "formula" in the eyes of beginners is like "Tianshu

The "formula" in the eyes of physicists is the most beautiful language. A formula is better than thousands of words, and it simply completes the complete and accurate description of nature [1]. Why are physicists and ordinary people feel so different about the "formula"? To a large extent, we encountered the situation of "going to the house" in the process of understanding and learning physics. "Formula" is a description method formed by generation physicists and mathematicians based on the purpose and characteristics of physics based on the purpose and characteristics of physics. In the course of basic physics, everyone often lacks the intermediate process and directly faces the final result. This is like a person climbed to the high place of the building along the ladder level, and then hidden the stairs passed by, so he gave it to Others form a highly unattainable feeling. If this step is displayed in front of everyone, everything is no longer mysterious. All everyone has to do is to work more along the ladder.

02

"Vocabulary" and "Sentence" of Physics

The "grammar" of natural language can usually be roughly divided into two parts: "word method" and "syntax". Semantic; the latter is to form a "sentence" in accordance with certain rules to form "sentences" to express their thoughts.

Although the language of physics looks very different from the surface of natural language, the basic logic is similar. In the process of describing nature, physics must first establish a quantitative indicator of various states and properties describing the research objects -physical quantity, and use simple letters, symbols, etc. as its code. This is not a kind of "sound, shape, meaning" Is the binding body of the "vocabulary" of physics language? Then connect the physical quantity with various arithmetic connections into equalization or inequality to describe phenomena or laws. Isn't this the "sentence" of physics?

The grammar of physics is simpler than natural language. In terms of "word method", there are neither "nouns", "verbs", "adjectives", "admits", "prepositions" and so on. The problem. Aiming at the various physical quantities constructed by complicated natural phenomena, in the process of connecting into the formula (like the "group sentence" process of natural language), the differences in the operation (operation) rules are divided into two types: there is no direction: no direction The "scalar" and the direction of "vector". If the concept of "tensor" is introduced, the scales and vectors are 0 -order and 1 order, respectively, and all the physical quantities are a type of tension. Of course, the physical quantity can also be divided into a wide range and intensity volume from the nature of the description object. From the perspective of the description state or the description process, it can be divided into status and process amount. And the export volume constructed by the basic quantity, but these classifications do not affect the operation (operation) rules of the corresponding physical quantities and the operator.

In terms of "syntax", physics does not pray for sentences, doubts, sighs, and so on. All "sentences" are statements. The symbols that represent the physical quantity are connected into equal formats or unwillingness through computing and mathematical computing rules to objectively describe the definition of object physical properties or their relationship between objects corresponding to the physical quantity. However, it should be noted that mathematical rules also play an important role in this process. For example, the vector algebra that often seen in basic physics formulas "•" (scalar accumulation) and "×" (vector accumulation) not only include the quantitative relationship between related physical quantities, but also whether there are directions and directions. Accurate information. According to the right hand accumulation of vector vector vector, Ampei DF = IDL × B, Lorenz force f = qv × b, etc. It is not necessary to remember "the left -hand generator is determined, the right -handed motor is determined" The rules of the judgment, the direction of each physical quantity and the sequence of the fork has given all the information.

03

Two different types of "formulas"

"Formula" is the "sentence" of physics describing nature. When we examine various "formulas" in basic physics, we will find that they actually have only two categories- "definition" and "laws", which are "narrative" two different contents.

The definition of the "formula" is to explain how to quantify some of the properties of the object, that is, the "definition" describing the corresponding physical physical quantity. The nature described by such "formulas" is usually not directly measured, and the physical quantity cannot be directly defined on the basis of measurement. Therefore, other physical quantities must be expressed by the combination by "formula". For example, the "speed" of the physical quantity of the rapid and slow exercise is an abstract concept, which cannot be directly measured in the real world. It is necessary to measure the changes in the position of the movement of the object and the time under this change. The change rate of changes is used as the physical quantity of quantitative description of the speed of exercise -speed (regular "formula" is to explain different physical properties in natural phenomena (these properties can belong to the same object or different objects) The relationship is the so -called "physical law". If Mr. Yang Zhenning uses the classic mechanics as an example to explain the layered structure of physical laws, it can also further divide the laws of physics into two levels: "phenomenon law" and "theoretical framework". "Elephant law" refers to these laws that only reflect the surface correlation between different physical quantities in the physical process, and does not reveal the mechanism behind it [2]. The correlation between positions, time, and track parameters does not tell us why planets exercise like this. This is a "phenomenon law".

Most of the laws involved in the physics courses of middle schools and ordinary physics of universities belong to the category of phenomena. For example, the law of ideal gas three gives only a certain quality of the ideal gase of the ideal gas parameter Press P, volume V, and temperature T.

F = -kx also only tells us that when the object has elastic deformation, the elastic force is proportional to the size and the variable variables. The proportional coefficient is related to the elastic properties of the object itself, but why is there such a relationship? What happened inside the object? Can't learn through the law. The law of classical friction (the law of Amenon -Kulun) F = μN also only reflects the friction on the interface and the positive pressure applied on the interface. The characteristics of the interface roughness, but when you understand the complex mechanism of the friction phenomenon, you will find that the friction coefficient μ does not contain information about the mechanism. Ohm's Law G, of course, the countdown to define the proportional coefficient is not essentially different as a characteristic parameter. We are more familiar with this physical quantity, that is, resistance R. The laws of Jiao Er, Curon's Law, Bio -Saavar's Law, Law Law, and Faraday Electromagnetic Law are all this.

The "theoretical framework" further reveals the causes and action mechanisms behind natural phenomena on the basis of the "law of phenomena". The formula describing the "theoretical framework" is relatively small throughout the physics, because the process of establishing the theoretical framework is also once again "thinking economy". , Perfectly reflect the "simplicity, completeness and accuracy" of physics. For example, the laws of gravitational law and Newton's movement established by Newton can solve most of the mechanical problems of macro -low -speed sports objects; Maxwell's equations unified electricity, magnetic, and light phenomena under the four concise formulas. Most of the rules of classic electromagnetics are summarized.

04

Conclusion

When we use the perspective of natural language to examine the common "formulas" in basic physics, and see the symbols that represent the physical quantities as "vocabulary", which is connected to the equal formula or inequality through the corresponding mathematical computing symbols and rules through the corresponding mathematical computing symbols and rules. The formula is regarded as "sentences". Each formula is nothing more than to explain how to quantitatively describes the property of the object, that is, define the physical quantity; or explain the accurate relationship relationship between different physical properties in the physical process, that is, describing physical laws. Try to describe this information with natural language and accurately, and then compare with the formula description method. At this time, you can feel the beauty of the formula in the eyes of physicists.

references

[1] Yang Zhenning. Physics Teaching, 2008, 30 (05): 10

[2] Wang Zinong. Modern physics knowledge, 2008, (03): 52

Reprinted content only represents the author's point of view

Does not represent the position of the Institute of Physics of the Chinese Academy of Sciences

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Source: China Physical Society Journal Network

Edit: Just_iu

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