Freiman popular lectures on physics. "The Great Laws of Conservation"

Chapter 1

ATOMS IN MOTION

§ 1. Introduction

§ 3. Atomic processes

§ 1. Introduction

This two-year physics course is designed for you, the reader, to become a physicist. Granted, this is not so necessary, but what teacher does not hope for it! If you really want to be a physicist, you will have to work hard. After all, two hundred years of rapid development of the most powerful field of knowledge mean something! Such an abundance of material, perhaps, cannot be mastered in four years; After this, you still need to take special courses.

And yet, the entire result of the colossal work done over these centuries can be condensed - reduced into a small number of laws that summarize all our knowledge. However, these laws are also not easy to master, and it would simply be dishonest for you to begin studying such a difficult subject without having at hand some diagram, some outline of the relationship of some parts of science with others. The first three chapters constitute such an essay. In these chapters we will get acquainted with how physics is connected with other sciences, how these other sciences relate to each other, and what science itself is. This will help us “feel” the subject of physics.

You may ask: why not immediately, on the first page, give the basic laws, and then only show how they work in different conditions? After all, this is exactly what they do in geometry: they formulate axioms, and then all that remains is to draw conclusions. (It’s not a bad idea: to explain in 4 minutes what you couldn’t explain in 4 years.) This is impossible to do for two reasons. Firstly, we do not know all the basic laws; on the contrary, the more we learn, the more the boundaries of what we need to know expand! Secondly, the exact formulation of the laws of physics is associated with many unusual ideas and concepts that require equally unusual mathematics for their description. It takes a lot of practice just to get the hang of understanding the meaning of words. So your proposal will not pass. We will have to move gradually, step by step.

Each step in the study of nature is always only an approach to the truth, or rather, to what we consider to be the truth. All that we learn is some kind of approximation, because we know that we do not yet know all the laws. Everything is studied only to become incomprehensible again or, in best case scenario, demand correction.

The principle of science, almost its definition, is this: the touchstone of all our knowledge is experience. Experience, experiment is the only judge of scientific “truth”. What is the source of knowledge? Where do the laws we test come from? Yes, from the same experience; it helps us derive laws; it contains hints of them. And on top of that, we also need imagination in order to see something big and important behind the hints, in order to guess the unexpected, simple and beautiful picture that arises behind them, and then carry out an experiment that would convince us of the correctness of the guess. This process of imagination is so difficult that a division of labor occurs: there are theoretical physicists, they imagine, figure out and guess new laws, but do not carry out experiments, and there are experimental physicists, whose job is to carry out experiments, imagine, figure out and guess.

We have said that the laws of nature are approximations; first they discover “wrong” laws, and then they discover “correct” ones. But how can an experience be “wrong”? Well, firstly, for the simplest reason: when something is wrong in your devices, and you don’t notice it. But such an error is easy to catch, you just need to check and check everything. Well, if you don’t nitpick about the little things, can the results of the experiment still be erroneous? They can, due to a lack of precision. For example, the mass of an object appears to be constant; A spinning top weighs the same as one lying still. Here is the “law” for you: mass is constant and does not depend on speed. But this “law,” as it turns out, is incorrect. It turned out that mass increases with increasing speed, but only for noticeable growth speeds close to light are needed. The correct law is this: if the speed of an object is less than 100 km/sec, the mass is constant to within one millionth. This law is approximately correct in this approximate form. One might think that there is practically no significant difference between the old law and the new one. Yes and no. For ordinary speeds, you can forget about the reservations and, to a good approximation, consider the statement that the mass is constant to be a law. But at high speeds we will begin to make mistakes, and the higher the speed, the more so.

But the most remarkable thing is that with common point From a perspective, any approximate law is absolutely erroneous. Our view of the world will require revision even when the mass changes even a little. This - characteristic property the general picture of the world that stands behind the laws. Even a minor effect sometimes requires a profound change in our views.

So what should we study first? Should we teach the right ones, but unusual laws with their strange and difficult concepts, such as the theory of relativity, four-dimensional space-time, etc.? Or should we start with the simple law of “constant mass”? Although he is close, he does without difficult ideas. The first is undoubtedly more pleasant and attractive; the first is very tempting, but it’s easier to start with the second, and then this is the first step towards a deeper understanding the right idea. This question comes up all the time when teaching physics. On different stages We will tackle it differently throughout the course, but at each stage we will try to lay out what is known now and with what accuracy, how it fits in with the rest, and what might change as we learn more about it.

Let's move on to our outline, to an outline of our understanding of modern science (primarily physics, but also other related sciences), so that when we later have to delve into various issues, we can see what lies at the basis of them, why they are interesting and how they fit into the overall structure.

So, what does the picture of the world look like?

§ 2. Matter consists of atoms

If, as a result of some global catastrophe, all accumulated scientific knowledge were destroyed and only one phrase were passed down to future generations of living beings, then which statement, composed of the fewest words, would bring the most information? I believe that this is the atomic hypothesis (you can call it not a hypothesis, but a fact, but this does not change anything): all bodies consist of atoms - small bodies that are in continuous motion, attract at a short distance, but repel if one press one of them more tightly to the other. This one phrase, as you will see, contains an incredible amount of information about the world, you just need to apply a little imagination and a little thought to it.

To show the power of the idea of an atom, let's imagine a drop of water 0.5 cm in size. If we look closely at it, we will see nothing but water, calm, continuous water. Even under the best optical microscope at 2000x magnification, when the drop takes size large room, and even then we will still see relatively calm water, unless some “soccer balls” begin to dart across it. This paramecia is a very interesting thing. At this point, you can linger and take care of the paramecia, its cilia, watch how it contracts and unclenches, and give up on further enlargement (unless you want to examine it from the inside). Biology deals with paramecia, and we will walk past them and, in order to see the water even better, we will magnify it again by 2000 times. Now the drop will grow to 20 km, and we will see something teeming in it; now it is no longer so calm and solid, now it resembles a crowd in a stadium on the day of a football match from a bird's eye view. What is this teeming with? To get a better look, let's magnify it another 250 times. Our eyes will see something similar to Fig. 1.1.

Fig. 1.1. A drop of water (magnified a billion times).

This is a drop of water, magnified a billion times, but, of course, this picture is relative. First of all, the particles are depicted here in a simplified manner, with sharp edges - this is the first inaccuracy. For simplicity, they are located on a plane, but in fact they wander in all three dimensions - this is the second thing. The figure shows “blots” (or circles) of two types - black (oxygen) and white (hydrogen); It can be seen that two hydrogens are attached to each oxygen. (Such a group of an oxygen atom and two hydrogen atoms is called a molecule.) Finally, the third simplification is that real particles in nature constantly shake and bounce, twisting and turning around one another. You should imagine in the picture not rest, but movement. The figure also cannot show how particles “stick to each other,” attract, stick one to another, etc. We can say that entire groups of them are “glued together” by something. However, neither body is able to squeeze through the other. If you try to force one against the other, they will push away.

The radius of an atom is approximately 1 or 2 per 10 -8 cm. The value 10 -8 cm is an angstrom, so the radius of an atom is 1 or 2 angstrom (A). Here's another way...

To the readers of the Russian edition

These are lectures on general physics given by a theoretical physicist. They are not at all similar to any known course. This may seem strange: the basic principles of classical physics, and not only classical, but also quantum, have long been established, the course of general physics is taught all over the world in thousands educational institutions for many years now and it’s time for it to become a standard sequence known facts and theories, like, for example, elementary geometry in school. However, even mathematicians believe that their science should be taught differently. And there is nothing to say about physics: it is developing so intensively that even the best teachers constantly face great difficulties when they need to tell students about modern science. They complain that they have to break what are called old or habitual ideas. But where do habitual ideas come from? Usually they get into young heads at school from the same teachers, who will then talk about the inaccessibility of the ideas of modern science. Therefore, before getting to the heart of the matter, a lot of time has to be spent convincing listeners of the falsity of what was previously instilled in them as an obvious and immutable truth. It would be crazy to first tell schoolchildren “for simplicity” that the Earth is flat, and then, as a discovery, report that it is spherical. Is the path along which future specialists enter the profession so far from this absurd example? modern world ideas of the theory of relativity and quantum? The matter is also complicated by the fact that for the most part the lecturer and listeners are people different generations, and it is very difficult for a lecturer to escape the temptation to lead listeners along that familiar and reliable path along which he himself at one time reached the desired heights. However, the old road does not remain the best forever. Physics is developing very quickly, and in order to keep up with it, we need to change the way we study it. Everyone agrees that physics is one of the most interesting sciences. At the same time, many physics textbooks cannot be called interesting. Such textbooks outline everything that follows the program. They usually explain what benefits physics brings and how important it is to study it, but from them it is very rarely possible to understand why studying physics is interesting. But this side of the issue also deserves attention. How can you make a boring object both interesting and modern? First of all, those physicists who themselves work with passion and know how to convey this passion to others should think about this. The time for experimentation has already arrived. Their goal is to find the most effective ways teaching physics, which would make it possible to quickly transfer to a new generation the entire stock of knowledge that has been accumulated by science throughout its history. The search for new ways in teaching has also always been important part Sciences. Teaching, following the development of science, must continuously change its forms, break traditions, and look for new methods. An important role here is played by the fact that in science an amazing process of a kind of simplification is constantly taking place, which makes it possible to simply and briefly present what once required many years of work.

An extremely interesting attempt in this direction was made at the California Institute of Technology (USA), which is abbreviated as CALTECH, where a group of professors and teachers, after numerous discussions, developed a new program in general physics, and one of the participants in this group, the prominent American physicist Richard Feynman, read lectures.

Feynman's lectures are distinguished by the fact that they are addressed to a listener living in the second half of the 20th century, who already knows or has heard a lot. Therefore, lectures do not waste time on explaining in “scientific language” what is already known. But they fascinatingly tell how a person studies the nature around him, about the boundaries reached today in the knowledge of the world, about what problems science solves today and will solve tomorrow.

Lectures were given in 1961–1962 and 1962–1963 academic years; they were recorded on tape, and then (and this turned out to be a difficult task in itself) “translated” into “written English” by Professors M. Sands and R. Leighton. This unique “translation” preserves many of the features of the lecturer’s live speech, its liveliness, jokes, and digressions. However, this very valuable quality of the lectures was by no means the main and self-sufficient one. No less important were the original methods presentation of the material, which reflected the bright scientific personality of the author, his point of view on the way of teaching students physics. This, of course, is not accidental. It is known that in their scientific works Feynman always found new methods that quickly became generally accepted. Feynman's work on quantum electrodynamics and statistics brought him wide recognition, and his method - the so-called "Feynman diagrams" - is now used in almost all areas of theoretical physics.

Whatever they say about these lectures - whether they admire the style of presentation or lament the breaking of good old traditions - one thing remains indisputable: it is necessary to begin pedagogical experiments. Probably, not everyone will agree with the author’s manner of presenting certain issues, and not everyone will agree with the assessment of the goals and prospects of modern physics. But this will stimulate the appearance of new books in which other views will be reflected. This is an experiment.

But the question is not only what to tell. Another question that is no less important is in what order this should be done. The location of sections within a general physics course and the sequence of presentation is always a conditional question. All parts of science are so connected with each other that it is often difficult to decide what should be presented first and what next.

However, in most university programs and available textbooks, certain traditions are still preserved.

Refusal from the usual sequence of presentation is one of the distinctive features Feynman lectures. They tell not only about specific tasks, but also about the place that physics occupies in a number of other sciences, about ways to describe and study natural phenomena. Probably, representatives of other sciences - say, mathematics - will not agree with the place that Feynman assigns to these sciences. For him, as a physicist, “his” science, of course, looks the most important. But this circumstance does not take up much space in his presentation. But his story clearly reflects the reasons that motivate a physicist to carry out the hard work of a researcher, as well as the doubts that arise when he is faced with difficulties that now seem insurmountable.

A young natural scientist must not only understand why it is interesting to do science, but also feel at what cost victories are won and how sometimes difficult the roads leading to them are.

“Physics is like sex: it may not give practical results, but this is not a reason not to do it”- the slogan with which Richard Feynman went through life, captivating thousands of people with his unbridled passion. A brilliant scientist, an inquisitive microbiologist, a thoughtful expert on Mayan writing, an artist, a musician, and a part-time safecracker, Feynman left behind an extensive scientific legacy in the field of theoretical physics and a considerable number of speeches in which the professor tried to convey to us his admiration for the genius and simplicity of nature , many laws that we still cannot comprehend.

In this sense, Feynman's Messenger lectures on the topic "The Nature of Physical Laws", read by him in 1964 at Cornell University, is a universal mini-textbook on physics, which briefly, sharply, accessiblely and emotionally presents the achievements of this science and the problems facing researchers. Yes, 50 years have passed, a lot has changed (string theory was put forward, the Higgs boson was discovered, the existence of dark energy, the expansion of the Universe), but those foundations, those physical laws that Feynman talks about are universal key, with which you can confidently approach acquaintance with the latest discoveries of scientists in this field. However, you can do without this pragmatic pathos: Feynman’s lectures are amazing, and will appeal to everyone who stands numb before the greatness of Nature and the harmony that permeates everything in our world, from the structure of the cell to the structure of the Universe. After all, as Feynman himself said, . So let's enjoy it.

Lecture No. 1

"The Law of Universal Gravity"

In this lecture, Richard Feynman introduces viewers to the law of universal gravitation as an example of a physical law, talks about the history of its discovery, characteristic features, distinguishing it from other laws, and about the extraordinary consequences that the discovery of gravity entailed. Another scientist here reflects on inertia and how amazingly everything works:

This law was called "the greatest generalization achieved by the human mind." But already from the introductory words you probably realized that I am interested not so much in the human mind as in the wonders of nature, which can obey such elegant and simple laws as the law of universal gravitation. Therefore, we will not talk about how smart we are in discovering this law, but about how wise nature is in observing it.

Lecture No. 2

"The connection between physics and mathematics"

Mathematics is the language spoken by nature, according to Richard Feynman. All the arguments in favor of this conclusion are in the video.

No amount of intellectual argument can convey to a deaf person the feeling of music. In the same way, no intellectual arguments can convey an understanding of nature to man. "another culture" Philosophers try to talk about nature without mathematics. I'm trying to describe nature mathematically. But if they don’t understand me, it’s not because it’s impossible. Perhaps my failure is explained by the fact that the horizons of these people are too limited and they consider man to be the center of the Universe.

Lecture No. 3

"The Great Laws of Conservation"

Here Richard Feynman begins to talk about general principles, which permeate the entire variety of physical laws, paying attention to Special attention the principle of the law of conservation of energy: the history of its discovery, application in different areas and the mysteries that energy poses for scientists.

Searching for the laws of physics is like a child’s game of playing with cubes, from which you need to assemble a whole picture. We have a huge variety of cubes, and every day there are more and more of them. Many lie on the sidelines and do not seem to fit in with the others. How do we know they are all from the same set? How do we know that together they should form a complete picture? There is no complete certainty, and this worries us somewhat. But the fact that many cubes have something in common gives us hope. All have blue skies painted on them, all are made from the same type of wood. All physical laws are subject to the same conservation laws.

Video source: Evgeny Kruychkov / Youtube

Lecture No. 4

"Symmetry in physical laws"

Lecture on the features of symmetry of physical laws, its properties and contradictions.

Since I'm talking about the laws of symmetry, I would like to tell you that several new problems have arisen in connection with them. For example, each elementary particle there is a corresponding antiparticle: for an electron it is a positron, for a proton it is an antiproton. In principle, we could create so-called antimatter, in which each atom would be made up of corresponding antiparticles. Thus, an ordinary hydrogen atom consists of one proton and one electron. If we take one antiproton, electric charge which is negative, and one positron and combine them, then we get a special type of hydrogen atom, so to speak, an antihydrogen atom. Moreover, it was found that, in principle, such an atom would be no worse than an ordinary one and that in this way it would be possible to create antimatter itself different types. Now it is permissible to ask, will such antimatter behave exactly the same as our matter? And, as far as we know, the answer to this question should be yes. One of the laws of symmetry is that if we make an installation from antimatter, it will behave exactly the same as an installation from our ordinary matter. True, as soon as these installations are brought together in one place, annihilation will occur and only sparks will fly.

Lecture No. 5

"The difference between past and future"

One of Feynman's most interesting lectures, which, ironically, remains the only one untranslated. There is no need to be discouraged - for those who do not try to understand the intricacies of scientific English, you can read the chapter of the same name from the scientist’s book, for everyone else - we are posting an English version of the physicist’s speech.

We remember the past, but we don't remember the future. Our awareness of what might happen is of a very different kind than our awareness of what has probably already happened. The past and present are perceived psychologically in completely different ways: for the past we have such a real concept as memory, and for the future we have the concept of apparent free will. We are sure that we can somehow influence the future, but none of us, with the possible exception of singletons, thinks that we can change the past. Repentance, regret and hope are all words that clearly draw the line between the past and the future.<…>. But if everything in this world is made of atoms and we also consist of atoms and obey physical laws, then most naturally this obvious difference between the past and the future, this irreversibility of all phenomena would be explained by the fact that some laws of atomic movement have only one direction - that atomic laws are not the same in relation to the past and the future. There must be a principle somewhere like: “You can make a stick out of a Christmas tree, but you can’t make a Christmas tree out of a stick,” in connection with which our world is constantly changing its character from a Christmas tree to a stick one - and this irreversibility of interactions should be the reason for the irreversibility of all phenomena of our life.

Lecture No. 6

“Probability and uncertainty - a look at the nature of quantum mechanics”

Here's how Feynman himself poses the problem of probability and uncertainty:

The theory of relativity states that if you believe that two events happened at the same time, then it is just your personal point view, and someone else with the same reason can assert that one of these phenomena occurred before the other, so that the concept of simultaneity turns out to be purely subjective<…>. Of course, it cannot be otherwise, since in our Everyday life we are dealing with huge aggregations of particles, very slow processes and other very specific conditions, so that our experience gives us only a very limited understanding of nature. Only a very small proportion of natural phenomena can be gleaned from direct experience. And only with the help of very subtle measurements and carefully prepared experiments can a broader view of things be achieved. And then we begin to encounter surprises. What we observe is not at all what we could have imagined, not at all what we imagined. We have to strain our imagination more not in order, as in fiction, to imagine something that does not actually exist, but in order to comprehend what is really happening. This is what I want to talk about today.

Lecture No. 7

"In search of new laws"

Strictly speaking, what I am going to talk about in this lecture cannot be called a characteristic of the laws of physics. When we talk about the nature of physical laws, we can at least assume that we are talking about nature itself. But now I want to talk not so much about nature, but about our attitude towards it. I would like to tell you about what we consider known today, what remains to be guessed, and about how laws in physics are guessed. Someone even suggested that it would be best if, as I tell you, little by little, I explain to you how to guess the law, and at the end I open it for you new law. I don't know if I can do this.

Richard Feynman about the material that drives all physical laws (about matter), about the problem of incompatibility physical principles, about the place of tacit assumptions in science and, of course, about how new laws are discovered.


	Name:	Feynman lectures on physics (in 9 volumes) + Problems and exercises with answers and solutions
	Authors:	Feynman R., Laymon R., Sands M.
	Edition:	M.: Nauka, 1965. - 260 p. + 164 s. + 234 s. + 257 pp. + 291 pp. + 339 pp. + 286 s. + 267 pp. + 254 s. + 621 pp.
	Format:	DjVu (OCR)
	Size:	3.34 Mb + 2.13 Mb + 3.52 Mb + 3.44 Mb + 3.53 Mb + 3.77 Mb + 3.62 Mb + 4.47 Mb + 3.16 Mb + 6.44 Mb
	Treatment:	-
	Links:	Volume 1. Modern science of nature. Laws of mechanics: HTTP Volume 2. Space, time, movement: HTTP Volume 3. Radiation, waves, quanta: HTTP Volume 4. Kinetics, heat, sound: HTTP Volume 5. Electricity and magnetism: HTTP Volume 6. Electrodynamics: HTTP Volume 7. Physics of continuous media: HTTP Volume 8. Quantum Mechanics (I): HTTP Volume 9. Quantum Mechanics (II): HTTP Problems and exercises with answers and solutions: HTTP

From the preface to readers of the Russian edition:
Everyone agrees that physics is one of the most interesting sciences. At the same time, many physics textbooks cannot be called interesting. Such textbooks outline everything that follows the program. They usually explain what benefits physics brings and how important it is to study it, but from them it is very rarely possible to understand why studying physics is interesting. But this side of the issue also deserves attention. How can you make a boring object both interesting and modern? First of all, those physicists who themselves work with passion and know how to convey this passion to others should think about this. The time for experimentation has already arrived. Their goal is to find the most effective ways to teach physics, which would quickly transfer to a new generation the entire stock of knowledge that has been accumulated by science throughout its history. Finding new ways to teach has also always been an important part of science. Teaching, following the development of science, must continuously change its forms, break traditions, and look for new methods. An important role here is played by the fact that in science an amazing process of a kind of simplification is constantly taking place, which makes it possible to simply and briefly present what once required many years of work.

Lectures were given in the 1961-1962 and 1962-1963 academic years; they were recorded on tape, and then (and this turned out to be a difficult task in itself) “translated” into “written English” by Professors M. Sands and R. Leighton. This unique “translation” preserves many of the features of the lecturer’s live speech, its liveliness, jokes, and digressions. However, this very valuable quality of the lectures was by no means the main and self-sufficient one. No less important were the original methods of presenting the material created by the lecturer, which reflected the bright scientific individuality of the author and his point of view on the way of teaching students physics. This, of course, is not accidental. It is known that in his scientific works Feynman always found new methods, which very quickly became generally accepted. Feynman's work on quantum electrodynamics and statistics brought him wide recognition, and his method - the so-called "Feynman diagrams" - is now used in almost all areas of theoretical physics.

Whatever they say about these lectures - whether they admire the style of presentation or lament the breaking of good old traditions - one thing remains indisputable: pedagogical experiments must begin. Probably, not everyone will agree with the author’s manner of presenting certain issues, and not everyone will agree with the assessment of the goals and prospects of modern physics. But this will stimulate the appearance of new books in which other views will be reflected. This is an experiment. But the question is not only what to tell. Another question that is no less important is in what order this should be done.

The location of sections within a general physics course and the sequence of presentation is always a conditional question. All parts of science are so connected with each other that it is often difficult to decide what should be presented first and what next. However, in most university programs and available textbooks, certain traditions are still preserved.

The rejection of the usual sequence of presentation is one of the distinctive features of Feynman's lectures. They tell not only about specific tasks, but also about the place that physics occupies in a number of other sciences, about ways to describe and study natural phenomena. Probably, representatives of other sciences - say, mathematics - will not agree with the place that Feynman assigns to these sciences. For him, as a physicist, “his” science, of course, looks the most important. But this circumstance does not take up much space in his presentation. But his story clearly reflects the reasons that motivate a physicist to carry out the hard work of a researcher, as well as the doubts that arise when he is faced with difficulties that now seem insurmountable.

A young natural scientist must not only understand why it is interesting to do science, but also feel at what cost victories are won and how sometimes difficult the roads leading to them are.

It must also be borne in mind that if at first the author did without a mathematical apparatus or used only the one presented in lectures, then the reader, as he moves forward, will be required to increase his mathematical knowledge. However, experience shows that mathematical analysis (at least its basics) is now easier to learn than physics.

Who will benefit from this book? First of all, to teachers who read it in its entirety: it will make them think about changing their existing views on how to start teaching physics. Next, students will read it. They will find a lot of new things in it in addition to what they learn in lectures. Of course, schoolchildren will also try to read it. Most of them will find it difficult to overcome everything, but what they can read and understand will help them enter modern science, the path to which is always difficult, but never boring. Anyone who does not believe that they can pass it should not undertake the study of this book! And finally, everyone else can read it. Read just for fun. This is also very useful. Feynman, in his preface, does not rate the results of his experiment very highly: too small a proportion of the students who took his course learned all the lectures. But that's how it should be. The first experience rarely brings complete success. New ideas always find only a few supporters at first and only gradually become familiar.

To the readers of the Russian edition

These are lectures on general physics given by a theoretical physicist. They are not at all similar to any known course. This may seem strange: the basic principles of classical physics, and not only classical, but also quantum, have long been established, the course of general physics has been taught all over the world in thousands of educational institutions for many years and it is time for it to turn into a standard sequence of known facts and theories, like , for example, elementary geometry at school. However, even mathematicians believe that their science should be taught differently. And there is nothing to say about physics: it is developing so intensively that even the best teachers constantly face great difficulties when they need to tell students about modern science. They complain that they have to break what are called old or habitual ideas. But where do habitual ideas come from? Usually they get into young heads at school from the same teachers, who will then talk about the inaccessibility of the ideas of modern science. Therefore, before getting to the heart of the matter, a lot of time has to be spent convincing listeners of the falsity of what was previously instilled in them as an obvious and immutable truth. It would be crazy to first tell schoolchildren “for simplicity” that the Earth is flat, and then, as a discovery, report that it is spherical. Is the path along which future specialists enter the modern world of ideas of the theory of relativity and quantum so far from this absurd example? The matter is also complicated by the fact that for the most part the lecturer and listeners are people of different generations, and it is very difficult for the lecturer to escape the temptation to lead listeners along the familiar and reliable path along which he himself at one time reached the desired heights. However, the old road does not remain the best forever. Physics is developing very quickly, and in order to keep up with it, we need to change the way we study it. Everyone agrees that physics is one of the most interesting sciences. At the same time, many physics textbooks cannot be called interesting. Such textbooks outline everything that follows the program. They usually explain what benefits physics brings and how important it is to study it, but from them it is very rarely possible to understand why studying physics is interesting. But this side of the issue also deserves attention. How can you make a boring object both interesting and modern? First of all, those physicists who themselves work with passion and know how to convey this passion to others should think about this. The time for experimentation has already arrived. Their goal is to find the most effective ways to teach physics, which would allow them to quickly transfer to a new generation the entire stock of knowledge that has been accumulated by science throughout its history. Finding new ways to teach has also always been an important part of science. Teaching, following the development of science, must continuously change its forms, break traditions, and look for new methods. An important role here is played by the fact that in science an amazing process of a kind of simplification is constantly taking place, which makes it possible to simply and briefly present what once required many years of work.

Lectures were given in the 1961–1962 and 1962–1963 academic years; they were recorded on tape, and then (and this turned out to be a difficult task in itself) “translated” into “written English” by Professors M. Sands and R. Leighton. This unique “translation” preserves many of the features of the lecturer’s live speech, its liveliness, jokes, and digressions. However, this very valuable quality of the lectures was by no means the main and self-sufficient one. No less important were the original methods of presenting the material created by the lecturer, which reflected the bright scientific individuality of the author and his point of view on the way of teaching students physics. This, of course, is not accidental. It is known that in his scientific works Feynman always found new methods, which very quickly became generally accepted. Feynman's work on quantum electrodynamics and statistics brought him wide recognition, and his method - the so-called "Feynman diagrams" - is now used in almost all areas of theoretical physics.

However, in most university programs and available textbooks, certain traditions are still preserved.

The rejection of the usual sequence of presentation is one of the distinctive features of Feynman’s lectures. They tell not only about specific tasks, but also about the place that physics occupies in a number of other sciences, about ways to describe and study natural phenomena. Probably, representatives of other sciences - say, mathematics - will not agree with the place that Feynman assigns to these sciences. For him, as a physicist, “his” science, of course, looks the most important. But this circumstance does not take up much space in his presentation. But his story clearly reflects the reasons that motivate a physicist to carry out the hard work of a researcher, as well as the doubts that arise when he is faced with difficulties that now seem insurmountable.

A young natural scientist must not only understand why it is interesting to do science, but also feel at what cost victories are won and how sometimes difficult the roads leading to them are.

Feynman's lectures were published in the United States in three large volumes. The first contains mainly lectures on mechanics and heat theory, the second - electrodynamics and continuum physics, and the third - quantum mechanics. To make the book available more readers and to make it more convenient to use, the Russian edition will be published in small editions. The first four of them correspond to the first volume of the American edition.

Who will benefit from this book? First of all, to teachers who read it in its entirety: it will make them think about changing their existing views on how to start teaching physics. Next, students will read it. They will find a lot of new things in it in addition to what they learn in lectures. Of course, schoolchildren will also try to read it. Most of them will find it difficult to master everything, but what they can read and understand will help them enter modern science, the path to which is always difficult, but never boring. Anyone who does not believe that they can pass it should not undertake the study of this book! And finally, everyone else can read it. Read just for fun. This is also very useful. Feynman, in his preface, does not rate the results of his experiment very highly: too small a proportion of the students who took his course learned all the lectures. But that's how it should be.