Fundamental interactions. Basic physical interactions

1.1. Gravity.

1.2. Electromagnetism.

1.3. Weak interaction.

1.4. The problem of the unity of physics.

2. Classification elementary particles.

2.1. characteristics of subatomic particles.

2.2. leptons.

2.3. Hadrons.

2.4. Particles are carriers of interactions.

3. Theories of elementary particles.

3.1. Quantum electrodynamics.

3.2. Quark theory.

3.3. Theory of electroweak interaction.

3.4. Quantum chromodynamics.

3.5. On the way to great unification.

References.

Introduction.

In the middle and second half of the twentieth century, truly amazing results were obtained in those branches of physics that study the fundamental structure of matter. First of all, this manifested itself in the discovery of a whole host of new subatomic particles. They are usually called elementary particles, but not all of them are truly elementary. Many of them, in turn, consist of even more elementary particles. The world of subatomic particles is truly diverse. These include protons and neutrons that make up atomic nuclei, as well as electrons orbiting the nuclei. But there are also particles that are practically never found in the matter around us. Their life time is extremely short, it is the smallest fractions of a second. After this extremely short time, they disintegrate into ordinary particles. There are an amazing number of such unstable short-lived particles: several hundred of them are already known. In the 1960s and 1970s, physicists were completely baffled by the number, variety, and strangeness of the newly discovered subatomic particles. There seemed to be no end to them. It is completely unclear why there are so many particles. Are these elementary particles chaotic and random fragments of matter? Or perhaps they hold the key to understanding the structure of the Universe? The development of physics in subsequent decades showed that there is no doubt about the existence of such a structure. At the end of the twentieth century. physics is beginning to understand the significance of each of the elementary particles. The world of subatomic particles is characterized by a deep and rational order. This order is based on fundamental physical interactions.

1. Fundamental physical interactions.

In your everyday life a person is faced with many forces acting on their bodies. Here is the force of the wind or the oncoming flow of water, air pressure, a powerful release of explosive chemicals, human muscular strength, the weight of heavy objects, the pressure of light quanta, the attraction and repulsion of electrical charges, seismic waves that sometimes cause catastrophic destruction, and volcanic eruptions that led to the death of civilization, etc. Some forces act directly upon contact with the body, others, for example, gravity, act at a distance, through space. But, as it turned out as a result of the development of theoretical natural science, despite such great diversity, all forces operating in nature can be reduced to just four fundamental interactions. It is these interactions that are ultimately responsible for all changes in the world; they are the source of all transformations of bodies and processes. Studying properties fundamental interactions amounts to main task modern physics.

Gravity.

In the history of physics, gravity became the first of the four fundamental interactions to be the subject of scientific research. After its appearance in the 17th century. Newton's theory of gravity - law universal gravity- it was possible for the first time to realize the true role of gravity as a force of nature. Gravity has a number of features that distinguish it from other fundamental interactions. The most surprising feature of gravity is its low intensity. The magnitude of gravitational interaction between the components of a hydrogen atom is 10n, where n = - 3 9, from the force of interaction electric charges. (If the dimensions of the hydrogen atom were determined by gravity, and not by the interaction between electric charges, then the lowest (closest to the nucleus) orbit of the electron would be larger in size than the observable part of the Universe!) (If the dimensions of the hydrogen atom were determined by gravity, and not by the interaction between electrical charges, then the lowest (closest to the nucleus) electron orbit would be larger in size than the observable part of the Universe!). It may seem surprising that we feel gravity at all, since it is so weak. How can she become the dominant force in the Universe? It's all about the second amazing feature of gravity - its universality. Nothing in the Universe is free from gravity. Each particle experiences the action of gravity and is itself a source of gravity. Since every particle of matter exerts a gravitational pull, gravity increases as larger clumps of matter form. We feel gravity in everyday life because all the atoms of the Earth work together to attract us. And although the effect of the gravitational attraction of one atom is negligible, the resulting force of attraction from all atoms can be significant. Gravity is a long-range force of nature. This means that, although the intensity of gravitational interaction decreases with distance, it spreads in space and can affect bodies very distant from the source. On an astronomical scale, gravitational interactions tend to play a major role. Thanks to long-range action, gravity prevents the Universe from falling apart: it holds planets in orbits, stars in galaxies, galaxies in clusters, clusters in the Metagalaxy. The gravitational force acting between particles is always an attractive force: it tends to bring the particles closer together. Gravitational repulsion has never been observed before (Although in the traditions of quasi-scientific mythology there is a whole field called levitation - the search for the “facts” of antigravity). Since the energy stored in any particle is always positive and gives it positive mass, particles under the influence of gravity always tend to get closer. What is gravity, a certain field or a manifestation of the curvature of space-time - there is still no clear answer to this question. As we have already noted, there are different opinions and concepts of physicists on this matter.

Electromagnetism.

Electrical forces are much larger than gravitational forces. Unlike the weak gravitational interaction, the electrical forces acting between bodies of normal size can be easily observed. Electromagnetism has been known to people since time immemorial (auroras, lightning flashes, etc.). For a long time, electrical and magnetic processes were studied independently of each other. As we already know, the decisive step in the knowledge of electromagnetism was made in the middle of the 19th century. J.C. Maxwell, who combined electricity and magnetism in a unified theory of electromagnetism - the first unified field theory. The existence of the electron was firmly established in the 90s of the last century. It is now known that the electric charge of any particle of matter is always a multiple of the fundamental unit of charge - a kind of “atom” of charge. Why this is so is an extremely interesting question. However, not all material particles are carriers of electric charge. For example, the photon and neutrino are electrically neutral. In this respect, electricity differs from gravity. All material particles create a gravitational field, whereas with electrical magnetic field Only charged particles are bound. Like electric charges, like magnetic poles repel, and opposite ones attract. However, unlike electric charges, magnetic poles do not occur individually, but only in pairs - a north pole and a south pole. Since ancient times, attempts have been known to obtain, by dividing a magnet, only one isolated magnetic pole - a monopole. But they all ended in failure. Perhaps the existence of isolated magnetic poles in nature is excluded? There is no definite answer to this question yet. Some theoretical concepts allow for the possibility of a monopole. Like electrical and gravitational interactions, the interaction of magnetic poles obeys the inverse square law. Consequently, electric and magnetic forces are “long-range”, and their effect is felt at large distances from the source. Thus, the Earth's magnetic field extends far into outer space. The Sun's powerful magnetic field fills the entire Solar System. There are also galactic magnetic fields. Electromagnetic interaction determines the structure of atoms and is responsible for the vast majority of physical and chemical phenomena and processes (except nuclear).

Weak interaction.

Physics has moved slowly towards identifying the existence of the weak interaction. The weak force is responsible for particle decays; and therefore its manifestation was confronted with the discovery of radioactivity and the study of beta decay. Beta decay was found in highest degree strange feature. Research led to the conclusion that this decay violates one of the fundamental laws of physics - the law of conservation of energy. It seemed that in this decay part of the energy disappeared somewhere. In order to “save” the law of conservation of energy, W. Pauli suggested that, together with the electron, during beta decay, another particle is emitted. It is neutral and has an unusually high penetrating ability, as a result of which it could not be observed. E. Fermi called the invisible particle "neutrino". But the prediction and detection of neutrinos is only the beginning of the problem, its formulation. It was necessary to explain the nature of neutrinos, but there remained a lot of mystery here. The fact is that both electrons and neutrinos were emitted by unstable nuclei. But it was irrefutably proven that there are no such particles inside nuclei. How did they arise? It has been suggested that electrons and neutrinos do not exist in the nucleus in " finished form", but are somehow formed from the energy of a radioactive nucleus. Further research showed that the neutrons included in the nucleus, left to themselves, after a few minutes decay into a proton, electron and neutrino, i.e. instead of one particle, three new ones appear. The analysis led to the conclusion that known forces could not cause such a decay. It was apparently generated by some other, unknown force. Research showed that this force corresponds to some weak interaction It is much weaker than the electromagnetic one, although it is stronger than the gravitational one. at very small distances. The radius of the weak interaction is very small. The weak interaction stops at a distance greater than 10n cm (where n = - 1 6) from the source and therefore cannot affect macroscopic objects, but is limited to individual subatomic particles. unstable elementary particles participate in weak interaction. The theory of weak interaction was created in the late 60s by S. Weinberg and A. Salam. Since Maxwell's theory of the electromagnetic field, the creation of this theory was the largest step towards the unity of physics. 10.

Strong interaction.

The last in the series of fundamental interactions is the strong interaction, which is a source of enormous energy. The most typical example of energy released by the strong force is our Sun. In the depths of the Sun and stars, starting from a certain time, thermonuclear reactions caused by strong interaction continuously occur. But man has also learned to release strong interactions: a hydrogen bomb has been created, technologies for controlled thermonuclear reactions have been designed and improved. Physics came to the idea of ​​the existence of strong interaction during the study of the structure of the atomic nucleus. Some force must hold the protons in the nucleus, preventing them from scattering under the influence of electrostatic repulsion. Gravity is too weak for this; Obviously, some new interaction is needed, moreover, stronger than electromagnetic. It was subsequently discovered. It turned out that although the strong interaction significantly exceeds all other fundamental interactions in its magnitude, it is not felt outside the nucleus. The radius of action of the new force turned out to be very small. The strong force drops off sharply at a distance from the proton or neutron greater than about 10n cm (where n = - 13). In addition, it turned out that not all particles experience strong interactions. It is experienced by protons and neutrons, but electrons, neutrinos and photons are not subject to it. Only heavier particles participate in strong interactions. The theoretical explanation of the nature of the strong interaction has been difficult to develop. A breakthrough came in the early 60s, when the quark model was proposed. In this theory, neutrons and protons are considered not as elementary particles, but as composite systems built from quarks. Thus, in fundamental physical interactions the difference between long-range and short-range forces is clearly visible. On the one hand, there are interactions of unlimited range (gravity, electromagnetism), and on the other, interactions of short range (strong and weak). The world of physical elements as a whole unfolds in the unity of these two polarities and is the embodiment of the unity of the extremely small and the extremely large - short-range action in the microworld and long-range action throughout the Universe.

The problem of the unity of physics.

Knowledge is a generalization of reality, and therefore the goal of science is the search for unity in nature, linking disparate fragments of knowledge into a single picture. In order to create unified system, it is necessary to discover a connecting link between various branches of knowledge, some fundamental relationship. The search for such connections and relationships is one of the main tasks of scientific research. Whenever it is possible to establish such new connections, the understanding of the surrounding world deepens significantly, new ways of knowing are formed that point the way to previously unknown phenomena. Establishing deep connections between different areas of nature is both a synthesis of knowledge and a method that guides scientific research along new, untrodden roads. Newton's discovery of the connection between the attraction of bodies under terrestrial conditions and the movement of planets marked the birth of classical mechanics, on the basis of which the technological base was built modern civilization. The establishment of a connection between the thermodynamic properties of gas and the chaotic movement of molecules put the atomic-molecular theory of matter on a solid basis. In the middle of the last century, Maxwell created a unified electromagnetic theory that covered both electrical and magnetic phenomena. Then, in the 20s of our century, Einstein made attempts to combine unified theory electromagnetism and gravity. But by the middle of the twentieth century. The situation in physics has changed radically: two new fundamental interactions have been discovered - strong and weak, i.e. when creating a unified physics, one has to take into account not two, but four fundamental interactions. This somewhat cooled the ardor of those who hoped for quick solution this problem. But the idea itself was not seriously questioned, and the enthusiasm for the idea of ​​a single description did not go away. There is a point of view that all four (or at least three) interactions represent phenomena of the same nature and their unified theoretical description must be found. The prospect of creating a unified theory of the world of physical elements based on a single fundamental interaction remains very attractive. This is the main dream of 20th century physicists. But for a long time it remained only a dream, and a very vague one. However, in the second half of the twentieth century. there were prerequisites for the realization of this dream and the confidence that this was by no means a matter of the distant future. It looks like it could soon become a reality. The decisive step towards a unified theory was made in the 60-70s. with the creation first of the theory of quarks, and then of the theory of electroweak interaction. There is reason to believe that we are on the threshold of a more powerful and deeper unification than ever before. There is a growing belief among physicists that the contours of a unified theory of all fundamental interactions - the Grand Unification - are beginning to emerge.

2 . Classification of elementary particles.

That various substances contain quite a lot of elementary particles, fundamental physical interactions are represented by four types: strong, electromagnetic, weak and gravitational. The latter is considered the most comprehensive.

All macrobodies and microparticles, without exception, are subject to gravity. Absolutely all elementary particles are subject to gravitational influence. It manifests itself in the form of universal gravity. This fundamental interaction controls the most global processes occurring in the Universe. Gravity provides structural stability solar system.

According to modern ideas, fundamental interactions arise due to the exchange of particles. Gravity is formed through the exchange of gravitons.

Fundamental interactions - gravitational and electromagnetic - are long-range in nature. The corresponding forces can manifest themselves over considerable distances. These fundamental interactions have their own characteristics.

Described by charges of the same type (electric). In this case, the charges can have both a positive and a negative sign. Electromagnetic forces, unlike (gravity), can act as repulsive and attractive forces. This interaction causes chemical and physical properties various substances, materials, living tissue. Electromagnetic forces drive both electronic and electrical equipment, connecting charged particles with each other.

Fundamental interactions are known beyond a small circle of astronomers and physicists in varying degrees.

Despite being less famous (compared to other types), weak forces play important role in the life of the Universe. So, if there were no weak interaction, the stars and the Sun would go out. These forces are short-range. The radius is approximately a thousand times smaller than that of nuclear forces.

Nuclear forces are considered the most powerful of all. The strong interaction determines the bonds only between hadrons. Acting between nucleons nuclear forces are its manifestation. approximately one hundred times more powerful than electromagnetic. Differing from gravitational (as, in fact, from electromagnetic), it is short-range at a distance of more than 10-15 m. In addition, it can be described using three charges that form complex combinations.

Range is considered the most important feature of fundamental interaction. The radius of action is the maximum distance that is formed between particles. Outside of this, interaction can be neglected. A small radius characterizes the force as short-range, a large radius as long-range.

As noted above, weak and strong interactions are considered short-range. Their intensity decreases quite quickly as the distance between particles increases. These interactions manifest themselves at small distances inaccessible to perception through the senses. In this regard, these forces were discovered much later than the others (only in the twentieth century). In this case, quite complex experimental setups were used. Gravitational and electromagnetic types fundamental interactions are considered long-range. They are characterized by a slow decrease as the distance between particles increases and are not endowed with a finite range of action.

Interaction in physics is the influence of bodies or particles on each other, leading to a change in their motion.

Proximity and long-range action (or action at a distance). There have long been two points of view in physics about how bodies interact. The first of them assumed the presence of some agent (for example, ether), through which one body transmits its influence to another, and with a finite speed. This is the theory of short-range action. The second assumed that the interaction between bodies occurs through empty space, which does not take any part in the transmission of interaction, and the transmission occurs instantly. This is the theory of long-range action. It seemed to have finally won after Newton’s discovery of the law of universal gravitation. For example, it was believed that the movement of the Earth should immediately lead to a change in the gravitational force acting on the Moon. In addition to Newton himself, the concept of long-range action was later adhered to by Coulomb and Ampere.

After the discovery and study of the electromagnetic field (see Electromagnetic field), the theory of long-range action was rejected, since it was proven that the interaction of electrically charged bodies does not occur instantly, but with a finite speed (equal to the speed of light: c = 3,108 m/s) and movement one of the charges leads to a change in the forces acting on the other charges, not instantly, but after some time. Arose new theory short-range interaction, which was then extended to all other types of interactions. According to the theory of short-range action, interaction is carried out through corresponding fields surrounding the bodies and continuously distributed in space (i.e., the field is the intermediary that transmits the action of one body to another). The interaction of electric charges - through an electromagnetic field, universal gravitation - through a gravitational field.

Today, physics knows four types of fundamental interactions that exist in nature (in order of increasing intensity): gravitational, weak, electromagnetic and strong interactions.

Fundamental interactions are those that cannot be reduced to other types of interactions.

Interaction Interacting particles "Relative Radius of action, m intensity Gravitational Everything except the photon Electromagnetic Charged particles

Fundamental interactions differ in intensity and range of action (see Table 1.1). The radius of action is the maximum distance between particles, beyond which their interaction can be neglected.

According to the radius of action, fundamental interactions are divided into long-range (gravitational and electromagnetic) and short-range (weak and strong) (see Table 1.1).

Gravitational interaction is universal: all bodies in nature participate in it - from stars, planets and galaxies to microparticles: atoms, electrons, nuclei. Its range of action is infinity. However, both for elementary particles of the microworld and for the objects of the macroworld that surround us, the forces of gravitational interaction are so small that they can be neglected (see Table 1.1). It becomes noticeable with increasing mass of interacting bodies and therefore determines behavior celestial bodies and the formation and evolution of stars.

Weak interaction is inherent in all elementary particles except the photon. It is responsible for the majority nuclear reactions decay and many transformations of elementary particles.

Electromagnetic interaction determines the structure of matter, connecting electrons and nuclei in atoms and molecules, combining atoms and molecules into various substances. It determines chemical and biological processes. Electromagnetic interaction is the cause of such phenomena as elasticity, friction, viscosity, magnetism and constitutes the nature of the corresponding forces. It does not have a significant effect on the motion of macroscopic electrically neutral bodies.

The strong interaction occurs between hadrons, which is what holds the nucleons in the nucleus.

In 1967, Sheldon Glashow, Abdus Salam, and Steven Weinberg created a theory that unified the electromagnetic and weak forces into a single electromagnetic force. weak interaction with a range of 10~17 m, within which the difference between weak and electromagnetic interactions disappears.

Currently, the theory of grand unification has been put forward, according to which there are only two types of interactions: unified, which includes strong, weak and electromagnetic interactions, and gravitational interaction.

There is also an assumption that all four interactions are special cases of the manifestation of a single interaction.

In mechanics, the mutual action of bodies on each other is characterized by force (see Force). More general characteristic interaction is potential energy (see Potential energy).

Forces in mechanics are divided into gravitational, elastic and frictional. As mentioned above, the nature of mechanical forces is determined by gravitational and electromagnetic interactions. Only these interactions can be considered as forces in the sense of Newtonian mechanics. Strong (nuclear) and weak interactions manifest themselves at such small distances that Newton’s laws of mechanics, and with them the concept mechanical force lose their meaning. Therefore, the term “force” in these cases should be perceived as “interaction”.

The ability to interact is the most important and integral property of matter. It is interactions that ensure the unification of various material objects of the mega-, macro- and microworld into systems. All famous modern science forces are reduced to four types of interactions, which are called fundamental: gravitational, electromagnetic, weak and strong.

Gravitational interaction first became the object of study of physics in the 17th century. I. Newton's theory of gravity, which is based on the law of universal gravitation, has become one of the components of classical mechanics. The law of universal gravitation states: between two bodies there is an attractive force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them (2.3). Any material particle is a source of gravitational influence and experiences it on itself. As the mass increases, gravitational interactions increase, i.e., the greater the mass of interacting substances, the stronger the gravitational forces. The forces of gravity are forces of attraction. IN lately physicists have suggested the existence of gravitational repulsion, which acted in the very first moments of the existence of the Universe (4.2), but this idea has not yet been confirmed. Gravitational interaction is the weakest currently known. The gravitational force acts over very large distances; its intensity decreases with increasing distance, but does not disappear completely. It is believed that the carrier of gravitational interaction is the hypothetical particle graviton. In the microworld, gravitational interaction does not play a significant role, but in macro- and especially mega-processes it plays a leading role.

Electromagnetic interaction became the subject of study in physics of the 19th century. The first unified theory of the electromagnetic field was the concept of J. Maxwell (2.3). Unlike the gravitational force, electromagnetic interactions exist only between charged particles: electric field– between two stationary charged particles, magnetic – between two moving charged particles. Electromagnetic forces can be either attractive or repulsive forces. Likely charged particles repel, oppositely charged particles attract. The carriers of this type of interaction are photons. Electromagnetic interaction manifests itself in the micro-, macro- and mega-worlds.

In the middle of the 20th century. was created quantum electrodynamics– a theory of electromagnetic interaction that satisfied the basic principles quantum theory and the theory of relativity. In 1965, its authors S. Tomanaga, R. Feynman and J. Schwinger were awarded the Nobel Prize. Quantum electrodynamics describes the interaction of charged particles - electrons and positrons.

Weak interaction was discovered only in the 20th century, in the 1960s. built general theory weak interaction. The weak force is associated with the decay of particles, so its discovery followed only after the discovery of radioactivity. When observing radioactive decay particles, phenomena were discovered that seemed to contradict the law of conservation of energy. The fact is that during the decay process, part of the energy “disappeared.” Physicist W. Pauli suggested that during the process of radioactive decay of a substance, a particle with high penetrating power is released along with an electron. This particle was later named "neutrino". It turned out that as a result of weak interactions, the neutrons that make up the atomic nucleus decay into three types of particles: positively charged protons, negatively charged electrons and neutral neutrinos. The weak interaction is much smaller than the electromagnetic interaction, but greater than the gravitational interaction, and unlike them, it spreads over small distances - no more than 10-22 cm. That's why for a long time weak interaction was not observed experimentally. The carriers of the weak interaction are bosons.

In the 1970s a general theory of electromagnetic and weak interaction was created, called theory of electroweak interaction. Its creators S. Weinberg, A. Salam and S. Glashow in 1979 received Nobel Prize. The theory of electroweak interaction considers two types of fundamental interactions as manifestations of a single, deeper one. Thus, at distances of more than 10-17 cm, the electromagnetic aspect of phenomena predominates, at smaller distances of to the same degree Both the electromagnetic and weak aspects are important. The creation of the theory under consideration meant that, united in classical physics of the 19th century, within the framework of the Faraday-Maxwell theory, electricity, magnetism and light in the last third of the 20th century. supplemented by the phenomenon of weak interaction.

Strong interaction was also discovered only in the 20th century. It holds protons in the nucleus of an atom, preventing them from scattering under the influence of electromagnetic repulsive forces. Strong interaction occurs at distances of no more than 10-13 cm and is responsible for the stability of nuclei. The nuclei of elements at the end of the periodic table are unstable because their radius is large and, accordingly, the strong interaction loses its intensity. Such nuclei are subject to decay, which is called radioactive. Strong interaction is responsible for the formation of atomic nuclei; only heavy particles participate in it: protons and neutrons. Nuclear interactions do not depend on the particle charge; the carriers of this type of interaction are gluons. Gluons are combined into a gluon field (similar to an electromagnetic field), due to which the strong interaction occurs. In its power, the strong interaction surpasses other known ones and is a source of enormous energy. An example of strong interaction is thermonuclear reactions in the Sun and other stars. The principle of strong interaction was used to create hydrogen weapons.

The theory of strong interaction is called quantum chromodynamics. According to this theory, the strong interaction is the result of the exchange of gluons, which results in the connection of quarks in hadrons. Quantum chromodynamics continues to develop, and although it cannot yet be considered a complete concept of the strong interaction, nevertheless this physical theory has a solid experimental base.

IN modern physics The search for a unified theory that would explain all four types of fundamental interactions continues. The creation of such a theory would also mean the construction of a unified concept of elementary particles. This project was called the “Great Unification”. The basis for the belief that such a theory is possible is the fact that at short distances (less than 10-29 cm) and at high energies (more than 1014 GeV) electromagnetic, strong and weak interactions are described in the same way, which means their common nature. However, this conclusion is still only theoretical; it has not yet been possible to verify it experimentally.

Various competing Grand Unified theories interpret cosmology (4.2) differently. For example, it is assumed that at the moment of the birth of our Universe, conditions existed in which all four fundamental interactions manifested themselves in the same way. Creating a theory that explains all four types of interactions on a unified basis will require a synthesis of the theory of quarks, quantum chromodynamics, modern cosmology and relativistic astronomy.

However, the search for a unified theory of four types of fundamental interactions does not mean that the emergence of other interpretations of matter is impossible: the discovery of new interactions, the search for new elementary particles, etc. Some physicists express doubts about the possibility of a unified theory. Thus, the creators of synergetics I. Prigogine and I. Stengers in the book “Time, Chaos, Quantum” write: “the hope for building such a “theory of everything” from which it would be possible to deduce full description physical reality, will have to be abandoned,” and justify their thesis by the laws formulated within the framework of synergetics (7.2).

Conservation laws played an important role in understanding the mechanisms of interaction of elementary particles, their formation and decay. In addition to the conservation laws operating in the macroworld (the law of conservation of energy, the law of conservation of momentum and the law of conservation of angular momentum), new ones were discovered in the physics of the microworld: the law of conservation of baryon, lepton charges, strangeness, etc.

Each conservation law is associated with some kind of symmetry in the surrounding world. In physics, symmetry is understood as invariance, the immutability of a system relative to its transformations, i.e., relative to changes in the series physical conditions. The German mathematician Emma Noether established a connection between the properties of space and time and the conservation laws of classical physics. A fundamental theorem of mathematical physics, called Noether's theorem, states that from the homogeneity of space the law of conservation of momentum follows, from the homogeneity of time the law of conservation of energy follows, and from the isotropy of space the law of conservation of angular momentum follows. These laws are fundamental in nature and are valid for all levels of existence of matter.

The law of conservation and transformation of energy states that energy does not disappear and does not appear again, but only passes from one form to another. The law of conservation of momentum postulates the constancy of momentum closed system over time. The law of conservation of angular momentum states that the angular momentum of a closed-loop system remains constant over time. Conservation laws are a consequence of symmetry, i.e. invariance, immutability of the structure of material objects relative to transformations, or changes in the physical conditions of their existence.

To understand whether it is worth continuing to write short sketches that literally explain different physical phenomena and processes. The result dispelled my doubts. I'll continue. But in order to approach rather complex phenomena, you will have to make separate sequential series of posts. So, in order to get to the story about the structure and evolution of the Sun and other types of stars, you will have to start with a description of the types of interaction between elementary particles. Let's start with this. No formulas.
In total, four types of interaction are known in physics. Everyone is well known gravitational And electromagnetic. And almost unknown to the general public strong And weak. Let us describe them sequentially.
Gravitational interaction . People have known it since ancient times. Because it is constantly in the gravity field of the Earth. And from school physics we know that the force of gravitational interaction between bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. Under the influence of gravitational force, the Moon rotates around the Earth, the Earth and other planets around the Sun, and the latter, together with other stars, around the center of our Galaxy.
The rather slow decrease in the strength of gravitational interaction with distance (inversely proportional to the square of the distance) forces physicists to talk about this interaction as long-range. In addition, the forces of gravitational interaction acting between bodies are only forces of attraction.
Electromagnetic interaction . In the simplest case of electrostatic interaction, as we know from school physics, the force of attraction or repulsion between electrically charged particles is proportional to the product of their electric charges and inversely proportional to the square of the distance between them. Which is very similar to the law of gravitational interaction. The only difference is that electric charges with the same signs repel, and those with different signs attract. Therefore, electromagnetic interaction, like gravitational interaction, is called by physicists long-range.
At the same time, electromagnetic interaction is more complex than gravitational interaction. From school physics we know that the electric field is created by electric charges, magnetic charges does not exist in nature, but a magnetic field is created electric currents.
In fact, an electric field can also be created by a time-varying magnetic field, and a magnetic field can also be created by a time-varying magnetic field electric field. The latter circumstance makes it possible to exist electromagnetic field without any electrical charges or currents at all. And this possibility is realized in the form of electromagnetic waves. For example, radio waves and light quanta.
Because electrical and gravitational forces are equally dependent on distance, it is natural to try to compare their intensities. Thus, for two protons, the forces of gravitational attraction turn out to be 10 to the 36th power of times (a billion billion billion billion times) weaker than the forces of electrostatic repulsion. Therefore, in the physics of the microworld, gravitational interaction can quite reasonably be neglected.
Strong interaction . This - short-range strength. In the sense that they act at distances only of the order of one femtometer (one trillionth of a millimeter), and at large distances their influence is practically not felt. Moreover, at distances of the order of one femtometer, the strong interaction is about a hundred times more intense than the electromagnetic one.
That is why equally electrically charged protons in atomic nucleus They are not repelled from each other by electrostatic forces, but are held together by strong interactions. Because the dimensions of a proton and a neutron are about one femtometer.
Weak interaction . It is really very weak. Firstly, it operates at distances a thousand times smaller than one femtometer. And at long distances it is practically not felt. Therefore, like the strong one, it belongs to the class short-range. Secondly, its intensity is approximately one hundred billion times less than the intensity of electromagnetic interaction. The weak force is responsible for some decays of elementary particles. Including free neutrons.
There is only one type of particle that interacts with matter only through weak interaction. This is a neutrino. Through every square centimeter Almost a hundred billion solar neutrinos pass through our skin every second. And we don’t notice them at all. In the sense that during our lifetime, it is unlikely that a few neutrinos will interact with the matter of our body.
We will not talk about theories that describe all these types of interactions. For what is important to us is a high-quality picture of the world, and not the delights of theorists.