They are not included in the number of fundamental interactions. Types of interactions

For a long time, man has sought to know and understand the physical world around him. It turns out that all the infinite variety of physical processes occurring in our world can be explained by the existence in nature of a very small number of fundamental interactions. Their interaction with each other explains the orderly arrangement celestial bodies in the Universe. They are the “elements” that move celestial bodies, generate light and make life itself possible (see. Application ).
Thus, all processes and phenomena in nature, be it an apple falling, a supernova explosion, a penguin jumping, or the radioactive decay of substances, occur as a result of these interactions.
The structure of the substance of these bodies is stable due to the bonds between its constituent particles.

1. TYPES OF INTERACTIONS

Despite the fact that matter contains a large number of elementary particles, there are only four types of fundamental interactions between them: gravitational, weak, electromagnetic and strong.
The most comprehensive is gravitational interaction . All material interactions, without exception, are subject to it - both microparticles and macrobodies. This means that everyone is involved elementary particles. It manifests itself in the form of universal gravity. Gravity (from Latin Gravitas - heaviness) controls the most global processes in the Universe, in particular, ensures the structure and stability of our solar system. According to modern concepts, each of the interactions arises as a result of the exchange of particles called carriers of this interaction. Gravitational interaction is carried out through exchange gravitons .
, like gravitational, is long-range in nature: the corresponding forces can manifest themselves at very significant distances. Electromagnetic interaction is described by charges of one type (electric), but these charges can already have two signs - positive and negative. Unlike gravity, electromagnetic forces can be both attractive and repulsive forces. Physical and Chemical properties of various substances, materials and living tissue itself are determined by this interaction. It also powers all electrical and electronic equipment, i.e. connects only charged particles with each other. The theory of electromagnetic interaction in the macrocosm is called classical electrodynamics.
Weak interaction less known outside a narrow circle of physicists and astronomers, but this does not detract from its significance. Suffice it to say that if it were not there, the Sun and other stars would go out, because in the reactions that ensure their glow, the weak interaction plays a very important role. The weak interaction is short-range: its radius is approximately 1000 times smaller than that of nuclear forces.
Strong interaction – the most powerful of all the others. It defines connections only between hadrons. Nuclear forces acting between nucleons in an atomic nucleus are a manifestation of this type of interaction. It is about 100 times stronger than electromagnetic energy. Unlike the latter (and also gravitational), it is, firstly, short-range at a distance greater than 10–15 m (on the order of the size of the nucleus), the corresponding forces between protons and neutrons, sharply decreasing, cease to bind them to each other. Secondly, it can be described satisfactorily only by means of three charges (colors) forming complex combinations.
Table 1 roughly presents the most important elementary particles belonging to the main groups (hadrons, leptons, interaction carriers).

Table 1

Participation of basic elementary particles in interactions

The most important characteristic of a fundamental interaction is its range of action. The radius of action is the maximum distance between particles, beyond which their interaction can be neglected (Table 2). At a small radius the interaction is called short-acting , with large – long-range .

table 2

Main characteristics of fundamental interactions

Strong and weak interactions are short-range . Their intensity decreases rapidly with increasing distance between particles. Such interactions occur at a short distance, inaccessible to perception by the senses. For this reason, these interactions were discovered later than others (only in the 20th century) using complex experimental setups. Electromagnetic and gravitational interactions are long-range . Such interactions decrease slowly with increasing distance between particles and do not have a finite range of action.

2. INTERACTION AS A CONNECTION OF STRUCTURES OF MATTER

In the atomic nucleus, the bond between protons and neutrons determines strong interaction . It provides exceptional core strength, which underlies the stability of the substance under terrestrial conditions.

Weak interaction a million times less intense than strong. It acts between most elementary particles located at a distance of less than 10–17 m from each other. Weak interaction determines the radioactive decay of uranium and thermonuclear fusion reactions in the Sun. As you know, it is the radiation of the Sun that is the main source of life on Earth.

Electromagnetic interaction , being long-range, determines the structure of matter beyond the range of the strong interaction. The electromagnetic force binds electrons and nuclei in atoms and molecules. It combines atoms and molecules into various substances and determines chemical and biological processes. This interaction is characterized by forces of elasticity, friction, viscosity, and magnetic forces. In particular, the electromagnetic repulsion of molecules located at short distances causes a ground reaction force, as a result of which we, for example, do not fall through the floor. Electromagnetic interaction does not have a significant effect on the mutual motion of macroscopic bodies large mass, since each body is electrically neutral, i.e. it contains approximately same number positive and negative charges.

Gravitational interaction directly proportional to the mass of interacting bodies. Due to the small mass of elementary particles, the gravitational interaction between particles is small compared to other types of interaction, therefore, in the processes of the microworld, this interaction is insignificant. As the mass of interacting bodies increases (i.e., as the number of particles they contain increases), the gravitational interaction between the bodies increases in direct proportion to their mass. In this regard, in the macrocosm, when considering the movement of planets, stars, galaxies, as well as the movement of small macroscopic bodies in their fields, gravitational interaction becomes decisive. It holds the atmosphere, seas and everything living and nonliving on Earth, the Earth revolving in orbit around the Sun, the Sun within the Galaxy. Gravitational interaction plays a major role in the formation and evolution of stars. Fundamental interactions of elementary particles are depicted using special diagrams, in which a real particle corresponds to a straight line, and its interaction with another particle is depicted either by a dotted line or a curve (Fig. 1).

Diagrams of interactions of elementary particles

Modern physical concepts of fundamental interactions are constantly being refined. In 1967 Sheldon Glashow, Abdus Salam And Steven Weinberg created a theory according to which the electromagnetic and weak interactions are a manifestation of a single electroweak interaction. If the distance from an elementary particle is less than the radius of action of weak forces (10–17 m), then the difference between electromagnetic and weak interactions disappears. Thus, the number of fundamental interactions was reduced to three.

The theory of the "Great Unification".
Some physicists, in particular G. Georgi and S. Glashow, suggested that during the transition to higher energies another merger should occur - the unification of the electroweak interaction with the strong one. The corresponding theoretical schemes are called the “Grand Unification” Theory. And this theory is currently being tested experimentally. According to this theory, which combines strong, weak and electromagnetic interactions, there are only two types of interactions: unified and gravitational. It is possible that all four interactions are only partial manifestations of a single interaction. The premises of such assumptions are considered when discussing the theory of the origin of the Universe (the Big Bang theory). Theory " Big Bang” explains how the combination of matter and energy gave birth to stars and galaxies.

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 discovery and exploration electromagnetic field(see Electromagnetic field) the theory of long-range action was rejected, since it was proven that the interaction of electrically charged bodies is not instantaneous, but with a finite speed (equal to the speed of light: c = 3,108 m/s) and the movement of one of the charges leads to a change forces acting on other charges, not instantly, but after some time. A new theory of short-range interaction arose, 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.

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.

By range fundamental interactions They 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 an increase in the mass of interacting bodies and therefore determines the behavior of 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 combines the electromagnetic and weak forces into a single electroweak force with a range of 10-17 m, within which the distinction between the 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 of mechanical force, become meaningless. Therefore, the term “force” in these cases should be perceived as “interaction”.

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 the structural stability of the solar system.

In accordance with 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 outside a small circle of astronomers and physicists to varying degrees.

Despite being less well known (compared to other types), weak forces play an 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. The nuclear forces acting between nucleons 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 of 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.

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, became one of the components classical mechanics. Any material particle is a source of gravitational influence and experiences it on itself. As 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. 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. 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– the theory of electromagnetic interaction, which describes the interaction of charged particles - electrons and positrons. In 1965, its authors S. Tomanaga, R. Feynman and J. Schwinger were awarded the Nobel Prize.

Weak interaction was discovered only in the 20th century, in the 60s. 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. 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 significantly less 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 is why for a long time weak interaction was not observed experimentally. The carriers of the weak interaction are bosons.

In the 70s XX century a general theory of electromagnetic and weak interaction was created, called theory of electroweak interaction. Its creators S. Weinberg, A. Sapam 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 greater than 10–17 cm, the electromagnetic aspect of phenomena predominates; at shorter distances, both the electromagnetic and weak aspects are equally 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 kernels of the elements located at the end of the table D.I. Mendeleev 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 education atomic nuclei, only heavy particles participate in it: protons and neutrons. Nuclear interactions do not depend on the charge of particles; 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; it cannot yet be considered a complete concept of the strong interaction, but it has a solid experimental basis.

IN modern physics The search continues for a unified theory that would explain all four types of fundamental interactions. 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 10 14 GeV), electromagnetic, strong and weak interactions are described in the same way, which means their nature is common. However, this conclusion is only theoretical; it has not yet been possible to verify it experimentally.

Important role conservation laws played a 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, etc.

Known four types of interactions between elementary particles: strong , electromagnetic , weak And gravitational (they are listed in descending order of intensity). The intensity of interaction is usually characterized by the so-called interaction constant α, which is a dimensionless parameter, determining the probability of processes, caused by this type of interaction. For electromagnetic interaction constant:

Where E– energy of interaction of two electrons located at a distance λ. Hence,

.

Then the characteristic relation has the form:

.

The electromagnetic interaction constant is a dimensionless quantity:

.

The constants of other types of interactions are determined relative to the value of the electromagnetic interaction constant.

The ratio of the constants gives the relative intensity of the corresponding interactions.

Strong interaction. This type of interaction ensures the connection of nucleons in the nucleus. The strong interaction constant is on the order of 1–10. The greatest distance at which the strong interaction occurs (range of action) is approximately m.

Electromagnetic interaction. The interaction constant is (fine structure constant). The range is not limited ().

Weak interaction. This interaction is responsible for all types of nuclear beta decay (including e- captures), for the decays of elementary particles, as well as for all processes of interaction of the neutron with matter. The interaction constant is equal to a value of the order of 10 –10 – . The weak interaction, like the strong one, is short-range.

Gravitational interaction. The interaction constant has a value of order . The range is not limited (). Gravitational interaction is universal; all elementary particles without exception are subject to it. However, in the processes of the microworld, gravitational interaction does not play a significant role. In table 1 shows the values ​​of the constant different types interactions, as well as the average lifetime of particles decaying due to this type of interaction (decay time).

Table 1