Formulated in the form of models of the origin and development of the Universe. This is due to the fact that in cosmology it is impossible to carry out reproducible experiments and derive any laws from them, as is done in other natural sciences. In addition, each cosmic phenomenon is unique. Therefore, cosmology operates with models. As new knowledge about the surrounding world accumulates, new cosmological models are refined and developed.

Classical cosmological model

Advances in cosmology and cosmogony in the 18th-19th centuries. culminated in the creation of a classical polycentric picture of the world, which became the initial stage in the development of scientific cosmology.

This model is quite simple and understandable.

1. The Universe is considered infinite in space and time, in other words, eternal.

2. The basic law governing the movement and development of celestial bodies is the law of universal gravitation.

3. Space is in no way connected with the bodies located in it, playing the passive role of a container for these bodies.

4. Time also does not depend on matter, being the universal duration of all natural phenomena and bodies.

5. If all bodies suddenly disappeared, space and time would remain unchanged. The number of stars, planets and star systems in the Universe is infinitely large. Each celestial body goes through a long life path. The dead, or rather extinguished, stars are being replaced by new, young luminaries.

Although the details of the origin and death of celestial bodies remained unclear, basically this model seemed harmonious and logically consistent. In this form, the classical polycentric model existed in science until the beginning of the 20th century.

However, this model of the universe had several flaws.

The law of universal gravitation explained the centripetal acceleration of the planets, but did not say where the desire of the planets, as well as any material bodies, to move uniformly and rectilinearly came from. To explain the inertial motion, it was necessary to assume the existence of a divine “first push” in it, which set all material bodies in motion. In addition, God's intervention was also allowed to correct the orbits of cosmic bodies.

The appearance within the framework of the classical model of the so-called cosmological paradoxes - photometric, gravitational, thermodynamic. The desire to resolve them also prompted scientists to search for new consistent models.

Thus, the classical polycentric model of the Universe was only partially scientific in nature; it could not provide a scientific explanation of the origin of the Universe and therefore was replaced by other models.

Relativistic model of the Universe

A new model of the Universe was created in 1917 by A. Einstein. It was based on the relativistic theory of gravity - the general theory of relativity. Einstein abandoned the postulates of absoluteness and infinity of space and time, but retained the principle of stationarity, the immutability of the Universe in time and its finitude in space. The properties of the Universe, according to Einstein, are determined by the distribution of gravitational masses in it. The Universe is limitless, but at the same time closed in space. According to this model, space is homogeneous and isotropic, i.e. has the same properties in all directions, matter is distributed evenly in it, time is infinite, and its flow does not affect the properties of the Universe. Based on his calculations, Einstein concluded that world space is a four-dimensional sphere.

At the same time, one should not imagine this model of the Universe in the form of an ordinary sphere. Spherical space is a sphere, but a four-dimensional sphere that cannot be visually represented. By analogy, we can conclude that the volume of such space is finite, just as the surface of any ball is finite; it can be expressed in a finite number of square centimeters. The surface of any four-dimensional sphere is also expressed in a finite number of cubic meters. Such a spherical space has no boundaries, and in this sense it is limitless. Flying in such space in one direction, we will eventually return to the starting point. But at the same time, a fly crawling along the surface of the ball will nowhere find boundaries or barriers that prohibit it from moving in any chosen direction. In this sense, the surface of any ball is limitless, although finite, i.e. limitlessness and infinity are different concepts.

So, from Einstein’s calculations it followed that our world is a four-dimensional sphere. The volume of such a Universe can be expressed, although very large, but still by a finite number of cubic meters. In principle, you can fly around the entire closed Universe, moving all the time in one direction. Such an imaginary journey is similar to earthly trips around the world. But the Universe, finite in volume, is at the same time limitless, just as the surface of any sphere has no boundaries. Einstein's Universe contains, although a large, but still finite number of stars and stellar systems, and therefore the photometric and gravitational paradoxes are not applicable to it. At the same time, the specter of heat death looms over Einstein’s Universe. Such a Universe, finite in space, inevitably comes to its end in time. Eternity is not inherent in it.

Thus, despite the novelty and even revolutionary nature of the ideas, Einstein in his cosmological theory was guided by the usual classical ideological attitude of the static nature of the world. He was more attracted to a harmonious and stable world than to a contradictory and unstable world.

Expanding Universe Model

Einstein's model of the Universe became the first cosmological model based on the conclusions of the general theory of relativity. This is due to the fact that it is gravity that determines the interaction of masses over large distances. Therefore, the theoretical core of modern cosmology is the theory of gravity - the general theory of relativity. Einstein assumed in his cosmological model the presence of a certain hypothetical repulsive force, which was supposed to ensure the stationarity and immutability of the Universe. However, the subsequent development of natural science made significant adjustments to this idea.

Five years later, in 1922, the Soviet physicist and mathematician A. Friedman, based on rigorous calculations, showed that Einstein’s Universe cannot be stationary and unchanging. At the same time, Friedman relied on the cosmological principle he formulated, which is based on two assumptions: the isotropy and homogeneity of the Universe. The isotropy of the Universe is understood as the absence of distinguished directions, the sameness of the Universe in all directions. The homogeneity of the Universe is understood as the sameness of all points of the Universe: we can conduct observations at any of them and everywhere we will see an isotropic Universe.

Friedman, based on the cosmological principle, proved that Einstein’s equations have other, non-stationary solutions, according to which the Universe can either expand or contract. At the same time, we were talking about expanding the space itself, i.e. about the increase in all the distances in the world. Friedman's universe resembled an inflating soap bubble, with both its radius and surface area continuously increasing.

Initially, the model of the expanding Universe was hypothetical and did not have empirical confirmation. However, in 1929, the American astronomer E. Hubble discovered the effect of “red shift” of spectral lines (shift of lines towards the red end of the spectrum). This was interpreted as a consequence of the Doppler effect - a change in oscillation frequency or wavelength due to the movement of the wave source and observer relative to each other. "Redshift" was explained as a consequence of galaxies moving away from each other at a rate that increases with distance. According to recent measurements, the increase in expansion rate is approximately 55 km/s for every million parsecs.

As a result of his observations, Hubble substantiated the idea that the Universe is a world of galaxies, that our Galaxy is not the only one in it, that there are many galaxies separated by enormous distances. At the same time, Hubble came to the conclusion that intergalactic distances do not remain constant, but increase. Thus, the concept of an expanding Universe appeared in natural science.

What kind of future awaits our Universe? Friedman proposed three models for the development of the Universe.

In the first model, the Universe expands slowly so that, due to the gravitational attraction between different galaxies, the expansion of the Universe slows down and eventually stops. After this, the Universe began to shrink. In this model, space bends, closing on itself, forming a sphere.

In the second model, the Universe expanded infinitely, and space was curved like the surface of a saddle and at the same time infinite.

In Friedman's third model, space is flat and also infinite.

Which of these three options follows the evolution of the Universe depends on the ratio of gravitational energy to the kinetic energy of the expanding matter.

If the kinetic energy of the expansion of matter prevails over the gravitational energy that prevents the expansion, then gravitational forces will not stop the expansion of galaxies, and the expansion of the Universe will be irreversible. This version of the dynamic model of the Universe is called the open Universe.

If gravitational interaction predominates, then the rate of expansion will slow down over time until it stops completely, after which the compression of matter will begin until the Universe returns to its original state of singularity (a point volume with an infinitely high density). This version of the model is called the oscillating, or closed, Universe.

In the limiting case, when the gravitational forces are exactly equal to the energy of the expansion of matter, the expansion will not stop, but its speed will tend to zero over time. Several tens of billions of years after the expansion of the Universe begins, a state will occur that can be called quasi-stationary. Theoretically, a pulsation of the Universe is also possible.

When E. Hubble showed that distant galaxies are moving away from each other at an ever-increasing speed, an unambiguous conclusion was made that our Universe is expanding. But an expanding Universe is a changing Universe, a world with all its history, having a beginning and an end. The Hubble constant allows us to estimate the time during which the process of expansion of the Universe continues. It turns out that it is no less than 10 billion and no more than 19 billion years. The most probable lifetime of the expanding Universe is considered to be 15 billion years. This is the approximate age of our Universe.

Scientist's opinion

There are other, even the most exotic, cosmological (theoretical) models based on the general theory of relativity. Here's what Cambridge University mathematics professor John Barrow says about cosmological models:

“The natural task of cosmology is to understand as best as possible the origin, history and structure of our own Universe. At the same time, general relativity, even without borrowing from other branches of physics, makes it possible to calculate an almost unlimited number of very different cosmological models. Of course, their selection is made on the basis of astronomical and astrophysical data, with the help of which it is possible not only to test various models for compliance with reality, but also to decide which of their components can be combined for the most adequate description of our world. This is how the current standard model of the Universe arose. So even for this reason alone, the historical diversity of cosmological models has been very useful.

But it's not only that. Many models were created when astronomers had not yet accumulated the wealth of data they have today. For example, the true degree of isotropy of the Universe was established thanks to space equipment only during the last two decades. It is clear that in the past space modelers had many fewer empirical constraints. In addition, it is possible that even models that are exotic by today’s standards will be useful in the future for describing those parts of the Universe that are not yet accessible to observation. And finally, the invention of cosmological models may simply stimulate the desire to find unknown solutions to the general relativity equations, and this is also a powerful incentive. In general, the abundance of such models is understandable and justified.

The recent union of cosmology and particle physics is justified in the same way. Its representatives consider the earliest stage of the life of the Universe as a natural laboratory, ideally suited for studying the basic symmetries of our world, which determine the laws of fundamental interactions. This union has already laid the foundation for a whole fan of fundamentally new and very deep cosmological models. There is no doubt that in the future it will bring no less fruitful results.”

In 1917, A. Einstein built a model of the Universe. In this model, a cosmological repulsive force called the lambda parameter was used to overcome the gravitational instability of the Universe. Later, Einstein would say that this was his gravest mistake, contrary to the spirit of the theory of relativity he created: the force of gravity in this theory is identified with the curvature of space-time. Einstein's Universe had the shape of a hypercylinder, the extent of which was determined by the total number and composition of forms of energy manifestation (matter, field, radiation, vacuum) in this cylinder. Time in this model is directed from the infinite past to the infinite future. Thus, here the amount of energy and mass of the Universe (matter, field, radiation, vacuum) is proportionally related to its spatial structure: limited in its shape, but of infinite radius and infinite in time.

Researchers who began to analyze this model noticed

to its extreme instability, similar to a coin standing on its edge, one side of which corresponds to the expanding Universe, the other to the closed one: when taking into account some physical parameters of the Universe, according to Einstein’s model, it turns out to be eternally expanding, when taking others into account - closed. For example, the Dutch astronomer W. de Sitter, having assumed that time is curved in the same way as space in Einstein’s model, received a model of the Universe in which time completely stops in very distant objects.

A. Freedman,fAndhIR And mathematician of Petrograd University, publishedV1922 G. article« ABOUTcurvaturespace."IN it presented the results of studies of the general theory of relativity, which did not exclude the mathematical possibility of the existence of three models of the Universe: the model of the Universe in Euclidean space ( TO = 0); model with a coefficient equal to ( K> 0) and a model in the Lobachevsky - Bolyai space ( TO< 0).

In his calculations, A. Friedman proceeded from the position that the value and

The radius of the Universe is proportional to the amount of energy, matter and other

forms of its manifestation in the Universe as a whole. The mathematical conclusions of A. Friedman denied the need to introduce a cosmological repulsive force, since the general theory of relativity did not exclude the possibility of the existence of a model of the Universe in which the process of its expansion corresponds to a compression process associated with an increase in the density and pressure of the energy-matter that makes up the Universe (matter, field, radiation , vacuum). A. Friedman's conclusions raised doubts among many scientists and A. Einstein himself. Although already in 1908, the mathematician G. Minkowski, having given a geometric interpretation of the special theory of relativity, received a model of the Universe in which the curvature coefficient is zero ( TO = 0), i.e., a model of the Universe in Euclidean space.

N. Lobachevsky, the founder of non-Euclidean geometry, measured the angles of a triangle between stars distant from the Earth and discovered that the sum of the angles of a triangle is 180°, i.e., space in space is Euclidean. The observed Euclidean space of the Universe is one of the mysteries of modern cosmology. It is currently believed that the density of matter

in the Universe is 0.1-0.2 parts of the critical density. The critical density is approximately 2·10 -29 g/cm 3 . Having reached critical density, the Universe will begin to contract.

A. Friedman's model with "TO > 0" is the expanding Universe from the original

her state to which she must return again. In this model, the concept of the age of the Universe appeared: the presence of a previous state relative to what was observed at a certain moment.

Assuming that the mass of the entire Universe is equal to 5 10 2 1 solar masses, A.

Friedman calculated that the observable Universe was in a compressed state

according to the model " K > 0" approximately 10-12 billion years ago. After this, it began to expand, but this expansion will not be endless and after a certain time the Universe will contract again. A. Friedman refused to discuss the physics of the initial, compressed state of the Universe, since the laws of the microworld were not clear at that time. A. Friedman's mathematical conclusions were repeatedly checked and rechecked not only by A. Einstein, but also by other scientists. After a certain time, A. Einstein, in response to A. Friedman’s letter, acknowledged the correctness of these decisions and called A. Friedman “the first scientist to take the path of constructing relativistic models of the Universe.” Unfortunately, A. Friedman died early. In his person, science has lost a talented scientist.

As noted above, neither A. Friedman nor A. Einstein knew the data on the fact of the “scattering” of galaxies obtained by the American astronomer V. Slifer (1875-1969) in 1912. By 1925, he measured the speed of movement of several tens galaxies. Therefore, the cosmological ideas of A. Friedman were discussed mainly in theoretical terms. NOalready V 1929

G.Americanastronomer E. Hubble (1889-1953) With with help telescope with instruments spectrumAline analysisfromwing tAto callingewasheduheffect

"reddisplacement." The light coming from the galaxies he observed

shifted to the red part of the visible light color spectrum. This meant

that the observed galaxies are moving away, “scattering” from the observer.

The redshift effect is a special case of the Doppler effect. The Austrian scientist K. Doppler (1803-1853) discovered it in 1824. When the wave source moves away relative to the device that records the waves, the wavelength increases and becomes shorter when approaching a stationary wave receiver. In the case of light waves, long waves of light correspond to the red segment of the light spectrum (red - violet), short ones - to the violet segment. The “redshift” effect was used by E. Hubble to measure the distances to galaxies and the speed of their removal: if the “redshift” from the galaxy A, For example, painwe V two times, how from galaxies IN, then the distance to the galaxy A twice as much as before the galaxy IN.

E. Hubble found that all observed galaxies are moving away in all directions of the celestial sphere at a speed proportional to the distance to them: Vr = Hr, Where r - distance to the observed galaxy, measured in parsecs (1 ps is approximately equal to 3.1 10 1 6 m), Vr - the speed of movement of the observed galaxy, Η - Hubble's constant, or the coefficient of proportionality between the speed of a galaxy and its distance

from the observer. The celestial sphere is a concept that is used to describe objects in the starry sky with the naked eye. The ancients considered the celestial sphere to be a reality, on the inner side of which the stars were fixed. Calculating the value of this quantity, which later became known as the Hubble constant, E. Hubble came to the conclusion that it was approximately 500 km/(s Mpc). In other words, a piece of space of one million parsecs increases by 500 km in one second.

Formula Vr= Hr allows us to consider both the removal of galaxies and the reverse situation, the movement towards a certain initial position, the beginning of the “scattering” of galaxies in time. The reciprocal of the Hubble constant has the dimension of time: t(time) = r/Vr = 1/H. When value N, which was mentioned above, E. Hubble obtained the time for the start of the “scattering” of galaxies to be equal to 3 billion years, which caused him to doubt the relativity of the correctness of the value he calculated. Using the “red shift” effect, E. Hubble reached the most distant galaxies known at that time: the further away the galaxy, the lower its brightness perceived by us. This allowed E. Hubble to say that the formula Vr = HR expresses the observed fact of the expansion of the Universe, which was discussed in A. Friedman’s model. The astronomical research of E. Hubble began to be considered by a number of scientists as experimental confirmation of the correctness of A. Friedman's model of a non-stationary, expanding Universe.

Already in the 1930s, some scientists expressed doubts about the data

E. Hubble. For example, P. Dirac put forward a hypothesis about the natural reddening of light quanta due to their quantum nature and interaction with the electromagnetic fields of outer space. Others pointed out the theoretical inconsistency of the Hubble constant: why should the value of the Hubble constant be the same at every moment in time in the evolution of the Universe? This stable constancy of the Hubble constant suggests that the laws of the Universe known to us, operating in the Megagalaxy, are mandatory for the entire Universe as a whole. Perhaps, as critics of the Hubble constant say, there are some other laws that the Hubble constant will not comply with.

For example, they say, light can “redden” due to the influence of the interstellar (ISM) and intergalactic (IGM) medium, which can lengthen the wavelength of its movement to the observer. Another issue that gave rise to discussions in connection with the research of E. Hubble was the question of the assumption of the possibility of galaxies moving at speeds exceeding the speed of light. If this is possible, then these galaxies may disappear from our observation, since from the general theory of relativity no signals can be transmitted faster than light. Nevertheless, most scientists believe that the observations of E. Hubble established the fact of the expansion of the Universe.

The fact of expansion of galaxies does not mean expansion within the galaxies themselves, since their structural certainty is ensured by the action of internal gravitational forces.

E. Hubble's observations contributed to further discussion of A. Friedman's models. BelgianmonkAndastronomerAND.Lemetr(VneRhowlhalf past)centurypaidpay attentionAtiononsleblowingcircumstance:galaxy recessionmeansextensionspace,hence,Vpast

wasdecreasevolumeAndPlrelationsVesociety. Lemaitre called the initial density of the substance a proto-atom with a density of 10 9 3 g/cm 3, from which God created the world. From this model it follows that the concept of density of matter can be used to determine the limits of applicability of the concepts of space and time. At a density of 10 9 3 g/cm 3 the concepts of time and space lose their usual physical meaning. This model brought attention to the physical state with super-dense and super-hot physical parameters. In addition, models have been proposed pulsatingUniverse: The universe expands and contracts, but never reaches extreme limits. Pulsating Universe models place great emphasis on measuring the energy-matter density of the Universe. When a critical density limit is reached, the Universe expands or contracts. As a result, the term appeared "singulIrnoe"(lat. singularus - a separate, single) state in which density and temperature take on an infinite value. This line of research faced the problem of the “hidden mass” of the Universe. The fact is that the observed mass of the Universe does not coincide with its mass calculated on the basis of theoretical models.

Model"Bigexplosion." Our compatriot G. Gamow (1904-1968)

worked at Petrograd University and was familiar with cosmological ideas

A. Friedman. In 1934, he was sent on a business trip to the USA, where he remained until the end of his life. Under the influence of the cosmological ideas of A. Friedman, G. Gamow became interested in two problems:

1) the relative abundance of chemical elements in the Universe and 2) their origin. By the end of the first half of the twentieth century. There was a lively discussion about these problems: where heavy chemical elements can be formed if hydrogen (1 1 H) and helium (4 H) are the most abundant chemical elements in the Universe. G. Gamow suggested that chemical elements trace their history back to the very beginning of the expansion of the Universe.

ModelG.GamovanAcalledmodel"Bigexplosion",nOsheIt has

AndotherName:"A-B-D-theory". This title indicates the initial letters of the authors of the article (Alpher, Bethe, Gamow), which was published in 1948 and contained a model of the “hot Universe”, but the main idea of ​​this article belonged to G. Gamow.

Briefly about the essence of this model:

1. The “original beginning” of the Universe, according to Friedman’s model, was represented by a super-dense and super-hot state.

2. This state arose as a result of the previous compression of the entire material and energy component of the Universe.

3. This condition corresponded to an extremely small volume.

4. Energy-matter, having reached a certain limit of density and temperature in this state, exploded, a Big Bang occurred, which Gamow called

"Cosmological Big Bang".

5. We are talking about an unusual explosion.

6. The Big Bang gave a certain speed of movement to all fragments of the original physical state before the Big Bang.

7. Since the initial state was superhot, the expansion should preserve the remnants of this temperature in all directions of the expanding Universe.

8. The value of this residual temperature should be approximately the same at all points of the Universe.

This phenomenon was called relict (ancient), background radiation.

1953 G. Gamow calculated the wave temperature of the cosmic microwave background radiation. Him

it turned out to be 10 K. CMB radiation is microwave electromagnetic radiation.

In 1964, American specialists A. Penzias and R. Wilson accidentally discovered relict radiation. Having installed the antennas of the new radio telescope, they could not get rid of interference in the 7.8 cm range. This interference and noise came from space, identical in size and in all directions. Measurements of this background radiation gave a temperature of less than 10 K.

Thus, G. Gamow’s hypothesis about relict, background radiation was confirmed. In his works on the temperature of background radiation, G. Gamow used A. Friedman's formula, which expresses the dependence of changes in radiation density over time. In parabolic ( K> 0) models of the Universe. Friedman considered a state where radiation dominates the matter of an infinitely expanding Universe.

According to Gamow's model, there were two eras in the development of the Universe: a) the predominance of radiation (physical field) over matter;

b) the predominance of matter over radiation. In the initial period, radiation predominated over matter, then there was a time when their ratio was equal, and a period when matter began to predominate over radiation. Gamow determined the boundary between these eras - 78 million years.

At the end of the twentieth century. measuring microscopic changes in background radiation, which was called pockmarkedbYu, have led a number of researchers to argue that these ripples represent a change in density substancesAndenergyGIIV as a result of the action of gravitational forces on early stages of development Universe.

Model "InflyatsiOnnoyUniverse".

The term "inflation" (lat. "inflation") is interpreted as swelling. Two researchers A. Guth and P. Seinhardt proposed this model. In this model, the evolution of the Universe is accompanied by a gigantic swelling of the quantum vacuum: in 10 -30 s the size of the Universe increases by 10 50 times. Inflation is an adiabatic process. It is associated with cooling and the emergence of differences between the weak, electromagnetic and strong interactions. An analogy for the inflation of the Universe can be, roughly speaking, represented by the sudden crystallization of a supercooled liquid. Initially, the inflationary phase was considered as the “rebirth” of the Universe after the Big Bang. Currently, inflation models use the concept AndnflatonnOthfields. This is a hypothetical field (from the word “inflation”), in which, thanks to random fluctuations, a homogeneous configuration of this field with a size of more than 10 -33 cm was formed. From it came the expansion and heating of the Universe in which we live.

The description of events in the Universe based on the “Inflationary Universe” model completely coincides with the description based on the Big Bang model, starting from 10 -30 from the expansion. The inflation phase means that the observable Universe is only part of the Universe. In the textbook by T. Ya. Dubnischeva “Concepts of modern natural science” the following course of events is proposed according to the model of the “Inflationary Universe”:

1) t - 10 - 4 5 s. At this point, after the expansion of the Universe began, its radius was approximately 10 -50 cm. This event is unusual from the point of view of modern physics. It is assumed that it is preceded by events generated by the quantum effects of the inflaton field. This time is less than the time of the “Planck era” - 10 - 4 3 s. But this does not confuse the supporters of this model, who carry out calculations with a time of 10 -50 s;

2) t - approximately from 10 -43 to 10 -35 s - the era of the “Great Unification” or the unification of all forces of physical interaction;

3) t - approximately from 10 - 3 5 to 10 -5 - the fast part of the inflationary phase,

when the diameter of the Universe increased by 10 5 0 times. We are talking about the emergence and formation of an electron-quark medium;

4) t- approximately from 10 -5 to 10 5 s, first the retention of quarks in hadrons occurs, and then the formation of nuclei of future atoms, from which matter is subsequently formed.

From this model it follows that after one second from the beginning of the expansion of the Universe, the process of the emergence of matter, its separation from photons of electromagnetic interaction and the formation of protosuperclusters and protogalaxies occurs. Heating occurs as a result of the emergence of particles and antiparticles interacting with each other. This process is called annihilation (lat. nihil - nothing or transformation into nothing). The authors of the model believe that annihilation is asymmetric towards the formation of ordinary particles that make up our Universe. Thus, the main idea of ​​the “Inflationary Universe” model is to exclude the concept of

The “Big Bang” as a special, unusual, exceptional state in the evolution of the Universe. However, an equally unusual condition appears in this model. This is the state configurations andnflaton field. The age of the Universe in these models is estimated at 10-15 billion years.

The “inflationary model” and the “Big Bang” model provide an explanation for the observed heterogeneity of the Universe (density of matter condensation). In particular, it is believed that during the inflation of the Universe, cosmic inhomogeneities-textures arose as embryos of aggregates of matter, which later grew into galaxies and their clusters. This is evidenced by what was recorded in 1992. the deviation of the temperature of the cosmic microwave background radiation from its average value of 2.7 K is approximately 0.00003 K. Both models speak of a hot expanding Universe, on average homogeneous and isotropic with respect to the cosmic microwave background radiation. In the latter case, we mean the fact that the cosmic microwave background radiation is almost identical in all parts of the observable Universe in all directions from the observer.

There are alternatives to the Big Bang and Inflationary models.

Universe": models of the "Stationary Universe", "Cold Universe" and

"Self-consistent cosmology".

Model"StationaryUniverse." This model was developed in 1948. It was based on the principle of “cosmological constancy” of the Universe: not only should there not be a single allocated place in the Universe, but also not a single moment in time should be allocated. The authors of this model are G. Bondi, T. Gold and F. Hoyle, the latter a well-known author of popular books on cosmology. In one of his works he wrote:

“Every cloud, galaxy, every star, every atom had a beginning, but not the entire Universe, the Universe is something more than its parts, although this conclusion may seem unexpected.” This model assumes the presence in the Universe of an internal source, a reservoir of energy that maintains the density of its energy-matter at a “constant level that prevents the compression of the Universe.” For example, F. Hoyle argued that if one atom appeared in one bucket of space every 10 million years, then the density of energy, matter and radiation in the Universe as a whole would be constant. This model does not explain how atoms of chemical elements, matter, etc. arose.

d. The discovery of relict radiation, background radiation, greatly undermined the theoretical foundations of this model.

Model« ColdUniverseth». The model was proposed in the sixties

years of the last century by the Soviet astrophysicist Ya. Zeldovich. Comparison

theoretical values ​​of radiation density and temperature according to the model

The “Big Bang” with radio astronomy data allowed Ya. Zeldovich to put forward a hypothesis according to which the initial physical state of the Universe was a cold proton-electron gas with an admixture of neutrinos: for each proton there is one electron and one neutrino. The discovery of cosmic microwave background radiation, confirming the hypothesis of an initial hot state in the evolution of the Universe, led Zeldovich to abandon his own model of the “Cold Universe”. However, the idea of ​​calculating the relationship between the number of different types of particles and the abundance of chemical elements in the Universe turned out to be fruitful. In particular, it was found that the energy-matter density in the Universe coincides with the density of the cosmic microwave background radiation.

Model"UniverseVatom." This model states that there is in fact not one, but many Universes. The “Universe in an Atom” model is based on the concept of a closed world according to A. Friedman. A closed world is a region of the Universe in which the forces of attraction between its components are equal to the energy of their total mass. In this case, the external dimensions of such a Universe can be microscopic. From the point of view of an external observer, it will be a microscopic object, but from the point of view of an observer inside this Universe, everything looks different: its galaxies, stars, etc. These objects are called fReadmonov. Academician A. A. Markov hypothesized that there could be an unlimited number of Friedmons and they could be completely open, that is, they have an entrance to their world and an exit (connection) with other worlds. It turns out that there are many Universes, or, as Corresponding Member of the USSR Academy of Sciences I. S. Shklovsky called it in one of his works, - Metaverse.

The idea of ​​a multiplicity of Universes was expressed by A. Guth, one of the authors of the inflationary model of the Universe. In an inflating Universe, the formation of “aneurysms” (a medical term meaning protrusion of the walls of blood vessels) from the mother Universe is possible. According to this author, the creation of the Universe is quite possible. To do this you need to compress 10 kg of substance

to a size smaller than one quadrillionth of an elementary particle.

SELF-TEST QUESTIONS

1. “Big Bang” model.

2. Astronomical research by E. Hubble and their role in development

modern cosmology.

3. Relict, background radiation.

4. Model “Inflationary Universe”.

Hypothesis of a multi-leaf model of the Universe

Preface by the site author: For the attention of readers of the site "Knowledge is Power" we offer fragments from the 29th chapter of Andrei Dmitrievich Sakharov's book "Memoirs". Academician Sakharov talks about the work in the field of cosmology, which he carried out after he began to actively engage in human rights activities - in particular, in Gorky’s exile. This material is of undoubted interest on the topic “The Universe”, discussed in this chapter of our site. We will get acquainted with the hypothesis of a multi-leaf model of the Universe and other problems of cosmology and physics. ...And, of course, let's remember our recent tragic past.

Academician Andrei Dmitrievich SAKHAROV (1921-1989).

In Moscow in the 70s and in Gorky, I continued my attempts to study physics and cosmology. During these years I was unable to put forward significantly new ideas, and I continued to develop those directions that were already presented in my works of the 60s (and described in the first part of this book). This is probably the lot of most scientists when they reach a certain age limit for them. However, I do not lose hope that perhaps something else will “shine” for me. At the same time, I must say that simply observing the scientific process, in which you yourself do not take part, but know what is what, brings deep inner joy. In this sense, I am “not greedy.”

In 1974, I did and in 1975 published a paper in which I developed the idea of ​​a zero Lagrangian of the gravitational field, as well as the calculation methods that I had used in previous works. At the same time, it turned out that I came to the method proposed many years ago by Vladimir Aleksandrovich Fok, and then by Julian Schwinger. However, my conclusion and the very path of construction, the methods were completely different. Unfortunately, I could not send my work to Fok - he died just then.

I subsequently discovered some errors in my article. It left unclarified the question of whether “induced gravity” (the modern term used instead of the term “zero Lagrangian”) gives the correct sign of the gravitational constant in any of the options that I considered.<...>

Three works - one published before my expulsion and two after my expulsion - are devoted to cosmological problems. In the first paper, I discuss the mechanisms of baryon asymmetry. Of some interest, perhaps, are general considerations about the kinetics of reactions leading to the baryon asymmetry of the Universe. However, specifically in this work, I reason within the framework of my old assumption about the existence of a “combined” conservation law (the sum of the numbers of quarks and leptons is conserved). I already wrote in the first part of my memoirs how I came to this idea and why I now consider it wrong. Overall, this part of the work seems to me unsuccessful. I like much more the part of the job where I write about multi-leaf model of the Universe . This is an assumption that the cosmological expansion of the Universe is replaced by compression, then a new expansion in such a way that the cycles of compression - expansion are repeated an infinite number of times. Such cosmological models have long attracted attention. Different authors called them "pulsating" or "oscillating" models of the Universe. I like the term better "multi-leaf model" . It seems more expressive, more in line with the emotional and philosophical meaning of the grandiose picture of the repeated repetition of the cycles of existence.

As long as conservation was assumed, the multileaf model encountered, however, an insurmountable difficulty following from one of the fundamental laws of nature - the second law of thermodynamics.

Retreat. In thermodynamics, a certain characteristic of the state of bodies is introduced, called. My dad once remembered an old popular science book called “The Queen of the World and Her Shadow.” (Unfortunately, I forgot who the author of this book is.) The queen is, of course, energy, and the shadow is entropy. Unlike energy, for which there is a conservation law, for entropy the second law of thermodynamics establishes the law of increase (more precisely, non-decrease). Processes in which the total entropy of bodies does not change are called (considered) reversible. An example of a reversible process is mechanical movement without friction. Reversible processes are an abstraction, a limiting case of irreversible processes accompanied by an increase in the total entropy of bodies (during friction, heat transfer, etc.). Mathematically, entropy is defined as a quantity whose increase is equal to the heat influx divided by the absolute temperature (it is additionally assumed - more precisely, it follows from general principles - that the entropy at absolute zero temperature and the entropy of vacuum are equal to zero).

Numerical example for clarity. A certain body having a temperature of 200 degrees transfers 400 calories during heat exchange to a second body having a temperature of 100 degrees. The entropy of the first body decreased by 400/200, i.e. by 2 units, and the entropy of the second body increased by 4 units; The total entropy increased by 2 units, in accordance with the requirement of the second law. Note that this result is a consequence of the fact that heat is transferred from a hotter body to a colder one.

An increase in total entropy during nonequilibrium processes ultimately leads to heating of the substance. Let's turn to cosmology, to multi-leaf models. If we assume that the number of baryons is fixed, then the entropy per baryon will increase indefinitely. The substance will heat up indefinitely with each cycle, i.e. conditions in the Universe will not be repeated!

The difficulty is eliminated if we abandon the assumption of conservation of baryon charge and consider, in accordance with my idea of ​​1966 and its subsequent development by many other authors, that the baryon charge arises from "entropy" (i.e. neutral hot matter) in the early stages of cosmological expansion of the Universe. In this case, the number of baryons formed is proportional to the entropy at each expansion-compression cycle, i.e. the conditions for the evolution of matter and the formation of structural forms can be approximately the same in each cycle.

I first coined the term "multi-leaf model" in a 1969 paper. In my recent articles I use the same term in a slightly different sense; I mention this here to avoid misunderstandings.

The first of the last three articles (1979) examined a model in which space is assumed to be flat on average. It is also assumed that Einstein's cosmological constant is not zero and is negative (although very small in absolute value). In this case, as the equations of Einstein's theory of gravity show, cosmological expansion inevitably gives way to compression. Moreover, each cycle completely repeats the previous one in terms of its average characteristics. It is important that the model is spatially flat. Along with flat geometry (Euclidean geometry), the following two works are also devoted to the consideration of Lobachevsky geometry and the geometry of a hypersphere (a three-dimensional analogue of a two-dimensional sphere). In these cases, however, another problem arises. An increase in entropy leads to an increase in the radius of the Universe at the corresponding moments of each cycle. Extrapolating into the past, we find that each given cycle could have been preceded by only a finite number of cycles.

In “standard” (one-sheet) cosmology there is a problem: what was there before the moment of maximum density? In multi-sheet cosmologies (except for the case of a spatially flat model), this problem cannot be avoided - the question is transferred to the moment of the beginning of the expansion of the first cycle. One can take the view that the beginning of the expansion of the first cycle or, in the case of the standard model, the only cycle is the Moment of the Creation of the World, and therefore the question of what happened before that lies beyond the scope of scientific research. However, perhaps, just as - or, in my opinion, more - justified and fruitful is the approach that allows for unlimited scientific research of the material world and space-time. At the same time, apparently, there is no place for the Act of Creation, but the basic religious concept of the divine meaning of Being is not affected by science and lies beyond its boundaries.

I am aware of two alternative hypotheses related to the problem under discussion. One of them, it seems to me, was first expressed by me in 1966 and was subject to a number of clarifications in subsequent works. This is the “turning of the arrow of time” hypothesis. It is closely related to the so-called reversibility problem.

As I already wrote, completely reversible processes do not exist in nature. Friction, heat transfer, light emission, chemical reactions, life processes are characterized by irreversibility, a striking difference between the past and the future. If we film some irreversible process and then play the movie in the opposite direction, we will see on the screen something that cannot happen in reality (for example, a flywheel rotating by inertia increases its rotation speed, and the bearings cool). Quantitatively, irreversibility is expressed in a monotonic increase in entropy. At the same time, the atoms, electrons, atomic nuclei, etc. that are part of all bodies. move according to the laws of mechanics (quantum, but this is unimportant here), which are completely reversible in time (in quantum field theory - with simultaneous CP reflection, see in the first part). The asymmetry of the two directions of time (the presence of the “arrow of time,” as they say) with the symmetry of the equations of motion has long attracted the attention of the creators of statistical mechanics. Discussion of this issue began in the last decades of the last century and was sometimes quite heated. The solution that more or less satisfied everyone was the hypothesis that the asymmetry was due to the initial conditions of motion and the position of all atoms and fields “in the infinitely distant past.” These initial conditions must be “random” in some well-defined sense.

As I suggested (in 1966 and more explicitly in 1980), in cosmological theories that have a designated point in time, these random initial conditions should be attributed not to the infinitely distant past (t -> - ∞), but to this selected point (t = 0).

Then automatically at this point the entropy has a minimum value, and when moving forward or backward from it in time, the entropy increases. This is what I called “the turning of the arrow of time.” Since when the arrow of time turns, all processes, including informational processes (including life processes), reverse, no paradoxes arise. The above ideas about the reversal of the arrow of time, as far as I know, have not received recognition in the scientific world. But they seem interesting to me.

The rotation of the arrow of time restores the symmetry of the two directions of time inherent in the equations of motion in the cosmological picture of the world!

In 1966-1967 I assumed that at the turning point of the arrow of time, CPT reflection occurs. This assumption was one of the starting points of my work on baryon asymmetry. Here I will present another hypothesis (Kirzhnitz, Linde, Guth, Turner and others had a hand; I only have the remark here that there is a turning of the arrow of time).

Modern theories assume that vacuum can exist in various states: stable, with an energy density equal to zero with great accuracy; and unstable, having a huge positive energy density (effective cosmological constant). The latter state is sometimes called a "false vacuum".

One of the solutions to the equations of general relativity for such theories is as follows. The Universe is closed, i.e. at each moment represents a “hypersphere” of finite volume (a hypersphere is a three-dimensional analogue of the two-dimensional surface of a sphere; a hypersphere can be imagined “embedded” in four-dimensional Euclidean space, just as a two-dimensional sphere is “embedded” in three-dimensional space). The radius of the hypersphere has a minimum finite value at some point in time (let us denote it t = 0) and increases with distance from this point, both forward and backward in time. Entropy is zero for a false vacuum (as for any vacuum in general) and when moving away from the point t = 0 forward or backward in time, it increases due to the decay of the false vacuum, turning into a stable state of true vacuum. Thus, at the point t = 0 the arrow of time rotates (but there is no cosmological CPT symmetry, which requires infinite compression at the point of reflection). Just as in the case of CPT symmetry, all conserved charges here are also equal to zero (for a trivial reason - at t = 0 there is a vacuum state). Therefore, in this case it is also necessary to assume the dynamic occurrence of the observed baryon asymmetry, caused by the violation of CP invariance.

An alternative hypothesis about the prehistory of the Universe is that in fact there is not one Universe or two (as - in some sense of the word - in the hypothesis of the turning of the arrow of time), but many radically different from each other and arising from some “primary” space (or its constituent particles; this may just be a different way of saying it). Other Universes and primary space, if it makes sense to talk about it, may, in particular, have, in comparison with “our” Universe, a different number of “macroscopic” spatial and temporal dimensions - coordinates (in our Universe - three spatial and one temporal dimension; in In other Universes, everything may be different!) I ask you not to pay special attention to the adjective “macroscopic” enclosed in quotation marks. It is associated with the “compactization” hypothesis, according to which most dimensions are compactified, i.e. closed on itself on a very small scale.

Structure of the “Mega-Universe”

It is assumed that there is no causal connection between different Universes. This is precisely what justifies their interpretation as separate Universes. I call this grandiose structure the “Mega Universe.” Several authors have discussed variations of such hypotheses. In particular, the hypothesis of multiple births of closed (approximately hyperspherical) Universes is defended in one of his works by Ya.B. Zeldovich.

The Mega Universe ideas are extremely interesting. Perhaps the truth lies precisely in this direction. For me, in some of these constructions there is, however, one ambiguity of a somewhat technical nature. It is quite acceptable to assume that conditions in different regions of space are completely different. But the laws of nature must necessarily be the same everywhere and always. Nature cannot be like the Queen in Carroll's Alice in Wonderland, who arbitrarily changed the rules of the game of croquet. Existence is not a game. My doubts relate to those hypotheses that allow a break in the continuity of space - time. Are such processes acceptable? Are they not a violation of the laws of nature at the breaking points, and not the “conditions of being”? I repeat, I am not sure that these are valid concerns; Maybe, again, as in the question of conservation of the number of fermions, I am starting from too narrow a point of view. In addition, hypotheses where the birth of Universes occurs without breaking continuity are quite conceivable.

The assumption that the spontaneous birth of many, and perhaps an infinite number of Universes differing in their parameters, and that the Universe surrounding us is distinguished among many worlds precisely by the condition for the emergence of life and intelligence, is called the “anthropic principle” (AP). Zeldovich writes that the first consideration of AP known to him in the context of an expanding Universe belongs to Idlis (1958). In the concept of a multi-leaf Universe, the anthropic principle can also play a role, but for the choice between successive cycles or their regions. This possibility is discussed in my work “Multiple Models of the Universe”. One of the difficulties of multi-sheet models is that the formation of “black holes” and their merging breaks the symmetry at the compression stage so much that it is completely unclear whether the conditions of the next cycle are suitable for the formation of highly organized structures. On the other hand, in sufficiently long cycles the processes of baryon decay and black hole evaporation occur, leading to the smoothing out of all density inhomogeneities. I assume that the combined action of these two mechanisms - the formation of black holes and the alignment of inhomogeneities - leads to a successive change of “smoother” and more “disturbed” cycles. Our cycle was supposed to be preceded by a “smooth” cycle during which no black holes were formed. To be specific, we can consider a closed Universe with a “false” vacuum at the turning point of the arrow of time. The cosmological constant in this model can be considered equal to zero; the change from expansion to compression occurs simply due to the mutual attraction of ordinary matter. The duration of the cycles increases due to the increase in entropy with each cycle and exceeds any given number (tends to infinity), so that the conditions for the decay of protons and the evaporation of “black holes” are met.

Multileaf models provide an answer to the so-called large number paradox (another possible explanation is the hypothesis of Guth et al., which involves a long "inflation" stage, see Chapter 18).

A planet on the outskirts of a distant globular star cluster. Artist © Don Dixon

Why is the total number of protons and photons in a Universe of finite volume so enormously large, although finite? And another form of this question, relating to the “open” version, is why is the number of particles so large in that region of Lobachevsky’s infinite world, the volume of which is of the order of A 3 (A is the radius of curvature)?

The answer given by the multileaf model is very simple. It is assumed that many cycles have already passed since t = 0; during each cycle, entropy (i.e., the number of photons) increased and, accordingly, an increasing baryon excess was generated in each cycle. The ratio of the number of baryons to the number of photons in each cycle is constant, since it is determined by the dynamics of the initial stages of the expansion of the Universe in a given cycle. The total number of cycles since t = 0 is just such that the observed number of photons and baryons is obtained. Since their number grows exponentially, for the required number of cycles we will not even get such a large value.

A by-product of my 1982 work is a formula for the probability of gravitational coalescence of black holes (the estimate in the book by Zeldovich and Novikov was used).

Another intriguing possibility, or rather a dream, is associated with multi-leaf models. Maybe a highly organized mind, developing billions of billions of years during a cycle, finds a way to transmit in encoded form some of the most valuable part of the information it has to its heirs in subsequent cycles, separated from this cycle in time by a period of a super-dense state?.. Analogy - transmission by living beings from generation to generation of genetic information, “compressed” and encoded in the chromosomes of the nucleus of a fertilized cell. This possibility, of course, is absolutely fantastic, and I did not dare to write about it in scientific articles, but on the pages of this book I gave myself free rein. But regardless of this dream, the hypothesis of a multi-leaf model of the Universe seems to me important in a philosophical worldview.

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8.2. Development of ideas about the Universe. Models of the Universe

Historically, ideas about the Universe have always developed within the framework of mental models of the Universe, starting with Ancient myths. In the mythology of almost any nation, a significant place is occupied by myths about the Universe - its origin, essence, structure, relationships and possible causes of the end.

In most ancient myths, the world (Universe) is not eternal, it was created by higher powers from some fundamental principle (substance), usually from water or from chaos. Time in ancient cosmogonic ideas is most often cyclical, i.e. the events of birth, existence and death of the Universe follow each other in a circle, like all objects in nature. The Universe is a single whole, all its elements are interconnected, the depth of these connections varies up to possible mutual transformations, events follow each other, replacing each other (winter and summer, day and night). This world order is opposed to chaos. The space of the world is limited. Higher powers (sometimes gods) act either as the creators of the Universe or as the guardians of the world order. The structure of the Universe in myths assumes multi-layeredness: along with the revealed (middle) world, there are the upper and lower worlds, the axis of the Universe (often in the form of a World Tree or Mountain), the center of the world - a place endowed with special sacred properties, there is a connection between the individual layers of the world. The existence of the world is conceived in a regressive manner - from the “golden age” to decline and death. Man in ancient myths can be an analogue of the entire Cosmos (the whole world is created from a gigantic creature similar to a giant man), which strengthens the connection between man and the Universe. In ancient models, man never takes center stage.

In the VI-V centuries. BC. The first natural philosophical models of the Universe are created, most developed in Ancient Greece. The ultimate concept in these models is the Cosmos as a single whole, beautiful and law-consistent. The question of how the world was formed is complemented by the question of what the world is made of and how it changes. The answers are no longer formulated in figurative, but in abstract, philosophical language. Time in models is most often still cyclical in nature, but space is finite. The substance acts as individual elements (water, air, fire - in the Milesian school and in Heraclitus), a mixture of elements, and a single, indivisible, motionless Cosmos (among the Eleatics), ontologized number (among the Pythagoreans), indivisible structural units - atoms that ensure the unity of the world - in Democritus. It is Democritus’ model of the Universe that is infinite in space. Natural philosophers determined the status of cosmic objects - stars and planets, the differences between them, their role and relative position in the Universe. In most models, movement plays a significant role. The Cosmos is built according to a single law - the Logos, and man is also subject to the same law - a microcosm, a reduced copy of the Cosmos.

The development of Pythagorean views, which geometrized the Cosmos and for the first time clearly presented it in the form of a sphere revolving around a central fire and surrounded by it, was embodied in Plato’s later dialogues. For many centuries, Aristotle’s model, mathematically processed by Ptolemy, was considered the logical pinnacle of antiquity’s views on the Cosmos. In a somewhat simplified form, this model, supported by the authority of the church, lasted about 2 thousand years. According to Aristotle, the Universe: o is a comprehensive whole, consisting of the totality of all perceived bodies; o one of a kind;

o spatially finite, limited to the extreme celestial sphere,

behind it “there is neither emptiness nor space”; o eternal, beginningless and endless in time. At the same time, the Earth is motionless and is located in the center of the Universe, the earthly and heavenly (supralunar) are absolutely opposite in their physical and chemical composition and the nature of movement.

In the 18th-19th centuries, during the Renaissance, natural philosophical models of the Universe re-emerged. They are characterized, on the one hand, by a return to the breadth and philosophical views of antiquity, and on the other, by strict logic and mathematics inherited from the Middle Ages. As a result of theoretical research, Nikolai Kuzansky, N. Copernicus, G. Bruno propose models of the Universe with infinite space, irreversible linear time, a heliocentric solar system and many worlds similar to it. G. Galileo, continuing this tradition, investigated the laws of motion - the property of inertia and was the first to consciously use mental models (constructs that later became the basis of theoretical physics), a mathematical language, which he considered the universal language of the Universe, a combination of empirical methods and a theoretical hypothesis that experience should confirm or refute, and, finally, astronomical observations using a telescope, which significantly expanded the capabilities of science.

G. Galileo, R. Descartes, I. Kepler laid the foundations of modern physical and cosmogonic ideas about the world, both on their basis and on the basis of the laws of mechanics discovered by Newton at the end of the 17th century. The first scientific cosmological model of the Universe was formed, called the classical Newtonian model. According to this model, the Universe: O is static (stationary), i.e. on average constant over time; O is homogeneous - all its points are equal; O is isotropic - all directions are equal; o is eternal and spatially infinite, and space and time are absolute - they do not depend on each other and on moving masses; O has a non-zero matter density; O has a structure that is completely understandable in the language of the existing system of physical knowledge, which means the infinite extrapolability of the laws of mechanics, the law of universal gravitation, which are the basic laws for the movement of all cosmic bodies.

In addition, the principle of long-range action is applicable in the Universe, i.e. instant signal propagation; The unity of the Universe is ensured by a single structure - the atomic structure of matter.

The empirical basis of this model was all the data obtained from astronomical observations; modern mathematical apparatus was used to process them. This construction was based on the determinism and materialism of the rationalistic philosophy of the New Age. Despite the contradictions that emerged (photometric and gravitational paradoxes - consequences of extrapolation of the model to infinity), ideological attractiveness and logical consistency, as well as heuristic potential, made the Newtonian model the only acceptable one for cosmologists until the 20th century.

The need to revise views on the Universe was prompted by numerous discoveries made in the 19th and 20th centuries: the presence of light pressure, the divisibility of the atom, the mass defect, the model of the structure of the atom, the non-planar geometries of Riemann and Lobachevsky, but only with the advent of the theory of relativity did a new quantum relativistic theory become possible model of the Universe.

From the equations of the special (STR, 1905) and general (GR, 1916) theories of relativity of A. Einstein, it follows that space and time are interconnected into a single metric and depend on moving matter: at speeds close to the speed of light, space is compressed, time is stretched, and near compact powerful masses space-time is curved, thereby the model of the Universe is geometrized. There were even attempts to imagine the entire Universe as a curved space-time, the nodes and defects of which were interpreted as masses.

Einstein, solving equations for the Universe, obtained a model that was limited in space and stationary. But to maintain stationarity, he needed to introduce an additional lambda term into the solution, which was not empirically supported by anything, and was equivalent in its action to a field opposing gravity at cosmological distances. However, in 1922-1924. A.A. Friedman proposed a different solution to these equations, from which it was possible to obtain three different models of the Universe depending on the density of matter, but all three models were non-stationary (evolving) - a model with expansion followed by compression, an oscillating model and a model with infinite expansion. At that time, the rejection of the stationarity of the Universe was a truly revolutionary step and was accepted by scientists with great difficulty, since it seemed to contradict all established scientific and philosophical views on nature, inevitably leading to creationism.

The first experimental confirmation of the nonstationarity of the Universe was obtained in 1929 - Hubble discovered a red shift in the spectra of distant galaxies, which, according to the Doppler effect, indicated the expansion of the Universe (not all cosmologists shared this interpretation at that time). In 1932-1933 Belgian theorist J. Lemaigre proposed a model of the Universe with a “hot beginning”, the so-called “Big Bang”. But back in the 1940s and 1950s. Alternative models were proposed (with the birth of particles from the c-field, from vacuum), preserving the stationary nature of the Universe.

In 1964, American scientists - astrophysicist A. Penzias and radio astronomer K. Wilson discovered homogeneous isotropic relict radiation, clearly indicating a “hot beginning” of the Universe. This model became dominant and was accepted by most cosmologists. However, this very point of “beginning”, the point of singularity, gave rise to many problems and disputes both about the mechanism of the “Big Bang” and because the behavior of the system (the Universe) near it could not be described within the framework of known scientific theories (infinitely high temperature and density had to be combined with infinitesimal sizes). In the 20th century Many models of the Universe have been put forward - from those that rejected the theory of relativity as a basis, to those that changed some factor in the basic model, for example, the “cellular structure of the Universe” or string theory. So, to remove the contradictions associated with the singularity, in 1980-1982. American astronomer P. Steinhart and Soviet astrophysicist A. Linde proposed a modification of the model of the expanding Universe - a model with an inflationary phase (the “inflating Universe” model), in which the first moments after the “Big Bang” received a new interpretation. This model continued to be refined later; it removed a number of significant problems and contradictions in cosmology. Research does not stop today: the hypothesis put forward by a group of Japanese scientists about the origin of primary magnetic fields is in good agreement with the model described above and allows us to hope to obtain new knowledge about the early stages of the existence of the Universe.

As an object of study, the Universe is too complex to be studied deductively; methods of extrapolation and modeling provide the opportunity to move forward in its knowledge. However, these methods require strict adherence to all procedures (from problem formulation, selection of parameters, degree of similarity between the model and the original, to interpretation of the results obtained), and even if all requirements are ideally fulfilled, the research results will be fundamentally probabilistic in nature.

Mathematization of knowledge, which significantly enhances the heuristic capabilities of many methods, is a general trend in science in the 20th century. Cosmology was no exception: a type of mental modeling arose - mathematical modeling, the method of mathematical hypothesis. Its essence is that equations are first solved, and then a physical interpretation of the resulting solutions is sought. This procedure, which is not typical for the science of the past, has enormous heuristic potential. It was this method that led Friedman to create a model of the expanding Universe; it was in this way that the positron was discovered and many more important discoveries were made in science at the end of the 20th century.

Computer models, including those used to model the Universe, are born of the development of computer technology. Based on them, models of the Universe with an inflationary phase have been improved; at the beginning of the 21st century. large amounts of information received from the space probe were processed, and a model of the development of the Universe was created, taking into account “dark matter” and “dark energy”.

Over time, the interpretation of many fundamental concepts has changed.

The physical vacuum is no longer understood as emptiness, not as ether, but as a complex state with a potential (virtual) content of matter and energy. At the same time, it was discovered that cosmic bodies and fields known to modern science make up an insignificant percentage of the mass of the Universe, and most of the mass is contained in “dark matter” and “dark energy” that indirectly reveal themselves. Research in recent years has shown that a significant part of this energy acts on the expansion, stretching, and tearing of the Universe, which can lead to a detectable acceleration of expansion. In this regard, the scenario for the possible future of the Universe requires revision. The category of time is one of the categories most discussed in cosmology. Most researchers attach an objective character to time, but according to the tradition coming from Augustine and I. Kant, time and space are forms of our contemplation, i.e. they are interpreted subjectively. Time is considered either as a parameter independent of any factors (a substantial concept coming from Democritus and underlying the classical Newtonian model of the Universe), or as a parameter associated with the movement of matter (a relational concept coming from Aristotle and becoming the basis of quantum -relativistic model of the Universe). The most common is the dynamic concept, which represents time as moving (they talk about the passage of time), but the opposite concept has also been put forward - static. Time in various models appears either cyclic, or finite, or infinite and linear. The essence of time is most often associated with causality. Problems such as the rationale for identifying the present moment of time, its direction, anisotropy, irreversibility, universality of time are discussed, i.e. Does time exist in all states of the Universe and is it always one-dimensional or can it have a different dimension and even not exist under certain conditions (for example, at a singularity point). The least developed question is about the peculiarities of time in complex systems: biological, mental, social.

When creating models of the Universe, some constants play a significant role - the gravitational constant, Planck's constant, the speed of light, the average density of matter, the number of dimensions of space-time. By studying these constants, some cosmologists came to the conclusion that with other values ​​of these constants, complex forms of matter would not exist in the Universe, not to mention life, and especially intelligence.

BIBLIOGRAPHICAL LIST

Evsyukov V.V. Myths about the Universe. Novosibirsk, 1988.

Latypov N.N., Beilin V.A., Vereshkov G.M. Vacuum, elementary particles and the Universe. M., 2001.

Linde A.D. Particle physics and inflationary cosmology. M., 1990.

Nadtochaev A.S. Philosophy and science in antiquity. M., 1990.

Novikov I.D. Evolution of the Universe. M., 1990.

Pavlenko A.N. European cosmology: foundations of the epistemological turn. M., 1997.

Hawking S. From the big bang to black holes. M., 1990.

Introduction. The structure of the Universe in Antiquity

3Heliocentric model of the Universe. Cosmological models of the Universe

1Cosmology

2Stationary model of the Universe

3Non-stationary model of the Universe

4Modern studies of cosmological models of the Universe. Nobel Prize for the discovery of the accelerated expansion of the Universe

5Dark matter

6Dark energy

Conclusion

Literature

Introduction

The Universe as a whole is the subject of a special astronomical science - cosmology, which has an ancient history. Its origins go back to antiquity. Cosmology has long been significantly influenced by the religious worldview, being not so much a subject of knowledge as a matter of faith.

Since the 19th century. Cosmological problems are not a matter of faith, but a subject of scientific knowledge. They are solved with the help of scientific concepts, ideas, theories, as well as instruments and instruments that allow us to understand what the structure of the universe is and how it was formed. In the 20th century Significant progress has been made in the scientific understanding of the nature and evolution of the Universe as a whole. Of course, the understanding of these problems is still far from complete, and, undoubtedly, the future will lead to new great revolutions in the currently accepted views on the picture of the universe. However, it is important to note that here we are dealing specifically with science, with rational knowledge, and not with beliefs and religious beliefs.

The relevance of this work is due, on the one hand, to the great interest in the structure of the Universe in modern science, on the other hand, to its insufficient development, as well as attention to the Universe in the modern world.

Object of study: Universe.

Subject of research: models of the structure of the Universe.

Purpose of the work: to consider modern cosmological models of the Universe.

To achieve this goal, it is necessary to solve the following tasks:

)Analyze the literature on the course of general physics and astronomy, in connection with the choice of subject of study.

)Trace the history of cosmological research.

)Consider modern cosmological models.

)Select illustrative material.

The course work consists of an introduction, three chapters, a conclusion and a bibliography. Chapter 1 is devoted to the history of the structure of the Universe, Chapter 2 examines cosmological models of the Universe, Chapter 3 opens modern studies of cosmological models, and in conclusion sums up the work done.

Chapter 1. The structure of the Universe in Antiquity

.1 Pyrocentric model of the Universe

The path to understanding the position of our planet and humanity living on it in the Universe was very difficult and sometimes very dramatic. In ancient times, it was natural to believe that the Earth was stationary, flat and at the center of the world. It seemed that the whole world was created for the sake of man. Such ideas are called anthropocentrism (from the Greek anthropos - man). Many ideas and thoughts that were later reflected in modern scientific ideas about nature, in particular in astronomy, originated in Ancient Greece, several centuries before our era. It is difficult to list the names of all the thinkers and their brilliant guesses. The outstanding mathematician Pythagoras (6th century BC) was convinced that “number rules the world.” It is believed that it was Pythagoras who first expressed the idea that the Earth, like all other celestial bodies, has a spherical shape and is located in the Universe without any support. The Pythagoreans proposed a pyrocentric model of the Universe, in which the stars, the Sun, the Moon and six planets revolve around a Central Fire (Hestia). To make the sacred number - ten - of spheres in total, the sixth planet was declared to be the Counter-Earth (Antichthon). Both the Sun and the Moon, according to this theory, shone with the reflected light of Hestia. This was the first mathematical system of the world - the rest of the ancient cosmogonists worked more with imagination than logic. The distances between the spheres of the luminaries among the Pythagoreans corresponded to musical intervals in the scale; when they rotate, the “music of the spheres” sounds, inaudible to us. The Pythagoreans believed that the Earth was spherical and rotating, which is why the change of day and night occurs. The Pythagoreans first arose the concept of ether. This is the uppermost, clean and transparent layer of air, the place of residence of the gods.

1.2 Geocentric model of the Universe

Another equally famous scientist of antiquity, Democritus - the founder of the concept of atoms, who lived 400 years BC - believed that the Sun is many times larger than the Earth, that the Moon itself does not glow, but only reflects sunlight, and the Milky Way consists of a huge number of stars. Summarize all the knowledge that had been accumulated by the 4th century. BC e., was able to the outstanding philosopher of the ancient world Aristotle (384-322 BC).

Rice. 1. Geocentric system of the world of Aristotle-Ptolemy.

His activities covered all natural sciences - information about the sky and Earth, about the patterns of movement of bodies, about animals and plants, etc. Aristotle's main merit as an encyclopedist scientist was the creation of a unified system of scientific knowledge. For almost two thousand years, his opinion on many issues was not questioned. According to Aristotle, everything heavy tends to the center of the Universe, where it accumulates and forms a spherical mass - the Earth. The planets are placed on special spheres that revolve around the Earth. Such a system of the world was called geocentric (from the Greek name for the Earth - Gaia). It was not by chance that Aristotle proposed to consider the Earth as the immovable center of the world. If the Earth moved, then, according to Aristotle’s fair opinion, a regular change in the relative positions of the stars on the celestial sphere would be noticeable. But none of the astronomers observed anything like this. Only at the beginning of the 19th century. The displacement of stars (parallax) resulting from the movement of the Earth around the Sun was finally discovered and measured. Many of Aristotle's generalizations were based on conclusions that could not be verified by experience at that time. Thus, he argued that the movement of a body cannot occur unless a force acts on it. As you know from your physics course, these ideas were refuted only in the 17th century. during the times of Galileo and Newton.

1.3 Heliocentric model of the Universe

Among ancient scientists, Aristarchus of Samos, who lived in the 3rd century, stands out for the boldness of his guesses. BC e. He was the first to determine the distance to the Moon and calculate the size of the Sun, which, according to his data, turned out to be more than 300 times larger than the Earth in volume. Probably, these data became one of the grounds for the conclusion that the Earth, along with other planets, moves around this largest body. Nowadays, Aristarchus of Samos has come to be called the “Copernicus of the ancient world.” This scientist introduced something new into the study of the stars. He believed that they were immeasurably further from the Earth than the Sun. For that era, this discovery was very important: from a cozy little home, the Universe was turning into an immense giant world. In this world, the Earth with its mountains and plains, with forests and fields, with seas and oceans became a tiny speck of dust, lost in a grandiose empty space. Unfortunately, the works of this remarkable scientist have practically not reached us, and for more than one and a half thousand years, humanity was sure that the Earth was the immovable center of the world. To a large extent, this was facilitated by the mathematical description of the visible movement of the luminaries, which was developed for the geocentric system of the world by one of the outstanding mathematicians of antiquity - Claudius Ptolemy in the 2nd century. AD The most difficult task was to explain the loop-like motion of the planets.

Ptolemy, in his famous work “Mathematical Treatise on Astronomy” (better known as “Almagest”) argued that each planet moves uniformly along an epicycle - a small circle, the center of which moves around the Earth along a deferent - a large circle. Thus, he was able to explain the special nature of the movement of the planets, which distinguished them from the Sun and Moon. The Ptolemaic system gave a purely kinematic description of the motion of the planets - the science of that time could not offer anything else. You have already seen that using a model of the celestial sphere to describe the movement of the Sun, Moon and stars allows you to carry out many calculations useful for practical purposes, although in reality such a sphere does not exist. The same is true for epicycles and deferents, on the basis of which the positions of the planets can be calculated with a certain degree of accuracy.

Rice. 2. Movement of the Earth and Mars.

However, over time, the requirements for the accuracy of these calculations constantly increased, and more and more new epicycles had to be added for each planet. All this complicated the Ptolemaic system, making it unnecessarily cumbersome and inconvenient for practical calculations. Nevertheless, the geocentric system remained unshakable for about 1000 years. After all, after the heyday of ancient culture in Europe, a long period began during which not a single significant discovery was made in astronomy and many other sciences. Only during the Renaissance did a rise in the development of sciences begin, in which astronomy became one of the leaders. In 1543, a book by the outstanding Polish scientist Nicolaus Copernicus (1473-1543) was published, in which he substantiated a new - heliocentric - system of the world. Copernicus showed that the daily motion of all the stars can be explained by the rotation of the Earth around its axis, and the loop-like motion of the planets by the fact that all of them, including the Earth, revolve around the Sun.

The figure shows the movement of the Earth and Mars during the period when, as it seems to us, the planet is describing a loop in the sky. The creation of the heliocentric system marked a new stage in the development of not only astronomy, but also all natural science. A particularly important role was played by Copernicus’s idea that behind the visible picture of occurring phenomena, which seems true to us, we must look for and find the essence of these phenomena, inaccessible to direct observation. The heliocentric system of the world, substantiated but not proven by Copernicus, was confirmed and developed in the works of such outstanding scientists as Galileo Galilei and Johannes Kepler.

Galileo (1564-1642), one of the first to point a telescope at the sky, interpreted the discoveries made as evidence in favor of the Copernican theory. Having discovered the change of phases of Venus, he came to the conclusion that such a sequence can only be observed if it revolves around the Sun.

Rice. 3. Heliocentric system of the world.

The four satellites of the planet Jupiter that he discovered also refuted the idea that the Earth is the only center in the world around which other bodies can rotate. Galileo not only saw mountains on the Moon, but even measured their height. Along with several other scientists, he also observed sunspots and noticed their movement across the solar disk. On this basis, he concluded that the Sun rotates and, therefore, has the kind of motion that Copernicus attributed to our planet. Thus, it was concluded that the Sun and Moon have a certain similarity with the Earth. Finally, observing many faint stars in and outside the Milky Way, inaccessible to the naked eye, Galileo concluded that the distances to the stars are different and that no “sphere of fixed stars” exists. All these discoveries became a new stage in understanding the position of the Earth in the Universe.

Chapter 2. Cosmological models of the Universe

.1 Cosmology

Translated from Greek, cosmology means “description of the world order.” This is a scientific discipline designed to find the most general laws of the movement of Matter and build an understanding of the Universe as a harmonious whole. Ideally, there should be no place for randomness in it (in cosmological theory), but all phenomena observed in the Cosmos should appear as manifestations of the general laws of motion of Matter. Thus, cosmology is the keys to understanding everything that happens in both the macrocosm and the microcosm.

Cosmology is a branch of astronomy and astrophysics that studies the origin, large-scale structure and evolution of the Universe. Data for cosmology are mainly obtained from astronomical observations. To interpret them, the general theory of relativity of A. Einstein (1915) is currently used. The creation of this theory and the carrying out of corresponding observations made it possible in the early 1920s to place cosmology among the exact sciences, whereas before that it was rather a field of philosophy. Now two cosmological schools have emerged: empiricists limit themselves to the interpretation of observational data, without extrapolating their models into unexplored areas; theorists try to explain the observable universe using some hypotheses selected for simplicity and elegance. The cosmological model of the Big Bang is now widely known, according to which the expansion of the Universe began some time ago from a very dense and hot state; The stationary model of the Universe is also discussed, in which it exists forever and has neither beginning nor end.

2.2 Stationary model of the Universe

The beginning of a new theory of the origin of the Universe was laid by the publication in 1916 of Albert Einstein's work “Fundamentals of the General Theory of Relativity.”

This work is the basis of the Relativistic Theory of Gravity, which, in turn, is the basis of modern cosmology. The general theory of relativity applies to all reference systems (and not just to those moving at a constant speed relative to each other) and looks mathematically much more complicated than the special one (which explains the eleven-year gap between their publication). It includes as a special case the special theory of relativity (and therefore Newton's laws). At the same time, the general theory of relativity goes much further than all its predecessors. In particular, it gives a new interpretation of gravity. The general theory of relativity makes the world four-dimensional: time is added to the three spatial dimensions. All four dimensions are inseparable, so we are no longer talking about the spatial distance between two objects, as is the case in the three-dimensional world, but about the space-time intervals between events, which combine their distance from each other - both in time and in space . That is, space and time are considered as a four-dimensional space-time continuum or, simply, space-time. Already in 1917, Einstein himself proposed a model of space, derived from his field equations, now known as the Einstein Model of the Universe. At its core, it was a stationary model. In order not to conflict with staticity, Einstein modified his theory by introducing the so-called cosmological constant into the equations. He introduced a new “anti-gravity” force, which, unlike other forces, was not generated by any source, but was embedded in the very structure of space-time. Einstein argued that space-time itself is always expanding and this expansion exactly balances the attraction of all other matter in the Universe, so that as a result the Universe turns out to be static.

Taking into account the cosmological constant, Einstein’s equations have the form:

Where ? - cosmological constant, g ab - metric tensor, R ab - Ricci tensor, R - scalar curvature, T ab - energy-momentum tensor, c - speed of light, G - Newton's gravitational constant.

“The universe, as depicted by Einstein's theory of relativity, is like an inflating soap bubble. She is not his insides, but a film. The surface of a bubble is two-dimensional, but the bubble of the Universe has four dimensions: three spatial and one temporal,” wrote the once prominent English physicist James Jeans. This modern scientist (he died in 1946) seemed to revive the old idea of ​​​​the followers of Plato and Pythagoras that everything around is pure mathematics, and the god who created this mathematical Universe was himself a great mathematician.

But Einstein was also a great mathematician. His formulas allow us to calculate the radius of this Universe. Since its curvature depends on the mass of the bodies that compose it, it is necessary to know the average density of matter. Astronomers have spent years studying the same small patches of sky and painstakingly counting the amount of matter in them. It turned out that the density is approximately 10 -30 g/cm 3 . If we substitute this figure into Einstein’s formulas, then, firstly, we get a positive value for curvature, that is, our Universe is closed! - and, secondly, its radius is 35 billion light years. This means that although the Universe is finite, it is huge - a ray of light, rushing along the Great Cosmic Circle, will return to the same point after 200 billion Earth years!

This is not the only paradox of Einstein's universe. It is not only finite, but limitless, it is also impermanent. Albert Einstein formulated his theory in the form of ten very complex, so-called nonlinear differential equations. However, not all scientists treated them as ten commandments, allowing only one interpretation. This is not surprising - after all, modern mathematics cannot accurately solve such equations, and there can be many approximate solutions.

2.3 Non-stationary model of the Universe

The first fundamentally new revolutionary cosmological consequences of the general theory of relativity were revealed by the outstanding Soviet mathematician and theoretical physicist Alexander Alexandrovich Friedman (1888-1925).

The fundamental equations of general relativity are Einstein's “world equations,” which describe the geometric properties, or metric, of four-dimensional curved spacetime.

Solving them allows, in principle, to construct a mathematical model of the Universe. The first such attempt was made by Einstein himself. Considering the radius of curvature of space to be constant (that is, based on the assumption that the Universe as a whole is stationary, which seemed most reasonable), he came to the conclusion that the Universe should be spatially finite and have the shape of a four-dimensional cylinder. In 1922-1924. Friedman criticized Einstein's conclusions. He showed the groundlessness of his initial postulate - about the stationarity, immutability in time of the Universe. Having analyzed the world equations, Friedman came to the conclusion that their solution under no circumstances can be unambiguous and cannot answer the question about the shape of the Universe, its finiteness or infinity.

Based on the opposite postulate - about the possible change in the radius of curvature of world space in time, Friedman found non-stationary solutions to the “world equations”. As an example of such solutions, he constructed three possible models of the Universe. In two of them, the radius of curvature of space increases monotonically, and the Universe expands (in one model - from a point, in the other - starting from a certain finite volume). The third model painted a picture of a pulsating Universe with a periodically changing radius of curvature.

Friedman's model is based on the idea of ​​an isotropic, homogeneous and non-stationary state of the Universe:

Ø Isotropy indicates that there are no distinct directional points in the Universe, that is, its properties do not depend on direction.

Ø The homogeneity of the Universe characterizes the distribution of matter in it. This uniform distribution of matter can be justified by counting the number of galaxies up to a given apparent magnitude. According to observations, the density of matter in the part of space we see is on average the same.

Ø Nonstationarity means that the Universe cannot be in a static, unchanging state, but must either expand or contract

In modern cosmology, these three statements are called cosmological postulates. The combination of these postulates is the fundamental cosmological principle. The cosmological principle directly follows from the postulates of the general theory of relativity. A. Friedman, on the basis of the postulates he put forward, created a model of the structure of the Universe in which all galaxies are moving away from each other. This model is similar to a uniformly inflating rubber ball, all points of which move away from each other. The distance between any two points increases, but neither of them can be called the center of expansion. Moreover, the greater the distance between the points, the faster they move away from each other. Friedman himself considered only one model of the structure of the Universe, in which space changes according to a parabolic law. That is, at first it will slowly expand, and then, under the influence of gravitational forces, the expansion will be replaced by compression to its original size. His followers showed that there are at least three models for which all three cosmological postulates are satisfied. The parabolic model of A. Friedman is one of the possible options. A slightly different solution to the problem was found by the Dutch astronomer W. de Sitter. The space of the Universe in his model is hyperbolic, that is, the expansion of the Universe occurs with increasing acceleration. The expansion rate is so high that gravitational influence cannot interfere with this process. He actually predicted the expansion of the Universe. The third option for the behavior of the Universe was calculated by the Belgian priest J. Lemaitre. In his model, the Universe will expand to infinity, but the rate of expansion will constantly decrease - this dependence is logarithmic. In this case, the expansion rate is just sufficient to avoid contraction to zero. In the first model, space is curved and closed on itself. It is a sphere, so its dimensions are finite. In the second model, space is curved differently, in the form of a hyperbolic paraboloid (or saddle), the space is infinite. In the third model with a critical expansion rate, space is flat, and therefore also infinite.

Initially, these hypotheses were perceived as an incident, including by A. Einstein. However, already in 1926, an epoch-making event in cosmology occurred, which confirmed the correctness of the calculations of Friedmann - De Sitter - Lemaitre. Such an event, which influenced the construction of all existing models of the Universe, was the work of the American astronomer Edwin P. Hubble. In 1929, while conducting observations with the largest telescope at that time, he found that light coming to Earth from distant galaxies is shifted towards the long-wavelength part of the spectrum. This phenomenon, called the “Redshift Effect,” is based on a principle discovered by the famous physicist K. Doppler. The Doppler effect says that in the spectrum of a radiation source approaching the observer, the spectral lines are shifted to the short-wave (violet) side, while in the spectrum of a source moving away from the observer, the spectral lines are shifted to the red (long-wave) side.

The redshift effect indicates that galaxies are moving away from the observer. With the exception of the famous Andromeda Nebula and several star systems closest to us, all other galaxies are moving away from us. Moreover, it turned out that the speed of expansion of galaxies is not the same in different parts of the Universe. The further away they are located, the faster they move away from us. In other words, the redshift value turned out to be proportional to the distance to the radiation source - this is the strict formulation of the open Hubble law. The natural relationship between the speed of removal of galaxies and the distance to them is described using the Hubble constant (N, km/sec per 1 megaparsec of distance).

V = Hr ,

where V is the speed of removal of galaxies, H is the Hubble constant, r is the distance between them.

The value of this constant has not yet been definitively established. Various scientists define it in the range of 80 ± 17 km/sec for each megaparsec of distance. The phenomenon of red shift was explained in the phenomenon of “galaxy recession”. In this regard, the problems of studying the expansion of the Universe and determining its age based on the duration of this expansion come to the fore.

Most modern cosmologists understand this expansion as the expansion of the entire conceivable and existing Universe... Unfortunately, his early death did not allow the brilliant theorist of the Universe A. A. Friedman, whose ideas have guided the thought of cosmologists for more than half a century, to take part in the further revolutionary development of the process himself updating the cosmological picture of the world. The experience of the history of the development of knowledge about the world suggests, however, that the modern relativistic cosmological picture of the world, being the result of extrapolation of knowledge about a limited part of the Universe to the entire conceivable “whole,” is inevitably inaccurate. Therefore, one can think that it rather reflects the properties of a limited part of the Universe (which can be called the Metagalaxy), and, perhaps, only one of the stages of its development (which relativistic cosmology allows and which can become clearer with clarification of the average density of matter in the Metagalaxy). At present, however, at this point the picture of the world remains uncertain.

Chapter 3. Modern research into cosmological models of the Universe

.1 Nobel Prize for the discovery of the accelerated expansion of the Universe

Modern cosmology is a complex, integrated and rapidly developing system of natural scientific (astronomy, physics, chemistry, etc.) and philosophical knowledge about the Universe as a whole, based on both observational data and theoretical conclusions related to the part of the universe covered by astronomical observations .

Quite recently, in the field of modern cosmology, a discovery was made that in the future could change our ideas about the origin and evolution of our Universe. Scientists who made a huge contribution to the development of this discovery were awarded the Nobel Prize for their work.

The Nobel Prize was awarded to the American Saul Perlmutter, the Australian Brian Schmidt and the American Adam Rees for their discovery of the accelerated expansion of the Universe.

In 1998, scientists discovered that the Universe is expanding at an accelerating rate. The discovery was made through the study of Type Ia supernovae. Supernovae are stars that flash brightly in the sky from time to time and then dim fairly quickly. Because of their unique properties, these stars are used as markers to determine how cosmological distances change over time. A supernova is a moment in the life of a massive star when it experiences a catastrophic explosion. Supernovae come in different types depending on the specific circumstances preceding the cataclysm. During observations, the type of flare is determined by the spectrum and shape of the light curve. Supernovae, designated Ia, occur in the thermonuclear explosion of a white dwarf whose mass has exceeded a threshold of ~1.4 solar masses, called the Chandrasekhar limit. As long as the white dwarf's mass is below a threshold value, the star's gravitational force is balanced by the pressure of the degenerate electron gas. But if in a close binary system matter flows onto it from a neighboring star, then at a certain moment the electron pressure turns out to be insufficient and the star explodes, and astronomers record another type Ia supernova explosion. Since the threshold mass and the reason why a white dwarf explodes are always the same, such supernovae at maximum brightness should have the same, and very high, luminosity and can serve as a “standard candle” for determining intergalactic distances. If we collect data on many such supernovae and compare the distances to them with the redshifts of the galaxies in which the explosions occurred, we can determine how the expansion rate of the Universe has changed in the past and select an appropriate cosmological model.

By studying distant supernovae, scientists have found that they are at least a quarter dimmer than theory predicts - meaning the stars are too far away. Having thus calculated the parameters of the expansion of the Universe, scientists have established that this process is accelerating.

3.2 Dark matter

Dark matter is similar to ordinary matter in the sense that it can clump together (the size of, say, a galaxy or cluster of galaxies) and participates in gravitational interactions in the same way as ordinary matter. Most likely, it consists of new particles that have not yet been discovered under terrestrial conditions.

In addition to cosmological data, measurements of the gravitational field in galaxy clusters and in galaxies support the existence of dark matter. There are several ways to measure the gravitational field in galaxy clusters, one of which is gravitational lensing, illustrated in Fig. 4.

Rice. 4. Gravitational lensing.

The gravitational field of the cluster bends the rays of light emitted by the galaxy located behind the cluster, i.e. the gravitational field acts like a lens. In this case, sometimes several images of this distant galaxy appear; on the left half of Fig. 7 they are blue. The bending of light depends on the distribution of mass in the cluster, regardless of which particles create that mass. The mass distribution restored in this way is shown on the right half of Fig. 7 in blue; it is clear that it is very different from the distribution of the luminous substance. The masses of galaxy clusters measured in this way are consistent with the fact that dark matter contributes about 25% of the total energy density in the Universe. Let us recall that this same number is obtained from comparing the theory of formation of structures (galaxies, clusters) with observations.

Dark matter also exists in galaxies. This again follows from measurements of the gravitational field, now in galaxies and their environs. The stronger the gravitational field, the faster the stars and clouds of gas rotate around the galaxy, so measuring rotation rates depending on the distance to the center of the galaxy allows us to reconstruct the distribution of mass in it.

What are dark matter particles? It is clear that these particles should not decay into other, lighter particles, otherwise they would decay during the existence of the Universe. This fact itself indicates that a new, not yet discovered conservation law operates in nature, prohibiting these particles from decaying. The analogy here is with the law of conservation of electric charge: an electron is the lightest particle with an electric charge, and that is why it does not decay into lighter particles (for example, neutrinos and photons). Further, dark matter particles interact extremely weakly with our matter, otherwise they would have already been discovered in earthly experiments. Then the area of ​​hypotheses begins. The most plausible (but far from the only!) hypothesis seems to be that dark matter particles are 100-1000 times heavier than a proton, and that their interaction with ordinary matter is comparable in intensity to the interaction of neutrinos. It is within the framework of this hypothesis that the modern density of dark matter finds a simple explanation: dark matter particles were intensively born and annihilated in the very early Universe at ultra-high temperatures (about 1015 degrees), and some of them have survived to this day. With the indicated parameters of these particles, their current number in the Universe turns out to be exactly what is needed.

Can we expect the discovery of dark matter particles in the near future under terrestrial conditions? Since today we do not know the nature of these particles, it is impossible to answer this question completely unambiguously. However, the outlook seems very optimistic.

There are several ways to search for dark matter particles. One of them is associated with experiments at future high-energy accelerators - colliders. If dark matter particles are really 100-1000 times heavier than a proton, then they will be born in collisions of ordinary particles accelerated at colliders to high energies (the energies achieved at existing colliders are not enough for this). The immediate prospects here are connected with the Large Hadron Collider (LHC), which is being built at the international center CERN near Geneva, which will produce colliding beams of protons with an energy of 7x7 Teraelectronvolts. It must be said that, according to today's popular hypotheses, dark matter particles are only one representative of a new family of elementary particles, so that along with the discovery of dark matter particles, one can hope for the discovery of a whole class of new particles and new interactions at accelerators. Cosmology suggests that the world of elementary particles is far from being exhausted by the “building blocks” known today!

Another way is to detect dark matter particles flying around us. There are by no means a small number of them: with a mass equal to 1000 times the mass of a proton, there should be 1000 of these particles here and now per cubic meter. The problem is that they interact extremely weakly with ordinary particles; the substance is transparent to them. However, dark matter particles occasionally collide with atomic nuclei, and these collisions can hopefully be detected. The search in this direction is carried out using a number of highly sensitive detectors placed deep underground, where the background from cosmic rays is sharply reduced.

Finally, another way is associated with recording the products of annihilation of dark matter particles among themselves. These particles should accumulate in the center of the Earth and in the center of the Sun (the matter is almost transparent to them, and they are able to fall into the Earth or the Sun). There they annihilate each other, and in the process other particles are formed, including neutrinos. These neutrinos pass freely through the thickness of the Earth or the Sun, and can be recorded by special installations - neutrino telescopes. One of these neutrino telescopes is located in the depths of Lake Baikal, the other (AMANDA) is located deep in the ice at the South Pole. There are other approaches to searching for dark matter particles, for example, searching for the products of their annihilation in the central region of our Galaxy. Time will tell which of all these paths will lead to success first, but in any case, the discovery of these new particles and the study of their properties will be the most important scientific achievement. These particles will tell us about the properties of the Universe 10-9 s (one billionth of a second!) after the Big Bang, when the temperature of the Universe was 1015 degrees, and dark matter particles intensively interacted with cosmic plasma.

3.3 Dark energy

Dark energy is a much stranger substance than dark matter. To begin with, it does not gather in clumps, but is evenly “spread” throughout the Universe. There is as much of it in galaxies and galaxy clusters as outside them. The most unusual thing is that dark energy, in a certain sense, experiences anti-gravity. We have already said that modern astronomical methods can not only measure the current rate of expansion of the Universe, but also determine how it has changed over time. So, astronomical observations indicate that today (and in the recent past) the Universe is expanding at an accelerating rate: the rate of expansion is increasing with time. In this sense, we can talk about antigravity: ordinary gravitational attraction would slow down the retreat of galaxies, but in our Universe, it turns out that the opposite is true.

heliocentric universe cosmological gravitational

Rice. 5. Illustration of dark energy.

This picture, generally speaking, does not contradict the general theory of relativity, but for this, dark energy must have a special property - negative pressure. This sharply distinguishes it from ordinary forms of matter. It is no exaggeration to say that the nature of dark energy is the main mystery of fundamental physics of the 21st century.

One of the candidates for the role of dark energy is vacuum. The vacuum energy density does not change as the Universe expands, and this means negative vacuum pressure. Another candidate is a new super-weak field that permeates the entire Universe; the term “quintessence” is used for it. There are other candidates, but in any case, dark energy is something completely unusual.

Another way to explain the accelerated expansion of the Universe is to assume that the laws of gravity themselves change over cosmological distances and cosmological times. This hypothesis is far from harmless: attempts to generalize the general theory of relativity in this direction face serious difficulties. Apparently, if such a generalization is possible at all, it will be associated with the idea of ​​the existence of additional dimensions of space, in addition to the three dimensions that we perceive in everyday experience.

Unfortunately, there are currently no visible ways to directly experimentally study dark energy under terrestrial conditions. This, of course, does not mean that new brilliant ideas in this direction cannot appear in the future, but today hopes for clarifying the nature of dark energy (or, more broadly, the reasons for the accelerated expansion of the Universe) are associated exclusively with astronomical observations and with obtaining new, more accurate cosmological data. We have to learn in detail exactly how the Universe expanded at a relatively late stage of its evolution, and this, hopefully, will allow us to make a choice between different hypotheses.

Conclusion

In this course work I examined cosmological models of the Universe. Having analyzed the literature on the course of general physics and astronomy, I traced the history of cosmological research, examined modern cosmological models of the Universe and selected illustrative material for the research topic. Having proved the relevance of the chosen topic, I summed up the work done.

Literature

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.Veselovsky I.N. Aristarchus of Samos - Copernicus of the ancient world. Historical and astronomical research. - M.: Nauka, 1961. Issue 7, p. 44.

.Efremov Yu.N., Pavlovskaya E.D. Determining the epoch of observation of the Almagest star catalog using the proper motions of stars. -- Historical and astronomical research. M.: Nauka, 1989, issue 18.

.I. G. Kolchinsky, A. A. Korsun, M. G. Rodriguez. Astronomers. 2nd ed., Kyiv, 1986.

.Karpenkov S.Kh. The concept of modern natural science: Textbook for universities / M.: Academic prospect, 2001.

.Klimishin I.A. Discovery of the Universe. - M.: Nauka, 1987.

.Matvievskaya G.P. As-Sufi. - Historical and astronomical research. M.: Nauka, 1983, issue 16, pp. 93--138.

.Pannekoek A. History of astronomy. - M.: Nauka, 1966.

.S. Shapiro, S. Tyukalski. Black holes, white dwarfs and neutron stars. Moscow, Mir, 1985

.Samygina S.I. “Concepts of modern natural science”/Rostov n/D: “Phoenix”, 1997.

.Physics of space: A small encyclopedia. M.: Sov. encyclopedia, 1986.

.Hawking S. A Brief History of Time: From the Big Bang to Black Holes. M.: Mir, 1990.

.E.V.Kononovich, V.I.Moroz. General astronomy course. Moscow, 2002.

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