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The energy in the clouds is dark. What are the cosmological models of the Universe? The formation of the modern cosmological model of the universe in brief

In classical science there was a theory of the steady state of the Universe, according to which the Universe has always been almost the same as it is now. Astronomy was static: the movement of planets and comets was studied, stars were described, their classification was created, which was, of course, very important. But the question of the evolution of the Universe was not raised. According to Newton's classical cosmology, space and time are homogeneous and isotropic, absolute and infinite. The Universe is stationary; specific cosmic systems can change, but not the world as a whole.

However, the recognition of the infinity of the Universe led to two paradoxes: gravitational and photometric. The essence gravitational paradox is that if the Universe is infinite and there is an infinite number of celestial bodies in it, then the gravitational force will be infinitely large, and the Universe should collapse, and not exist forever. Photometric paradox: if there are an infinite number of stars, and they are distributed evenly in space, then there must be an infinite luminosity of the sky. Against this background, even the Sun would seem to be a black spot, but it is not.

These cosmological paradoxes remained unsolvable until the twenties of the twentieth century, when relativistic cosmology replaced classical cosmology. Until this time, science did not have theoretically meaningful astronomical data indicating the large-scale evolution of matter. After the discovery of the phenomenon of natural radioactivity, the idea of the instability of cosmic matter in general, and the variability of the chemical composition of the Universe in particular, became inevitable.

The first relativistic cosmological model of the Universe was developed by A. Einstein in 1917. It was based on the equation of gravity introduced by Einstein in the general theory of relativity. In accordance with the ideas of classical astronomy about the stationarity of the Universe, he proceeded from the assumption that the properties of the Universe as a whole are unchanged in time (he considered the radius of curvature of space to be constant). Einstein even modified the general theory of relativity to satisfy this requirement, and introduced an additional cosmic repulsive force that should balance the mutual attraction of stars. Einstein's model was stationary in nature, since the metric of space was considered as independent of time. The existence of the Universe is infinite, i.e. it had neither beginning nor end, and space was limitless, but finite.

In 1922, Russian mathematician and geophysicist A.A. Friedman suggested a non-stationary solution by Einstein's equation of gravity, where the metric was considered as changing with time. He argued that the Universe cannot be stationary, it must either expand or contract. A. Einstein at first had a negative attitude towards Friedman’s work, but soon admitted the fallacy of his criticism.

Models of the Universe A.A. Friedman was soon confirmed in observations of the movements of distant galaxies - in the effect "red shift" discovered in 1929 by an American astronomer E. Hubble. Hubble discovered that in the spectra of distant galaxies, the spectral lines are shifted to the red end. Previously discovered Doppler effect said that when any source of vibration moves away from us, the frequency of vibrations perceived by us decreases, and the wavelength increases accordingly. When light is emitted, “reddening” occurs, i.e. the spectrum lines shift towards longer red wavelengths. If the redshift discovered by Hubble is understood as a result of the Doppler effect, then this means that galaxies are “moving away” from us at a speed that linearly depends on distance. Currently, removal velocities of the order of 100,000 km/sec have already been recorded for the most distant of the observed galaxies.

The recession of galaxies should not be imagined as some kind of ordinary movement in space that does not change with time. This is not the movement of objects in unchanged space, but an effect caused by new properties of space itself - the instability of its matter. So, neither the galaxies disperse in the remaining constant space, but the space itself expands (its metric changes) over time. For greater clarity, we can provide a two-dimensional model that clearly illustrates the Friedmann expansion. Let's take a rubber sphere and inflate it. Then all points on the surface will move away from each other, and from any point all the others will look like they are running away. Thus, the fact that all others move away from a given point does not at all indicate some kind of central, privileged position of this point.

The vast majority of modern cosmological theories are models of an evolving Universe. The most reasonable among them is considered to be based on the ideas of Friedman hot Big Bang model, which is also called standard, due to its almost universal recognition in the scientific community. According to this hypothesis, our Universe (Metagalaxy) 15-20 billion years ago arose as a result of the cosmic Big Bang, which was preceded by the so-called “singular” (special) state, when the matter of the visible Universe was “pulled to a point”, being in a super-dense state. Theoretical calculations show that in the original, singular, i.e. in a superdense state, the density of the matter of the Universe was 10 91 g/cm 3, and the radius was 10 -12 cm, which is close to the classical radius of the electron. But the idea of a singular state as matter “contracted to a point” with infinite values of physical quantities is, of course, an idealization, since science does not have the means to establish the dimensions (radius) of the visible Universe in its initial superdense state.

From the initial singular state, the Universe moved to expansion as a result of the Big Bang, which filled all space. As a result, every particle of matter rushed away from every other. Just one hundredth of a second after the explosion, the Universe had a temperature of 100,000 million degrees Kelvin. At such a temperature (above the temperature of the center of the hottest star), molecules, atoms, and even atomic nuclei cannot exist. The matter of the Universe was in the form of elementary particles, among which electrons, positrons, neutrinos, photons predominated, as well as protons and neutrons in relatively small quantities. The density of the matter of the Universe 0.01 s after the explosion was enormous - 4000 million times more than that of water. At the end of the first three minutes after the explosion, the temperature of the substance of the Universe, continuously decreasing, reached 1 billion degrees. At this temperature, atomic nuclei began to form, in particular, the nuclei of heavy hydrogen and helium. However, the matter of the Universe at the end of the first three minutes consisted mainly of photons, neutrinos and antineutrinos. Only after several hundred thousand years did atoms begin to form, mainly hydrogen and helium, forming the hydrogen-helium plasma.

The existence of the Universe as a hydrogen-helium plasma is confirmed by astronomy data. In 1965, the so-called "relic" radio emission of the Universe, which is the radiation of hot plasma, preserved from the time when there were no stars and galaxies.

Within the framework of Friedman's model, questions about the finitude and infinity of space and time, in a certain sense, become empirically verifiable. Friedman's non-stationary world, generally speaking, may have positive curvature (closed model) And negative curvature (open model), it can have one special time point- the beginning of time (expanding Universe). But it can also have infinitely many singular points. In this case, none of them can be considered the beginning of time, and their presence simply means that in the Universe, periods of expansion are replaced by periods of compression, when galaxies “compress” (the red shift changes to violet), the density again takes on an infinite value, and then begins to expand again (pulsating Universe).

The choice between the listed possibilities depends on the average density of matter and fields in the Universe. The future of our world depends on the relationship between the rate at which galaxies break apart and the force with which they attract each other. The force of gravity is determined by the average density of matter in the Universe, and it is known approximately. In relativistic cosmology, it is accepted that there is a critical value of the average density equal to approximately 10 -29 g/cm 3, i.e. 10 hydrogen atoms in one m3. If the actual average density of matter is less than the critical one, the space of the visible Universe has negative curvature, and the expansion of the Universe will continue indefinitely. According to this model, in the Universe, after 10 33 or more years, matter will turn into a rarefied gas of electrons, positrons, photons, and in the interval of 10 60 to 10 100 years, the so-called “black holes” will evaporate. If the average density of matter turns out to be greater than the critical one, the expansion of the Universe in the future will be replaced by compression, collapse, as a result of which a new singular state will arise. So, The only alternative for humanity in the Universe is “either to be burned in a closed Universe, or to be frozen in an open one.”

The standard model of an expanding universe has a number of theoretical problems and difficulties that prompt cosmologists to search for new concepts. One of the newest concepts is called the theory of an inflating universe, to emphasize the enormous speed of its expansion, incomparably higher than the rate of expansion characteristic of the standard model. The creator of this theory (otherwise called the inflationary model) is an American cosmologist A.G. Gus. The first version of this theory was presented by him in 1981. Huss's theory was created based on the application of the "Grand Unification" theory (i.e., a theory that describes in a unified way strong, weak and electromagnetic interactions) to descriptions of the very first moments of the evolution of the Universe. This theory allows us to resolve some problems that arise within the standard model, but gives rise to new ones. Currently, there are already three versions of the inflationary Universe model, differing in different approaches and views on the nature of the initial state from which the evolution of the Universe began. But all these hypotheses cannot be considered sufficiently substantiated, since the answer to the question about the original cause of the expansion of the Universe has not yet been found. However, two experimentally established provisions - expansion of the Universe and cosmic microwave background radiation- are very convincing arguments in favor of the Big Bang theory, which has now become generally accepted.

Cosmology studies the physical nature, structure and evolution of the Universe as a whole.

The concept of “Universe” means Space accessible to human observation.

Cosmology considers the most general properties of the entire region of space covered by observation. We call it the Metagalaxy. Our knowledge of the Metagalaxy is limited by the observation horizon. This horizon is determined by the fact that the speed of light is not instantaneous. Consequently, we can observe only those regions of the Universe from which light has managed to reach us by now. At the same time, we see objects not in their current state, but in the one in which they were at the moment of emission of light.

Models of the Universe, like any other, are built on the basis of theoretical concepts that currently exist in cosmology, physics, mathematics, chemistry and other related disciplines.

Several prerequisites for studying the Universe:

It is believed that the laws of the functioning of the world formulated by physics operate throughout the Universe;

It is believed that astronomers' observations also extend to the entire Universe;

It is believed that those conclusions are true that do not contradict the existence of man (anthropic principle).

The conclusions of cosmology are called models of the origin and development of the Universe.

Problems of the origin and structure of the Universe have occupied people since ancient times. Despite the high level of astronomical knowledge of the peoples of the ancient East, their views on the structure of the world were limited to direct visual sensations. Therefore, in Babylon there were ideas according to which the Earth has the appearance of a convex island surrounded by an ocean. There is supposedly a “kingdom of the dead” inside the Earth. The sky is a solid dome resting on the earth's surface and separating the "lower waters" (the ocean flowing around the earth's island) from the "upper" (rain) waters. Heavenly bodies are attached to this dome; gods seem to live above the sky. According to the ideas of the ancient Egyptians, the Universe looks like a large valley stretching from north to south, with Egypt in the center. The sky was likened to a large iron roof, which is supported on pillars, and stars are hung on it in the form of lamps.

Heraclides of Pontus and Eudoxus of Cnidus in the 4th century BC. argued that all bodies in the Universe rotate around their own axis and revolve around a common center (Earth) in spheres, the number of which in different cosmogonies varied from 30 to 55. The pinnacle of this picture of the world was the system of Claudius Ptolemy (2nd century AD). ).

The first scientifically based models of the Universe appeared after the discoveries of Copernicus, Galileo and Newton. First, R. Descartes put forward the idea of an evolutionary vortex Universe. According to his theory, all cosmic objects were formed from primary homogeneous matter as a result of vortex movements. The solar system, according to Descartes, is one of the vortices of cosmic matter. I. Kant developed the idea of an infinite Universe, formed under the influence of mechanical forces of attraction and repulsion, and tried to figure out the further fate of such a Universe. The great French mathematician Laplace described Kant's hypothesis mathematically.

I. Newton believed that the gravitating universe cannot be finite, since in this case all the stars that make it up will gather in the center under the influence of gravitational forces. He tried to explain the observed contradiction by the infinite number of stars in the Universe, as well as the infinity of the world in time and space. However, cosmology then encountered paradoxes.

1. Gravitational paradox: according to the Newtonian concept of gravity, an infinite Cosmos with a finite mass density should give an infinite force of attraction. Infinitely increasing gravity inevitably leads to infinite accelerations and infinite speeds of cosmic bodies. Consequently, the speed of bodies should increase with increasing distance between the bodies. But this does not happen, and then it turns out that the Universe cannot exist forever.

Solving this problem, I. Kant concluded that the Cosmos is not static. He called nebulae “world islands.” Lambert developed Kant's ideas. In his opinion, as the size of the islands increases, the distance between them also increases so that the total forces of the Cosmos remain finite. Then the paradox is resolved.

2. Photometric paradox (Olbers paradox): with an infinite Universe filled with an infinite number of stars, the sky should be uniformly bright. In fact, such an effect is not observed. In 1823, Olbers showed that dust clouds that absorb the light of more distant stars are themselves heated and should therefore emit light. This paradox resolved itself after the creation of a model of the expanding Universe.

Modern cosmology arose after the advent of Einstein’s general theory of relativity and therefore, in contrast to classical Galilean and Newtonian cosmology, it is called relativistic. The empirical basis for cosmology is optical and radar astronomical observations. The discovery of elementary particles and the study of their behavior in accelerators under conditions close to those that existed at the initial stages of the development of the Universe helped to understand what happened in the first moments of its evolution.

When Einstein worked on his general theory of relativity, the universe was not as it is now. The Metagalaxy and its expansion had not yet been discovered, so Einstein relied on the idea of a stationary Universe, which is evenly filled with Galaxies located at constant distances. Then the conclusion inevitably followed about the compression of the world under the influence of gravity. This result was in conflict with the conclusions of general relativity. In order not to conflict with the generally accepted picture of the world, Einstein arbitrarily introduced a new parameter into his equations - cosmic repulsion, which was characterized using the cosmological constant. A. Einstein assumed that the Universe is stationary, infinite, but not limitless. That is, it was thought of as a sphere, constantly increasing in volume, but having boundaries.

The only person who in 1922 believed in the correctness of the conclusions of General Relativity in relation to cosmological problems was the young Soviet physicist A.A. Friedman. He noticed that the theory of relativity implies non-stationary curvature of space.

As already mentioned in the first part of this work, Friedman’s model is based on the idea of an isotropic, homogeneous and non-stationary state of the Universe.

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

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.

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, based on 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 Friedmann-De Sitter-Lemaître calculations. 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).

where V is the speed of removal of galaxies, 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.

According to all three models of the evolution of the Universe, it had a starting point - a state characterized by the zero moment of time. The initial state of matter in it was a certain superdense state, which was characterized by instability, which led to its destruction. As a result, the matter of the Universe began to rapidly fly apart. We now know that for every billion years of life, the Universe expands by 5 - 10%. The most probable value of the Hubble constant of 80 km/sec gives us expansion times ranging from 13 to 17 billion years. In 2002, using a computer model of the current state of the Universe, results were obtained that gave us a lifetime of 13.7 billion years.

The mechanism of further evolution depends on the average density of matter in it. The critical density of a substance corresponds to a value of 3 hydrogen atoms per 1 m3 of space. However, the uncertainty in the current value of the density of matter in the Universe is very large. If we add up the masses of all currently known galaxies and interstellar gas, we get the value? = 0.3 atoms of H, that is, an order of magnitude less than the critical value. Accordingly, the Universe can expand forever.

However, there is the so-called hidden mass problem. Perhaps scientists do not know all the matter in the Universe. According to the latest data, the observed mass of the Universe is only 5-10% relative to the total mass of matter. If this result is confirmed, the evolution of the Universe may take a different path. Various cosmic objects claim to be the hidden mass carriers of the Universe. In our and other Galaxies there is a large amount of dark matter that cannot be seen directly, but whose existence we recognize by its gravitational effect on the orbits of stars. Moreover, galaxy clusters contain even larger amounts of such matter. This matter is a vacuum quantum mechanical structure. It accounts for 75% of the hidden mass.

Neutrinos, particles formed in the early stages of the development of the universe, can claim to be carriers of hidden mass. As has become known in the last 3 years, neutrinos still have mass, therefore, they can participate in the formation of gravitational interactions.

Candidates for the same role are some exotic objects, such as black holes - objects of point size and enormous mass, which are contained in the universe in large quantities, spatial string objects, etc.

According to a number of scientists, 20% of hidden matter is represented by “mirror particles”, which make up the “mirror world” invisible to us, which permeates our Universe. There are enough hypotheses on this matter, but their confirmation or refutation is a matter for the future.

If scientists’ assumptions about the unknown mass of matter in the Universe are confirmed, then its evolution may follow the path proposed in Friedman’s model, or according to the Pulsating Universe scheme. In this model, the Universe goes through an infinitely large number of oscillations, that is, at the end of each life cycle it returns to its original state with a point volume and an infinitely high density.

A very important problem of modern cosmology is the initial moments of the existence of our Universe. A successful attempt to solve this problem is associated with the name of the American astrophysicist Georgiy Antonovich Gamow, who in 1942 proposed the concept of the evolution of the Universe through the “Big Bang”. The main goal of the author of the concept was to, by considering nuclear reactions at the beginning of cosmological expansion, obtain the relationships between the amounts of various chemical elements and their isotopes observed in our time. The theory of the Hot Universe and the Big Bang makes certain predictions about the state of matter in the Universe in the first moments of its life.

1. Introduction.

2. Modern cosmological models of the Universe.

3. Stages of cosmic evolution.

4. Planets.

5. Comets.

6. Asteroids.

7. Stars.

8. Literature used.

Introduction.

Modern science views the megaworld, or space, as an interacting and developing system of all celestial bodies. The megaworld has a systemic organization in the form of planets and planetary systems that arise around stars, stars and stellar systems - galaxies; systems of galaxies - Metagalaxies.

Matter in the Universe is represented by condensed cosmic bodies and diffuse matter. Diffuse matter exists in the form of isolated atoms and molecules, as well as denser formations - giant clouds of dust and gas - gas-dust nebulae. A significant proportion of matter in
The Universe, along with diffuse formations, is occupied by matter in the form of radiation. Therefore, cosmic interstellar space is by no means empty.

Modern cosmological models of the Universe.

As indicated in the previous chapter, in classical science there was the so-called theory of the stationary state of the Universe, according to which
The universe has always been almost the same as it is now. Astronomy was static: the movements of planets and comets were studied, stars were described, their classifications were created, which was, of course, very important. But the question of the evolution of the Universe was not raised.

Classical Newtonian cosmology explicitly or implicitly accepted the following postulates:

The Universe is an all-existing, “world as a whole.” Cosmology cognizes the world as it exists in itself, regardless of the conditions of knowledge.

The space and time of the Universe are absolute; they do not depend on material objects and processes.

Space and time are metrically infinite.

Space and time are homogeneous and isotropic.

The Universe is stationary and does not undergo evolution. Specific space systems can change, but not the world as a whole.

Modern cosmological models of the Universe are based on A. Einstein's general theory of relativity, according to which the metric of space and time is determined by the distribution of gravitational masses in the Universe. Its properties as a whole are determined by the average density of matter and other specific physical factors. Modern relativistic cosmology builds models of the Universe, starting from the basic equation of gravity introduced by A. Einstein in the general theory of relativity.
Einstein's equation of gravity has not one, but many solutions, which explains the existence of many cosmological models of the Universe. The first model was developed by L. Einstein himself in 1917. He rejected the postulates of Newtonian cosmology about the absoluteness and infinity of space and time. In accordance with the cosmological model of the Universe
According to A. Einstein, world space is homogeneous and isotropic, matter on average is distributed evenly in it, the gravitational attraction of masses is compensated by the universal cosmological repulsion.

This model seemed quite satisfactory at the time, since it was consistent with all known facts. But new ideas put forward by A. Einstein stimulated further research, and soon the approach to the problem changed decisively.

In the same 1917, the Dutch astronomer W. de Sitter proposed another model, which was also a solution to the gravitational equations. This solution had the property that it would exist even in the case of "empty"
A universe free of matter. If masses appeared in such a Universe, then the solution ceased to be stationary: a kind of cosmic repulsion between the masses arose, tending to remove them from each other and dissolve the entire system. The tendency to expansion, according to W. de Sitter, became noticeable only at very large distances.

In 1922, Russian mathematician and geophysicist L.A. Friedman abandoned the postulate of classical cosmology about the stationarity of the Universe and gave the currently accepted solution to the cosmological problem.

Solving the equations of A.A. Friedman, allows three possibilities. If the average density of matter and radiation in the Universe is equal to a certain critical value, the world space turns out to be Euclidean and
The Universe is expanding indefinitely from its original point state.
If the density is less than critical, the space has geometry
Lobachevsky and also expands without limit. And finally, if the density is greater than the critical one, the space of the Universe turns out to be Riemannian; expansion at some stage is replaced by compression, which continues until the initial point state. According to modern data, the average density of matter in the Universe is less than critical, so the Lobachevsky model is considered more probable, i.e. spatially infinite expanding Universe. It is possible that some types of matter, which are of great importance for the average density, remain unaccounted for now. In this regard, it is still premature to draw final conclusions about the finiteness or infinity of the Universe.

The expansion of the Universe is considered a scientifically established fact. W. de Sitter was the first to search for data on the motion of spiral galaxies.
The discovery of the Doppler effect, which indicated the retreat of galaxies, gave impetus to further theoretical studies and new and improved measurements of the distances and velocities of spiral nebulae.

In 1929, American astronomer E.P. Hubble discovered the existence of a strange relationship between the distance and speed of galaxies: all galaxies are moving away from us, and with a speed that increases in proportion to the distance - the galaxy system is expanding.

But the fact that the Universe is currently expanding does not yet allow us to unambiguously resolve the issue in favor of one model or another.

Stages of cosmic evolution.

No matter how the question of the diversity of cosmological models is resolved, it is obvious that our Universe is expanding and evolving. The time of its evolution from its original state is estimated at approximately 20 billion years.

Perhaps a more appropriate analogy is not with an elementary particle, but with a supergene, which has a huge set of potential capabilities that are realized in the process of evolution. Modern science has put forward the so-called anthropic principle in cosmology. Its essence lies in the fact that life in the Universe is possible only for those values of universal constants, physical constants that actually occur. If the value of physical constants had even an insignificant deviation from existing ones, then the emergence of life would be impossible in principle. This means that already in the initial physical conditions of the existence of the Universe, the possibility of the emergence of life is inherent.

From the initial singular state, the Universe moved to expansion as a result of the Big Bang, which filled all space. As a result, every particle of matter rushed away from every other.

Just one hundredth of a second after the explosion, the Universe had a temperature of about 100,000 million degrees Kelvin. At this temperature
(above the temperature of the center of the hottest star), molecules, atoms and even atomic nuclei cannot exist. The matter of the Universe was in the form of elementary particles, among which electrons, positrons, neutrinos, photons predominated, as well as protons and neutrons in relatively small quantities. The density of the matter of the Universe 0.01 s after the explosion was enormous - 4,000 million times more than that of water

At the end of the first three minutes after the explosion, the temperature of the substance of the Universe, continuously decreasing, reached 1 billion degrees. At this still very high temperature, atomic nuclei began to form, in particular the nuclei of heavy hydrogen and helium. However, the matter of the Universe at the end of the first three minutes consisted mainly of photons, neutrinos and antineutrinos.

Planets.

Mercury, Venus, Mars, Jupiter and Saturn were known in ancient times. Uranus was discovered in 1781 by W. Herschel.
In 1846, the eighth planet, Neptune, was discovered. In 1930, American astronomer C. Tombaugh found a slowly moving star-shaped object on the negatives, which turned out to be a new, ninth planet. She was named Pluto. The search and discovery of satellites of the planets of the solar system continues to this day.
The planets Mercury, Venus, Earth and Mars are combined into one group of terrestrial planets. In their characteristics, they differ significantly from Jupiter, Saturn, Uranus and Neptune, which form a group of giant planets.

There are many interesting details visible on the disks of Mars, Jupiter and Saturn. Some of them belong to the surface of planets, others to their atmosphere (cloud formations)

When observing Mars during the opposition period, you can see the polar caps changing with the seasons, light continents, dark areas (seas) and periodic cloudiness.
The visible surface of Jupiter is cloudy. The most noticeable are dark reddish stripes, extended parallel to the equator.
The rings of Saturn are one of the most beautiful objects that can be observed through a telescope. The outer ring is separated from the middle ring by a dark gap called the Cassini gap. The middle ring is the brightest. It is also separated from the inner ring by a dark gap. The inner dark and translucent ring is called crepe. Its edge is blurred, the ring gradually disappears.
Experienced observers note the presence of foggy spots on the disk of Venus, the appearance of which varies from day to day. These spots can only be details of the cloud structure. The clouds on Venus form a powerful continuous layer that completely hides the surface of the planet from us.
Uranus cannot be observed with the naked eye. It is only visible through a telescope and appears as a small greenish disk.
Pluto, the most distant known planet in the solar system, looks like a star in a telescope. Its brightness experiences periodic changes, apparently associated with rotation (period of 6.4 days).

Spacecraft flights have brought more information for planetary research. However, ground-based observations of planets are important, if only for the reason that these devices do not yet allow long enough tracking of planets, necessary to study all kinds of changes (seasonal changes on Mars, the movement of clouds on Jupiter, etc.). Ground-based astronomical observations will provide interesting data for a long time to come.

Comets. Presumably, long-period comets come to us from the Oort Cloud, which contains a huge number of cometary nuclei. Bodies located on the outskirts of the Solar system, as a rule, consist of volatile substances (water, methane and other ices) that evaporate when approaching the Sun.

So far, more than 400 short-period comets have been discovered. Of these, about 200 were observed during more than one perihelion passage. Many of them belong to so-called families. For example, approximately 50 of the shortest-period comets (their complete revolution around the Sun lasts 3-10 years) form the Jupiter family. Slightly smaller in number are the families of Saturn, Uranus and Neptune (the latter, in particular, includes the famous Comet Halley).

Comets emerging from the depths of space look like nebulous objects with a tail stretching behind them, sometimes reaching a length of millions of kilometers. The comet's nucleus is a body of solid particles and ice shrouded in a hazy shell called a coma. A core with a diameter of several kilometers can have around it a coma 80 thousand km in diameter. Streams of sunlight knock gas particles out of the coma and throw them back, pulling them into a long smoky tail that drags behind her in space.

The brightness of comets depends very much on their distance from the Sun. Of all the comets, only a very small part comes close enough to the Sun and Earth to be seen with the naked eye. The most prominent ones are sometimes called "great comets."

Asteroids. To date, hundreds of thousands of asteroids have been discovered in the Solar System. As of September 26, 2009, there were 460,271 objects in the databases, 219,018 had precisely defined orbits and were assigned an official number. 15,361 of them at this time had officially approved names. It is estimated that the Solar System may contain from 1.1 to 1.9 million objects larger than 1 km. Most currently known asteroids are concentrated within the asteroid belt, located between the orbits of Mars and Jupiter.

Ceres, measuring approximately 975×909 km, was considered the largest asteroid in the Solar System, but since August 24, 2006 it received the status of a dwarf planet. The other two largest asteroids, 2 Pallas and 4 Vesta, have a diameter of ~500 km. 4 Vesta is the only object in the asteroid belt that can be observed with the naked eye. Asteroids moving in other orbits can also be observed during their passage near the Earth.

The total mass of all main belt asteroids is estimated at 3.0-3.6×10 21 kg, which is only about 4% of the mass of the Moon. The mass of Ceres is 0.95×10 21 kg, that is, about 32% of the total, and together with the three largest asteroids 4 Vesta (9%), 2 Pallas (7%), 10 Hygea (3%) - 51%, that is, absolute Most asteroids have negligible, by astronomical standards, mass.

Stars.

The most common objects in the Universe are stars. They arise like this: particles of a gas and dust cloud are slowly attracted to each other due to gravitational forces. The density of the cloud increases, and the resulting opaque sphere begins to rotate, capturing more and more particles from the surrounding space. The outer layers press on the inner ones, the pressure and temperature in the depths increase, according to the laws of thermodynamics, gradually reaching several million degrees. Then conditions are created in the core of the protostar for the reaction of thermonuclear fusion of helium from hydrogen. The fluxes of neutrinos released during such a reaction “notify the world” about this. As a result, a powerful stream of electromagnetic radiation presses on the outer layers of matter, counteracting gravitational compression. When the forces of radiation and gravity are balanced, the protostar becomes a star. To go through this stage of its evolution, a protostar needs from several million years (with a mass greater than the Sun) to several hundred million years (with a mass less than the Sun). Binary and multiple stars are widespread and can be said to be a common occurrence. They are formed nearby and rotate around a common center of mass. There are about 50% of all stars.

The chemical composition of stars, according to spectral analysis, on average is as follows: per 10,000 hydrogen atoms there are 1,000 helium atoms, 5 oxygen atoms, 2 nitrogen atoms, 1 carbon atom, and even fewer other elements. Due to high temperatures, atoms are ionized and are in a plasma state - a mixture of ions and electrons. Depending on the mass and chemical composition of the protostellar cloud, the young star falls on a certain section of the Hertzsprung-Russell diagram, which is a coordinate plane, along the vertical axis of which the luminosity of the star is plotted (the amount of energy emitted per unit time), and along the horizontal axis is the spectral class (star color depending on surface temperature). Moreover, blue stars are hotter than red ones. For convenience, the entire sequence of spectra is divided into several sections, or spectral classes. These spectral classes are designated by Latin letters: O - B - A - F - G - K - M - L - T The spectra of stars of two neighboring spectral classes are still very different from each other. Therefore, it was necessary to introduce a finer gradation - dividing the spectra within each spectral class into 10 subclasses. After this division, part of the sequence of spectra will look like this: ... - B9 - A0 - A1 - A2 - A3 - A4 - A5 - A6 - A7 - A8 - A9 - F0 - F1 - F2 - ... (the yellow Sun has a class G2, that is it is in the middle of the diagram, with a surface temperature of 6000 o). For convenience, the entire sequence of spectra is divided into several sections, or spectral classes. These spectral classes are designated by Latin letters: O - B - A - F - G - K - M - L - T The spectra of stars of two neighboring spectral classes are still very different from each other. Therefore, it was necessary to introduce a finer gradation - dividing the spectra within each spectral class into 10 subclasses. After this division, part of the sequence of spectra will look like this: ... - B9 - A0 - A1 - A2 - A3 - A4 - A5 - A6 - A7 - A8 - A9 - F0 - F1 - F2 - ... Most of the stars in the diagram are located along the main sequence - a smooth curve going from the upper left to the lower right corner of the diagram. As hydrogen is consumed, its mass changes and the star moves to the right along the main sequence. Stars with masses on the order of the Sun have been on the main sequence for 10-15 billion years (the Sun has been on it for about 4.5 billion years). Gradually, the energy in the center of the star runs out, and the pressure drops. Since it does not resist gravity, the core contracts, and the temperature there increases again, but reactions now occur only at the boundary of the core inside the star. The star swells, and its luminosity also increases. It descends from the main sequence to the upper right corner of the diagram, turning into a red giant with a radius greater than the radius of the orbit of Mars. When the temperature of the contracting helium (after all, the hydrogen has “burned out”) core of the red giant reaches 100-150 million degrees, the synthesis of carbon from helium begins. When this reaction exhausts itself, the outer layers are shed. The hot inner layers of the star end up on the surface, inflating the separated shell with radiation into the planetary nebula. After a few tens of thousands of years, the envelope dissipates, leaving behind a small, very hot, dense star. As it cools, it moves to the lower left corner of the diagram and turns into a white dwarf with a radius no greater than the radius of the Earth. White dwarfs are a pathetic end to the normal evolution of most stars.

Some stars flare up from time to time, shedding part of their shell and turning into new stars. At the same time, each time they lose about a hundredth of a percent of their mass. Less common are catastrophes that destroy a star - supernova explosions, in which more energy is emitted in a short time than from an entire galaxy. During the explosion, the star sheds its outer shell of gas (this is how it arose during the supernova explosion of 1054. The Crab nebula inside of which now contains a “stellar cinder” - the pulsar PSR0531, emitting even in the gamma-ray range). The last supernova occurred nearby in 1987, in the Large Magellanic Cloud, 60 kiloparsecs away. Neutrino radiation from this supernova was detected for the first time. If the mass of the star remaining after the catastrophe exceeds the solar mass by 2.5 times, a white dwarf cannot form. Gravity even destroys the structure of atoms. At the same time, according to the laws of physics, the rotation sharply accelerates.

In 1963, mysterious quasi-stellar objects (quasars) were discovered, which are compact formations the size of a star, but emitting like an entire galaxy. In their spectrum, against a continuous background of radiation, bright lines are visible, strongly red-shifted, which indicates that quasars are moving away from us at enormous speed (and are located very far from our galaxy). The nature of quasars has not been fully explained. Let us remember that, according to the hypothesis of the Russian physicist A. Kushelev, the “red shift” has a different nature, to explain which there is no need to imagine the Big Bang (although in this case quasars turn out to be one of the oldest objects in the Universe). And yet it is the explosive option that most researchers still adhere to.

Choose one correct answer.

1. The ancient Phoenicians were the first seafarers
4) discovered Asia

2. For the first time the term “geography” was used
2) Eratosthenes

3. Vasco da Gama was the first European
2) circled Africa, found a way to India

4. One of the first geographical maps was compiled by an ancient Greek scientist
3) Herodotus

5. Which traveler discovered America?
3) H. Columbus.

6. Which traveler made the first trip around the world?
3) F. Magellan

7. Which traveler discovered Antarctica?
4) F. Bellingshausen, M. Lazarev

8. Which traveler discovered the strait between Eurasia and America?
1) V. Bering

9. They took part in the development of northern Europe and Asia
1) S. Dezhnev
3) A. Nikitin

10. Match the discovery with the traveler’s name. Enter the resulting correspondence into the table.

Earth in the Universe. How did ancient people imagine the universe?

1. Formulate and write down a definition.
The Universe is outer space and everything that fills it: cosmic or celestial bodies, gas, dust.

2. What celestial bodies were known to the ancient Greeks?
Planets, Moon, Sun, stars.

3. Complete the sentences.
The great mathematician Pythagoras suggested that the Earth is spherical.
Aristarchus of Samos believed that the center of the Universe is not the Earth, but the Sun

4. Using additional sources of information, fill out the table.

Exploring the Universe: from Copernicus to the present day

1. Look at the pictures. How did the ideas about the world system of Ptolemy (a) and Copernicus (b) differ?

System of the world according to Ptolemy.
The center is the Earth, the Moon, the Sun, five (known at that time) planets, as well as the “sphere of fixed stars” move around the fixed center.
System of the world according to Copernicus.
The Earth revolves around the Sun. The center of the world is the Sun, around which all the planets move, rotating simultaneously around their axes. The stars are motionless. The stars form a sphere that limits the Universe.

2. What contribution did Giordano Bruno make to the development of the teachings of Nicolaus Copernicus? Write down the answer to the question in the form of a plan.
The Universe is infinite; it does not and cannot have a single center. The sun is the center of the solar system. But it itself is one of many stars around which planets orbit.

3. What discoveries did Galileo Galilei make? What instrument did he use in his research?
Telescope. I saw irregularities on the surface of the Moon, spots on the Sun, and discovered the satellites of Jupiter.

4. Complete the chain “Modern model of the Universe.”
Earth – solar system – galaxy – metagalaxy

5. Using additional sources of information, write a short report about the scientific activities of N. Copernicus, woman. Bruno, G. Galilee.

Neighbors of the Sun

1. What is the Solar System?
The sun and the celestial bodies moving around it.

2. List the cosmic bodies that are part of the Solar System.
Mercury, Venus, Earth, Mars, Jupiter, Sun, asteroids, stars, Jupiter, Saturn, Uranus, Neptune.

3. Complete the names of the planets of the solar system.