Hypothesis of a multi-sheeted model of the universe. Model of the Universe. Stationary Universe Cosmological model of the early universe radiation era

Introduction

Since ancient times, human thought has been trying to solve the problem of the origin of our world, the emergence and further fate universe. This question belongs to eternal questions, and, probably, will never cease to excite the minds of people. IN different times were offered and various solutions the specified problem. According to one of them, the world was created and once began to exist; according to others, the world is eternal and has no beginning. There are also such points of view, according to which the universe periodically arises and is destroyed.

Origin and evolution of the universe

The Universe arose about 20 billion years ago from some dense and hot protomatter. Today, one can only guess what this progenitor substance of the Universe was like, how it was formed, what laws it obeyed, and what kind of processes led it to expand. There is a point of view that from the very beginning protomatter began to expand at a gigantic speed. At the initial stage, this dense substance scattered, scattered in all directions and was a homogeneous seething mixture of unstable particles constantly disintegrating during collisions. Cooling down and interacting over millions of years, all this mass of matter dispersed in space was concentrated into large and small gas formations, which over hundreds of millions of years, approaching and merging, turned into huge complexes. In turn, denser areas arose in them - subsequently, stars and even entire galaxies were formed there. As a result of gravitational instability, dense “protostellar formations” with masses close to the mass of the Sun can form in different zones of the formed galaxies. The compression process that has begun will accelerate under the influence of its own gravitational field. This process accompanies the free fall of cloud particles to its center - gravitational compression occurs. In the center of the cloud, a seal is formed, consisting of molecular hydrogen and helium. An increase in density and temperature in the center leads to the decay of molecules into atoms, ionization of atoms, and the formation of a dense core of a protostar. There is a hypothesis about the cyclic state of the Universe. Arising once from a superdense clot of matter. The universe, perhaps already in the first cycle, has generated within itself billions of star systems and planets. But then, inevitably, the Universe begins to strive towards the state from which the history of the cycle began, the red shift is replaced by purple, the radius of the Universe gradually decreases and, in the end, the substance of the Universe returns to its original superdense state, ruthlessly destroying all life on the way to it. And so it is repeated every time, in every cycle for eternity! By the beginning of the 1930s, it was believed that the main components of the Universe are galaxies, each of which, on average, consists of 100 billion stars. The Sun, together with the planetary system, enters our Galaxy, the bulk of the stars of which we observe in the form Milky Way. Except stars and planets. The galaxy contains a significant amount of rarefied gases and cosmic dust. Is the Universe finite or infinite, what is its geometry - these and many other questions are connected with the evolution of the Universe, in particular with the observed expansion. If, as is currently believed, the speed of the “expansion” of galaxies increases by 75 km / s for every million parsecs, then extrapolation to the past leads to a surprising result: about 10–20 billion years ago, the entire Universe was concentrated in a very small area . Many scientists believe that at that time the density of the universe was the same as atomic nucleus. Simply put, the Universe then was one giant "nuclear drop". For some reason, this "drop" came into an unstable state and exploded. We are now seeing the consequences of this explosion as a system of galaxies. The most serious blow to the inviolability of the Universe was inflicted by the results of measurements of the receding velocities of galaxies obtained by the famous American scientist E. Hubble. He found that any galaxy is moving away from us on average with a speed proportional to the distance to it. This discovery finally destroyed the idea of ​​a static, unshakable Universe that existed since the time of Aristotle, which, however, was already shaken in connection with the discovery of the evolution of stars. This means that galaxies are not at all cosmic lanterns suspended at equal distances from each other, and, moreover, since they are moving away, then at some time in the past they must have been closer to us. About 20 billion years ago, all galaxies, apparently, were concentrated in one point, from which the rapid expansion of the Universe to modern sizes began. But where is this point? Answer: nowhere and at the same time everywhere; it is impossible to specify its location, it would be contrary to the basic principle of cosmology. Another comparison may help to understand this statement. According to the general theory of relativity, the presence of matter in space leads to its curvature. In the presence of a sufficient amount of matter, it is possible to construct a model of curved space. Moving along the earth in one direction, we eventually, having traveled 40,000 km, must return to the starting point. In a curved universe, the same thing will happen, but after 40 billion light years; in addition, the "wind rose" is not limited to four parts of the world, but also includes up and down directions. So, the Universe resembles a balloon, on which galaxies are drawn and, like on a globe, parallels and meridians are plotted to determine the position of points; but in the case of the universe, it is necessary to use not two, but three dimensions to determine the position of galaxies. The expansion of the Universe resembles the process of inflating this balloon: mutual arrangement different objects on its surface does not change, there are no selected points on the ball. To estimate the total amount of matter in the universe, you just need to count all the galaxies around us. By doing so, we will get less matter than is necessary in order, according to Einstein, to close, " balloon» Universe. There are models of the open universe, the mathematical interpretation of which is just as simple, and which explain the lack of matter. On the other hand, it may turn out that in the Universe there is not only matter in the form of galaxies, but also an invisible substance in the amount necessary for the Universe to be closed; controversy on this issue has not yet subsided.

The creative role of the physical vacuum

Speaking the word "vacuum", we usually imagine an extremely rarefied medium, which is either studied in special laboratories or observed in outer space. However, vacuum is not emptiness, but something completely different: special, unobservable in Everyday life a state of matter called the physical vacuum.

Of course, there are no ordinary (real) particles in an empty volume, but quantum theory predicts the existence of many other particles, called virtual ones. Such particles are capable under certain conditions to turn into real ones.

The lifetime for particles with mass me is about

With. This value is very small and they speak not so much about "life" as about a short-term burst of life of very strange particles and the fields associated with them.

So, a sea of ​​unobservable particles, ready under certain conditions to become ordinary.

The state of physical vacuum can be characterized the smallest value the energy of quantum fields such as a scalar field that must exist in a vacuum. Corresponding to this field is the hypothetical Higgs particle (named after the scientist Higgs who proposed it), which is an example of a superheavy boson, whose mass, perhaps, is

times the mass of a proton. Such particles can be born at a temperature of K. There are projects of huge accelerators, where, by observing the interaction of particles, scientists hope to confirm the reality of the existence of Higgs.

One of the projects American engineers and physicists are planning to implement at the end of the century. It will be a very powerful colliding beam accelerator, and superconducting magnets will be used to reduce the energy consumption in the annular facility with a circumference of 84 km. The future accelerator is called the SSC superconducting supercollider.

One of amazing properties physical vacuum is due to the fact that it creates a negative pressure and, therefore, can be a source of repulsive forces in nature. This property plays an extremely important role in the "inflating universe" scenario.

Paradoxes of the Stationary Universe

In 1744 the Swiss astronomer Jean Philippe de Chezo discovered the photometric paradox associated with the alleged infinity of the universe. Its essence is as follows: if there are countless stars in an infinite universe, then in any direction the gaze of an earthly observer would certainly come across some star, and then the sky would have a brightness comparable to the brightness of the sun, which is not actually observed. In 1826, the German astronomer Heinrich Olbers independently reached the same conclusions. Since then, the photometric paradox has been called the Szezo-Olbers paradox. Scientists tried in various ways to eliminate this paradox, assuming the uneven arrangement of stars or the absorption of light by gas and dust interstellar clouds, as Szezo and Olbers tried to do. However, as was later shown, the gas and dust clouds must have heated up and themselves re-emitted the absorbed rays, and this fact did not allow avoiding the photometric paradox.

In 1895, the German astronomer Hugo Seeliger discovered the gravitational paradox, also related to the alleged infinity of the universe. Its essence is as follows: if there are countless evenly distributed stars (masses) in an infinite universe, then their gravitational force acting on any body becomes either infinitely large or indefinite (depending on the method of calculation), which is not observed. And in this case, attempts were made to avoid the gravitational paradox by assuming a different formula for the gravitational force in the law of gravity, or by assuming that the mass density in the universe is close to zero. But accurate observations of the movement of the planets of the solar system disproved these assumptions. The paradox remained in place.

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 the 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 reasons end .

In most ancient myths, the world (the Universe) is not eternal, it was created by higher forces from some fundamental principle (substance), usually from water or chaos. Time in ancient cosmogonic ideas is most often cyclical, i.e. the events of the 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 is different 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 implies a layering: along with the manifest (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 regressively - from the "golden age" to decline and death. A man in ancient myths can be an analogue of the entire Cosmos (the whole world is created from a giant creature similar to a giant man), which strengthens the connection between man and the Universe. In ancient models, man never occupies a central place.

In the VI-V centuries. BC. the first natural-philosophical models of the Universe are being created, the most developed in Ancient Greece. The limiting concept in these models is the Cosmos as a whole, beautiful and law-like. The question of how the world was formed is complemented by the question of what the world is made of, how it changes. The answers are no longer formulated in figurative, but in abstract, philosophical language. Time in models most often still has a cyclical character, but space is finite. As a substance, both separate elements act (water, air, fire - in the Miletus school and Heraclitus), a mixture of elements, and a single, indivisible motionless Cosmos (among the Eleatics), an 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 space 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, geometrizing the Cosmos and for the first time clearly presenting it as a sphere revolving around the central fire and surrounded by it, was embodied in Plato's later dialogues. The logical peak of the views of antiquity on the Cosmos for many centuries was considered the model of Aristotle, mathematically processed by Ptolemy. In a somewhat simplified form, this model, supported by the authority of the church, existed for 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 by the extreme celestial sphere,

behind it "there is no emptiness, no place"; 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 terrestrial and celestial (supralunar) are absolutely opposite in their physical and chemical composition and the nature of movement.

In the Х1У-Х>/1 centuries, during the Renaissance, natural-philosophical models of the Universe arose again. They are characterized, on the one hand, by a return to the breadth and philosophical views of antiquity, and, on the other hand, by strict logic and mathematics inherited from the Middle Ages. As a result of theoretical research, Nikolai Kuzansky, N. Copernicus, J. Bruno offer models of the Universe with infinite space, irreversible linear time, heliocentric solar system and many worlds like it. G. Galileo, continuing this tradition, investigated the laws of motion - a property of inertia and was the first to consciously use mental models (constructs that later became the basis of theoretical physics), the 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 with a telescope, which greatly expanded the possibilities of science.

G. Galileo, R. Descartes, I. Kepler laid the foundations of modern physical and cosmogonic ideas about the world, and 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, called the classical Newtonian, was formed. According to this model, the Universe: O is static (stationary), i.e. on average, unchanged over time; O is homogeneous - all its points are equal; O isotropic - all directions are equal; o eternal and spatially infinite, moreover, space and time are absolute - they do not depend on each other and on moving masses; O has a non-zero density of matter; O has a structure that is fully comprehended in the language of the available system of physical knowledge, which means the infinite extrapolation of the laws of mechanics, the law of universal gravitation, which are the basic laws for the motion 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 in astronomical observations, for their processing a modern mathematical apparatus was used. This construction relied on the determinism and materialism of the rationalist philosophy of modern times. Despite the revealed contradictions (the photometric and gravitational paradoxes are the consequences of extrapolating the model to infinity), the worldview attractiveness and logical consistency, as well as the heuristic potential, made the Newtonian model the only acceptable one for cosmologists until the 20th century.

Numerous discoveries made in the 19th and 20th centuries prompted the need to revise the views on the Universe: 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 special (SRT, 1905) and general (GR, 1916) theory of relativity by A. Einstein, it follows that space and time are interconnected into a single metric, depend on moving matter: at speeds close to the speed of light, space is compressed, time is stretched, and near powerful compact masses, space-time is curved, thereby the model of the Universe is geometrized. There were even attempts to represent the entire Universe as a curved space-time, the knots and defects of which were interpreted as masses.

Einstein, solving equations for the Universe, received a model limited in space and stationary. But to maintain stationarity, he needed to introduce an additional lambda term into the solution, empirically unsupported by anything, equivalent in its action to a field that opposes gravity at cosmological distances. However, in 1922-1924. A.A. Friedman proposed a different solution to these equations, from which the possibility of obtaining three different models of the Universe depending on the density of matter followed, but all three models were non-stationary (evolving) - a model with expansion, alternating 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 perceived by scientists with great difficulty, since it seemed contrary to all established scientific and philosophical views on nature, inevitably leading to creationism.

The first experimental confirmation of the non-stationarity of the Universe was obtained in 1929 - Hubble discovered the redshift in the spectra of distant galaxies, which, according to the Doppler effect, indicated the expansion of the Universe (not all cosmologists shared this interpretation then). In 1932-1933 The Belgian theorist J. Lemegre proposed a model of the Universe with a "hot start", 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) that preserve the stationarity of the Universe.

In 1964, American scientists, astrophysicist A. Penzias and radio astronomer K. Wilson, discovered homogeneous isotropic cosmic microwave background radiation, clearly indicating the "hot beginning" of the Universe. This model has become dominant and has been recognized by most cosmologists. However, this “beginning” point itself, the singularity point, gave rise to many problems and disputes both about the “Big Bang” mechanism and because the behavior of the system (the Universe) near it could not be described within the framework of known scientific theories(infinitely large temperature and density had to be combined with infinitely small dimensions). In the XX 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 "honeycomb structure of the universe" or string theory. So, to remove the contradictions associated with the singularity, in 1980-1982. the American astronomer P. Steinhart and the Soviet astrophysicist A. Linde proposed a modification of the expanding Universe model - 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 even 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 gain new knowledge about the early stages of the existence of the Universe.

As an object of study, the Universe is too complex to study it deductively; it is precisely the methods of extrapolation and modeling that make it possible to move forward in its knowledge. However, these methods require the exact observance of all procedures (from the formulation of the problem, the choice of parameters, the degree of similarity of the model and the original to the interpretation of the results), and even if all requirements are ideally met, the results of the research will be of a fundamentally probabilistic 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 kind 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 solutions obtained is sought. This procedure, which is not typical for the science of the past, has a colossal 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 in the modeling of the Universe, were born by the development of computer technology. Based on them, models of the Universe with an inflationary phase have been improved; at the beginning of the XXI century. processed large amounts of information received from a space probe, and created a model for the development of the universe, 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 a void, not as an ether, but as a complex state with a potential (virtual) content of matter and energy. It was found that the known modern science cosmic bodies and fields make up a small percentage of the mass of the universe, and most of the mass lies in indirectly revealing itself "dark matter" and "dark energy". Research recent years showed that a significant part of this energy acts on the expansion, stretching, tearing of the Universe, which can lead to a fixed expansion acceleration. In this regard, the scenario of 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 that does not depend on any factors (substantial concept, coming from Democritus and underlying the classical Newtonian model of the Universe), or as a parameter associated with the shift of matter (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, the static one, has also been put forward. Time in various models is either cyclic, or finite, or infinite and linear. The essence of time is most often associated with causality. Such problems are discussed as the substantiation of the allocation of the present moment of time, its direction, anisotropy, irreversibility, universality of time, i.e. Does time exist under all states of the Universe and is it always one-dimensional or can it have a different dimension and not even exist under certain conditions (for example, at a singularity point). The least developed question is about the features of time in complex systems: biological, mental, social.

When creating models of the Universe, some constants play an essential role - the gravitational constant, Planck's constant, the speed of light, the average density of matter, the number of dimensions of space-time. Exploring these constants, some cosmologists have come 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 even more so mind.

REFERENCES

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

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

Linde A.D. Physics elementary particles and inflationary cosmology. M., 1990.

Nadtochaev A.S. Philosophy and science in the era of 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.

Models of the stationary Universe. The uniqueness of the Universe does not allow for an experimental verification of the hypotheses put forward and raising them to the level of theories, so the evolution of the Universe can only be considered within the framework of models.

After creation classical mechanics scientific picture of the world was based on Newtonian concepts of space, time and gravity and described a constant in time, i.e. stationary, infinite Universe created by the Creator.

In the XX century. new theoretical basis to create new cosmological models.

First of all, it is necessary to mention the cosmological postulate, according to which the physical laws established in a limited part of the Universe are also valid for the entire Universe. In addition, the homogeneity and isotropy of the large-scale distribution of matter in the Universe is considered an axiom. At the same time, the model of evolution should correspond to the so-called anthropic principle, i.e. to provide for the possibility of the appearance at a certain stage of evolution of an observer (reasonable person).

Since it is gravitation that determines the interaction of masses at large distances, the theoretical core of cosmology of the twentieth century. became the relativistic theory of gravity and space-time - the general theory of relativity. According to this theory, the distribution and movement of matter determine geometric properties space-time and at the same time they themselves depend on them. The gravitational field manifests itself as a "curvature" of space-time. In Einstein's first cosmological model, based on general relativity in 1916, the universe is also stationary. It is boundless, but closed and has finite dimensions. The space closes on itself.

Friedman's models of the non-stationary Universe. Einstein's model of the stationary Universe was refuted in the works of the Russian scientist A.A. Friedman (1888 - 1925), who in 1922 showed that curved space cannot be stationary: it must either expand or contract. Three different models of the change in the radius of curvature of the Universe are possible, depending on the average density of matter in it, and in two of them the Universe expands infinitely, and in the third, the radius of curvature changes periodically (the Universe pulsates).

Although the discovery by E. Hubble of the law of the dependence of the velocity of galaxies receding on the distance to them confirmed the expansion of the Universe, at present, a comparison of the experimentally estimated density of matter with the critical value of this parameter, which determines the transition from expansion to pulsation, does not make it possible to unambiguously choose a scenario for further evolution. These two quantities turned out to be close, and the experimental data were not sufficiently reliable.

The expansion of the Universe is currently a well-founded and generally recognized fact that allows us to estimate the age of the Universe. According to the most common estimates, it is 10 18 s (18 billion years). Therefore, current models suggest a "beginning" of the universe. How did its evolution begin?

hot universe model. At the core contemporary ideas about the initial stages of the evolution of the Universe lies the model of the "hot Universe", or " big bang”, the foundations of which were laid in the 40s of the XX century. Russian scientists working in the USA, G.A. Gammov (1904 - 1968). In the simplest version of this model, it seems that the Universe arose spontaneously as a result of an explosion from a superdense and superhot state with infinite space curvature (singularity state). The "hotness" of the initial singular state is characterized by the predominance of electromagnetic radiation in it over matter. This is confirmed by the experimental discovery in 1965 by American astrophysicists Penzias (b. 1933) and Wilson (b. 1936) of isotropic electromagnetic "relic radiation". Modern physical theories make it possible to describe the evolution of matter starting from the moment of time t= 10 -43 s. The very initial moments of the evolution of the Universe are still behind the physical barrier. Only from the moment t= 10 -10 s after the Big Bang, our ideas about the state of matter in the early Universe and the processes occurring in it can be tested experimentally and described theoretically.

As the universe expands, the density of matter in it decreases and the temperature drops. At the same time, processes of qualitative transformations of particles of matter take place. At the moment 10 -10 s the matter consists of free quarks, leptons and photons (see Section III). As the Universe cools, the formation of hadrons occurs, then the nuclei of light elements appear - isotopes of hydrogen, helium, lithium. The fusion of helium nuclei stops at the moment t= 3 min. Only after hundreds of thousands of years, the nuclei are combined with electrons, and hydrogen and helium atoms arise, and from that moment on, the substance ceases to interact with electromagnetic radiation. "Relic" radiation arose precisely during this period. When the size of the universe was about 100 times smaller than at the present era, gaseous clumps arose from the heterogeneities of gaseous hydrogen and helium, which fragmented and led to the emergence of stars and galaxies.

The question of the exclusivity of the Universe as an object of cosmology remains open. Along with the widespread point of view that the entire Universe is our Metagalaxy, there is an opposite opinion that the Universe can consist of many metagalaxies, and the idea of ​​the uniqueness of the Universe is historically relative, determined by the level of science and practice.

In 1917, A. Einstein built a model of the Universe. In this model, to overcome the gravitational instability of the Universe, a cosmological repulsive force, called the lambda parameter, was used. In the future, Einstein will say that this was his grossest 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 form of a hypercylinder, the length of which was determined by the total number and composition of forms of manifestation of energy (substance, field, radiation, vacuum) in this cylinder. Time in this model is directed from the infinite past to the infinite future. Thus, here the magnitude of the energy-mass of the Universe (substance, field, radiation, vacuum) is proportionally related to its spatial structure: limited in its form, but of infinite radius and infinite in time.

Researchers who began to analyze this model noticed

on its extreme instability, similar to a coin standing on its edge, one side of which corresponds to the expanding Universe, the other - closed: when taking into account some physical parameters of the Universe, according to Einstein's model, it turns out to be eternally expanding, when taking into account others - closed. For example, the Dutch astronomer W. de Sitter, assuming 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,fAndhik And mathematician of Petrograd University, publishedV1922 G. article« ABOUTcurvaturespaces."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: a model of the Universe in Euclidean space ( TO = 0); model with 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 density, pressure of the energy-matter component of the Universe (substance, field, radiation , vacuum). The conclusions of A. Friedman 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, obtained a model of the Universe in which the curvature coefficient is equal to 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 found 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 equal to 2 · 10 -29 g/cm 3 . Having reached a critical density, the Universe will begin to shrink.

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 the observed at a certain moment.

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

Friedman calculated that the observable universe was in a compressed state

according to the model K > 0” about 10-12 billion years ago. After that, it began to expand, but this expansion will not be infinite, 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 microcosm were not clear by that time. The mathematical conclusions of A. Friedman 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. Fridman's letter, acknowledged the correctness of these decisions and called A. Fridman "the first scientist who took the path of building relativistic models of the Universe." Unfortunately, A. Friedman died early. Science has lost a talented scientist in his person.

As noted above, neither A. Friedman nor A. Einstein knew the data on the fact of the "retreat" 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. HOalready V 1929

G.Americanastronomer E. Hubble (1889-1953) With help telescope with spectrum instrumentsAanalysisfromwing tAto callemyuheffect

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

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

that the observed galaxies move away, “run away” 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 source of waves is removed relative to the device that fixes the waves, the wavelength increases and becomes shorter when approaching a stationary wave receiver. In the case of light waves, long wavelengths of light correspond to the red segment of the light spectrum (red to violet), short wavelengths 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, 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 is the distance to the observed galaxy, measured in parsecs (1 ps is approximately equal to 3.1 10 1 6 m), VR is the speed of the observed galaxy, Η - Hubble constant, or 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 the objects of 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 are fixed. Calculating the value of this quantity, which later became known as the Hubble constant, E. Hubble came to the conclusion that it is approximately 500 km / (s Mpc). In other words, a piece of space of one million parsecs increases in one second by 500 km.

Formula VR= Нr allows us to consider both the removal of galaxies and the reverse situation, the movement to a certain initial position, the beginning of the “retreat” of galaxies in time. The reciprocal of the Hubble constant has the dimension of time: t(time) = r/Vr = 1/H. With a value H, which was mentioned above, E. Hubble obtained the time of the beginning of the "recession" of galaxies, equal to 3 billion years, which caused him to doubt the relativity of the correctness of the value calculated by him. Using the "redshift" effect, E. Hubble reached the most distant galaxies known at that time: the farther the galaxy, the less perceived by us its brightness. This allowed E. Hubble to say that the formula VR = HR expresses the observed fact of the expansion of the Universe, which was mentioned in A. Friedman's model. Astronomical studies 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 hypothesized about the natural reddening of light quanta due to their quantum nature, interaction with the electromagnetic fields of outer space. Others have pointed to the theoretical failure of the Hubble constant: why should the value of the Hubble constant be the same at every instant of time in the evolution of the universe? This stable constancy of the Hubble constant suggests that the laws of the Universe known to us, acting 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 "blush" due to the influence of the interstellar (ISS) and intergalactic (IGS) medium on it, which can lengthen the wavelength of its movement towards the observer. Another issue that caused discussions in connection with E. Hubble's research was the question of the assumption of the possibility of galaxies moving at a speed 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 E. Hubble's observations have established the fact of the expansion of the Universe.

The fact of the 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)centurydrewheedAnieonsleblowingcircumstance:recession of galaxiesmeansextensionspace,hence,Vpast

wasdecreasevolumeAndPlrelationVecreatures. Lemaitre called the initial density of matter a protoatom with a density of 10 9 3 g/cm 3 , from which the world was created by God. It follows from this model that the concept of matter density 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 drew attention to the physical state with superdense and superhot physical parameters. In addition, models have been proposed pulsatingUniverse: The universe expands and contracts, but never reaches its extreme limits. Models of the pulsating Universe attach great importance to the measurement of the energy-matter density in the Universe. When the critical density limit is reached, the Universe expands or contracts. As a result, the term "singulIrnoe"(lat. singularus - separate, single) state in which the density and temperature take on an infinite value. This line of research is faced with 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. Gamov (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 on these problems: where heavy chemical elements, if hydrogen (1 1 H) and helium (4 H) are the most common chemical elements in the universe. G. Gamow suggested that chemical elements trace their history from the very beginning of the expansion of the Universe.

ModelG.GamownAcalledmodel"Bigexplosion,nOsheIt has

AndotherName:"A-B-G-theory". This title indicates the initial letters of the authors of the article (Alfer, Bethe, Gamow), which was published in 1948 and contained the “hot Universe” model, 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 superdense and superhot state.

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

3. An extremely small volume corresponded to this state.

4. Energy-matter, having reached a certain limit of density and temperature in this state, exploded, there was a Big Bang, 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 initial physical state before the Big Bang.

7. Since the initial state was superhot, the expansion must 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 in the universe.

This phenomenon was called relic (ancient), background m radiation.

1953 G. Gamow calculated the wave temperature of the relic radiation. Him

it turned out 10 K. Relic radiation is microwave electromagnetic radiation.

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

Thus, G. Gamow's hypothesis about relic, background radiation was confirmed. In his works on the temperature of the background radiation, G. Gamow used the formula of A. Friedman, which expresses the dependence of the change in the radiation density with time. In parabolic ( K> 0) models of the Universe. Friedman considered the state when radiation prevails over the matter of the infinitely expanding Universe.

According to the Gamow model, there were two epochs 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 prevailed over matter, then there was a time when their ratio was equal, and a period when matter began to prevail over radiation. Gamow determined the boundary between these epochs - 78 million years.

At the end of the twentieth century. measurement of microscopic changes in background radiation, which was called ripplesbYu, allowed a number of researchers to argue that these ripples represent a change in density substancesAndenerGaiV result of the action of gravitational forces on early stages of development Universe.

Model "InflyatsiOnoahUniverse".

The term "inflation" (lat. inflation) is treated as swelling. Two researchers A. Gut and P. Seinhardt proposed this model. In this model, the evolution of the Universe is accompanied by a giant swelling of the quantum vacuum: in 10 -30 s, the size of the Universe increases by 1050 times. Inflation is an adiabatic process. It is associated with cooling and the emergence of a difference between the weak, electromagnetic and strong interactions. The analogy of the expansion of the Universe can be, roughly speaking, represented as a sudden crystallization of a supercooled liquid. Initially, the inflationary phase was seen as the "second birth" 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, due to random fluctuations, a uniform configuration of this field larger than 10 -33 cm was formed. From it, the expansion and heating of the Universe in which we live occurred.

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 s of expansion. The inflation phase means that the observable universe is only part of the universe. The textbook by T. Ya. Dubnishcheva "Concepts of modern natural science" suggests the following course of events according to the "Inflationary Universe" model:

1) t - 10 - 4 5 s. By this moment, after the beginning of the expansion of the Universe, 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 bother 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 the 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 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, quarks are first retained in hadrons, and then the nuclei of future atoms are formed, from which matter is subsequently formed.

It follows from this model that in 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 takes place. Heating occurs as a result of the appearance 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 from cosmology the concept

"Big Bang" as a special, unusual, exceptional state in the evolution of the Universe. However, an equally unusual state appears in this model. This state tonfandnflaton 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 inhomogeneity of the Universe (density of matter condensation). In particular, it is believed that when the Universe was inflated, cosmic inhomogeneities-textures arose as the embryos of aggregates of matter, which later grew into galaxies and their clusters. This is evidenced by the data recorded in 1992. the deviation of the temperature of the background radiation from its average value of 2.7 K by about 0.00003 K. Both models speak of a hot expanding Universe, on average homogeneous and isotropic with respect to the background radiation. In the latter case, we have in mind the fact of almost the same value of the relict radiation in all parts of the observable Universe in all directions from the observer.

There are alternatives to the "Big Bang" and "Inflationary

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 the "cosmological constancy" of the Universe: not only should there not be a single selected place in the Universe, but not a single moment should be singled out in time. The authors of this model are G. Bondy, T. Gold and F. Hoyle, the latter is a well-known author of popular books on problems of cosmology. In one of his works he wrote:

"Every cloud, galaxy, every star, every atom had a beginning, but not the whole universe, the universe is something more than its parts, although this conclusion may seem unexpected." This model assumes the existence of an internal source in the Universe, a reservoir of energy that maintains the density of its energy-matter at a "constant level that prevents the Universe from shrinking." 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 the atoms of chemical elements, matter, etc., arose.

e. The discovery of relict, background radiation severely 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 the radiation density and temperature according to the model

The "Big Bang" with radio astronomy data allowed Ya. Zel'dovich 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 the cosmic microwave background, which confirms the hypothesis of an initial hot state in the evolution of the Universe, led Zel'dovich to abandon his own model of the "Cold Universe". However, the idea of ​​calculating the ratios 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 density of energy-matter in the Universe coincides with the density of relic 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. Fridman. 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 own galaxies, stars, etc. These objects are called freadmonov. Academician A. A. Markov hypothesized that there can be an unlimited number of Friedmons and they can be completely open, i.e. they have an entrance to their world and an exit (connection) with other worlds. It turns out a lot of Universes, or, as Corresponding Member of the USSR Academy of Sciences I.S. Shklovsky called in one of his works, - Metaverse.

The idea of ​​a plurality of Universes was put forward by A. Gut, one of the authors of the inflationary model of the Universe. In the inflating Universe, the formation of "aneurysms" (a term from medicine, means protrusion of the walls of blood vessels) from the parent 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 matter

to a size smaller than one quadrillion part of an elementary particle.

SELF-CHECK QUESTIONS

1. Big bang model.

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

modern cosmology.

3. Relic, background radiation.

4. Model "Inflationary Universe".

No physicist today disputes the special theory of relativity, and only a few dispute the basic provisions of the general theory of relativity. True, the general theory of relativity leaves many important problems unresolved. There is no doubt that the observations and experiments supporting this theory are few and not always convincing. But even if there were no evidence at all, general relativity would still be extraordinarily attractive because of the great simplifications it introduces into physics.

Simplifications? It may seem strange to use this word in relation to a theory that uses mathematics so advanced that someone once said that no more than twelve people in the whole world could understand it (by the way, this number was clearly underestimated even at the time when this opinion was generally accepted).

The mathematical apparatus of the theory of relativity is indeed complex, but this complexity is offset by an extraordinary simplification of the overall picture. For example, the reduction of gravity and inertia to the same phenomenon is enough to make the general theory of relativity the most fruitful direction in the formation of a view of the world.

Einstein expressed this idea in 1921 when he was giving a lecture on relativity at Princeton University: The possibility of explaining the numerical equality of inertia and gravitation by the unity of their nature gives the general theory of relativity, in my opinion, such advantages over the concepts of classical mechanics that, in comparison with this, all the difficulties encountered here should be considered small ...»

In addition, the theory of relativity has what mathematicians like to call "gracefulness." This is a kind of artistic work. “Every lover of the beautiful,” Lorenz once said, “should wish that it turned out to be correct.”

In this chapter, the firmly established aspects of the theory of relativity will be left aside, and the reader will plunge into a realm of bitter controversy, a realm where points of view are nothing more than assumptions that must be accepted or rejected on the basis of scientific evidence.

What is the universe as a whole? We know that the Earth is the third planet from the Sun in a system of nine planets, and that the Sun is one of the approximately one hundred billion stars that make up our Galaxy. We know that in the region of space that can be probed by the most powerful telescopes, other galaxies are scattered, the number of which should also be in the billions. Does this continue indefinitely?

Is the number of galaxies infinite? Or does space still have finite dimensions? (Perhaps we should say "our space", because if our space is limited, then who can say that there are no other limited spaces?)

Astronomers are working hard to answer these questions. They construct so-called models of the Universe - imaginary pictures of the world, if it is considered as a whole. In the early nineteenth century, many astronomers assumed that the universe was infinite and contained an infinite number of suns. The space was considered to be Euclidean. Direct showers went to infinity in all directions. If the spaceship were to travel in any direction and move in a straight line, then its journey would take an infinitely long time, and it would never reach the boundary. This view goes back to the ancient Greeks. They liked to say that if a warrior threw his spear farther and farther into space, he could never reach the end; if such an end were imagined, then the warrior could stand there and throw a spear even further!

There is one important objection to this view. The German astronomer Heinrich Olbers noted in 1826 that if the number of suns is infinite and these suns are randomly distributed in space, then a straight line drawn from the Earth in any direction must eventually pass through some star. This would mean that the entire night sky would have to be one continuous surface emitting blinding starlight. We know it's not. Some explanation for the darkness of the night sky must be devised to explain what is now called Olbers' paradox. Most astronomers of the late nineteenth and early twentieth centuries believed that the number of suns was limited. Our galaxy, they argued, contains all the available suns. What is outside the galaxy? Nothing! (It was not until the mid-twenties of this century that irrefutable evidence appeared that there were millions of galaxies at vast distances from our own.) Other astronomers assumed that light from distant stars could be absorbed by clusters interstellar dust.

The most ingenious explanation was given by the Swedish mathematician W. K. Charlier. Galaxies, he said, are grouped into associations, associations - into super-associations, super-associations - into super-super-associations, and so on ad infinitum. At each stage of association, the distances between groupings grow faster than the size of the groups. If this is correct, then the farther the straight line continues from our galaxy, the less likely it is to meet another galaxy. At the same time, this hierarchy of associations is infinite, so that one can still say that the Universe contains an infinite number of stars. There is nothing wrong with Charlier's explanation of Olbers' paradox, except that there is the following simpler explanation.

The first model of the universe based on the theory of relativity was proposed by Einstein himself in an article published in 1917. It was an elegant and beautiful model, although Einstein was later forced to abandon it. It has already been explained above that gravitational fields are the curvature of the space-time structure produced by the presence of large masses of matter. Within each galaxy, therefore, there are many such twists and turns of space-time. But what about the vast areas of empty space between galaxies? One Tacon point of view: the greater the distance from galaxies, the flatter (more Euclidean) space becomes. If the universe were free of all matter, then space would be perfectly flat; some, however, believe that in this case it would be meaningless to say that it has any structure at all. In both cases, the universe of space-time extends indefinitely in all directions.

Einstein made one tempting counteroffer. Suppose, he said, that the amount of matter in the universe is large enough to provide an overall positive curvature. Space would then close on itself in all directions. This cannot be fully understood without delving into four-dimensional non-Euclidean geometry, but the meaning can be grasped quite easily with the help of a two-dimensional model. Imagine a flat country called Ploskovia, where two-dimensional beings live. They consider their country to be a Euclidean plane that extends indefinitely in all directions. True, the suns of Ploskovia are the cause of the appearance of various bulges on this plane, but these are local bulges that do not affect the overall smoothness. There is, however, another possibility that the astronomers of this country can imagine. Perhaps each local bulge produces a slight curvature of the entire plane in such a way that the total action of all the suns will lead to deformation of this plane into something similar to the surface of a bumpy sphere. Such a surface would nevertheless be limitless in the sense that you could move in any direction forever and never reach the boundary. The warrior of Flats could not find a place beyond which he would have nowhere to throw his flat spear. However, the surface of the country would be finite. A traveler traveling in a "straight line" long enough would eventually arrive back at the same place where he started his journey.

Mathematicians say that such a surface is "closed". It is, of course, not unlimited. Like the infinite Euclidean space, its center is everywhere, the periphery does not exist. This “closure”, a topological property of such a surface, can be easily verified by the inhabitants of this country. One criterion has already been mentioned: movement around the sphere in all directions. Another way to check would be to paint this surface. If an inhabitant of this country, starting from some place, began to draw larger and larger circles, he would eventually enclose himself inside a spot on the opposite side of the sphere. However, if this sphere is large and the inhabitants occupy a small part of it, they will not be able to make such topological tests.

Einstein suggested that our space is a three-dimensional "surface" of a huge hypersphere ( four-dimensional sphere). Time in his model remains uncurved; it is a direct coordinate extending back into the infinitely distant past and extending infinitely far forward into the future. If this model is thought of as a four-dimensional space-time structure, it looks more like a hypercylinder than a hypersphere. For this reason, such a model is usually called the "cylindrical universe" model. At any given time, we see space as a kind of three-dimensional cross-section of a hypercylinder. Each cross section represents the surface of a hypersphere.

Our Galaxy occupies only a small part of this surface, so it is not yet possible to perform a topological experiment that would prove its closedness. But there is a fundamental possibility of proving closedness. By setting a sufficiently powerful telescope in some direction, you can focus it on a particular galaxy, and then, turning the telescope in opposite side, to see the other side of the same galaxy. If there were spaceships that traveled close to the speed of light, they could circle the universe, moving in any direction in the most straight line possible.

The universe cannot be "colored" in the literal sense of the word, but one can do essentially the same thing by making larger and larger spherical maps of the universe. If the cartographer does this long enough, he may find that he is inside the sphere he is mapping. This sphere will grow smaller and smaller as he continues his occupation, like the circle that shrinks when a Ploskovian encloses himself within the spot.

In some respects, Einstein's non-Euclidean model is simpler than the classical model, in which space is not curved. It is simpler in the same sense that a circle can be said to be simpler than a straight line. A straight line extends to infinity in both directions, and infinity in mathematics is a very complicated thing! The convenience of a circle is that it is limited. It has no ends, no one has to worry about what will happen to this line in infinity. In a neat Einsteinian universe, no one has to care about all the free ends at infinity, what cosmologists like to call "boundary conditions." In Einstein's cozy universe, boundary problems do not exist because it has no boundaries.

Other cosmological models, fully consistent with the general theory of relativity, were discussed in the twenties. Some of them have properties even more unusual than Einstein's cylindrical universe. Dutch astronomer Billem de Sitter developed a model of a closed, limited universe in which time curves in the same way as space. The further you look through de Sitter space, the slower the clock seems to go. If you look far enough, you can see areas where time has completely stopped, "like at Mad Shlyapochkin's tea party," writes Eddington, "where it's always six o'clock in the evening."

“You don't have to think that there is some kind of boundary,” explains Bertrand Russell in The ABC of Relativity. “People living in the country, which our observer considers the country of lotophages, live in exactly the same bustle as the observer himself, and it seems to them that he himself is frozen in eternal immobility. In fact, you would never know about this land of lotophages, since it would take an infinitely long time for the light to reach you from it. You could find out about places located near her, but she herself would always remain behind the horizon. Of course, if you were to head towards this area on spaceship If you keep it under constant observation with a telescope, you would see that as you approach it, the passage of time there slowly accelerates. When you get there, everything will move at normal speed. The land of the Lotus Eaters will now be on the edge of a new horizon.

Have you noticed that when an airplane flies low over you and soars up sharply, the pitch of the sound from its motors immediately drops a little? This is called the Doppler effect, after the Austrian physicist Christian Johann Doppler, who discovered this effect in the mid-nineteenth century. It's easy to explain. As the plane approaches, the sound waves from its engines vibrate your eardrum more frequently than it would if the plane was stationary. This increases the pitch of the sound. As the plane moves away, the jolts you feel in your ears from the sound vibrations are less frequent. The sound becomes lower.

Exactly the same thing happens when the light source moves quickly towards you or away from you. At the same time, the speed of light (which is always constant) should remain unchanged, but not its wavelength. If you and the light source are moving towards each other, then the Doppler effect shortens the wavelength of the light, shifting the color towards the violet end of the spectrum. If you and the light source move away from each other, then the Doppler effect gives a similar shift towards the red end of the spectrum.

Georgy Gamow, in one of his lectures, told a story (undoubtedly anecdotal) with the Doppler effect, which is too good not to tell here. This happened, it seems, with the famous American physicist from Johns Hopkins University, Robert Wood, who was detained in Baltimore for running a red light. Appearing before the judge, Wood brilliantly explained, based on the Doppler effect, that due to the high speed of his movement, the red light shifted to the violet end of the spectrum, which is why he perceived it as green. The judge was inclined to acquit Wood, but one of Wood's students happened to be on trial, whom Wood had failed shortly before. He quickly calculated the speed it takes to turn a traffic light from red to green. The judge dropped the original charge and fined Wood for speeding.

Doppler thought that the effect he discovered explained the apparent color of distant stars: reddish stars should move away from the Earth, bluish stars should move towards the Earth. As it turned out, this was not the case (these colors were due to other reasons); in the twenties of our century, it was discovered that light from distant galaxies exhibits a clear redshift, which cannot be explained convincingly enough except by assuming that these galaxies move away from the Earth. Moreover, this shift increases on average in proportion to the distance from the galaxy to the Earth. If galaxy A is twice as far away as galaxy B, then the redshift from A is approximately twice the redshift from B. According to the English astronomer Fred Hoyle, the redshift for the association of galaxies in the constellation Hydra indicates that this the association is moving away from the Earth at an enormous speed, equal to about 61,000 km / s.

Various attempts have been made to explain the redshift not by the Doppler effect, but in some other way. According to the theory of “light fatigue”, the longer the light is on the way, the lower the frequency of its oscillations. (This is a perfect example of a conjecture ad hoc, i.e., a hypothesis related only to this particular phenomenon, since there is no other evidence in its favor.) Another explanation is that the passage of light through cosmic dust leads to a displacement. In the de Sitter model, this shift clearly follows from the time curvature.

But the simplest explanation that fits best with others known facts, is that the redshift really indicates real movement galaxies. Based on this assumption, a new series of "expanding universe" models was soon developed.

However, this expansion does not mean that the galaxies themselves are expanding, or that (as it is now believed) the distances between galaxies in galaxy associations are increasing. Apparently, this expansion entails an increase in the distances between associations. Imagine a giant ball of dough, which is interspersed with several hundred raisins. Each raisin represents an association of galaxies. If this dough is put in the oven, it expands evenly in all directions, but the dimensions of the raisins remain the same. The distance between raisins increases. None of the raisins can be called an expansion center. From the point of view of any single raisin, all other raisins appear to be moving away from it.

The greater the distance to the raisin, the greater the apparent speed of its removal.

Einstein's model of the universe is static. This is because he developed this model before astronomers discovered the expansion of the universe. In order to prevent the contraction of his Universe by gravitational forces and its death, Einstein was forced to assume in his model that there is another force (he introduced it into the model using the so-called "cosmological constant"), the role of which is to repel and hold stars on some distance from each other.

Calculations performed later showed that Einstein's model is unstable, like a coin standing on its edge. The slightest push will make it fall either on the front or on the back side, the first corresponding to an expanding, the second - a contracting universe. The discovery of redshift showed that the universe is not contracting anyway; cosmologists turned to models of the expanding universe.

Various models of the expanding Universe were constructed. The Soviet scientist Alexander Friedman and the Belgian abbe Georges Lemaitre developed the two most famous models. In some of these models, space is assumed to be closed (positive curvature), in others it is open (negative curvature), and in others, the question of whether space is closed remains open.

One of the models was proposed by Eddington, who described it in the fascinating book The Expanding Universe. His model is essentially very similar to Einstein's, it is closed, like a huge four-dimensional ball, and expands uniformly in all its three spatial dimensions. At present, however, astronomers are not certain that space is closed in on itself. Apparently, the density of matter in space is insufficient to lead to positive curvature. Astronomers favor an open or infinite universe with an overall negative curvature resembling the surface of a saddle.

The reader should not think that if the surface of a sphere has a positive curvature, then from the inside this surface will have a negative curvature. The curvature of a spherical surface is positive, regardless of whether you look at it from the outside or from the inside. The negative curvature of the surface of the saddle is due to the fact that at any point this surface is curved in different ways. It is concave if you run your hand along it from the back to the front, and convex if you run your hand from one edge to the other. One curvature is expressed by a positive number, the other by a negative one. To get the curvature of this surface at a given point, these two numbers must be multiplied. If at all points this number is negative, as it should be when the surface is curved differently at any point, then this surface is said to have a negative curvature. The surface surrounding a hole in a torus (donut) is another well-known example of a surface of negative curvature. Of course, such surfaces are only rough models of a three-dimensional space of negative curvature.

Perhaps, with the advent of more powerful telescopes, it will be possible to solve the question of what is the curvature of the Universe - positive, negative or equal to zero. The telescope allows you to see galaxies only in a certain spherical volume. If the galaxies are randomly distributed and if space is Euclidean (zero curvature), the number of galaxies inside such a sphere must always be proportional to the cube of the sphere's radius. In other words, if you build a telescope that can look twice as far as any telescope before it, then the number of visible galaxies should increase from n before 8n. If this jump turns out to be smaller, then this will mean that the curvature of the Universe is positive, if more - negative.

One might think that it should be the other way around, but consider the case of two-dimensional surfaces with positive and negative curvature. Suppose a circle is cut from a flat sheet of rubber.

Raisins are glued on it at distances of half a centimeter from one another. In order to give this rubber the shape of a spherical surface, it must be compressed, and many of the raisins will come together. In other words, if on a spherical surface the raisins must remain half a centimeter apart, then fewer raisins will be needed. If the rubber is applied to the surface of the saddle, then the raisins will move apart over long distances, i.e., in order to maintain the distance between the raisins of half a centimeter on the surface of the saddle, more raisins will be required. The moral that follows from all this can be jokingly expressed like this: when you buy a bottle of beer, be sure to tell the seller that you want a bottle that contains space curved negatively, not positively?

Models of the expanding Universe do not require Einstein's cosmological constant, which leads to the hypothetical repulsion of stars.

(Later, Einstein considered the concept of the cosmological constant to be the biggest mistake he ever made.) With the advent of these models, the issue of Olbers' paradox about the brightness of the night sky was immediately cleared up. Einstein's static model was of little help in this regard. True, it contains only a finite number of suns, but due to the closeness of space in the model, the light from these suns is forced to go around the Universe forever, bending its trajectory in accordance with local curvature of space-time. As a result, the night sky is as brightly lit as it is with an infinite number of suns, unless we assume that the universe is so young that the light could only complete a limited number of annular orbits.

The concept of an expanding universe removes this paradox very simply. If distant galaxies are moving away from Earth at speeds proportional to their distances, then the total amount of light reaching Earth must decrease. If any galaxy is far enough away, its speed can exceed the speed of light, then the light from it will never reach us at all. Many astronomers now seriously believe that if the universe were not expanding, there would be literally no difference between night and day.

The fact that the speed of distant galaxies relative to the Earth can exceed the speed of light would seem to violate the premise that no material body can move faster than light. But, as we saw in Chap. 4, this provision is only valid under conditions that meet the requirements special theory relativity. In general relativity, it should be rephrased as: no signals can be transmitted faster than light. But the important question still remains: can distant galaxies actually overcome the light barrier and, becoming invisible, forever disappear from the field of view of man, even if he has the most powerful telescopes imaginable. Some experts believe that the speed of light is indeed the limit and that the most distant galaxies will simply become dimmer, never becoming completely invisible (provided, of course, that a person has enough sensitive instruments for their observation).

Old galaxies, as someone once pointed out, never die. They just gradually disappear. It is important to understand, however, that no galaxy disappears in the sense that its matter disappears from the Universe. It simply reaches such a speed that it becomes impossible or almost impossible to detect it in terrestrial telescopes. The vanishing galaxy continues to be visible from all galaxies closer to it. Every galaxy has an "optical horizon," a spherical boundary beyond which its telescopes cannot penetrate. These spherical horizons do not coincide for any two galaxies. Astronomers have calculated that the point at which galaxies begin to disappear from our "field of view" is about twice as far as the reach of any modern optical telescope. If this assumption is correct, then about one-eighth of all galaxies that could ever be observed are now visible.

If the universe is expanding (it doesn't matter if space is flat, open, or closed), then such a tricky question arises. What was the universe like before? There are two different ways to answer this question, two modern models of the universe. Both models are discussed in the next chapter.

Notes:

book character Lewis Querrol"Alice in Wonderland". - Note. translation.

A land of plenty and idleness, see The Odyssey. - Note. translation.