Big universe online magazine. Scientists have proven that the universe could not have been born without a big bang. Epoch before recombination

On the edge of the world

What is the Big Universe

Objects inhabiting the Big Universe

What space of the Big Universe

wandering planets

intergalactic space

Formation of the Small Universe

The Big Bang Theory of the Universe

Quasars

Impossible to travel to the Big Universe

The large-scale structure of the Universe as it appears in 2.2 µm infrared - 1,600,000 galaxies recorded in the Extended Source Catalog as a result of the Two Micron All-Sky Survey. The brightness of galaxies is shown in color from blue (brightest) to red (dimest). The dark strip along the diagonal and the edges of the picture is the location of the Milky Way, the dust of which interferes with observations

The universe is a concept that does not have a strict definition in astronomy and philosophy. It is divided into two fundamentally different entities: speculative(philosophical) and material observable now or in the foreseeable future. If the author distinguishes between these entities, then, following the tradition, the first is called the Universe, and the second - the astronomical Universe or Metagalaxy (this term has practically fallen out of use recently). The Universe is the subject of study of cosmology.

Historically, various words have been used to refer to "all space", including equivalents and variants from various languages, such as "cosmos", "world", "celestial sphere". The term "macrocosm" has also been used, although it is intended to define systems on a large scale, including their subsystems and parts. Similarly, the word "microcosm" is used to refer to systems on a small scale.

Any study, any observation, whether it is a physicist's observation of how the nucleus of an atom splits, a child watching a cat, or an astronomer conducting observations of the far, far away - all this is an observation of the Universe, or rather, of its individual parts. These parts are the subject of study of individual sciences, and the Universe on the largest possible scale, and even the Universe as a whole, are occupied by astronomy and cosmology; in this case, the Universe is understood either as a region of the world covered by observations and space experiments, or as an object of cosmological extrapolations - the physical Universe as a whole.

The subject of the article is knowledge about the observable Universe as a whole: observations, their theoretical interpretation and the history of formation.

Among the unequivocally interpretable facts about the properties of the Universe, we present here the following:

The theoretical explanations and descriptions of these phenomena are based on the cosmological principle, the essence of which is that observers, regardless of the place and direction of observation, on average reveal the same picture. Theories themselves seek to explain and describe the origin chemical elements, the course of development and the reason for the expansion, the emergence of a large-scale structure.

The first significant push towards modern ideas about the universe was made by Copernicus. The second largest contribution was made by Kepler and Newton. But truly revolutionary changes in our understanding of the universe occur only in the 20th century.

Etymology

In Russian, the word "Universe" is a borrowing from the Old Slavonic "vsєlena", which is a tracing-paper of the ancient Greek word "oecumene" (Old Greek οἰκουμένη), from the verb οἰκέω "I inhabit, I inhabit" and in the first meaning it made sense only the inhabited part of the world . Therefore, the Russian word "Universe" is related to the noun "settlement" and only consonant with the attributive pronoun "everything". The most general definition for "the Universe" among ancient Greek philosophers, beginning with the Pythagoreans, was τὸ πᾶν (Everything), which included both all matter (τὸ ὅλον) and the entire cosmos (τὸ κενόν).

The face of the universe

Representing the Universe as the whole surrounding world, we immediately make it unique and unique. And at the same time, we deprive ourselves of the opportunity to describe it in terms of classical mechanics: because of its uniqueness, the Universe cannot interact with anything, it is a system of systems, and therefore such concepts as mass, shape, size lose their meaning in relation to it. Instead, one has to resort to the language of thermodynamics, using such concepts as density, pressure, temperature, and chemical composition.

Universe expansion

However, the Universe bears little resemblance to ordinary gas. Already on the largest scales, we are faced with the expansion of the Universe and the relict background. The nature of the first phenomenon is the gravitational interaction of all existing objects. It is its development that determines the future of the universe. The second phenomenon is a legacy of early eras, when the light of the hot Big Bang practically ceased to interact with matter, separated from it. Now, due to the expansion of the Universe, most of the photons emitted then have moved from the visible range to the microwave radio range.

Hierarchy of scales in the Universe

When going to scales less than 100 Mpc, a clear cellular structure is revealed. Inside the cells, there is emptiness - voids. And the walls are formed from superclusters of galaxies. These superclusters are the upper level of the whole hierarchy, then there are clusters of galaxies, then local groups of galaxies, and the lowest level (scale 5-200 kpc) is a huge variety of various objects. Of course, they are all galaxies, but they are all different: they are lenticular, irregular, elliptical, spiral, with polar rings, with active nuclei, etc.

Of these, it is worth mentioning separately, which are distinguished by a very high luminosity and such a small angular size that for several years after the discovery they could not be distinguished from "point sources" -. The bolometric luminosity of quasars can reach 10 46 - 10 47 erg/s.

Moving on to the composition of the galaxy, we find: dark matter, cosmic rays, interstellar gas, globular clusters, open clusters, binary stars, star systems of higher multiplicity, supermassive and black holes of stellar mass, and, finally, single stars of different populations.

Their individual evolution and interaction with each other gives rise to many phenomena. Thus, it is assumed that the source of energy for the already mentioned quasars is the accretion of interstellar gas onto a supermassive central black hole.

Separately, it is worth mentioning gamma-ray bursts - these are sudden short-term localized increases in the intensity of cosmic gamma radiation with an energy of tens and hundreds of keV. From estimates of distances to gamma-ray bursts, it can be concluded that the energy emitted by them in the gamma range reaches 10 50 erg. For comparison, the luminosity of the entire galaxy in the same range is "only" 10 38 erg/c. Such bright flashes are visible from the farthest corners of the Universe, so GRB 090423 has a redshift of z = 8.2.

The most complex complex, which includes many processes, is the evolution of the galaxy:

The course of evolution is little dependent on what happens to the entire galaxy as a whole. However, the total number of newly formed stars and their parameters are subject to significant external influence. Processes whose scales are comparable or over size galaxies, change the morphological structure, the rate of star formation, and hence the rate of chemical evolution, the spectrum of the galaxy, and so on.

Observations

The diversity described above gives rise to a whole spectrum of problems of an observational nature. One group can include the study of individual phenomena and objects, and these are:

expansion phenomenon. And for this you need to measure the distances and redshifts and as far as possible objects. On closer examination, this results in a whole complex of tasks called the distance scale.
Relic background.
Individual distant objects like quasars and gamma-ray bursts.

Distant and old objects emit little light and giant telescopes are needed, such as the Keck Observatory, VLT, BTA, Hubble, and the E-ELT and James Webb under construction. In addition, specialized tools are needed to complete the first task, such as Hipparcos and Gaia, which is being developed.

As mentioned, the radiation of the relic lies in the microwave range of wavelengths, therefore, radio observations and, preferably, space telescopes such as WMAP and Planck are needed to study it.

The unique features of gamma-ray bursts require not only in-orbit gamma ray laboratories like SWIFT, but also unusual telescopes - robot telescopes - whose field of view is larger than that of the aforementioned SDSS instruments and capable of observing in automatic mode. Examples of such systems are the telescopes of the Russian network "Master" and the Russian-Italian project Tortora.

The previous tasks are work on individual objects. A completely different approach is required for:

Study of the large-scale structure of the universe.
The study of the evolution of galaxies and the processes of its components. Thus, observations of as old objects as possible and in as large a number as possible are needed. On the one hand, massive survey observations are needed. This forces the use of wide field telescopes such as those in the SDSS project. On the other hand, detailing is required, which exceeds by orders of magnitude the needs of most of the tasks of the previous group. And this is possible only with the help of VLBI observations, with a base diameter of , or even more like the Radioastron experiment.

Separately, it is worth highlighting the search for relic neutrinos. To solve it, it is necessary to use special telescopes - neutrino telescopes and neutrino detectors - such as the Baksan neutrino telescope, Baikal underwater, IceCube, KATRIN.

One study of gamma-ray bursts and the cosmic background indicates that only the optical part of the spectrum is not enough here. However, the Earth's atmosphere has only two windows of transparency: in the radio and optical ranges, and therefore one cannot do without space observatories. From the current ones, we will cite Chandra, Integral, XMM-Newton, Herschel as an example. Spektr-UF, IXO, Spektr-RG, Astrosat and many others are under development.

Distance scale and cosmological redshift

Distance measurement in astronomy is a multi-step process. And the main difficulty lies in the fact that the best accuracy in different methods is achieved at different scales. Therefore, to measure more and more distant objects, an increasingly long chain of methods is used, each of which relies on the results of the previous one.

All these chains are based on the trigonometric parallax method - the basic one, the only one where the distance is measured geometrically, with minimal involvement of assumptions and empirical patterns. Other methods, for the most part, use a standard candle - a source with a known luminosity - to measure the distance. And the distance to it can be calculated:

where D is the desired distance, L is the luminosity, and F is the measured luminous flux.

Scheme of the occurrence of annual parallax

Parallax is the angle resulting from the projection of the source onto the celestial sphere. There are two types of parallax: annual and group.

Annual parallax - the angle at which the average radius of the Earth's orbit would be visible from the center of mass of the star. Due to the movement of the Earth in orbit, the apparent position of any star in the celestial sphere is constantly shifting - the star describes an ellipse, the semi-major axis of which turns out to be equal to the annual parallax. According to the known parallax from the laws of Euclidean geometry, the distance from the center of the earth's orbit to the star can be found as:

where D is the desired distance, R is the radius of the earth's orbit, and the approximate equality is written for a small angle (in radians). This formula well demonstrates the main difficulty of this method: with increasing distance, the parallax value decreases along a hyperbola, and therefore measuring the distances to distant stars is associated with significant technical difficulties.

The essence of group parallax is as follows: if a certain star cluster has a noticeable speed relative to the Earth, then according to the laws of projection, the visible directions of movement of its members will converge at one point, called the radiant of the cluster. The position of the radiant is determined from the proper motions of the stars and the shift in their spectral lines due to the Doppler effect. Then the distance to the cluster is found from the following relation:

where μ and V r are the angular (in arcseconds per year) and radial (in km/s) velocity of the cluster star, respectively, λ is the angle between the straight lines -star and radiant star, and D is the distance expressed in parsecs. Only the Hyades have noticeable group parallax, but until the launch of the Hipparcos satellite, this is the only way to calibrate the distance scale for old objects.

Method for determining the distance from Cepheids and RR Lyrae stars

On Cepheids and stars of the RR Lyrae type, the unified distance scale diverges into two branches - the distance scale for young objects and for old ones. Cepheids are located mainly in regions of recent star formation and therefore are young objects. RR-type Lyrae gravitate toward old systems, for example, there are especially many of them in globular star clusters in the halo of our Galaxy.

Both types of stars are variable, but if Cepheids are newly formed objects, then RR Lyrae stars have descended from the main sequence - giants of spectral types A-F, located mainly on the horizontal branch of the color-magnitude diagram for globular clusters. However, the way they are used as standard candles is different:

Determination of distances by this method is associated with a number of difficulties:

It is necessary to select individual stars. Within the Milky Way, this is not difficult, but the greater the distance, the smaller the angle separating the stars.

It is necessary to take into account the absorption of light by dust and the inhomogeneity of its distribution in space.

In addition, for Cepheids, it remains a serious problem to accurately determine the zero-point of the "pulsation period - luminosity" dependence. Throughout the 20th century, its value has been constantly changing, which means that the distance estimate obtained in a similar way has also changed. The luminosity of RR Lyrae stars, although almost constant, still depends on the concentration of heavy elements.

Type Ia supernova distance method:

Light curves of various supernovae.

A colossal explosive process occurring throughout the body of the star, while the released energy lies in the range from 10 50 - 10 51 erg. Also, type Ia supernovae have the same luminosity at maximum brightness. Together, this makes it possible to measure distances to very distant galaxies.

Thanks to them, in 1998, two groups of observers discovered the acceleration of the expansion of the Universe. To date, the fact of acceleration is almost beyond doubt, however, it is impossible to unambiguously determine its magnitude from supernovae: the errors for large z are still extremely large.

Usually, in addition to common for all photometric methods, disadvantages and open problems include:

The K-correction problem. The essence of this problem is that it is not the bolometric intensity (integrated over the entire spectrum) that is measured, but in a certain spectral range of the receiver. This means that for sources with different redshifts, the intensity is measured in different spectral ranges. To account for this difference, a special correction is introduced, called the K-correction.

The shape of the distance versus redshift curve is measured by different observatories with different instruments, which causes problems with flux calibrations, etc.

It was previously believed that all Ia supernovae are exploding in a close binary system, where the second component is . However, evidence has emerged that at least some of them may arise during the merger of two white dwarfs, which means that this subclass is no longer suitable for use as a standard candle.

Dependence of the supernova luminosity on the chemical composition of the progenitor star.

Geometry of gravitational lensing:

Geometry of gravitational lensing

Passing near a massive body, a beam of light is deflected. Thus, a massive body is able to collect a parallel beam of light at a certain focus, building an image, and there may be several of them. This phenomenon is called gravitational lensing. If the lensed object is variable and several of its images are observed, this opens up the possibility of measuring distances, since there will be different time delays between images due to the propagation of rays in different parts of the gravitational field of the lens (the effect is similar to the Shapiro effect in ).

If as a characteristic scale for the image coordinates ξ and source η (see figure) in the corresponding planes take ξ 0 =D l and η 0 =ξ 0 D s/ D l (where D- angular distance), then you can record the time delay between images number i And j in the following way:

Where x=ξ /ξ 0 and y=η /η 0 - angular positions of the source and image, respectively, With- the speed of light, z l is the redshift of the lens, and ψ is the deviation potential depending on the choice of model. It is believed that in most cases the real potential of the lens is well approximated by a model in which the matter is distributed radially symmetrically, and the potential turns to infinity. Then the delay time is determined by the formula:

However, in practice, the sensitivity of the method to the form of the galaxy halo potential is significant. So the measured value H 0 for the galaxy SBS 1520+530 varies from 46 to 72 km/(s Mpc) depending on the model.

Red giant distance determination method:

The brightest red giants have the same absolute magnitude −3.0 m ±0.2 m , which means they are suitable for the role of standard candles. Observationally, this effect was first discovered by Sandage in 1971. It is assumed that these stars are either at the top of the first ascent of the red giant branch of low-mass (less than solar) stars or lie on the asymptotic giant branch.

The main advantage of the method is that the red giants are far from the regions of star formation and high concentrations of dust, which greatly facilitates the calculation of extinction. Their luminosity also depends extremely weakly on the metallicity of both the stars themselves and their environment. The main problem of this method is the selection of red giants from observations of the stellar composition of the galaxy. There are two ways to solve it:

• Classic - a method of highlighting the edges of images. In this case, a Sobel filter is usually used. The beginning of the failure is the desired turning point. Sometimes, instead of the Sobel filter, the Gaussian is taken as an approximating function, and the edge detection function depends on the photometric errors of the observations. However, as the star weakens, so do the errors of the method. As a result, the maximum measurable brightness is two magnitudes worse than the equipment allows.

The main problem is the divergence in some cases of the series resulting from the operation of the maximum likelihood method.

Issues and contemporary discussions:

One of the problems is the uncertainty in the value of the Hubble constant and its isotropy. One group of researchers claims that the value of the Hubble constant fluctuates on scales of 10-20°. There are several possible reasons for this phenomenon:

Real physical effect - in this case, the cosmological model must be radically revised;
The standard error averaging procedure is incorrect. This also leads to a revision of the cosmological model, but perhaps not as significant. In turn, many other reviews and their theoretical interpretation do not show an anisotropy exceeding that locally caused by the growth of inhomogeneity, which includes our Galaxy, in an isotropic Universe as a whole.

CMB spectrum

The information that can be obtained by observing the relic background is extremely diverse: the very fact of the existence of the relic background is noteworthy. If the Universe existed forever, then the reason for its existence is unclear - we do not observe mass sources capable of creating such a background. However, if the lifetime of the Universe is finite, then it is obvious that the reason for its occurrence lies in the initial stages of its formation.

To date, the prevailing opinion is that relic radiation is radiation released at the time of the formation of hydrogen atoms. Prior to this, the radiation was locked in matter, or rather, in what it was then - a dense hot plasma.

The method of relict background analysis is based on this assumption. If we mentally trace the path of each photon, it turns out that the surface of the last scattering is a sphere, then it is convenient to expand temperature fluctuations in a series of spherical functions:

where are coefficients, called multipole, and are spherical harmonics. The resulting information is quite varied.

1. Various information is also embedded in deviations from black-body radiation. If the deviations are large-scale and systematic, then the Sunyaev-Zeldovich effect is observed, while small fluctuations are due to fluctuations of matter in the early stages of the development of the Universe.
2. Especially valuable information about the first seconds of the life of the Universe (in particular, about the stage of inflationary expansion) is provided by the polarization of the relic background.

Sunyaev-Zeldovich effect

If CMB photons encounter the hot gas of galaxy clusters on their way, then in the course of scattering due to the inverse Compton effect, the photons will heat up (that is, increase the frequency), taking some of the energy from hot electrons. Observationally, this will be manifested by a decrease in the cosmic microwave background radiation flux in the direction of large clusters of galaxies in the long-wavelength region of the spectrum.

With this effect, you can get information:

about the pressure of hot intergalactic gas in the cluster, and, possibly, about the mass of the cluster itself;
on the cluster velocity along the line of sight (from observations at different frequencies);
on the value of the Hubble constant H0, with the involvement of observations in the gamma range.

With a sufficient number of observed clusters, one can also determine the total density of the Universe Ω.

CMB polarization map according to WMAP data

The polarization of the cosmic microwave background radiation could have arisen only in the era of enlightenment. Since the scattering is Thompson, the relic radiation is linearly polarized. Accordingly, the Stokes parameters Q and U, characterizing the linear parameters, are different, and the parameter V is equal to zero. If the intensity can be expanded in terms of scalar harmonics, then the polarization can be expanded in terms of the so-called spin harmonics:

The E-mode (gradient component) and B-mode (rotary component) are distinguished.

The E-mode can appear when radiation passes through an inhomogeneous plasma due to Thompson scattering. The B-mode, whose maximum amplitude reaches only , appears only when interacting with gravitational waves.

The B-mode is a sign of inflation in the Universe and is determined by the density of primary gravitational waves. Observation of the B-mode is challenging due to the unknown noise level for this component of the CMB, and also due to the fact that the B-mode is mixed by weak gravitational lensing with the stronger E-mode.

To date, polarization has been detected, its value is at a level of several (microkelvins). The B-mode has not been observed for a long time. It was first discovered in 2013 and confirmed in 2014.

CMB fluctuations

After the removal of the background sources, the constant component of the dipole and quadrupole harmonics, only fluctuations scattered over the sky remain, the amplitude spread of which lies in the range from −15 to 15 μK.

For comparison with theoretical data, raw data are reduced to a rotationally invariant quantity:

The “spectrum” is built for the quantity l(l + 1)Cl/2π, from which conclusions important for cosmology are obtained. For example, by the position of the first peak one can judge the total density of the Universe, and by its value - the content of baryons.

So, from the coincidence of the cross-correlation between the anisotropy and the E-mode of polarization with the theoretical predictions for small angles (θ<5°) и значительного расхождения в области больших можно сделать о наличии эпохи рекомбинации на z ≈ 15-20.

Since the fluctuations are Gaussian, the Markov chain method can be used to construct the maximum likelihood surface. In general, the processing of data on the background background is a whole complex of programs. However, both the final result and the assumptions and criteria used are debatable. Various groups have shown the difference between the distribution of fluctuations from Gaussian, the dependence of the distribution map on the algorithms for its processing.

An unexpected result was an anomalous distribution on large scales (from 6° and more). The quality of the latest supporting data from the Planck space observatory eliminates measurement errors. Perhaps they are caused by a yet undiscovered and unexplored phenomenon.

Observation of distant objects

lyman alpha forest

In the spectra of some distant objects one can observe a large accumulation of strong absorption lines in a small section of the spectrum (the so-called forest of lines). These lines are identified as lines of the Lyman series, but with different redshifts.

Clouds of neutral hydrogen effectively absorb light at wavelengths from Lα(1216 Å) to the Lyman limit. Radiation, originally short-wavelength, on the way to us due to the expansion of the Universe is absorbed where its wavelength is compared with this "forest". The interaction cross section is very large and the calculation shows that even a small fraction of neutral hydrogen is sufficient to create a large absorption in the continuous spectrum.

With a large number of clouds of neutral hydrogen in the path of light, the lines will be located so close to each other that a dip forms in the spectrum over a fairly wide interval. The long-wavelength boundary of this interval is due to Lα, and the short-wavelength one depends on the nearest redshift, below which the medium is ionized and there is little neutral hydrogen. This effect is called the Ghan-Peterson effect.

The effect is observed in quasars with redshift z > 6. Hence, it is concluded that the epoch of ionization of the intergalactic gas began at z ≈ 6.

Gravitationally Lensed Objects

Among the effects, the observations of which are also possible for any object (it doesn't even matter if it is far away), one should also include the effect of gravitational lensing. In the previous section, it was pointed out that gravitational lensing is used to build a distance scale; this is a variant of the so-called strong lensing, when the angular separation of source images can be directly observed. However, there is also weak lensing, which can be used to explore the potential of the object under study. Thus, with its help, it was found that clusters of galaxies ranging in size from 10 to 100 Mpc are gravitationally bound, thereby being the largest stable systems in the Universe. It also turned out that this stability is ensured by a mass that manifests itself only in gravitational interaction - dark mass or, as it is called in cosmology, dark matter.

The nature of the quasar

A unique property of quasars is large concentrations of gas in the radiation region. According to modern concepts, the accretion of this gas onto a black hole provides such a high luminosity of objects. A high concentration of a substance also means a high concentration of heavy elements, and hence more noticeable absorption lines. Thus, water lines were found in the spectrum of one of the lensed quasars.

A unique advantage is the high luminosity in the radio range, against its background, the absorption of part of the radiation by cold gas is more noticeable. In this case, the gas can belong both to the quasar's native galaxy, and to a random cloud of neutral hydrogen in the intergalactic medium, or to a galaxy that accidentally fell into the line of sight (in this case, there are often cases when such a galaxy is not visible - it is too dim for our telescopes). The study of interstellar matter in galaxies by this method is called “transmission study”, for example, the first galaxy with supersolar metallicity was discovered in a similar way.

Also, an important result of the application of this method, although not in the radio, but in the optical range, is the measurement of the primary abundance of deuterium. The current value of the deuterium abundance obtained from such observations is .

With the help of quasars, unique data were obtained on the temperature of the background background at z ≈ 1.8 and at z = 2.4. In the first case, we studied the lines of the hyperfine structure of neutral carbon, for which quanta with T ≈ 7.5 K (the supposed temperature of the background background at that time) play the role of pumping, providing an inverse level population. In the second case, the lines of molecular hydrogen H2, hydrogen deuteride HD, and also carbon monoxide CO molecules were found, according to the intensity of the spectrum of which the temperature of the background background was measured, it coincided with the expected value with good accuracy.

Another achievement that took place thanks to quasars is the estimation of the rate of star formation at large z. First, comparing the spectra of two different quasars, and then comparing individual parts of the spectrum of the same quasar, we found a strong dip in one of the UV parts of the spectrum. Such a strong dip could only be caused by a large concentration of dust that absorbs radiation. Previously, they tried to detect dust using spectral lines, but it was not possible to identify specific series of lines, proving that it was dust, and not an admixture of heavy elements in the gas. It was the further development of this method that made it possible to estimate the star formation rate at z from ~ 2 to ~ 6.

Observations of gamma-ray bursts

A popular model for the occurrence of a gamma-ray burst

Gamma-ray bursts are a unique phenomenon, and there is no generally accepted opinion about its nature. However, the vast majority of scientists agree with the statement that stellar mass objects are the progenitor of the gamma-ray burst.

The unique possibilities of using gamma-ray bursts to study the structure of the Universe are as follows:

Since the progenitor of a gamma-ray burst is a stellar mass object, it is possible to trace gamma-ray bursts at a greater distance than quasars, both due to the earlier formation of the progenitor itself, and because of the small mass of the quasar black hole, and hence its smaller luminosity for that period of time. The spectrum of a gamma-ray burst is continuous, that is, it does not contain spectral lines. This means that the most distant absorption lines in the spectrum of a gamma-ray burst are the lines of the interstellar medium of the host galaxy. From the analysis of these spectral lines, one can obtain information about the temperature of the interstellar medium, its metallicity, degree of ionization, and kinematics.

Gamma-ray bursts provide an almost ideal way to study the intergalactic medium before the epoch of reionization, since their influence on the intergalactic medium is 10 orders of magnitude less than that of quasars due to the short lifetime of the source. If the afterglow of the gamma-ray burst in the radio range is strong enough, then the 21 cm line can be used to judge the state of various structures of neutral hydrogen in the intergalactic medium near the progenitor galaxy of the gamma-ray burst. A detailed study of the processes of star formation in the early stages of the development of the Universe with the help of gamma-ray bursts strongly depends on the chosen model of the nature of the phenomenon, but if we collect enough statistics and plot the distributions of the characteristics of gamma-ray bursts depending on the redshift, then, remaining within fairly general provisions, it is possible to estimate the rate of star formation and the mass function of the born stars.

If we accept the assumption that a gamma-ray burst is an explosion of a population III supernova, then we can study the history of the enrichment of the Universe with heavy metals. Also, a gamma-ray burst can serve as an indicator of a very faint dwarf galaxy, which is difficult to detect with "massive" observation of the sky.

A serious problem for observing gamma-ray bursts in general and their applicability for studying the Universe, in particular, is their sporadism and the shortness of time when the burst afterglow, which alone can determine the distance to it, can be observed spectroscopically.

Studying the evolution of the Universe and its large-scale structure

Exploring large-scale structure

2df Survey Large Scale Structure Data

The first method of studying the large-scale structure of the Universe, which has not lost its relevance, was the so-called method of "star counts" or the method of "star scoops". Its essence is to count the number of objects in different directions. Applied by Herschel at the end of the 18th century, when the existence of distant space objects was only suspected, and the only objects available for observation were stars, hence the name. Today, of course, not stars are counted, but extragalactic objects (quasars, galaxies), and in addition to the selected direction, distributions in z are built.

The largest sources of data on extragalactic objects are individual observations of specific objects, surveys such as SDSS, APM, 2df, and compiled databases such as Ned and Hyperleda. For example, in the 2df survey, the sky coverage was ~ 5%, the average z was 0.11 (~ 500 Mpc), the number of objects was ~ 220,000.

The dominant view is that when moving to scales of hundreds of megaparsecs, the cells are added and averaged, and the distribution of visible matter becomes uniform. However, unambiguity in this issue has not yet been achieved: using various methods, some researchers come to the conclusion that there is no uniformity in the distribution of galaxies up to the largest scales studied. At the same time, inhomogeneities in the distribution of galaxies do not cancel the fact of the high homogeneity of the Universe in the initial state, which is derived from the high degree of isotropy of the cosmic microwave background radiation.

At the same time, it was found that the redshift distribution of the number of galaxies is complex. Dependence for different objects is different. However, all of them are characterized by the presence of several local maxima. What this is connected with is not yet entirely clear.

Until recently, it was not clear how the large-scale structure of the Universe evolves. However, recent studies show that large galaxies formed first, and only then small ones (the so-called downsizing effect).

Observations of star clusters

A population of white dwarfs in the globular star cluster NGC 6397. Blue squares are helium white dwarfs, purple circles are "normal" high carbon white dwarfs.

The main property of globular clusters for observational cosmology is that there are many stars of the same age in a small space. This means that if the distance to one member of the cluster is measured in some way, then the difference in the distance to other members of the cluster is negligible.

The simultaneous formation of all the stars in the cluster makes it possible to determine its age: based on the theory of stellar evolution, isochrones are constructed, that is, curves of equal age for stars of different masses. Comparing them with the observed distribution of stars in the cluster, one can determine its age.

The method has a number of its own difficulties. Trying to solve them, different teams, at different times, received different ages for the oldest clusters, from ~8 Ga to ~25 Ga.

In galaxies, globular clusters that are part of the old spherical subsystem of galaxies contain many white dwarfs - the remnants of evolved red giants of relatively small mass. White dwarfs are deprived of their own sources of thermonuclear energy and radiate solely due to the emission of heat reserves. White dwarfs have approximately the same mass of precursor stars, and hence, approximately the same dependence of temperature on time. By determining the current absolute magnitude of a white dwarf from the spectrum of a white dwarf and knowing the time-luminosity dependence during cooling, one can determine the age of the dwarf.

However, this approach is associated with both great technical difficulties - white dwarfs are extremely faint objects - extremely sensitive instruments are needed to observe them. The first and so far the only telescope that can solve this problem is the space telescope. Hubble. The age of the oldest cluster, according to the group working with it: billion years, however, the result is disputed. Opponents indicate that additional sources of errors were not taken into account, their estimate of billions of years.

Observations of non-evolved objects

NGC 1705 - a BCDG-type galaxy

Objects that actually consist of primary matter have survived to our time due to the extremely low rate of their internal evolution. This makes it possible to study the primary chemical composition of the elements, as well as, without going into too much detail and based on the laboratory laws of nuclear physics, to estimate the age of such objects, which will give a lower limit on the age of the Universe as a whole.

This type includes: low-mass stars with low metallicity (the so-called G-dwarfs), low-metal HII regions, as well as dwarf irregular galaxies of the BCDG class (Blue Compact Dwarf Galaxy).

According to modern concepts, lithium should have been formed during the primary nucleosynthesis. The peculiarity of this element lies in the fact that nuclear reactions with its participation begin at temperatures that are not very large, on a cosmic scale. And in the course of stellar evolution, the original lithium had to be almost completely recycled. It could remain only near massive population type II stars. Such stars have a calm, non-convective atmosphere, which allows lithium to remain on the surface without the risk of burning out in the hotter inner layers of the star.

In the course of measurements, it was found that in most of these stars the abundance of lithium is:

However, there are a number of stars, including ultra-low-metal ones, in which the abundance is significantly lower. What this is connected with is not completely clear, it is assumed that this is somehow connected with processes in the atmosphere.

In the star CS31082-001, which belongs to the stellar population of type II, lines were found and concentrations of thorium and uranium in the atmosphere were measured. These two elements have different half-lives, so their ratio changes over time, and if you somehow estimate the initial abundance ratio, then you can determine the age of the star. It can be estimated in two ways: from the theory of r-processes, confirmed both by laboratory measurements and observations of the Sun; or you can cross the curve of concentration changes due to decay and the curve of changes in the abundance of thorium and uranium in the atmospheres of young stars due to the chemical evolution of the Galaxy. Both methods gave similar results: 15.5±3.2 billion years were obtained by the first method, billion years - by the second.

Weakly metallic BCDG galaxies (there are ~10 of them in total) and HII zones are sources of information on the primary abundance of helium. For each object from its spectrum, metallicity (Z) and He concentration (Y) are determined. By extrapolating the Y-Z diagram in a certain way to Z=0, one obtains an estimate of the primordial helium.

The resulting value of Yp varies from one group of observers to another and from one observation period to another. So, one, consisting of the most authoritative experts in this field: Izotova and Thuan (Thuan) obtained the value Yp = 0.245 ± 0.004 for BCDG galaxies, for HII zones at the moment (2010) they settled on the value Yp = 0.2565 ± 0.006. Another authoritative group led by Peimbert also obtained various Yp values, from 0.228±0.007 to 0.251±0.006.

Theoretical models

Of the entire set of observational data for constructing and confirming theories, the key ones are the following:

Their interpretation begins with the postulate that every observer at the same moment of time, regardless of the place and direction of observation, discovers on average the same picture. That is, on large scales, the Universe is spatially homogeneous and isotropic. Note that this statement does not prohibit inhomogeneity in time, that is, the existence of distinguished sequences of events accessible to all observers.

Proponents of theories of a stationary Universe sometimes formulate a "perfect cosmological principle", according to which the four-dimensional space-time should have the properties of homogeneity and isotropy. However, the evolutionary processes observed in the Universe do not seem to be consistent with such a cosmological principle.

In the general case, the following theories and sections of physics are used to build models:

Equilibrium statistical physics, its basic concepts and principles, as well as the theory of relativistic gas.
The theory of gravity, usually GR. Although its effects have only been tested on the scale of the solar system, its use on the scale of galaxies and the universe as a whole can be questioned.
Some information from the physics of elementary particles: a list of basic particles, their characteristics, interaction types, conservation laws. Cosmological models would be much simpler if the proton were not a stable particle and would decay, which modern experiments in physical laboratories do not confirm. At the moment, the set of models that best explain the observational data is:

The Big Bang Theory. Describes the chemical composition of the universe.
Theory of the stage of inflation. Explains the reason for the expansion.
Friedman extension model. Describes an extension.
Hierarchical theory. Describes the large-scale structure.

Expanding Universe Model

The model of the expanding Universe describes the very fact of expansion. In the general case, it is not considered when and why the Universe began to expand. Most models are based on general relativity and its geometric view of the nature of gravity.

If an isotropically expanding medium is considered in a coordinate system rigidly connected with matter, then the expansion of the Universe is formally reduced to a change in the scale factor of the entire coordinate grid, in the nodes of which galaxies are “planted”. Such a coordinate system is called comoving. The origin of the reference is usually attached to the observer.

There is no single point of view whether the Universe is really infinite or finite in space and volume. However, the observable universe is finite because the speed of light is finite and the Big Bang existed.

Friedman model

Stage	Evolution	Hubble parameter
inflationary
radiation dominance p=ρ/3
dust stage p=const
-dominance

Within the framework of general relativity, the entire dynamics of the universe can be reduced to simple differential equations for the scale factor.

In a homogeneous, isotropic four-dimensional space with constant curvature, the distance between two infinitely close points can be written as follows:

where k takes the value:

• k=0 for 3D plane
• k=1 for 3d sphere
• k=-1 for 3D hypersphere

x - 3D radius vector in quasi-Cartesian coordinates: .

If the expression for the metric is substituted into the GR equations, then we obtain the following system of equations:

• Energy Equation

• Motion equation

• Continuity equation

where Λ is the cosmological constant, ρ is the average density of the Universe, P is the pressure, c is the speed of light.

The given system of equations admits many solutions, depending on the chosen parameters. In fact, the values ​​of the parameters are fixed only at the current moment and evolve over time, so the evolution of the extension is described by a set of solutions.

Explanation of Hubble's law

Suppose there is a source located in the comoving system at a distance r 1 from the observer. The receiving equipment of the observer registers the phase of the incoming wave. Consider two intervals between points with the same phase:

On the other hand, for a light wave in the accepted metric, the following equality holds:

If we integrate this equation and remember that in comoving coordinates r does not depend on time, then, under the condition that the wavelength is small relative to the radius of curvature of the Universe, we obtain the relation:

If we now substitute it into the original ratio:

After expanding the right-hand side into a Taylor series, taking into account the term of the first order of smallness, we obtain a relation that exactly coincides with the Hubble law. Where the constant H takes the form:

ΛCDM

As already mentioned, the Friedmann equations admit many solutions, depending on the parameters. And the modern ΛCDM model is the Friedman model with generally accepted parameters. Usually in the work of observers they are given in terms of critical density:

If we express the left side from the Hubble law, then after reduction we get the following form:

where Ω m =ρ/ρ cr , Ω k = -(kc 2)/(a 2 H 2) , Ω Λ =(8πGΛc 2)/ρ cr . It can be seen from this entry that if Ω m + Ω Λ = 1 , i.e. the total density of matter and dark energy is equal to the critical one, then k = 0 , i.e. the space is flat, if more, then k = 1 , if less than k = -1

In the modern generally accepted model of expansion, the cosmological constant is positive and significantly different from zero, that is, antigravity forces arise on large scales. The nature of such forces is unknown, theoretically such an effect could be explained by the action of the physical vacuum, however, the expected energy density turns out to be many orders of magnitude greater than the energy corresponding to the observed value of the cosmological constant - cosmological constant problem.

The remaining options are currently only of theoretical interest, but this may change with the emergence of new experimental data. The modern history of cosmology already knows such examples: models with a zero cosmological constant dominated unconditionally (apart from a short burst of interest in other models in the 1960s) from the discovery of the cosmological redshift by Hubble until 1998, when data on type Ia supernovae convincingly disproved their.

Further evolution of expansion

The further course of the expansion generally depends on the values ​​of the cosmological constant Λ , space curvature k and the equation of state P(ρ) . However, the evolution of the extension can be estimated qualitatively based on fairly general assumptions.

If the value of the cosmological constant is negative, then only attractive forces act and nothing else. The right side of the energy equation will be non-negative only for finite values ​​of R. This means that at some value of R c the Universe will begin to contract at any value of k and regardless of the form of the equation of state.

If the cosmological constant is equal to zero, then the evolution for a given value of H 0 depends entirely on the initial density of matter:

If , then the expansion continues indefinitely, in the limit with the rate asymptotically tending to zero. If the density is greater than the critical one, then the expansion of the Universe slows down and is replaced by contraction. If less, then the expansion goes on indefinitely with a non-zero limit H.

If Λ>0 and k≤0, then the Universe expands monotonically, but unlike the case with Λ=0, for large values ​​of R, the expansion rate increases:

When k=1, the selected value is . In this case, there exists a value of R for which and , that is, the Universe is static.

For Λ>Λ c, the expansion rate decreases up to a certain moment, and then begins to increase indefinitely. If Λ slightly exceeds Λ c , then for some time the expansion rate remains practically unchanged.

In case Λ<Λ c всё зависит от начального значения R, с которого началось расширения. В зависимости от этого значения Вселенная либо будет расширяться до какого-то размера, а потом сожмётся, либо будет неограниченно расширяться.

The Big Bang Theory (Hot Universe Model)

The Big Bang Theory is the theory of primordial nucleosynthesis. It answers the question - how the chemical elements were formed and why their abundance is exactly the same as it is now observed. It is based on the extrapolation of the laws of nuclear and quantum physics, on the assumption that when moving into the past, the average particle energy (temperature) increases.

The limit of applicability is the region of high energies, above which the studied laws cease to work. At the same time, there is no longer any substance as such, but there is practically pure energy. If we extrapolate Hubble's law to that moment, it turns out that the visible region of the Universe is located in a small volume. Small volume and high energy - a characteristic state of matter after the explosion, hence the name of the theory - the theory of the Big Bang. At the same time, the answer to the question remains beyond the scope: “What caused this explosion and what is its nature?”.

Also, the Big Bang theory predicted and explained the origin of the cosmic microwave background radiation - this is the legacy of the moment when all matter was still ionized and could not resist the pressure of light. In other words, the relict background is the remnant of the "photosphere of the Universe".

Entropy of the Universe

The main argument confirming the theory of the hot Universe is the value of its specific entropy. It is equal to the ratio of the concentration of equilibrium photons n γ to the concentration of baryons n b , up to a numerical coefficient.

Let us express n b in terms of the critical density and the fraction of baryons:

where h 100 is the modern Hubble value, expressed in units of 100 km / (s Mpc), and, given that for the cosmic microwave background with T = 2.73 K

cm −3,

we get:

The reciprocal value is the value of the specific entropy.

First three minutes. Primary nucleosynthesis

Presumably, from the beginning of birth (or at least from the end of the inflationary stage) and during the time until the temperature remains below 10 16 GeV (10 −10 s), all known elementary particles are present, and all of them have no mass. This period is called the period of the Great Unification, when the electroweak and strong interactions are united.

At the moment, it is impossible to say exactly which particles are present at that moment, but something is still known. The value of η is not only an indicator of specific entropy, but also characterizes the excess of particles over antiparticles:

At the moment when the temperature drops below 10 15 GeV, X- and Y-bosons with corresponding masses are likely to be released.

The era of the Great Unification is replaced by the era of the electroweak unification, when the electromagnetic and weak interactions represent a single whole. In this epoch, the annihilation of X- and Y-bosons takes place. At the moment when the temperature drops to 100 GeV, the electroweak unification epoch ends, quarks, leptons and intermediate bosons are formed.

The hadron era is coming, the era of active production and annihilation of hadrons and leptons. In this epoch, the moment of the quark-hadron transition or the moment of quark confinement is noteworthy, when the fusion of quarks into hadrons became possible. At this moment, the temperature is 300-1000 MeV, and the time from the birth of the Universe is 10 −6 s.

The epoch of the hadron era is inherited by the lepton era - at the moment when the temperature drops to the level of 100 MeV, and on the clock 10 −4 s. In this era, the composition of the universe begins to resemble the modern one; the main particles are photons, in addition to them there are only electrons and neutrinos with their antiparticles, as well as protons and neutrons. During this period, one important event occurs: the substance becomes transparent to neutrinos. There is something like a relict background, but for neutrinos. But since the separation of neutrinos occurred before the separation of photons, when some types of particles had not yet annihilated, giving their energy to the rest, they cooled down more. By now, the neutrino gas should have cooled down to 1.9 K if neutrinos have no mass (or their masses are negligible).

At a temperature T≈0.7 MeV, the thermodynamic equilibrium between protons and neutrons, which existed before, is violated and the ratio of the concentration of neutrons and protons freezes at a value of 0.19. The synthesis of nuclei of deuterium, helium, lithium begins. After ~200 seconds after the birth of the Universe, the temperature drops to values ​​at which nucleosynthesis is no longer possible, and the chemical composition of matter remains unchanged until the birth of the first stars.

Problems of the Big Bang Theory

Despite significant advances, the theory of the hot universe faces a number of difficulties. If the Big Bang caused the expansion of the Universe, then in the general case a strong inhomogeneous distribution of matter could arise, which is not observed. The Big Bang theory also does not explain the expansion of the universe, it accepts it as a fact.

The theory also assumes that the ratio of the number of particles and antiparticles at the initial stage was such that it resulted in the modern predominance of matter over antimatter. It can be assumed that at the beginning the Universe was symmetrical - there was an equal amount of matter and antimatter, but then, in order to explain the baryon asymmetry, some mechanism of baryogenesis is needed, which should lead to the possibility of proton decay, which is also not observed.

Various theories of the Grand Unification suggest the birth in the early Universe of a large number of magnetic monopoles, which have not yet been discovered either.

inflation model

The task of inflation theory is to answer the questions left behind by expansion theory and the Big Bang theory: “Why is the universe expanding? And what is the Big Bang? To do this, the expansion is extrapolated to the zero point in time and the entire mass of the Universe is at one point, forming a cosmological singularity, often called the Big Bang. Apparently, the general theory of relativity at that time is no longer applicable, which leads to numerous, but so far, alas, only purely speculative attempts to develop a more general theory (or even “new physics”) that solves this problem of the cosmological singularity.

The main idea of ​​the inflationary stage is that if we drive a scalar field called inflanton, the impact of which is strong in the initial stages (starting from about 10 −42 s), but quickly decreases with time, then the flat geometry of space can be explained, while the Hubble expansion becomes an inertial motion due to the large kinetic energy accumulated during inflation, and the origin from a small initially causally connected region explains the uniformity and isotropy of the Universe.

However, there are a great many ways to set an inflaton, which in turn generates a whole lot of models. But the majority is based on the assumption of slow rolling: the inflanton potential slowly decreases to a value equal to zero. The specific type of potential and the method of setting the initial values ​​depend on the chosen theory.

Theories of inflation are also divided into infinite and finite in time. In a theory with infinite inflation, there are regions of space - domains - that began to expand, but due to quantum fluctuations returned to their original state, in which conditions for repeated inflation arise. Such theories include any theory with infinite potential and Linde's chaotic theory of inflation.

Theories with a finite inflation time include the hybrid model. There are two types of fields in it: the first is responsible for large energies (and hence for the rate of expansion), and the second for small ones, which determine the moment when inflation ends. In this case, quantum fluctuations can affect only the first field, but not the second, and hence the inflation process itself is finite.

The unresolved problems of inflation include temperature jumps in a very wide range, at some point it drops almost to absolute zero. At the end of inflation, the substance is reheated to high temperatures. The role of a possible explanation for such a strange behavior is proposed "parametric resonance".

multiverse

"Multiverse", "Big Universe", "Multiverse", "Hyperuniverse", "Superuniverse", "Multiverse", "Omniverse" - various translations of the English term multiverse. It appeared during the development of the theory of inflation.

Regions of the universe separated by distances greater than the size of the particle horizon evolve independently of each other. Any observer sees only those processes that occur in a domain equal in volume to a sphere with a radius equal to the distance to the particle horizon. In the epoch of inflation, two regions of expansion, separated by a distance of the order of the horizon, do not intersect.

Such domains can be thought of as separate universes like our own: they are similarly uniform and isotropic on large scales. The conglomerate of such formations is the Multiverse.

The chaotic theory of inflation assumes an infinite variety of universes, each of which may have different physical constants from other universes. In another theory, the universes differ in their quantum dimension. By definition, these assumptions cannot be experimentally verified.

Alternatives to inflation theory

The cosmic inflation model is quite successful, but not necessary for the consideration of cosmology. She has opponents, including Roger Penrose. Their argument boils down to the fact that the solutions proposed by the inflationary model leave behind missed details. For example, this theory does not offer any fundamental justification that density perturbations at the pre-inflationary stage should be just so small that an observable degree of homogeneity arises after inflation. The situation is similar with spatial curvature: it greatly decreases during inflation, but nothing prevented it from being so important before inflation that it still manifests itself at the present stage of the development of the Universe. In other words, the problem of initial values ​​is not solved, but only skillfully draped.

As alternatives, exotic theories such as string theory and brane theory, as well as cyclic theory, are proposed. The main idea of ​​these theories is that all the necessary initial values ​​are formed before the Big Bang.

String theory requires adding a few more dimensions to the usual four-dimensional space-time, which would have played a role in the early stage of the Universe, but are now in a compactified state. To the inevitable question why these dimensions are compactified, the following answer is proposed: superstrings have T-duality, in connection with which the string "winds" on additional dimensions, limiting their size.

In brane theory (M-theory), everything starts with a cold, static five-dimensional space-time. The four spatial dimensions are limited by three-dimensional walls or three-branes; one of these walls is the space in which we live, while the second brane is hidden from perception. There is another three-brane "lost" somewhere between the two boundary branes in four-dimensional space. According to the theory, when this brane collides with ours, a large amount of energy is released and thus the conditions for the emergence of the Big Bang are formed.

Cyclic theories postulate that the Big Bang is not unique in its kind, but implies the transition of the Universe from one state to another. Cyclic theories were first proposed in the 1930s. The stumbling block of such theories was the second law of thermodynamics, according to which entropy can only increase. This means that previous cycles would have been much shorter and the matter in them would have been much hotter than at the time of the last Big Bang, which is unlikely. At the moment, there are two theories of a cyclic type that have managed to solve the problem of ever-increasing entropy: the Steinhardt-Turok theory and the Baum-Frampton theory.

The theory of evolution of large-scale structures

The formation and collapse of protogalactic clouds as imagined by an artist.

As the data on the background background show, at the moment of separation of radiation from matter, the Universe was actually homogeneous, the fluctuations of matter were extremely small, and this is a significant problem. The second problem is the cellular structure of superclusters of galaxies and, at the same time, the spherical structure of smaller clusters. Any theory attempting to explain the origin of the large-scale structure of the universe must necessarily solve these two problems (as well as correctly model the morphology of galaxies).

The modern theory of the formation of a large-scale structure, as well as individual galaxies, is called the "hierarchical theory". The essence of the theory is as follows: at first, the galaxies were small in size (about the size of the Magellanic cloud), but over time they merge, forming ever larger galaxies.

Recently, the validity of the theory has been called into question, and downsizing has contributed in no small measure to this. However, in theoretical studies this theory is dominant. The most striking example of such research is Millennium simulation (Millennium run).

General provisions

The classical theory of the origin and evolution of fluctuations in the early Universe is the Jeans theory against the background of the expansion of a homogeneous isotropic Universe:

Where us is the speed of sound in the medium, G is the gravitational constant, and ρ is the density of the unperturbed medium, is the magnitude of the relative fluctuation, Φ is the gravitational potential created by the medium, v is the velocity of the medium, p(x,t) is the local density of the medium, and the consideration takes place in the comoving coordinate system.

The given system of equations can be reduced to one, describing the evolution of inhomogeneities:

where a is the scale factor and k is the wave vector. From it, in particular, it follows that unstable are fluctuations whose size exceeds:

In this case, the perturbation grows linearly or weaker, depending on the evolution of the Hubble parameter and the energy density.

This model adequately describes the collapse of perturbations in a nonrelativistic medium if their size is much smaller than the current event horizon (including for dark matter during the radiation-dominated stage). For the opposite cases, it is necessary to consider the exact relativistic equations. The energy-momentum tensor of an ideal fluid with allowance for small density perturbations

is conserved covariantly, from which the hydrodynamic equations generalized for the relativistic case follow. Together with the GR equations, they represent the original system of equations that determine the evolution of fluctuations in cosmology against the background of Friedman's solution.

Epoch before recombination

The selected moment in the evolution of the large-scale structure of the Universe can be considered the moment of hydrogen recombination. Up to this point, some mechanisms operate, after - completely different ones.

The initial density waves are larger than the event horizon and do not affect the density of matter in the Universe. But as it expands, the size of the horizon is compared with the wavelength of the perturbation, as they say, "the wave leaves the horizon" or "enters the horizon." After that, the process of its expansion is the propagation of a sound wave on an expanding background.

In this epoch, waves with a wavelength of no more than 790 Mpc for the current epoch enter below the horizon. Waves important for the formation of galaxies and their clusters enter at the very beginning of this stage.

At this time, the matter is a multicomponent plasma, in which there are many different effective mechanisms for damping all sound disturbances. Perhaps the most effective among them in cosmology is Silk damping. After all sound perturbations are suppressed, only adiabatic perturbations remain.

For some time, the evolution of ordinary and dark matter goes synchronously, but due to interaction with radiation, the temperature of ordinary matter falls more slowly. There is a kinematic and thermal separation of dark matter and baryonic matter. It is assumed that this moment occurs at 10 5 .

The behavior of the baryon-photon component after separation and up to the end of the radiative stage is described by the equation:

where k is the momentum of the considered wave, η is the conformal time. It follows from his solution that in that epoch the amplitude of perturbations in the density of the baryon component did not increase or decrease, but experienced acoustic oscillations:

At the same time, dark matter did not experience such oscillations, since neither the pressure of light, nor the pressure of baryons and electrons affects it. Moreover, the amplitude of its perturbations grows:

After recombination

After recombination, the pressure of photons and neutrinos on matter is negligible. Consequently, the systems of equations describing perturbations of dark and baryonic matter are similar:

Already from the similarity of the type of equations, one can assume, and then prove, that the difference in fluctuations between dark and baryonic matter tends to a constant. In other words, ordinary matter rolls into potential wells formed by dark matter. The growth of perturbations immediately after recombination is determined by the solution

where C i are constants depending on the initial values. As can be seen from the above, at large times the density fluctuations grow in proportion to the scale factor:

All the perturbation growth rates given in this paragraph and in the previous one grow with the wave number k, therefore, with an initial flat spectrum of perturbations, perturbations of the smallest spatial scales enter the collapse stage earlier, that is, objects with a smaller mass are formed first.

For astronomy, objects with a mass of ~10 5 Mʘ are of interest. The fact is that when dark matter collapses, a protohalo is formed. Hydrogen and helium tending to its center begin to radiate, and at masses less than 10 5 M ʘ , this radiation throws the gas back to the outskirts of the protostructure. At higher masses, the process of formation of the first stars starts.

An important consequence of the initial collapse is that high-mass stars appear, emitting in the hard part of the spectrum. The emitted hard quanta, in turn, meet neutral hydrogen and ionize it. Thus, immediately after the first burst of star formation, secondary ionization of hydrogen occurs.

Dark energy dominance stage

Let us assume that the pressure and density of dark energy does not change with time, that is, it is described by a cosmological constant. Then it follows from the general equations for fluctuations in cosmology that the perturbations evolve as follows:

Taking into account that the potential is inversely proportional to the scale factor a, this means that there is no growth of perturbations and their size is unchanged. This means that the hierarchical theory does not allow structures larger than those currently observed.

In the era of dark energy dominance, two last important events for large-scale structures occur: the appearance of galaxies like the Milky Way - this happens at z~2, and a little later - the formation of clusters and superclusters of galaxies.

Theory problems

Hierarchical theory - logically derived from modern, proven, ideas about the formation of stars and using a large arsenal of mathematical tools, has recently encountered a number of problems, both theoretical and, more importantly, observational in nature:

The biggest theoretical problem lies at the point where the thermodynamics and mechanics are merged: without the introduction of additional non-physical forces, it is impossible to force two dark matter halos to merge.
Voids are formed more likely closer to our time than to recombination, however, recently discovered absolutely empty spaces with dimensions of 300 Mpc come into dissonance with this statement.
Also, giant galaxies are born at the wrong time, their number per unit volume at large z is much larger than what the theory predicts. What's more, it stays the same when theoretically it should grow very fast.
Data on the oldest globular clusters do not want to put up with a burst of star formation of the order of 100Mʘ and prefer stars like our Sun. And this is only a part of the problems that confronted the theory.

If you extrapolate Hubble's law back in time, you end up with a point, a gravitational singularity called the cosmological singularity. This is a big problem, since the entire analytical apparatus of physics becomes useless. And although, following the path of Gamow, proposed in 1946, it is possible to reliably extrapolate until the modern laws of physics are operational, it is not yet possible to accurately determine this moment of the onset of the “new physics”.

The question of the shape of the universe is an important open question in cosmology. Speaking mathematically, we are faced with the problem of finding a three-dimensional topology of the spatial section of the Universe, that is, such a figure that best represents the spatial aspect of the Universe. The general theory of relativity as a local theory cannot give a complete answer to this question, although it also introduces some limitations.

First, it is not known whether the universe is globally spatially flat, that is, whether the laws of Euclidean geometry apply at the largest scales. Currently, most cosmologists believe that the observable universe is very close to spatially flat with local folds where massive objects distort spacetime. This view has been confirmed by the latest WMAP data looking at "acoustic oscillations" in the temperature variations of the CMB.

Secondly, it is not known whether the Universe is simply connected or multiply connected. According to the standard expansion model, the universe has no spatial boundaries, but may be spatially finite. This can be understood by the example of a two-dimensional analogy: the surface of a sphere has no boundaries, but has a limited area, and the curvature of the sphere is constant. If the Universe is really spatially limited, then in some of its models, moving in a straight line in any direction, you can get to the starting point of the journey (in some cases this is impossible due to the evolution of space-time).

Thirdly, there are suggestions that the Universe was originally born rotating. The classical concept of origin is the idea of ​​the isotropy of the Big Bang, that is, the distribution of energy equally in all directions. However, a competing hypothesis emerged and received some confirmation: a group of researchers from the University of Michigan, led by physics professor Michael Longo (Michael Longo), found that the spiral arms of galaxies, twisted counterclockwise, are 7% more common than galaxies with "opposite orientation", which may indicate the presence of the initial moment of rotation of the universe. This hypothesis must also be tested by observations in the Southern Hemisphere.

28.02.1993 15:16 | A. D. Chernin / The Universe and We

The starry sky has occupied the imagination of people at all times. Why do stars light up? How many of them shine at night? Are they far from us? Does the stellar universe have boundaries? Since ancient times, man has thought about this, sought to understand and comprehend the structure of the big world in which he lives.

The earliest ideas of people about the stellar world have been preserved in legends and tales. Centuries and millennia passed before the science of the Universe arose and received a deep substantiation and development, revealing to us the remarkable simplicity and amazing order of the universe. No wonder in ancient Greece the Universe was called Cosmos: this word originally meant order and beauty.

Picture of the world

In an ancient Indian book called the Rigveda, which means "Book of Hymns", one can find one of the earliest descriptions in the history of mankind of the entire universe as a single whole. It contains, first of all, the Earth. It appears as a boundless flat surface - "vast space". This surface is covered from above by the sky - a blue vault dotted with stars. Between heaven and earth - "luminous air".

Very similar to this picture and the early ideas about the world among the ancient Greeks and Romans - also a flat Earth under the dome of the sky.

It was very far from science. But something else is important here. Remarkable and grandiose is the daring goal itself - to embrace the whole Universe with thought. From this originates our confidence that the human mind is able to comprehend, understand, unravel the structure of the Universe, create in its imagination a complete picture of the world.

Celestial Spheres

The scientific picture of the world took shape as the accumulation of the most important knowledge about the Earth, the Sun, the Moon, planets, and stars proceeded.

Back in the VI century. BC. the great mathematician and philosopher of antiquity Pythagoras taught that the Earth is spherical. Evidence of this is, for example, the round shadow of our planet falling on the Moon during lunar eclipses.

Another great scientist of the ancient world, Aristotle, considered the entire Universe to be spherical, spherical. This idea was suggested not only by the rounded appearance of the sky, but also by the circular daily movements of the luminaries. He placed the Earth at the center of his picture of the Universe. Around it are the Sun, the Moon and the then known five planets. Each of these bodies corresponded to its own sphere, circling around our planet. The body is "attached" to its sphere and therefore also moves around the Earth. The most distant sphere, covering all the others, was considered the eighth. Stars are attached to it. She also revolved around the Earth in accordance with the observed daily movement of the sky.

Aristotle believed that celestial bodies, like their spheres, are made of a special "heavenly" material - ether, which does not have the properties of gravity and lightness and performs eternal circular motion in world space.

Such a picture of the world reigned in the minds of people for two millennia - until the era of Copernicus. In the 2nd century AD, this picture was improved by Ptolemy, the famous astronomer and geographer who lived in Alexandria. He gave a detailed mathematical theory of planetary motion. Ptolemy could accurately calculate the apparent positions of the stars - where they are now, where they were before and where they will be later.

True, five spheres were not enough to reproduce all the subtle details of the movement of the planets across the sky. New ones had to be added to the five roundabouts, and the old ones had to be rebuilt. In Ptolemy, each planet participated in several circular motions, and their addition gave the visible movement of the planets across the sky.

Later, in the Middle Ages, Aristotle's doctrine of the celestial spheres, which then became generally accepted, was tried to be developed in a completely different direction. For example, spheres were proposed to be considered crystal. Why? Because, probably, the crystal is transparent and besides, the crystal sphere is beautiful! And yet such additions by no means improved the picture of the universe.

World of Copernicus.

The book of Copernicus, published in the year of his death (1543), bore the modest title "On the Revolutions of the Celestial Spheres". But it was a complete overthrow of the Aristotelian view of the world. The complex colossus of hollow transparent crystal spheres did not immediately recede into the past. Since that time, a new era has begun in our understanding of the Universe. It continues to this day.

Thanks to Copernicus, we have learned that the Sun occupies its proper position in the center of the planetary system. The Earth is not the center of the world, but one of the ordinary planets revolving around the Sun. So everything fell into place. The structure of the solar system was finally unraveled.

Further discoveries of astronomers added to the family of planets. There are nine of them: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In this order, they occupy their orbits around the Sun. Many small bodies of the solar system - asteroids and comets - have been discovered. But this did not change the Copernican picture of the world. On the contrary, all these discoveries only confirm and refine it.

Now we understand that we live on a small planet, similar in shape to a ball. The earth revolves around the sun in an orbit that is not too different from a circle. The radius of this orbit is close to 150 million kilometers.

The distance from the Sun to Saturn - the farthest planet known at the time of Copernicus - is approximately ten times the radius of the earth's orbit. This distance was quite correctly determined by Copernicus. The distance from the Sun to the most distant known planet (Pluto) is still almost four times greater, at about six billion kilometers.

This is the picture of the universe in our immediate environment. This is the world according to Copernicus.

But the solar system is not the whole universe. We can say that this is only our small world. What about distant stars? About them Copernicus did not dare to express any opinion. He simply left them in their original place, on the far sphere where Aristotle had them, and only said - and quite rightly - that the distance to them is many times greater than the size of planetary orbits. Like ancient scientists, he represented the Universe as a closed space, limited by this sphere.

How many stars are in the sky?

Everyone will answer this question: oh, a lot. But still how much - a hundred or a thousand?

Much more, a million or a billion.

This response is often heard.

Indeed, the sight of the starry sky gives us the impression of innumerable stars. As Lomonosov said in a famous poem: "The abyss has opened, the stars are full, there are no number of stars ..."

But in reality, the number of stars visible to the naked eye is not at all so great. If you do not succumb to impressions, but try to count them, it will turn out that even on a clear moonless night, when nothing interferes with observation, a person with sharp eyesight will see no more than two or three thousand twinkling dots in the sky.

In a list compiled in the 2nd century BC. the famous ancient Greek astronomer Hipparchus and later supplemented by Ptolemy, there are 1022 stars. Hevelius, the last astronomer who made such calculations without the help of a telescope, brought their number to 1533.

But already in antiquity, the existence of a large number of stars invisible to the naked eye was suspected. Democritus, the great scientist of antiquity, said that the whitish strip that stretches across the entire sky, which we call the Milky Way, is in reality a combination of the light of many stars invisible individually. Disputes about the structure of the Milky Way have continued for centuries. The decision - in favor of Democritus' conjecture - came in 1610, when Galileo reported the first discoveries made in the sky with a telescope. He wrote with understandable excitement and pride that now it was possible to "make available to the eye stars that have never been visible before and whose number is at least ten times greater than the number of stars known from ancient times."

sun and stars

But this great discovery still left the world of stars mysterious. Are all of them, visible and invisible, really concentrated in a thin spherical layer around the Sun?

Even before the discovery of Galileo, a remarkably bold idea, unexpected for those times, was expressed. It belongs to Giordano Bruno, whose tragic fate is known to all. Bruno put forward the idea that our Sun is one of the stars of the universe. Only one of the great multitude, and not the center of the Universe.

If Copernicus pointed out a place for the Earth - by no means in the center of the world, then Bruno and the Sun deprived of this privilege.

Bruno's idea gave rise to many striking consequences. From it followed an estimate of the distances to the stars. Indeed, the Sun is a star like the others, but only the closest to us. That's why it's so big and bright. And how far should the star be moved to make it look like, for example, the star Sirius? The answer to this question was given by the Dutch astronomer Huygens (1629-1695). He compared the brightness of these two celestial bodies, and this is what it turned out: Sirius is hundreds of thousands of times farther from us than the Sun.

To better imagine how great the distance to the star is, let's say this: a beam of light flying three hundred thousand kilometers in one second takes several years to travel from us to Sirius. Astronomers speak in this case of a distance of several light years. According to modern updated data, the distance to Sirius is 8.7 light years. And the distance from us to the Sun is only 8 1/3 light minutes.

Of course, different stars differ in themselves from the Sun and from each other (this is taken into account in the modern estimate of the distance to Sirius). Therefore, determining the distances to them even now often remains a difficult, sometimes simply unsolvable task for astronomers, although since the time of Huygens many new methods have been invented for this.

Bruno's remarkable idea and Huygens' calculation based on it became a very important step in the science of the Universe. Thanks to this, the boundaries of our knowledge about the world have greatly expanded, they have gone beyond the solar system and reached the stars.

Galaxy

Since the 17th century, the most important goal of astronomers has been the study of the Milky Way - this giant collection of stars that Galileo saw with his telescope. The efforts of many generations of astronomers-observers were aimed at finding out what is the total number of stars in the Milky Way, determining its actual shape and boundaries, and estimating its size. It was only in the 19th century that it was possible to understand that this is a single system that includes all the visible and many more invisible stars. On an equal footing with everyone, this system includes our Sun, and with it the Earth and planets. Moreover, they are located far from the center, but on the outskirts of the Milky Way system.

It took many more decades of careful observations and deep reflections before it was possible to figure out the structure of the Galaxy. So they began to call the star system, which we see from the inside as a strip of the Milky Way. (The word "galaxy" is formed from the modern Greek "galaktos", which means "milky").

It turned out that the Galaxy has a fairly regular structure and shape, despite the apparent raggedness of the Milky Way, the disorder with which, as it seems to us, the stars are scattered across the sky. It consists of a disk, a halo and a crown. As can be seen from the schematic drawing, the disk is like two plates folded at the edges. It is formed by stars that, inside this volume, move in almost circular orbits around the center of the Galaxy.

The diameter of the disk is measured - it is approximately one hundred thousand light years. This means that it takes one hundred thousand years for light to cross the disk from end to end in diameter. And the number of stars in the disk is about one hundred billion.

There are ten times fewer stars in the halo. (The word "halo" means "round".) They fill a slightly flattened spherical volume and move not in circular, but in highly elongated orbits. The planes of these orbits pass through the center of the Galaxy. In different directions they are distributed more or less evenly.

The disk and the halo surrounding it are immersed in the corona. If the radii of the disk and halo are comparable in size, then the radius of the corona is five, and maybe ten times greater. Why maybe"? Because the crown is invisible - no light comes from it. How did astronomers find out about it then?

hidden mass

All bodies in nature create gravity and experience its action. This is what Newton's well-known law says. They learned about the crown not by the light, but by the gravity created by it. It acts on visible stars, on luminous clouds of gas. Observing the movement of these bodies, astronomers discovered that in addition to the disk and halo, something else is acting on them. A detailed study eventually made it possible to discover the corona, which creates additional gravity. It turned out to be very massive - several times larger than the total mass of all the stars included in the disk and halo. Such is the information obtained by the Estonian astronomer J. Einasto and his collaborators at the Tartu Observatory, and then by other astronomers.

Of course, studying the invisible crown is difficult. Because of this, estimates of its size and mass are not yet too accurate. But the main mystery of the crown is different: we do not know what it consists of. We do not know if there are stars in it, even if they are some unusual ones that do not emit light at all.

Now many people assume that its mass does not consist of stars at all, but of elementary particles - for example, neutrinos. These particles have been known to physicists for a long time, but in themselves they also remain mysterious. It is not known about them, one might say, the most important thing: do they have a rest mass, that is, such a mass that a particle has in a state when it is not moving. Many elementary particles (electron, proton, neutron), of which all atoms are composed, have such a mass. But a photon, a particle of light, does not have it. Photons exist only in motion. Neutrinos could serve as material for the corona, but only if they have a rest mass.

It is easy to imagine with what impatience astronomers await news from physics laboratories, where special experiments are being set up to find out whether the neutrino has a rest mass. Theoretical physicists, meanwhile, are considering other variants of elementary particles, not necessarily just neutrinos, which could act as carriers of hidden mass.

star worlds.

By the beginning of our century, the boundaries of the Universe had expanded so much that they included the Galaxy. Many, if not all, thought then that this huge star system is the entire universe.

But in the twenties, the first large telescopes were built, and new unexpected horizons opened up before astronomers. It turned out that the world does not end outside the Galaxy. Billions of star systems, galaxies, both similar to ours and different from it, are scattered here and there across the expanses of the Universe.

Photographs of galaxies taken with the largest telescopes amaze with their beauty and variety of shapes. These are mighty whirlwinds of stellar clouds, and regular balls or ellipsoids; other star systems do not show the correct structure, they are ragged and shapeless. All these types of galaxies - spiral, elliptical, irregular, named after their appearance in photographs, were discovered and described by the American astronomer Edwin Hubble in the 20-30s of our century.

If we could see our Galaxy from the outside and from afar, then it would appear before us completely different from the schematic drawing by which we got acquainted with its structure. We would not see a disk, a halo, or, of course, a corona, which is generally invisible. From great distances, only the brightest stars would be visible. And all of them, as it turned out, are collected in wide bands, which arc out from the central region of the Galaxy. The brightest stars form its spiral pattern. Only this pattern would be distinguishable from afar. Our Galaxy in a picture taken by an astronomer from some other galaxy would look very similar to the Andromeda Nebula, as it appears to us from photographs.

Recent studies have shown that many large galaxies (not only ours) have extended and massive invisible coronas. And this is very important: after all, if so, then, in general, almost the entire mass of the Universe, or, in any case, its overwhelming part, is a mysterious, invisible, but gravitating "hidden" mass.

Chains and voids

Many, and perhaps almost all galaxies are collected in various collectives, which are called groups, clusters and superclusters - depending on how many there are. A group may include only 3 or 4 galaxies, and a supercluster may contain tens of thousands. Our Galaxy, the Andromeda Nebula and more than a thousand of the same objects are included in the Local Supercluster. It does not have a clearly defined shape and generally looks rather flattened.

Approximately the same look and other superclusters, lying far from us, but quite clearly distinguishable with modern large telescopes.

Until recently, astronomers believed that superclusters were the largest formations in the universe and that there were simply no other large systems. It turned out, however, that this was not the case.

A few years ago, astronomers made an amazing map of the universe. On it, each galaxy is represented by just a dot. At first glance, they are randomly scattered on the map. If you look closely, you can find groups, clusters and superclusters, the latter being represented by chains of points. The map reveals that some of these chains connect and intersect, forming some kind of mesh or honeycomb pattern, reminiscent of lace or maybe a honeycomb with a cell size of 100-300 million light years.

Whether such "grids" cover the entire universe remains to be seen. But several individual cells outlined by superclusters have been studied in detail. There are almost no galaxies inside them, all of them are collected in "walls", limiting huge voids, which are now called "voids" (ie "voids").

Cell and void are tentative working names for the largest formation in the universe. Larger systems in nature are unknown to us. Therefore, we can say that scientists have now solved one of the most ambitious tasks of astronomy - the entire sequence or, as they say, the hierarchy of astronomical systems, is now completely known.

Universe

More than anything else, the Universe itself, embracing and including all the planets, stars, galaxies, clusters, superclusters and cells with voids. The range of modern telescopes reaches several billion light years. This is the size of the observable universe.

All celestial bodies and systems amaze with a variety of properties, complexity of structure. And how is the whole Universe arranged, the Universe as a whole? It turns out that it is extremely monotonous and simple!

Its main property is uniformity. This can be said even more precisely. Let us imagine that we have mentally singled out in the Universe a very large cubic volume with an edge, say, of five hundred million light years. Let's calculate how many galaxies are in it. Let's make the same calculations for other, but equally gigantic volumes located in different parts of the Universe. If all this is done and the results are compared, it turns out that each of them, no matter where they are taken, contains the same number of galaxies. The same will happen when counting clusters and even cells.

So, if we ignore such "details" as clusters, superclusters, cells, and look at the Universe more broadly, mentally covering the whole multitude of stellar worlds at once, then it will appear to us everywhere the same - "solid" and homogeneous.

You can't think of a simpler device. I must say that people have long suspected this. For example, the remarkable thinker Pascal (1623-1662) said that the world is a circle, the center of which is everywhere, and the circumference is nowhere. So with the help of a visual geometric image, he spoke about the homogeneity of the world.

In a homogeneous world, all "places" can be said to have equal rights, and any of them can claim to be the Center of the world. And if so, it means that no center of the world exists at all.

Extension

The Universe also has one more important property, but no one guessed about it until the end of the 20s of our century. The universe is in motion - it is expanding. The distance between clusters and superclusters is constantly increasing. They seem to run away from each other. And the mesh network is stretched.

At all times, people preferred to consider the Universe eternal and unchanging. This point of view prevailed until the 1920s. It was believed that the Universe is limited by the size of our Galaxy. And although individual stars in the Milky Way can be born and die, the Galaxy still remains the same - just as a forest remains unchanged, in which trees are replaced generation after generation.

A real revolution in the science of the universe was made in 1922-24. work of the Petersburg mathematician Alexander Alexandrovich Fridman. Based on the general theory of relativity just created by Einstein, he mathematically proved that the world is not something frozen and unchanging. As a whole, he lives his dynamic life, changes in time, expanding or contracting according to strictly defined laws.

Friedman discovered the non-stationarity of the Universe. It was a theoretical prediction. It was possible to finally decide whether the Universe is expanding or contracting only on the basis of astronomical observations. Such observations in 1928-29. managed to do the Hubble.

He discovered that distant galaxies and their entire collectives scatter from us in all directions. According to Friedman's predictions, this is exactly what the general expansion of the universe should look like.

If the universe is expanding, then clusters and superclusters were closer together in the distant past. Moreover, it follows from Friedman's theory that 15-20 billion years ago, neither stars nor galaxies existed yet, and all matter was mixed and compressed to a colossal density. This substance then had a monstrously high temperature.

Big Bang

The hypothesis of the high temperature of cosmic matter in that distant era was put forward by Georgy Antonovich Gamov (1904-1968), who began his studies in cosmology at the Leningrad University under the guidance of Professor A. A. Fridman. Gamow argued that the expansion of the universe began with the Big Bang, which occurred simultaneously and everywhere in the world. The big bang filled space with hot matter and radiation.

The original goal of Gamow's research was to elucidate the origin of the chemical elements that make up all the bodies in the universe - galaxies, stars, planets and ourselves.

Astronomers have long established that the most common element in the universe is hydrogen, number one on the periodic table. It accounts for approximately 3/4 of the entire "ordinary" (not hidden) matter of the Universe. About 1/4 is helium (element N2), and all other elements (carbon, oxygen, calcium, silicon, iron, etc.) account for very little, up to 2% (by mass). This is the chemical composition of the Sun and most stars.

How did the universal chemical composition of cosmic matter develop, how did the "standard" ratio between hydrogen and helium arise in the first place?

In search of an answer to this question, astronomers and physicists first turned to the stellar interior, where the reactions of transformation of atomic nuclei proceed intensively. Soon, however, it became clear that under the conditions that exist in the central regions of stars like the Sun, no elements heavier than helium can be formed in any significant quantities.

But what if the chemical elements appeared not in the stars, but immediately in the entire Universe at the very first stages of cosmological expansion? The versatility of the chemical composition is automatically ensured. As for the physical conditions, in the early Universe the matter was undoubtedly very dense, in any case, much denser than in the interiors of stars. The high density guaranteed by Friedman's cosmology is an indispensable condition for the occurrence of nuclear reactions for the synthesis of elements. These reactions also require a high temperature of the substance. The early Universe was, according to Gamow's idea, the "cauldron" in which the synthesis of all chemical elements took place.

As a result of a large multi-year collective activity of scientists from different countries, initiated by Gamow, in the 40-60s. it became obvious that the cosmic abundance of the two main elements - hydrogen and helium - can indeed be explained by nuclear reactions in the hot matter of the early Universe. Heavier elements should, apparently, be synthesized in a different way (during bursts of supernovae).

Synthesis of elements is possible, as already mentioned, only at high temperatures; but in a heated substance, according to the general laws of thermodynamics, there must always be radiation, which is in thermal equilibrium with it. After the epoch of nucleosynthesis (which, by the way, lasted only a few minutes), the radiation does not disappear anywhere and continues to move along with matter in the course of the general evolution of the expanding Universe. It should be preserved to the present epoch, only its temperature should be - due to significant expansion - much lower than at the beginning. Such radiation should create a general sky background in the range of short radio waves.

The discovery in 1965 of the cosmic radio emission predicted by this theory became a major event in the entire science of nature, a real triumph of Friedmann-Gamow cosmology. This was the most important observational discovery in cosmology since the discovery of the general recession of galaxies.

How galaxies formed

Observations have shown that cosmic radiation comes to us from all directions in space extremely uniformly. This fact has been established with record-breaking accuracy for cosmology: up to hundredths of a percent. It is with such precision that one can now speak about the general uniformity, the homogeneity of the Universe itself as a whole.

So, the observations reliably confirmed not only the idea of ​​the hot beginning of the Universe, but also the ideas about the geometrical properties of the world embedded in cosmology.

But that's not all. Quite recently, very weak, less than a thousandth of a percent, deviations from complete and ideal uniformity were found in the cosmic background. Cosmologists rejoiced at this discovery almost more than once upon the discovery of radiation itself. It was a welcome discovery.

For a long time, theorists predicted that small "ripples" should exist in cosmic radiation, which arose in it in the early times of the life of the Universe, when there were no stars or galaxies in it yet. Instead of them, there were only very weak concentrations of matter, from which modern star systems were subsequently "born". These concentrations gradually condensed due to their own gravity and at a certain epoch were able to "disconnect" from the general cosmological expansion. After that, they turned into observable galaxies, their groups, clusters and superclusters. The presence of pre-galactic irregularities in the early Universe left its distinct imprint on the cosmic radiation background: because of them, it cannot be perfectly uniform, which was discovered in 1992 (see "Astronomy News" on page 14 - Ed).

This was reported by two groups of astronomers-observers - from the Institute for Space Research in Moscow and from the Goddard Space Center near Washington. Their research was carried out on orbital stations equipped with special very sensitive radio wave receivers. Cosmic radiation, predicted by Gamow, thus rendered a new service to astronomy.

The hidden masses, it must be assumed, were also born in a single grandiose event of the Big Bang. They gathered into future coronas, inside which the "ordinary" matter continued to shrink and disintegrated into relatively small but dense fragments - gas clouds. Those, in turn, continued to shrink even more under the influence of their own gravity and split into protostars, which eventually turned into stars when thermonuclear reactions “turned on” in their densest and hottest regions.

The release of high energy in the reactions of the conversion of hydrogen into helium, and then into heavier elements, is the source of luminosity of both the very first stars and the stars of subsequent generations. Now astronomers can directly observe the birth of young stars in the disk of the Galaxy: it is happening before our eyes. The physical nature of the stars, the reason why these physical bodies radiate their light, and even their very origin, is no longer an unsolvable mystery.

Why is it expanding?

Much more difficult is science advancing in the study of the early, pre-stellar, pre-galactic stages of the evolution of the world, which cannot be observed directly. Cosmic background radiation has told us a lot about the past of the Universe. But the main questions of cosmology remain open. This is primarily a question about the cause of the general expansion of matter, which lasts 15-20 billion years.

So far, one can only build hypotheses, put forward theoretical assumptions, and make guesses about the physical nature of this most grandiose natural phenomenon. One such hypothesis has now won a large number of enthusiastic supporters.

Its initial idea is that at the very beginning of the Universe, even before the era of nucleosynthesis, the world was dominated not by universal gravitation, but by universal antigravitation. The general theory of relativity, on which cosmology is built, does not in principle exclude such a possibility. This idea was, in essence, as if prompted by Einstein himself many years ago.

If such an idea is accepted, then it is not difficult to guess that due to antigravity, all bodies in the world should not attract, but, on the contrary, repel and scatter from each other. This expansion does not stop and continues by inertia even after the anti-gravity is replaced at some point by the universal gravitation familiar to us.

This bright and fruitful hypothesis is now being actively developed theoretically, but it still needs to pass a rigorous observational test in order to turn into a convincing concept, if successful, as it happened earlier with the theories of Friedman and Gamow. In the meantime, this is just one of the curious areas of scientific research in cosmology. The answer to the most amazing mysteries of the Big Universe is yet to come.

And its characteristic features, as well as the exact structure and organization of the Universe, give us reason to assume that for someone is worth it. Book - Think and Grow Rich!

Our awe inspiring universe

For thousands of years, people have admired the starry sky. On a clear night, the beautiful stars stand out like sparkling gems against the black
outer space background. Night in all its beauty floods the earth with moonlight.

People who think about such a spectacle often have questions: “What, after all, is there, in space? How does it all work? Can we find out how all this came about? The answers to these questions will undoubtedly help explain why the Earth and all life on it appeared and what the future holds.

Centuries ago, it was believed that the universe consisted of several thousand stars that were visible to the naked eye. But now, thanks to powerful instruments that carefully scan the sky, scientists know that there are many more.

In fact, what can be seen today is much more awe-inspiring than anyone could have imagined before. Immeasurable
the scale and complexity of it all stagger the human imagination.

According to National Geographic magazine, the knowledge of the universe that man is currently acquiring "stuns him."

Awe inspiring dimensions

In previous centuries, astronomers who scanned the sky with early telescopes noticed some kind of obscure cloud-like formations.

They suggested that these are nearby gas clouds. But in the 1920s, when larger and more powerful telescopes began to be used, these "gases" turned out to be a much larger and more significant phenomenon - galaxies.

A galaxy is a huge collection of stars, gases, and other matter revolving around a central core. The galaxies have been called island universes because each one resembles a universe in itself.

Consider, for example, a galaxy called the Milky Way in which we live. Our solar system, that is, the Sun, Earth and other planets with their satellites, is part of this galaxy. But it is only a tiny part of it, since our Milky Way consists of more than 100
billion stars!

Some scientists suggest that there are at least 200 to 400 billion stars. One science editor even stated: “It is possible that in the Milky
The path contains between five and ten trillion stars.”

The diameter of our Galaxy is so great that even if you could move at the speed of light (299,793 kilometers per second), it would take you 100,000 years to cross it! How many kilometers is this?

Since light travels about ten trillion (10000000000000) kilometers in a year, you get the answer by multiplying this number by 100,000: diameter
Our Milky Way is approximately one quintillion (1000000000000000000) kilometers!

The average distance between stars within our galaxy is estimated to be about six light years, or about 60 trillion kilometers.

Such dimensions and distances are almost impossible to grasp by the human mind. And yet our Galaxy is only the beginning of what is in outer space! There is something even more amazing: so many galaxies have been discovered so far that they are now considered "as ordinary as blades of grass in a meadow."

There are about ten billion galaxies within the visible universe! But beyond the sight of modern telescopes, there is much more. Some astronomers believe that the universe has 100 billion galaxies! And each galaxy can be made up of hundreds of billions of stars!

clusters of galaxies

But that is not all. These awe inspiring galaxies are not randomly scattered in outer space. On the contrary, they tend to be arranged in certain groups, so-called clusters, like berries in a bunch of grapes. Thousands of these galaxy clusters have already been observed and photographed.

Some clusters contain relatively few galaxies. The Milky Way, for example, is part of a cluster of about twenty galaxies.

As part of this local group, there is one "neighboring" galaxy to us, which can be seen on a clear night without a telescope. We are talking about the Andromeda Galaxy, which, like our Galaxy, has a spiral structure.

Other clusters of galaxies consist of many tens and possibly hundreds or even thousands of galaxies. It is estimated that one such cluster contains about 10,000 galaxies!

The distance between galaxies within a cluster can average one million light-years. However, the distance from one cluster of galaxies to another can be a hundred times greater. And there is even evidence that the clusters themselves are located in "super clusters", like brushes on a vine. What colossal dimensions and what a brilliant organization!

Similar organization

Returning back to our solar system, we find a similar, superbly organized arrangement. The sun is a medium-sized star -
is the “core” around which the Earth and other planets move along with their satellites in precisely defined orbits.

Year after year, they turn around with such mathematical inevitability that astronomers can accurately predict where they will be at any given moment.

We find the same precision when looking at the infinitely small world of atoms. The atom is a marvel of order, like a miniature solar system. An atom consists of a nucleus made up of protons and neutrons, and tiny electrons that surround this nucleus. All matter is made up of these building blocks.
details.

One substance differs from another in the number of protons and neutrons in the nucleus, as well as in the number and arrangement of electrons revolving around it. In all this, an ideal order can be traced, since all the elements of which matter is composed can be brought into a neat system, according to the available number of these building details.

What explains this organization?

As we have noted, the size of the universe is truly awe-inspiring. The same can be said about her wonderful device. From the immensely large to the infinitely small, from galaxy clusters to atoms, the universe is characterized by excellent organization everywhere.

Discover magazine stated: “We have experienced order with surprise, and our cosmologists and physicists continue to find new, surprising facets of this order ...

We used to say it was a miracle, and we still allow ourselves to talk about the entire universe as a miracle.” The orderly structure is confirmed even by the use of the word used in astronomy to designate the universe: "cosmos."

In one reference manual, this word is defined as "a well-ordered, organized system, as opposed to chaos, a disorderly heap of matter."

Former astronaut John Glenn drew attention to the "order in the entire universe around us" and the fact that galaxies "all move in
established orbits in a certain ratio to each other.

So he asked, “Could it just happen by chance? Was it
by chance that drifting objects suddenly began to move along these orbits on their own?

His conclusion was, "I can't believe it... Some Power has brought all these things into orbit and is keeping them there."

Indeed, the universe is so precisely organized that man can use the heavenly bodies as a basis for measuring time. But any
a well-designed watch is obviously the product of an orderly thinking mind capable of design. Orderly
a thinking mind capable of constructing can only be possessed by a rational person.

How, then, to consider the much more sophisticated design and reliability found throughout the universe? Does it indicate
also this is for the designer, for the creator, for the idea - for the intellect? And do you have any reason to believe that the intellect can exist separately from the personality?

One thing we can't help but recognize is that a great organization requires a great organizer. In our life experience there is not a single
a case that would testify to the accidental occurrence of something organized. On the contrary, all our life experience shows that any organization must have an organizer.

Every machine, computer, building, even a pencil and piece of paper had a manufacturer, an organizer. Logically, the much more complex and awe-inspiring organization of the universe must also have had an organizer.

The law requires a legislator

In addition, the entire universe, from atoms to galaxies, is governed by certain physical laws. For example, there are laws governing heat, light, sound, and gravity.

Physicist Stephen W. Hawking said: “The more we explore the universe, the clearer it becomes that it is not at all random, but obeys certain well-established laws that operate in various areas.

The assumption that there are some universal principles, so that all laws are part of some larger law, seems quite reasonable.

Rocket specialist Wernher von Braun went even further when he declared: “The laws of nature in the universe are so precise that we have no difficulty with
building a spacecraft to go to the moon, and we can time the flight to the nearest fraction of a second.

These laws had to be established by someone." Scientists who wish to successfully launch a rocket into orbit around the Earth or the Moon must act in accordance with these universal laws.

When we think about laws, we realize that they must come from the legislature. Behind the stop sign is clearly the person or group of people who made this law.

What, then, can be said about the all-encompassing laws that govern the material universe? Such brilliantly calculated laws undoubtedly testify to a highly intelligent legislator.

Organizer and Legislator

After a comment about the many special conditions in the universe that are so obvious in order and regularity, in the journal Science News
(Science News) noted: “Thinking about this disturbs cosmologists, because it seems that such exceptional and precise conditions could hardly have been created by chance.

One way to solve this problem is to assume that everything was invented and attribute it to God's Providence.

Many individuals, including many scientists, are reluctant to admit this possibility. But others are ready to admit what the facts persistently convince of - reason. They recognize that such colossal size, precision, and regularity, found throughout the universe, could never have been formed simply by chance. All this must be the result of activity beyond the mind.

This is the conclusion expressed by one of the writers of the Bible, who said regarding the material heavens: “Lift up your eyes to the height of the heavens, and see who created them? Who brings out the host by their count? He calls them all by name. “He” is none other than “the one who made the heavens and their expanse” (Isaiah 40:26; 42:5).

Energy source

Existing matter is subject to universal laws. But where did all this matter come from? In the book Cosmos (Cosmos), Carl Sagan says: “In the beginning
there were no galaxies, no stars or planets, no life or civilizations in the existence of this universe.”

He calls the transition from this state to the modern universe "the most impressive transformation of matter and energy that we have had the honor to imagine."

This is the key to understanding how the universe could begin to exist: there must have been a transformation of energy and matter.

This relationship is confirmed by Einstein's famous formula E=mc2 (energy equals mass times the square of the speed of light). From this formula
the conclusion follows that matter can be created from energy, just as colossal energy can be obtained from matter.

The proof of the latter was the atomic bomb. Therefore, astrophysicist Josip Kleczek stated: “Most of the elementary particles, and possibly all
they can be created by materializing energy.”

Therefore, the assumption that a source of unlimited energy would possess the source material for creating the matter of the universe has scientific proof.

A previously cited Bible writer noted that this source of energy is a living, thinking person, saying: “According to the multitude of power and
nothing (none of the heavenly bodies) drops out of His great power.

Thus, from a biblical point of view, behind what is described in Genesis 1:1 with the words: “In the beginning God created the heavens and the earth,” lies this source
inexhaustible energy.

The beginning was not chaotic

Scientists now generally accept that the universe had a beginning. One well-known theory that attempts to describe this beginning is called the "Big Bang" theory. "Almost all recent discussions about the origin of the universe are based on the theory" "" - says Francis Crick.

Jastrov speaks of this cosmic "explosion" as a "literal moment of creation." Scientists, as astrophysicist John Gribbin admitted in New
Scientist (New Scientist), "claim that they are, by and large, able to describe in some detail" what happened after this "moment", but according to
the reason for this "moment of creation" remains a mystery.

“It is possible that God did it after all,” he remarked in thought.

However, most scientists are unwilling to associate this "moment" with God. Therefore, an "explosion" is usually described as something chaotic, like an explosion.
atomic bomb. But does such an explosion lead to an improvement in the organization of anything? Do bombs dropped on cities during
wars, superbly constructed buildings, streets and road signs?

On the contrary, such explosions cause death, confusion, chaos and destruction. And when a nuclear weapon explodes, the disorganization is total, like
this was experienced in 1945 by the Japanese cities of Hiroshima and Nagasaki.

No, a simple "explosion" could not create our awe-inspiring universe with its amazing order, purposeful structure and laws.

Only a mighty organizer and legislator could direct the enormous active forces in such a way that a magnificent organization and excellent laws would result.

Therefore, scientific data and logic provide a solid foundation for the following Bible statement: “The heavens declare the glory of God, and the expanse speaks of the work of his hands” (Psalm 18:2).

So the Bible comes to grips with questions that evolutionary theory has not been able to answer conclusively. Instead of leaving us in the dark about what lies behind the origin of everything, the Bible gives us a simple and clear answer.

It confirms scientific as well as our own observations that nothing is created by itself.

Although we were not personally present when the universe was erected, it is obvious that this required a master designer, according to the reasoning of the Bible: “Every house is built by someone; but it is God who made all things” (Hebrews 3:4).

MOSCOW, June 15 - RIA Novosti. The Universe could only be born as a result of the Big Bang, since all alternative scenarios for its formation lead to the immediate collapse of the newborn Universe and its destruction, according to an article published in the journal Physical Review D.

“All these theories were developed in order to explain the initial “smooth” structure of the Universe at the moment of its birth and to “grope” for the primary conditions for its formation. We have shown that in fact they generate the opposite picture - powerful disturbances arise in them, which, in ultimately lead to the collapse of the entire system," write Jean-Luc Lehners from the Institute for Gravitational Physics in Potsdam (Germany) and his colleagues.

Most cosmologists believe that the Universe was born from a singularity that began to expand rapidly in the first moments after the Big Bang. Another group of astrophysicists believes that the birth of our Universe was preceded by the death of its "progenitor", which probably happened during the so-called "Big Rip".

The main problem of these theories is that they are incompatible with the theory of relativity - at the moment when the Universe was a dimensionless point, it should have had infinite energy density and space curvature, and powerful quantum fluctuations should have arisen inside it, which is impossible from the point vision of Einstein's brainchild.

To solve this problem, scientists have developed in the past 30 years several alternative theories in which the Universe is born in other, less extreme conditions. For example, Stephen Hawking and James Hartle suggested 30 years ago that the Universe was a point not only in space, but also in time, and before its birth, time, in our understanding of the word, simply did not exist. When time appeared, the space was already relatively "flat" and homogeneous so that a "normal" Universe with "classical" laws of physics could arise.

In turn, the Soviet-American physicist Alexander Vilenkin believes that our Universe is a kind of "bubble" of false vacuum inside the eternal and constantly expanding giant multi-universe, where such bubbles constantly arise as a result of quantum fluctuations in vacuum, literally being born from nothing.

Both of these theories avoid the issue of the "beginning of time" and the incompatibility of the conditions of the Big Bang with Einsteinian physics, but at the same time they raise a new question - are such variants of the expansion of the Universe capable of generating it in the form in which it now exists?

As the calculations of Leners and his colleagues show, in fact, such scenarios for the birth of the Universe cannot work in principle. In most cases, they do not lead to the birth of a "flat" and calm Universe, similar to ours, but to the appearance of powerful perturbations in its structure, which will make such "alternative" Universes unstable. Moreover, the probability of the birth of such an unstable universe is much higher than its stable counterparts, which calls into question the ideas of Hawking and Vilenkin.

Accordingly, the Big Bang cannot be avoided - scientists, Lehners and his colleagues conclude, will have to find a way to reconcile quantum mechanics and relativity theory, as well as understand how quantum fluctuations were suppressed by extremely high matter density and space-time curvature.