Relict radiation- cosmic electromagnetic radiation with a high degree of isotropy and with a spectrum characteristic of an absolutely black body with temperature? 2.725 K... The relic radiation was predicted by G. Gamow, R. Alfer and R. Herman in 1948 on the basis of the first theory of the Big Bang they created. Alfer and Herman were able to establish that the temperature of the relic radiation should be 5 K, and Gamow gave a prediction at 3 K... Although some estimates of space temperature existed before, they had several drawbacks. First, these were measurements of only the effective temperature of space; it was not assumed that the radiation spectrum obeys Planck's law. Second, they were dependent on our particular location at the edge of the Galaxy and did not assume that the radiation was isotropic. Moreover, they would give completely different results if the Earth were somewhere else in the universe. Neither G. Gamow himself, nor many of his followers raised the question of the experimental detection of relic radiation. Apparently, they believed that this radiation could not be detected, since it "drowns" in the streams of energy brought to earth by the radiation of stars and cosmic rays.

The possibility of detecting relict radiation against the background of radiation from galaxies and stars in the region of centimeter radio waves was substantiated by the calculations of A.G. Doroshkevich and I.D. Novikov, performed at the suggestion of Ya.B. Zeldovich in 1964, i.e. a year before the discovery of A. Pepsias and R. Wilson.

In 1965, Arno Penzias and Robert Woodrow Wilson built the Dicke radiometer, which they intended to use not for searching for relic radiation, but for experiments in radio astronomy and satellite communications. When calibrating the device, it turned out that the antenna has an excess temperature of 3.5 Kwhich they couldn't explain. A small background noise did not change either from the direction or from the time of operation. At first they decided that this was the noise inherent in the equipment. The radio telescope was dismantled, its "stuffing" was tested again and again. The engineers' pride was hurt, and therefore the check went to the last detail, to the last soldering. Eliminated everything. Collected again - the noise resumed. After much thought, theorists came to the conclusion that this radiation could be nothing more than a constant background of cosmic radio emission that fills the Universe with an even stream. On receiving a call from Holdmdale, Dikke wittily remarked, "We hit the jackpot, guys." A meeting between the teams from Princeton and Holmdale determined that this antenna temperature was caused by the CMB. Astrophysicists have calculated that the noise corresponds to a temperature of about 3 degrees Kelvin, and “is heard at different frequencies. In 1978, Penzias and Wilson received Nobel Prize for their discovery. One can imagine how the supporters of the "hot" model rejoiced when this message arrived. This discovery not only strengthened the position of the "hot" model. The relic radiation allowed from the quasar time step (8-10 billion years) to descend to the step corresponding to 300 thousand years from the very "beginning". At the same time, the idea was confirmed that the Universe once had a density a billion times higher than it is now. It is known that heated matter always emits photons. According to the general laws of thermodynamics, this manifests a tendency towards equilibrium state, at which saturation is achieved: the production of new photons is compensated by the reverse process, the absorption of photons by matter, so that the total number of photons in the medium does not change. This "photon gas" uniformly fills the entire Universe. The temperature of the gas of photons is close to absolute zero - about 3 kelvin, but the energy contained in it is greater than the light energy emitted by all stars during their lifetime. For every cubic centimeter of space in the Universe there are approximately five hundred quanta of radiation, and the total number of photons within the visible Universe is several billion times greater than the total number of particles of matter, i.e. atoms, nuclei, electrons that make up planets, stars and galaxies. This general background radiation of the Universe is called with a light hand by I.S. Shklovsky, relict, i.e. residual, which is a remnant, a relic of the dense and hot initial state of the Universe. Assuming that the matter of the early Universe was hot, G. Gamow predicted that the photons, which were then in thermodynamic equilibrium with matter, should be preserved in the modern era. These photons were directly detected in 1965. Having experienced general expansion and the associated cooling, the photon gas now forms the background radiation of the Universe, coming to us uniformly from all directions. A quantum of relic radiation has no rest mass, like any quantum of electromagnetic radiation, but it has energy, and therefore, according to the famous formula of Einstein E \u003d Ms?, and a mass corresponding to this energy. For most relict quanta, this mass is very small: much less than the mass of the hydrogen atom, the most abundant element in stars and galaxies. Therefore, despite a significant predominance in the number of particles, the relic radiation is inferior to stars and galaxies in terms of its contribution to the total mass of the Universe. In the modern era, the radiation density is 3 * 10 -34 g / cm 3, which is approximately a thousand times less than the average density of the matter of galaxies. But this was not always the case - in the distant past of the Universe, photons made the main contribution to its density. The point is that in the course of cosmological expansion, the radiation density decreases faster than the density of matter. In this process, not only the concentration of photons decreases (at the same rate as the concentration of particles), but the average energy of one photon also decreases, since the temperature of the photon gas decreases during expansion. In the course of the subsequent expansion of the Universe, the temperature of the plasma and radiation dropped. The interaction of particles with photons no longer had time to noticeably affect the emission spectrum during the characteristic expansion time. However, even in the complete absence of interaction of radiation with matter during the expansion of the Universe, the blackbody spectrum of radiation remains blackbody, only the radiation temperature decreases. While the temperature was over 4000 K, the primary matter was completely ionized, the range of photons from one scattering event to another was much less than the horizon of the Universe. When T ? 4000Kthere was a recombination of protons and electrons, the plasma turned into a mixture of neutral hydrogen and helium atoms, the Universe became completely transparent to radiation. In the course of its further expansion, the radiation temperature continued to fall, but the blackbody nature of the radiation was preserved as a relic, as a "memory" of early period evolution of the world. This radiation was first detected at 7.35 cm, and then at other waves (from 0.6 mm to 50 cm).

No stars and radio galaxies, no hot intergalactic gas, no re-radiation visible light interstellar dust cannot produce radiation approaching the properties of the microwave background radiation: the total energy of this radiation is too high, and its spectrum does not resemble either the spectrum of stars or the spectrum of radio sources. This, as well as the almost complete absence of intensity fluctuations over celestial sphere (small-scale angular fluctuations) the cosmological, relict origin of the microwave background radiation is proved.

The background radiation is isotropic only in the coordinate system associated with the "scattering" galaxies, so-called. accompanying frame of reference (this frame expands with the Universe). In any other coordinate system, the radiation intensity depends on the direction. This fact opens up the possibility of measuring the speed of the Sun's motion relative to the coordinate system associated with the microwave background radiation. Indeed, due to the Doppler effect, the photons propagating towards the moving observer have a higher energy than those that catch up with him, despite the fact that in the system associated with the m.f. and., their energies are equal. Therefore, the radiation temperature for such an observer turns out to be direction-dependent. Dipole anisotropy of the CMB associated with motion Solar system relative to the field of this radiation, by now it has been firmly established: in the direction to the constellation Leo, the temperature of the relic radiation is 3.5 mK higher than the average, and in the opposite direction (constellation Aquarius) by the same amount below the average. Consequently, the Sun (together with the Earth) moves relative to the m.f. and. at a speed of about 400 km / s towards the constellation Leo. The accuracy of the observations is so high that the experimenters record the speed of the Earth's motion around the Sun at 30 km / s. Taking into account the speed of the Sun's movement around the center of the Galaxy allows one to determine the speed of the Galaxy's movement relative to the background radiation.It is ≈600 km / s. A far infrared spectrophotometer (FIRAS) on the NASA Cosmic Background Explorer (COBE) satellite has accurately measured the CMB spectrum. These measurements have become the most accurate blackbody spectrum measurements to date. Most detailed map relic radiation was built as a result of the work of the American spacecraft WMAP.

The spectrum of the relict radiation filling the Universe corresponds to the emission spectrum of an absolutely black body with a temperature of 2.725 K... Its maximum is at 160.4 GHz, which corresponds to a wavelength of 1.9 mm. It is isotropic to within 0.001% - the rms temperature deviation is approximately 18 μK. This value does not take into account the dipole anisotropy (the difference between the coldest and hottest regions is 6.706 mK) caused by the Doppler shift of the radiation frequency due to our own speed relative to the relic radiation coordinate system. The dipole anisotropy corresponds to the motion of the solar system towards the constellation Virgo with a speed of? 370 km / s.

The discovery of the cosmic microwave background radiation

Foreword

RELICT RADIATION, cosmic electromagnetic radiation arriving at the Earth from all sides of the sky with approximately the same intensity and having a spectrum characteristic of blackbody radiation at a temperature of about 3 K (3 degrees Kelvin, which corresponds to –270 ° C). At this temperature, the bulk of the radiation falls on centimeter and millimeter-wave radio waves. The energy density of the relic radiation is 0.25 eV / cm3. Experimental radio astronomers prefer to call this radiation "Cosmic microwave background radiation" (M. f. And.) cosmic microwave background, CMB). Astrophysicists-theorists often call it "Relict radiation" (the term was proposed by the Russian astrophysicist I.S. early stage expansion of our world, when its substance was practically homogeneous and very hot. In what follows, we will call this radiation "relict". The discovery in 1965 of the CMB was of great importance for cosmology; it became one of the most important achievements of natural science in the twentieth century and, undoubtedly, the most important for cosmology after the discovery of redshift in the spectra of galaxies. Weak relic radiation brings us information about the first moments of the existence of our Universe, about that distant epoch when the entire Universe was hot and there were no planets, stars or galaxies in it. Detailed measurements of this radiation carried out in recent years with the help of ground-based, stratospheric and space observatories open the veil over the mystery of the very birth of the Universe.

The discovery of the background radiation

In 1960, an antenna was built in Crawford Hill, Holmdel (NJ, USA) to receive radio signals reflected from the Echo balloon satellite. By 1963, this antenna was no longer needed to operate a satellite, and radio physicists Robert Woodrow Wilson (b. 1936) and Arno Elan Penzias (b. 1933) of the Bell Telephone laboratory decided to use it for radio astronomy observations. The antenna was a 20-foot horn. Together with the latest receiving device, this radio telescope was at that time the most sensitive instrument in the world for measuring radio waves coming from space.

First of all, it was supposed to measure the radio emission of the interstellar medium of our Galaxy at a wavelength of 7.35 cm. Arno Pensias and Robert Wilson did not know about the theory of a hot Universe and were not going to look for relic radiation. To accurately measure the radio emission from the Galaxy, it was necessary to take into account all possible interference caused by radiation from the earth's atmosphere and the Earth's surface, as well as interference arising from the antenna, electrical circuits and receivers.

Preliminary tests of the receiving system showed slightly more noise than expected, but it seemed plausible that this was due to a slight excess of noise in the amplifying circuits. To overcome these problems, Penzias and Wilson used a device known as "cold loading": the signal coming from the antenna is compared to the signal from an artificial source cooled with liquid helium at about four degrees above absolute zero (4K). In both cases, the electrical noise in the amplifying circuits must be the same, and therefore the difference obtained by comparison gives the power of the signal coming from the antenna. This signal contains contributions only from the antenna arrangement, the earth's atmosphere, and the astronomical source of radio waves entering the antenna's field of view. Penzias and Wilson expected the antenna device to produce very little electrical noise. However, to test this assumption, they began their observations at relatively short wavelengths of 7.35 cm, at which the radio noise from the Galaxy should be negligible. Naturally, some radio noise was expected at this wavelength and from the earth's atmosphere, but this noise should have a characteristic dependence on direction: it should be proportional to the thickness of the atmosphere in the direction in which the antenna is looking: slightly less towards the zenith, slightly more towards horizon. It was expected that after subtracting the atmospheric directional term, there would be no significant signal from the antenna, and this would confirm that the electrical noise generated by the antenna device is negligible. After that, it will be possible to start studying the Galaxy itself at long wavelengths - about 21 cm, where the radiation Milky way has a very noticeable meaning.

Microwave noise

To their surprise, Penzias and Wilson discovered in the spring of 1964 that they received a fairly noticeable amount of direction-independent microwave noise at 7.35 cm. They found that this "static background" does not change with the time of day, and later found that it does not depend on the time of year. Therefore, this could not be the radiation of the Galaxy, because in this case its intensity would change depending on whether the antenna is looking along the plane of the Milky Way or across. In addition, if it were radiation from our Galaxy, then the large spiral galaxy M 31 in Andromeda, similar in many respects to ours, would also have to emit strongly at a wavelength of 7.35 cm, but this was not observed. The absence of any directional variation in observed microwave noise was a very strong indication that these radio waves, if they really existed, were not coming from the Milky Way, but from a much larger volume of the universe. It was clear to the researchers that it was necessary to check again if the antenna itself might be producing more electrical noise than expected. In particular, it was known that a pair of pigeons nestled in the horn of the antenna. They were caught, mailed to Bell's site in Whippany, released, rediscovered a few days later in their antenna location, recaptured, and finally pacified by more decisive means. However, during the lease, the pigeons covered the inside of the antenna with what Penzias called "white dielectric material," which could be a source of electrical noise at room temperature. In early 1965, the horn of the antenna was removed and all the dirt was cleaned out, but this, like all other tricks, produced very little reduction in the observed noise level.

When all sources of interference were carefully analyzed and taken into account, Penzias and Wilson were forced to conclude that radiation comes from space, and from all directions with the same intensity. It turned out that space radiates as if it were heated to a temperature of 3.5 kelvin (more precisely, the accuracy achieved made it possible to conclude that the "temperature of space" was from 2.5 to 4.5 kelvin). It should be noted that this is a very delicate experimental result: for example, if an ice cream briquette was placed in front of an antenna horn, then it would shine in the radio range, 22 million times brighter than the corresponding part of the sky. Pondering the unexpected result of their observations, Penzias and Wilson took their time to publish. But the events developed against their will. It so happened that Penzias called his friend Bernard Burke at the Massachusetts Institute of Technology for a completely different reason. Burke had recently heard from his colleague Ken Turner at the Carnegie Institution about a talk he had heard at Johns Hopkins University by Princeton theorist Phill Peebles, under the direction of Robert Dicke. In this talk, Peebles argued that there must be background radio noise left over from the early Universe and now has an equivalent temperature of about 10 K. Penzias called Dikka and the two research teams met. It became clear to Robert Dicke and his colleagues F. Peebles, P. Roll and D. Wilkinson that A. Penzias and R. Wilson had discovered the relic radiation of the hot Universe. The scientists decided to simultaneously publish two letters in the prestigious Astrophysical Journal. In the summer of 1965, both works were published: Penzias and Wilson on the discovery of relic radiation and Dicke and colleagues - with its explanation using the theory of a hot universe. Apparently not completely convinced of the cosmological interpretation of their discovery, Penzias and Wilson gave their note a modest title: Measurement of excess antenna temperature at a frequency of 4080 MHz. They simply announced that "measurements of the effective zenith noise temperature ... gave a value 3.5 K higher than expected" and avoided any mention of cosmology, except for the phrase that "a possible explanation for the observed excess noise temperature was given by Dicke, Peebles , Roll and Wilkinson in a companion letter in the same issue of the magazine.

In subsequent years, numerous measurements were carried out at various wavelengths from tens of centimeters to a fraction of a millimeter. Observations have shown that the spectrum of the relic radiation corresponds to the Planck formula, as it should be for radiation with a certain temperature. This temperature was confirmed to be approximately 3 K. A remarkable discovery was made proving that the universe was hot at the beginning of the expansion. Such is the intricate intertwining of events that culminated in the discovery of a hot universe by Penzias and Wilson in 1965. The establishment of the fact of superhigh temperature at the beginning of the expansion of the Universe was the starting point of the most important studies leading to the disclosure of the secrets of not only astrophysical, but also the secrets of the structure of matter. The most accurate measurements of the relic radiation were carried out from space: these are the Relikt experiment on the Soviet satellite Prognoz-9 (1983-1984) and the DMR (Differential Microwave Radiometer) experiment on the American satellite COBE (Cosmic Background Explorer, November 1989-1993) It was the latter that made it possible to determine the temperature of the relic radiation most accurately: 2.725 ± 0.002 K.

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Microwave background radiation (relic radiation)

- cosmic. radiation with a spectrum characteristic of at a temperature of approx. ZK; determines the intensity of the background radiation of the Universe in the short-wave radio range (at centimeter, millimeter and submillimeter waves). Characterized the highest degree isotropy (the intensity is practically the same in all directions). The discovery of M. f. and. (A. Penzias, R. Wilson, 1965, USA) confirmed the so-called. , gave the most important experimental evidence in favor of the concept of isotropy of the expansion of the Universe and its homogeneity on a large scale (see).

According to the hot Universe model, the matter of the expanding Universe in the past had a much higher density than it is now, and an extremely high temperature. When T \u003e 10 8 K primary, consisting of protons, helium ions and electrons, continuously emitting, scattering and absorbing photons, was in full with radiation. In the course of the subsequent expansion of the Universe, the temperature of plasma and radiation dropped. The interaction of particles with photons no longer had time to noticeably influence the radiation spectrum during the characteristic expansion time (the universe in terms of bremsstrahlung by this time had become much less than unity). However, even in the complete absence of interaction of radiation with matter during the expansion of the Universe, the blackbody spectrum of radiation remains blackbody, only the radiation temperature decreases. While the temperature exceeded 4000 K, the primary matter was completely ionized, the range of photons from one scattering event to another was much less. At 4000 K, protons and electrons occurred, the plasma turned into a mixture of neutral hydrogen and helium atoms, the Universe became completely transparent to radiation. In the course of its further expansion, the radiation temperature continued to fall, but the blackbody character of the radiation was preserved as a relic, as a "memory" of the early period of the world's evolution. This radiation was first detected at 7.35 cm, and then at other waves (from 0.6 mm to 50 cm).

Temp-ra M. f. and. with an accuracy of 10% turned out to be 2.7 K. Cf. the energy of the photons of this radiation is extremely small - 3000 times less than the energy of the photons of visible light, but the number of photons of the M. f. and. very large. For each atom in the Universe there are ~ 10 9 photons of the M. f. and. (on average 400-500 photons per 1 cm 3).

Along with the direct method for determining the temperature of M. f. and. - according to the energy distribution curve in the radiation spectrum (see), there is also an indirect method - according to the population of the lower energy levels of molecules in the interstellar medium. When a photon is absorbed, M. f. and. the molecule passes from the main. states to excited. The higher the radiation temperature, the higher the density of photons with an energy sufficient to excite molecules, and the greater their fraction is at the excited level. By the number of excited molecules (population of levels), one can judge the temperature of the exciting radiation. So, observations of optical. the absorption lines of interstellar cyanogen (CN) show that its lower energy levels are populated as if the CN molecules were in the field of three-degree blackbody radiation. This fact was established (but not fully understood) back in 1941, long before the discovery of M. f. and. direct observations.

No stars and radio galaxies, no hot intergalactic. gas, nor the re-emission of visible light by interstellar dust can not give radiation, approaching the St. i .: the total energy of this radiation is too high, and its spectrum does not resemble either the spectrum of stars or the spectrum of radio sources (Fig. 1). This, as well as the almost complete absence of intensity fluctuations over the celestial sphere (small-scale angular fluctuations) proves the cosmological, relict origin of the M. f. and.

Fluctuations of M. f. and.
Detection of small differences in the intensity of M. t. and., received from different parts of the celestial sphere, would make it possible to draw a number of conclusions about the nature of the primary perturbations in matter, which subsequently led to the formation of galaxies and clusters of galaxies. Modern galaxies and their clusters were formed as a result of the growth of insignificant amplitude inhomogeneities in the density of matter that existed before the recombination of hydrogen in the Universe. For any cosmologist. model, you can find the law of growth of the amplitude of inhomogeneities during the expansion of the Universe. If one knows what the amplitudes of the inhomogeneity of the substance were at the moment of recombination, one can establish how long it took them to grow and become of the order of unity. After that, regions with a density significantly higher than the average should have stood out from the general expanding background and gave rise to galaxies and their clusters. Only relic radiation can "tell" about the amplitude of the initial density inhomogeneities at the moment of recombination. Since, before recombination, radiation was rigidly bound to matter (electrons scattered photons), inhomogeneities in the spatial distribution of matter led to inhomogeneities in the radiation energy density, i.e., to a difference in the radiation temperature in regions of the Universe with different density. When, after recombination, the substance stopped interacting with radiation and became transparent to it, M. f. and. should have retained all the information about density inhomogeneities in the Universe during the recombination period. If inhomogeneities existed, then the temperature of the M. f. and. should fluctuate, depend on the direction of observation. However, experiments to detect the expected fluctuations are not yet sufficiently accurate. They give only the upper limits of the fluctuation values. On small angular scales (from one angular minute to six degrees of arc) fluctuations do not exceed 10 -4 K. Search for fluctuations of the M. f. and. are also complicated by the fact that discrete cosmic rays contribute to background fluctuations. radio sources, the radiation of the Earth's atmosphere fluctuates, etc. Experiments on large angular scales have also shown that the temperature of the M. f. and. practically does not depend on the direction of observation: the deviations do not exceed K. The data obtained made it possible to reduce the estimate of the degree of anisotropy of the expansion of the Universe by a factor of 100 in comparison with the estimate based on the data of direct observations of "scattering" galaxies.

M. f. and. as a "new ether".
M. f. and. isotropic only in the coordinate system associated with "scattering" galaxies, in the so-called. accompanying frame of reference (this frame expands with the Universe). In any other coordinate system, the radiation intensity depends on the direction. This fact opens up the possibility of measuring the speed of the Sun's motion relative to the coordinate system associated with the M. f. and. Indeed, due to the Doppler effect, the photons propagating towards the moving observer have a higher energy than those that catch up with him, despite the fact that in the system associated with the M. f. and., their energies are equal. Therefore, the radiation temperature for such an observer turns out to depend on the direction:, where T 0 - cf. the radiation temperature across the sky, v is the observer's speed, is the angle between the velocity vector and the direction of observation.

The dipole anisotropy of the relict radiation, associated with the motion of the solar system relative to the field of this radiation, has been firmly established by now (Fig. 2): in the direction of the constellation Leo, the temperature of M. f. and. is 3.5 mK higher than the average, and in the opposite direction (the constellation of Aquarius) by the same amount below the average. Consequently, the Sun (together with the Earth) moves relative to the M. f. and. at a speed of approx. 400 km / s towards the constellation Leo. The accuracy of the observations is so high that the experimenters record the speed of the Earth's motion around the Sun at 30 km / s. Taking into account the speed of motion of the Sun around the center of the Galaxy makes it possible to determine the speed of motion of the Galaxy relative to the Mf. and. It is 600 km / s. In principle, there is a method that allows you to determine the speed of rich clusters of galaxies relative to the relict radiation (see).

Spectrum M. f. and.
In fig. 1 shows the existing experimental data on M. f. and. and the Planck curve of energy distribution in the spectrum of equilibrium radiation of an absolutely black body having a temperature of 2.7 K. The positions of the experimental points are in good agreement with the theoretical. crooked. This is strong support for the hot universe model.

Note that in the range of centimeter and decimeter waves, measurements of the temperature of M. f. and. possible from the surface of the Earth using radio telescopes. In the millimeter and especially in the submillimeter ranges, atmospheric radiation interferes with the observations of the magnetic field. and., therefore, the measurements are carried out with broadband set at balloons (balloons) and rockets. Valuable data on the spectrum of M. f. and. in the millimeter range are obtained from observations of absorption lines of molecules of the interstellar medium in the spectra of hot stars. It turned out that DOS. contribution to the energy density of the M. f. and. gives radiation from 6 to 0.6 mm, the temperature of which is close to 3 K. In this wavelength range, the energy density of the M. f. and. \u003d 0.25 eV / cm 3.

Many of the cosmologists. theories and theories of the formation of galaxies, which consider the processes of matter and antimatter, the dissipation of developed, large-scale potential motions, the evaporation of primary small masses, the decay of unstable ones, predict. energy release in the early stages of the expansion of the Universe. At the same time, any release of energy align \u003d "absmiddle" width \u003d "127" height \u003d "18"\u003e at the stage when the temperature of M. f. and. varied from up to 3 K, should have noticeably distorted its blackbody spectrum. Thus, the spectrum of M. f. and. carries information about the thermal history of the Universe. Moreover, this information turns out to be differentiated: the release of energy at each of the three stages of expansion (K; 3T 4000 K). There are very few such energetic photons (~ 10 -9 of their total number). Therefore, the recombination radiation that arises during the formation of neutral atoms should have strongly distorted the spectrum of the magnetic field. and. at 250 microns.

The substance could experience another heating during the formation of galaxies. Spectrum M. f. and. in this case, it could also change, since the scattering of relict photons by hot electrons increases the energy of the photons (see). Especially strong changes occur in this case in the short-wavelength region of the spectrum. One of the curves showing the possible distortion of the spectrum of the M. f. and., is shown in Fig. 1 (dashed line). Available changes in the spectrum of M. f. and. showed that the secondary heating of matter in the Universe occurred much later than recombination.

M. f. and. and cosmic rays.

Cosmich. rays (protons and high-energy nuclei; ultra-relativistic electrons, which determine the radio emission of our and other galaxies in the meter range) carry information about giant explosive processes in stars and galactic nuclei, at which they are born. As it turned out, the lifetime of high-energy particles in the Universe largely depends on the photons of the M. f. and., possessing low energy, but extremely numerous - there are a billion times more of them than atoms in the Universe (this ratio remains in the process of expansion of the Universe). In the collision of ultrarelativistic electrons, cosmic. rays with photons M. f. and. there is a redistribution of energy and momentum. The photon energy increases many times, and the radio photon turns into an X-ray photon. radiation, the energy of the electron changes slightly. Since this process is repeated many times, the electron gradually loses all energy. Observed from satellites and rockets x-rays. background radiation appears to be partly due to this process.

Ultrahigh-energy protons and nuclei are also subject to the action of photons from the M. f. i .: in collisions with them, nuclei split, and collisions with protons lead to the creation of new particles (electron-positron pairs, -mesons, etc.). As a result, the energy of protons quickly decreases to the threshold, below which the creation of particles becomes impossible according to the laws of conservation of energy and momentum. It is with these processes that practical. absence in space. rays of particles with an energy of 10 20 eV, as well as a small number of heavy nuclei.

Lit .:
Zeldovich Ya.B., "Hot" model of the Universe, UFN, 1966, v. 89, v. 4, p. 647; Weinberg S., The first three minutes, trans. from English, M., 1981.

Despite the use of modern devices and the latest techniques study of the Universe, the question of its appearance is still open. This is not surprising when you consider its age: according to the latest data, it ranges from 14 to 15 billion years. It is obvious that since then there has been very little evidence of the once grandiose processes of the Universal scale. Therefore, no one dares to assert anything, limiting themselves to hypotheses. However, one of them has recently received a very significant argument - relic radiation.

In 1964, two employees of a well-known laboratory, performing radio observation of the Echo satellite, having access to the appropriate supersensitive equipment, decided to test some of their theories regarding the intrinsic radio emission of certain space objects.

In order to filter out possible interference from terrestrial sources, it was decided to use 7.35 cm. However, after turning on and tuning the antenna, a strange phenomenon was registered: a certain noise, a constant background component, was recorded throughout the Universe. It did not depend on the position of the Earth relative to other planets, which immediately sifted out the assumption of these radio interference either from the time of day. Neither R. Wilson nor A. Penzias even suspected that they had discovered the relict radiation of the universe.

Since none of them assumed this, writing off the "background" on the features of the equipment (suffice it to recall that the microwave antenna used was the most sensitive at that time), almost a year passed until it became obvious that the recorded noise is part of the Universe itself. The intensity of the captured radio signal turned out to be practically identical to the intensity of radiation with a temperature of 3 Kelvin (1 Kelvin is equal to -273 degrees Celsius). For comparison: zero Kelvin corresponds to the temperature of an object of stationary atoms. ranges from 500 MHz to 500 GHz.

At this time, two theorists from Princeton University - R. Dicke and D. Peibbles, based on new models of the development of the Universe, mathematically calculated that such radiation should exist and permeate all space. Needless to say, Penzias, who accidentally found out about lectures on this topic, contacted the university and reported that the relic radiation was recorded.

Based on the Big Bang theory, all matter was created as a result of a colossal explosion. For the first 300 thousand years after that, space was a combination elementary particles and radiation. Subsequently, due to the expansion, temperatures began to fall, which made it possible for atoms to appear. The recorded relic radiation is an echo of those distant times. While the universe had boundaries, the density of particles was so high that the radiation was "bound", since the mass of particles reflected any kind of waves, not allowing them to propagate. And only after the beginning of the formation of atoms, space became "transparent" for waves. It is believed that the relic radiation appeared in this way. At the moment in everyone cubic centimeter space contains about 500 initial quanta, however, their energy has decreased by almost 100 times.

The relic radiation in different parts of the Universe has different temperatures. This is due to the location of the primary matter in the expanding Universe. Where the density of atoms of future matter was higher, the fraction of radiation, and hence its temperature, was reduced. It was in these directions that large objects (galaxies and their clusters).

The study of the relic radiation lifts the veil of uncertainty over many processes taking place at the beginning of time.

The CMB is the background microwave radiation, which is the same in all directions and has a spectrum characteristic of a black body at a temperature of ~ 2.7 K.

It is believed that by this radiation one can find out the answer to the question: where did it come from? In fact, the relic radiation is what was left of the "construction of the Universe" when it only began to emerge after the expansion of a dense hot plasma. In order to make it easier to understand what relict radiation is, let's compare it with the remnants of human activity. For example, a person invents something, others buy it, use it and throw it away. So garbage (the very result of human life) is the analogue of the relic radiation. By the garbage you can find out everything - where a person was at a certain period of time, what he ate, what he was wearing, and even what he was talking about. Also the relic radiation. According to its properties, scientists are trying to build a picture of the moment of the big bang, which may give an answer to the question: how did the universe appear? But still, the laws of conservation of energy create certain disagreements about the origin of the universe, because nothing comes from nowhere and does not disappear anywhere. The dynamics of our universe are transitions, changes in properties and states. This can be observed even on our planet. For example, ball lightning appears in a cloud of water particles ?! How? How can this be? Nobody can explain the origin of these or those laws. There are only moments of discovery of these laws, as well as the history of the discovery of relic radiation.

Historical facts of the study of relic radiation

For the first time, Georgy Antonovich Gamow (George Gamow) mentioned the relic radiation when he tried to explain the big bang theory. He assumed that some kind of residual radiation fills the space of an ever-expanding universe. In 1941, while studying the absorption of one of the stars of the Ophiuchus cluster, Andrew McKellar noticed spectral absorption lines of light, which corresponded to a temperature of 2.7 K. In 1948, Georgy Gamov, Ralph Alfert and Robert Herman set the temperature of the relic radiation at 5 K. Later Georgy Gamov assumed the temperature was less than the known one in 3 K. But this was only a superficial study of this fact, at that time unknown to anyone. In the early 1960s, Robert Dicke and Yakov Zeldovich obtained the same results as Gamow, recording waves whose radiation intensity did not depend on time. The inquisitive mind of scientists had to create a special radio telescope for more accurate registration of the relic radiation. In the early 1980s, with the development of the space industry, the relic radiation began to be studied more thoroughly from the spacecraft. It was possible to establish the property of the isotropy of the relic radiation (the same properties in all directions, for example, 5 steps to the north in 10 seconds and 5 steps to the south will also take 10 seconds). Today, studies of the properties of the relict study and the history of its origin are continuing.

What properties does the relic radiation have?

CMB spectrum from data obtained with the FIRAS instrument aboard the COBE satellite

The CMB spectrum is 2.75 Kelvin, which is similar to soot cooled to this temperature. Such a substance always absorbs the radiation (light) incident on it, no matter how you influence it. Put it into the magnetic coil, though nuclear bomb throw it, even shine a spotlight. Such a body also emits small radiation. But this only proves the fact that nothing is absolute. It is always possible to derive an ideal law for an infinitely long time, to achieve the maximum of a certain property of something, but there will always be a small fraction of inertia.

Interesting facts related to the study of the CMB

The maximum CMB frequency was recorded at 160.4 GHz, which is equal to 1.9 mm wavelength. And the density of such radiation is 400-500 photons per cm 3. The relic radiation is the oldest, most ancient radiation that can be observed in general in the universe. Each particle has traveled 400,000 years to reach Earth. Not kilometers, but years! According to satellite observations and mathematical calculations, the relic radiation seems to stand still, and all galaxies and constellations move relative to it at a tremendous speed, on the order of hundreds of kilometers per second. It's like looking out the window of a moving train. The CMB temperature in the direction of the constellation is 0.1% higher, and in the opposite direction, 0.1% lower. This explains the movement of the Sun towards this constellation relative to the relict background.

What does the study of relic radiation give us?

The early universe was cold, very cold. Why was the universe so cold and what happened when the universe began to expand? It can be assumed that due to the big bang, a huge amount of energy clots were released outside the universe, then the universe cooled down, almost froze, but over time, the energy began to gather into clots again, and a certain reaction arose that triggered the expansion of the universe. Then where did dark matter come from and does it interact with the relic radiation? Perhaps the relic radiation is the result of the decomposition of dark matter, which is more logical than the residual radiation of the big bang. Since dark energy can be antimatter and particles of dark matter, colliding with particles of matter, form radiation in the material and antimaterial world like a relict one. Today it is the freshest, unexplored area of \u200b\u200bscience in which one can achieve success and be imprinted in the history of science and society.