CMB radiation
Extragalactic microwave background radiation occurs in the frequency range from 500 MHz to 500 GHz, which corresponds to wavelengths from 60 cm to 0.6 mm. This background radiation carries information about the processes that took place in the Universe before the formation of galaxies, quasars, and other objects. This radiation, called relic, was discovered in 1965, although it was predicted back in the 40s by Georgy Gamow and studied by astronomers for decades.
In the expanding Universe, the average density of matter depends on time - in the past it was greater. However, during expansion, not only the density changes, but also the thermal energy of matter, which means that at the early stage of expansion the Universe was not only dense, but also hot. As a consequence, in our time there should be a residual radiation whose spectrum is the same as the spectrum of an absolutely solid body, and this radiation should be highly isotropic. In 1964, A.A. Penzias and R. Wilson, testing a sensitive radio antenna, discovered a very weak background microwave radiation, which they could not get rid of in any way. Its temperature turned out to be 2.73 K, which is close to the predicted value. From experiments on the study of isotropy, it was shown that the source of microwave background radiation cannot be located inside the Galaxy, since then a concentration of radiation towards the center of the Galaxy would have to be observed. The source of radiation could not be located inside the solar system, as well. a diurnal variation in the radiation intensity would be observed. Because of this, a conclusion was drawn about the extragalactic nature of this background radiation. Thus, the hypothesis of a hot Universe received an observational basis.
To understand the nature of the CMB, it is necessary to turn to the processes that took place in the early stages of the expansion of the Universe. Let us consider how the physical conditions in the Universe changed during the expansion process.
Now each cubic centimeter of space contains about 500 cosmic microwave background photons, and there is much less substance in this volume. Since the ratio of the number of photons to the number of baryons in the process of expansion is preserved, but the energy of photons in the course of the expansion of the Universe decreases with time due to redshift, we can conclude that at some time in the past the energy density of radiation was greater than the energy density of matter particles. This time is called the radiation stage in the evolution of the Universe. The radiation stage was characterized by the equality of the temperature of matter and radiation. In those days, radiation completely determined the nature of the expansion of the Universe. Approximately one million years after the start of the expansion of the Universe, the temperature dropped to several thousand degrees and the recombination of electrons, which were previously free particles, took place with protons and helium nuclei, i.e. the formation of atoms. The Universe has become transparent to radiation, and it is this radiation that we now capture and call relict. True, since that time, due to the expansion of the Universe, photons have reduced their energy by about 100 times. Figuratively speaking, relic radiation quanta "imprinted" the era of recombination and carry direct information about the distant past.
After recombination, the matter for the first time began to evolve independently, regardless of radiation, and densifications began to appear in it - the embryos of future galaxies and their clusters. That is why experiments on studying the properties of relic radiation - its spectrum and spatial fluctuations - are so important for scientists. Their efforts were not in vain: in the early 90s. The Russian space experiment "Relikt-2" and the American "Kobe" discovered differences in the temperature of the relict radiation of neighboring sections of the sky, and the deviation from the average temperature is only about a thousandth of a percent. These temperature variations carry information about the deviation of the matter density from the average value during the recombination epoch. After recombination, the matter in the Universe was distributed almost evenly, and where the density was at least slightly above average, the attraction was stronger. It was density variations that subsequently led to the formation of large-scale structures observed in the Universe, clusters of galaxies and individual galaxies. According to modern concepts, the first galaxies should have formed in an epoch that corresponds to redshifts from 4 to 8.
Is there any chance to look even further into the era preceding recombination? Until the moment of recombination, it was the pressure of electromagnetic radiation that mainly created the gravitational field, which slowed down the expansion of the Universe. At this stage, the temperature varied in inverse proportion to the square root of the time elapsed since the start of expansion. Let us consider successively different stages of the expansion of the early Universe.
At a temperature of approximately 1013 Kelvin, pairs of various particles and antiparticles were born and annihilated in the Universe: protons, neutrons, mesons, electrons, neutrinos, etc. When the temperature dropped to 5 * 1012 K, almost all protons and neutrons annihilated, turning into radiation quanta; only those for which there were “not enough” antiparticles remained. It is from these "excess" protons and neutrons that the substance of the modern observable Universe mainly consists.
At Т= 2*1010 K all-penetrating neutrinos ceased to interact with the matter – from that moment the “relic background of neutrinos” should have remained, which may be detected in the course of future neutrino experiments.
Everything that has just been said took place at superhigh temperatures in the first second after the beginning of the expansion of the Universe. A few seconds after the moment of the “birth” of the Universe, the era of primary nucleosynthesis began, when the nuclei of deuterium, helium, lithium and beryllium were formed. It lasted approximately three minutes, and its main result was the formation of helium nuclei (25% of the mass of the entire matter of the Universe). The remaining elements, heavier than helium, made up a negligible part of the substance - about 0.01%.
After the epoch of nucleosynthesis and before the epoch of recombination (about 106 years), there was a calm expansion and cooling of the Universe, and then - hundreds of millions of years after the beginning - the first galaxies and stars appeared.
In recent decades, the development of cosmology and elementary particle physics has made it possible to theoretically consider the very initial, “superdense” period of the expansion of the Universe. It turns out that at the very beginning of the expansion, when the temperature was incredibly high (more than 1028 K), the Universe could be in a special state in which it expanded with acceleration, and the energy per unit volume remained constant. This stage of expansion was called inflationary. Such a state of matter is possible under one condition - negative pressure. The stage of ultrafast inflationary expansion covered a tiny period of time: it ended by the time of about 10–36 s. It is believed that the real “birth” of elementary particles of matter in the form in which we know them now occurred just after the end of the inflationary stage and was caused by the collapse of the hypothetical field. After that, the expansion of the universe continued by inertia.
The hypothesis of an inflationary Universe answers a number of important questions in cosmology, which until recently were considered inexplicable paradoxes, in particular, the question of the cause of the expansion of the Universe. If in its history the Universe really went through an era when there was a large negative pressure, then gravity would inevitably have to cause not attraction, but mutual repulsion of material particles. And that means that the Universe began to expand rapidly, explosively. Of course, the model of the inflationary Universe is only a hypothesis: even an indirect verification of its positions requires such instruments, which are simply not yet created at present. However, the idea of accelerated expansion of the Universe at the earliest stage of its evolution has firmly entered modern cosmology.
Speaking of the early Universe, we are suddenly transferred from the largest cosmic scales to the region of the microworld, which is described by the laws of quantum mechanics. The physics of elementary particles and superhigh energies is closely intertwined in cosmology with the physics of giant astronomical systems. The biggest and the smallest merge here with each other. This is the amazing beauty of our world, full of unexpected interconnections and deep unity.
The manifestations of life on Earth are extremely diverse. Life on Earth is represented by nuclear and pre-nuclear, unicellular and multicellular beings; multicellular, in turn, are represented by fungi, plants and animals. Any of these kingdoms unites various types, classes, orders, families, genera, species, populations and individuals.
In all the seemingly endless variety of living things, several different levels of organization of living things can be distinguished: molecular, cellular, tissue, organ, ontogenetic, population, species, biogeocenotic, biospheric. The listed levels are highlighted for ease of study. If we try to identify the main levels, which reflect not so much the levels of study as the levels of organization of life on Earth, then the main criteria for such a selection should be recognized as the presence of specific elementary, discrete structures and elementary phenomena. With this approach, it turns out to be necessary and sufficient to single out the molecular-genetic, ontogenetic, population-species and biogeocenotic levels (N.V. Timofeev-Resovsky and others).
Molecular genetic level. In the study of this level, apparently, the greatest clarity has been achieved in the definition of the basic concepts, as well as in the identification of elementary structures and phenomena. The development of the chromosomal theory of heredity, the analysis of the mutation process, and the study of the structure of chromosomes, phages, and viruses revealed the main features of the organization of elementary genetic structures and the phenomena associated with them. It is known that the main structures at this level (codes of hereditary information transmitted from generation to generation) are DNA, differentiated in length into code elements - triplets of nitrogenous bases that form genes.
Genes at this level of life organization represent elementary units. The main elementary phenomena associated with genes can be considered their local structural changes (mutations) and the transfer of information stored in them to intracellular control systems.
Covariant reduplication occurs according to the matrix principle by breaking the hydrogen bonds of the DNA double helix with the participation of the DNA polymerase enzyme. Then each of the strands builds a corresponding thread for itself, after which the new strands are complementaryly connected to each other. The pyrimidine and purine bases of the complementary strands are hydrogen-bonded to each other by DNA polymerase. This process is very fast. Thus, the self-assembly of Escherichia coli DNA, which consists of approximately 40 thousand base pairs, requires only 100 s. Genetic information is transferred from the nucleus by mRNA molecules to the cytoplasm to the ribosomes and is involved in protein synthesis there. A protein containing thousands of amino acids is synthesized in a living cell in 5–6 minutes, while in bacteria it is faster.
The main control systems, both in convariant reduplication and in intracellular information transfer, use the "matrix principle", i.e. are matrices, next to which the corresponding specific macromolecules are built. At present, the code embedded in the structure of nucleic acids, which serves as a matrix in the synthesis of specific protein structures in cells, is being successfully deciphered. Reduplication based on matrix copying retains not only the genetic norm, but also deviations from it, i.e. mutations (the basis of the evolutionary process). Sufficiently accurate knowledge of the molecular-genetic level is a necessary prerequisite for a clear understanding of life phenomena occurring at all other levels of life organization.
One of the components of the general background cosm. email magn. radiation. R. i. uniformly distributed over the celestial sphere and corresponds in intensity to the thermal radiation of an absolutely black body at a temperature of approx. 3 K, discovered Amer. scientists A. Penzias and ... Physical Encyclopedia
RELICT radiation, filling the Universe with cosmic radiation, the spectrum of which is close to the spectrum of an absolutely black body with a temperature of about 3 K. It is observed at waves from several mm to tens of cm, almost isotropically. Origin... ... Modern Encyclopedia
Background cosmic radiation, the spectrum of which is close to the spectrum of a completely black body with a temperature of approx. 3 K. It is observed at waves from several mm to tens of cm, almost isotropically. The origin of relic radiation is associated with the evolution of ... Big Encyclopedic Dictionary
background radiation- Background cosmic radio emission, which was formed in the early stages of the development of the Universe. [GOST 25645.103 84] Subjects conditions physical space. space EN relic radiation … Technical Translator's Handbook
Background cosmic radiation, the spectrum of which is close to the spectrum of a black body with a temperature of about 3°K. It is observed at wavelengths from a few millimeters to tens of centimeters, almost isotropically. The origin of the relic radiation ... ... encyclopedic Dictionary
Electromagnetic radiation that fills the observable part of the Universe (See Universe). R. i. existed already in the early stages of the expansion of the Universe and played an important role in its evolution; is a unique source of information about her past... Great Soviet Encyclopedia
CMB radiation- (from lat. relicium remnant) cosmic electromagnetic radiation associated with the evolution of the Universe, which began its development after the "big bang"; background cosmic radiation, the spectrum of which is close to the spectrum of a completely black body with ... ... Beginnings of modern natural science
Background space radiation, the spectrum of which is close to the spectrum of an absolutely black body with a temperature of approx. 3 K. Observed on waves from several. mm to tens of cm, almost isotropically. R.'s origin and. associated with the evolution of the universe, to paradise in the past ... ... Natural science. encyclopedic Dictionary
Thermal background cosmic radiation, the spectrum of which is close to the spectrum of an absolutely black body with a temperature of 2.7 K. The origin of R. i. associated with the evolution of the Universe, which in the distant past had a high temperature and radiation density ... ... Astronomical dictionary
Cosmology Age of the Universe Big Bang Cosmic distance Relic radiation Cosmological equation of state Dark energy Hidden mass Friedmann Universe Cosmological principle Cosmological models Formation ... Wikipedia
Books
- A set of tables. Evolution of the Universe (12 tables), . Educational album of 12 sheets. Article - 5-8676-012. astronomical structures. Hubble law. Friedman model. Periods of evolution of the Universe. early universe. primary nucleosynthesis. Relic…
- Cosmology, Steven Weinberg. A monumental monograph by Nobel laureate Steven Weinberg summarizes the results of the progress made over the past two decades in modern cosmology. She is unique in…
Microwave background radiation (CMB)
- cosmic radiation having a spectrum characteristic of at a temperature of approx. ZK; determines the intensity of the background radiation of the Universe in the shortwave radio range (on centimeter, millimeter and submillimeter waves). It is characterized by the highest degree of isotropy (the intensity is almost the same in all directions). Opening of M. f. and. (A. Penzias, R. Wilson, 1965, USA) confirmed the so-called. , gave the most important experimental evidence in favor of the ideas about the isotropy of the expansion of the Universe and its homogeneity on large scales (see ).According to the model of the hot Universe, the substance of the expanding Universe had in the past a much higher density than now, and an extremely high temperature. At T> 10 8 K primary, consisting of protons, helium ions and electrons, continuously emitting, scattering and absorbing photons, was in full radiation. During the subsequent expansion of the Universe, the temperature of plasma and radiation fell. The interaction of particles with photons no longer had time to noticeably affect the radiation spectrum during the characteristic time of expansion (by this time the Universe had become much less than unity in terms of bremsstrahlung). However, even in the absence of interaction between radiation and matter during the expansion of the Universe, the black-body radiation spectrum remains black-body, only the radiation temperature decreases. While the temperature exceeded 4000 K, the primary substance 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 temperature of the radiation continued to fall, but the black-body nature of the radiation was preserved as a relic, as a "memory" of the early period of the evolution of the world. This radiation was discovered first at a wavelength of 7.35 cm, and then at other wavelengths (from 0.6 mm to 50 cm).
Temp-ra M. f. and. with an accuracy of 10% turned out to be equal to 2.7 K. Cf. the energy of photons of this radiation is extremely small - 3000 times less than the energy of photons of visible light, but the number of photons of M. f. and. very large. For each atom in the Universe, there are ~ 10 9 photons of M. f. and. (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. At absorption of a photon M. f. and. the molecule moves from the main state to excited. The higher the radiation temperature, the higher the density of photons with energy sufficient to excite molecules, and the greater their proportion is at the excited level. By the number of excited molecules (level population) one can judge the temperature of the exciting radiation. Thus, the observations of optical The absorption lines of interstellar cyanogen (CN) show that its lower energy levels are populated as if the CN molecules are in a three-degree black-body radiation field. This fact was established (but not fully understood) as early as 1941, long before the discovery of M. f. and. direct observations.Neither stars and radio galaxies, nor hot intergalaxies. gas, nor the re-emission of visible light by interstellar dust, can produce radiation approaching St. and .: 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 M. f. and.
Fluctuations of M. f. and.
Detection of small distinctions in intensity M. f. and., received from different parts of the celestial sphere, would allow us 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 in amplitude inhomogeneities in the density of matter that existed before the recombination of hydrogen in the Universe. For any cosmological model, one can find the law of growth of the amplitude of inhomogeneities in the course of the expansion of the Universe. If you know what were the amplitudes of the inhomogeneity of the substance at the time of recombination, you can determine how long they could grow and become about unity. After that, regions with a density much higher than the average should have stood out from the general expanding background and given 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 the 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 ceased to interact with radiation and became transparent to it, M. f. and. was supposed to preserve all the information about density inhomogeneities in the Universe during the recombination period. If inhomogeneities existed, then the temperature of M. f. and. should fluctuate depending on the direction of observation. However, experiments to detect the expected fluctuations do not yet have sufficiently high accuracy. They give only upper limits on fluctuation values. On small angular scales (from one minute of arc to six degrees of arc), fluctuations do not exceed 10 -4 K. Searches for fluctuations of M. f. and. are also complicated by the fact that the contribution to the background fluctuations is given by discrete cosmic. radio sources, the radiation of the Earth's atmosphere fluctuates, etc. Experiments on large angular scales also showed that the temperature of the M. f. and. practically does not depend on the direction of observation: the deviations do not exceed K. The obtained data made it possible to reduce the estimate of the degree of anisotropy of the expansion of the Universe by a factor of 100 compared to the estimate from the data of direct observations of "receding" galaxies.
M. f. and. as "new air".
M. f. and. isotropic only in the coordinate system associated with "receding" galaxies, in the so-called. comoving frame of reference (this frame is expanding along 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 relative to the coordinate system associated with the M. f. and. Indeed, due to the Doppler effect, photons propagating towards a moving observer have a higher energy than those catching up with him, despite the fact that in the system associated with M. f. i.e., their energies are equal. Therefore, the radiation temperature for such an observer turns out to depend on the direction: , where T 0 - cf. across the sky radiation temperature, v- the speed of the observer, - the angle between the velocity vector and the direction of observation.
The dipole anisotropy of the relic radiation, associated with the motion of the solar system relative to the field of this radiation, has now been firmly established (Fig. 2): in the direction of the constellation Leo, the temperature of M. f. and. 3.5 mK above 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 observations is so high that experimenters fix the speed of the Earth around the Sun, which is 30 km/s. Accounting for the velocity of the Sun around the center of the Galaxy makes it possible to determine the velocity of the Galaxy relative to the magnetic field. and. It is 600 km/s. In principle, there is a method that makes it possible to determine the velocities of rich clusters of galaxies relative to the background radiation (see ).
Spectrum M. f. and.
On fig. 1 shows the existing experimental data on M. f. and. and the Planck energy distribution curve in the equilibrium radiation spectrum 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 a strong confirmation of 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 Earth's surface using radio telescopes. In the millimeter and especially in the submillimeter ranges, the radiation of the atmosphere interferes with the observations of M. f. and., therefore, measurements are carried out by broadband, installed on balloons (cylinders) and rockets. Valuable data on the spectrum of M. t. and. in the millimeter range were obtained from observations of the absorption lines of the molecules of the interstellar medium in the spectra of hot stars. It turned out that the main contribution to the energy density of 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 cosmological 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 means. energy release in the early stages of the expansion of the universe. At the same time, any release of energy align="absmiddle" width="127" height="18"> at the stage when the temperature of the M. f. and. changed from up to 3 K, it 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: energy release at each of the three expansion stages (K; 3T 4000 K). There are very few such energetic photons (~10 -9 of their total number). Therefore, the recombination radiation arising from the formation of neutral atoms must have strongly distorted the spectrum of the magnetic field. and. at waves of 250 μm.The substance could experience another heating during the formation of galaxies. Spectrum M. f. and. could also change in this case, since the scattering of relic photons by hot electrons increases the photon energy (see ). Especially strong changes occur in this case in the short-wavelength region of the spectrum. One of the curves demonstrating the possible distortion of the spectrum of M. f. i., shown in Fig. 1 (dashed curve). Available changes in the spectrum of M. t. and. showed that the secondary heating of matter in the Universe occurred much later than recombination.
M. f. and. and cosmic rays.
Space beams (high-energy protons and nuclei; ultrarelativnst electrons that 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 is preserved in the process of expansion of the Universe). In the collision of ultrarelativistic electrons cosmic. rays with photons M. f. and. energy and momentum are redistributed. The energy of the photon increases many times over, and the radio photon turns into an x-ray photon. radiation, while the energy of the electron changes insignificantly. Since this process is repeated many times, the electron gradually loses all the energy. Observed from satellites and rockets roentgen. the background radiation appears to be partly due to this process.
Protons and superhigh-energy nuclei are also subject to the action of photons of M. f. and .: in collisions with them, the nuclei split, and collisions with protons lead to the birth of new particles (electron-positron pairs, -mesons, etc.). As a result, the energy of protons rapidly 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 the practice is associated. absence in space beams of particles with an energy of 10 20 eV, as well as a small number of heavy nuclei.
Lit.:
Zel'dovich Ya.B., "Hot" model of the Universe, UFN, 1966, v. 89, c. 4, p. 647; Weinberg S., The first three minutes, trans. from English, M., 1981.
As the reader has probably already noticed, the history of radio astronomy has developed in such a way that the most important discoveries in this field of science were made by accident. The very beginning of radio astronomy was laid by the accidental discovery by Jansky of discrete sources of radiation coming to Earth from space. When researching
phenomena of flickering of radio waves as an accidental, secondary, but much more important result, pulsars were discovered.
Another major discovery of our day was made quite unexpectedly for those who discovered a new phenomenon. In 1965, Penzias and Wilson, two radio specialists, on behalf of Bell, investigated one of the most sensitive devices for receiving radio waves and made improvements to it to eliminate the effects of all possible interference. When, after a long work, they came to the conclusion that they had done everything in this direction and the influence of terrestrial sources of radio emission should be completely destroyed, it turned out that the receiving device directed to the sky continues to receive, although very weak, but surely registered radio emission. Its peculiarity was that the radiation intensity showed almost strict constancy for all directions, with the exception, of course, of those in which discrete cosmic radio emission saddlers are located.
The significance of the discovery made became clear when further studies showed that the distribution of incoming radiation over wavelengths corresponds to the radiation of a "black body". It is such as would be caused by a body having an extremely low temperature: 3 kelvin (Kelvin). In accordance with Wien's law (λ m · T = 0.2897) the maximum radiation energy at this temperature falls on a wavelength of about 1 mm.
From the almost complete independence of the intensity of the detected radio emission from the direction (its isotropy), it follows that the Universe is permeated by this radiation, it fills all the space between stars and galaxies. The distribution of energy in the spectrum according to the law for an absolutely black body with a temperature of 3 K shows that this radiation is not a transformed radiation of stars, nebulae and galaxies, but is an independent substance that fills the space of the Universe. Therefore, it is called background radiation.
