What happened as a result of the big bang. Big Bang. Inflation: Explaining the Big Bang
Coursework on the subject "Theoretical Foundations of Progressive Technologies"
Completed by: Belozerskaya Larisa Mirzodzhonovna, Course I
Moscow State Open University, branch
Cosmology is a physical study of the Universe, which includes the theory of the entire world covered by astronomical observations as part of the Universe.
The greatest achievement of modern cosmology was the model of the expanding universe, called the Big Bang theory.
According to this theory, the entire observable space is expanding. But what happened at the very beginning? All matter in the Cosmos at some initial moment was squeezed literally into nothing - compressed into a single point. It had a fantastically huge density - it is almost impossible to imagine, it is expressed by a number in which there are 96 zeros after one - and an equally unimaginably high temperature. Astronomers have called this state a singularity.
For some reason, this amazing balance was suddenly destroyed by the action of gravitational forces - it's hard to even imagine what they should have been with an infinitely huge density of "primary matter"!
Scientists have given the name "Big Bang" to this moment. The universe began to expand and cool.
It should be noted that the question of what was the birth of the Universe - "hot" or "cold" - was not immediately resolved unambiguously and occupied the minds of astronomers for a long time. Interest in the problem was far from idle - after all, the age of the Universe, for example, depends on the physical state of matter at the initial moment. In addition, thermonuclear reactions can take place at high temperatures. Consequently, the chemical composition of the "hot" Universe must differ from the composition of the "cold" one. And this, in turn, determines the size and rate of development of celestial bodies ...
For several decades, both versions - "hot" and "cold" birth of the Universe - existed in cosmology on an equal footing, having both supporters and critics. The matter remained "for small" - it was necessary to confirm their observations.
Modern astronomy can give an affirmative answer to the question of whether there is evidence for the hypothesis of a hot Universe and the Big Bang. In 1965, a discovery was made, which, according to scientists, directly confirms that in the past the matter of the Universe was very dense and hot. It turned out that in outer space there are electromagnetic waves that were born in that distant era, when there were no stars, no galaxies, or our solar system.
The possibility of the existence of such radiation was predicted by astronomers much earlier. In the middle of 1940s. American physicist George Gamow (1904-1968) took up the problems of the origin of the Universe and the origin of chemical elements. The calculations performed by Gamow and his students made it possible to imagine that the Universe had a very high temperature in the first seconds of its existence. The heated substance "shone" - it emitted electromagnetic waves. Gamow suggested that they should be observed in the modern era in the form of weak radio waves, and even predicted the temperature of this radiation - about 5-6 K.
In 1965, American scientists, radio engineers Arno Penzias and Robert Wilson, registered cosmic radiation that could not be attributed to any known cosmic source at that time. Astronomers have come to the conclusion that this radiation, which has a temperature of about 3 K, is a relic (from the Latin "remainder", hence the name of the radiation - "relic") of those distant times when the Universe was fantastically hot. Now astronomers have been able to make a choice in favor of the "hot" birth of the Universe. A. Penzias and R. Wilson, received in 1978 the Nobel Prize for the discovery of the cosmic microwave background (this is the official name of the cosmic microwave background) at a wavelength of 7.35 cm.
The Big Bang is the name given to the creation of the universe. Within the framework of this concept, it is assumed that the initial state of the Universe was a point called the singularity point, in which all matter and energy were concentrated. It was characterized by an infinitely high density of matter. The specific properties of the singularity point are unknown, as is unknown what preceded the singularity state.
An approximate chronology of events that followed from the zero point in time - the beginning of the expansion, is presented below:
| Time since explosion | Temperature (degrees Kelvin) | Event | Consequences |
| 0 - 5*10-44 seconds | 1,3*1032 | There is no reliable information | |
| 5*10-44 - 10-36 seconds | 1,3*1032 – 1028 | The beginning of known physical laws, the era of inflationary expansion | The expansion of the universe continues to this day |
| 10-36 - 10-4 seconds | 1028 – 1012 | The era of intermediate bosons, and then the hadron era, the existence of free quarks | |
| 10-4 - 10-3 seconds | 1012 – 1010 | The emergence of particles and antiparticles from free quarks, as well as their annihilation, the emergence of transparency of matter for neutrinos | The emergence of baryon asymmetry, the appearance of neutrino cosmic microwave background |
| 10-3 - 10-120 seconds | 1010 – 109 | The course of nuclear reactions for the fusion of helium nuclei and some other light chemical elements | Establishment of the primary ratio of chemical elements |
| Between 300 thousand - 1 million years | 3000 – 4500 | The end of the era of recombination | The appearance of CMB and neutral gas |
| 1 million - 1 billion years | 4500 – 10 | Development of gravitational inhomogeneities of gas | Formation of stars and galaxies |
Regarding the conditions and events that occurred before the moment 5·10-44 seconds - the end of the first time quantum - there is no reliable information. About the physical parameters of that era, one can only say that then the temperature was 1.3 1032 K, and the density of matter was about 1096 kg/m3. The given values are limiting for the application of existing theories. They follow from the ratios of the speed of light, the gravitational constant, Planck's and Boltzmann's constants and are called "Planck's".
The events of the period from 5·10-44 to 10-36 seconds reflect the model of the “inflationary Universe”, the description of which is difficult and cannot be given within the framework of this presentation. However, it should be noted that, according to this model, the expansion of the Universe occurred without a decrease in the volume concentration of energy and at a negative pressure of the primary mixture of matter and energy, i.e., as it were, repulsion of material objects from each other, which caused the expansion of the Universe, which continues to this day.
To understand the processes that took place in the period of 10-36-10-4 seconds from the beginning of the explosion, a deep knowledge of elementary particle physics is required. During this period, electromagnetic radiation and elementary particles - various types of mesons, hyperons, protons and antiprotons, neutrons and antineutrons, neutrinos and antineutrinos, etc. existed in balance, i.e. their volume concentrations were equal. A very important role at that time was played first by the fields of strong and then weak interactions.
In the period of 10-4 - 10-3 seconds, the formation of the entire set of elementary particles took place, which, transforming one into another, now make up the entire Universe. Annihilation of the overwhelming majority of elementary particles and antiparticles that existed earlier took place. It was during this period that the baryon asymmetry appeared, which turned out to be the result of a very small, only one billionth part, excess of the number of baryons over antibaryons. It arose, apparently, immediately after the era of the inflationary expansion of the Universe. At a temperature of 1011 degrees, the density of the Universe has already decreased to a value characteristic of atomic nuclei. During this period, the temperature halved in thousandths of a second. At the same time, the existing and now relic neutrino radiation was born. However, despite its significant density, which is no less than 400 pieces/cm3, and the possibility of obtaining with its help the most important information about that period of the formation of the Universe, its registration is not yet feasible.
In the period from 10-3 to 10-120 seconds, as a result of thermonuclear reactions, helium nuclei were formed and a very small number of nuclei of some other light chemical elements, and a significant part of the protons - hydrogen nuclei - did not undergo fusion into atomic nuclei. All of them remained immersed in the “ocean” of free electrons and photons of electromagnetic radiation. From that moment on, the ratio was established in the primary gas: 75-78% hydrogen and 25-22% helium - according to the masses of these gases.
Between 300 thousand and 1 million years, the temperature of the universe dropped to 3000 - 45000 K and the era of recombination began. Previously free electrons united with light atomic nuclei and protons. Hydrogen, helium, and some lithium atoms formed. The matter became transparent and the cosmic microwave background radiation, observed so far, “separated” from it. All currently observed features of the relic radiation, for example, fluctuations in the temperature of its streams coming from different parts of the celestial sphere or their polarization reflect the picture of the properties and distribution of matter at that time.
During the next - the first billion years of the existence of the Universe, its temperature decreased from 3000 - 45000 K to 300 K. Due to the fact that by this period of time in the Universe there were no sources of electromagnetic radiation - stars, quasars, etc., and CMB has already cooled down, this era is called the “Dark Age” of the Universe.
The idea of the development of the Universe naturally led to the formulation of the problem of the beginning of the evolution (birth) of the Universe and its
end (death). Currently, there are several cosmological models that explain certain aspects of the origin of matter in the Universe, but they do not explain the causes and process of the birth of the Universe itself. Of the totality of modern cosmological theories, only Gamow's theory of the Big Bang has been able to satisfactorily explain almost all the facts related to this problem by now. The main features of the Big Bang model have survived to this day, although they were later supplemented by the theory of inflation, or the theory of the expanding Universe, developed by the American scientists A. Gut and P. Steinhardt and supplemented by the Soviet physicist A.D. Linda.
In 1948, the outstanding American physicist of Russian origin G. Gamow suggested that the physical Universe was formed as a result of a gigantic explosion that occurred about 15 billion years ago. Then all the matter and all the energy of the Universe were concentrated in one tiny superdense clot. If you believe mathematical calculations, then at the beginning of the expansion, the radius of the Universe was completely equal to zero, and its density is equal to infinity. This initial state is called singularity - point volume with infinite density. The known laws of physics do not work in the singularity. In this state, the concepts of space and time lose their meaning, so it is meaningless to ask where this point was. Also, modern science cannot say anything about the reasons for the appearance of such a state.
However, according to the Heisenberg uncertainty principle, matter cannot be pulled into one point, so it is believed that the Universe in its initial state had a certain density and dimensions. According to some estimates, if the entire matter of the observable Universe, which is estimated at about 10 61 g, is compressed to a density of 10 94 g/cm 3 , then it will occupy a volume of about 10 -33 cm 3 . It would be impossible to see it in any electron microscope. For a long time, nothing could be said about the causes of the Big Bang and the transition of the Universe to expansion. But today there are some hypotheses trying to explain these processes. They underlie the inflationary model of the development of the Universe.
"Beginning" of the Universe
The main idea of the Big Bang concept is that the Universe in its early stages of origin had an unstable vacuum-like state with a high energy density. This energy originated from quantum radiation, i.e. as if from nothing. The fact is that in the physical vacuum there are no fixed
particles, fields and waves, but this is not a lifeless void. In a vacuum, there are virtual particles that are born, have a fleeting existence and immediately disappear. Therefore, the vacuum "boils" with virtual particles and is saturated with complex interactions between them. Moreover, the energy contained in vacuum is located, as it were, on its different floors, i.e. there is a phenomenon of differences in the energy levels of the vacuum.
While the vacuum is in equilibrium, there are only virtual (ghostly) particles in it, which borrow energy from the vacuum for a short period of time to be born, and quickly return the borrowed energy to disappear. When the vacuum, for some reason, at a certain starting point (singularity) was excited and left the state of equilibrium, then virtual particles began to capture energy without recoil and turned into real particles. In the end, at a certain point in space, a huge number of real particles were formed, along with the energy associated with them. When the excited vacuum collapsed, a gigantic radiation energy was released, and the superpower compressed the particles into superdense matter. The extreme conditions of the "beginning", when even space-time was deformed, suggest that the vacuum was also in a special state, which is called a "false" vacuum. It is characterized by an energy of extremely high density, which corresponds to an extremely high density of matter. In this state of matter, strongest stresses, negative pressures can arise in it, equivalent to a gravitational repulsion of such magnitude that it caused an unrestrained and rapid expansion of the Universe - the Big Bang. This was the first impulse, the “beginning” of our world.
From this moment, the rapid expansion of the Universe begins, time and space arise. At this time, there is an unrestrained inflation of "bubbles of space", the embryos of one or several universes, which may differ from each other in their fundamental constants and laws. One of them became the embryo of our Metagalaxy.
According to various estimates, the period of "inflation", going exponentially, takes an unimaginably short period of time - up to 10 - 33 s after the "beginning". It is called inflation period. During this time, the size of the universe has increased 1050 times, from a billionth of the size of a proton to the size of a matchbox.
By the end of the inflation phase, the universe was empty and cold, but when inflation dried up, the universe suddenly became extremely "hot". This burst of heat that lit up the cosmos is due to the huge reserves of energy contained in the "false" vacuum. This state of vacuum is very unstable and tends to decay. When
the decay ends, the repulsion disappears, and so does inflation. And the energy, bound in the form of many real particles, was released in the form of radiation, which instantly heated the Universe to 10 27 K. From that moment on, the Universe developed according to the standard theory of the “hot” Big Bang.
Early evolution of the universe
Immediately after the Big Bang, the Universe was a plasma of elementary particles of all kinds and their antiparticles in a state of thermodynamic equilibrium at a temperature of 10 27 K, which freely transformed into each other. Only gravitational and large (Great) interactions existed in this bunch. Then the Universe began to expand, at the same time its density and temperature decreased. The further evolution of the Universe took place in stages and was accompanied, on the one hand, by differentiation, and, on the other hand, by the complication of its structures. The stages of the evolution of the Universe differ in the characteristics of the interaction of elementary particles and are called eras. The most important changes took less than three minutes.
hadron era lasted 10 -7 s. At this stage, the temperature drops to 10 13 K. At the same time, all four fundamental interactions appear, the free existence of quarks ceases, they merge into hadrons, the most important of which are protons and neutrons. The most significant event was the global symmetry breaking that occurred in the first moments of the existence of our Universe. The number of particles turned out to be slightly larger than the number of antiparticles. The reasons for this asymmetry are still unknown. In a common plasma-like bunch, for every billion pairs of particles and antiparticles, one particle turned out to be more, it lacked a pair for annihilation. This determined the further appearance of the material Universe with galaxies, stars, planets and intelligent beings on some of them.
lepton era lasted up to 1 s after the onset. The temperature of the Universe dropped to 10 10 K. Its main elements were leptons, which participated in the mutual transformations of protons and neutrons. At the end of this era, matter became transparent to neutrinos, they stopped interacting with matter and have since survived to the present day.
Radiation era (photon era) lasted 1 million years. During this time, the temperature of the Universe decreased from 10 billion K to 3000 K. During this stage, the processes of primary nucleosynthesis, the most important for the further evolution of the Universe, took place - the combination of protons and neutrons (there were about 8 times less
less than protons) into atomic nuclei. By the end of this process, the matter of the Universe consisted of 75% of protons (hydrogen nuclei), about 25% were helium nuclei, hundredths of a percent fell on deuterium, lithium and other light elements, after which the Universe became transparent to photons, since the radiation separated from matter and formed what in our era is called relic radiation.
Then, for almost 500 thousand years, no qualitative changes occurred - the Universe slowly cooled and expanded. The universe, while remaining homogeneous, became increasingly rarefied. When it cooled down to 3000 K, the nuclei of hydrogen and helium atoms could already capture free electrons and turn into neutral hydrogen and helium atoms. As a result, a homogeneous Universe was formed, which was a mixture of three almost non-interacting substances: baryon matter (hydrogen, helium and their isotopes), leptons (neutrinos and antineutrinos) and radiation (photons). By this time there were no high temperatures and high pressures. It seemed that in the long term the Universe was waiting for further expansion and cooling, the formation of a "lepton desert" - something like heat death. But this did not happen; on the contrary, there was a jump that created the modern structural Universe, which, according to modern estimates, took from 1 to 3 billion years.
In the scientific world, it is generally accepted that the Universe originated as a result of the Big Bang. This theory is based on the fact that energy and matter (the foundations of all things) were previously in a state of singularity. It, in turn, is characterized by the infinity of temperature, density and pressure. The singularity state itself defies all the laws of physics known to the modern world. Scientists believe that the Universe arose from a microscopic particle, which, due to unknown reasons, came into an unstable state in the distant past and exploded.
The term "Big Bang" began to be used since 1949 after the publication of the works of the scientist F. Hoyle in popular science publications. Today, the theory of the “dynamic evolving model” has been developed so well that physicists can describe the processes occurring in the Universe as early as 10 seconds after the explosion of a microscopic particle that laid the foundation for everything.
There are several proofs of the theory. One of the main ones is the relic radiation, which permeates the entire Universe. It could have arisen, according to modern scientists, only as a result of the Big Bang, due to the interaction of microscopic particles. It is the relic radiation that makes it possible to learn about those times when the Universe looked like a blazing space, and there were no stars, planets and the galaxy itself. The second proof of the birth of everything that exists from the Big Bang is the cosmological redshift, which consists in a decrease in the frequency of radiation. This confirms the removal of stars, galaxies from the Milky Way in particular and from each other in general. That is, it indicates that the Universe expanded earlier and continues to do so until now.
A Brief History of the Universe
- 10 -45 - 10 -37 sec- inflation expansion
- 10 -6 sec- the emergence of quarks and electrons
- 10 -5 sec- the formation of protons and neutrons
- 10 -4 sec - 3 min- the emergence of nuclei of deuterium, helium and lithium
- 400 thousand years- formation of atoms
- 15 million years- continued expansion of the gas cloud
- 1 billion years- the birth of the first stars and galaxies
- 10 - 15 billion years- the emergence of planets and intelligent life
- 10 14 billion years- termination of the process of birth of stars
- 10 37 billion years- depleting the energy of all stars
- 10 40 billion years- evaporation of black holes and the birth of elementary particles
- 10 100 billion years- completion of the evaporation of all black holes
The Big Bang theory has become a real breakthrough in science. It allowed scientists to answer many questions regarding the birth of the universe. But at the same time, this theory gave rise to new mysteries. Chief among them is the cause of the Big Bang itself. The second question to which modern science has no answer is how space and time appeared. According to some researchers, they were born together with matter, energy. That is, they are the result of the Big Bang. But then it turns out that time and space must have some kind of beginning. That is, a certain entity, constantly existing and not dependent on their indicators, could well initiate the processes of instability in a microscopic particle that gave rise to the Universe.
The more research is done in this direction, the more questions arise for astrophysicists. The answers to them await humanity in the future.
by discipline Concepts of modern natural science
"Origin of the Universe. Big bang concept. Properties of the megaworld»
1. Introduction
2. The origin of the universe - the theory of the "Big Bang"
3. General characteristics of the megaworld
4. Properties of the mega world
Conclusion
Bibliography
Introduction
Mankind has always been interested in everything that is shrouded in secrets, and the Universe is the largest receptacle of the unknown. The universe is the entire existing material world, boundless in time and space and infinitely diverse in the forms that matter takes in the process of its development. And, of course, it was always interesting to know how it all began? The search for an answer to this question remains relevant in our time, and the problem of the evolution of the Universe occupies a central place in natural science. Accordingly, there are many different concepts that try to explain this phenomenon.
Using the achievements of various sciences, such as physics, mathematics, philosophy, a new science arose - cosmology. This is a set of accumulated theoretical provisions on the structure of matter and the structure of the Universe, as an integral object, as well as individual scientific knowledge of the world covered by astronomical observations as part of the Universe. The subject of cosmology is the entire mega world around us, and the task is to describe the most general properties, structure and evolution of the universe. In modern times, by the way, cosmogony is born - the science of the origin and development of cosmic bodies and their systems.
Modern astronomy has not only discovered the grandiose world of galaxies, but also discovered unique phenomena: the expansion of the Metagalaxy, the cosmic abundance of chemical elements, cosmic microwave background radiation, indicating that the Universe is continuously evolving.
The evolution of the structure of the Universe is associated with the emergence of clusters of galaxies, the separation and formation of stars and galaxies, the formation of planets and their satellites. The Universe itself arose about 20 billion years ago from some dense and hot protomatter. There is a point of view that from the very beginning the protosubstance will expand at a gigantic speed. At the initial stage, this dense substance scattered in all directions and was a homogeneous seething mixture of unstable particles constantly disintegrating upon collision. Cooling down and interacting over millions of years, all this mass of matter dispersed in space was concentrated into large and small gas formations, which over hundreds of millions of years, approaching and merging, turned into huge complexes. In these complexes, in turn, denser regions arose - subsequently, stars and even entire galaxies were formed there.
As a result of gravitational instability, dense “protostellar formations” with masses close to the mass of the Sun can form in different zones of the formed galaxies. The compression process that has begun will accelerate under the influence of its own gravitational field. This process accompanies the free fall of cloud particles to its center - gravitational compression occurs. In the center of the cloud, a seal is formed, consisting of molecular hydrogen and helium. An increase in density and temperature in the center leads to the disintegration of molecules into atoms, ionization of atoms, and the formation of a dense core of a protostar.
There is a hypothesis about the cyclic state of the Universe. Having once arisen from a superdense clot of matter, the Universe, perhaps already in the first cycle, gave birth to billions of star systems and planets within itself. And then the Universe begins to strive towards the state from which the history of the cycle began. In the end, the matter of the Universe returns to its original superdense state, destroying all life that got in the way. And so it is repeated every time, in every cycle for eternity.
Origin of the Universe - Big Bang Theory
The Universe itself arose about 20 billion years ago from some dense and hot protomatter. Today, one can only guess what this substance that gave rise to the Universe was, how it was formed, what laws it obeyed, and what kind of processes led it to expand. There is a point of view that from the very beginning protomatter began to expand at a gigantic speed.
At the initial stage, this dense substance flew apart in all directions and was a homogeneous seething mixture of unstable particles constantly disintegrating during collisions. Cooling down and interacting over millions of years, all this mass of matter dispersed in space was concentrated into large and small gas formations, which over hundreds of millions of years, approaching and merging, turned into huge complexes. In turn, denser areas arose in them - subsequently, stars and even entire galaxies were formed there.
Is the Universe finite or infinite, what is its geometry - these and many other questions are connected with the evolution of the Universe, in particular with the observed expansion. If, as is currently believed, the speed of the "expansion" of galaxies increases by 75 km / s for every million parsecs, then extrapolation to the past leads to a surprising result: approximately 10-20 billion years ago, the entire Universe was concentrated in a very small area . Many scientists believe that at that time the density of the universe was the same as that of an atomic nucleus: the universe was one giant "nuclear drop". For some reason, this "drop" came into an unstable state and exploded. We are now seeing the consequences of this explosion as systems of galaxies. The model of the hot exploding Universe was developed by Friedman's student J. Gamow in the late 1940s, laying the foundation for the so-called "Big Bang" theory, but this theory became widespread only in the mid-1960s.
Asking about what was before the Big Bang and what is beyond this expanding world is meaningless. The universe, according to the Big Bang theory, is limited in space and time, at least from the side of the past. Such a difficult-to-understand picture followed from Friedman's formulas. Soon, however, the American astronomer E. Hubble confirmed the fact of the space expanding around us by measuring the speed of this phenomenon. Thanks to this, it became possible to measure the time of the existence of the Universe - approximately 15-20 billion years.
Before the explosion, there was no matter, no time, no space. Events in the first second proceeded rapidly. First, radiations (photons) were formed, then particles and substances (quarks and antiquarks). Within the same second, protons, antiprotons and neutrons were formed from them. When a proton and an antiproton collide, which, as is known, differ from each other in opposite charges, an annihilation reaction occurs, during which both particles disappear, leaving radiation (photons). These reactions became quite frequent, since the substance of the "newborn" Universe was very dense - the particles constantly collided with each other. The universe was dominated by radiation.
By the end of the first second, when the temperature dropped to 10 billion degrees, new particles were formed, including the electron and its antiparticle, the positron. By this time, most of the particles had already annihilated. It so happened that the number of particles was a tiny fraction of a percent greater than the number of antiparticles (this fact has not yet been explained), as a result of which our universe consists of matter, and not of antimatter.
By the third minute, helium nuclei formed from a quarter of all protons and neutrons. A few hundred years later, the ever-expanding universe cooled down enough that protons and helium nuclei could hold electrons around them. This is how helium and hydrogen atoms were formed. Radiation, unrestrained by the freer electrons, could now propagate over vast distances. In the Universe, which has cooled down significantly (for 15 billion years), in our time we can hear the “echoes” of that radiation - it is microwave, and, coming evenly from all sides, corresponds to the radiation of a body heated to only 3 K. It is accepted called cosmic background radiation. Its discovery and existence support the Big Bang theory.
With the expansion in the Universe, areas of accumulation of matter began to form, as well as areas where it was almost absent. under the influence of gravity, these compactions grew and in their place galaxies, clusters and superclusters of galaxies began to form.
Supplemented by the theory of nuclear reactions in matter cooling down as it expands, the Big Bang theory made it possible to calculate the relative concentrations of hydrogen, deuterium, and heavier chemical elements in nature.
At the end of the XX century. This theory has become almost universally accepted in cosmology.
General characteristics of the megaworld
Modern science considers the mega world as an interacting and developing system of celestial bodies.
There is no clear boundary between the mega world and the macro world. It is usually believed that it begins with distances of about m and masses of kg.
Since the megaworld deals with large distances, special units have been introduced for their measurement: the astronomical unit, the light year and the parsec.
An astronomical unit is the average distance from the Earth to the Sun, equal to 1.5 m.
A light year is the distance that light travels in one year, namely 9.46m.
Parsec (parallax-second) - the distance at which the annual parallax of the earth's orbit (i.e. the angle at which the semi-major axis of the earth's orbit is visible, located perpendicular to the line of sight) is equal to one second. This distance is 206265 AU. \u003d 3.08 \u003d 3.26 s.g.
Celestial bodies throughout the universe form systems of varying complexity. All existing galaxies are included in the system of the highest order - the Metagalaxy. The dimensions of the Metagalaxy are very large: the radius of the cosmological horizon is 15-20 billion light years. d. The concepts of "Universe" and "Metagalaxy" are very close concepts: they characterize the same object, but in different aspects. The concept of "Universe" means the entire existing material world; the concept of "Metagalaxy" - the same world, but from the point of view of its structure - as an ordered system of galaxies. Metagalaxy - is a collection of star systems - galaxies, and its structure is determined by their distribution in space filled with extremely rarefied intergalactic gas and penetrated by intergalactic rays. According to modern concepts, a metagalaxy is characterized by a cellular (network, porous) structure. The age of the Metagalaxy is close to the age of the Universe, since the formation of the structure falls on the period following the separation of matter and radiation. According to modern data, the age of the Metagalaxy is estimated at 15 billion years.
A galaxy is a giant system consisting of clusters of stars and nebulae that form a rather complex configuration in space.
According to their shape, galaxies are conditionally divided into three types: elliptical, spiral, and irregular.
At the present stage of the evolution of the Universe, the matter in it is predominantly in the stellar state. 97% of the matter in our Galaxy is concentrated in stars, which are giant plasma formations of various sizes, temperatures, with different motion characteristics. In many other galaxies, if not most, "stellar substance" makes up more than 99.9% of their mass. The age of stars varies over a fairly large range of values: from 15 billion years, corresponding to the age of the Universe, to hundreds of thousands - the youngest. There are stars that are currently being formed and are in the protostellar stage, i.e. they have not yet become real stars. At the final stage of evolution, stars turn into inert (“dead”) stars. Stars do not exist in isolation, but form systems.
The solar system is a group of celestial bodies, very different in size and physical structure. This group includes: the Sun, nine large planets, dozens of satellites of planets, thousands of small planets (asteroids), hundreds of comets and countless meteorite bodies moving both in swarms and in the form of individual particles. All these bodies are united into one system due to the force of attraction of the central body - the Sun. The solar system is an ordered system that has its own patterns of structure. The unified character of the solar system is manifested in the fact that all the planets revolve around the sun in the same direction and almost in the same plane. The sun, planets, satellites of planets rotate around their axes in the same direction in which they move along their trajectories. The structure of the solar system is also natural: each next planet is approximately twice as far from the Sun as the previous one.
The first theories of the origin of the solar system were put forward by the German philosopher I. Kant and the French mathematician P. S. Laplace. According to this hypothesis, the system of planets around the Sun was formed as a result of the action of forces of attraction and repulsion between particles of scattered matter (nebula), which is in rotation around the Sun.
Properties of the mega world
The first astronomical knowledge was obtained by the thinkers of the Ancient East - Egypt, Babylonia, India, China. Astronomers of the ancient world learned to predict the onset of eclipses, followed the movement of the planets. This astronomical knowledge, accumulated in the 7th-6th centuries. BC, borrowed by the ancient Greeks.
In the VI century BC. The scientist and philosopher of ancient Greece, Aristotle, actually put forward the idea of the geocentric structure of the universe. Aristotle believed that the Earth and all celestial bodies are spherical, that the Earth is the fixed center of the Universe around which all celestial bodies revolve. The universe, according to Aristotle, has finite dimensions, it is as if closed by the sphere of stars. After Aristotle in the III century BC. Greek astronomer Aristarchus of Samos put forward the idea that the Earth revolves around the Sun, that the distance from the Earth to the Sun is 600 Earth diameters. Unfortunately, contemporaries did not understand him and did not accept his idea. In the II century BC. finally formed the geocentric system of the world. The Alexandrian astronomer Ptolemy generalized the ideas that existed before him and proposed his own model of the Universe. According to Ptolemy, the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn and the sky of fixed stars move around the spherical and motionless Earth. Each of the planets, according to Ptolemy, has the center of its movement not the Earth, but a certain point. This point, in turn, moves along a circle, in the center of which is the Earth.
The heliocentric system of the world is associated with the name of the Polish scientist Nicolaus Copernicus (XV century). He revived the hypothesis of Aristarchus of Samos about the structure of the world: the Earth gave way to the center of the Sun and turned out to be the third in a row among the planets rotating in circular orbits. At the same time, the scientist believed that the stars are fixed, the Universe is limited by the sphere of fixed stars.
The idea of the infinity of the universe was developed by Giordano Bruno (XVI century). According to Bruno, the Sun is a star, there are infinitely many such stars, planets revolve around the stars, like the Earth, which revolves around the Sun. Bruno conjectured that both the Sun and the stars revolve around their axes, and in the solar system, in addition to the known planets, there are others that have not yet been discovered.
With the invention of the telescope, Galileo Galilei made an outstanding discovery in the first half of the 17th century, which confirmed the teachings of Copernicus and Bruno's guesses. Galileo came to the conclusion that rotation is inherent not only to the Earth, but also to other celestial bodies. Simultaneously with Galileo, outstanding discoveries in astronomy were made by Johannes Kepler, who formulated the laws of motion of bodies in the solar system.
The task of modern astronomy is not only to explain the data of astronomical observations, but also to study the evolution of the Universe. These questions are considered by cosmology. When studying the Universe, it is impossible to conduct an empirical verification of the results of the study, therefore the conclusions of cosmology are called not laws, but models of the origin and development of the Universe. A model is a diagram of a certain fragment of natural or social reality, a possible variant of its explanation. In the process of development of science, the old model is replaced by a new model. At the heart of modern cosmology is an evolutionary approach to the questions of the origin and development of the Universe, in accordance with which a model of the expanding Universe has been developed.
A. Einstein's general theory of relativity served as a key prerequisite for creating a model of an evolving expanding universe. The object of the theory of relativity is physical events. Physical events characterize the concepts of space, time, matter, motion, which are considered in unity in the theory of relativity. Based on the unity of space, matter and time, it follows that with the disappearance of metrics, space and time will also disappear. Therefore, before the creation of the universe, there was neither space nor time. Einstein derived fundamental equations that relate the distribution of matter with the geometric properties of space, with the passage of time, and based on them developed a statistical model of the universe. According to this model, the Universe has the following properties:
1. homogeneity, that is, it has the same properties at all points;
2. isotropic, that is, it has the same properties in all directions;
3. The third property follows from the Hubble law: “the farther the galaxies are separated from each other, the faster they move away from each other”, that is, the Universe is non-stationary - it is in a state of constant expansion; the expansion acceleration agent is dark energy;
4. In the XX century, one more property of the Universe is supplemented - it is hot.
At present, there is an assumption that the Universe arose from a "singular point" - the initial state of the Universe - by the Big Bang of this initial cosmic matter. In addition to and development of the concept of the Big Bang, the theory of inflation arose, which says that the Universe arose from a vacuum.
Convincing arguments confirming the validity of the cosmological model of the expanding Universe are the established facts. These facts include the following:
1. expansion of the Universe in accordance with the Hubble law;
2. homogeneity of luminous matter at distances of the order of 100 Mcp;
3. the existence of a relict radiation background with a thermal spectrum corresponding to a temperature of 2.7 K.
Conclusion
Since ancient times, people have been trying to find explanations for the incomprehensibility and bizarreness of the world around them, but it is most difficult to do this in a world that is practically impossible to study. However, scientists have done tremendous work in the study of the Universe and made a huge number of discoveries. Although much has not yet been proven, it is enough that we are significantly closer to unraveling the misunderstood.
Bibliography
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5. Novikov I.D. How the universe exploded. – M.: Nauka, 1988.
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The Big Bang theory is now considered as certain as the Copernican system. However, until the second half of the 1960s, it did not enjoy universal recognition, and not only because many scientists from the threshold denied the very idea of the expansion of the Universe. It's just that this model had a serious competitor.
In 11 years, cosmology as a science will be able to celebrate its centenary. In 1917, Albert Einstein realized that the equations of general relativity theory allow one to calculate physically reasonable models of the universe. Classical mechanics and the theory of gravity do not provide such an opportunity: Newton tried to build a general picture of the Universe, but in all cases it inevitably collapsed under the influence of gravity.
Einstein strongly did not believe in the beginning and end of the universe and therefore came up with an ever-existing static universe. To do this, he needed to introduce into his equations a special component that created "anti-gravity" and thus formally ensured the stability of the world order. Einstein considered this addition (the so-called cosmological term) inelegant, ugly, but still necessary (the author of general relativity did not believe his aesthetic instinct in vain - later it was proved that the static model is unstable and therefore physically meaningless).
Einstein's model quickly had competitors - the model of the world without matter by Willem de Sitter (1917), closed and open non-stationary models by Alexander Friedman (1922 and 1924). But these beautiful constructions remained for the time being purely mathematical exercises. To talk about the universe as a whole is not speculative, you must at least know that there are worlds located outside the star cluster in which the solar system is located and we are with it. And cosmology was able to seek support in astronomical observations only after Edwin Hubble published his work "Extragalactic Nebulae" in 1926, where the description of galaxies as independent star systems that are not part of the Milky Way was given for the first time.
The creation of the universe did not take six days at all - the bulk of the work was completed much earlier. Here is his approximate chronology.
0. Big bang.
Planck era: 10-43 p. Planck moment. There is a separation of gravitational interaction. The size of the Universe at this moment is 10-35 m (the so-called Planck length). 10-37 p. inflationary expansion of the universe.
The era of the great unification: 10-35 p. Separation of strong and electroweak interactions. 10-12 s. Separation of the weak interaction and the final separation of interactions.
Hadron era: 10-6 s. Annihilation of proton-antiproton pairs. Quarks and antiquarks cease to exist as free particles.
Lepton era: 1 s. Hydrogen nuclei are formed. Nuclear fusion of helium begins.
Era of Nucleosynthesis: 3 minutes. The universe is made up of 75% hydrogen and 25% helium, as well as trace amounts of heavy elements.
Radiation era: 1 week. By this time, the radiation is thermalized.
The era of matter: 10 thousand years. Matter begins to dominate the universe. 380 thousand years. Hydrogen nuclei and electrons recombine, the Universe becomes transparent to radiation.
Star era: 1 billion years. Formation of the first galaxies. 1 billion years. Formation of the first stars. 9 billion years. The formation of the solar system. 13.5 billion years. This moment
Receding galaxies
This chance was quickly realized. The Belgian Georges Henri Lemaitre, who studied astrophysics at the Massachusetts Institute of Technology, heard rumors that Hubble had come close to a revolutionary discovery - proof of the recession of galaxies. In 1927, after returning to his homeland, Lemaitre published (and in subsequent years he refined and developed) a model of the Universe formed as a result of an explosion of superdense matter expanding in accordance with the equations of general relativity. He proved mathematically that their radial velocity should be proportional to their distance from the solar system. A year later, Princeton mathematician Howard Robertson independently arrived at the same conclusion.
And in 1929, Hubble obtained the same dependence experimentally by processing data on the distance of twenty-four galaxies and the redshift of the light coming from them. Five years later, Hubble and his assistant observer Milton Humason provided new evidence for this conclusion by monitoring very faint galaxies at the extreme periphery of observable space. The predictions of Lemaitre and Robertson were fully justified, and the cosmology of the non-stationary Universe, it would seem, won a decisive victory.
Unrecognized model
But still, astronomers were in no hurry to shout cheers. Lemaitre's model made it possible to estimate the duration of the existence of the Universe - for this it was only necessary to find out the numerical value of the constant included in the Hubble equation. Attempts to determine this constant led to the conclusion that our world arose only about two billion years ago. However, geologists argued that the Earth is much older, and astronomers had no doubt that the space is full of stars of a more respectable age. Astrophysicists also had their own reasons for distrust: the percentage composition of the distribution of chemical elements in the Universe based on the Lemaitre model (this work was first done in 1942 by Chandrasekhar) clearly contradicted reality.
The skepticism of specialists was also explained by philosophical reasons. The astronomical community has just got used to the idea that an endless world populated by many galaxies has opened up before it. It seemed natural that in its foundations it does not change and exists forever. And now scientists were asked to admit that the Cosmos is finite not only in space, but also in time (besides, this idea suggested a divine creation). Therefore, Lemaitre's theory remained out of work for a long time. However, an even worse fate befell the model of an eternally oscillating universe, proposed in 1934 by Richard Tolman. It did not receive serious recognition at all, and in the late 1960s it was rejected as mathematically incorrect.
The ballooning world stock did not rise much after George Gamow and his graduate student Ralph Alfer built a new, more realistic version of the model in early 1948. Lemaitre's universe was born from the explosion of a hypothetical "primary atom", which clearly went beyond the physicists' ideas about the nature of the microworld.
For a long time, Gamow's theory was called quite academically - "dynamic evolving model". And the phrase "Big Bang", oddly enough, was introduced into circulation not by the author of this theory, and not even by its supporter. In 1949, BBC science producer Peter Laslett suggested that Fred Hoyle prepare a series of five lectures. Hoyle shone in front of the microphone and instantly gained a lot of fans among radio listeners. In his last speech, he talked about cosmology, spoke about his model, and finally decided to settle scores with competitors. Their theory, Hoyle said, "is based on the assumption that the universe came into being in the process of a single powerful explosion and therefore exists only for a finite time ... This idea of the Big Bang seems to me completely unsatisfactory." This is how the expression first appeared. It can also be translated into Russian as "Big Cotton", which probably corresponds more closely to the pejorative meaning of u that Hoyle put into it. A year later, his lectures were published, and the new term went around the world.
George Gamow and Ralph Alpher proposed that the universe soon after its birth consisted of well-known particles - electrons, photons, protons and neutrons. In their model, this mixture was heated to high temperatures and tightly packed in a tiny (compared to today's) volume. Gamow and Alfer showed that thermonuclear fusion occurs in this super-hot soup, as a result of which the main isotope of helium, helium-4, is formed. They even calculated that after a few minutes, matter passes into an equilibrium state in which there are about a dozen hydrogen nuclei for each helium nucleus.
This proportion was in full agreement with astronomical data on the distribution of light elements in the universe. These conclusions were soon confirmed by Enrico Fermi and Anthony Turkevich. They also found that fusion processes must produce some of the light isotope helium-3 and the heavy isotopes of hydrogen, deuterium and tritium. Their estimates of the concentration of these three isotopes in outer space also coincided with the observations of astronomers.
Problem theory
But practical astronomers continued to doubt. First, there remained the problem of the age of the Universe, which Gamow's theory could not solve. It was possible to increase the duration of the existence of the world only by proving that galaxies fly apart much more slowly than is commonly believed (in the end, this happened, and to a large extent with the help of observations made at the Palomar Observatory, but already in the 1960s).
Secondly, Gamow's theory stalled on nucleosynthesis. Having explained the origin of helium, deuterium, and tritium, she could not move on to heavier nuclei. The helium-4 nucleus consists of two protons and two neutrons. Everything would be fine if it could attach a proton and turn into a lithium nucleus. However, nuclei of three protons and two neutrons or two protons and three neutrons (lithium-5 and helium-5) are extremely unstable and decay instantly. Therefore, only stable lithium-6 (three protons and three neutrons) exists in nature. For its formation by direct fusion, it is necessary that both a proton and a neutron simultaneously merge with the helium nucleus, and the probability of this event is extremely small. True, under conditions of high density of matter in the first minutes of the existence of the Universe, such reactions still occasionally occur, which explains the very low concentration of the most ancient lithium atoms.
Nature has prepared Gamow another unpleasant surprise. The path to heavy elements could also lie through the fusion of two helium nuclei, but this combination is also not viable. There was no way to explain the origin of elements heavier than lithium, and in the late 1940s this obstacle seemed insurmountable (now we know that they are born only in stable and exploding stars and in cosmic rays, but Gamow did not know this).
However, the model of the "hot" birth of the Universe had one more card in reserve, which eventually became a trump card. In 1948, Alpher and Gamow's other assistant, Robert German, came to the conclusion that the cosmos is permeated with microwave radiation that arose 300,000 years after the primary cataclysm. However, radio astronomers showed no interest in this prediction, and it remained on paper.
The emergence of a competitor
Gamow and Alfer invented their "hot" model in the US capital, where from 1934 Gamow taught at the George Washington University. Many productive ideas came to them while drinking moderately at the Little Vienna bar on Pennsylvania Avenue near the White House. And if this path to constructing a cosmological theory seems exotic to some, what about the horror movie-influenced alternative?
Fred Hoyle: The expansion of the universe goes on forever! Matter is born spontaneously in the void at such a rate that the average density of the universe remains constant
In good old England, at the University of Cambridge, after the war, three remarkable scientists settled - Fred Hoyle, Herman Bondi and Thomas Gold. Before that, they worked in the radar laboratory of the British Navy, where they became friends. Hoyle, an Englishman from Yorkshire, was not yet 30 at the time of the surrender of Germany, and his friends, natives of Vienna, turned 25. Hoyle and his friends in their "radar era" took their souls in conversations about the problems of the universe and cosmology. All three disliked Lemaitre's model, but Hubble's law was taken seriously, and therefore rejected the concept of a static universe. After the war, they met at Bondy's and discussed the same problems. The insight descended after watching the horror movie "Dead in the Night". Its main character, Walter Craig, got into a closed event loop, which at the end of the picture returned him to the same situation that started it all. A film with such a plot can go on indefinitely (like a poem about a priest and his dog). It was then that Gold realized that the Universe could turn out to be an analogue of this plot - simultaneously changing and unchanged!
Friends thought the idea was crazy, but then they decided that there was something in it. Together they turned the hypotheses y into a coherent theory. Bondy and Gold gave its general presentation, and Hoyle, in a separate publication "A New Model of the Expanding Universe" - mathematical calculations. He took the equations of general relativity as a basis, but supplemented them with a hypothetical "field of creation" (Creation field, C-field), which has a negative pressure. Something like this appeared 30 years later in inflationary cosmological theories, which Hoyle emphasized with no small pleasure.
Steady state cosmology
The new model entered the history of science as Steady State Cosmology. She proclaimed the complete equality of not only all points of space (Einstein had this), but also all moments of time: the Universe expands, but has no beginning, since it always remains similar to itself. Gold called this statement the perfect cosmological principle. The geometry of space in this model remains flat, as in Newton. The galaxies scatter, but in space "from nothing" (more precisely, from the field of creation) new matter appears, and with such intensity that the average density of matter remains unchanged. In accordance with the then known value of the Hubble constant, Hoyle calculated that only one particle is born in every cubic meter of space for 300,000 years. The question was immediately removed why the instruments do not register these processes - they are too slow by human standards. The new cosmology did not experience any difficulties associated with the age of the Universe, this problem simply did not exist for it.
To confirm his model, Hoyle suggested using data on the spatial distribution of young galaxies. If the C-field uniformly creates matter everywhere, then the average density of such galaxies should be approximately the same. On the contrary, the model of the cataclysmic birth of the Universe predicts that this density is maximum at the far edge of the observable space - from there the light of star clusters that have not yet grown old comes to us. Hoyle's criterion was perfectly reasonable, but at that time it was not possible to test it due to the lack of sufficiently powerful telescopes.
Triumph and defeat
For more than 15 years, rival theories have fought almost evenly. True, in 1955, the English radio astronomer and future Nobel laureate Martin Ryle discovered that the density of weak radio sources on the cosmic periphery is greater than near our galaxy. He stated that these results are inconsistent with Steady State Cosmology. However, after a few years, his colleagues came to the conclusion that Ryle exaggerated the differences in densities, so the question remained open.
But in his twentieth year, Hoyle's cosmology began to fade rapidly. By that time, astronomers had proved that the Hubble constant was an order of magnitude smaller than previous estimates, which made it possible to raise the estimated age of the Universe to 10-20 billion years (the current estimate is 13.7 billion years ± 200 million). And in 1965, Arno Penzias and Robert Wilson registered the radiation predicted by Alpher and Herman and thereby immediately attracted a great number of supporters to the Big Bang theory.
For forty years now, this theory has been considered the standard and generally accepted cosmological model. She also has competitors of different ages, but no one takes Hoyle's theory seriously anymore. She was not helped even by the discovery (in 1999) of the acceleration of the expansion of galaxies, the possibility of which both Hoyle and Bondy and Gold wrote about. Her time is irrevocably gone.
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