What do we know about the universe, what is space like? The Universe is a boundless world difficult to comprehend by the human mind, which seems unreal and intangible. In fact, we are surrounded by matter, limitless in space and time, capable of taking various forms. To try to understand the true scale of outer space, how the Universe works, the structure of the universe and the processes of evolution, we will need to cross the threshold of our own worldview, look at the world around us from a different angle, from the inside.
Education of the Universe: first steps
The space that we observe through telescopes is only part of the stellar Universe, the so-called Megagalaxy. The parameters of Hubble's cosmological horizon are colossal - 15-20 billion light years. These data are approximate, since in the process of evolution the Universe is constantly expanding. The expansion of the Universe occurs through the spread of chemical elements and cosmic microwave background radiation. The structure of the Universe is constantly changing. Clusters of galaxies, objects and bodies of the Universe appear in space - these are billions of stars that form the elements of near space - star systems with planets and satellites.
Where is the beginning? How did the Universe come into being? Presumably the age of the Universe is 20 billion years. Perhaps the source of cosmic matter was hot and dense promaterial, the accumulation of which exploded at a certain moment. The smallest particles formed as a result of the explosion scattered in all directions, and continue to move away from the epicenter in our time. The Big Bang theory, which now dominates scientific circles, most accurately describes the formation of the Universe. The substance that emerged as a result of the cosmic cataclysm was a heterogeneous mass consisting of tiny unstable particles that, colliding and scattering, began to interact with each other.
The Big Bang is a theory of the origin of the Universe that explains its formation. According to this theory, there initially existed a certain amount of matter, which, as a result of certain processes, exploded with colossal force, scattering the mass of the mother into the surrounding space.
After some time, by cosmic standards - an instant, by earthly chronology - millions of years, the stage of materialization of space began. What is the Universe made of? The scattered matter began to concentrate into clumps, large and small, in the place of which the first elements of the Universe, huge gas masses—nurseries of future stars—subsequently began to emerge. In most cases, the process of formation of material objects in the Universe is explained by the laws of physics and thermodynamics, but there are a number of points that cannot yet be explained. For example, why is expanding matter more concentrated in one part of space, while in another part of the universe matter is very rarefied? Answers to these questions can only be obtained when the mechanism of formation of space objects, large and small, becomes clear.
Now the process of formation of the Universe is explained by the action of the laws of the Universe. Gravitational instability and energy in different areas triggered the formation of protostars, which in turn, under the influence of centrifugal forces and gravity, formed galaxies. In other words, while matter continued and continues to expand, compression processes began under the influence of gravitational forces. Particles of gas clouds began to concentrate around an imaginary center, eventually forming a new compaction. The building materials in this gigantic construction project are molecular hydrogen and helium.
The chemical elements of the Universe are the primary building material from which the objects of the Universe were subsequently formed
Then the law of thermodynamics begins to operate, and the processes of decay and ionization are activated. Hydrogen and helium molecules disintegrate into atoms, from which the core of a protostar is formed under the influence of gravitational forces. These processes are the laws of the Universe and have taken the form of a chain reaction, occurring in all distant corners of the Universe, filling the universe with billions, hundreds of billions of stars.
Evolution of the Universe: highlights
Today, in scientific circles there is a hypothesis about the cyclical nature of the states from which the history of the Universe is woven. Arising as a result of the explosion of promaterial, gas clusters became nurseries for stars, which in turn formed numerous galaxies. However, having reached a certain phase, matter in the Universe begins to tend to its original, concentrated state, i.e. the explosion and subsequent expansion of matter in space is followed by compression and a return to a superdense state, to the starting point. Subsequently, everything repeats itself, the birth is followed by the finale, and so on for many billions of years, ad infinitum.
The beginning and end of the universe in accordance with the cyclical evolution of the Universe
However, omitting the topic of the formation of the Universe, which remains an open question, we should move on to the structure of the universe. Back in the 30s of the 20th century, it became clear that outer space is divided into regions - galaxies, which are huge formations, each with its own stellar population. Moreover, galaxies are not static objects. The speed of galaxies moving away from the imaginary center of the Universe is constantly changing, as evidenced by the convergence of some and the removal of others from each other.
All of the above processes, from the point of view of the duration of earthly life, last very slowly. From the point of view of science and these hypotheses, all evolutionary processes occur rapidly. Conventionally, the evolution of the Universe can be divided into four stages - eras:
- hadron era;
- lepton era;
- photon era;
- star era.
Cosmic time scale and evolution of the Universe, according to which the appearance of cosmic objects can be explained
At the first stage, all matter was concentrated in one large nuclear droplet, consisting of particles and antiparticles, combined into groups - hadrons (protons and neutrons). The ratio of particles to antiparticles is approximately 1:1.1. Next comes the process of annihilation of particles and antiparticles. The remaining protons and neutrons are the building blocks from which the Universe is formed. The duration of the hadron era is negligible, only 0.0001 seconds - the period of explosive reaction.
Then, after 100 seconds, the process of synthesis of elements begins. At a temperature of a billion degrees, the process of nuclear fusion produces molecules of hydrogen and helium. All this time, the substance continues to expand in space.
From this moment, a long, from 300 thousand to 700 thousand years, stage of recombination of nuclei and electrons begins, forming hydrogen and helium atoms. In this case, a decrease in the temperature of the substance is observed, and the radiation intensity decreases. The universe becomes transparent. Hydrogen and helium formed in colossal quantities under the influence of gravitational forces turns the primary Universe into a giant construction site. After millions of years, the stellar era begins - which is the process of formation of protostars and the first protogalaxies.
This division of evolution into stages fits into the hot Universe model, which explains many processes. The true causes of the Big Bang and the mechanism of matter expansion remain unexplained.
Structure and structure of the Universe
The stellar era of the evolution of the Universe begins with the formation of hydrogen gas. Under the influence of gravity, hydrogen accumulates into huge clusters and clumps. The mass and density of such clusters are colossal, hundreds of thousands of times greater than the mass of the formed galaxy itself. The uneven distribution of hydrogen, observed at the initial stage of the formation of the universe, explains the differences in the sizes of the resulting galaxies. Megagalaxies formed where the maximum accumulation of hydrogen gas should exist. Where the concentration of hydrogen was insignificant, smaller galaxies appeared, similar to our stellar home - the Milky Way.
The version according to which the Universe is a beginning-end point around which galaxies revolve at different stages of development
From this moment on, the Universe receives its first formations with clear boundaries and physical parameters. These are no longer nebulae, accumulations of stellar gas and cosmic dust (products of an explosion), protoclusters of stellar matter. These are star countries, the area of which is huge from the point of view of the human mind. The universe is becoming full of interesting cosmic phenomena.
From the point of view of scientific justification and the modern model of the Universe, galaxies were first formed as a result of the action of gravitational forces. There was a transformation of matter into a colossal universal whirlpool. Centripetal processes ensured the subsequent fragmentation of gas clouds into clusters, which became the birthplace of the first stars. Protogalaxies with fast rotation periods turned into spiral galaxies over time. Where the rotation was slow and the process of compression of matter was mainly observed, irregular galaxies were formed, most often elliptical. Against this background, more grandiose processes took place in the Universe - the formation of superclusters of galaxies, whose edges are in close contact with each other.
Superclusters are numerous groups of galaxies and clusters of galaxies within the large-scale structure of the Universe. Within 1 billion St. There are about 100 superclusters for years
From that moment on, it became clear that the Universe is a huge map, where the continents are clusters of galaxies, and the countries are megagalaxies and galaxies formed billions of years ago. Each of the formations consists of a cluster of stars, nebulae, and accumulations of interstellar gas and dust. However, this entire population constitutes only 1% of the total volume of universal formations. The bulk of the mass and volume of galaxies is occupied by dark matter, the nature of which is not possible to determine.
Diversity of the Universe: classes of galaxies
Thanks to the efforts of the American astrophysicist Edwin Hubble, we now have the boundaries of the Universe and a clear classification of the galaxies that inhabit it. The classification is based on the structural features of these giant formations. Why do galaxies have different shapes? The answer to this and many other questions is given by the Hubble classification, according to which the Universe consists of galaxies of the following classes:
- spiral;
- elliptical;
- irregular galaxies.
The first include the most common formations with which the universe is filled. The characteristic features of spiral galaxies are the presence of a clearly defined spiral that rotates around a bright core or tends to a galactic bar. Spiral galaxies with a core are designated S, while objects with a central bar are designated SB. Our Milky Way galaxy also belongs to this class, in the center of which the core is divided by a luminous bridge.
A typical spiral galaxy. In the center, a core with a bridge from the ends of which spiral arms emanate is clearly visible.
Similar formations are scattered throughout the Universe. The closest spiral galaxy, Andromeda, is a giant that is rapidly approaching the Milky Way. The largest representative of this class known to us is the giant galaxy NGC 6872. The diameter of the galactic disk of this monster is approximately 522 thousand light years. This object is located at a distance of 212 million light years from our galaxy.
The next common class of galactic formations are elliptical galaxies. Their designation in accordance with the Hubble classification is the letter E (elliptical). These formations are ellipsoidal in shape. Despite the fact that there are quite a lot of similar objects in the Universe, elliptical galaxies are not particularly expressive. They consist mainly of smooth ellipses that are filled with star clusters. Unlike galactic spirals, ellipses do not contain accumulations of interstellar gas and cosmic dust, which are the main optical effects of visualizing such objects.
A typical representative of this class known today is the elliptical ring nebula in the constellation Lyra. This object is located at a distance of 2100 light years from Earth.
View of the elliptical galaxy Centaurus A through the CFHT telescope
The last class of galactic objects that populate the Universe are irregular or irregular galaxies. The designation according to the Hubble classification is the Latin symbol I. The main feature is an irregular shape. In other words, such objects do not have clear symmetrical shapes and characteristic patterns. In its shape, such a galaxy resembles a picture of universal chaos, where star clusters alternate with clouds of gas and cosmic dust. On the scale of the Universe, irregular galaxies are a common phenomenon.
In turn, irregular galaxies are divided into two subtypes:
- Irregular galaxies of subtype I have a complex irregular structure, a high dense surface, and are distinguished by brightness. Often this chaotic shape of irregular galaxies is the result of collapsed spirals. A typical example of such a galaxy is the Large and Small Magellanic Cloud;
- Irregular, irregular galaxies of subtype II have a low surface, a chaotic shape and are not very bright. Due to the decrease in brightness, such formations are difficult to detect in the vastness of the Universe.
The Large Magellanic Cloud is the closest irregular galaxy to us. Both formations, in turn, are satellites of the Milky Way and may soon (in 1-2 billion years) be absorbed by a larger object.
Irregular galaxy Large Magellanic Cloud - a satellite of our Milky Way galaxy
Despite the fact that Edwin Hubble quite accurately classified galaxies into classes, this classification is not ideal. We could achieve more results if we included Einstein’s theory of relativity in the process of understanding the Universe. The Universe is represented by a wealth of various forms and structures, each of which has its own characteristic properties and features. Recently, astronomers were able to discover new galactic formations that are described as intermediate objects between spiral and elliptical galaxies.
The Milky Way is the most famous part of the Universe
Two spiral arms, symmetrically located around the center, make up the main body of the galaxy. The spirals, in turn, consist of arms that smoothly flow into each other. At the junction of the Sagittarius and Cygnus arms, our Sun is located, located at a distance of 2.62·10¹⁷km from the center of the Milky Way galaxy. The spirals and arms of spiral galaxies are clusters of stars whose density increases as they approach the galactic center. The rest of the mass and volume of galactic spirals is dark matter, and only a small part is accounted for by interstellar gas and cosmic dust.
The position of the Sun in the arms of the Milky Way, the place of our galaxy in the Universe
The thickness of the spirals is approximately 2 thousand light years. This entire layer cake is in constant motion, rotating at a tremendous speed of 200-300 km/s. The closer to the center of the galaxy, the higher the rotation speed. It will take the Sun and our Solar System 250 million years to complete a revolution around the center of the Milky Way.
Our galaxy consists of a trillion stars, large and small, super-heavy and medium-sized. The densest cluster of stars in the Milky Way is the Sagittarius Arm. It is in this region that the maximum brightness of our galaxy is observed. The opposite part of the galactic circle, on the contrary, is less bright and difficult to distinguish by visual observation.
The central part of the Milky Way is represented by a core, the dimensions of which are estimated to be 1000-2000 parsecs. In this brightest region of the galaxy, the maximum number of stars is concentrated, which have different classes, their own paths of development and evolution. These are mainly old super-heavy stars in the final stages of the Main Sequence. Confirmation of the presence of an aging center of the Milky Way galaxy is the presence in this region of a large number of neutron stars and black holes. Indeed, the center of the spiral disk of any spiral galaxy is a supermassive black hole, which, like a giant vacuum cleaner, sucks in celestial objects and real matter.
A supermassive black hole located in the central part of the Milky Way is the place of death of all galactic objects
As for star clusters, scientists today have managed to classify two types of clusters: spherical and open. In addition to star clusters, the spirals and arms of the Milky Way, like any other spiral galaxy, consist of scattered matter and dark energy. As a consequence of the Big Bang, matter is in a highly rarefied state, which is represented by tenuous interstellar gas and dust particles. The visible part of the matter consists of nebulae, which in turn are divided into two types: planetary and diffuse nebulae. The visible part of the spectrum of nebulae is due to the refraction of light from stars, which emit light inside the spiral in all directions.
Our solar system exists in this cosmic soup. No, we are not the only ones in this huge world. Like the Sun, many stars have their own planetary systems. The whole question is how to detect distant planets, if distances even within our galaxy exceed the duration of existence of any intelligent civilization. Time in the Universe is measured by other criteria. Planets with their satellites, the smallest objects in the Universe. The number of such objects is incalculable. Each of those stars that are in the visible range can have their own star systems. We can see only the existing planets closest to us. What is happening in the neighborhood, what worlds exist in other arms of the Milky Way and what planets exist in other galaxies remains a mystery.
Kepler-16 b is an exoplanet near the double star Kepler-16 in the constellation Cygnus
Conclusion
Having only a superficial understanding of how the Universe appeared and how it is evolving, man has taken only a small step towards comprehending and comprehending the scale of the universe. The enormous size and scope that scientists have to deal with today suggests that human civilization is just a moment in this bundle of matter, space and time.
Model of the Universe in accordance with the concept of the presence of matter in space, taking into account time
The study of the Universe goes from Copernicus to the present day. At first, scientists started from the heliocentric model. In fact, it turned out that space has no real center and all rotation, movement and movement occurs according to the laws of the Universe. Despite the fact that there is a scientific explanation for the processes taking place, universal objects are divided into classes, types and types, not a single body in space is similar to another. The sizes of celestial bodies are approximate, as is their mass. The location of galaxies, stars and planets is arbitrary. The thing is that there is no coordinate system in the Universe. Observing space, we make a projection onto the entire visible horizon, considering our Earth as the zero reference point. In fact, we are only a microscopic particle, lost in the endless expanses of the Universe.
The Universe is a substance in which all objects exist in close connection with space and time
Similar to the connection to size, time in the Universe should be considered as the main component. The origin and age of space objects allows us to create a picture of the birth of the world and highlight the stages of the evolution of the universe. The system we are dealing with is closely bound by time. All processes occurring in space have cycles - beginning, formation, transformation and ending, accompanied by the death of a material object and the transition of matter to another state.
Looking at the starry sky at night, you involuntarily ask yourself: how many stars are there in the sky? Is there still life somewhere, how did it all come about, and is there an end to it all?
Most astronomers are confident that the Universe was born as a result of a powerful explosion, about 15 billion years ago. This huge explosion, usually called the “Big Bang” or “Big Impact”, was formed from a strong compression of matter, dispersed hot gases in different directions, and gave rise to galaxies, stars and planets. Even the most modern and new astronomical devices are not able to cover the entire space. But modern technology can catch light from stars that are 15 billion light years away from Earth! Perhaps these stars are long gone, they were born, grew old and died, but the light from them traveled to Earth for 15 billion years and the telescope still sees it.
Scientists of many generations and countries are trying to guess, calculate the size of our Universe, and determine its center. Previously, it was believed that the center of the Universe was our planet Earth. Copernicus proved that this is the Sun, but with the development of knowledge and the discovery of our Milky Way galaxy, it became clear that neither our planet nor even the Sun are the center of the Universe. For a long time they thought that there were no other galaxies besides the Milky Way, but this was also denied.
A well-known scientific fact says that the Universe is constantly expanding and the starry sky that we observe, the structure of the planets that we see now, is completely different than millions of years ago. If the Universe is growing, that means there are edges. Another theory says that beyond the boundaries of our space there are other Universes and worlds.
The first who decided to prove the infinity of the Universe was Isaac Newton. Having discovered the law of universal gravitation, he believed that if space were finite, all its bodies would sooner or later attract and merge into a single whole. And since this does not happen, it means that the Universe has no boundaries.
It would seem that all this is logical and obvious, but still Albert Einstein was able to break these stereotypes. He created his model of the Universe based on his theory of relativity, according to which the Universe is infinite in time, but finite in space. He compared it to a three-dimensional sphere or, in simple terms, to our globe. No matter how much a traveler travels across the Earth, he will never reach its edge. However, this does not mean that the Earth is infinite. The traveler will simply return to the place from which he began his journey.
In the same way, a space wanderer, starting from our planet and crossing the Universe on a starship, can return back to Earth. Only this time the wanderer will move not along the two-dimensional surface of a sphere, but along the three-dimensional surface of a hypersphere. This means that the Universe has a finite volume, and therefore a finite number of stars and mass. However, the Universe has neither boundaries nor any center. Einstein believed that the Universe is static and its size never changes.
However, the greatest minds are not above delusions. In 1927, our Soviet physicist Alexander Friedman significantly expanded this model. According to his calculations, the Universe is not static at all. It can expand or contract over time. Einstein did not immediately accept this amendment, but with the discovery of the Hubble telescope, the fact of the expansion of the Universe was proven, because galaxies scattered, i.e. were moving away from each other.
It has now been proven that the Universe is expanding at an accelerating rate, that it is filled with cold dark matter and its age is 13.75 billion years. Knowing the age of the Universe, we can determine the size of its observable region. But don’t forget about constant expansion.
So, the size of the observable Universe is divided into two types. The apparent size, also called the Hubble radius (13.75 billion light years), which we discussed above. And the real size, called the particle horizon (45.7 billion light years). Now I’ll explain: you’ve probably heard that when we look at the sky, we see the past of other stars and planets, and not what is happening now. For example, looking at the Moon, we see as it was a little more than a second ago, the Sun - more than eight minutes ago, the nearest stars - years, galaxies - millions of years ago, etc. That is, since the birth of the Universe, no photon, i.e. light would not have time to travel more than 13.75 billion light years. But! We should not forget about the fact of the expansion of the Universe. So, by the time it reaches the observer, the object of the nascent Universe that emitted this light will already be 45.7 billion light years away from us. years. This size is the horizon of particles, it is the boundary of the observable Universe.
However, both of these horizons do not at all characterize the real size of the Universe. It is expanding and if this trend continues, then all those objects that we can now observe will sooner or later disappear from our field of vision.
Currently, the most distant light observed by astronomers is the cosmic microwave background radiation. These are ancient electromagnetic waves that arose at the birth of the Universe. These waves are detected using highly sensitive antennas and directly in space. By peering into the cosmic microwave background radiation, scientists see the Universe as it was 380 thousand years after the Big Bang. At this moment, the Universe cooled down enough that it was able to emit free photons, which are detected today with the help of radio telescopes. At that time, there were no stars or galaxies in the Universe, but only a continuous cloud of hydrogen, helium and an insignificant amount of other elements. From the inhomogeneities observed in this cloud, galaxy clusters will subsequently form.
Scientists are still debating whether there are true, unobservable boundaries of the Universe. One way or another, everyone agrees on the infinity of the Universe, but interprets this infinity in completely different ways. Some consider the Universe to be multidimensional, where our “local” three-dimensional Universe is only one of its layers. Others say that the Universe is fractal - which means that our local Universe may be a particle of another. We should not forget about the various models of the Multiverse, i.e. the existence of an infinite number of other universes beyond ours. And there are many, many different versions, the number of which is limited only by human imagination.
Did you know that the Universe we observe has fairly definite boundaries? We are used to associating the Universe with something infinite and incomprehensible. However, modern science, when asked about the “infinity” of the Universe, offers a completely different answer to such an “obvious” question.
According to modern ideas, the size of the observable Universe is approximately 45.7 billion light years (or 14.6 gigaparsecs). But what do these numbers mean?
The first question that comes to the mind of an ordinary person is how can the Universe not be infinite? It would seem that it is indisputable that the container of all that exists around us should have no boundaries. If these boundaries exist, what exactly are they?
Let's say some astronaut reaches the boundaries of the Universe. What will he see in front of him? A solid wall? Fire barrier? And what is behind it - emptiness? Another Universe? But can emptiness or another Universe mean that we are on the border of the universe? After all, this does not mean that there is “nothing” there. Emptiness and another Universe are also “something”. But the Universe is something that contains absolutely everything “something”.
We arrive at an absolute contradiction. It turns out that the boundary of the Universe must hide from us something that should not exist. Or the boundary of the Universe should fence off “everything” from “something”, but this “something” should also be part of “everything”. In general, complete absurdity. Then how can scientists declare the limiting size, mass and even age of our Universe? These values, although unimaginably large, are still finite. Does science argue with the obvious? To understand this, let's first trace how people came to our modern understanding of the Universe.
Expanding the boundaries
Since time immemorial, people have been interested in what the world around them is like. There is no need to give examples of the three pillars and other attempts of the ancients to explain the universe. As a rule, in the end it all came down to the fact that the basis of all things is the earth's surface. Even in the times of antiquity and the Middle Ages, when astronomers had extensive knowledge of the laws of planetary movement along the “fixed” celestial sphere, the Earth remained the center of the Universe.
Naturally, even in Ancient Greece there were those who believed that the Earth revolves around the Sun. There were those who spoke about the many worlds and the infinity of the Universe. But constructive justifications for these theories arose only at the turn of the scientific revolution.
In the 16th century, Polish astronomer Nicolaus Copernicus made the first major breakthrough in knowledge of the Universe. He firmly proved that the Earth is only one of the planets revolving around the Sun. Such a system greatly simplified the explanation of such a complex and intricate movement of planets in the celestial sphere. In the case of a stationary Earth, astronomers had to come up with all sorts of clever theories to explain this behavior of the planets. On the other hand, if the Earth is accepted as moving, then an explanation for such intricate movements comes naturally. Thus, a new paradigm called “heliocentrism” took hold in astronomy.
Many Suns
However, even after this, astronomers continued to limit the Universe to the “sphere of fixed stars.” Until the 19th century, they were unable to estimate the distance to the stars. For several centuries, astronomers have tried to no avail to detect deviations in the position of stars relative to the Earth’s orbital movement (annual parallaxes). The instruments of those times did not allow such precise measurements.
Finally, in 1837, the Russian-German astronomer Vasily Struve measured parallax. This marked a new step in understanding the scale of space. Now scientists could safely say that the stars are distant similarities to the Sun. And our luminary is no longer the center of everything, but an equal “resident” of an endless star cluster.
Astronomers have come even closer to understanding the scale of the Universe, because the distances to the stars turned out to be truly monstrous. Even the size of the planets’ orbits seemed insignificant in comparison. Next it was necessary to understand how the stars are concentrated in .
Many Milky Ways
The famous philosopher Immanuel Kant anticipated the foundations of the modern understanding of the large-scale structure of the Universe back in 1755. He hypothesized that the Milky Way is a huge rotating star cluster. In turn, many of the observed nebulae are also more distant “milky ways” - galaxies. Despite this, until the 20th century, astronomers believed that all nebulae are sources of star formation and are part of the Milky Way.
The situation changed when astronomers learned to measure distances between galaxies using . The absolute luminosity of stars of this type strictly depends on the period of their variability. By comparing their absolute luminosity with the visible one, it is possible to determine the distance to them with high accuracy. This method was developed in the early 20th century by Einar Hertzschrung and Harlow Scelpi. Thanks to him, the Soviet astronomer Ernst Epic in 1922 determined the distance to Andromeda, which turned out to be an order of magnitude larger than the size of the Milky Way.
Edwin Hubble continued Epic's initiative. By measuring the brightness of Cepheids in other galaxies, he measured their distance and compared it with the redshift in their spectra. So in 1929 he developed his famous law. His work definitively disproved the established view that the Milky Way is the edge of the Universe. Now it was one of many galaxies that had once been considered part of it. Kant's hypothesis was confirmed almost two centuries after its development.
Subsequently, the connection discovered by Hubble between the distance of a galaxy from an observer relative to the speed of its removal from him, made it possible to draw a complete picture of the large-scale structure of the Universe. It turned out that the galaxies were only an insignificant part of it. They connected into clusters, clusters into superclusters. In turn, superclusters form the largest known structures in the Universe—threads and walls. These structures, adjacent to huge supervoids (), constitute the large-scale structure of the currently known Universe.
Apparent infinity
It follows from the above that in just a few centuries, science has gradually fluttered from geocentrism to a modern understanding of the Universe. However, this does not answer why we limit the Universe today. After all, until now we were talking only about the scale of space, and not about its very nature.
The first who decided to justify the infinity of the Universe was Isaac Newton. Having discovered the law of universal gravitation, he believed that if space were finite, all its bodies would sooner or later merge into a single whole. Before him, if anyone expressed the idea of the infinity of the Universe, it was exclusively in a philosophical vein. Without any scientific basis. An example of this is Giordano Bruno. By the way, like Kant, he was many centuries ahead of science. He was the first to declare that stars are distant suns, and planets also revolve around them.
It would seem that the very fact of infinity is quite justified and obvious, but the turning points of science of the 20th century shook this “truth”.
Stationary Universe
The first significant step towards developing a modern model of the Universe was taken by Albert Einstein. The famous physicist introduced his model of a stationary Universe in 1917. This model was based on the general theory of relativity, which he had developed a year earlier. According to his model, the Universe is infinite in time and finite in space. But, as noted earlier, according to Newton, a Universe with a finite size must collapse. To do this, Einstein introduced a cosmological constant, which compensated for the gravitational attraction of distant objects.
No matter how paradoxical it may sound, Einstein did not limit the very finitude of the Universe. In his opinion, the Universe is a closed shell of a hypersphere. An analogy is the surface of an ordinary three-dimensional sphere, for example, a globe or the Earth. No matter how much a traveler travels across the Earth, he will never reach its edge. However, this does not mean that the Earth is infinite. The traveler will simply return to the place from which he began his journey.
On the surface of the hypersphere
In the same way, a space wanderer, traversing Einstein’s Universe on a starship, can return back to Earth. Only this time the wanderer will move not along the two-dimensional surface of a sphere, but along the three-dimensional surface of a hypersphere. This means that the Universe has a finite volume, and therefore a finite number of stars and mass. However, the Universe has neither boundaries nor any center.
Einstein came to these conclusions by connecting space, time and gravity in his famous theory. Before him, these concepts were considered separate, which is why the space of the Universe was purely Euclidean. Einstein proved that gravity itself is a curvature of space-time. This radically changed early ideas about the nature of the Universe, based on classical Newtonian mechanics and Euclidean geometry.
Expanding Universe
Even the discoverer of the “new Universe” himself was not a stranger to delusions. Although Einstein limited the Universe in space, he continued to consider it static. According to his model, the Universe was and remains eternal, and its size always remains the same. In 1922, Soviet physicist Alexander Friedman significantly expanded this model. According to his calculations, the Universe is not static at all. It can expand or contract over time. It is noteworthy that Friedman came to such a model based on the same theory of relativity. He managed to apply this theory more correctly, bypassing the cosmological constant.
Albert Einstein did not immediately accept this “amendment.” This new model came to the aid of the previously mentioned Hubble discovery. The recession of galaxies indisputably proved the fact of the expansion of the Universe. So Einstein had to admit his mistake. Now the Universe had a certain age, which strictly depends on the Hubble constant, which characterizes the rate of its expansion.
Further development of cosmology
As scientists tried to solve this question, many other important components of the Universe were discovered and various models of it were developed. So in 1948, George Gamow introduced the “hot Universe” hypothesis, which would later turn into the big bang theory. The discovery in 1965 confirmed his suspicions. Now astronomers could observe the light that came from the moment when the Universe became transparent.
Dark matter, predicted in 1932 by Fritz Zwicky, was confirmed in 1975. Dark matter actually explains the very existence of galaxies, galaxy clusters and the Universal structure itself as a whole. This is how scientists learned that most of the mass of the Universe is completely invisible.
Finally, in 1998, during a study of the distance to, it was discovered that the Universe is expanding at an accelerating rate. This latest turning point in science gave birth to our modern understanding of the nature of the universe. The cosmological coefficient, introduced by Einstein and refuted by Friedman, again found its place in the model of the Universe. The presence of a cosmological coefficient (cosmological constant) explains its accelerated expansion. To explain the presence of a cosmological constant, the concept of a hypothetical field containing most of the mass of the Universe was introduced.
Modern understanding of the size of the observable Universe
The modern model of the Universe is also called the ΛCDM model. The letter "Λ" means the presence of a cosmological constant, which explains the accelerated expansion of the Universe. "CDM" means that the Universe is filled with cold dark matter. Recent studies indicate that the Hubble constant is about 71 (km/s)/Mpc, which corresponds to the age of the Universe 13.75 billion years. Knowing the age of the Universe, we can estimate the size of its observable region.
According to the theory of relativity, information about any object cannot reach an observer at a speed greater than the speed of light (299,792,458 m/s). It turns out that the observer sees not just an object, but its past. The farther an object is from him, the more distant the past he looks. For example, looking at the Moon, we see as it was a little more than a second ago, the Sun - more than eight minutes ago, the nearest stars - years, galaxies - millions of years ago, etc. In Einstein’s stationary model, the Universe has no age limit, which means its observable region is also not limited by anything. The observer, armed with increasingly sophisticated astronomical instruments, will observe increasingly distant and ancient objects.
We have a different picture with the modern model of the Universe. According to it, the Universe has an age, and therefore a limit of observation. That is, since the birth of the Universe, no photon could have traveled a distance greater than 13.75 billion light years. It turns out that we can say that the observable Universe is limited from the observer to a spherical region with a radius of 13.75 billion light years. However, this is not quite true. We should not forget about the expansion of the space of the Universe. By the time the photon reaches the observer, the object that emitted it will be already 45.7 billion light years away from us. years. This size is the horizon of particles, it is the boundary of the observable Universe.
Over the horizon
So, the size of the observable Universe is divided into two types. Apparent size, also called the Hubble radius (13.75 billion light years). And the real size, called the particle horizon (45.7 billion light years). The important thing is that both of these horizons do not at all characterize the real size of the Universe. Firstly, they depend on the position of the observer in space. Secondly, they change over time. In the case of the ΛCDM model, the particle horizon expands at a speed greater than the Hubble horizon. Modern science does not answer the question of whether this trend will change in the future. But if we assume that the Universe continues to expand with acceleration, then all those objects that we see now will sooner or later disappear from our “field of vision”.
Currently, the most distant light observed by astronomers is the cosmic microwave background radiation. Peering into it, scientists see the Universe as it was 380 thousand years after the Big Bang. At this moment, the Universe cooled down enough that it was able to emit free photons, which are detected today with the help of radio telescopes. At that time, there were no stars or galaxies in the Universe, but only a continuous cloud of hydrogen, helium and an insignificant amount of other elements. From the inhomogeneities observed in this cloud, galaxy clusters will subsequently form. It turns out that precisely those objects that will be formed from inhomogeneities in the cosmic microwave background radiation are located closest to the particle horizon.
True Boundaries
Whether the Universe has true, unobservable boundaries is still a matter of pseudoscientific speculation. One way or another, everyone agrees on the infinity of the Universe, but interprets this infinity in completely different ways. Some consider the Universe to be multidimensional, where our “local” three-dimensional Universe is only one of its layers. Others say that the Universe is fractal - which means that our local Universe may be a particle of another. We should not forget about the various models of the Multiverse with its closed, open, parallel Universes, and wormholes. And there are many, many different versions, the number of which is limited only by human imagination.
But if we turn on cold realism or simply step back from all these hypotheses, then we can assume that our Universe is an infinite homogeneous container of all stars and galaxies. Moreover, at any very distant point, be it billions of gigaparsecs from us, all the conditions will be exactly the same. At this point, the particle horizon and the Hubble sphere will be exactly the same, with the same relict radiation at their edge. There will be the same stars and galaxies around. Interestingly, this does not contradict the expansion of the Universe. After all, it is not just the Universe that is expanding, but its space itself. The fact that at the moment of the Big Bang the Universe arose from one point only means that the infinitely small (practically zero) dimensions that were then have now turned into unimaginably large ones. In the future, we will use precisely this hypothesis in order to clearly understand the scale of the observable Universe.
Visual representation
Various sources provide all sorts of visual models that allow people to understand the scale of the Universe. However, it is not enough for us to realize how big the cosmos is. It is important to imagine how concepts such as the Hubble horizon and the particle horizon actually manifest themselves. To do this, let's imagine our model step by step.
Let's forget that modern science does not know about the “foreign” region of the Universe. Discarding versions of multiverses, the fractal Universe and its other “varieties”, let’s imagine that it is simply infinite. As noted earlier, this does not contradict the expansion of its space. Of course, let's take into account that its Hubble sphere and particle sphere are respectively 13.75 and 45.7 billion light years.
Scale of the Universe
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First, let's try to understand how large the Universal scale is. If you have traveled around our planet, you can well imagine how big the Earth is for us. Now imagine our planet as a grain of buckwheat moving in orbit around a watermelon-Sun the size of half a football field. In this case, Neptune’s orbit will correspond to the size of a small city, the area will correspond to the Moon, and the area of the boundary of the influence of the Sun will correspond to Mars. It turns out that our Solar System is as much larger than the Earth as Mars is larger than buckwheat! But this is just the beginning.
Now let’s imagine that this buckwheat will be our system, the size of which is approximately equal to one parsec. Then the Milky Way will be the size of two football stadiums. However, this will not be enough for us. The Milky Way will also have to be reduced to centimeter size. It will somewhat resemble coffee foam wrapped in a whirlpool in the middle of coffee-black intergalactic space. Twenty centimeters from it there is the same spiral “crumb” - the Andromeda Nebula. Around them there will be a swarm of small galaxies of our Local Cluster. The apparent size of our Universe will be 9.2 kilometers. We have come to an understanding of the Universal dimensions.
Inside the universal bubble
However, it is not enough for us to understand the scale itself. It is important to realize the Universe in dynamics. Let's imagine ourselves as giants, for whom the Milky Way has a centimeter diameter. As noted just now, we will find ourselves inside a ball with a radius of 4.57 and a diameter of 9.24 kilometers. Let’s imagine that we are able to float inside this ball, travel, covering entire megaparsecs in a second. What will we see if our Universe is infinite?
Of course, countless galaxies of all kinds will appear before us. Elliptical, spiral, irregular. Some areas will be teeming with them, others will be empty. The main feature will be that visually they will all be motionless while we are motionless. But as soon as we take a step, the galaxies themselves will begin to move. For example, if we are able to discern a microscopic Solar System in the centimeter-long Milky Way, we will be able to observe its development. Moving 600 meters away from our galaxy, we will see the protostar Sun and the protoplanetary disk at the moment of formation. Approaching it, we will see how the Earth appears, life arises and man appears. In the same way, we will see how galaxies change and move as we move away from or approach them.
Consequently, the more distant galaxies we look at, the more ancient they will be for us. So the most distant galaxies will be located further than 1300 meters from us, and at the turn of 1380 meters we will already see relict radiation. True, this distance will be imaginary for us. However, as we get closer to the cosmic microwave background radiation, we will see an interesting picture. Naturally, we will observe how galaxies will form and develop from the initial cloud of hydrogen. When we reach one of these formed galaxies, we will understand that we have covered not 1.375 kilometers at all, but all 4.57.
Zooming out
As a result, we will increase in size even more. Now we can place entire voids and walls in the fist. So we will find ourselves in a rather small bubble from which it is impossible to get out. Not only will the distance to objects at the edge of the bubble increase as they get closer, but the edge itself will shift indefinitely. This is the whole point of the size of the observable Universe.
No matter how big the Universe is, for an observer it will always remain a limited bubble. The observer will always be at the center of this bubble, in fact he is its center. Trying to get to any object at the edge of the bubble, the observer will shift its center. As you approach an object, this object will move further and further from the edge of the bubble and at the same time change. For example, from a shapeless hydrogen cloud it will turn into a full-fledged galaxy or, further, a galactic cluster. In addition, the path to this object will increase as you approach it, since the surrounding space itself will change. Having reached this object, we will only move it from the edge of the bubble to its center. At the edge of the Universe, relict radiation will still flicker.
If we assume that the Universe will continue to expand at an accelerated rate, then being in the center of the bubble and moving time forward by billions, trillions and even higher orders of years, we will notice an even more interesting picture. Although our bubble will also increase in size, its changing components will move away from us even faster, leaving the edge of this bubble, until each particle of the Universe wanders separately in its lonely bubble without the opportunity to interact with other particles.
So, modern science does not have information about the real size of the Universe and whether it has boundaries. But we know for sure that the observable Universe has a visible and true boundary, called respectively the Hubble radius (13.75 billion light years) and the particle radius (45.7 billion light years). These boundaries depend entirely on the observer's position in space and expand over time. If the Hubble radius expands strictly at the speed of light, then the expansion of the particle horizon is accelerated. The question of whether its acceleration of the particle horizon will continue further and whether it will be replaced by compression remains open.
The portal site is an information resource where you can get a lot of useful and interesting knowledge related to Space. First of all, we will talk about our and other Universes, about celestial bodies, black holes and phenomena in the depths of outer space.
The totality of everything that exists, matter, individual particles and the space between these particles is called the Universe. According to scientists and astrologers, the age of the Universe is approximately 14 billion years. The size of the visible part of the Universe occupies about 14 billion light years. And some claim that the Universe extends over 90 billion light years. For greater convenience, it is customary to use the parsec value in calculating such distances. One parsec is equal to 3.2616 light years, that is, a parsec is the distance over which the average radius of the Earth's orbit is viewed at an angle of one arcsecond.
Armed with these indicators, you can calculate the cosmic distance from one object to another. For example, the distance from our planet to the Moon is 300,000 km, or 1 light second. Consequently, this distance to the Sun increases to 8.31 light minutes.
Throughout history, people have tried to solve mysteries related to Space and the Universe. In the articles on the portal site you can learn not only about the Universe, but also about modern scientific approaches to its study. All material is based on the most advanced theories and facts.
It should be noted that the Universe includes a large number of different objects known to people. The most widely known among them are planets, stars, satellites, black holes, asteroids and comets. At the moment, most of all is understood about the planets, since we live on one of them. Some planets have their own satellites. So, the Earth has its own satellite - the Moon. Besides our planet, there are 8 more that revolve around the Sun.
There are many stars in Space, but each of them is different from each other. They have different temperatures, sizes and brightness. Since all stars are different, they are classified as follows:
White dwarfs;
Giants;
Supergiants;
Neutron stars;
Quasars;
Pulsars.
The densest substance we know is lead. In some planets, the density of their substance can be thousands of times higher than the density of lead, which raises many questions for scientists.
All planets revolve around the Sun, but it also does not stand still. Stars can gather into clusters, which, in turn, also revolve around a center still unknown to us. These clusters are called galaxies. Our galaxy is called the Milky Way. All studies conducted so far indicate that most of the matter that galaxies create is so far invisible to humans. Because of this, it was called dark matter.
The centers of galaxies are considered the most interesting. Some astronomers believe that the possible center of the galaxy is a black hole. This is a unique phenomenon formed as a result of the evolution of a star. But for now, these are all just theories. Conducting experiments or studying such phenomena is not yet possible.
In addition to galaxies, the Universe contains nebulae (interstellar clouds consisting of gas, dust and plasma), cosmic microwave background radiation that permeates the entire space of the Universe, and many other little-known and even completely unknown objects.
Circulation of the ether of the Universe
Symmetry and balance of material phenomena is the main principle of structural organization and interaction in nature. Moreover, in all forms: stellar plasma and matter, world and released ethers. The whole essence of such phenomena lies in their interactions and transformations, most of which are represented by the invisible ether. It is also called relict radiation. This is microwave cosmic background radiation with a temperature of 2.7 K. There is an opinion that it is this vibrating ether that is the fundamental basis for everything filling the Universe. The anisotropy of the distribution of ether is associated with the directions and intensity of its movement in different areas of invisible and visible space. The whole difficulty of studying and research is quite comparable with the difficulties of studying turbulent processes in gases, plasmas and liquids of matter.
Why do many scientists believe that the Universe is multidimensional?
After conducting experiments in laboratories and in Space itself, data was obtained from which it can be assumed that we live in a Universe in which the location of any object can be characterized by time and three spatial coordinates. Because of this, the assumption arises that the Universe is four-dimensional. However, some scientists, developing theories of elementary particles and quantum gravity, may come to the conclusion that the existence of a large number of dimensions is simply necessary. Some models of the Universe do not exclude as many as 11 dimensions.
It should be taken into account that the existence of a multidimensional Universe is possible with high-energy phenomena - black holes, the big bang, bursters. At least, this is one of the ideas of leading cosmologists.
The expanding Universe model is based on the general theory of relativity. It was proposed to adequately explain the redshift structure. The expansion began at the same time as the Big Bang. Its condition is illustrated by the surface of an inflated rubber ball, on which dots - extragalactic objects - were applied. When such a ball is inflated, all its points move away from each other, regardless of position. According to the theory, the Universe can either expand indefinitely or contract.
Baryonic asymmetry of the Universe
The significant increase in the number of elementary particles over the entire number of antiparticles observed in the Universe is called baryon asymmetry. Baryons include neutrons, protons and some other short-lived elementary particles. This disproportion occurred during the era of annihilation, namely three seconds after the Big Bang. Up to this point, the number of baryons and antibaryons corresponded to each other. During the mass annihilation of elementary antiparticles and particles, most of them combined into pairs and disappeared, thereby generating electromagnetic radiation.
Age of the Universe on the portal website
Modern scientists believe that our Universe is approximately 16 billion years old. According to estimates, the minimum age may be 12-15 billion years. The minimum is repelled by the oldest stars in our Galaxy. Its real age can only be determined using Hubble's law, but real does not mean accurate.
Visibility horizon
A sphere with a radius equal to the distance that light travels during the entire existence of the Universe is called its visibility horizon. The existence of a horizon is directly proportional to the expansion and contraction of the Universe. According to Friedman's cosmological model, the Universe began to expand from a singular distance approximately 15-20 billion years ago. During all the time, light travels a residual distance in the expanding Universe, namely 109 light years. Because of this, each observer at moment t0 after the start of the expansion process can observe only a small part, limited by a sphere, which at that moment has radius I. Those bodies and objects that are at this moment beyond this boundary are, in principle, not observable. The light reflected from them simply does not have time to reach the observer. This is not possible even if the light came out when the expansion process began.
Due to absorption and scattering in the early Universe, given the high density, photons could not propagate in a free direction. Therefore, the observer is able to detect only that radiation that appeared in the era of the Universe transparent to radiation. This epoch is determined by the time t»300,000 years, the density of the substance r»10-20 g/cm3 and the moment of hydrogen recombination. From all of the above it follows that the closer the source is in the galaxy, the greater the redshift value for it will be.
Big Bang
The moment the Universe began is called the Big Bang. This concept is based on the fact that initially there was a point (singularity point) at which all energy and all matter were present. The basis of the characteristic is considered to be the high density of matter. What happened before this singularity is unknown.
There is no exact information regarding the events and conditions that occurred at the time of 5*10-44 seconds (the moment of the end of the 1st time quantum). In physical terms of that era, one can only assume that then the temperature was approximately 1.3 * 1032 degrees with a matter density of approximately 1096 kg/m 3. These values are the limits for the application of existing ideas. They appear due to the relationship between the gravitational constant, the speed of light, the Boltzmann and Planck constants and are called “Planck constants”.
Those events that are associated with 5*10-44 to 10-36 seconds reflect the model of the “inflationary Universe”. The moment of 10-36 seconds is referred to as the “hot Universe” model.
In the period from 1-3 to 100-120 seconds, helium nuclei and a small number of nuclei of other light chemical elements were formed. From this moment on, a ratio began to be established in the gas: hydrogen 78%, helium 22%. Before one million years, the temperature in the Universe began to drop to 3000-45000 K, and the era of recombination began. Previously free electrons began to combine with light protons and atomic nuclei. Atoms of helium, hydrogen and a small number of lithium atoms began to appear. The substance became transparent, and the radiation, which is still observed today, was disconnected from it.
The next billion years of the existence of the Universe was marked by a decrease in temperature from 3000-45000 K to 300 K. Scientists called this period for the Universe the “Dark Age” due to the fact that no sources of electromagnetic radiation had yet appeared. During the same period, the heterogeneity of the mixture of initial gases became denser due to the influence of gravitational forces. Having simulated these processes on a computer, astronomers saw that this irreversibly led to the appearance of giant stars that exceeded the mass of the Sun by millions of times. Because they were so massive, these stars heated to incredibly high temperatures and evolved over tens of millions of years before exploding as supernovae. Heating to high temperatures, the surfaces of such stars created strong streams of ultraviolet radiation. Thus, a period of reionization began. The plasma that was formed as a result of such phenomena began to strongly scatter electromagnetic radiation in its spectral short-wave ranges. In a sense, the Universe began to plunge into a thick fog.
These huge stars became the first sources in the Universe of chemical elements that are much heavier than lithium. Space objects of the 2nd generation began to form, which contained the nuclei of these atoms. These stars began to be created from mixtures of heavy atoms. A repeated type of recombination of most of the atoms of intergalactic and interstellar gases occurred, which, in turn, led to a new transparency of space for electromagnetic radiation. The Universe has become exactly what we can observe now.
Observable structure of the Universe on the website portal
The observed part is spatially inhomogeneous. Most galaxy clusters and individual galaxies form its cellular or honeycomb structure. They construct cell walls that are a couple of megaparsecs thick. These cells are called "voids". They are characterized by a large size, tens of megaparsecs, and at the same time they do not contain substance with electromagnetic radiation. The void accounts for about 50% of the total volume of the Universe.
Doctor of Pedagogical Sciences E. LEVITAN, full member of the Russian Academy of Natural Sciences
Science and life // Illustrations
One of the best modern astrophysical observatories is the European Southern Observatory (Chile). In the photo: a unique instrument of this observatory - the New Technologies Telescope (NTT).
Photo of the reverse side of the 3.6-meter main mirror of the New Technologies Telescope.
Spiral galaxy NGC 1232 in the constellation Eridanus (distance to it is about 100 million light years). Size - 200 light years.
Before you is a huge gas disk, perhaps heated to hundreds of millions of degrees Kelvin (its diameter is about 300 light years).
It would seem a strange question. Of course, we see the Milky Way and other stars of the Universe that are closer to us. But the question posed in the title of the article is actually not so simple, and therefore we will try to figure it out.
The bright Sun during the day, the Moon and the scattering of stars in the night sky have always attracted human attention. Judging by the rock paintings, in which the most ancient painters depicted the figures of the most noticeable constellations, even then people, at least the most inquisitive of them, peered into the mysterious beauty of the starry sky. And of course they showed interest in the rising and setting of the Sun, in the mysterious changes in the appearance of the Moon... This is probably how “primitive contemplative” astronomy was born. This happened many thousands of years earlier than writing arose, the monuments of which have already become for us documents testifying to the origin and development of astronomy.
At first, the heavenly bodies, perhaps, were only an object of curiosity, then - deification, and, finally, began to help people, acting as a compass, calendar, clock. A serious reason for philosophizing about the possible structure of the Universe could be the discovery of “wandering luminaries” (planets). Attempts to unravel the incomprehensible loops that describe the planets against the background of supposedly fixed stars led to the construction of the first astronomical pictures or models of the world. The geocentric system of the world of Claudius Ptolemy (2nd century AD) is rightfully considered their apotheosis. Ancient astronomers tried (mostly unsuccessfully) to determine (but not yet prove!) what place the Earth occupied in relation to the seven then known planets (these were considered the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn). And only Nicolaus Copernicus (1473-1543) finally succeeded.
Ptolemy is called the creator of the geocentric, and Copernicus - the heliocentric system of the world. But fundamentally, these systems differed only in the ideas they contained about the location of the Sun and Earth in relation to the true planets (Mercury, Venus, Mars, Jupiter, Saturn) and to the Moon.
Copernicus essentially discovered the Earth as a planet, the Moon took its rightful place as a satellite of the Earth, and the Sun turned out to be the center of revolution of all planets. The sun and six planets moving around it (including the Earth) - this was the solar system as it was imagined in the 16th century.
The system, as we now know, is far from complete. Indeed, in addition to the six planets known to Copernicus, it also includes Uranus, Neptune, and Pluto. The latter was discovered in 1930 and turned out to be not only the most distant, but also the smallest planet. In addition, the Solar System includes about a hundred satellites of planets, two asteroid belts (one between the orbits of Mars and Jupiter, the other, recently discovered, the Kuiper belt, in the region of the orbits of Neptune and Pluto) and many comets with different orbital periods. The hypothetical “Cloud of comets” (something like their sphere of habitation) is, according to various estimates, at a distance of about 100-150 thousand astronomical units from the Sun. The boundaries of the solar system have accordingly expanded many times over.
At the beginning of 2002, American scientists “talked” with their automatic interplanetary station Pioneer 10, which was launched 30 years ago and managed to fly away from the Sun to a distance of 12 billion kilometers. The response to the radio signal sent from Earth arrived in 22 hours 06 minutes (at a speed of radio waves of about 300,000 km/sec). Taking into account what has been said, Pioneer 10 will have to fly for a long time to the “borders” of the Solar system (of course, quite conditional!). And then he will fly to the closest star on his path, Aldebaran (the brightest star in the constellation Taurus). "Pioneer 10" may arrive there and deliver the messages of earthlings embedded in it only in 2 million years...
We are separated from Aldebaran by at least 70 light years. And the distance to the closest star to us (in the a Centauri system) is only 4.75 light years. Today, even schoolchildren should know what a “light year”, “parsec” or “megaparsec” is. These are already questions and terms of stellar astronomy, which simply did not exist not only in the time of Copernicus, but also much later.
It was assumed that the stars were distant bodies, but their nature was unknown. True, Giordano Bruno, developing the ideas of Copernicus, brilliantly suggested that the stars are distant suns, and, perhaps, with their own planetary systems. The correctness of the first part of this hypothesis became completely obvious only in the 19th century. And the first dozens of planets around other stars were discovered only in the very last years of the recently ended 20th century. Before the birth of astrophysics and before the application of spectral analysis in astronomy, it was simply impossible to get closer to the scientific solution to the nature of stars. So it turned out that the stars played almost no role in the previous systems of the world. The starry sky was a kind of stage on which the planets “performed,” and they did not think much about the nature of the stars themselves (sometimes they were referred to as ... “silver nails” stuck in the firmament of heaven). The “sphere of stars” was a kind of boundary of the Universe in both the geocentric and heliocentric systems of the world. The entire Universe, naturally, was considered visible, and what was beyond it was the “kingdom of heaven”...
Today we know that only a tiny fraction of stars are visible to the naked eye. The whitish strip stretching across the entire sky (Milky Way) turned out, as some ancient Greek philosophers guessed, to be a multitude of stars. Galileo (at the beginning of the 17th century) discerned the brightest of them even with the help of his very imperfect telescope. As the size of telescopes increased and they improved, astronomers were able to gradually penetrate into the depths of the Universe, as if probing it. But it did not immediately become clear that the stars observed in different directions of the sky had some relation to the stars of the Milky Way. One of the first who managed to prove this was the English astronomer and optician V. Herschel. Therefore, the discovery of our Galaxy (it is sometimes called the Milky Way) is associated with his name. However, it is apparently not possible for a mere mortal to see our entire Galaxy. Of course, it is enough to look into an astronomy textbook to find clear diagrams there: a view of the Galaxy “from above” (with a distinct spiral structure, with arms consisting of stars and gas-dust matter) and a view “from the side” (in this perspective, our stellar island resembles biconvex lens, if you do not go into some details of the structure of the central part of this lens). Schemes, diagrams... Where is at least one photograph of our Galaxy?
Gagarin was the first earthling to see our planet from outer space. Now, probably, everyone has seen photographs of the Earth from space, transmitted from artificial Earth satellites, from automatic interplanetary stations. Forty-one years have passed since Gagarin's flight, and 45 years have passed since the launch of the first satellite - the beginning of the space age. But to this day, no one knows whether a person will ever be able to see the Galaxy by going beyond its borders... For us, this is a question from the realm of science fiction. So let's get back to reality. But just at the same time, please think about the fact that just a hundred years ago, current reality could seem like the most incredible fantasy.
So, the Solar System and our Galaxy have been discovered, in which the Sun is one of trillions of stars (about 6,000 stars are visible to the naked eye in the entire celestial sphere), and the Milky Way is a projection of part of the Galaxy onto the celestial sphere. But just as in the 16th century earthlings realized that our Sun is the most ordinary star, we now know that our Galaxy is one of many other galaxies now discovered. Among them, as in the world of stars, there are giants and dwarfs, “ordinary” and “extraordinary” galaxies, relatively quiet and extremely active. They are located at enormous distances from us. The light from the closest of them rushes towards us for almost two million three hundred thousand years. But we can see this galaxy even with the naked eye; it is in the constellation Andromeda. This is a very large spiral galaxy, similar to ours, and therefore its photographs to some extent “compensate” for the lack of photographs of our Galaxy.
Almost all discovered galaxies can only be seen in photographs taken using modern giant ground-based telescopes or space telescopes. The use of radio telescopes and radio interferometers has helped to significantly supplement optical data. Radio astronomy and extra-atmospheric X-ray astronomy have lifted the curtain on the mystery of the processes occurring in the nuclei of galaxies and in quasars (the most distant currently known objects in our Universe, almost indistinguishable from stars in photographs taken using optical telescopes).
In an extremely huge and practically hidden from view megaworld (or in the Metagalaxy), it was possible to discover its important patterns and properties: expansion, large-scale structure. All this is somewhat reminiscent of another, already discovered and largely unraveled microworld. There they study the very close to us, but also invisible building blocks of the universe (atoms, hadrons, protons, neutrons, mesons, quarks). Having learned the structure of atoms and the patterns of interaction of their electron shells, scientists literally “revitalized” D. I. Mendeleev’s Periodic Table of Elements.
The most important thing is that man turned out to be able to discover and cognize worlds of various scales that were not directly perceived by him (megaworld and microworld).
In this context, astrophysics and cosmology seem to be not original. But here we come to the most interesting part.
The “curtain” of the long-known constellations opened, taking with it the last attempts of our “centrism”: geocentrism, heliocentrism, galaxycentrism. We ourselves, like our Earth, like the Solar System, like the Galaxy, are just “particles” of the structure of the Universe, unimaginable in ordinary scale and in complexity, called the “Metagalaxy”. It includes many galaxy systems of varying complexity (from “binaries” to clusters and superclusters). Agree that at the same time, awareness of the scale of one’s own insignificant size in the vast mega-world does not humiliate a person, but, on the contrary, elevates the power of his Mind, capable of discovering all this and understanding what was discovered earlier.
It would seem that it is time to calm down, since the modern picture of the structure and evolution of the Metagalaxy has been created in general terms. However, firstly, it conceals a lot of fundamentally new things, previously unknown to us, and secondly, it is possible that, in addition to our Metagalaxy, there are other mini-universes that form the still hypothetical Big Universe...
Maybe we should stop there for now. Because now, as they say, we would like to figure out our Universe. The fact is that at the end of the twentieth century it presented astronomy with a big surprise.
Those who are interested in the history of physics know that at the beginning of the twentieth century, some great physicists thought that their titanic work was completed, because everything important in this science had already been discovered and explored. True, a couple of strange “clouds” remained on the horizon, but few imagined that they would soon “turn into” the theory of relativity and quantum mechanics... Is something like this really awaiting astronomy?
It is quite likely, because our Universe, observed with the help of all the power of modern astronomical instruments and seemingly already quite thoroughly studied, may turn out to be just the tip of the universal iceberg. Where is the rest of it? How could such a daring assumption arise about the existence of something huge, material and completely hitherto unknown?
Let us turn again to the history of astronomy. One of her triumphant pages was the discovery of the planet Neptune "at the tip of a pen." The gravitational influence of some mass on the movement of Uranus prompted scientists to think about the existence of a still unknown planet, allowed talented mathematicians to determine its location in the solar system, and then tell astronomers exactly where to look for it on the celestial sphere. And in the future, gravity provided similar services to astronomers: it helped to discover various “outlandish” objects - white dwarfs, black holes. So now, the study of the movement of stars in galaxies and galaxies in their clusters has led scientists to the conclusion about the existence of a mysterious invisible ("dark") matter (or perhaps some form of matter unknown to us), and the reserves of this "matter" should be colossal.
According to the most daring estimates, everything that we observe and take into account in the Universe (stars, gas-dust complexes, galaxies, etc.) is only 5 percent of the mass that “should have been” according to calculations based on laws of gravity. This 5 percent includes the entire megaworld we know, from dust grains and cosmic hydrogen atoms to superclusters of galaxies. Some astrophysicists even include all-pervasive neutrinos here, believing that, despite their small rest mass, neutrinos with their countless numbers make a certain contribution to the same 5 percent.
But perhaps the “invisible matter” (or at least part of it, unevenly distributed in space) is the mass of extinct stars or galaxies, or such invisible cosmic objects as black holes? To some extent, such an assumption is not without meaning, although the missing 95 percent (or, according to other estimates, 60-70 percent) will not be made up. Astrophysicists and cosmologists are forced to consider various other, mostly hypothetical, possibilities. The most fundamental ideas boil down to the fact that a significant part of the “hidden mass” is “dark matter”, consisting of elementary particles unknown to us.
Further research in the field of physics will show which elementary particles, other than those that consist of quarks (baryons, mesons, etc.) or are structureless (for example, muons), can exist in nature. It will probably be easier to solve this mystery if we combine the forces of physicists, astronomers, astrophysicists, and cosmologists. Considerable hopes are placed on data that can be obtained in the coming years in the event of successful launches of specialized spacecraft. For example, it is planned to launch a space telescope (diameter 8.4 meters). It will be able to register a huge number of galaxies (up to the 28th magnitude; recall that luminaries up to the 6th magnitude are visible to the naked eye), and this will make it possible to construct a map of the distribution of “hidden mass” across the entire sky. Certain information can also be extracted from ground-based observations, since the “hidden matter,” having high gravity, should bend the rays of light coming to us from distant galaxies and quasars. By processing images of such light sources on computers, it is possible to register and estimate the invisible gravitating mass. Similar reviews of individual areas of the sky have already been made. (See the article by Academician N. Kardashev “Cosmology and SETI problems”, recently published in the popular science magazine of the Presidium of the Russian Academy of Sciences “Earth and the Universe”, 2002, No. 4.)
In conclusion, let us return to the question formulated in the title of this article. It seems that after all that has been said, it is unlikely that one can confidently give a positive answer to it... The oldest of the most ancient sciences, astronomy is just beginning.
