Origin of the Earth determines its age, chemical and physical composition. Our Earth is one of the nine planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto) of the solar system. All the planets of the solar system revolve around the sun in approximately the same plane and in the same direction along elliptical orbits that are very close to circles.
Galaxy - Sun and system of stars. Most of the stars are located in the ring of the Milky Way. Stars are larger or smaller than the Sun. The Sun is located closer to the center of the Galaxy and, together with all the stars, revolves around it.
Outside the Galaxy there are many other Galaxies, which include from 1 to 150 billion stars. Such a large grouping of stars is called a metagalaxy, or the Big Universe. Our metagalaxy was discovered by the American astronomer Edwin Hubble (1924-1926). He established that the Milky Way is the only one of the many "star worlds" that we observe. The galaxy (Milky Way) has a spiral structure. This is an elongated band of stars with a significant thickening in the middle and at the ends.
An innumerable number of Galaxies relatively close to us make up the Archipelago of Star Islands, i.e., forms a system of Galaxies.
Big Universe is a system of archipelagos, several million galaxies. The diameter of the Big Universe is many billions of light years. The universe is infinite in time and space.
The origin of the Earth has been of interest to scientists since ancient times., and many hypotheses have been put forward about this, which can be divided into hypotheses of hot and cold origin.
The German philosopher Kant (1724-1804) put forward a hypothesis according to which the Earth was formed from a nebula consisting of dusty particles, between which there was attraction and repulsion, as a result of which a circular motion of the nebula was formed.
The French mathematician and astronomer Laplace (1749-1827) hypothesized that the Earth was formed from a single hot nebula, but did not explain its movement. According to Kant, the Earth was formed independently of the Sun, and according to Laplace, it is a product of the decay of the Sun (the formation of rings).
In the XIX and XX centuries. in Western Europe, a number of hypotheses were put forward about the origin of the Earth and other planets (Chamberlain, Multiton, Jeans, etc.), which turned out to be idealistic or mechanical and scientifically unfounded. A great contribution to the science of the origin of the Earth and space was made by Russian scientists - Academician O. Yu. Schmidt and V. G. Fesenkov.
Academician O. Yu. Schmidt scientifically proved that the planets (including the Earth) were formed from solid fragmented particles captured by the Sun. When passing through a cluster of such particles, the forces of attraction captured them, and they began to move around the Sun. As a result of the movement, the particles formed clots, which were grouped and turned into planets. According to the hypothesis of O. Yu. Schmidt, the Earth, like other planets of the solar system, was cold from the beginning of its existence. Later, the decay of radioactive elements began in the body of the Earth, as a result of which the bowels of the Earth began to warm up and melt, and its mass began to delaminate into separate zones or spheres with different physical properties and chemical composition.
Academician V. G. Fesenkov to explain his hypothesis proceeded from the fact that the Sun and the planets were formed in a single process of development and evolution from a large clot of gas-dust nebula. This clot looked like a very flattened disk-like cloud. From the most dense hot cloud in the center, the Sun was formed. Due to the movement of the entire mass of the cloud on its periphery, the density was not the same. The denser particles of the clouds became the centers from which the future nine planets of the solar system, including the Earth, began to form. V. G. Fesenkov concluded that the Sun and its planets were formed almost simultaneously from a gas-dust mass with a high temperature.
The shape, size and structure of the globe
The earth has a complex configuration. Its shape does not correspond to any of the regular geometric shapes. Speaking about the shape of the globe, it is believed that the figure of the Earth is limited to an imaginary surface coinciding with the surface of the water in the World Ocean, conditionally continued under the continents in such a way that the plumb line at any point on the globe is perpendicular to this surface. Such a shape is called a geoid, i.e. a form unique to the earth.
The study of the shape of the Earth has a rather long history. The first assumptions about the spherical shape of the Earth belong to the ancient Greek scientist Pythagoras (571-497 BC). However, scientific proof of the sphericity of the planet was given by Aristotle (384-322 BC), the first to explain the nature of lunar eclipses as the shadow of the Earth.
In the 18th century, I. Newton (1643-1727) calculated that the rotation of the Earth causes its shape to deviate from an exact ball and makes it somewhat flattened at the poles. The reason for this is centrifugal force.
Determining the size of the Earth has also occupied the minds of mankind for a long time. For the first time, the size of the planet was calculated by the Alexandrian scientist Eratosthenes of Cyrene (about 276-194 BC): according to his data, the radius of the Earth is about 6290 km. In 1024-1039. AD Abu Reyhan Biruni calculated the radius of the Earth, which turned out to be 6340 km.
For the first time, an exact calculation of the shape and size of the geoid was made in 1940 by A.A. Izotov. The figure calculated by him is named in honor of the famous Russian surveyor F.N. Krasovsky Krasovsky ellipsoid. These calculations showed that the figure of the Earth is a triaxial ellipsoid and differs from the ellipsoid of revolution.
According to measurements, the Earth is a ball flattened from the poles. The equatorial radius (the major semi-axis of the ellipslide - a) is 6378 km 245 m, the polar radius (the minor semi-axis - b) is 6356 km 863 m. The difference between the equatorial and polar radii is 21 km 382 m. Compression of the Earth (the ratio of the difference between a and b to a) is (a-b)/a=1/298.3. In those cases where greater accuracy is not required, the mean radius of the Earth is assumed to be 6371 km.
Modern measurements show that the surface of the geoid is slightly more than 510 million km, and the volume of the Earth is approximately 1.083 billion km. The determination of other characteristics of the Earth - mass and density - is made on the basis of the fundamental laws of physics. So the mass of the Earth is 5.98 * 10 tons. The value of the average density turned out to be 5.517 g / cm.
General structure of the Earth
To date, according to seismological data, about ten interfaces have been distinguished in the Earth, indicating the concentric nature of its internal structure. The main of these boundaries are: the surface of Mohorovichich at depths of 30-70 km on the continents and at depths of 5-10 km under the ocean floor; Wiechert-Gutenberg surface at a depth of 2900 km. These main boundaries divide our planet into three concentric shells - geospheres:
Earth's crust - the outer shell of the Earth, located above the surface of Mohorovichich;
The mantle of the Earth is an intermediate shell bounded by the surfaces of Mohorovic and Wiechert-Gutenberg;
The Earth's core is the central body of our planet, located deeper than the Wiechert-Gutenberg surface.
In addition to the main boundaries, a number of secondary surfaces are distinguished within the geospheres.
Earth's crust. This geosphere makes up a small fraction of the total mass of the Earth. Three types of the earth's crust are distinguished by thickness and composition:
The continental crust is characterized by a maximum thickness reaching 70 km. It is composed of igneous, metamorphic and sedimentary rocks, which form three layers. The thickness of the upper layer (sedimentary) usually does not exceed 10-15 km. Below lies a granite-gneiss layer with a thickness of 10-20 km. In the lower part of the crust lies a balsate layer up to 40 km thick.
The oceanic crust is characterized by low thickness - decreasing to 10-15 km. It also has 3 layers. Upper, sedimentary, does not exceed several hundred meters. The second, balsat, with a total thickness of 1.5-2 km. The lower layer of the oceanic crust reaches a thickness of 3-5 km. This type of earth's crust lacks a granite-gneiss layer.
The crust of transitional regions is usually characteristic of the periphery of large continents, where marginal seas are developed and there are archipelagos of islands. Here, the continental crust is replaced by an oceanic one, and, naturally, in terms of structure, thickness, and rock density, the crust of the transitional regions occupies an intermediate position between the two types of crust indicated above.
Mantle of the Earth. This geosphere is the largest element of the Earth - it occupies 83% of its volume and makes up about 66% of its mass. A number of interfaces are distinguished in the composition of the mantle, the main of which are surfaces occurring at depths of 410, 950 and 2700 km. According to the values of physical parameters, this geosphere is divided into two subshells:
Upper mantle (from the surface of Mohorovichich to a depth of 950 km).
Lower mantle (from a depth of 950 km to the Wiechert-Gutenberg surface).
The upper mantle, in turn, is subdivided into layers. The upper one, lying from the surface of Mohorovichic to a depth of 410 km, is called the Gutenberg layer. Inside this layer, a hard layer and an asthenosphere are distinguished. The earth's crust, together with the solid part of the Gutenberg layer, forms a single rigid layer lying on the asthenosphere, which is called the lithosphere.
Below the Gutenberg layer lies the Golitsin layer. Which is sometimes called the middle mantle.
The lower mantle has a significant thickness, almost 2 thousand km, and consists of two layers.
Earth's core. The central geosphere of the Earth occupies about 17% of its volume and accounts for 34% of its mass. In the section of the core, two boundaries are distinguished - at depths of 4980 and 5120 km. In this regard, it is divided into three elements:
The outer core is from the Wiechert-Gutenberg surface to 4980 km. This substance, which is at high pressures and temperatures, is not a liquid in the usual sense. But it has some of its properties.
Transitional shell - in the interval 4980-5120 km.
Sub-core - below 5120 km. Possibly in a solid state.
The chemical composition of the Earth is similar to that of other terrestrial planets.<#"justify">· lithosphere (crust and uppermost part of the mantle)
· hydrosphere (liquid shell)
· atmosphere (gas shell)
About 71% of the Earth's surface is covered with water, its average depth is about 4 km.
Earth's atmosphere:
more than 3/4 - nitrogen (N2);
about 1/5 - oxygen (O2).
Clouds, consisting of tiny water droplets, cover about 50% of the planet's surface.
The atmosphere of our planet, like its bowels, can be divided into several layers.
· The lowest and densest layer is called the troposphere. Here are the clouds.
· Meteors ignite in the mesosphere.
· Auroras and many orbits of artificial satellites are the inhabitants of the thermosphere. Ghostly silvery clouds hover there.
Hypotheses of the origin of the Earth. The first cosmogonetic hypotheses
A scientific approach to the question of the origin of the Earth and the solar system became possible after the strengthening in science of the idea of material unity in the Universe. There is a science about the origin and development of celestial bodies - cosmogony.
The first attempts to give a scientific justification for the question of the origin and development of the solar system were made 200 years ago.
All hypotheses about the origin of the Earth can be divided into two main groups: nebular (Latin "nebula" - fog, gas) and catastrophic. The first group is based on the principle of the formation of planets from gas, from dust nebulae. The second group is based on various catastrophic phenomena (collision of celestial bodies, close passage of stars from each other, etc.).
One of the first hypotheses was expressed in 1745 by the French naturalist J. Buffon. According to this hypothesis, our planet was formed as a result of the cooling of one of the clots of solar matter ejected by the Sun during its catastrophic collision with a large comet. The idea of J. Buffon about the formation of the Earth (and other planets) from plasma was used in a whole series of later and more advanced hypotheses of the "hot" origin of our planet.
Nebular theories. Hypothesis of Kant and Laplace
Among them, of course, the leading place is occupied by the hypothesis developed by the German philosopher I. Kant (1755). Independently of him, another scientist - the French mathematician and astronomer P. Laplace - came to the same conclusions, but developed the hypothesis more deeply (1797). Both hypotheses are similar in essence and are often considered as one, and its authors are considered the founders of scientific cosmogony.
The Kant-Laplace hypothesis belongs to the group of nebular hypotheses. According to their concept, a huge gas-dust nebula was previously located on the site of the solar system (a dust nebula of solid particles, according to I. Kant; a gas nebula, according to P. Laplace). The nebula was hot and spinning. Under the influence of the laws of gravity, its matter gradually condensed, flattened, forming a nucleus in the center. This is how the primordial sun was formed. Further cooling and compaction of the nebula led to an increase in the angular velocity of rotation, as a result of which, at the equator, the outer part of the nebula separated from the main mass in the form of rings rotating in the equatorial plane: several of them formed. As an example, Laplace cited the rings of Saturn.
Unevenly cooling, the rings were broken, and due to the attraction between the particles, the formation of planets circulating around the Sun took place. The cooling planets were covered with a hard crust, on the surface of which geological processes began to develop.
I. Kant and P. Laplace correctly noted the main and characteristic features of the structure of the solar system:
) the vast majority of the mass (99.86%) of the system is concentrated in the Sun;
) the planets revolve in almost circular orbits and almost in the same plane;
) all planets and almost all of their satellites rotate in the same direction, all planets rotate around their axis in the same direction.
A significant merit of I. Kant and P. Laplace was the creation of a hypothesis, which was based on the idea of the development of matter. Both scientists believed that the nebula had a rotational motion, as a result of which the particles were compacted and the planets and the Sun were formed. They believed that motion is inseparable from matter and is as eternal as matter itself.
The Kant-Laplace hypothesis has existed for almost two hundred years. Subsequently, it was proved to be inconsistent. So, it became known that the satellites of some planets, such as Uranus and Jupiter, rotate in a different direction than the planets themselves. According to modern physics, the gas separated from the central body must dissipate and cannot form into gas rings, and later - into planets. Other significant shortcomings of the Kant and Laplace hypothesis are the following:
It is known that the angular momentum in a rotating body always remains constant and is distributed evenly throughout the body in proportion to the mass, distance and angular velocity of the corresponding part of the body. This law also applies to the nebula from which the sun and planets formed. In the solar system, the momentum does not correspond to the law of distribution of momentum in a mass that has arisen from a single body. The planet of the solar system concentrates 98% of the angular momentum of the system, and the Sun has only 2%, while the Sun accounts for 99.86% of the entire mass of the solar system.
If we add up the rotational moments of the Sun and other planets, then in the calculations it turns out that the primary Sun rotated at the same speed as Jupiter now rotates. In this regard, the Sun must have had the same contraction as Jupiter. And this, as calculations show, is not enough to cause fragmentation of the rotating Sun, which, according to Kant and Laplace, disintegrated due to excess rotation.
At present, it has been proven that a star with an excess of rotation breaks up into parts, and does not form a family of planets. Spectral binary and multiple systems can serve as an example.
catastrophic theories. Jeans hypothesis
earth cosmogonic concentric origin
After the Kant-Laplace hypothesis in cosmogony, several more hypotheses for the formation of the solar system were created.
So-called catastrophic ones appear, which are based on an element of chance, an element of a happy coincidence:
Unlike Kant and Laplace, who "borrowed" from J. Buffon only the idea of the "hot" origin of the Earth, the followers of this trend also developed the very hypothesis of catastrophism. Buffon believed that the Earth and the planets were formed due to the collision of the Sun with a comet; Chamberlain and Multon - the formation of planets is associated with the tidal action of another star passing by the Sun.
As an example of a hypothesis of a catastrophic trend, consider the concept of the English astronomer Jeans (1919). His hypothesis is based on the possibility of another star passing near the Sun. Under the influence of its attraction, a jet of gas escaped from the Sun, which, with further evolution, turned into the planets of the solar system. The gas jet was shaped like a cigar. In the central part of this body revolving around the Sun, large planets formed - Jupiter and Saturn, and at the ends of the "cigar" - the terrestrial planets: Mercury, Venus, Earth, Mars, Pluto.
Jeans believed that the passage of a star past the Sun, which caused the formation of the planets of the solar system, can explain the discrepancy in the distribution of mass and angular momentum in the solar system. The star, which pulled out a gas jet from the Sun, gave the rotating "cigar" an excess of angular momentum. Thus, one of the main shortcomings of the Kant-Laplace hypothesis was eliminated.
In 1943, the Russian astronomer N.I. Pariysky calculated that at a high speed of a star passing by the Sun, the gaseous prominence should have left with the star. At a low speed of the star, the gas jet should have fallen on the Sun. Only in the case of a strictly defined speed of the star could the gaseous prominence become a satellite of the Sun. In this case, its orbit should be 7 times smaller than the orbit of the planet closest to the Sun - Mercury.
Thus, the Jeans hypothesis, as well as the Kant-Laplace hypothesis, could not give a correct explanation for the disproportionate distribution of angular momentum in the solar system
The biggest drawback of this hypothesis is the fact of randomness, the exclusivity of the formation of a family of planets, which contradicts the materialistic worldview and the available facts that indicate the presence of planets in other stellar worlds.
In addition, calculations have shown that the approach of stars in world space is practically impossible, and even if this happened, a passing star could not give the planets motion in circular orbits.
Modern hypotheses
A fundamentally new idea lies in the hypotheses of the "cold" origin of the Earth. The meteorite hypothesis proposed by the Soviet scientist O.Yu.Shmidt in 1944 has been most deeply developed. Other hypotheses of "cold" origin include the hypotheses of K. Weizsacker (1944) and J. Kuiper (1951), in many respects close to the theory of O. Yu. Schmidt, F. Foyle (England), A. Cameron (USA ) and E. Schatzman (France).
The most popular are the hypotheses about the origin of the solar system created by O.Yu. Schmidt and V.G. Fesenkov. Both scientists, when developing their hypotheses, proceeded from the ideas about the unity of matter in the Universe, about the continuous movement and evolution of matter, which are its main properties, about the diversity of the world, due to various forms of the existence of matter.
Hypothesis O.Yu. Schmidt
According to the concept of O.Yu. Schmidt, the solar system was formed from an accumulation of interstellar matter captured by the Sun in the process of movement in the world space. The Sun moves around the center of the Galaxy, making a complete revolution in 180 million years. Among the stars of the Galaxy there are large accumulations of gas-dust nebulae. Proceeding from this, O.Yu. Schmidt believed that the Sun, when moving, entered one of these clouds and took it with it. The rotation of the cloud in the strong gravitational field of the Sun led to a complex redistribution of meteorite particles in mass, density and size, as a result of which some of the meteorites, the centrifugal force of which turned out to be weaker than the gravitational force, were absorbed by the Sun. Schmidt believed that the original cloud of interstellar matter had some rotation, otherwise its particles would fall on the Sun.
The cloud turned into a flat compacted rotating disk, in which, due to the increase in the mutual attraction of the particles, condensation occurred. The resulting clumps-bodies grew at the expense of small particles joining them, like a snowball. In the process of the cloud reversal, when the particles collided, they began to stick together, the formation of larger aggregates and the attachment to them - the accretion of smaller particles that fall into the sphere of their gravitational influence. In this way, the planets and the satellites revolving around them were formed. The planets began to rotate in circular orbits due to the averaging of the orbits of small particles.
The earth, according to O.Yu. Schmidt, also formed from a swarm of cold solid particles. The gradual heating of the Earth's interior occurred due to the energy of radioactive decay, which led to the release of water and gas, which were part of solid particles in small quantities. As a result, the oceans and atmosphere arose, which led to the emergence of life on Earth.
O.Yu.Shmidt, and later his students gave a serious physical and mathematical justification of the meteorite model of the formation of the planets of the solar system. The modern meteorite hypothesis explains not only the features of the motion of the planets (the shape of the orbits, different directions of rotation, etc.), but also the actually observed distribution of them by mass and density, as well as the ratio of the planetary angular momentum to the solar one. The scientist believed that the existing discrepancies in the distribution of momentum of the Sun and planets are explained by different initial moments of momentum of the Sun and the gas-dust nebula. Schmidt calculated and mathematically substantiated the distances of the planets from the Sun and between themselves, and found out the reasons for the formation of large and small planets in different parts of the solar system and the difference in their composition. By means of calculations, the reasons for the rotational motion of the planets in one direction are substantiated.
The disadvantage of the hypothesis is the consideration of the question of the origin of the planets in isolation from the formation of the Sun - the defining member of the system. The concept is not without an element of chance: the capture of interstellar matter by the Sun. Indeed, the possibility of capture by the Sun of a sufficiently large meteorite cloud is very small. Moreover, according to calculations, such a capture is possible only with the gravitational assistance of another nearby star. The probability of a combination of such conditions is so insignificant that it makes the possibility of the capture of interstellar matter by the Sun an exceptional event.
Hypothesis V.G. Fesenkova
The work of the astronomer V.A. Ambartsumyan, who proved the continuity of the formation of stars as a result of the condensation of matter from rarefied gas-dust nebulae, allowed Academician V.G. space. Fesenkov believed that the process of planet formation is widespread in the Universe, where there are many planetary systems. In his opinion, the formation of planets is associated with the formation of new stars arising from the condensation of initially rarefied matter within one of the giant nebulae ("globules"). These nebulae were very rarefied matter (with a density of about 10 g/cm) and consisted of hydrogen, helium, and a small amount of heavy metals. First, the Sun formed in the core of the "globule", which was a hotter, more massive and rapidly rotating star than at present. The evolution of the Sun was accompanied by repeated ejections of matter into the protoplanetary cloud, as a result of which it lost part of its mass and transferred a significant fraction of its angular momentum to the forming planets. Calculations show that during non-stationary ejections of matter from the bowels of the Sun, the actually observed ratio of the angular momentum of the Sun and the protoplanetary cloud (and, consequently, the planets) could develop. The simultaneous formation of the Sun and planets is proved by the same age of the Earth and the Sun.
As a result of the compaction of the gas-dust cloud, a star-shaped cluster was formed. Under the influence of the rapid rotation of the nebula, a significant part of the gas-dust matter was increasingly moving away from the center of the nebula along the plane of the equator, forming something like a disk. Gradually, the compaction of the gas-dust nebula led to the formation of planetary clumps, which subsequently formed the modern planets of the solar system. Unlike Schmidt, Fesenkov believes that the gas-dust nebula was in a hot state. His great merit is the substantiation of the law of planetary distances depending on the density of the medium. VG Fesenkov mathematically substantiated the reasons for the stability of the angular momentum in the solar system by the loss of the Sun's substance when choosing matter, as a result of which its rotation slowed down. VG Fesenkov also argues in favor of the reverse motion of some satellites of Jupiter and Saturn, explaining this by the capture of asteroids by the planets.
Fesenkov attached a great role to the processes of radioactive decay of the isotopes K, U, Th and others, the content of which was then much higher.
To date, a number of options for raditogenic heating of the subsoil have been theoretically calculated, the most detailed of which was proposed by E.A. Lyubimova (1958). According to these calculations, after one billion years, the temperature of the Earth's interior at a depth of several hundred kilometers reached the melting temperature of iron. By this time, apparently, the beginning of the formation of the Earth's core, represented by metals that have sunk to its center - iron and nickel, belongs. Later, with a further increase in temperature, the melting of the most fusible silicates began from the mantle, which, due to their low density, rose upwards. This process, theoretically and experimentally studied by A.P. Vinogradov, explains the formation of the earth's crust.
It is also necessary to note two hypotheses that developed towards the end of the 20th century. They considered the development of the Earth without affecting the development of the solar system as a whole.
The earth was completely melted and, in the process of depletion of internal thermal resources (radiactive elements), gradually began to cool. A hard crust has formed in the upper part. And with a decrease in the volume of the cooled planet, this crust broke, and folds and other forms of relief formed.
There was no complete melting of matter on Earth. In a relatively loose protoplanet, local melting centers (this term was introduced by academician Vinogradov) formed at a depth of about 100 km.
Gradually, the amount of radioactive elements decreased, and the temperature of the LOP decreased. The first high-temperature minerals crystallized from the magma and fell to the bottom. The chemical composition of these minerals differed from that of the magma. Heavy elements were extracted from the magma. And the residual melt was relatively enriched in light. After the 1st phase and a further decrease in temperature, the next phase of minerals crystallized from the solution, also containing more heavy elements. This is how the gradual cooling and crystallization of LOPs occurred. The magma of basic balsatic composition was formed from the initial ultramafic composition of the magma.
A fluid cap (gas-liquid) formed in the upper part of the LOP. Balsate magma was mobile and fluid. It erupted from the LOPs and poured onto the surface of the planet, forming the first hard basaltic crust. The fluid cap also broke through to the surface and, having mixed with the remnants of primary gases, formed the first atmosphere of the planet. Nitrogen oxides were in the primary atmosphere. H, He, inert gases, CO, CO, HS, HCl, HF, CH, water vapor. There was almost no free oxygen. The temperature of the Earth's surface was about 100 C, there was no liquid phase. The interior of the rather loose protoplanet had a temperature close to the melting point. Under these conditions, the processes of heat and mass transfer inside the Earth proceeded intensively. They occurred in the form of thermal convection flows (TCFs). Particularly important are the TSPs that arise in the surface layers. There, cellular thermal structures developed, which at times were rebuilt into a single-cell structure. Ascending SSTs transmitted the impulse of motion to the planet's surface (balsate crust), and a stretch zone was created on it. As a result of extension, a powerful extended fault with a length of 100 to 1000 km is formed in the uplift zone of the TKP. They were called rift faults.
The surface temperature of the planet and its atmosphere cools below 100 C. Water condenses from the primary atmosphere and the primary hydrosphere is formed. The landscape of the Earth is a shallow ocean with a depth of up to 10 m, with separate volcanic pseudo-islands exposed during low tides. There was no permanent sushi.
With a further decrease in temperature, LOP completely crystallized and turned into rigid crystalline cores in the interior of a rather loose planet.
The surface cover of the planet was destroyed by the aggressive atmosphere and hydrosphere.
As a result of all these processes, the formation of igneous, sedimentary and metamorphic rocks took place.
Thus, hypotheses about the origin of our planet explain the current data on its structure and position in the solar system. And space exploration, launches of satellites and space rockets provide many new facts for practical testing of hypotheses and further improvement.
Literature
1. Questions of cosmogony, M., 1952-64
2. Schmidt O. Yu., Four lectures on the theory of the origin of the Earth, 3rd ed., M., 1957;
Levin B. Yu. Origin of the Earth. "Izv. Academy of Sciences of the USSR Physics of the Earth”, 1972, No. 7;
Safronov V.S., Evolution of the pre-planetary cloud and the formation of the Earth and planets, M., 1969; .
Kaplan S. A., Physics of Stars, 2nd ed., M., 1970;
Problems of modern cosmogony, ed. V. A. Ambartsumyan, 2nd ed., M., 1972.
Arkady Leokum, Moscow, "Julia", 1992
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Currently, there are several hypotheses, each of which in its own way describes the periods of the formation of the Universe and the position of the Earth in the solar system.
· Kant-Laplace hypothesis
Pierre Laplace and Immanuel Kant believed that the progenitor of the solar system is a hot gas-dust nebula, slowly rotating around a dense core in the center. Under the influence of forces of mutual attraction, the nebula began to flatten at the poles and turn into a huge disk. Its density was not uniform, so the disc was stratified into separate gas rings. Subsequently, each ring began to thicken and turn into a single gas clot rotating around its axis. Subsequently, the clots cooled down and turned into planets, and the rings around them into satellites. The main part of the nebula remained in the center, still has not cooled down and has become the Sun.
· O.Yu. Schmidt's hypothesis
According to the hypothesis of O.Yu. Schmidt, the Sun, traveling through the Galaxy, passed through a gas and dust cloud and dragged part of it along with it. Subsequently, the solid particles of the cloud were subjected to sticking together and turned into planets, initially cold. The heating of these planets occurred later as a result of compression, as well as the influx of solar energy. The heating of the Earth was accompanied by massive eruptions of lavas to the surface as a result of volcanic activity. Thanks to this outpouring, the first covers of the Earth were formed. Gases were emitted from the lavas. They formed the primary anoxic atmosphere. More than half of the volume of the primary atmosphere was water vapor, and its temperature exceeded 100°C. With further gradual cooling of the atmosphere, condensation of water vapor occurred, which led to rainfall and the formation of a primary ocean. Later, the formation of land began, which is thickened, relatively light parts of lithospheric plates rising above ocean level.
· J. Buffon's hypothesis
The French naturalist Georges Buffon suggested that another star had once passed in the vicinity of the Sun. Its attraction caused a huge tidal wave on the Sun, stretching out in space for hundreds of millions of kilometers. Having broken away, this wave began to twist around the Sun and break up into clots, each of which formed its own planet.
· Hypothesis of F. Hoyle (XX century)
The English astrophysicist Fred Hoyle proposed his own hypothesis. According to her, the Sun had a twin star that exploded. Most of the fragments were carried away into outer space, the smaller part remained in the orbit of the Sun and formed planets.
All hypotheses interpret the origin of the solar system and family ties between the Earth and the Sun in different ways, but they are unanimous in that all the planets originated from a single gas and dust cloud, and then the fate of each of them was decided in its own way.
According to modern concepts, the Earth was formed from a gas and dust cloud about 4 and a half billion years ago. The sun was very hot, so all volatile substances (gases) evaporated from the region of the formation of the Earth. Gravitational forces contributed to the fact that the matter of the gas and dust cloud accumulated on the Earth, which is at the stage of origin. In the beginning, the temperature on Earth was very high, so all matter was in a liquid state. Due to gravitational differentiation, the denser elements sank closer to the center of the planet, while the lighter ones remained on the surface. After some time, the temperature on Earth decreased, the process of solidification began, while the water remained in a liquid state.
The English scientist James Hopwood Jeans built his hypothesis on the assumption that the planets arose from a jet of hot matter torn from the Sun as a result of the attraction of another nearby star. This jet remained in the sphere of attraction of the Sun and began to rotate around it. Due to the attraction of the Sun and the movement given to it by a stray star, it formed a kind of nebula, shaped like an elongated cigar, which eventually broke up into several clots from which the planets arose.
According to US geochemists, the collision of the Earth with the celestial body Theia, which supposedly occurred about 4.5 billion years ago, if it took place, did not make major changes in the structure of the bowels. At least, our planet did not exactly turn into a hot ball.
The modern hypothesis of the origin of the Earth is still the subject of heated cabinet debate, but most scientists agree that everything began from a protoplanetary cloud of cosmic dust and gas. Some scientists were sure that it was cold, others that, on the contrary, it was red-hot, since it was pulled out of the young Sun by the gravity of a massive star passing nearby at that time. The latest version is rapidly losing its fans today, since astrophysicists have proven that such an interpretation of events is extremely unlikely. Therefore, today the hypothesis of a cold protoplanetary cloud dominates.
Approximately 4.54 billion years ago, the Earth began to form from this protoplanetary cloud. The process itself probably took place as follows: since in this cloud the “light” and “heavy” elements were not yet strongly mixed, as a result of the action of gravity, the second (iron and other related metals) began to descend towards the future center of the planet, squeezing out on surface more "light" elements. Scientists called this process gravitational differentiation.
Thus, iron accumulated in the center of the cloud, forming the future core. But during the lowering, the potential energy of the layer of "heavy" elements began to decrease, respectively, the kinetic energy began to increase, that is, heating occurred. It is believed that this heat warmed up our planet to 1200 degrees Celsius (in some places - up to 1600 degrees).
However, the impact of the most perfect refrigerator in nature - space, led to the fact that the surface of the cloud of "light" elements began to cool rapidly, turning from a melt into a solid. This is how the earth's crust was formed. And the area where gravitational differentiation continued (according to the calculations of some geophysicists, this process will continue for about one and a half billion years), and the high temperature was preserved, became the modern mantle.
Approximately 4.5 billion years ago, the solid part of the Earth was fully formed (although the atmosphere and hydrosphere appeared somewhat later). And it was at that time, according to recent research, that a catastrophe occurred, the result of which was the appearance of a satellite and a return to an unstructured state. According to many scientists, most likely, there was a collision with some massive celestial body (named the planet Theia).
At the same time, some geophysicists are sure that the collision was so impressive that the upper part of the Earth melted again. That is, for some time the planet was a ball of molten homogeneous substance, after which, over several tens of millions of years, it again acquired a solid surface.
Yet some scientists have expressed doubt that the consequences of this collision were so significant. They are sure that even a collision with a celestial body could not radically change the existing structure of our planet. More recently, this version has received evidence of its plausibility. And this evidence was presented by stones found near Kostomuksha.
Planet Earth is the only known place where life has been found so far, I say so far because perhaps in the future people will discover another planet or satellite with intelligent life living there, but so far the Earth is the only place where there is life. Life on our planet is very diverse, from microscopic organisms to huge animals, plants and more. And people have always had a question - How and where did our planet come from? There are many hypotheses. The hypotheses of the origin of the Earth are radically different from each other, and some of them are very hard to believe.
This is a very difficult question. It is impossible to look into the past and see how it all began and how it all began to emerge. The first hypotheses of the origin of the planet Earth began to appear in the 17th century, when people had already accumulated a sufficient amount of knowledge about space, our planet and the solar system itself. Now we adhere to two possible hypotheses of the origin of the Earth: Scientific - the Earth was formed from dust and gases. Then the Earth was a dangerous place to live after many years of evolution, the surface of the planet Earth became habitable for our life: Earth's breathable atmosphere, solid surface, and much more. And Religious - God created the Earth in 7 days and settled here all the variety of animals and plants. But at that time, knowledge was not enough to weed out all other hypotheses, and then there were much more of them:
- Georges Louis Leclerc Buffon. (1707–1788)
He made an assumption that no one would believe now. He suggested that the Earth could be formed from a piece of the Sun, which was torn off by some comet that hit our star.
But this theory has been debunked. Edmund Halley, an English astronomer, noticed that the same comet visits our solar system at intervals of several decades. Halley even managed to predict the next appearance of a comet. He also established that the comet changes its orbit a little each time, which means it does not have a significant mass to tear off a “piece” from the Sun.
- Immanuel Kant. (1724–1804)
Our Earth and the entire solar system were formed from a cold and shrinking dust cloud. Kant wrote an anonymous book where he described his hypotheses of the origin of the planet, but it did not attract the attention of scientists. Scientists by this time were considering a more popular hypothesis put forward by Pierre Laplace, a French mathematician.
- Pierre-Simon Laplace (1749–1827)
Laplace suggested that the solar system was formed from a constantly rotating gas cloud heated to an enormous temperature. This theory is very similar to current scientific theory.
- James Jeans (1877–1946)
A certain cosmic body, namely a star, passed too close to our Sun. The solar attraction tore some mass out of this star, forming a sleeve of hot substance, which eventually formed all of our 9 planets. Jeans talked about his hypothesis so convincingly that in a short time it won the minds of people and they believed that this was the only possible occurrence of the planet.
So, we examined the most famous hypotheses of occurrence, they were very unusual and varied. In our time, such people would not even be listened to, because we now have much more knowledge about our solar system and about the Earth than man knew then. Therefore, the hypotheses of the origin of the Earth were based only on the imagination of scientists. Now we can observe and conduct various studies and experiments, but this has not given us a definitive answer about how and from what exactly our planet arose.
