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 in elliptical orbits that are very close to circles.
Galaxy - Sun and star system... 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 contain from 1 to 150 billion stars. Such a large grouping of stars is called the metagalaxy, or the Big Universe. Our metagalaxy was discovered by the American astronomer Edwin Hubble (1924-1926). He found that the Milky Way is the only one of many "starry worlds" that we observe. The galaxy (Milky Way) has a spiral structure. This is an elongated strip of stars with significant thickening in the middle and at the ends.
An innumerable number of relatively close to us Galaxies make up the Archipelago of stellar islands, that is, it 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 on this occasion, many hypotheses have been put forward, which can be divided into hypotheses of hot and cold origin.
The German philosopher Kant (1724-1804) hypothesized that 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 incandescent 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 Art. In Western Europe, a number of hypotheses (Chamberlain, Multon, Jeans, etc.) were put forward about the origin of the Earth and other planets, which turned out to be idealistic or mechanical and scientifically not substantiated. A great contribution to the science of the origin of the Earth and space was made by Russian scientists - Academician O. Yu. Schmidt and VG 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 gravity captured them, and they began to move around the Sun. As a result of the movement, the particles formed clumps, which grouped together and turned into planets. According to the hypothesis of O. Yu. Schmidt, the Earth, like other planets of the solar system, has been cold since the beginning of its existence. Subsequently, the decay of radioactive elements began in the body of the Earth, as a result of which the interior of the Earth began to heat up and melt, and its mass began to stratify 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-dusty nebula. This clot had the appearance of a very flattened disk-like cloud. From the thickest 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. VG Fesenkov concluded that the Sun and its planets were formed almost simultaneously from a gas-dusty mass with a high temperature.
There are about 100 billion stars in one galaxy, and in total there are 100 billion galaxies in our Universe. If you wanted to go on a journey from Earth to the very edge of the universe, it would take you more than 15 billion years, provided that you move at the speed of light - 300,000 km per second. But where did cosmic matter come from? How did the universe come about? The history of the Earth is about 4.6 billion years old. During this time, many millions of species of plants and animals appeared and died out on it; the highest mountain ranges grew and turned to dust; huge continents then split into pieces and scattered in different directions, then collided with each other, forming new giant land masses. How do we all know this? The fact is that, despite all the disasters and cataclysms that the history of our planet is so rich in, surprisingly much of its turbulent past is imprinted in the rocks that exist to this day, in the fossils that are found in them, as well as in the organisms of living beings living on Earth today. Of course, this chronicle is incomplete. We come across only fragments of it, between them gaping voids, whole chapters fall out of the narrative, extremely important for understanding what really happened. And yet, even in such a truncated form, the history of our Earth will not yield in fascination to any detective novel.
Astronomers believe that our world came about as a result of the Big Bang. Having exploded, a giant fireball scattered matter and energy through space, which subsequently thickened, forming billions of stars, and those, in turn, united into numerous galaxies.
The Big Bang Theory.
The theory that most modern scientists adhere to is that the universe was formed as a result of the so-called Big Bang. An incredibly hot fireball, whose temperature reached billions of degrees, exploded at some point and scattered streams of energy and matter particles in all directions, giving them a tremendous acceleration.
Any substance consists of tiny particles - atoms. Atoms are the smallest material particles that can take part in chemical reactions. However, they, in turn, consist of even smaller, elementary particles. There are many types of atoms in the world, which are called chemical elements. Each chemical element includes atoms of a certain size and weight and differs from other chemical elements. Therefore, in the course of chemical reactions, each chemical element behaves only in its own way. Everything in the universe, from the largest galaxies to the smallest living organisms, is made up of chemical elements.
After the Big Bang.
Since the fireball that exploded as a result of the Big Bang had a colossal temperature, the tiny particles of matter had too much energy at first and could not combine with each other to form atoms. However, after about a million years, the temperature of the Universe dropped to 4000 "C, and various atoms began to form from elementary particles. At first, the lightest chemical elements - helium and hydrogen - appeared. Gradually the Universe cooled down more and more and heavier elements were formed. The process of the formation of new atoms and elements. continues to this day in the bowels of stars such as our Sun. Their temperature is unusually high.
The universe was cooling down. The newly formed atoms gathered in giant clouds of dust and gas. Dust particles collided with each other, merged into a single whole. Gravitational forces pulled small objects towards larger ones. As a result, galaxies, stars, planets were formed in the Universe over time.
The earth has a molten core rich in iron and nickel. The earth's crust consists of lighter elements and, as it were, floats on the surface of partially molten rocks that form the Earth's mantle.
Expanding Universe.
The Big Bang turned out to be so powerful that all the matter in the Universe scattered across outer space with great speed. Moreover, the universe continues to expand to this day. We can confidently assert this because distant galaxies are still moving away from us, and the distances between them are constantly increasing. This means that once the galaxies were located much closer to each other than today.
No one knows exactly how the solar system was formed. The main theory is that the sun and planets were formed from a swirling cloud of cosmic gas and dust. The denser parts of this cloud, with the help of gravitational forces, attracted an increasing amount of matter from the outside. As a result, the Sun and all its planets arose from it.
Microwaves from the past.
Based on the assumption that the universe was formed as a result of a "hot" Big Bang, that is, emerged from a giant fireball, scientists tried to calculate to what extent it should have cooled by now. They concluded that the temperature of the intergalactic space should be about -270 ° C. Scientists also determine the temperature of the Universe by the intensity of microwave (thermal) radiation coming from the depths of space. Measurements have confirmed that it is in fact about -270 "C.
How old is the universe?
To find out the distance to a particular galaxy, astronomers determine its size, brightness and color of the light it emits. If the Big Bang theory is correct, then it means that all the galaxies that exist today were originally squeezed into one superdense and hot ball of fire. You just need to divide the distance from one galaxy to another by the speed with which they move away from each other in order to establish how long ago they formed a single whole. This will be the age of the universe. Of course, this method does not allow obtaining accurate data, but nevertheless it gives reason to believe that the age of the Universe is from 12 to 20 billion years.
The lava flow flows out of the crater of Kilauea volcano, located on the island of Hawaii. When lava comes to the surface of the Earth, it solidifies, forming new rocks.
The formation of the solar system.
The galaxies were formed, in all likelihood, about 1 - 2 billion years after the Big Bang, and the solar system arose about 8 billion years later. After all, matter was not evenly distributed over space. Denser areas, thanks to gravitational forces, attracted more and more dust and gas. The size of these areas grew rapidly. They turned into giant swirling clouds of dust and gas - the so-called nebulae.
One such nebula - namely, the solar nebula - thickened to form our Sun. From other parts of the cloud, clumps of matter arose, which became planets, including the Earth. They were held in their circumsolar orbits by the powerful gravitational field of the Sun. As gravitational forces pulled the particles of the sun's matter closer and closer to each other, the Sun became smaller and denser. At the same time, a monstrous pressure arose in the solar core. It was converted into colossal thermal energy, and this, in turn, accelerated the course of thermonuclear reactions inside the Sun. As a result, new atoms were formed and even more heat was released.
The emergence of living conditions.
Roughly the same processes, albeit on a much smaller scale, took place on Earth. The earth's core was rapidly shrinking. Due to nuclear reactions and the decay of radioactive elements, so much heat was released in the bowels of the Earth that the rocks that form it melted. Lighter substances, rich in silicon, a glass-like mineral, separated in the earth's core from the denser iron and nickel and formed the first crust of the earth. After about a billion years, when the Earth cooled significantly, the earth's crust solidified and turned into a solid outer shell of our planet, consisting of solid rocks.
Cooling down, the Earth threw out many different gases from its core. This usually happened during volcanic eruptions. Light gases such as hydrogen or helium mostly escaped into space. However, the Earth's gravity was strong enough to keep the heavier gases at its surface. It was they who formed the basis of the earth's atmosphere. Part of the water vapor from the atmosphere condensed, and oceans arose on Earth. Now our planet was fully prepared to become the cradle of life.
Birth and death of rocks.
Terrestrial land is formed by hard rocks, often covered with soil and vegetation. But where do these rocks come from? New rocks are formed from matter that is born deep in the bowels of the Earth. In the lower layers of the earth's crust, the temperature is much higher than on the surface, and the rocks that make them up are under tremendous pressure. Under the influence of heat and pressure, rocks sag and soften, or even melt altogether. As soon as a weak spot forms in the earth's crust, molten rocks - they are called magma - break through to the Earth's surface. Magma flows out of the vents of volcanoes in the form of lava and spreads over a large area. Freezing, lava turns into solid rock.
Explosions and fire fountains.
In some cases, the birth of rocks is accompanied by tremendous cataclysms, in others it is quiet and imperceptible. There are many varieties of magma, and different types of rocks are formed from them. For example, basaltic magma is very fluid, easily comes to the surface, spreads in wide streams, and quickly solidifies. Sometimes it bursts out of the volcano's mouth with a bright "fiery fountain" - this happens when the earth's crust cannot withstand its pressure.
Other types of magma are much thicker: their density, or consistency, is more like molasses. The gases contained in such magma with great difficulty break through to the surface through its dense mass. Remember how easily air bubbles burst out of boiling water and how much slower it happens when you heat something thicker, like jelly. As the denser magma rises closer to the surface, the pressure on it decreases. The gases dissolved in drink tend to expand, but cannot. When the magma finally bursts out, the gases expand so rapidly that a huge explosion occurs. Lava, rock debris and ash fly in all directions like shells fired from a cannon. A similar eruption occurred in 1902 on Martinique Island in the Caribbean Sea. The catastrophic eruption of the Moptap-Pele volcano completely destroyed the port of Sep-Pierre. About 30,000 people died.
Crystal formation.
Rocks that form from cooling lava are called volcanic, or igneous, rocks. As the lava cools, the minerals contained in the molten rock gradually turn into solid crystals. If the lava cools quickly, the crystals do not have time to grow and remain very small. This happens when basalt is formed. Sometimes lava cools so quickly that it produces a smooth, glassy rock with no crystals at all, such as obsidian (volcanic glass). This usually happens during an underwater eruption or when small particles of lava are thrown from a volcanic vent high into the cold air.
Erosion and weathering of rocks in Cedar Break Canyons, Utah, USA. These canyons were formed as a result of the erosional impact of the river, which laid its bed through layers of sedimentary rocks, "squeezed" upward by the movements of the earth's crust. The exposed mountain slopes were gradually eroded, and debris formed rocky talus on them. In the midst of these taluses protrude outcrops of still solid rocks, which form the edges of the canyons.
Testimonies of the Past.
The size of the crystals contained in volcanic rocks allows us to judge how quickly the lava cooled and at what distance from the Earth's surface it lay. Here is a piece of granite as it looks in polarized light under a microscope. Different crystals have different colors in this image.
Gneiss is a metamorphic rock formed from sedimentary rock under the influence of heat and pressure. The pattern of colored stripes that you see on this piece of gneiss allows you to determine the direction in which the earth's crust, moving, pressed against the layers of rocks. So we get an idea of the events that took place 3.5 billion years ago.
By the folds and faults (breaks) in rocks, we can judge in which direction colossal stresses in the earth's crust acted in geological epochs long past. These folds arose as a result of mountain-forming movements of the earth's crust that began 26 million years ago. In these places, monstrous forces squeezed layers of sedimentary rocks - and folds formed.
Magma does not always reach the Earth's surface. It can linger in the lower layers of the earth's crust and then cools down much more slowly, forming delightful large crystals. This is how granite comes into being. The size of the crystals in some pebbles makes it possible to establish how this rock was formed many millions of years ago.
Hooduz, Alberta, Canada. Rains and sandstorms destroy soft rocks faster than hard rocks, and as a result, outliers (protrusions) with bizarre outlines appear.
Sedimentary "sandwiches".
Not all rocks are like volcanic rocks such as granite or basalt. Many of them are made up of many layers and look like a huge stack of sandwiches. They were formed once from other rocks destroyed by wind, rains and rivers, the fragments of which were washed into lakes or seas, and they settled at the bottom under the water column. Gradually, a huge amount of such precipitation accumulates. They pile up on top of each other, forming layers hundreds and even thousands of meters thick. The water of a lake or sea presses on these deposits with tremendous force. The water inside them is squeezed out, and they are pressed into a dense mass. At the same time, the mineral substances previously dissolved in the squeezed out water, as it were, cement this entire mass, and as a result, a new rock is formed from it, which is called sedimentary.
Both volcanic and sedimentary rocks can be pushed upward by the movements of the earth's crust, forming new mountain systems. Colossal forces are involved in the formation of mountains. Under their influence, rocks either get very hot or shrink monstrously. At the same time, they are transformed - transformed: one mineral can turn into another, the crystals are flattened and take on a different arrangement. As a result, in place of one rock, another appears. Rocks formed during the transformation of other rocks under the influence of the above forces are called metamorphic.
Nothing lasts forever, not even mountains.
At first glance, nothing could be stronger and more durable than a huge mountain. Alas, this is just an illusion. Based on the geological time scale, which counts for millions and even hundreds of millions of years, the mountains turn out to be just as transient as everything else, including you and me.
Any rock, as soon as it begins to be exposed to the atmosphere, will instantly collapse. If you look at a fresh piece of rock or a split peel, you will see that the newly formed surface of the rock is often of a completely different color than the old one that has been in the air for a long time. This is due to exposure to oxygen in the atmosphere and, in many cases, rainwater. Because of them, various chemical reactions occur on the surface of the rock, gradually changing its properties.
Over time, these reactions lead to the release of the minerals that hold the rock together, and it begins to crumble. Tiny cracks form in the rock, into which water penetrates. Freezing, this water expands and tears apart the rock from the inside. When the ice melts, this rock will simply fall apart. Very soon, the pieces of rock that have fallen off will be washed away by the rains. This process is called erosion.
Muir Glacier in Alaska. The destructive effect of the glacier and stones frozen into it from below and from the sides gradually causes erosion of the walls and bottom of the valley along which it moves. As a result, long strips of rock debris - the so-called moraines - are formed on the ice. At the confluence of two neighboring glaciers, their moraines also join.
Destroyer water.
Chunks of shattered rock eventually end up in rivers. The current drags them along the river bed and grinds them off the rock, which forms the channel itself, until the surviving debris finally finds a quiet refuge at the bottom of a lake or sea. Frozen water (ice) is even more destructive. Glaciers and ice sheets drag along with them a lot of large and small fragments of rocks frozen into their ice sides and belly. These debris cut deep grooves in the rocks along which glaciers move. The glacier can carry rock debris that fell on top of it for many hundreds of kilometers.
Sculptures created by the wind
The wind also destroys rocks. This happens especially often in deserts, where the wind carries millions of the smallest grains of sand. Grains of sand are mostly composed of quartz, an extremely durable mineral. A whirlwind of grains of sand hits the rocks, knocking out more and more grains of sand from them.
Often the wind piles sand into large sandy hills or dunes. Each gust of wind brings a new layer of grains of sand to the dunes. The location of the slopes and the steepness of these sandy hills make it possible to judge the direction and strength of the wind that created them.
Glaciers make deep U-shaped valleys on their way. In Nantfrancone, Wales, glaciers disappeared in prehistoric times, leaving behind a wide valley that is clearly large for the small river that flows through it today. A small lake in the foreground is blocked off by a strip of extra strong rock.
Until now, the Big Bang theory is considered the main theory of the origin of the cradle of humanity. According to astronomers, an infinitely long time ago in outer space there was a huge incandescent ball, whose temperature was calculated in millions of degrees. As a result of chemical reactions taking place inside the fiery sphere, an explosion occurred, scattering a huge amount of the smallest particles of matter and energy in space. Initially, these particles were too hot. Then the Universe cooled down, the particles were attracted to each other, accumulating in one space. The lighter elements were attracted to the heavier ones, which arose as a result of the gradual cooling of the universe. This is how galaxies, stars, planets were formed.
In support of this theory, scientists cite the structure of the Earth, whose inner part, called the core, consists of heavy elements - nickel and iron. The core, in turn, is covered with a thick mantle of incandescent rocks, which are lighter. The surface of the planet, in other words, the earth's crust, seems to float on the surface of molten masses, as a result of their cooling.
Formation of living conditions
Gradually, the globe cooled down, creating more and more dense soil areas on its surface. The volcanic activity of the planet at that time was quite active. As a result of eruptions of magma, a huge amount of various gases was thrown into space. The lightest, such as helium and hydrogen, instantly evaporated. Heavier molecules remained above the planet's surface, attracted by its gravitational fields. Under the influence of external and internal factors, the vapors of the emitted gases became a source of moisture, the first precipitation appeared, which played a key role in the emergence of life on the planet.
Gradually, internal and external metamorphoses led to the diversity of the landscape to which mankind has long been accustomed to:
- mountains and valleys formed;
- seas, oceans and rivers appeared;
- a certain climate was formed in each area, which gave impetus to the development of one or another form of life on the planet.
The opinion about the tranquility of the planet and that it is finally formed is wrong. Under the influence of endogenous and exogenous processes, the planet's surface is still being formed. By his destructive management, a person contributes to the acceleration of these processes, which leads to the most catastrophic consequences.
Only relatively recently did people receive factual material that makes it possible to put forward scientifically grounded hypotheses about the origin of the Earth, but this question has worried the minds of philosophers since time immemorial.
First performances
Although the first ideas about the life of the Earth were based only on empirical observations of natural phenomena, nevertheless, fantastic fiction rather than objective reality often played a fundamental role in them. But already in those days, ideas and views arose, which in our days amaze us with their similarity with our ideas about the origin of the Earth.
So, for example, the Roman philosopher and poet Titus Lucretius Carus, who is known as the author of the didactic poem "On the Nature of Things", believed that the Universe is infinite and there are many worlds similar to ours in it. The ancient Greek scientist Heraclitus (500 BC) wrote about the same: “The world, one of everything, was not created by any of the gods or any of people, but was, is and will be an eternally living fire, naturally flammable and naturally extinguished ".
After the fall of the Roman Empire for Europe came a difficult time of the Middle Ages - the period of the dominance of theology and scholasticism. This period was then replaced by the Renaissance, the works of Nicolaus Copernicus, Galileo Galilei prepared the emergence of progressive cosmogonic ideas. They were expressed at different times by R. Descartes, I. Newton, N. Steenon, I. Kant and P. Laplace.
Hypotheses of the origin of the Earth
R. Descartes hypothesis
So, in particular, R. Descartes argued that our planet was previously a red-hot body, like the Sun. And later it cooled down and began to represent itself as an extinct celestial body, in the depths of which fire was still preserved. The incandescent core was covered with a dense shell, which consisted of a substance similar to that of sunspots. Above, there was a new shell - made of small fragments resulting from the disintegration of spots.
I. Kant's hypothesis
1755 - German philosopher I. Kant suggested that the substance of which the body of the solar system - all planets and comets - was decomposed into primary elements and filled the entire volume of the Universe in which the bodies now formed from them move. These ideas of Kant that the solar system could have formed as a result of the accumulation of primary dispersed scattered matter seem surprisingly correct in our time.
P. Laplace's hypothesis
1796 - the French scientist P. Laplace expressed similar ideas about the origin of the Earth, knowing nothing about the existing treatise by I. Kant. The hypothesis that appeared about the origin of the Earth was thus called the Kant-Laplace hypothesis. According to this hypothesis, the Sun and the planets moving around it were formed from a single nebula, which, when rotating, disintegrated into separate clumps of matter - planets.
Initially, the fiery liquid Earth cooled down, covered with a crust, which warped as the depths cooled and their volume decreased. It should be noted that the Kant-Laplace hypothesis prevailed among other cosmogonic views for more than 150 years. It was on the basis of this hypothesis that geologists explained all the geological processes that took place in the bowels of the Earth and on its surface.
E. Chladni's hypothesis
Of great importance for the development of reliable scientific hypotheses about the origin of the Earth are of course meteorites - aliens from distant space. All because meteorites have always been falling on our planet. However, they were not always considered aliens from outer space. One of the first to correctly explain the appearance of meteorites was the German physicist E. Chladni, who proved in 1794 that meteorites are the remnants of fireballs of unearthly origin. According to him, meteorites are pieces of interplanetary matter wandering in space, probably also fragments of planets.
The modern concept of the origin of the Earth
But this kind of thought in those days was not shared by everyone, however, studying stone and iron meteorites, scientists were able to obtain interesting data that were used in cosmogonic constructions. For example, the chemical composition of meteorites was found out - basically it turned out that these are oxides of silicon, magnesium, iron, aluminum, calcium, sodium. Consequently, it became possible to find out the composition of other planets, which turned out to be akin to the chemical composition of our Earth. The absolute age of the meteorites was also determined: it is in the range of 4.2-4.6 billion years. At the moment, these data have been supplemented with information on the chemical composition and age of the rocks of the Moon, as well as the atmospheres and rocks of Venus and Mars. These new data show, in particular, that our natural satellite, the Moon, was formed from a cold cloud of gas and dust and began "functioning" 4.5 billion years ago.
A huge role in substantiating the modern concept of the origin of the Earth and the solar system belongs to the Soviet scientist, academician O. Schmidt, who made a significant contribution to solving this problem.
So bit by bit, according to separate scattered facts, the scientific basis of modern cosmogonic views was gradually formed ... Most modern cosmogonists adhere to the following point of view.
The initial material for the formation of the solar system was a gas and dust cloud located in the equatorial plane of our Galaxy. The substance of this cloud was in a cold state and, as a rule, contained volatile components: hydrogen, helium, nitrogen, water vapor, methane, carbon. The primary planetary matter was very homogeneous, and its temperature was rather low.
Due to the forces of gravity, interstellar clouds began to shrink. The substance became denser to the stage of stars, at the same time its internal temperature increased. The movement of atoms inside the cloud was accelerated, and, colliding with each other, the atoms sometimes combined. Thermonuclear reactions took place, during which hydrogen was converted into helium, while a huge amount of energy was released.
In the fury of powerful elements, the Protosun appeared. Its birth occurred as a result of a supernova explosion - a phenomenon not so rare. On average, such a star appears in any galaxy every 350 million years. During a supernova explosion, gigantic energy is emitted. The material ejected as a result of this thermonuclear explosion formed a wide, gradually thickening gas plasma cloud around the Protosun. It was a kind of nebula in the form of a disk with a temperature of several million degrees Celsius. From this protoplanetary cloud, planets, comets, asteroids and other celestial bodies of the solar system arose later. The formation of the Protosun and the protoplanetary cloud around it occurred possibly about 6 billion years ago.
Hundreds of millions of years have passed. Over time, the gaseous matter of the protoplanetary cloud cooled down. The most refractory elements and their oxides were condensed from the hot gas. As the cooling continued for millions of years, dust-like solids appeared in the cloud, and the previously incandescent gas cloud became comparatively cold again.
Gradually, a wide annular disk was formed around the young Sun as a result of the condensation of dusty matter, which subsequently disintegrated into cold swarms of solid particles and gas. From the inner parts of the gas-dust disk, planets of the Earth type began to form, consisting, as a rule, of refractory elements, and from the peripheral parts of the disk, large planets rich in light gases and volatile elements. In the very outer zone, a huge number of comets appeared.
Primary Earth
So about 5.5 billion years ago, the first planets, including the primary Earth, arose from the cold planetary matter. In those days, it was a cosmic body, but not yet a planet, it did not have a core and mantle, and even solid surface areas did not exist.
The formation of Proto-Earth was an extremely important milestone - it was the birth of the Earth. In those days, ordinary, well-known geological processes did not take place on Earth, therefore this period of the planet's evolution is called pre-geological, or astronomical.
Proto-earth was a cold accumulation of cosmic matter. Under the influence of gravitational compaction, heating from the continuous impacts of cosmic bodies (comets, meteorites) and the release of heat by radioactive elements, the surface of Proto-Earth began to heat up. There is no consensus among scientists about the amount of warming up. According to the Soviet scientist V. Fesenko, the substance of Proto-Earth heated up to 10,000 ° C and, as a result, passed into a molten state. According to the assumption of other scientists, the temperature could barely reach 1,000 ° C, and still others deny even the very possibility of melting the substance.
Be that as it may, but the warming up of Proto-earth contributed to the differentiation of its material, which continued throughout the subsequent geological history.
Differentiation of the substance of Proto-Earth led to the concentration of heavy elements in its inner regions, and on the surface - lighter ones. This, in turn, predetermined the further division into core and mantle.
Initially, our planet did not have an atmosphere. This can be explained by the fact that gases from the protoplanetary cloud were lost in the first stages of formation, because then the mass of the Earth could not keep light gases near its surface.
The formation of the core and mantle, and later the atmosphere, completed the first stage of the Earth's development - pre-geological, or astronomical. The earth has become a solid planet. After that, its long geological evolution begins.
Thus, 4-5 billion years ago, the solar wind, hot rays of the Sun and cosmic cold prevailed on the surface of our planet. The surface was constantly bombarded by cosmic bodies - from dust particles to asteroids ...
1. Introduction ……………………………………………… 2 p.
2. Hypotheses of the formation of the Earth ……………………… ... 3 - 6 pages.
3. Internal structure of the Earth ………………………… 7 - 9 pages.
4. Conclusion …………………………………………… 10 p.
5. References …………………………………. 11 p.
Introduction.
At all times, people wanted to know where and how the world in which we live came about. There are many legends and myths that have come from ancient times. But with the advent of science in its modern understanding, the mythological and religious ones are replaced by scientific ideas about the origin of the world.
At the present time, a situation has been created in science that the development of the cosmogonic theory and the restoration of the early history of the solar system can be carried out mainly in an inductive way, based on the comparison and generalization of empirical data obtained quite recently on the material of meteorites, planets and the moon. Since we learned a lot about the structure of atoms and the behavior of their compounds under various thermodynamic conditions, and absolutely reliable and accurate data were obtained about the composition of cosmic bodies, the solution to the problem of the origin of our planet was placed on a solid chemical basis, which was lacking in previous cosmogonic constructions. It should be expected in the near future that the solution of the problems of the cosmogony of the solar system in general and the problem of the origin of our Earth in particular will achieve great success at the atomic-molecular level, just as at the same level the genetic problems of modern biology are brilliantly solved before our eyes.
In the current state of science, a physicochemical approach to solving the problems of the cosmogony of the solar system is absolutely inevitable. Therefore, the long-known mechanical features of the solar system, to which the classical cosmogonic hypotheses were given the main attention, must be interpreted in close connection with physicochemical processes in the early history of the solar system. Recent advances in the chemical study of individual bodies of this system allow us to approach the restoration of the history of the Earth's matter in a completely new way and, on this basis, restore the framework of those conditions in which the birth of our planet took place - the formation of its chemical composition and the formation of a shell structure.
Thus, the purpose of this work is to tell about the most famous hypotheses of the formation of the Earth, as well as about its internal structure.
Hypotheses of the formation of the Earth.
At all times, people wanted to know where and how the world in which we live came about. There are many legends and myths that have come from ancient times. But with the advent of science in its modern understanding, the mythological and religious ones are replaced by scientific ideas about the origin of the world. The first scientific hypotheses about the origin of the Earth and the solar system, based on astronomical observations, were put forward only in the 18th century.
All hypotheses about the origin of the Earth can be divided into two main groups:
1. Nebular (lat. "Nebula" - fog, gas) - the principle of the formation of planets from gas, from dust nebulae is the cornerstone;
2. Catastrophic - based on the principle of the formation of planets due to various catastrophic phenomena (collision of celestial bodies, close passage of stars from each other, etc.).
Nebular hypotheses of Kant and Laplace. The first scientific hypothesis about the origin of the solar system was the hypothesis of Immanuel Kant (1755). Kant believed that the solar system arose from some primordial matter, previously freely scattered in space. Particles of this matter moved in different directions and, colliding with each other, lost speed. The heaviest and densest of them, under the influence of the force of gravity, connected with each other, forming a central clot - the Sun, which, in turn, attracted more distant, smaller and lighter particles. Thus, a number of rotating bodies arose, the trajectories of which were mutually intersecting. Some of these bodies, initially moving in opposite directions, were eventually drawn into a single stream and formed rings of gaseous matter, located approximately in the same plane and rotating around the Sun in the same direction, without interfering with each other. In separate rings denser nuclei were formed, to which lighter particles were gradually attracted, forming globular accumulations of matter; this is how the planets were formed, which continued to circle around the sun in the same plane as the original rings of gaseous matter.
Independently of Kant, another scientist - the French mathematician and astronomer P. Laplace - came to the same conclusions, but developed a hypothesis more deeply (1797). Laplace believed that the Sun originally existed in the form of a huge incandescent gaseous nebula (nebula) with an insignificant density, but of colossal size. This nebula, according to Laplace, originally rotated slowly through space. Under the influence of gravitational forces, the nebula gradually shrank, and its speed of rotation increased. The resulting increasing centrifugal force gave the nebula a flattened and then lenticular shape. In the equatorial plane of the nebula, the relationship between attraction and centrifugal force changed in favor of this latter, so that ultimately the mass of matter accumulated in the equatorial zone of the nebula separated from the rest of the body and formed a ring. New rings were sequentially separated from the nebula, which continued to rotate, which, condensing at certain points, gradually turned into planets and other bodies of the solar system. In total, ten rings separated from the original nebula, which disintegrated into nine planets and an asteroid belt - small celestial bodies. The satellites of individual planets were formed from the substance of the secondary rings, detached from the incandescent gaseous mass of the planets.
Due to the continued compaction of matter, the temperature of the newly formed bodies was extremely high. At that time, our Earth, according to P. Laplace, was an incandescent gaseous sphere that shone like a star. Gradually, however, this sphere cooled down, its matter passed into a liquid state, and then, as it cooled further, a solid crust began to form on its surface. This crust was shrouded in heavy atmospheric vapors, from which water condensed as it cooled. Both theories are similar to each other in essence and are often considered as one, mutually complementary to each other, therefore in the literature they are often referred to under the general name as the Kant-Laplace hypothesis. Since science did not have more acceptable explanations at that time, this theory had many followers in the 19th century.
Jeans's catastrophic theory. After the Kant-Laplace hypothesis in cosmogony, several more hypotheses of the formation of the solar system were created. So-called catastrophic hypotheses appear, based on an element of a coincidence. As an example of a catastrophic direction hypothesis, consider the concept of the British 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 planets of the solar system. Jeans believed that the passage of a star past the sun helped to explain the discrepancy in the distribution of mass and angular momentum in the solar system. But in 1943. The Russian astronomer N.I. Pariyskiy calculated that only in the case of a strictly defined speed of the star, the gas clot could become a satellite of the Sun. In this case, its orbit should be 7 times less than the orbit of the planet closest to the Sun - Mercury.
Thus, the Jeans hypothesis could not provide a correct explanation for the disproportionate distribution of the angular momentum in the solar system. The biggest drawback of this hypothesis is the fact of chance, which contradicts the materialistic worldview and the available facts about the finding 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 movement in circular orbits.
The Big Bang Theory. The theory that most modern scientists adhere to is that the universe was formed as a result of the so-called Big Bang. An incredibly hot fireball, whose temperature reached billions of degrees, exploded at some point and scattered streams of energy and matter particles in all directions, giving them a tremendous acceleration. Since the fireball that exploded as a result of the Big Bang had a colossal temperature, the tiny particles of matter had too much energy at first and could not combine with each other to form atoms. However, after about a million years, the temperature of the Universe dropped to 4000 "C, and various atoms began to form from elementary particles. First, the lightest chemical elements - helium and hydrogen, formed, their cluster was formed. Gradually, the Universe cooled more and more and heavier elements were formed. For many billions of years, there has been an increase in masses in accumulations of helium and hydrogen. The growth of mass continues until a certain limit is reached, after which the force of mutual attraction of particles inside the gas-dust cloud is very strong and then the cloud begins to compress (collapse). In the process of collapse, high pressure develops inside the cloud, conditions favorable for the reaction of thermonuclear fusion - the fusion of light nuclei of hydrogen with the formation of heavy elements.A star is born in place of the collapsing cloud.As a result of the birth of a star, more than 99% of the mass of the original cloud is in the body of the star, and the rest form scattered clouds of solid particles from Later, the planets of the stellar system are formed.
Modern theories. In recent years, a number of new hypotheses have been put forward by American and Soviet scientists. If earlier it was believed that a continuous process of heat transfer took place in the evolution of the Earth, then in new theories the development of the Earth is considered as a result of many heterogeneous, sometimes opposite processes. Simultaneously with a decrease in temperature and a loss of energy, other factors could also act, causing the release of large amounts of energy and thus compensating for the loss of heat. One of such modern assumptions is the "dust cloud theory", its author is the American astronomer F. L. Weiple (1948). However, in essence, this is nothing more than a modified version of the Kant-Laplace nebular theory. Also popular are the hypotheses of Russian scientists 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 existence of matter.
It is curious that at a new level, armed with more advanced technology and deeper knowledge of the chemical composition of the solar system, astronomers returned to the idea that the Sun and the planets arose from a vast, not cold nebula, consisting of gas and dust. Powerful telescopes have discovered numerous gas and dust "clouds" in interstellar space, some of which actually condense into new stars. In this regard, the original theory of Kant-Laplace was revised using the latest data; it can still serve well in explaining the process of the origin of the solar system.
Each of these cosmogonic theories has contributed to the elucidation of a complex set of problems associated with the origin of the Earth. All of them consider the emergence of the Earth and the solar system as a natural result of the development of stars and the universe as a whole. The Earth appeared simultaneously with other planets, which, like it, revolve around the Sun and are the most important elements of the solar system.
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