The history of planet Earth, like human life, is filled with various important events and stages of development that have occurred since its birth. Before planet Earth and all other celestial bodies appeared: planets and stars, clouds of dust flew in space. The Blue Planet, like other objects in the solar system, including the Sun, is believed by scientists to have formed when a cloud of interstellar dust compacted.
The Earth was formed some 10 million years after interstellar dust began to compact. The heat released formed a celestial body from the molten substance. After the planet Earth appeared. Differentiation of the layers of its constituents led to the appearance of an inner core of heavy elements wrapped in a mantle; the accumulation of light elements on the surface caused the formation of a proto-crust. At the same time, the Moon also appeared, possibly due to a strong collision between the Earth and a huge asteroid.
Over time, the planet cooled, a hardened shell appeared on it - the crust, and subsequently the first continents. From the moment planet Earth appeared, it was constantly bombarded by meteorites and icy comets, as a result, enough water accumulated on the surface to form seas and oceans. Thanks to strong volcanic activity and steam, an atmosphere appeared in which there was practically no oxygen. Throughout the history of planet Earth, the continents constantly floated on the molten mantle, sometimes connecting, sometimes separating, this was repeated many times over the course of 4.5 billion years.
Complex chemical reactions gave rise to organic molecules interacting with each other, and increasingly complex molecular structures appeared. As a result, this led to the emergence of molecules capable of self-copying. These were the first steps of Life on Earth. Living organisms developed, bacteria appeared, then multicellular organisms. During the life of these organisms, the composition of the atmosphere changed. Oxygen appeared, which led to the development of a protective layer of ozone.
Life has evolved in numerous forms, and the number of species on Earth is amazing in its diversity. Changes in environmental conditions throughout the history of the planet led to the emergence of new species, many of which subsequently became extinct, others were able to adapt to the new environment and created the modern biosphere.
About 6 million years ago, billions of years after the Earth came into existence, a branch of primate evolutionary differentiation led to the emergence of humans. The ability to walk on the hind legs, a strong increase in brain size and the development of speech were the main factors. First, man learned to make fire, then he achieved success in the development of agriculture. This led to an improvement in life, which led to the formation of communities and after civilizations, with different cultural and religious characteristics. Thanks to their achievements in various fields: science, politics, writing, transportation and communications, humans have become the dominant species on Earth. It is no longer the Earth that forms life forms; man changes the environment in the process of life. For the first time, the history of planet Earth is being created by the forces of the creatures that live on it, and it is We who are forced to solve global issues of climate and other environment to preserve our habitat.
It arose about 4600 million years ago. Since then, its surface has constantly changed under the influence of various processes. The earth apparently formed several million years after a colossal explosion in space. The explosion created a huge amount of gas and dust. Scientists believe that its particles, colliding with each other, united into giant clumps of hot matter, which over time turned into the existing planets.
According to scientists, the Earth arose after a colossal cosmic explosion. The first continents probably formed from molten rock flowing to the surface from vents. As it solidified, it made the earth's crust thicker. Oceans could have formed in the lowlands from droplets contained in volcanic gases. The original one probably consisted of the same gases.
It is thought that the Earth was at first incredibly hot, with a sea of molten rocks on the surface. About 4 billion years ago, the Earth began to slowly cool and split into several layers (see right). The heaviest rocks sank deep into the bowels of the Earth and formed its core, remaining unimaginably hot. Less dense matter formed a series of layers around the core. On the surface itself, molten rocks gradually hardened, forming a solid crust covered with many volcanoes. The molten rock, bursting to the surface, froze, forming the earth's crust. Low areas were filled with water.
Earth today
Although the earth's surface seems solid and unshakable, changes are still taking place. They are caused by various kinds of processes, some of which destroy the earth's surface, while others recreate it. Most changes occur extremely slowly and are detected only by special devices. It takes millions of years for a new mountain range to form, but a powerful volcanic eruption or a monstrous earthquake can transform the surface of the Earth in a matter of days, hours and even minutes. In 1988, an earthquake in Armenia that lasted about 20 seconds destroyed buildings and killed more than 25,000 people.
Structure of the Earth
In general, the Earth has the shape of a ball, slightly flattened at the poles. It consists of three main layers: crust, mantle and core. Each layer is formed by different types of rocks. The picture below shows the structure of the Earth, but the layers are not to scale. The outer layer is called the earth's crust. Its thickness is from 6 to 70 km. Beneath the crust is the upper layer of the mantle, formed by hard rock. This layer, together with the crust, is called and has a thickness of about 100 km. The part of the mantle underlying the lithosphere is called the asthenosphere. It is approximately 100 km thick and is likely composed of partially molten rocks. the mantle varies from 4000°C near the core to 1000″C in the upper part of the asthenosphere. The lower mantle probably consists of solid rock. The outer core is composed of iron and nickel, apparently molten. The temperature of this layer can reach 55СТГС. The temperature of the subcore can be above 6000'C. It is solid due to the colossal pressure of all the other layers. Scientists believe that it consists mainly of iron (more about this in the article ““).
Man has long sought to understand the world that surrounds him, and above all the Earth - our home. How did the Earth originate? This question has worried humanity for more than one millennium.
Numerous legends and myths of various peoples about the origin of our planet have reached us. They are united by the statement that the Earth was created by the intelligent activity of mythical heroes or gods.
The first hypotheses, i.e. scientific assumptions, about the origin of the Earth began to appear only in the 18th century, when science had accumulated a sufficient amount of information about our planet and the Solar system. Let's take a look at some of these hypotheses.
French scientist Georges Buffon (1707-1788) suggested that the globe arose as a result of a catastrophe. At a very distant time, some celestial body (Buffon believed that it was a comet) collided with the Sun. The collision produced a lot of “splash.” The largest of them, gradually cooling, gave rise to planets.
The German scientist Immanuel Kant (1724-1804) explained the possibility of the formation of celestial bodies differently. He suggested that the solar system originated from a giant, cold dust cloud. The particles of this cloud were in constant disorderly movement, mutually attracted each other, collided, stuck together, forming condensations that began to grow and eventually gave rise to the Sun and planets.
Pierre Laplace (1749-1827), French astronomer and mathematician, proposed his hypothesis explaining the formation and development of the Solar system. In his opinion, the Sun and planets arose from a rotating hot gas cloud. Gradually cooling, it contracted, forming numerous rings, which, as they became denser, created planets, and the central clot turned into the Sun.
The emergence of the solar system according to Kant's hypothesis
The emergence of the solar system according to Laplace's hypothesis
At the beginning of this century, the English scientist James Jeans (1877-1946) put forward a hypothesis that explained the formation of the planetary system: once upon a time another star flew near the Sun, which, with its gravity, tore out part of the matter from it. Having condensed, it gave rise to planets.
The emergence of planets according to Schmidt's hypothesis
Modern ideas about the origin of the solar system
Our compatriot, the famous scientist Otto Yulievich Schmidt (1891-1956), proposed his hypothesis of planet formation in 1944. He believed that billions of years ago the Sun was surrounded by a giant cloud that consisted of particles of cold dust and frozen gas. They all revolved around the Sun. Being in constant motion, colliding, mutually attracting each other, they seemed to stick together, forming clumps. Gradually, the gas and dust cloud flattened, and the clumps began to move in circular orbits. Over time, the planets of our solar system were formed from these clumps.
It is easy to see that the hypotheses of Kant, Laplace, and Schmidt are close in many ways. Many of the thoughts of these scientists formed the basis of the modern understanding of the origin of the Earth and the entire solar system.
Today, scientists suggest that the Sun and planets arose simultaneously from interstellar matter - particles of dust and gas. This cold substance gradually became denser, compressed, and then broke up into several unequal clumps. One of them, the largest, gave rise to the Sun. Its substance, continuing to compress, warmed up. A rotating gas-dust cloud formed around it, which had the shape of a disk. From the dense clumps of this cloud, planets arose, including our Earth.
As you can see, scientists’ ideas about the origin of the Earth, other planets and the entire solar system have changed and developed. And even now there remains a lot of unclear and controversial things. Scientists have to resolve many questions before we know for sure how the Earth came into being.
Scientists who explained the origin of the Earth
Georges Louis Leclerc Buffon is a great French naturalist. In his main work, “Natural History,” he expressed thoughts about the development of the globe and its surface, about the unity of all living things. In 1776 he was elected an honorary foreign member of the St. Petersburg Academy of Sciences.
Immanuel Kant is a great German philosopher, professor at the University of Konigsberg. In 1747-1755 developed a hypothesis about the origin of the solar system, which he outlined in the book “General Natural History and Theory of the Heavens.”
Pierre Simon Laplace was born into the family of a poor farmer. Talent and perseverance allowed him to independently study mathematics, mechanics and astronomy. He achieved his greatest success in astronomy. He studied in detail the movement of celestial bodies (Moon, Jupiter, Saturn) and gave it a scientific explanation. His hypothesis about the origin of the planets existed in science for almost a century.
Academician Otto Yulievich Schmidt was born in Mogilev. Graduated from Kyiv University. For many years he worked at Moscow University. O. Yu. Schmidt was a major mathematician, geographer, and astronomer. He participated in the organization of the drifting scientific station "North Pole-1". An island in the Arctic Ocean, a plain in Antarctica, and a cape in Chukotka are named after him.
Test your knowledge
- What is the essence of J. Buffon's hypothesis about the origin of the Earth?
- How did I. Kant explain the formation of celestial bodies?
- How did P. Laplace explain the origin of the solar system?
- What is D. Jeans' hypothesis about the origin of the planets?
- How does O. Yu. Schmidt’s hypothesis explain the process of the formation of planets?
- What is the current understanding of the origin of the Sun and planets?
Think!
- How did ancient people explain the origin of our planet?
- What are the similarities and differences between the hypotheses of J. Buffon and D. Jeans? Do they explain how the Sun came into being? Do you think these hypotheses are plausible?
- Compare the hypotheses of I. Kant, P. Laplace and O. Yu. Schmidt. What are their similarities and differences?
- Why do you think it was only in the 18th century? did the first scientific assumptions about the origin of the Earth appear?
The first scientific assumptions about the origin of the Earth appeared only in the 18th century. The hypotheses of I. Kant, P. Laplace, O. Yu. Schmidt and many other scientists formed the basis of modern ideas about the origin of the Earth and the entire solar system. Modern scientists suggest that the Sun and planets arose simultaneously from interstellar matter - dust and gas. This substance was compressed, then broke up into several clumps, one of which gave rise to the Sun. A rotating gas-dust cloud arose around it, from the clumps of which planets were formed, including our Earth.
Only relatively recently did people receive factual material that makes it possible to put forward scientifically based 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 often played a fundamental role in them rather than objective reality. But already in those days, ideas and views arose that even today amaze us with their similarity to 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 thing: “The world, one of all, was not created by any of the gods and by any of the people, but was, is and will be an eternally living fire, naturally igniting and naturally extinguishing "
After the fall of the Roman Empire, a difficult time of the Middle Ages began for Europe - the period of the dominance of theology and scholasticism. This period was then replaced by the Renaissance; the works of Nicolaus Copernicus and Galileo Galilei prepared the emergence of progressive cosmogonic ideas. They were expressed at different times by R. Descartes, I. Newton, N. Stenon, I. Kant and P. Laplace.
Hypotheses about the origin of the Earth
R. Descartes' hypothesis
So, in particular, R. Descartes argued that our planet was previously a hot body, like the Sun. And subsequently it cooled down and began to look like an extinct celestial body, in the depths of which fire still remained. The hot core was covered by a dense shell, which consisted of a substance similar to the substance of sunspots. Above was a new shell - made of small fragments resulting from the disintegration of the spots.
Immanuel Kant's hypothesis
1755 - the German philosopher I. Kant suggested that the substance of which the body of the solar system is composed - all the planets and comets, before the start of all transformations, was decomposed into primary elements and filled the entire volume of the Universe in which the bodies formed from them now move. These Kantian ideas that the solar system could have formed as a result of the accumulation of primordial dispersed scattered matter seem surprisingly correct in our time.
P. Laplace's hypothesis
1796 - French scientist P. Laplace expressed similar ideas about the origin of the Earth, knowing nothing about the existing treatise of I. Kant. The emerging hypothesis about the origin of the Earth thus received the name of the Kant-Laplace hypothesis. According to this hypothesis, the Sun and the planets moving around it were formed from a single nebula, which, during rotation, broke up into separate clumps of matter - planets.
The initially fiery liquid Earth cooled down and became 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 occurred in the bowels of the Earth and on its surface.
E. Chladni's hypothesis
Of course, meteorites - aliens from deep space - are of great importance for the development of reliable scientific hypotheses about the origin of the Earth. This is because meteorites have always fallen 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 remains of fireballs of unearthly origin. According to him, meteorites are pieces of interplanetary matter traveling in space, probably fragments of planets.
Modern concept of the origin of the Earth
But not everyone shared this kind of thought in those days; however, by studying stone and iron meteorites, scientists were able to obtain interesting data that was used in cosmogonic constructions. For example, the chemical composition of meteorites was clarified - it mainly turned out to be oxides of silicon, magnesium, iron, aluminum, calcium, and sodium. Consequently, it became possible to find out the composition of other planets, which turned out to be similar 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. Currently, these data have been supplemented with information about 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 gas and dust cloud and began to “function” 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.
Thus, bit by bit, based on isolated isolated facts, the scientific basis of modern cosmogonic views was gradually formed... Most modern cosmogonists adhere to the following point of view.
The starting 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 usually contained volatile components: hydrogen, helium, nitrogen, water vapor, methane, carbon. The primary planetary matter was very homogeneous, and its temperature was quite low.
Due to gravitational forces, interstellar clouds began to compress. The matter was densified to the stage of stars, at the same time its internal temperature increased. The movement of atoms inside the cloud accelerated, and, colliding with each other, the atoms sometimes united. Thermonuclear reactions occurred, during which hydrogen was converted into helium, releasing a huge amount of energy.
In the fury of powerful elements, the Proto-Sun appeared. His birth occurred as a result of a supernova explosion - a not so rare phenomenon. On average, such a star appears in any Galaxy every 350 million years. During a supernova explosion, enormous energy is emitted. The matter ejected as a result of this thermonuclear explosion formed a wide, gradually denser gas plasma cloud around the Proto-Sun. 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 subsequently emerged. The formation of the Proto-Sun and the protoplanetary cloud around it occurred perhaps about 6 billion years ago.
Hundreds of millions of years have passed. Over time, the gaseous matter of the protoplanetary cloud cooled. The most refractory elements and their oxides condensed from the hot gas. As further cooling continued over millions of years, dusty solids appeared in the cloud, and the previously hot gas cloud became comparatively cold again.
Gradually, a wide annular disk 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 internal parts of the gas and dust disk, planets like the Earth 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 began to form. A huge number of comets appeared in the outer zone itself.
Primary Earth
So, approximately 5.5 billion years ago, the first planets, including the primordial Earth, arose from cold planetary matter. At that time, it was a cosmic body, but not yet a planet; it did not have a core or mantle, and there were not even solid surface areas.
The formation of the Proto-Earth was an extremely important milestone - it was the birth of the Earth. In those days, the usual, well-known geological processes did not occur on Earth, which is why this period of the planet’s evolution is called pre-geological, or astronomical.
The proto-earth was a cold accumulation of cosmic matter. Under the influence of gravitational compaction, heating from continuous impacts of cosmic bodies (comets, meteorites) and the release of heat by radioactive elements, the surface of the Proto-Earth began to heat up. There is no consensus among scientists about the magnitude of the heating. According to the Soviet scientist V. Fesenko, the substance of the Proto-Earth heated up to 10,000°C and, as a result, passed into a molten state. According to the assumptions 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, the heating of the Proto-Earth contributed to the differentiation of its material, which continued throughout subsequent geological history.
The differentiation of the Proto-Earth substance led to the concentration of heavy elements in its internal regions, and lighter elements on the surface. This, in turn, predetermined the further division into the 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 at that time the mass of the Earth could not retain light gases near its surface.
The formation of the core and mantle, and subsequently the atmosphere, completed the first stage of the Earth’s development - pre-geological, or astronomical. The earth has become a solid planet. After which its long geological evolution begins.
Thus, 4-5 billion years ago, the solar wind, hot rays of the Sun and cosmic cold dominated the surface of our planet. The surface was constantly bombarded by cosmic bodies - from dust particles to asteroids...
The question of how the Earth came into being has occupied the minds of people for more than one millennium. The answer to it has always depended on the level of knowledge of people. Initially, there were naive legends about the creation of the world by some divine force. Then the Earth, in the works of scientists, acquired the shape of a ball, which was the center of the Universe. Then, in the 16th century, the doctrine of N. appeared, which placed the Earth in a number of planets revolving around the Sun. This was the first step in a truly scientific solution to the question of the origin of the Earth. Currently, there are several hypotheses, each of which in its own way describes the periods of formation of the Universe and the position of the Earth in.
Kant-Laplace hypothesis
This was the first serious attempt to create a scientific picture of the origin of the solar system. It is associated with the names of the French mathematician Pierre Laplace and the German philosopher Immanuel Kant, who worked at the end of the 18th century. They believed that the progenitor of the solar system was a hot gas-dust nebula, slowly rotating around a dense core at the center. Under the influence of the forces of mutual attraction, the nebula began to flatten and turn into a huge disk. Its density was not uniform, so separation into separate gas rings occurred in the disk. Subsequently, each ring began to thicken and turn into a single gas clump rotating around its axis. Subsequently, the clumps cooled and turned into planets, and the rings around them into satellites.
The main part of the nebula remained in the center, still did not cool down and became the Sun. Already in the 19th century, the insufficiency of this hypothesis was revealed, since it could not always explain new data in science, but its value is still great.
The Soviet geophysicist O.Yu. Schmidt imagined the development of the Solar system somewhat differently, working in the first half of the 20th century. According to his hypothesis, the Sun, traveling through the Galaxy, passed through a cloud of gas and dust and carried part of it along with it. Subsequently, the solid particles of the cloud coalesced and turned into planets, which were 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 outpourings of lava onto the surface as a result of activity. Thanks to this outpouring, the first covers of the Earth were formed.
They stood out from the lavas. They formed a primary one, which did not yet contain oxygen. More than half the volume of the primary atmosphere consisted of water vapor, and its temperature exceeded 100°C. With further gradual cooling of the atmosphere, it occurred, which led to rainfall and the formation of the primary ocean. This happened about 4.5-5 billion years ago. Later, the formation of land began, which consists of thickened, relatively light parts rising above ocean level.
J. Buffon's hypothesis
Not everyone agreed with the evolutionary scenario for the origin of planets around the Sun. Back in the 18th century, the French naturalist Georges Buffon made an assumption, supported and developed by the American physicists Chamberlain and Multon. The essence of these assumptions is this: once upon a time another star flashed in the vicinity of the Sun. Its attraction caused a huge surface on the Sun, stretching in space for hundreds of millions of kilometers. Having broken away, this wave began to swirl around the Sun and disintegrate into clumps, each of which formed its own planet.
F. Hoyle's hypothesis (XX century)
The English astrophysicist Fred Hoyle proposed his own hypothesis. According to it, the Sun had a twin star that exploded. Most of the fragments were carried into outer space, a smaller part remained in the orbit of the Sun and formed planets.
All hypotheses interpret differently the origin of the Solar system and the family ties between the Earth and the Sun, but they are united in the fact that all the planets originated from a single clump of matter, and then the fate of each of them was decided in its own way. The Earth had to travel 5 billion years and experience a series of fantastic transformations before we saw it in its modern form. However, it should be noted that there is not yet a hypothesis that does not have serious shortcomings and answers all questions about the origin of the Earth and other planets of the solar system. But it can be considered established that the Sun and the planets were formed simultaneously (or almost simultaneously) from a single material medium, from a single gas-dust cloud.
