Excited the minds of scientists for many millennia. There were and are many versions - from purely theological to modern, formed on the basis of data from deep space research.

But since no one happened to be present during the formation of our planet, it remains to rely only on indirect "evidence". Also, the most powerful telescopes are of great help in removing the veil from this mystery.

solar system

The history of the Earth is inextricably linked with the appearance and around which it revolves. And so you have to start from afar. According to scientists, after the Big Bang, it took one or two billion years for galaxies to become approximately what they are now. The solar system, on the other hand, arose, presumably, eight billion years later.

Most scientists agree that it, like all similar space objects, arose from a cloud of dust and gas, since matter in the Universe is distributed unevenly: somewhere there was more of it, and in another place - less. In the first case, this leads to the formation of nebulae from dust and gas. At some stage, perhaps due to external influence, such a cloud contracted and began to rotate. The reason for what happened, probably lies in a supernova explosion somewhere in the vicinity of our future cradle. However, if all are formed in approximately the same way, then this hypothesis looks doubtful. Most likely, having reached a certain mass, the cloud began to attract more particles to itself and contract, and acquired a rotational moment due to the uneven distribution of matter in space. Over time, this swirling clot became more and more dense in the middle. Thus, under the influence of enormous pressure and rising temperatures, our Sun arose.

Hypotheses of different years

As mentioned above, people have always wondered how the planet Earth was formed. The first scientific justification appeared only in the seventeenth century AD. At that time, many discoveries were made, including physical laws. According to one of these hypotheses, the Earth was formed as a result of the collision of a comet with the Sun as a residual substance from the explosion. According to another, our system arose from a cold cloud of cosmic dust.

The particles of the latter collided with each other and connected until the Sun and planets were formed. But French scientists suggested that the specified cloud was red-hot. As it cooled, it rotated and contracted, forming rings. From the latter, the planets were formed. And the sun appeared in the center. The Englishman James Jeans suggested that another star once flew past our star. She pulled out with her attraction the substance from the Sun, from which the planets subsequently formed.

How the Earth Was Formed

According to modern scientists, the solar system arose from cold particles of dust and gas. The substance was compressed and disintegrated into several parts. From the largest piece, the Sun was formed. This piece rotated and warmed up. It became like a disc. From dense particles on the periphery of this gas-dust cloud, planets were formed, including our Earth. Meanwhile, in the center of the nascent star, under the influence of high temperatures and enormous pressure,

There is a hypothesis that arose during the search for exoplanets (similar to Earth) that the more heavy elements a star has, the less likely it is that life will arise near it. This is due to the fact that their large content leads to the appearance of gas giants around the star - objects like Jupiter. And such giants inevitably move towards the star and push small planets out of their orbits.

Date of Birth

The Earth was formed about four and a half billion years ago. The pieces rotating around the red-hot disk became heavier and heavier. It is assumed that initially their particles were attracted due to electric forces. And at some stage, when the mass of this “coma” reached a certain level, it began to attract everything in the area with the help of gravity.

As in the case of the Sun, the clot began to shrink and heat up. The substance is completely melted. Over time, a heavier center formed, consisting mainly of metals. When the Earth was formed, it began to slowly cool, and the crust formed from lighter substances.

clash

And then the Moon appeared, but not the way the Earth was formed, again, according to the assumption of scientists and according to the minerals found on our satellite. The Earth, having already cooled down, collided with a slightly smaller other planet. As a result, both objects completely melted and turned into one. And the substance thrown out by the explosion began to rotate around the Earth. It was from this that the moon was born. It is claimed that the minerals found on the satellite differ from those of the earth in their structure: as if the substance was melted and solidified again. But the same thing happened to our planet. And why didn't this terrible collision lead to the complete destruction of two objects with the formation of small fragments? There are many mysteries.

path to life

Then the Earth began to cool again. Again, a metal core formed, and then a thin surface layer. And between them - a relatively mobile substance - the mantle. Thanks to strong volcanic activity, the atmosphere of the planet was formed.

Initially, of course, it was absolutely unsuitable for human breathing. And life would be impossible without the appearance of liquid water. It is assumed that the latter was brought to our planet by billions of meteorites from the outskirts of the solar system. Apparently, some time after the formation of the Earth, there was a powerful bombardment, the cause of which could be the gravitational influence of Jupiter. Water was trapped inside minerals, and volcanoes turned it into steam, and it fell out to form oceans. Then came oxygen. According to many scientists, this happened due to the vital activity of ancient organisms that could appear in those harsh conditions. But that's a completely different story. And humanity every year is getting closer and closer to getting an answer to the question of how the planet Earth was formed.

The history of our planet still holds many mysteries. Scientists from various fields of natural science have contributed to the study of the development of life on Earth.

It is believed that the age of our planet is about 4.54 billion years. This entire time period is usually divided into two main stages: Phanerozoic and Precambrian. These stages are called eons or eonoteme. Eons, in turn, are divided into several periods, each of which is distinguished by a set of changes that have taken place in the geological, biological, atmospheric state of the planet.

1. Precambrian, or Cryptozoic- this is an eon (time interval of the development of the Earth), covering about 3.8 billion years. That is, the Precambrian is the development of the planet from the moment of formation, the formation of the earth's crust, the proto-ocean and the emergence of life on Earth. By the end of the Precambrian, highly organized organisms with a developed skeleton were already widespread on the planet.

The eon includes two more eonotemes - katarche and archaea. The latter, in turn, includes 4 eras.

1. Katarchaeus- this is the time of the formation of the Earth, but there was still neither the core nor the earth's crust. The planet was still a cold cosmic body. Scientists suggest that during this period there was already water on Earth. The Catarchean lasted about 600 million years.

2. Archaea covers a period of 1.5 billion years. During this period, there was no oxygen on Earth yet, deposits of sulfur, iron, graphite, and nickel were being formed. The hydrosphere and the atmosphere were a single vapor-gas shell that enveloped the globe in a dense cloud. The sun's rays practically did not penetrate through this veil, so darkness reigned on the planet. 2.1 2.1. Eoarchean- this is the first geological era, which lasted about 400 million years. The most important event of the Eoarchean is the formation of the hydrosphere. But there was still little water, the reservoirs existed separately from each other and did not yet merge into the world ocean. At the same time, the earth's crust becomes solid, although asteroids are still bombarding the Earth. At the end of the Eoarchean, the first supercontinent in the history of the planet, Vaalbara, is formed.

2.2 Paleoarchaean- the next era, which also lasted approximately 400 million years. During this period, the core of the Earth is formed, the magnetic field strength increases. A day on the planet lasted only 15 hours. But the oxygen content in the atmosphere increases due to the activity of bacteria that have appeared. The remains of these first forms of the Paleoarchean era of life have been found in Western Australia.

2.3 Mesoarchean also lasted about 400 million years. In the Mesoarchean era, our planet was covered by a shallow ocean. Land areas were small volcanic islands. But already during this period, the formation of the lithosphere begins and the mechanism of plate tectonics starts. At the end of the Mesoarchean, the first ice age occurs, during which snow and ice form for the first time on Earth. Biological species are still represented by bacteria and microbial life forms.

2.4 Neoarchean- the final era of the Archean eon, the duration of which is about 300 million years. Colonies of bacteria at this time form the first stromatolites (limestone deposits) on Earth. The most important event of the Neoarchean is the formation of oxygen photosynthesis.

II. Proterozoic- one of the longest time periods in the history of the Earth, which is usually divided into three eras. During the Proterozoic, the ozone layer first appears, the world ocean reaches almost its present volume. And after the longest Huron glaciation, the first multicellular life forms appeared on Earth - mushrooms and sponges. The Proterozoic is usually divided into three eras, each of which contained several periods.

3.1 Paleo-Proterozoic- the first era of the Proterozoic, which began 2.5 billion years ago. At this time, the lithosphere is fully formed. But the former forms of life, due to the increase in oxygen content, practically died out. This period is called the oxygen catastrophe. By the end of the era, the first eukaryotes appear on Earth.

3.2 Mesoproterozoic lasted approximately 600 million years. The most important events of this era: the formation of continental masses, the formation of the supercontinent Rodinia and the evolution of sexual reproduction.

3.3 Neo-proterozoic. During this era, Rodinia breaks up into about 8 parts, the super-ocean of Mirovia ceases to exist, and at the end of the era, the Earth is covered with ice almost to the equator. In the Neoproterozoic era, living organisms for the first time begin to acquire a hard shell, which will later serve as the basis of the skeleton.

III. Paleozoic- the first era of the Phanerozoic eon, which began approximately 541 million years ago and lasted about 289 million years. This is the era of the emergence of ancient life. The supercontinent Gondwana unites the southern continents, a little later the rest of the land joins it and Pangea appears. Climatic zones begin to form, and flora and fauna are represented mainly by marine species. Only towards the end of the Paleozoic does the development of land begin, and the first vertebrates appear.

The Paleozoic era is conditionally divided into 6 periods.

1. Cambrian period lasted 56 million years. During this period, the main rocks are formed, the mineral skeleton appears in living organisms. And the most important event of the Cambrian is the appearance of the first arthropods.

2. Ordovician period- the second period of the Paleozoic, which lasted 42 million years. This is the era of the formation of sedimentary rocks, phosphorites and oil shale. The organic world of the Ordovician is represented by marine invertebrates and blue-green algae.

3. Silurian period covers the next 24 million years. At this time, almost 60% of living organisms that existed before die out. But the first cartilaginous and bone fish in the history of the planet appear. On land, the Silurian is marked by the appearance of vascular plants. Supercontinents converge and form Laurasia. By the end of the period, ice melting was noted, the sea level rose, and the climate became milder.

4 Devonian is characterized by the rapid development of various forms of life and the development of new ecological niches. Devon covers a time interval of 60 million years. The first terrestrial vertebrates, spiders, and insects appear. Land animals develop lungs. Although fish still dominate. The kingdom of flora of this period is represented by ferns, horsetails, club mosses and gosperms.

5. Carboniferous period often referred to as carbon. At this time, Laurasia collides with Gondwana and the new supercontinent Pangea appears. A new ocean is also formed - Tethys. This is the time when the first amphibians and reptiles appeared.

6. Permian period- the last period of the Paleozoic, which ended 252 million years ago. It is believed that at this time a large asteroid fell to Earth, which led to significant climate change and the extinction of almost 90% of all living organisms. Most of the land is covered with sand, the most extensive deserts appear that have only existed in the entire history of the Earth's development.

IV. Mesozoic- the second era of the Phanerozoic eon, which lasted almost 186 million years. At this time, the continents acquire almost modern outlines. A warm climate contributes to the rapid development of life on Earth. Giant ferns disappear, and angiosperms appear to replace them. The Mesozoic is the era of dinosaurs and the appearance of the first mammals.

The Mesozoic era is divided into three periods: Triassic, Jurassic and Cretaceous.

1. Triassic period lasted a little over 50 million years. At this time, Pangea begins to split, and the inland seas gradually become smaller and dry up. The climate is mild, the zones are not pronounced. Nearly half of land plants are disappearing as deserts spread. And in the realm of fauna, the first warm-blooded and terrestrial reptiles appear, which became the ancestors of dinosaurs and birds.

2 Jurassic covers a gap of 56 million years. A humid and warm climate reigned on Earth. The land is covered with thickets of ferns, pines, palms, cypresses. Dinosaurs reign on the planet, and numerous mammals have so far been distinguished by their small stature and thick hair.

3 Cretaceous- the longest period of the Mesozoic, lasting almost 79 million years. The split of the continents is practically coming to an end, the Atlantic Ocean is significantly increasing in volume, and ice sheets are forming at the poles. An increase in the water mass of the oceans leads to the formation of a greenhouse effect. At the end of the Cretaceous, a catastrophe occurs, the causes of which are still not clear. As a result, all dinosaurs and most species of reptiles and gymnosperms became extinct.

V. Cenozoic- this is the era of animals and Homo sapiens, which began 66 million years ago. The continents at this time acquired their modern shape, Antarctica occupied the south pole of the Earth, and the oceans continued to grow. Plants and animals that survived the catastrophe of the Cretaceous period found themselves in a completely new world. Unique communities of lifeforms began to form on each continent.

The Cenozoic era is divided into three periods: Paleogene, Neogene and Quaternary.

1. Paleogene period ended approximately 23 million years ago. At that time, a tropical climate reigned on Earth, Europe was hiding under evergreen tropical forests, and deciduous trees grew only in the north of the continents. It was during the Paleogene period that the rapid development of mammals takes place.

2. Neogene period covers the next 20 million years of the planet's development. Whales and bats appear. And, although saber-toothed tigers and mastodons still roam the earth, the fauna is increasingly acquiring modern features.

3. Quaternary period began more than 2.5 million years ago and continues to this day. Two major events characterize this time period: the Ice Age and the advent of man. The Ice Age completely completed the formation of the climate, flora and fauna of the continents. And the appearance of man marked the beginning of civilization.

So we got to our planet.

How did the earth actually form? So far, we, the people living on this planet, are not ready to talk about it. We can measure and understand the size of the oceans and continents on our planet, how much time it takes to fly somewhere by plane. Yes, we have some idea about the planet of the solar system - the Earth, although far from complete. The same questions arise - when, where and for what purposes?

I have already expressed the hypothesis earlier that our planet Earth may have been in a different constellation and was a satellite of a completely different star (a source of thermal radiation). It was inhabited and humanoid and other creatures of gigantic size existed on it. Why giant? This is due to only one factor, which luminary and what energy it gives, that is, the closer to the source of magnetic energy, the larger the size of the flora and fauna will be. And of course, again there is a dependence on the state of the planet itself, or rather its atmosphere.

Therefore, all the found skeletons of 10-20 meter people and various pangolins belonged to a different era of life on Earth and not under our Sunshine. It is difficult to say what kind of civilization they had. At some point (apparently, there were good reasons for this) something terrible happened to this planet and all living beings were doomed to death. After that, this planet could turn into just a large meteorite. But in view of the fact that this planet was unique in its internal reserves, kind super beings decided to preserve it.

To do this, they created a new magnetic star, our Sun (possibly on the outskirts of the Universe) and moved our planet to this place. Personally, I do not see anything supernatural in this. Simply for this, it was necessary to install magnetic installations on the planet, which could create a traction acceleration in the designated direction. Of course, it was necessary to constantly correct this direction. Approximately such a spotter could be a small planet, which we now call the Moon. We humans don't have that kind of opportunity. And for super beings, this is the relocation of the planet according to difficulty, perhaps the same as we overtake heavy vehicles, for example, across the Sahara desert. Maybe the example is not very successful, but again we do not know the development of the technical mind of aliens.

Then it is possible to somehow explain the existence of a long ice age on our planet. Imagine a long journey through dark and cold space, and after that, a long thawing of the planet. Even those who remained on the planet at that moment were subject to sudden freezing and their bodies, like the entire surface of the planet, were covered with a multi-meter layer of ice. And this happened not for a hundred or 50 years, but more.

You can object to such a hypothesis, but no one can refute it either.

And of course, the next point of intelligent beings, after the installation of the planet in the orbit of the Sun, is a new creation of life on the planet. But how to revive an extinct planet and create life anew?

In our humanity, there was only one justification for the formation of planet Earth - this is a gradual collision of solid space objects and gases, which, during a long period of various reactions, formed our planet. I also can not refute this, although I think it is stupidity. I just can’t understand - small asteroids fought, destroyed and fought again. As soon as a small ball was created, it is again destroyed by arriving asteroids. But then, let me ask you, who and how kindled the “bonfire” in the center of the planet, so that it would become warm, and later, from this warmth, our earthly atmosphere was created? As you understand, that only our Sun alone would not be able to do it.

Have you ever wondered where the incomprehensible magma came from, why it has such huge temperatures, while our Earth does not warm up and even freezes in places? What is this magma core for? Many questions come up again.

After a general review, let me express my hypothesis about the formation of our beloved planet. Our planet Earth, has been moved in outer space.

"Traditional" structure of the Earth

At the same time, the necessary conditions have already been created, i.e. our Sun was originally made. After moving, our planet of the ball is “placed” in the desired orbit in relation to the Sun. Now, it had to be heated from the inside in order to create life on this planet.

Again, without knowledge of chemistry and physics, which is super incomprehensible to us, this is not possible.

Let's turn to simple school physics. Just compare all the lines coming from two permanent magnets. Is there any difference between such lines of our Earth and laboratory magnets. As you can see, none. All lines go from S to N. And then return along arcs. These are our laws, and dogma for us in the field of permanent magnets.

It turns out that the same permanent magnets or magnetic installations are located in the center of our planet. Then it turns out that someone dug through our planet from the side of the poles and specially installed such magnets (magnetic installations). It is very difficult to do this, according to our concepts, but it is quite easy to do this for rational beings. With such knowledge in the technical field, there will not be much work.

Having launched such magnetic installations, it was along the axis of our globe from two sides that intelligent beings made a through tunnel. And then, with the help of the same two magnetic devices, by directing the rays of magnetic energy towards each other (with different swirls of magnetic spirals), they created a reaction (as we understand thermonuclear), which has been working for many centuries. Believe me, I can imagine the power of such installations, it's elementary. Just turn to the media again. According to them, huge round openings were found on the surface of our planet, which were made not a hundred years ago, but already in our time. It's just that these sentient beings are asking to believe it's possible. And what tunnels inside the planet can do, we don’t even guess.

We, mankind, have not yet begun to explore the internal cavities of our planet. For now, just drill it from all sides. I can even assume that the intelligent beings who produced us have already taken care of the worst consequences that can occur on the surface (the extinction of the sun, thermonuclear and various wars on the planet). Or maybe there, in the bowels of the Earth, there are already huge underground galleries, where further residence of earthly humanity is possible.

How was the Earth born?

There are several theories of the origin of our planet at once, each of which has its supporters and its right to life. Of course, it is impossible to determine exactly which of the theories actually describes the appearance of the Earth and whether such a theory exists at all, but in this article we will consider each of them in detail. The question of the origin of the Earth is still not fully understood and does not have an absolutely accurate answer.

Modern idea of ​​the origin of the planet Earth

To date, the most recognized theory of the origin of the planet Earth is the theory according to which the Earth was formed from the gas and dust matter scattered in the solar system.

According to this theory, the Sun appeared before the planets, and the Earth, like other planets in the solar system, was born from the debris, gas and dust left after the formation of the Sun. Thus, it is believed that the Earth was formed approximately 4.5 billion years ago, and the process of its formation took approximately 10 - 20 million years.

History of the development of the theory

The first to put forward this theory in 1755 was the German philosopher I. Kant. He believed that the Sun and the planets of the solar system originated from dust and gas that was dispersed in space. Particles of dust and gas under the influence of the shock wave from the Big Bang randomly moved, collided with each other, transferring energy. Thus, the heaviest and largest particles were formed, which were attracted to each other and eventually formed the Sun. After the Sun acquired a large size, smaller particles began to rotate around it, the paths of which intersected. Thus, gaseous rings were formed, in which light particles were attracted to heavier nuclei, creating globular clusters, which became future planets.

There are other theories about the origin of the Earth, which at different times were put forward by different scientists and even had their followers in the future.

Tidal theory of the origin of the Earth

According to this theory, the Sun appeared much earlier than the planets, and the Earth and other planets of the solar system were formed from substances released by the Sun or another large star.

History of the development of the theory

The history of this theory began in 1776, when the mathematician J. Buffon put forward the theory of the collision of the sun with a comet. As a result of this collision, the material from which both the planet Earth and other planets were born was released.

This theory found its follower in the 20th century. It was then that the scientist astrophysicist I.I. Wulfson, using computer calculations, showed that a star does not have to collide with the Sun in order to detach material. According to his theory, any large and cold star from a new cluster of stars could approach the Sun at a small distance and thereby cause giant tides both on its surface and on the Sun. The amplitude of these tides increases until the material breaks away from the Sun or an approaching star and takes place between these stellar bodies in the form of a cigar-shaped jet. Then the cold star leaves, and the emerging jet scatters into the planets of the solar system.

How the Earth was born according to the "nebular theory"

The creator of the first nebular theory was the French astronomer and mathematician P.-S. Laplace. He believed that there was some kind of gas disk rotating from compression; the speed of its rotation increased until the centrifugal force at its edge began to exceed the gravitational force of attraction. After that, the disk was torn, and after a while this process was repeated. Thus, the rings turned into planets, and the central mass into the Sun.

This theory explains well the fact that the Earth and the Sun rotate in the same plane and in the same direction, but it also has significant gaps.

According to this theory, the Sun must rotate very quickly (with a rotation period of several hours). However, in reality, the Sun rotates much more slowly - 1 revolution in 27 days. Another shortcoming of the theory is the mechanism for collecting particles into planets. The theory does not answer the question of why the substances after the rupture of the disk were divided into rings, and did not take the form of the same disk, but smaller.

This is where we end the story about the origin of planet Earth and recommend that you read about.

Earth is the third planet from the Sun and the fifth largest among all the planets in the solar system. It is also the largest in diameter, mass and density among the terrestrial planets.

Sometimes referred to as the World, the Blue Planet, sometimes Terra (from lat. Terra). The only known to man at the moment is the body of the solar system in particular and the universe in general, inhabited by living organisms.

Scientific evidence indicates that the Earth formed from the solar nebula about 4.54 billion years ago, and shortly thereafter acquired its only natural satellite, the Moon. Life appeared on Earth about 3.5 billion years ago, that is, within 1 billion after its occurrence. Since then, the Earth's biosphere has significantly changed the atmosphere and other abiotic factors, causing the quantitative growth of aerobic organisms, as well as the formation of the ozone layer, which, together with the Earth's magnetic field, weakens solar radiation harmful to life, thereby preserving the conditions for the existence of life on Earth.

Radiation, caused by the earth's crust itself, has significantly decreased since its formation due to the gradual decay of radionuclides in it. The Earth's crust is divided into several segments, or tectonic plates, that move across the surface at speeds of the order of a few centimeters per year. Approximately 70.8% of the planet's surface is occupied by the World Ocean, the rest of the surface is occupied by continents and islands. On the continents there are rivers and lakes, together with the World Ocean they make up the hydrosphere. Liquid water, essential for all known life forms, does not exist on the surface of any of the known planets and planetoids of the Solar System, except Earth. The Earth's poles are covered by an ice shell, which includes Arctic sea ice and the Antarctic ice sheet.

Earth's inner regions are quite active and consist of a thick, highly viscous layer called the mantle, which covers a liquid outer core, which is the source of the Earth's magnetic field, and a solid inner core, presumably composed of iron and nickel. The physical characteristics of the Earth and its orbital motion have allowed life to persist over the past 3.5 billion years. According to various estimates, the Earth will retain the conditions for the existence of living organisms for another 0.5 - 2.3 billion years.

The Earth interacts (is attracted by gravitational forces) with other objects in space, including the Sun and Moon. The Earth revolves around the Sun and makes a complete revolution around it in about 365.26 solar days - a sidereal year. The Earth's axis of rotation is inclined at 23.44° relative to the perpendicular to its orbital plane, which causes seasonal changes on the planet's surface with a period of one tropical year - 365.24 solar days. A day is now about 24 hours long. The Moon began its orbit around the Earth approximately 4.53 billion years ago. The gravitational influence of the Moon on the Earth is the cause of ocean tides. The moon also stabilizes the tilt of the earth's axis and gradually slows down the rotation of the earth. Some theories suggest that asteroid impacts led to significant changes in the environment and the surface of the Earth, causing, in particular, mass extinctions of various species of living beings.

The planet is home to millions of species of living beings, including humans. The territory of the Earth is divided into 195 independent states that interact with each other through diplomatic relations, travel, trade or military actions. Human culture has formed many ideas about the structure of the universe - such as the concept of a flat Earth, the geocentric system of the world and the Gaia hypothesis, according to which the Earth is a single superorganism.

History of the Earth

The modern scientific hypothesis of the formation of the Earth and other planets of the solar system is the solar nebula hypothesis, according to which the solar system was formed from a large cloud of interstellar dust and gas. The cloud consisted mainly of hydrogen and helium, which were formed after the Big Bang and heavier elements left behind by supernova explosions. Approximately 4.5 billion years ago, the cloud began to shrink, which was probably due to the impact of a shock wave from a supernova that broke out at a distance of several light years. As the cloud began to contract, its angular momentum, gravity and inertia flattened it into a protoplanetary disk perpendicular to its axis of rotation. After that, the fragments in the protoplanetary disk began to collide under the action of gravity, and, merging, formed the first planetoids.

In the process of accretion, planetoids, dust, gas, and debris left over from the formation of the solar system began to merge into ever larger objects, forming planets. The approximate date of the formation of the Earth is 4.54±0.04 billion years ago. The entire process of planet formation took approximately 10-20 million years.

The moon formed later, approximately 4.527 ± 0.01 billion years ago, although its origin has not yet been precisely established. The main hypothesis says that it was formed by accretion from the material left after the tangential collision of the Earth with an object similar in size to Mars and with a mass of 10% of the Earth (sometimes this object is called "Theia"). This collision released about 100 million times more energy than the one that caused the extinction of the dinosaurs. This was enough to evaporate the outer layers of the Earth and melt both bodies. Part of the mantle was ejected into Earth's orbit, which predicts why the Moon is devoid of metallic material and explains its unusual composition. Under the influence of its own gravity, the ejected material took on a spherical shape and the Moon was formed.

The proto-Earth expanded by accretion, and was hot enough to melt metals and minerals. Iron, as well as siderophile elements geochemically related to it, having a higher density than silicates and aluminosilicates, descended towards the center of the Earth. This led to the separation of the Earth's inner layers into a mantle and a metallic core just 10 million years after the Earth began to form, producing the Earth's layered structure and forming the Earth's magnetic field. The release of gases from the crust and volcanic activity led to the formation of the primary atmosphere. Condensation of water vapor, enhanced by ice brought by comets and asteroids, led to the formation of oceans. The Earth's atmosphere then consisted of light atmophilic elements: hydrogen and helium, but contained much more carbon dioxide than now, and this saved the oceans from freezing, since the luminosity of the Sun then did not exceed 70% of the current level. Approximately 3.5 billion years ago, the Earth's magnetic field formed, which prevented the devastation of the atmosphere by the solar wind.

The surface of the planet has been constantly changing for hundreds of millions of years: continents have appeared and collapsed. They moved across the surface, sometimes gathering into a supercontinent. Around 750 million years ago, the earliest known supercontinent, Rodinia, began to break apart. Later, these parts united into Pannotia (600-540 million years ago), then into the last of the supercontinents - Pangea, which broke up 180 million years ago.

The emergence of life

There are a number of hypotheses for the origin of life on Earth. About 3.5-3.8 billion years ago, the “last universal common ancestor” appeared, from which all other living organisms subsequently descended.

The development of photosynthesis allowed living organisms to use solar energy directly. This led to the oxygenation of the atmosphere, which began about 2500 million years ago, and in the upper layers - to the formation of the ozone layer. The symbiosis of small cells with larger ones led to the development of complex cells - eukaryotes. Approximately 2.1 billion years ago, multicellular organisms appeared that continued to adapt to environmental conditions. Thanks to the absorption of harmful ultraviolet radiation by the ozone layer, life was able to begin the development of the Earth's surface.

In 1960, the Snowball Earth hypothesis was put forward, stating that between 750 and 580 million years ago, the Earth was completely covered in ice. This hypothesis explains the Cambrian explosion - a sharp increase in the diversity of multicellular life forms about 542 million years ago.

About 1200 million years ago, the first algae appeared, and about 450 million years ago, the first higher plants appeared. Invertebrates appeared in the Ediacaran period, and vertebrates appeared during the Cambrian explosion about 525 million years ago.

There have been five mass extinctions since the Cambrian Explosion. The extinction at the end of the Permian period, which is the most massive in the history of life on Earth, led to the death of more than 90% of living beings on the planet. After the Permian catastrophe, archosaurs became the most common terrestrial vertebrates, from which dinosaurs descended at the end of the Triassic period. They dominated the planet during the Jurassic and Cretaceous periods. 65 million years ago there was a Cretaceous-Paleogene extinction, probably caused by a meteorite fall; it led to the extinction of dinosaurs and other large reptiles, but bypassed many small animals, such as mammals, which were then small insectivorous animals, and birds, an evolutionary branch of the dinosaurs. Over the past 65 million years, a huge variety of mammalian species has evolved, and several million years ago, ape-like animals acquired the ability to walk upright. This enabled the use of tools and promoted communication, which aided in foraging for food and stimulated the need for a large brain. The development of agriculture, and then civilization, in a short time allowed people to influence the Earth like no other form of life, to influence the nature and number of other species.

The last ice age began about 40 million years ago and peaked in the Pleistocene about 3 million years ago. Against the background of long and significant changes in the average temperature of the earth's surface, which may be associated with the period of revolution of the solar system around the center of the Galaxy (about 200 million years), there are also smaller cycles of cooling and warming in amplitude and duration that occur every 40-100 thousand years , which are clearly self-oscillating in nature, possibly caused by the action of feedback from the reaction of the entire biosphere as a whole, seeking to stabilize the Earth's climate (see the Gaia hypothesis put forward by James Lovelock, as well as the theory of biotic regulation proposed by V. G. Gorshkov).

The last cycle of glaciation in the Northern Hemisphere ended about 10,000 years ago.

Earth structure

According to the theory of tectonic plates, the outer part of the Earth consists of two layers: the lithosphere, which includes the earth's crust, and the hardened upper part of the mantle. Under the lithosphere is the asthenosphere, which makes up the outer part of the mantle. The asthenosphere behaves like an overheated and extremely viscous fluid.

The lithosphere is divided into tectonic plates, and, as it were, floats on the asthenosphere. Plates are rigid segments that move relative to each other. There are three types of their mutual movement: convergence (convergence), divergence (divergence) and shear movements along transform faults. On faults between tectonic plates, earthquakes, volcanic activity, mountain building, and the formation of ocean depressions can occur.

A list of the largest tectonic plates with sizes is given in the table on the right. Among the smaller plates, the Hindustanian, Arabian, Caribbean, Nazca and Scotia plates should be noted. The Australian plate actually merged with the Hindustan between 50 and 55 million years ago. Oceanic plates move the fastest; Thus, the Cocos plate moves at a speed of 75 mm per year, and the Pacific plate at a speed of 52-69 mm per year. The lowest speed is at the Eurasian plate - 21 mm per year.

Geographic envelope

The near-surface parts of the planet (the upper part of the lithosphere, the hydrosphere, the lower layers of the atmosphere) are generally called the geographical envelope and are studied by geography.

The relief of the Earth is very diverse. About 70.8% of the planet's surface is covered with water (including the continental shelves). The underwater surface is mountainous, includes a system of mid-ocean ridges, as well as underwater volcanoes, oceanic trenches, submarine canyons, oceanic plateaus and abyssal plains. The remaining 29.2%, not covered by water, includes mountains, deserts, plains, plateaus, etc.

During geological periods, the surface of the planet is constantly changing due to tectonic processes and erosion. The relief of tectonic plates is formed under the influence of weathering, which is a consequence of precipitation, temperature fluctuations, and chemical influences. Change the earth's surface and glaciers, coastal erosion, the formation of coral reefs, collisions with large meteorites.

As continental plates move across the planet, the ocean floor sinks under their advancing edges. At the same time, mantle matter rising from the depths creates a divergent boundary at mid-ocean ridges. Together, these two processes lead to a constant renewal of the material of the oceanic plate. Most of the ocean floor is less than 100 million years old. The oldest oceanic crust is located in the western part of the Pacific Ocean, and its age is approximately 200 million years. For comparison, the age of the oldest fossils found on land reaches about 3 billion years.

Continental plates are composed of low density material such as volcanic granite and andesite. Less common is basalt - a dense volcanic rock that is the main component of the ocean floor. Approximately 75% of the surface of the continents is covered with sedimentary rocks, although these rocks make up approximately 5% of the earth's crust. The third most common rocks on Earth are metamorphic rocks, formed as a result of the transformation (metamorphism) of sedimentary or igneous rocks under the influence of high pressure, high temperature, or both. The most common silicates on the Earth's surface are quartz, feldspar, amphibole, mica, pyroxene, and olivine; carbonates - calcite (in limestone), aragonite and dolomite.

The pedosphere, the topmost layer of the lithosphere, includes the soil. It is located on the border between the lithosphere, atmosphere, hydrosphere. Today, the total area of ​​cultivated land is 13.31% of the land surface, of which only 4.71% is permanently occupied by crops. Approximately 40% of the earth's land area today is used for arable land and pastures, which is approximately 1.3 x 107 km² of arable land and 3.4 x 107 km² of pasture.

Hydrosphere

Hydrosphere (from other Greek Yδωρ - water and σφαῖρα - ball) - the totality of all the water reserves of the Earth.

The presence of liquid water on the Earth's surface is a unique property that distinguishes our planet from other objects in the solar system. Most of the water is concentrated in the oceans and seas, much less - in river networks, lakes, swamps and groundwater. There are also large reserves of water in the atmosphere, in the form of clouds and water vapor.

Part of the water is in a solid state in the form of glaciers, snow cover and permafrost, making up the cryosphere.

The total mass of water in the World Ocean is approximately 1.35 1018 tons, or about 1/4400 of the total mass of the Earth. The oceans cover an area of ​​about 3.618 108 km2 with an average depth of 3682 m, which makes it possible to calculate the total volume of water in them: 1.332 109 km3. If all this water was evenly distributed over the surface, then a layer would be obtained, more than 2.7 km thick. Of all the water that is on Earth, only 2.5% is fresh, the rest is salty. Most of the fresh water, about 68.7%, is currently in glaciers. Liquid water appeared on Earth probably about four billion years ago.

The average salinity of the earth's oceans is about 35 grams of salt per kilogram of sea water (35 ‰). Much of this salt was released in volcanic eruptions or extracted from the cooled igneous rocks that formed the ocean floor.

Earth's atmosphere

Atmosphere - the gaseous shell that surrounds the planet Earth; It is composed of nitrogen and oxygen, with trace amounts of water vapor, carbon dioxide and other gases. Since its formation, it has changed significantly under the influence of the biosphere. The emergence of oxygenic photosynthesis 2.4-2.5 billion years ago contributed to the development of aerobic organisms, as well as the saturation of the atmosphere with oxygen and the formation of the ozone layer, which protects all living things from harmful ultraviolet rays. The atmosphere determines the weather on the Earth's surface, protects the planet from cosmic rays, and partly from meteorite bombardments. It also regulates the main climate-forming processes: the water cycle in nature, the circulation of air masses, and heat transfer. Atmospheric molecules can capture thermal energy, preventing it from escaping into outer space, thereby raising the temperature of the planet. This phenomenon is known as the greenhouse effect. The main greenhouse gases are considered to be water vapour, carbon dioxide, methane and ozone. Without this thermal insulation effect, the average surface temperature of the Earth would be between minus 18 and minus 23 °C, although in reality it is 14.8 °C, and life would most likely not exist.

The Earth's atmosphere is divided into layers that differ in temperature, density, chemical composition, etc. The total mass of gases that make up the Earth's atmosphere is approximately 5.15 1018 kg. At sea level, the atmosphere exerts a pressure of 1 atm (101.325 kPa) on the Earth's surface. The average air density at the surface is 1.22 g/l, and it rapidly decreases with increasing altitude: for example, at an altitude of 10 km above sea level it is no more than 0.41 g/l, and at an altitude of 100 km it is 10−7 g/l.

The lower part of the atmosphere contains about 80% of its total mass and 99% of all water vapor (1.3-1.5 1013 tons), this layer is called the troposphere. Its thickness varies and depends on the type of climate and seasonal factors: for example, in the polar regions it is about 8-10 km, in the temperate zone up to 10-12 km, and in tropical or equatorial regions it reaches 16-18 km. In this layer of the atmosphere, the temperature drops by an average of 6 ° C for every kilometer as you move up. Above is a transitional layer - the tropopause, which separates the troposphere from the stratosphere. The temperature here is in the range of 190-220 K.

Stratosphere - a layer of the atmosphere, which is located at an altitude of 10-12 to 55 km (depending on weather conditions and seasons). It accounts for no more than 20% of the total mass of the atmosphere. This layer is characterized by a decrease in temperature to a height of ~25 km, followed by an increase at the boundary with the mesosphere to almost 0 °C. This boundary is called the stratopause and is located at an altitude of 47-52 km. The stratosphere contains the highest concentration of ozone in the atmosphere, which protects all living organisms on Earth from harmful ultraviolet radiation from the Sun. Intensive absorption of solar radiation by the ozone layer causes a rapid increase in temperature in this part of the atmosphere.

The mesosphere is located at an altitude of 50 to 80 km above the Earth's surface, between the stratosphere and the thermosphere. It is separated from these layers by the mesopause (80-90 km). This is the coldest place on Earth, the temperature here drops to -100 °C. At this temperature, the water contained in the air quickly freezes, forming noctilucent clouds. They can be observed immediately after sunset, but the best visibility is created when it is from 4 to 16 ° below the horizon. Most of the meteorites that enter the earth's atmosphere burn up in the mesosphere. From the surface of the Earth, they are observed as shooting stars. At an altitude of 100 km above sea level, there is a conditional boundary between the earth's atmosphere and space - the Karman line.

In the thermosphere, the temperature quickly rises to 1000 K, this is due to the absorption of short-wave solar radiation in it. This is the longest layer of the atmosphere (80-1000 km). At an altitude of about 800 km, the temperature rise stops, because the air here is very rarefied and weakly absorbs solar radiation.

The ionosphere includes the last two layers. Molecules are ionized here under the action of the solar wind and auroras occur.

The exosphere is the outermost and very rarefied part of the earth's atmosphere. In this layer, particles are able to overcome the second cosmic velocity of the Earth and escape into outer space. This causes a slow but steady process called dissipation (scattering) of the atmosphere. It is mainly particles of light gases that escape into space: hydrogen and helium. Hydrogen molecules, which have the lowest molecular weight, can more easily reach escape velocity and escape into space at a faster rate than other gases. It is believed that the loss of reducing agents, such as hydrogen, was a necessary condition for the possibility of a sustainable accumulation of oxygen in the atmosphere. Therefore, the ability of hydrogen to leave the Earth's atmosphere may have influenced the development of life on the planet. Currently, most of the hydrogen that enters the atmosphere is converted to water without leaving the Earth, and the loss of hydrogen occurs mainly from the destruction of methane in the upper atmosphere.

The chemical composition of the atmosphere

At the surface of the Earth, the air contains up to 78.08% nitrogen (by volume), 20.95% oxygen, 0.93% argon, and about 0.03% carbon dioxide. The remaining components account for no more than 0.1%: these are hydrogen, methane, carbon monoxide, sulfur and nitrogen oxides, water vapor, and inert gases. Depending on the season, climate and terrain, the atmosphere may include dust, particles of organic materials, ash, soot, etc. Above 200 km, nitrogen becomes the main component of the atmosphere. At an altitude of 600 km, helium predominates, and from 2000 km - hydrogen ("hydrogen corona").

Weather and climate

The earth's atmosphere has no definite boundaries; it gradually becomes thinner and rarer, passing into outer space. Three quarters of the mass of the atmosphere is contained in the first 11 kilometers from the surface of the planet (the troposphere). Solar energy heats this layer near the surface, causing the air to expand and reduce its density. The heated air then rises and is replaced by colder, denser air. This is how the circulation of the atmosphere arises - a system of closed currents of air masses through the redistribution of thermal energy.

The basis of atmospheric circulation is the trade winds in the equatorial zone (below 30° latitude) and the westerly winds of the temperate zone (in latitudes between 30° and 60°). Sea currents are also important factors in shaping the climate, as is the thermohaline circulation, which distributes thermal energy from equatorial to polar regions.

Water vapor rising from the surface forms clouds in the atmosphere. When atmospheric conditions allow warm, moist air to rise, this water condenses and falls to the surface as rain, snow, or hail. Most of the precipitation that falls on land ends up in rivers, and eventually returns to the oceans or remains in lakes, and then evaporates again, repeating the cycle. This water cycle in nature is a vital factor for the existence of life on land. The amount of precipitation falling during the year is different, ranging from a few meters to a few millimeters, depending on the geographical location of the region. Atmospheric circulation, topological features of the area and temperature differences determine the average amount of precipitation that falls in each region.

The amount of solar energy reaching the Earth's surface decreases with increasing latitude. At higher latitudes, sunlight hits the surface at a sharper angle than at lower latitudes; and it must travel a longer path in the earth's atmosphere. As a result, the average annual air temperature (at sea level) decreases by about 0.4 °C when moving 1 degree on either side of the equator. The earth is divided into climatic zones - natural zones that have an approximately uniform climate. Climate types can be classified according to the temperature regime, the amount of winter and summer precipitation. The most common climate classification system is the Köppen classification, according to which the best criterion for determining the type of climate is what plants grow in a given area under natural conditions. The system includes five main climatic zones (moist tropical forests, deserts, temperate zone, continental climate and polar type), which in turn are divided into more specific subtypes.

Biosphere

The biosphere is a set of parts of the earth's shells (litho-, hydro- and atmosphere), which is inhabited by living organisms, is under their influence and is occupied by the products of their vital activity. The term "biosphere" was first proposed by the Austrian geologist and paleontologist Eduard Suess in 1875. The biosphere is the shell of the Earth inhabited by living organisms and transformed by them. It began to form no earlier than 3.8 billion years ago, when the first organisms began to emerge on our planet. It includes the entire hydrosphere, the upper part of the lithosphere and the lower part of the atmosphere, that is, it inhabits the ecosphere. The biosphere is the totality of all living organisms. It is home to over 3,000,000 species of plants, animals, fungi and microorganisms.

The biosphere consists of ecosystems, which include communities of living organisms (biocenosis), their habitats (biotope), systems of connections that exchange matter and energy between them. On land, they are separated mainly by geographical latitude, altitude and differences in precipitation. Terrestrial ecosystems located in the Arctic or Antarctic, at high altitudes or in extremely dry areas, are relatively poor in plants and animals; species diversity peaks in the equatorial rainforests.

Earth's magnetic field

The Earth's magnetic field in the first approximation is a dipole, the poles of which are located near the geographic poles of the planet. The field forms a magnetosphere that deflects solar wind particles. They accumulate in radiation belts - two concentric torus-shaped regions around the Earth. Near the magnetic poles, these particles can “fall out” into the atmosphere and lead to the appearance of auroras. At the equator, the Earth's magnetic field has an induction of 3.05·10-5 T and a magnetic moment of 7.91·1015 T·m3.

According to the "magnetic dynamo" theory, the field is generated in the central region of the Earth, where heat creates the flow of electric current in the liquid metal core. This in turn creates a magnetic field around the Earth. Convection motions in the core are chaotic; magnetic poles drift and periodically change their polarity. This causes reversals in the Earth's magnetic field, which occur, on average, several times every few million years. The last inversion occurred approximately 700,000 years ago.

Magnetosphere - a region of space around the Earth, which is formed when the stream of charged particles of the solar wind deviates from its original trajectory under the influence of a magnetic field. On the side facing the Sun, its bow shock is about 17 km thick and is located at a distance of about 90,000 km from the Earth. On the night side of the planet, the magnetosphere stretches out into a long cylindrical shape.

When high-energy charged particles collide with the Earth's magnetosphere, radiation belts (Van Allen belts) appear. Auroras occur when solar plasma reaches the Earth's atmosphere near the magnetic poles.

Orbit and rotation of the Earth

It takes the Earth an average of 23 hours 56 minutes and 4.091 seconds (a sidereal day) to complete one revolution around its axis. The rotation of the planet from west to east is approximately 15 degrees per hour (1 degree per 4 minutes, 15′ per minute). This is equivalent to the angular diameter of the Sun or Moon every two minutes (the apparent sizes of the Sun and Moon are about the same).

The rotation of the Earth is unstable: the speed of its rotation relative to the celestial sphere changes (in April and November, the length of the day differs from the reference ones by 0.001 s), the rotation axis precesses (by 20.1″ per year) and fluctuates (the distance of the instantaneous pole from the average does not exceed 15′ ). On a large time scale, it slows down. The duration of one revolution of the Earth has increased over the past 2000 years by an average of 0.0023 seconds per century (according to observations over the past 250 years, this increase is less - about 0.0014 seconds per 100 years). Due to tidal acceleration, on average, each day is ~29 nanoseconds longer than the previous one.

The period of rotation of the Earth relative to the fixed stars, in the International Earth Rotation Service (IERS), is 86164.098903691 seconds according to UT1 or 23 hours 56 minutes. 4.098903691 p.

The Earth moves around the Sun in an elliptical orbit at a distance of about 150 million km with an average speed of 29.765 km/sec. The speed ranges from 30.27 km/s (at perihelion) to 29.27 km/s (at aphelion). Moving in orbit, the Earth makes a complete revolution in 365.2564 mean solar days (one sidereal year). From Earth, the movement of the Sun relative to the stars is about 1° per day in an easterly direction. The speed of the Earth's movement in orbit is not constant: in July (during the passage of aphelion) it is minimal and is about 60 arc minutes per day, and when passing perihelion in January it is maximum, about 62 minutes per day. The sun and the entire solar system revolve around the center of the Milky Way galaxy in an almost circular orbit at a speed of about 220 km/s. In turn, the solar system as part of the Milky Way moves at a speed of about 20 km/s towards a point (apex) located on the border of the constellations Lyra and Hercules, accelerating as the universe expands.

The Moon revolves with the Earth around a common center of mass every 27.32 days relative to the stars. The time interval between two identical phases of the moon (synodic month) is 29.53059 days. Seen from the north celestial pole, the moon moves around the earth in a counterclockwise direction. In the same direction, the circulation of all the planets around the Sun, and the rotation of the Sun, Earth and Moon around their axis. The axis of rotation of the Earth is deflected from the perpendicular to the plane of its orbit by 23.5 degrees (the direction and angle of inclination of the Earth's axis changes due to precession, and the apparent elevation of the Sun depends on the time of year); the Moon's orbit is tilted 5 degrees relative to the Earth's orbit (without this tilt, there would be one solar and one lunar eclipse each month).

Due to the tilt of the Earth's axis, the height of the Sun above the horizon changes throughout the year. For an observer at northern latitudes in summer, when the North Pole is tilted toward the Sun, daylight hours last longer and the Sun is higher in the sky. This leads to higher average air temperatures. When the North Pole deviates away from the Sun, everything is reversed and the climate becomes colder. Beyond the Arctic Circle at this time there is a polar night, which at the latitude of the Arctic Circle lasts almost two days (the sun does not rise on the day of the winter solstice), reaching half a year at the North Pole.

These changes in climate (due to the tilt of the earth's axis) cause the seasons to change. The four seasons are determined by the solstices - the moments when the earth's axis is maximally tilted towards the Sun or away from the Sun - and the equinoxes. The winter solstice occurs around December 21st, the summer solstice around June 21st, the spring equinox around March 20th, and the autumn equinox around September 23rd. When the North Pole is tilted towards the Sun, the South Pole is tilted away from it. Thus, when it is summer in the northern hemisphere, it is winter in the southern hemisphere, and vice versa (although the months are named the same, that is, for example, February in the northern hemisphere is the last (and coldest) month of winter, and in the southern hemisphere - the last (and warmest ) month of summer).

The tilt angle of the earth's axis is relatively constant for a long time. However, it undergoes minor shifts (known as nutation) at intervals of 18.6 years. There are also long-term fluctuations (about 41,000 years) known as Milankovitch cycles. The orientation of the Earth's axis also changes with time, the duration of the precession period is 25,000 years; this precession is the cause of the difference between the sidereal year and the tropical year. Both of these motions are caused by the changing attraction exerted by the Sun and Moon on the Earth's equatorial bulge. The poles of the Earth move relative to its surface by several meters. This movement of the poles has a variety of cyclical components, which together are called quasi-periodic motion. In addition to the annual components of this movement, there is a 14-month cycle called the Chandler movement of the Earth's poles. The speed of rotation of the Earth is also not constant, which is reflected in the change in the length of the day.

The Earth is currently going through perihelion around January 3rd and aphelion around July 4th. The amount of solar energy reaching the Earth at perihelion is 6.9% more than at aphelion, since the distance from the Earth to the Sun at aphelion is 3.4% greater. This is due to the inverse square law. Since the southern hemisphere is tilted towards the sun at about the same time that the Earth is closest to the sun, it receives slightly more solar energy during the year than the northern hemisphere. However, this effect is much less significant than the change in total energy due to the tilt of the earth's axis, and, in addition, most of the excess energy is absorbed by the large amount of water in the southern hemisphere.

For the Earth, the radius of the Hill sphere (the sphere of influence of the earth's gravity) is approximately 1.5 million km. This is the maximum distance at which the influence of the Earth's gravity is greater than the influence of the gravitations of other planets and the Sun.

Observation

The Earth was first photographed from space in 1959 by the Explorer 6. The first person to see the Earth from space was Yuri Gagarin in 1961. The crew of Apollo 8 in 1968 was the first to observe Earth rising from lunar orbit. In 1972, the crew of Apollo 17 took the famous picture of the Earth - "The Blue Marble".

From outer space and from the "outer" planets (located beyond the orbit of the Earth), one can observe the passage of the Earth through phases similar to those of the moon, just as an earthly observer can see the phases of Venus (discovered by Galileo Galilei).

Moon

The Moon is a relatively large planet-like satellite with a diameter equal to a quarter of Earth's. It is the largest, in relation to the size of its planet, satellite of the solar system. After the name of the earth's moon, the natural satellites of other planets are also called "moons".

The gravitational attraction between the Earth and the Moon is the cause of the earth's tides. A similar effect on the Moon is manifested in the fact that it constantly faces the Earth with the same side (the period of revolution of the Moon around its axis is equal to the period of its revolution around the Earth; see also tidal acceleration of the Moon). This is called tidal synchronization. During the revolution of the Moon around the Earth, the Sun illuminates various parts of the satellite's surface, which is manifested in the phenomenon of lunar phases: the dark part of the surface is separated from the light by a terminator.

Due to tidal synchronization, the Moon is moving away from the Earth by about 38 mm per year. In millions of years, this tiny change, as well as an increase in the Earth's day by 23 microseconds per year, will lead to significant changes. So, for example, in the Devonian (about 410 million years ago) there were 400 days in a year, and a day lasted 21.8 hours.

The moon can significantly affect the development of life by changing the climate on the planet. Paleontological findings and computer models show that the tilt of the earth's axis is stabilized by the tidal synchronization of the Earth with the Moon. If the Earth's axis of rotation approached the plane of the ecliptic, then as a result the climate on the planet would become extremely severe. One of the poles would point directly at the Sun, and the other would point in the opposite direction, and as the Earth revolves around the Sun, they would change places. The poles would point directly at the Sun in summer and winter. Planetologists who have studied this situation argue that in this case, all large animals and higher plants would have died out on Earth.

The angular size of the Moon as seen from Earth is very close to the apparent size of the Sun. The angular dimensions (and solid angle) of these two celestial bodies are similar, because although the diameter of the Sun is 400 times larger than the moon, it is 400 times farther from the Earth. Due to this circumstance and the presence of a significant eccentricity of the Moon's orbit, both total and annular eclipses can be observed on Earth.

The most common hypothesis for the origin of the Moon, the giant impact hypothesis, states that the Moon was formed as a result of the collision of the protoplanet Thei (roughly the size of Mars) with the proto-Earth. This, among other things, explains the reasons for the similarities and differences in the composition of the lunar soil and the earth.

At present, the Earth has no other natural satellites other than the Moon, however, there are at least two natural co-orbital satellites - asteroids 3753 Cruitney, 2002 AA29 and many artificial ones.

Asteroids approaching the Earth

The fall of large (several thousand km in diameter) asteroids to the Earth poses a danger of its destruction, however, all similar bodies observed in the modern era are too small for this, and their fall is dangerous only for the biosphere. According to popular hypotheses, such falls could cause several mass extinctions. Asteroids with perihelion distances less than or equal to 1.3 astronomical units that may within the foreseeable future approach Earth by less than or equal to 0.05 AU. i.e., are considered potentially dangerous objects. In total, about 6,200 objects have been registered that pass at a distance of up to 1.3 astronomical units from the Earth. The danger of their fall to the planet is regarded as negligible. According to modern estimates, collisions with such bodies (according to the most pessimistic forecasts) are unlikely to occur more often than once every hundred thousand years.

Geographic Information

Square

• Surface: 510.072 million km²
• Land: 148.94 million km² (29.1%)
• Water: 361.132 million km² (70.9%)

Coastline length: 356,000 km

Use of sushi

Data for 2011

• arable land - 10.43%
• perennial plantations - 1.15%
• other - 88.42%

Irrigated land: 3,096,621.45 km² (as of 2011)

Socio-economic geography

On October 31, 2011, the world's population reached 7 billion people. According to UN estimates, the world's population will reach 7.3 billion in 2013 and 9.2 billion in 2050. The bulk of population growth is expected to occur in developing countries. The average population density on land is about 40 people / km2, it varies greatly in different parts of the Earth, and it is highest in Asia. According to forecasts, by 2030 the level of urbanization of the population will reach 60%, while now it is 49% on average in the world.

Role in culture

The Russian word "land" goes back to Praslav. *zemja with the same meaning, which, in turn, continues the Proto-I.e. *dheĝhōm "earth".

In English, Earth is Earth. This word continues Old English eorthe and Middle English erthe. As the name of the planet Earth was first used around 1400. This is the only name of the planet that was not taken from Greco-Roman mythology.

The standard astronomical sign of the Earth is a cross outlined by a circle. This symbol has been used in various cultures for various purposes. Another version of the symbol is a cross on top of a circle (♁), a stylized orb; was used as an early astronomical symbol for the planet Earth.

In many cultures, the Earth is deified. She is associated with a goddess, a mother goddess, called Mother Earth, often depicted as a goddess of fertility.

The Aztecs called the Earth Tonantzin - "our mother". Among the Chinese, this is the goddess Hou-Tu (后土), similar to the Greek goddess of the Earth - Gaia. In Norse mythology, the Earth goddess Jord was the mother of Thor and the daughter of Annar. In ancient Egyptian mythology, unlike many other cultures, the Earth is identified with a man - the god Geb, and the sky with a woman - the goddess Nut.

In many religions, there are myths about the origin of the world, telling about the creation of the Earth by one or more deities.

In many ancient cultures, the Earth was considered flat, so, in the culture of Mesopotamia, the world was represented as a flat disk floating on the surface of the ocean. Assumptions about the spherical shape of the Earth were made by ancient Greek philosophers; This view was held by Pythagoras. In the Middle Ages, most Europeans believed that the Earth was spherical, as witnessed by thinkers such as Thomas Aquinas. Before the advent of space flight, judgments about the spherical shape of the Earth were based on the observation of secondary signs and on the similar shape of other planets.

Technological progress in the second half of the 20th century changed the general perception of the Earth. Before the beginning of space flights, the Earth was often depicted as a green world. Fantast Frank Paul may have been the first to depict a cloudless blue planet (with clearly defined land) on the back of the July issue of Amazing Stories in 1940.

In 1972, the crew of Apollo 17 took the famous photograph of the Earth, called "Blue Marble" (Blue Marble). An image of Earth taken in 1990 by Voyager 1 from a great distance from it prompted Carl Sagan to compare the planet to a pale blue dot (Pale Blue Dot). Also, the Earth was compared to a large spaceship with a life support system that needs to be maintained. The Earth's biosphere has sometimes been described as one large organism.

Ecology

In the last two centuries, a growing environmental movement has been concerned about the growing impact of human activities on the nature of the Earth. The key tasks of this socio-political movement are the protection of natural resources, the elimination of pollution. Conservationists advocate sustainable use of the planet's resources and environmental management. This, in their opinion, can be achieved by making changes in public policy and changing the individual attitude of each person. This is especially true for the large-scale use of non-renewable resources. The need to take into account the impact of production on the environment imposes additional costs, which leads to a conflict between commercial interests and the ideas of environmental movements.

Future of the Earth

The future of the planet is closely connected with the future of the Sun. As a result of the accumulation of “spent” helium in the core of the Sun, the luminosity of the star will begin to slowly increase. It will increase by 10% over the next 1.1 billion years, and as a result, the habitable zone of the solar system will shift beyond the current Earth orbit. According to some climate models, an increase in the amount of solar radiation falling on the Earth's surface will lead to catastrophic consequences, including the possibility of the complete evaporation of all oceans.

An increase in the temperature of the Earth's surface will accelerate the inorganic circulation of CO2, reducing its concentration to a lethal level for plants (10 ppm for C4 photosynthesis) in 500-900 million years. The disappearance of vegetation will lead to a decrease in the oxygen content in the atmosphere and life on Earth will become impossible in a few million years. In another billion years, water from the surface of the planet will completely disappear, and the average surface temperature will reach 70 ° C. Most of the land will become unsuitable for the existence of life, and it must first of all remain in the ocean. But even if the Sun were eternal and unchanging, then the continued internal cooling of the Earth could lead to the loss of most of the atmosphere and oceans (due to reduced volcanic activity). By that time, the only living creatures on Earth will be extremophiles, organisms that can withstand high temperatures and lack of water.

After 3.5 billion years from now, the luminosity of the Sun will increase by 40% compared to the current level. Conditions on the Earth's surface by that time will be similar to the surface conditions of modern Venus: the oceans will completely evaporate and evaporate into space, the surface will become a barren hot desert. This catastrophe will make it impossible for any life forms to exist on Earth. In 7.05 billion years, the solar core will run out of hydrogen. This will cause the Sun to exit the main sequence and enter the red giant stage. The model shows that it will increase in radius to a value equal to about 77.5% of the current radius of the Earth's orbit (0.775 AU), and its luminosity will increase by 2350-2700 times. However, by that time, the Earth's orbit may increase to 1.4 AU. That is, because the attraction of the Sun will weaken due to the fact that it will lose 28-33% of its mass due to the strengthening of the solar wind. However, studies in 2008 show that the Earth may still be absorbed by the Sun due to tidal interactions with its outer shell.

By then, the Earth's surface will be in a molten state as temperatures on Earth reach 1370°C. Earth's atmosphere is likely to be blown into outer space by the strongest solar wind emitted by a red giant. After 10 million years from the time the Sun enters the red giant phase, the temperature in the solar core will reach 100 million K, a helium flash will occur, and a thermonuclear reaction will begin to synthesize carbon and oxygen from helium, the Sun will decrease in radius to 9.5 modern. The stage of "burning helium" (Helium Burning Phase) will last 100-110 million years, after which the rapid expansion of the outer shells of the star will repeat, and it will again become a red giant. Having reached the asymptotic giant branch, the Sun will increase in diameter by 213 times. After 20 million years, a period of unstable pulsations of the surface of the star will begin. This phase of the existence of the Sun will be accompanied by powerful flares, at times its luminosity will exceed the current level by 5000 times. This will come from the fact that previously unaffected helium residues will enter into a thermonuclear reaction.

After about 75,000 years (according to other sources - 400,000), the Sun will shed its shells, and eventually only its small central core will remain from the red giant - a white dwarf, a small, hot, but very dense object, with a mass of about 54.1% from the original solar. If the Earth can avoid absorption by the outer shells of the Sun during the red giant phase, then it will exist for many more billions (and even trillions) of years, as long as the Universe exists, but the conditions for the re-emergence of life (at least in its current form) will not be on Earth. With the entry of the Sun into the phase of a white dwarf, the surface of the Earth will gradually cool down and plunge into darkness. If we imagine the size of the Sun from the surface of the Earth of the future, then it will look not like a disk, but like a shining point with an angular size of about 0°0’9″.

A black hole with a mass equal to Earth would have a Schwarzschild radius of 8 mm.

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