The structure of the earth. Why was the Earth called Earth? The history of the origin of the name of our planet The atmosphere and temperature of planet Earth

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 World, Blue Planet, sometimes Terra (from the Latin Terra). The only body currently known to man, the Solar System in particular and the Universe in general, inhabited by living organisms.

Scientific evidence indicates that the Earth formed from a 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 origin. Since then, the Earth's biosphere has significantly changed the atmosphere and other abiotic factors, causing a quantitative increase in 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 maintaining the conditions for the existence of life on Earth.

Radiation caused by the earth's crust itself has decreased significantly since its formation due to the gradual decay of radionuclides in it. The Earth's crust is divided into several segments, or tectonic plates, which move across the surface at speeds of the order of several 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. There are rivers and lakes on the continents; 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 known planets or planetoids in the Solar System other than Earth. The Earth's poles are covered by a shell of ice that includes Arctic sea ice and the Antarctic ice sheet.

The Earth's interior is quite active and consists 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 an inner solid 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 maintain conditions for the existence of living organisms for another 0.5 - 2.3 billion years.

The Earth interacts (is pulled 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 approximately 365.26 solar days - a sidereal year. The Earth's rotation axis is inclined by 23.44° relative to the perpendicular to its orbital plane, this causes seasonal changes on the surface of the planet with a period of one tropical year - 365.24 solar days. A day is now approximately 24 hours long. The Moon began its orbit around the Earth approximately 4.53 billion years ago. The Moon's gravitational effect on Earth causes ocean tides. The Moon also stabilizes the tilt of the Earth's axis and gradually slows down the Earth's rotation. Some theories suggest that asteroid impacts led to significant changes in the environment and the surface of the Earth, in particular causing 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, which interact with each other through diplomatic relations, travel, trade or military action. 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

A modern scientific hypothesis for 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 formed after the Big Bang, and heavier elements left behind by supernova explosions. About 4.5 billion years ago, the cloud began to shrink, likely due to the impact of a shock wave from a supernova that erupted several light-years away. 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 this, the debris in the protoplanetary disk began to collide under the influence of gravity and, merging, formed the first planetoids.

During 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 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 is that it was formed by accretion from material remaining after a tangential collision of the Earth with an object similar in size to Mars and 10% of Earth's mass (sometimes this object is called “Theia”). This collision released approximately 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. Some of the mantle was thrown 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 grew larger through 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, sank to 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 shaping the Earth's magnetic field. The release of gases from the crust and volcanic activity led to the formation of the primary atmosphere. The condensation of water vapor, enhanced by ice brought in 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 its current level. About 3.5 billion years ago, the Earth's magnetic field formed, which prevented the solar wind from ravaging the atmosphere.

The surface of the planet was constantly changing over hundreds of millions of years: continents appeared and collapsed. They moved across the surface, sometimes gathering into a supercontinent. About 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 oxygenation of the atmosphere, which began approximately 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. About 2.1 billion years ago, multicellular organisms appeared and continued to adapt to their surrounding conditions. Thanks to the absorption of harmful ultraviolet radiation by the ozone layer, life was able to begin developing the Earth's surface.

In 1960, the Snowball Earth hypothesis was put forward, arguing that between 750 and 580 million years ago the Earth was completely covered in ice. This hypothesis explains the Cambrian Explosion, a dramatic increase in the diversity of multicellular life forms around 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 during 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 end-Permian extinction event, the largest in the history of life on Earth, resulted in the death of more than 90% of living things on the planet. After the Permian disaster, archosaurs became the most common land vertebrates, from which dinosaurs evolved at the end of the Triassic period. They dominated the planet during the Jurassic and Cretaceous periods. The Cretaceous-Paleogene extinction event occurred 65 million years ago, probably caused by a meteorite impact; 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 dinosaurs. Over the past 65 million years, a huge variety of mammal species have evolved, and a few million years ago, ape-like animals gained the ability to walk upright. This allowed the use of tools and facilitated communication, which aided in obtaining 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 numbers 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-term 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 cycles of cooling and warming that are smaller in amplitude and duration, occurring every 40-100 thousand years , having a clearly self-oscillating nature, possibly caused by the action of feedback from the reaction of the entire biosphere as a whole, seeking to ensure stabilization of 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 glaciation cycle in the Northern Hemisphere ended about 10 thousand years ago.

Structure of the Earth

According to plate tectonic theory, the outer part of the Earth consists of two layers: the lithosphere, which includes the Earth's crust, and the solidified upper part of the mantle. Below the lithosphere is the asthenosphere, which makes up the outer part of the mantle. The asthenosphere behaves like a superheated and extremely viscous liquid.

The lithosphere is divided into tectonic plates, and seems to float on the asthenosphere. The plates are rigid segments that move relative to each other. There are three types of their mutual movement: convergence (convergence), divergence (divergence) and strike-slip movements along transform faults. Earthquakes, volcanic activity, mountain building, and the formation of ocean basins can occur on faults between tectonic plates.

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

Geographical 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 geographic 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 continental shelves). The underwater surface is mountainous and includes a system of mid-ocean ridges, as well as submarine volcanoes, ocean trenches, submarine canyons, oceanic plateaus and abyssal plains. The remaining 29.2%, not covered by water, includes mountains, deserts, plains, plateaus, etc.

Over 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. The earth's surface is changed by glaciers, coastal erosion, the formation of coral reefs, and collisions with large meteorites.

As continental plates move across the planet, the ocean floor sinks beneath their advancing edges. At the same time, mantle material rising from the depths creates a divergent boundary at mid-ocean ridges. Together, these two processes lead to 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 Pacific Ocean and is approximately 200 million years old. By comparison, the oldest fossils found on land are about 3 billion years old.

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 by the alteration (metamorphism) of sedimentary or igneous rocks under 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 is the uppermost layer of the lithosphere and includes soil. It is located on the boundary between the lithosphere, atmosphere, and hydrosphere. Today, the total area of ​​cultivated land is 13.31% of the land surface, of which only 4.71% is permanently occupied by agricultural crops. Approximately 40% of the earth's land area today is used for arable land and pastures, this is approximately 1.3 107 km² of arable land and 3.4 107 km² of grassland.

Hydrosphere

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

The presence of liquid water on the surface of the Earth 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.

Some 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 allows us to calculate the total volume of water in them: 1.332 109 km3. If all this water were evenly distributed over the surface, it would create a layer more than 2.7 km thick. Of all the water on Earth, only 2.5% is fresh, the rest is salty. Most of the fresh water, about 68.7%, is currently contained 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 by volcanic eruptions or extracted from the cooled igneous rocks that formed the ocean floor.

Earth's atmosphere

Atmosphere is the gaseous shell surrounding planet Earth; consists 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 appearance 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 partially from meteorite bombardments. It also regulates the main climate-forming processes: the water cycle in nature, the circulation of air masses, and heat transfer. Molecules in the atmosphere can capture thermal energy, preventing it from escaping into outer space, thereby increasing the temperature of the planet. This phenomenon is known as the greenhouse effect. The main greenhouse gases are water vapor, 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 quickly 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 - 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 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 in height. Above is the transition layer - the tropopause, which separates the troposphere from the stratosphere. The temperature here is between 190-220 K.

The stratosphere is a layer of the atmosphere that is located at an altitude of 10-12 to 55 km (depending on weather conditions and time of year). It accounts for no more than 20% of the total mass of the atmosphere. This layer is characterized by a decrease in temperature to an altitude of ~25 km, followed by an increase at the border 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. The intense 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 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 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. In the mesosphere, most of the meteorites that penetrate the earth's atmosphere burn up. From the surface of the Earth they are observed as falling stars. At an altitude of 100 km above sea level there is a conventional 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 increase in temperature stops, since the air here is very rarefied and weakly absorbs solar radiation.

The ionosphere includes the last two layers. Here, molecules are ionized under the influence of the solar wind and auroras occur.

The exosphere is the outer and very rarefied part of the earth's atmosphere. In this layer, particles are able to overcome the second escape velocity of the Earth and escape into outer space. This causes a slow but steady process called atmospheric dissipation. Mostly particles of light gases 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 sustained accumulation of oxygen in the atmosphere to be possible. Consequently, 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 entering 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.

Chemical composition of the atmosphere

At the Earth's surface, 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%: hydrogen, methane, carbon monoxide, sulfur and nitrogen oxides, water vapor, and inert gases. Depending on the time of year, 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”) predominates.

Weather and climate

The earth's atmosphere has no definite boundaries; it gradually becomes thinner and more rarefied, moving into outer space. Three-quarters of the atmosphere's mass is contained in the first 11 kilometers from the planet's surface (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 cooler, denser air takes its place. This is how atmospheric circulation arises - a system of closed flows of air masses through the redistribution of thermal energy.

The basis of atmospheric circulation is the trade winds in the equatorial belt (below 30° latitude) and the westerly winds of the temperate zone (at latitudes between 30° and 60°). Ocean currents are also important factors in shaping 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 before evaporating again, repeating the cycle. This water cycle in nature is vital to the existence of life on land. The amount of precipitation that falls per year varies, ranging from several meters to several millimeters, depending on the geographical location of the region. Atmospheric circulation, topological features of the area and temperature changes 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 by temperature regime, 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 climate zones (tropical rainforests, deserts, temperate zones, continental climates and polar types), which in turn are divided into more specific subtypes.

Biosphere

The biosphere is a collection of parts of the earth’s shells (litho-, hydro- and atmosphere), which is populated 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 populated 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 more than 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), and systems of connections that exchange matter and energy between them. On land they are separated mainly by latitude, altitude and differences in precipitation. Terrestrial ecosystems, found in the Arctic or Antarctic, at high altitudes or in extremely dry areas, are relatively poor in plants and animals; species diversity reaches its peak in the tropical rainforests of the equatorial belt.

Earth's magnetic field

To a first approximation, the Earth's magnetic field is a dipole, the poles of which are located next to the geographic poles of the planet. The field forms a magnetosphere, which deflects solar wind particles. They accumulate in radiation belts - two concentric torus-shaped regions around the Earth. Near the magnetic poles, these particles can “precipitate” 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 leads to the emergence of a magnetic field near the Earth. Convection movements 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 reversal occurred approximately 700,000 years ago.

The magnetosphere is a region of space around the Earth that is formed when a stream of charged solar wind particles 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 Earth. On the night side of the planet, the magnetosphere elongates, acquiring 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 in the region of the magnetic poles.

Earth's orbit and rotation

It takes the Earth an average of 23 hours 56 minutes and 4.091 seconds (sidereal day) to complete one revolution around its axis. The planet's rotation rate 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 approximately 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 standard by 0.001 s), the axis of rotation 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 next 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 equal to 86164.098903691 seconds according to UT1 version 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/sec (at perihelion) to 29.27 km/sec (at aphelion). Moving in orbit, the Earth makes a full revolution in 365.2564 average 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 Earth's orbital speed is not constant: in July (when passing aphelion) it is minimal and amounts to 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 within the Milky Way moves at a speed of approximately 20 km/s towards a point (apex) located on the border of the constellations Lyra and Hercules, accelerating as the Universe expands.

The Moon and the Earth revolve 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. When viewed from the north celestial pole, the Moon moves around the Earth counterclockwise. The rotation of all planets around the Sun and the rotation of the Sun, Earth and Moon around their axis occur in the same direction. The Earth's rotation axis is deviated from 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 inclined 5 degrees relative to the Earth's orbit (without this deviation, 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 the 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 tilts away from the Sun, everything becomes 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 six months at the North Pole.

These climate changes (caused by the tilt of the earth's axis) lead to changing seasons. The four seasons are determined by the solstices - the moments when the earth's axis is tilted most towards the Sun or away from the Sun - and the equinoxes. The winter solstice occurs around December 21, the summer around June 21, the spring equinox around March 20, and the autumn equinox around September 23. 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 called the same, that is, for example, February in the northern hemisphere is the last (and coldest) month of winter, and in the southern hemisphere it is the last (and warmest) ) month of summer).

The tilt angle of the earth's axis is relatively constant over a long period of time. However, it undergoes slight displacements (known as nutation) at intervals of 18.6 years. There are also long-period oscillations (about 41,000 years) known as Milankovitch cycles. The orientation of the Earth's axis also changes over time, the duration of the precession period is 25,000 years; this precession is the reason for the difference between the sidereal year and the tropical year. Both of these movements are caused by the changing gravitational pull exerted by the Sun and Moon on the Earth's equatorial bulge. The Earth's poles move relative to its surface by several meters. This movement of the poles has various cyclic components, which are collectively called quasiperiodic movement. 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 the Earth's rotation is also not constant, which is reflected in the change in the length of the day.

Currently, the Earth passes perihelion around January 3 and aphelion around July 4. The amount of solar energy reaching the Earth at perihelion is 6.9% greater than at aphelion, since the distance from the Earth to the Sun at aphelion is 3.4% greater. This is explained by the inverse square law. Because the southern hemisphere is tilted toward the sun around the same time that the Earth is closest to the sun, it receives slightly more solar energy throughout 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 (sphere of influence of Earth's gravity) is approximately 1.5 million km. This is the maximum distance at which the influence of Earth's gravity is greater than the influence of the gravity of other planets and the Sun.

Observation

The Earth was first photographed from space in 1959 by 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 the Earth rise from lunar orbit. In 1972, the crew of Apollo 17 took the famous image of the Earth - "The Blue Marble".

From outer space and from the "outer" planets (located beyond the Earth's orbit), it is possible to observe the Earth's passage through phases similar to the Moon's, just as an observer on Earth 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 satellite in the solar system relative to the size of its planet. Based on 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 the Moon’s revolution 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 Moon's orbit around the Earth, the Sun illuminates various parts of the satellite's surface, which manifests itself in the phenomenon of lunar phases: the dark part of the surface is separated from the light part by a terminator.

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

The Moon can significantly influence 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 Earth's tidal synchronization with the Moon. If the Earth's rotation axis were to move closer to the ecliptic plane, the planet's climate would become extremely harsh as a result. 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 switch places. The poles would point directly toward the Sun in summer and winter. Planetologists who have studied this situation claim that, in this case, all large animals and higher plants would die 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's, 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 by the collision of the protoplanet Theia (about the size of Mars) with the proto-Earth. This, among other things, explains the reasons for the similarities and differences in the composition of lunar soil and terrestrial soil.

Currently, the Earth has no other natural satellites except the Moon, but there are at least two natural co-orbital satellites - asteroids 3753 Cruithney, 2002 AA29 and many artificial ones.

Near-Earth asteroids

The fall of large (several thousand km in diameter) asteroids onto the Earth poses a danger of its destruction, however, all such 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 have caused several mass extinctions. Asteroids with perihelion distances less than or equal to 1.3 astronomical units that may approach Earth within a distance of less than or equal to 0.05 AU in the foreseeable future. That is, they 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 falling onto 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.

Geographical 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

Using sushi

Data for 2011

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

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

Socio-economic geography

On October 31, 2011, the world's population reached 7 billion people. The UN estimates that 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, and varies greatly in different parts of the Earth, with the highest in Asia. The population's urbanization rate is projected to reach 60% by 2030, up from the current global average of 49%.

Role in culture

The Russian word “earth” goes back to the Praslavs. *zemja with the same meaning, which, in turn, continues pra-i.e. *dheĝhōm “earth”.

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

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

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

The Aztecs called the Earth Tonantzin - “our mother.” For 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; for example, 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; Pythagoras adhered to this point of view. In the Middle Ages, most Europeans believed that the Earth was spherical, which was attested to 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 features 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 space flight, the Earth was often depicted as a green world. Science fiction writer Frank Paul may have been the first to depict a cloudless blue planet (with land clearly visible) on the back of the July 1940 issue of Amazing Stories magazine.

In 1972, the crew of Apollo 17 took the famous photograph of the Earth, called “Blue Marble.” A photograph of the 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. The Earth was also compared to a large spaceship with a life support system that must be maintained. The Earth's biosphere has sometimes been described as one large organism.

Ecology

Over the past two centuries, a growing environmental movement has expressed concern about the growing impact of human activities on the Earth's environment. The key objectives of this socio-political movement are the protection of natural resources and the elimination of pollution. Conservationists advocate for sustainable use of the planet's resources and environmental management. This, in their opinion, can be achieved by making changes to government policy and changing the individual attitude of each person. This is especially true for 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 Sun’s core, the star’s luminosity 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's orbit. According to some climate models, increasing the amount of solar radiation falling on the Earth's surface will lead to catastrophic consequences, including the possibility of complete evaporation of all oceans.

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

3.5 billion years from now, the Sun's luminosity will increase by 40% compared to its current level. Conditions on the surface of the Earth by that time will be similar to the surface conditions of modern Venus: the oceans will completely evaporate and fly into space, the surface will become a barren hot desert. This catastrophe will make it impossible for any form of life to exist on Earth. In 7.05 billion years, the solar core will run out of hydrogen. This will lead to the Sun leaving the main sequence and entering the red giant stage. The model shows that it will increase in radius to a value equal to approximately 77.5% of the current radius of the Earth's orbit (0.775 AU), and its luminosity will increase by a factor of 2350-2700. However, by that time the Earth's orbit may increase to 1.4 AU. That is, since the Sun’s gravity 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 from 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 will reach 1370 °C. Earth's atmosphere is likely to be blown into outer space by the strongest solar wind emitted by the red giant. In 10 million years from the time the Sun enters the red giant phase, temperatures in the solar core will reach 100 million K, a helium flare will occur, and a thermonuclear reaction of the synthesis of carbon and oxygen from helium will begin, the Sun will decrease in radius to 9.5 modern ones. The 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 entered the asymptotic giant branch, the Sun will increase in diameter by 213 times. After 20 million years, a period of unstable pulsations of the star's surface will begin. This phase of the Sun's existence will be accompanied by powerful flares, at times its luminosity will exceed the current level by 5000 times. This will happen because previously unaffected helium residues will enter into the thermonuclear reaction.

In about 75,000 years (according to other sources - 400,000), the Sun will shed its shells, and ultimately all that will remain of the red giant is its small central core - a white dwarf, a small, hot, but very dense object, with a mass of about 54.1% from the original solar one. If the Earth can avoid being absorbed by the outer shells of the Sun during the red giant phase, then it will exist for many 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) form) will not exist on Earth. As the Sun enters the white dwarf phase, the Earth's surface will gradually cool and plunge into darkness. If you imagine the size of the Sun from the surface of the future Earth, it will look not like a disk, but like a shining point with angular dimensions of about 0°0’9″.

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

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The Earth is the object of study for a significant amount of geosciences. The study of the Earth as a celestial body belongs to the field, the structure and composition of the Earth is studied by geology, the state of the atmosphere - meteorology, the totality of manifestations of life on the planet - biology. Geography describes the relief features of the planet's surface - oceans, seas, lakes and waters, continents and islands, mountains and valleys, as well as settlements and societies. education: cities and villages, states, economic regions, etc.

Planetary characteristics

The Earth revolves around the star Sun in an elliptical orbit (very close to circular) with an average speed of 29,765 m/s at an average distance of 149,600,000 km per period, which is approximately equal to 365.24 days. The Earth has a satellite, which revolves around the Sun at an average distance of 384,400 km. The inclination of the earth's axis to the ecliptic plane is 66 0 33 "22". The period of revolution of the planet around its axis is 23 hours 56 minutes 4.1 s. Rotation around its axis causes the change of day and night, and the tilt of the axis and revolution around the Sun causes the change of times of the year.

The shape of the Earth is geoid. The average radius of the Earth is 6371.032 km, equatorial - 6378.16 km, polar - 6356.777 km. The surface area of ​​the globe is 510 million km², volume - 1.083 10 12 km², average density - 5518 kg / m³. The mass of the Earth is 5976.10 21 kg. The earth has a magnetic field and a closely related electric field. The Earth's gravitational field determines its close to spherical shape and the existence of an atmosphere.

According to modern cosmogonic concepts, the Earth was formed approximately 4.7 billion years ago from gaseous matter scattered in the protosolar system. As a result of the differentiation of the Earth's substance, under the influence of its gravitational field, in conditions of heating of the earth's interior, shells of different chemical composition, state of aggregation and physical properties - the geosphere - arose and developed: the core (in the center), the mantle, the earth's crust, the hydrosphere, the atmosphere, the magnetosphere . The composition of the Earth is dominated by iron (34.6%), oxygen (29.5%), silicon (15.2%), magnesium (12.7%). The Earth's crust, mantle, and inner core are solid (the outer core is considered liquid). From the surface of the Earth towards the center, pressure, density and temperature increase. The pressure at the center of the planet is 3.6 10 11 Pa, the density is approximately 12.5 10³ kg/m³, and the temperature ranges from 5000 to 6000 °C. The main types of the earth's crust are continental and oceanic; in the transition zone from the continent to the ocean, crust of an intermediate structure is developed.

Shape of the Earth

The figure of the Earth is an idealization that is used to try to describe the shape of the planet. Depending on the purpose of the description, various models of the shape of the Earth are used.

First approach

The roughest form of description of the figure of the Earth at the first approximation is a sphere. For most problems of general geoscience, this approximation seems sufficient to be used in the description or study of certain geographical processes. In this case, the oblateness of the planet at the poles is rejected as an insignificant remark. The Earth has one axis of rotation and an equatorial plane - a plane of symmetry and a plane of symmetry of meridians, which characteristically distinguishes it from the infinity of sets of symmetry of an ideal sphere. The horizontal structure of the geographic envelope is characterized by a certain zonality and a certain symmetry relative to the equator.

Second approximation

At a closer approach, the figure of the Earth is equated to an ellipsoid of revolution. This model, characterized by a pronounced axis, an equatorial plane of symmetry and meridional planes, is used in geodesy for calculating coordinates, constructing cartographic networks, calculations, etc. The difference between the semi-axes of such an ellipsoid is 21 km, the major axis is 6378.160 km, the minor axis is 6356.777 km, the eccentricity is 1/298.25. The position of the surface can easily be theoretically calculated, but it cannot be determined experimentally in nature.

Third approximation

Since the equatorial section of the Earth is also an ellipse with a difference in the lengths of the semi-axes of 200 m and an eccentricity of 1/30000, the third model is a triaxial ellipsoid. This model is almost never used in geographical studies; it only indicates the complex internal structure of the planet.

Fourth approximation

The geoid is an equipotential surface that coincides with the average level of the World Ocean; it is the geometric locus of points in space that have the same gravitational potential. Such a surface has an irregular complex shape, i.e. is not a plane. The level surface at each point is perpendicular to the plumb line. The practical significance and importance of this model is that only with the help of a plumb line, level, level and other geodetic instruments can one trace the position of level surfaces, i.e. in our case, the geoid.

Ocean and land

A general feature of the structure of the earth's surface is its distribution into continents and oceans. Most of the Earth is occupied by the World Ocean (361.1 million km² 70.8%), land is 149.1 million km² (29.2%), and forms six continents (Eurasia, Africa, North America, South America , and Australia) and islands. It rises above the level of the world's oceans by an average of 875 m (the highest height is 8848 m - Mount Chomolungma), mountains occupy more than 1/3 of the land surface. Deserts cover approximately 20% of the land surface, forests - about 30%, glaciers - over 10%. The height amplitude on the planet reaches 20 km. The average depth of the world's oceans is approximately 3800 m (the greatest depth is 11020 m - the Mariana Trench (trench) in the Pacific Ocean). The volume of water on the planet is 1370 million km³, the average salinity is 35 ‰ (g/l).

Geological structure

Geological structure of the Earth

The inner core is thought to be 2,600 km in diameter and composed of pure iron or nickel, the outer core is 2,250 km thick of molten iron or nickel, and the mantle, about 2,900 km thick, is composed primarily of hard rock, separated from the crust by the Mohorovic surface. The crust and upper mantle form 12 main moving blocks, some of which support continents. Plateaus are constantly moving slowly, this movement is called tectonic drift.

Internal structure and composition of the “solid” Earth. 3. consists of three main geospheres: the earth's crust, mantle and core, which, in turn, is divided into a number of layers. The substance of these geospheres differs in physical properties, condition and mineralogical composition. Depending on the magnitude of the velocities of seismic waves and the nature of their changes with depth, the “solid” Earth is divided into eight seismic layers: A, B, C, D ", D ", E, F and G. In addition, a particularly strong layer is distinguished in the Earth the lithosphere and the next, softened layer - the asthenosphere. Ball A, or the earth's crust, has a variable thickness (in the continental region - 33 km, in the oceanic region - 6 km, on average - 18 km).

The crust thickens under the mountains and almost disappears in the rift valleys of mid-ocean ridges. At the lower boundary of the earth's crust, the Mohorovicic surface, the velocities of seismic waves increase abruptly, which is mainly associated with a change in the material composition with depth, the transition from granites and basalts to ultrabasic rocks of the upper mantle. Layers B, C, D", D" are included in the mantle. Layers E, F and G form the Earth's core with a radius of 3486 km. At the border with the core (Gutenberg surface), the speed of longitudinal waves sharply decreases by 30%, and transverse waves disappear, which means that the outer core (layer E, extends to a depth of 4980 km) liquid Below the transition layer F (4980-5120 km) there is a solid inner core (layer G), in which transverse waves again propagate.

The following chemical elements predominate in the solid crust: oxygen (47.0%), silicon (29.0%), aluminum (8.05%), iron (4.65%), calcium (2.96%), sodium (2.5%), magnesium (1.87%), potassium (2.5%), titanium (0.45%), which add up to 98.98%. The rarest elements: Po (approximately 2.10 -14%), Ra (2.10 -10%), Re (7.10 -8%), Au (4.3 10 -7%), Bi (9 10 -7%) etc.

As a result of magmatic, metamorphic, tectonic and sedimentation processes, the earth's crust is sharply differentiated; complex processes of concentration and dispersion of chemical elements take place in it, leading to the formation of various types of rocks.

The upper mantle is believed to be similar in composition to ultramafic rocks, dominated by O (42.5%), Mg (25.9%), Si (19.0%) and Fe (9.85%). In mineral terms, olivine reigns here, with fewer pyroxenes. The lower mantle is considered an analogue of stony meteorites (chondrites). The core of the earth is similar in composition to iron meteorites and contains approximately 80% Fe, 9% Ni, 0.6% Co. Based on the meteorite model, the average composition of the Earth was calculated, which is dominated by Fe (35%), A (30%), Si (15%) and Mg (13%).

Temperature is one of the most important characteristics of the earth's interior, allowing us to explain the state of matter in various layers and build a general picture of global processes. According to measurements in wells, the temperature in the first kilometers increases with depth with a gradient of 20 °C/km. At a depth of 100 km, where the primary sources of volcanoes are located, the average temperature is slightly lower than the melting point of rocks and is equal to 1100 ° C. At the same time, under the oceans at a depth of 100-200 km the temperature is 100-200 ° C higher than in the continents. The density of matter in layer C at 420 km corresponds to a pressure of 1.4 10 10 Pa and is identified with the phase transition to olivine, which occurs at a temperature of approximately 1600 ° C. At the boundary with the core at a pressure of 1.4 10 11 Pa and temperature At about 4000 °C, silicates are in a solid state, and iron is in a liquid state. In the transition layer F, where iron solidifies, the temperature can be 5000 ° C, in the center of the earth - 5000-6000 ° C, i.e., adequate to the temperature of the Sun.

Earth's atmosphere

The Earth's atmosphere, the total mass of which is 5.15 10 15 tons, consists of air - a mixture of mainly nitrogen (78.08%) and oxygen (20.95%), 0.93% argon, 0.03% carbon dioxide, the rest is water vapor, as well as inert and other gases. The maximum land surface temperature is 57-58 ° C (in the tropical deserts of Africa and North America), the minimum is about -90 ° C (in the central regions of Antarctica).

The Earth's atmosphere protects all living things from the harmful effects of cosmic radiation.

Chemical composition of the Earth's atmosphere: 78.1% - nitrogen, 20 - oxygen, 0.9 - argon, the rest - carbon dioxide, water vapor, hydrogen, helium, neon.

The Earth's atmosphere includes :

• troposphere (up to 15 km)
• stratosphere (15-100 km)
• ionosphere (100 - 500 km).

Between the troposphere and stratosphere there is a transition layer - the tropopause. In the depths of the stratosphere, under the influence of sunlight, an ozone shield is created that protects living organisms from cosmic radiation. Above are the meso-, thermo- and exospheres.

Weather and climate

The lower layer of the atmosphere is called the troposphere. Phenomena that determine the weather occur in it. Due to the uneven heating of the Earth's surface by solar radiation, large masses of air constantly circulate in the troposphere. The main air currents in the Earth's atmosphere are the trade winds in the band up to 30° along the equator and the westerly winds of the temperate zone in the band from 30° to 60°. Another factor in heat transfer is the ocean current system.

Water has a constant cycle on the surface of the earth. Evaporating from the surface of water and land, under favorable conditions, water vapor rises up in the atmosphere, which leads to the formation of clouds. Water returns to the surface of the earth in the form of precipitation and flows down to the seas and oceans throughout the year.

The amount of solar energy that the Earth's surface receives decreases with increasing latitude. The further from the equator, the smaller the angle of incidence of the sun's rays on the surface, and the greater the distance that the ray must travel in the atmosphere. As a consequence, the average annual temperature at sea level decreases by about 0.4 °C per degree of latitude. The surface of the Earth is divided into latitudinal zones with approximately the same climate: tropical, subtropical, temperate and polar. The classification of climates depends on temperature and precipitation. The most widely recognized is the Köppen climate classification, which distinguishes five broad groups - humid tropics, desert, humid mid-latitudes, continental climate, cold polar climate. Each of these groups is divided into specific groups.

Human influence on the Earth's atmosphere

The Earth's atmosphere is significantly influenced by human activity. About 300 million cars annually emit 400 million tons of carbon oxides, more than 100 million tons of carbohydrates, and hundreds of thousands of tons of lead into the atmosphere. Powerful producers of atmospheric emissions: thermal power plants, metallurgical, chemical, petrochemical, pulp and other industries, motor vehicles.

Systematic inhalation of polluted air significantly worsens people's health. Gaseous and dust impurities can give the air an unpleasant odor, irritate the mucous membranes of the eyes and upper respiratory tract and thereby reduce their protective functions, and cause chronic bronchitis and lung diseases. Numerous studies have shown that against the background of pathological abnormalities in the body (diseases of the lungs, heart, liver, kidneys and other organs), the harmful effects of atmospheric pollution are more pronounced. Acid rain has become an important environmental problem. Every year, when burning fuel, up to 15 million tons of sulfur dioxide enters the atmosphere, which, when combined with water, forms a weak solution of sulfuric acid, which falls to the ground along with rain. Acid rain negatively affects people, crops, buildings, etc.

Ambient air pollution can also indirectly affect the health and sanitary living conditions of people.

The accumulation of carbon dioxide in the atmosphere can cause climate warming as a result of the greenhouse effect. Its essence lies in the fact that the layer of carbon dioxide, which freely transmits solar radiation to the Earth, will delay the return of thermal radiation to the upper layers of the atmosphere. In this regard, the temperature in the lower layers of the atmosphere will increase, which, in turn, will lead to the melting of glaciers, snow, rising levels of oceans and seas, and flooding of a significant part of the land.

Story

The Earth formed approximately 4540 million years ago from a disk-shaped protoplanetary cloud along with the other planets of the solar system. The formation of the Earth as a result of accretion lasted 10-20 million years. At first the Earth was completely molten, but gradually cooled, and a thin solid shell formed on its surface - the earth's crust.

Shortly after the formation of the Earth, approximately 4530 million years ago, the Moon formed. The modern theory of the formation of a single natural satellite of the Earth claims that this happened as a result of a collision with a massive celestial body, which was called Theia.
The Earth's primary atmosphere was formed as a result of degassing of rocks and volcanic activity. Water condensed from the atmosphere to form the World Ocean. Despite the fact that the Sun by that time was 70% weaker than it is now, geological data shows that the ocean did not freeze, which may be due to the greenhouse effect. About 3.5 billion years ago, the Earth's magnetic field formed, protecting its atmosphere from the solar wind.

The formation of the Earth and the initial stage of its development (lasting approximately 1.2 billion years) belong to pre-geological history. The absolute age of the oldest rocks is over 3.5 billion years and, starting from this moment, the geological history of the Earth begins, which is divided into two unequal stages: the Precambrian, which occupies approximately 5/6 of the entire geological chronology (about 3 billion years), and Phanerozoic, covering the last 570 million years. About 3-3.5 billion years ago, as a result of the natural evolution of matter, life arose on Earth, the development of the biosphere began - the totality of all living organisms (the so-called living matter of the Earth), which significantly influenced the development of the atmosphere, hydrosphere and geosphere (at least in parts of the sedimentary shell). As a result of the oxygen catastrophe, the activity of living organisms changed the composition of the Earth's atmosphere, enriching it with oxygen, which created the opportunity for the development of aerobic living beings.

A new factor that has a powerful influence on the biosphere and even the geosphere is the activity of mankind, which appeared on Earth after the appearance of man as a result of evolution less than 3 million years ago (unity regarding dating has not been achieved and some researchers believe - 7 million years ago). Accordingly, in the process of development of the biosphere, formations and further development of the noosphere are distinguished - the shell of the Earth, which is greatly influenced by human activity.

The high growth rate of the Earth's population (the world's population was 275 million in 1000, 1.6 billion in 1900 and approximately 6.7 billion in 2009) and the increasing influence of human society on the natural environment have raised problems of rational use of all natural resources and protection nature.

We live in a world in which everything seems so familiar and established that we never think about why the things around us are named that way. How did the objects around us get their names? And why was our planet called “Earth” and not otherwise?

First, let’s find out how names are given now. After all, astronomers discover new things, biologists find new plant species, and entomologists find insects. They also need to be given a name. Who is dealing with this issue now? You need to know this to find out why the planet was called “Earth”.

Toponymy will help

Since our planet is a geographical object, let us turn to the science of toponymy. She studies place names. More precisely, she studies the origin, meaning, and development of the toponym. Therefore, this amazing science is in close interaction with history, geography and linguistics. Of course, there are situations when the name, for example, of a street, is given just like that, by accident. But in most cases, toponyms have their own history, sometimes going back centuries.

The planets will give the answer

When answering the question of why the Earth was called Earth, we must not forget that our home is He is part of the planets of the solar system, which also have names. Perhaps, by studying their origin, it will be possible to find out why the Earth was called Earth?

Regarding the most ancient names, scientists and researchers do not have an exact answer to the question of how exactly they arose. Today there are only numerous hypotheses. Which of them is correct - we will never know. As for the names of the planets, the most common version of their origin is this: they are named after the ancient Roman gods. Mars - the Red Planet - received the name of the god of war, who cannot be imagined without blood. Mercury, the fastest planet, revolving faster than others around the Sun, owes its name to the lightning-fast messenger of Jupiter.

It's all about the gods

To what deity does the Earth owe its name? Almost every nation had such a goddess. The ancient Scandinavians - Jord, the Celts - Echte. The Romans called her Tellus, and the Greeks called her Gaia. None of these names are similar to the current name of our planet. But, answering the question of why the Earth was called Earth, let us remember two names: Yord and Tellus. They will still be useful to us.

Voice of Science

In fact, the question of the origin of the name of our planet, with which children so love to torment their parents, has interested scientists for a long time. Many versions were put forward and smashed to smithereens by opponents, until a few remained that were considered the most probable.

In astrology, it is customary to use the name of planets. And in this language, the name of our planet is pronounced as Terra(“earth, soil”). In turn, this word goes back to the Proto-Indo-European ters meaning “dry; dry". Along with Terra the name is often used to refer to the Earth Tellus. And we have already encountered it above - this is what the Romans called our planet. Man, as an exclusively land-based creature, could name the place where he lives only by analogy with the earth, the soil under his feet. It is also possible to draw analogies with the biblical tales about God’s creation of the earth’s firmament and the first man, Adam, from clay. Why was the Earth called Earth? Because for humans it was the only habitat.

Apparently, it was on this principle that the current name of our planet appeared. If we take the Russian name, then it comes from the Proto-Slavic root land-, which translated means “low”, “bottom”. Perhaps this is due to the fact that in ancient times people considered the Earth to be flat.

In English the name of the Earth sounds like Earth. It comes from two words - erthe And eorthe. And those, in turn, descended from the even more ancient Anglo-Saxon erda(remember how the Scandinavians called the goddess of the Earth?) - “ground” or “soil”.

Another version of why the Earth was called Earth says that man was able to survive only thanks to agriculture. It was after the advent of this activity that the human race began to develop successfully.

Why is the Earth called the nurse?

The Earth is a huge biosphere inhabited by diverse life. And all living things that exist on it feed on the Earth. Plants take the necessary microelements from the soil, insects and small rodents feed on them, which, in turn, serve as food for larger animals. People are engaged in agriculture and grow wheat, rye, rice and other types of plants necessary for life. They raise livestock that eat plant foods.

Life on our planet is a chain of interconnected living organisms that do not die only thanks to the Earth-nurse. If a new ice age begins on the planet, the likelihood of which scientists have again begun to talk about after unprecedented cold this winter in many warm countries, then the survival of humanity will be in doubt. The ice-bound land will not be able to produce a harvest. This is a disappointing forecast.

Humanity has only just learned that the Earth has another satellite besides the Moon.

The second satellite of the Earth, astronomers say, differs from the big Moon in that it completes a full revolution around the Earth in 789 years. Its orbit is shaped like a horseshoe, and is located at a distance comparable to the distance from Earth to Mars. The satellite cannot approach our planet closer than 30 million kilometers, which is 30 times further than the distance to the Moon.

Relative motion of the Earth and Cruithne in their orbits.

Scientists say that the Earth's second natural satellite is the near-Earth asteroid Cruithney. Its peculiarity is that it intersects the orbits of three planets: Earth, Mars and Venus.

The diameter of the second Moon is only five kilometers, and this natural satellite of our planet will come to its closest distance to Earth in two thousand years. At the same time, scientists do not expect a collision between the Earth and Cruithne, which has approached our planet.

The satellite will pass from the planet at a distance of 406,385 kilometers. At this moment, the Moon will be located in the constellation Leo. Our planet's satellite will be fully visible, but the size of the Moon will be 13 percent smaller than at the time of its closest approach to the Earth. A collision is not predicted: the Earth's orbit does not intersect anywhere with Cruithney's orbit, since the latter is in a different orbital plane and is inclined to the Earth's orbit at an angle of 19.8 °.

Also, according to experts, in 7899 years our second moon will pass very close to Venus and there is a possibility that Venus will attract it to itself and thereby we will lose “Cruithney”.

The new moon Cruithney was discovered on October 10, 1986 by British amateur astronomer Duncan Waldron. Duncan spotted it in a photograph from the Schmidt telescope. From 1994 to 2015, the maximum annual approach of this asteroid to the Earth occurs in November.

Due to the very large eccentricity, the orbital speed this asteroid changes much more strongly than that of the Earth, so from the point of view of an observer on Earth, if we take the Earth as a reference system and consider it stationary, it turns out that not the asteroid, but its orbit rotates around the Sun, while the asteroid itself begins to describe ahead of the Earth a horseshoe-shaped trajectory, reminiscent of a “bean” in shape, with a period equal to the period of revolution of the asteroid around the Sun - 364 days.

Cruithne will approach Earth again in June 2292. The asteroid will make a series of annual approaches to the Earth at a distance of 12.5 million km, as a result of which there will be a gravitational exchange of orbital energy between the Earth and the asteroid, which will lead to a change in the orbit of the asteroid and Cruitney will again begin to migrate from the Earth, but this time in the other direction , - it will lag behind the Earth.

Earth- the third planet of the solar system. Find out the description of the planet, mass, orbit, size, interesting facts, distance to the Sun, composition, life on Earth.

Of course we love our planet. And not only because this is our home, but also because this is a unique place in the solar system and the Universe, because so far we only know life on Earth. Lives in the inner part of the system and occupies a place between Venus and Mars.

Planet Earth also called the Blue Planet, Gaia, World and Terra, which reflects its role for each people in historical terms. We know that our planet is rich in many different forms of life, but how exactly did it manage to become so? First, consider some interesting facts about Earth.

Interesting facts about planet Earth

Rotation gradually slows down

• For earthlings, the entire process of slowing down the rotation of the axis occurs almost imperceptibly - 17 milliseconds per 100 years. But the nature of the speed is not uniform. Because of this, the length of the day increases. In 140 million years, a day will cover 25 hours.

Believed that the Earth was the center of the Universe

• Ancient scientists could observe celestial objects from the position of our planet, so it seemed that all objects in the sky were moving relative to us, and we remained at one point. As a result, Copernicus stated that the Sun (the heliocentric system of the world) is at the center of everything, although now we know that this does not correspond to reality, if we take the scale of the Universe.

Endowed with a powerful magnetic field

• The Earth's magnetic field is created by the nickel-iron planetary core, which rotates rapidly. The field is important because it protects us from the influence of the solar wind.

Has one satellite

• If you look at the percentage, the Moon is the largest satellite in the system. But in reality it is in 5th position in size.

The only planet not named after a deity

• Ancient scientists named all 7 planets in honor of the gods, and modern scientists followed the tradition when discovering Uranus and Neptune.

First in density

• Everything is based on the composition and specific part of the planet. So the core is represented by metal and bypasses the crust in density. The average density of the earth is 5.52 grams per cm 3.

Size, mass, orbit of planet Earth

With a radius of 6371 km and a mass of 5.97 x 10 24 kg, the Earth ranks 5th in size and massiveness. It is the largest terrestrial planet, but it is smaller in size than the gas and ice giants. However, in terms of density (5.514 g/cm3) it ranks first in the Solar System.

Polar compression	0,0033528
Equatorial	6378.1 km
Polar radius	6356.8 km
Average radius	6371.0 km
Great circle circumference	40,075.017 km (equator) (meridian)
Surface area	510,072,000 km²
Volume	10.8321 10 11 km³
Weight	5.9726 10 24 kg
Average density	5.5153 g/cm³
Acceleration free falls at the equator	9.780327 m/s²
First escape velocity	7.91 km/s
Second escape velocity	11.186 km/s
Equatorial speed rotation	1674.4 km/h
Rotation period	(23 h 56 m 4,100 s)
Axis tilt	23°26’21",4119
Albedo	0.306 (Bond) 0.367 (geom.)

There is a slight eccentricity in the orbit (0.0167). The distance from the star at perihelion is 0.983 AU, and at aphelion – 1.015 AU.

One passage around the Sun takes 365.24 days. We know that due to the existence of leap years, we add a day every 4 passes. We are used to thinking that a day lasts 24 hours, but in reality this time takes 23 hours 56 minutes and 4 seconds.

If you observe the rotation of the axis from the poles, you can see that it occurs counterclockwise. The axis is inclined at 23.439281° from the perpendicular to the orbital plane. This affects the amount of light and heat.

If the North Pole is turned towards the Sun, then summer occurs in the northern hemisphere, and winter in the southern hemisphere. At a certain time, the Sun does not rise at all over the Arctic Circle, and then night and winter last there for 6 months.

Composition and surface of planet Earth

The shape of planet Earth is like a spheroid, flattened at the poles and with a convexity at the equatorial line (diameter - 43 km). This happens due to rotation.

The structure of the Earth is represented by layers, each of which has its own chemical composition. It differs from other planets in that our core has a clear distribution between the solid inner (radius - 1220 km) and the liquid outer (3400 km).

Next comes the mantle and crust. The first deepens to 2890 km (the densest layer). It is represented by silicate rocks with iron and magnesium. The crust is divided into lithosphere (tectonic plates) and asthenosphere (low viscosity). You can carefully examine the structure of the Earth in the diagram.

The lithosphere breaks down into solid tectonic plates. These are rigid blocks that move relative to each other. There are points of connection and break. It is their contact that leads to earthquakes, volcanic activity, the creation of mountains and ocean trenches.

There are 7 main plates: Pacific, North American, Eurasian, African, Antarctic, Indo-Australian and South American.

Our planet is notable for the fact that approximately 70.8% of its surface is covered with water. The bottom map of the Earth shows tectonic plates.

The earth's landscape is different everywhere. The submerged surface resembles mountains and has underwater volcanoes, oceanic trenches, canyons, plains and even oceanic plateaus.

During the development of the planet, the surface was constantly changing. Here it is worth considering the movement of tectonic plates, as well as erosion. It also affects the transformation of glaciers, the creation of coral reefs, meteorite impacts, etc.

Continental crust is represented by three varieties: magnesium rocks, sedimentary and metamorphic. The first is divided into granite, andesite and basalt. Sedimentary makes up 75% and is created by burying accumulated sediment. The latter is formed during the icing of sedimentary rock.

From the lowest point, the surface height reaches -418 m (at the Dead Sea) and rises to 8848 m (the top of Everest). The average height of the land above sea level is 840 m. The mass is also divided between the hemispheres and continents.

The outer layer contains soil. This is a certain line between the lithosphere, atmosphere, hydrosphere and biosphere. Approximately 40% of the surface is used for agricultural purposes.

Atmosphere and temperature of planet Earth

There are 5 layers of the earth's atmosphere: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The higher you rise, the less air, pressure and density you will feel.

The troposphere is located closest to the surface (0-12 km). Contains 80% of the mass of the atmosphere, with 50% located within the first 5.6 km. It consists of nitrogen (78%) and oxygen (21%) with admixtures of water vapor, carbon dioxide and other gaseous molecules.

In the interval of 12-50 km we see the stratosphere. It is separated from the first tropopause - a line with relatively warm air. This is where the ozone layer is located. The temperature rises as the layer absorbs ultraviolet light. The atmospheric layers of the Earth are shown in the figure.

This is a stable layer and is practically free from turbulence, clouds and other weather formations.

At an altitude of 50-80 km there is the mesosphere. This is the coldest place (-85°C). It is located near the mesopause, extending from 80 km to the thermopause (500-1000 km). The ionosphere lives within the range of 80-550 km. Here the temperature increases with altitude. In the photo of the Earth you can admire the northern lights.

The layer is devoid of clouds and water vapor. But it is here that auroras form and the International Space Station is located (320-380 km).

The outermost sphere is the exosphere. This is a transition layer to outer space, devoid of an atmosphere. Represented by hydrogen, helium and heavier molecules with low density. However, the atoms are so scattered that the layer does not behave like a gas, and particles are constantly being removed into space. Most of the satellites live here.

This mark is influenced by many factors. The Earth makes an axial revolution every 24 hours, which means one side always experiences night and lower temperatures. In addition, the axis is tilted, so the northern and southern hemispheres alternately move away and move closer.

All this creates seasonality. Not every part of the earth experiences sharp drops and rises in temperatures. For example, the amount of light entering the equatorial line remains virtually unchanged.

If we take the average, we get 14°C. But the maximum was 70.7°C (Lut Desert), and the minimum of -89.2°C was reached at the Soviet Vostok station on the Antarctic plateau in July 1983.

Moon and asteroids of the Earth

The planet has only one satellite, which affects not only the physical changes of the planet (for example, the ebb and flow of tides), but is also reflected in history and culture. To be precise, the Moon is the only celestial body on which a person has walked. This happened on July 20, 1969 and the right to take the first step went to Neil Armstrong. Overall, 13 astronauts landed on the satellite.

The Moon appeared 4.5 billion years ago due to the collision of the Earth and a Martian-sized object (Theia). We can be proud of our satellite, because it is one of the largest moons in the system, and also ranks second in density (after Io). It is in gravitational locking (one side always faces the Earth).

The diameter covers 3474.8 km (1/4 of the Earth), and the mass is 7.3477 x 10 22 kg. The average density is 3.3464 g/cm3. In terms of gravity it reaches only 17% of the Earth's. The moon influences the earth's tides, as well as the activity of all living organisms.

Don't forget that there are lunar and solar eclipses. The first happens when the Moon falls into the Earth's shadow, and the second happens when a satellite passes between us and the Sun. The satellite's atmosphere is weak, causing temperatures to fluctuate greatly (from -153°C to 107°C).

Helium, neon and argon can be found in the atmosphere. The first two are created by the solar wind, and argon is due to the radioactive decay of potassium. There is also evidence of frozen water in craters. The surface is divided into different types. There is Maria - flat plains that ancient astronomers mistook for seas. Terras are lands, like highlands. Even mountainous areas and craters can be seen.

The Earth has five asteroids. Satellite 2010 TK7 resides at L4, and asteroid 2006 RH120 approaches the Earth-Moon system every 20 years. If we talk about artificial satellites, there are 1265 of them, as well as 300,000 pieces of debris.

Formation and evolution of planet Earth

In the 18th century, humanity came to the conclusion that our terrestrial planet, like the entire solar system, emerged from a nebulous cloud. That is, 4.6 billion years ago, our system resembled a circumstellar disk, represented by gas, ice and dust. Then most of it approached the center and, under pressure, transformed into the Sun. The remaining particles created the planets we know.

The primordial Earth appeared 4.54 billion years ago. From the very beginning, it was molten due to volcanoes and frequent collisions with other objects. But 4-2.5 billion years ago, solid crust and tectonic plates appeared. Degassing and volcanoes created the first atmosphere, and ice arriving on comets formed the oceans.

The surface layer did not remain frozen, so the continents converged and moved apart. About 750 million years ago, the very first supercontinent began to break apart. Pannotia was created 600-540 million years ago, and the last one (Pangea) collapsed 180 million years ago.

The modern picture was created 40 million years ago and took hold 2.58 million years ago. The last ice age, which began 10,000 years ago, is currently underway.

It is believed that the first hints of life on Earth appeared 4 billion years ago (Archean eon). Due to chemical reactions, self-replicating molecules appeared. Photosynthesis created molecular oxygen, which, together with ultraviolet rays, formed the first ozone layer.

Then various multicellular organisms began to appear. Microbial life arose 3.7-3.48 billion years ago. 750-580 million years ago, most of the planet was covered with glaciers. Active reproduction of organisms began during the Cambrian explosion.

Since that time (535 million years ago), history includes 5 major extinction events. The last one (the death of dinosaurs from a meteorite) occurred 66 million years ago.

They were replaced by new species. The African ape-like animal stood on its hind legs and freed its forelimbs. This stimulated the brain to use different tools. Then we know about the development of agricultural crops, socialization and other mechanisms that led us to modern man.

Reasons for the habitability of planet Earth

If a planet meets a number of conditions, then it is considered potentially habitable. Now the Earth is the only lucky one with developed life forms. What is needed? Let's start with the main criterion - liquid water. In addition, the main star must provide enough light and heat to maintain the atmosphere. An important factor is location in the habitat zone (the distance of the Earth from the Sun).

We should understand how lucky we are. After all, Venus is similar in size, but due to its close location to the Sun, it is a hellishly hot place with acid rain. And Mars, which lives behind us, is too cold and has a weak atmosphere.

Planet Earth Research

The first attempts to explain the origin of the Earth were based on religion and myths. Often the planet became a deity, namely a mother. Therefore, in many cultures, the history of everything begins with the mother and the birth of our planet.

There are also a lot of interesting things in the form. In ancient times, the planet was considered flat, but different cultures added their own characteristics. For example, in Mesopotamia, a flat disk floated in the middle of the ocean. The Mayans had 4 jaguars that held up the heavens. For the Chinese it was generally a cube.

Already in the 6th century BC. e. scientists sewed it onto a round shape. Surprisingly, in the 3rd century BC. e. Eratosthenes even managed to calculate the circle with an error of 5-15%. The spherical shape became established with the advent of the Roman Empire. Aristotle spoke about changes in the earth's surface. He believed that it happens too slowly, so a person is not able to catch it. This is where attempts to understand the age of the planet arise.

Scientists are actively studying geology. The first catalog of minerals was created by Pliny the Elder in the 1st century AD. In 11th century Persia, explorers studied Indian geology. The theory of geomorphology was created by the Chinese naturalist Shen Guo. He identified marine fossils located far from the water.

In the 16th century, understanding and exploration of the Earth expanded. We should thank the heliocentric model of Copernicus, which proved that the Earth is not the universal center (previously they used the geocentric system). And also Galileo Galilei for his telescope.

In the 17th century, geology became firmly established among other sciences. They say that the term was coined by Ulysses Aldvandi or Mikkel Eschholt. The fossils discovered at that time caused serious controversy in the age of the earth. All the religious people insisted on 6000 years (as the Bible said).

This debate ended in 1785 when James Hutton declared that the Earth was much older. It was based on the erosion of rocks and the calculation of the time required for this. In the 18th century, scientists were divided into 2 camps. The former believed that the rocks were deposited by floods, while the latter complained about the fiery conditions. Hutton stood in firing position.

The first geological maps of the Earth appeared in the 19th century. The main work is “Principles of Geology”, published in 1830 by Charles Lyell. In the 20th century, age calculations became much easier thanks to radiometric dating (2 billion years). However, the study of tectonic plates has already led to the modern mark of 4.5 billion years.

The future of planet Earth

Our life depends on the behavior of the Sun. However, each star has its own evolutionary path. It is expected that in 3.5 billion years it will increase in volume by 40%. This will increase the flow of radiation, and the oceans may simply evaporate. Then the plants will die, and in a billion years all living things will disappear, and the constant average temperature will be fixed at around 70°C.

In 5 billion years, the Sun will transform into a red giant and shift our orbit by 1.7 AU.

If you look at the entire earth's history, then humanity is just a fleeting blip. However, the Earth remains the most important planet, home and unique place. One can only hope that we will have time to populate other planets outside our system before the critical period of solar development. Below you can explore a map of the Earth's surface. In addition, our website contains many beautiful high-resolution photos of the planet and places on Earth from space. Using online telescopes from the ISS and satellites, you can observe the planet for free in real time.

Click on the image to enlarge it