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Presentation on the topic: Earth is a planet in the solar system. Planets of our solar system

It is part of the solar system and is the third planet from the sun. It has a single satellite -. The position of the Earth and its satellite in the solar system determines many processes occurring on the Earth.

solar system

Included in the cluster of stars - the Milky Way Galaxy (from Greek word galaktikos - milky, milky). It stands out in the night sky as a wide pale band and, together with other galaxies, forms the Universe. Thus, our planet Earth is a part of the Universe and develops along with it according to its laws. The composition of the solar system, in addition to the sun, includes 8 planets, more than 60 of their satellites, over 5000 asteroids and many smaller objects - comets, space debris and space dust. All of them are held at a certain distance from the Sun by gravity. The sun is the center of our planetary system, the basis of life on Earth.

The planets of the solar system are spherical, revolve around their own axis and around the sun. The path of the planets around the Sun is called an orbit (from the Latin word orbita track, road). The orbits are close to circles in shape.

Geographic Consequences of the Shape and Size of the Earth

Spherical and its dimensions are important geographical importance. The huge mass of our planet - 6.6 hextillion tons (including 21 zero!) - determines the force of gravity that keeps the hearth on the surface of the planet and around it. With a smaller size of the Earth, its attraction would be very weak, the gases of the air would disperse into space. So, the force of lunar attraction is six times weaker than that of the earth, so the moon has almost no atmosphere and water. The larger size and mass of the planet would also change the composition of the air.

The spherical shape of the Earth determines the different amounts of sunlight and heat entering its surface in equal geographical latitudes.

Earth-Moon system

The Earth has a permanent satellite - the Moon, moving around it in orbit. The spherical shape of the Moon and its rather large dimensions make it possible to consider the Earth and the Moon as a binary planetary system with a common center of rotation near the earth's surface. The force of lunar attraction and the force arising from the mutual rotation of the Earth and the Moon lead to the formation of ebbs and flows on Earth.

Earth is a unique planet

The main feature of the Earth is that it is a planet of life. It was here that the necessary conditions for the existence and development of living organisms were formed. The atmosphere of our planet is not as dense as, for example, Venus, and passes a sufficient amount of sunlight. An invisible magnetic field appears in it, protecting it from cosmic radiation harmful to life. Only under terrestrial conditions is it possible for water to exist in three states - gaseous, solid and, of course, liquid. The first living organisms arose on Earth almost immediately with the advent of water. These were bacteria, including those producing oxygen. With the development of life, new, more complex organisms appeared. Plants that came to land changed the composition of the Earth's atmosphere, increasing the amount of oxygen in it.

The Earth is the third planet from the Sun and the largest of the terrestrial planets. However, it is only the fifth largest planet in terms of size and mass in the solar system, but, surprisingly, the densest of all the planets in the system (5.513 kg / m3). It is also noteworthy that the Earth is the only planet in the solar system that people themselves did not name after a mythological creature - its name comes from the old English word"ertha" which means soil.

Earth is thought to have formed sometime around 4.5 billion years ago, and is currently the only known planet where life is possible at all, and conditions are such that life literally teems on the planet.

Throughout human history, humans have sought to understand their home planet. However, the learning curve turned out to be very, very difficult, with lots of mistakes made along the way. For example, even before the existence of the ancient Romans, the world was understood as flat, not spherical. Second good example is the belief that the sun revolves around the earth. It wasn't until the sixteenth century, thanks to the work of Copernicus, that people learned that the earth was actually just a planet revolving around the sun.

Perhaps the most important discovery regarding our planet in the last two centuries is that the Earth is both a common and a unique place in the solar system. On the one hand, many of its characteristics are rather ordinary. Take, for example, the size of a planet, its internal and geological processes: Its internal structure is almost identical to the other three terrestrial planets in the solar system. Almost the same geological processes that form the surface take place on Earth, which are characteristic of similar planets and many planetary satellites. However, with all this, the Earth has just a huge number of absolutely unique characteristics that strikingly distinguish it from almost all the planets of the terrestrial group known today.

One of the necessary conditions for the existence of life on Earth without a doubt is its atmosphere. It is composed of approximately 78% nitrogen (N2), 21% oxygen (O2) and 1% argon. It also contains very small amounts of carbon dioxide (CO2) and other gases. It is noteworthy that nitrogen and oxygen are necessary for the creation of deoxyribonucleic acid (DNA) and the production of biological energy, without which life cannot exist. In addition, the oxygen present in the ozone layer of the atmosphere protects the surface of the planet and absorbs harmful solar radiation.

It is curious that a significant amount of oxygen present in the atmosphere is created on Earth. It is formed as a by-product of photosynthesis, when plants convert carbon dioxide from the atmosphere into oxygen. Essentially, this means that without plants, the amount of carbon dioxide in the atmosphere would be much higher, and the level of oxygen would be much lower. On the one hand, if the level of carbon dioxide rises, it is likely that the Earth will suffer from the greenhouse effect as on. On the other hand, if the percentage of carbon dioxide becomes even slightly lower, then a decrease in the greenhouse effect would lead to a sharp cooling. Thus, the current level of carbon dioxide contributes to an ideal range of comfortable temperatures from -88°C to 58°C.

When observing the Earth from space, the first thing that catches your eye is the oceans of liquid water. In terms of surface area, the oceans cover approximately 70% of the Earth, which is one of the most unique features of our planet.

Like the Earth's atmosphere, the presence of liquid water is a necessary criterion for sustaining life. Scientists believe that for the first time life on Earth arose 3.8 billion years ago and it was in the ocean, and the ability to move on land appeared in living beings much later.

Planetologists explain the presence of oceans on Earth in two ways. The first of these is the Earth itself. There is an assumption that during the formation of the Earth, the atmosphere of the planet was able to capture large volumes of water vapor. Over time, the planet's geological mechanisms, primarily its volcanic activity, released this water vapor into the atmosphere, after which, in the atmosphere, this vapor condensed and fell to the planet's surface in the form of liquid water. Another version suggests that the comets that fell to the Earth's surface in the past were the source of water, the ice that prevailed in their composition and formed the existing reservoirs on Earth.

Ground surface

Despite the fact that most of the Earth's surface is located under its oceans, the "dry" surface has many distinctive features. When comparing the Earth with other solid bodies in the solar system, its surface is strikingly different, since it does not have craters. According to planetary scientists, this does not mean that the Earth has escaped numerous impacts of small cosmic bodies, but rather indicates that evidence of such impacts has been erased. There may be many geological processes responsible for this, but the two most important are weathering and erosion. It is believed that in many respects it was the dual impact of these factors that influenced the erasure of traces of craters from the face of the Earth.

So weathering breaks surface structures into smaller pieces, not to mention the chemical and physical means of weathering. An example of chemical weathering is acid rain. An example of physical weathering is the abrasion of river beds caused by rocks contained in running water. The second mechanism, erosion, is essentially the impact on the relief by the movement of particles of water, ice, wind or earth. Thus, under the influence of weathering and erosion, impact craters on our planet were “erased”, due to which some relief features were formed.

Scientists also identify two geological mechanisms that, in their opinion, helped shape the surface of the Earth. The first such mechanism is volcanic activity - the process of release of magma (molten rock) from the bowels of the Earth through gaps in its crust. Possibly due to volcanic activity. Earth's crust was changed and islands were formed (a good example is Hawaiian Islands). The second mechanism determines mountain building or the formation of mountains as a result of compression of tectonic plates.

Structure of the planet Earth

Like other terrestrial planets, the Earth consists of three components: core, mantle and crust. Science now believes that the core of our planet consists of two separate layers: an inner core of solid nickel and iron, and an outer core of molten nickel and iron. At the same time, the mantle is a very dense and almost completely solid silicate rock - its thickness is approximately 2850 km. The crust is also composed of silicate rocks and the difference is in its thickness. While continental ranges of crust are 30 to 40 kilometers thick, oceanic crust is much thinner, only 6 to 11 kilometers.

Another one distinguishing feature Earth relative to other terrestrial planets is that its crust is divided into cold, rigid plates that rest on the hotter mantle below. In addition, these plates are in constant motion. Along their boundaries, as a rule, two processes are carried out at once, known as subduction and spreading. During subduction, two plates come into contact producing earthquakes and one plate runs over the other. The second process is separation, when two plates move away from each other.

Orbit and rotation of the Earth

The Earth takes approximately 365 days to make a complete orbit around the Sun. The length of our year is related to a large extent to the average orbital distance of the Earth, which is 1.50 x 10 to the power of 8 km. At this orbital distance, it takes on average about eight minutes and twenty seconds for sunlight to reach the Earth's surface.

With an orbital eccentricity of .0167, the Earth's orbit is one of the most circular in the entire solar system. This means that the difference between the Earth's perihelion and aphelion is relatively small. As a result of such a small difference, the intensity of sunlight on Earth remains almost the same all year round. However, the position of the Earth in its orbit determines this or that season.

The tilt of the Earth's axis is approximately 23.45°. At the same time, the Earth takes twenty-four hours to complete one revolution around its axis. This is the fastest rotation among the terrestrial planets, but slightly slower than all gas planets.

In the past, the Earth was considered the center of the universe. For 2000 years, ancient astronomers believed that the Earth was static, while others celestial bodies travel in circular orbits around it. They came to this conclusion by observing the apparent movement of the Sun and planets when viewed from the Earth. In 1543, Copernicus published his heliocentric model of the solar system, in which the sun is at the center of our solar system.

Earth is the only planet in the system not named after mythological gods or goddesses (the other seven planets in the solar system were named after Roman gods or goddesses). This refers to the five planets visible to the naked eye: Mercury, Venus, Mars, Jupiter and Saturn. The same approach with the names of the ancient Roman gods was used after the discovery of Uranus and Neptune. The very same word "Earth" comes from the old English word "ertha" meaning soil.

Earth is the densest planet in the solar system. The density of the Earth is different in each layer of the planet (the core, for example, is denser than the earth's crust). The average density of the planet is about 5.52 grams per cubic centimeter.

The gravitational interaction between the Earth and causes the tides on the Earth. It is believed that the Moon is blocked by the tidal forces of the Earth, so its period of rotation coincides with the Earth's and it always faces our planet with the same side.

Abstract on the topic

"Earth is a planet in the solar system"

1. The structure and composition of the solar system. Two groups of planets

2. Terrestrial planets. Earth-Moon system

3. Earth

4. Ancient and modern explorations of the Earth

5. Exploring the Earth from space

6. Origin of life on earth

7. Earth's only satellite is the Moon

Conclusion

1. The structure and composition of the solar system. two groups of planets.

Our Earth is one of the 8 major planets revolving around the Sun. It is in the Sun that the main part of the matter of the solar system is concentrated. The mass of the Sun is 750 times the mass of all the planets and 330,000 times the mass of the Earth. Under the influence of the force of its attraction, the planets and all other bodies of the solar system move around the sun.

The distances between the Sun and the planets are many times greater than their size, and it is almost impossible to draw such a diagram that would observe a single scale for the Sun, planets and the distances between them. The diameter of the Sun is 109 times larger than the Earth, and the distance between them is about the same number of times the diameter of the Sun. In addition, the distance from the Sun to the last planet of the solar system (Neptune) is 30 times greater than the distance to the Earth. If we depict our planet as a circle with a diameter of 1 mm, then the Sun will be at a distance of about 11 m from the Earth, and its diameter will be approximately 11 cm. The orbit of Neptune will be shown as a circle with a radius of 330 m. drawing from the book of Copernicus "On the circulation of the celestial circles" with other, very approximate proportions.

According to physical characteristics, large planets are divided into two groups. One of them - the planets of the terrestrial group - is the Earth and similar Mercury, Venus and Mars. The second includes the giant planets: Jupiter, Saturn, Uranus and Neptune. Until 2006, Pluto was considered the largest planet farthest from the Sun. Now, together with other objects of similar size - long-known large asteroids (see § 4) and objects discovered on the outskirts of the solar system - it is among the dwarf planets.

The division of the planets into groups can be traced by three characteristics (mass, pressure, rotation), but most clearly by density. Planets belonging to the same group differ insignificantly in density, while the average density of terrestrial planets is about 5 times greater than the average density of giant planets (see Table 1).

Most of the mass of the terrestrial planets is in solid matter. The Earth and other planets of the terrestrial group consist of oxides and other compounds of heavy chemical elements: iron, magnesium, aluminum and other metals, as well as silicon and other non-metals. The four most abundant elements in the solid shell of our planet (lithosphere) - iron, oxygen, silicon and magnesium - account for over 90% of its mass.

The low density of the giant planets (for Saturn it is less than the density of water) is explained by the fact that they consist mainly of hydrogen and helium, which are predominantly in gaseous and liquid states. The atmospheres of these planets also contain hydrogen compounds - methane and ammonia. Differences between the planets of the two groups arose already at the stage of their formation (see § 5).

Of the giant planets, Jupiter is best studied, on which, even in a small school telescope, numerous dark and light stripes are visible, stretching parallel to the planet's equator. This is what cloud formations look like in its atmosphere, the temperature of which is only -140 ° C, and the pressure is about the same as at the surface of the Earth. The reddish-brown color of the bands is apparently due to the fact that, in addition to the ammonia crystals that form the basis of the clouds, they contain various impurities. The images taken by spacecraft show traces of intense and sometimes persistent atmospheric processes. So, for over 350 years, an atmospheric vortex, called the Great Red Spot, has been observed on Jupiter. In the earth's atmosphere, cyclones and anticyclones exist on average for about a week. Atmospheric currents and clouds have been recorded by spacecraft on other giant planets, although they are less developed than on Jupiter.

Structure. It is assumed that as it approaches the center of the giant planets, due to an increase in pressure, hydrogen should pass from a gaseous to a gaseous state, in which its gaseous and liquid phases coexist. At the center of Jupiter, the pressure is millions of times higher than the atmospheric pressure that exists on Earth, and hydrogen acquires the properties characteristic of metals. In the depths of Jupiter, metallic hydrogen, together with silicates and metals, forms a core, which is approximately 1.5 times larger in size and 10–15 times larger in mass than the Earth.

Weight. Any of the giant planets exceeds in mass all the terrestrial planets combined. The largest planet in the solar system - Jupiter is larger than the largest planet of the terrestrial group - the Earth by 11 times in diameter and more than 300 times in mass.

Rotation. The differences between the planets of the two groups are also manifested in the fact that the giant planets rotate faster around the axis, and in the number of satellites: there are only 3 satellites for 4 terrestrial planets, more than 120 for 4 giant planets. All these satellites consist of the same substances, like the planets of the terrestrial group - silicates, oxides and sulfides of metals, etc., as well as water (or water-ammonia) ice. In addition to numerous craters of meteorite origin, tectonic faults and cracks in their crust or ice cover have been found on the surface of many satellites. The discovery of about a dozen active volcanoes on the closest satellite to Jupiter, Io, turned out to be the most surprising. This is the first reliable observation of terrestrial-type volcanic activity outside our planet.

In addition to satellites, giant planets also have rings, which are clusters of small bodies. They are so small that they cannot be seen individually. Due to their circulation around the planet, the rings appear to be continuous, although both the surface of the planet and the stars shine through the rings of Saturn, for example. The rings are located in close proximity to the planet, where large satellites cannot exist.

2. Planets of the terrestrial group. Earth-Moon system

Due to the presence of a satellite, the Moon, the Earth is often called a double planet. This emphasizes both the commonality of their origin and the rare ratio of the masses of the planet and its satellite: the Moon is only 81 times smaller than the Earth.

Sufficiently detailed information will be given about the nature of the Earth in subsequent chapters of the textbook. Therefore, here we will talk about the rest of the planets of the terrestrial group, comparing them with ours, and about the Moon, which, although it is only a satellite of the Earth, by its nature belongs to planetary-type bodies.

Despite the common origin, the nature of the moon is significantly different from the earth, which is determined by its mass and size. Due to the fact that the force of gravity on the surface of the Moon is 6 times less than on the surface of the Earth, it is much easier for gas molecules to leave the Moon. Therefore, our natural satellite is devoid of a noticeable atmosphere and hydrosphere.

The absence of an atmosphere and slow rotation around the axis (a day on the Moon is equal to an Earth month) lead to the fact that during the day the surface of the Moon heats up to 120 ° C, and cools down to -170 ° C at night. Due to the absence of an atmosphere, the lunar surface is subject to constant “bombardment” by meteorites and smaller micrometeorites that fall on it at cosmic speeds (tens of kilometers per second). As a result, the entire Moon is covered with a layer of finely divided substance - regolith. As described by American astronauts who have been on the Moon, and as photographs of the traces of lunar rovers show, in terms of its physical and mechanical properties (particle sizes, strength, etc.), regolith is similar to wet sand.

When large bodies fall on the surface of the Moon, craters up to 200 km in diameter are formed. Craters meter and even centimeter in diameter are clearly visible in the panoramas of the lunar surface obtained from spacecraft.

Under laboratory conditions, samples of rocks delivered by our automatic stations "Luna" and American astronauts who visited the Moon on the Apollo spacecraft were studied in detail. This made it possible to obtain more complete information than in the analysis of the rocks of Mars and Venus, which was carried out directly on the surface of these planets. Lunar rocks are similar in composition to terrestrial rocks such as basalts, norites, and anorthosites. The set of minerals in lunar rocks is poorer than in terrestrial, but richer than in meteorites. Our satellite does not have and never had a hydrosphere or an atmosphere of the same composition as on Earth. Therefore, there are no minerals that can be formed in aquatic environment and in the presence of free oxygen. Lunar rocks are depleted in volatile elements compared to terrestrial ones, but they are distinguished by an increased content of iron and aluminum oxides, and in some cases titanium, potassium, rare earth elements and phosphorus. No signs of life, even in the form of microorganisms or organic compounds, have been found on the Moon.

The light areas of the Moon - the "continents" and the darker ones - the "seas" differ not only in appearance, but also in relief, geological history and the chemical composition of the substance covering them. On the younger surface of the "seas", covered with solidified lava, there are fewer craters than on the older surface of the "continents". IN various parts On the moon, such relief forms as cracks are noticeable, along which the crust is shifted vertically and horizontally. In this case, only fault-type mountains are formed, and there are no folded mountains, so typical for our planet, on the Moon.

The absence of erosion and weathering processes on the Moon allows us to consider it a kind of geological reserve, where for millions and billions of years all the landforms that have arisen during this time have been preserved. Thus, the study of the Moon makes it possible to understand the geological processes that took place on Earth in the distant past, of which no traces remain on our planet.

3. Earth.

Earth is the third planet from the Sun in the solar system. It revolves around the star at an average distance of 149.6 million km over a period of 365.24 days.

The Earth has a satellite - the Moon, which revolves around the Sun at an average distance of 384,400 km. The inclination of the earth's axis to the plane of the ecliptic is 66033`22``. The period of rotation of the planet around its axis is 23 hours 56 minutes 4.1 seconds. Rotation around its axis causes the change of day and night, and the tilt of the axis and circulation around the Sun - the change of seasons. The shape of the Earth is a geoid, approximately a triaxial ellipsoid, a spheroid. 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, the volume is 1.083 * 1012 km², the average density is 5518 kg / m³. The mass of the Earth is 5976 * 1021 kg.

The earth has magnetic and electric fields. The gravitational field of the Earth determines its spherical shape and the existence of the atmosphere. According to modern cosmogonic concepts, the Earth was formed about 4.7 billion years ago from the gaseous matter scattered in the protosolar system. As a result of the differentiation of matter, the Earth, under the influence of its gravitational field, under the conditions of heating of the earth's interior, arose and developed different in chemical composition, state of aggregation and physical properties of the shell - the geosphere: core (in the center), mantle, earth's crust, hydrosphere, atmosphere, 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 part of the core are solid (the outer part of the core is considered liquid). From the surface of the Earth to the center, pressure, density and temperature increase.

The pressure in the center of the planet is 3.6 * 1011 Pa, the density is about 12.5 * 103 kg / m³, the temperature ranges from 50000ºС to 60000ºС.

The main types of the earth's crust are continental and oceanic; in the transition zone from the mainland to the ocean, an intermediate crust is developed.

Most of the Earth is occupied by the World Ocean (361.1 million km²; 70.8%), the land is 149.1 million km² (29.2%), and forms six continents and islands. It rises above sea level by an average of 875 m ( highest altitude 8848 m - Mount Chomolungma), mountains occupy more than 1/3 of the land surface. Deserts cover about 20% of the land surface, forests - about 30%, glaciers - over 10%. The average depth of the world ocean is about 3800 m (the greatest depth is 11020 m - the Mariana Trench (trough) in the Pacific Ocean). The volume of water on the planet is 1370 million km³, the average salinity is 35 g/l. The atmosphere of the Earth, the total mass of which is 5.15 * 1015 tons, consists of air - a mixture of mainly nitrogen (78.08%) and oxygen (20.95%), the rest is water vapor, carbon dioxide, as well as inert and other gases. The maximum land surface temperature is 570º-580º C (in the tropical deserts of Africa and North America), the minimum is about -900º C (in the central regions of Antarctica). Earth formation and First stage its developments belong to pregeological history. The absolute age of the most ancient rocks is over 3.5 billion years. The geological history of the Earth is divided into two unequal stages: the Precambrian, which occupies approximately 5/6 of the entire geological chronology (about 3 billion years) and the 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, and the development of the biosphere began. The totality of all living organisms inhabiting it, the so-called living matter Earth, had a significant impact on the development of the atmosphere, hydrosphere and sedimentary shell. A new factor that has a powerful influence on the biosphere is the production activity of man, who appeared on Earth less than 3 million years ago. The high growth rate of the world's population (275 million people in 1000, 1.6 billion people in 1900 and about 6.3 billion people in 1995) and the growing influence human society brought problems to the natural environment rational use all natural resources and nature protection.

4. Ancient and modern studies of the Earth.

For the first time, the ancient Greek mathematician and astronomer Eratosthenes managed to obtain fairly accurate dimensions of our planet in the 1st century BC (an accuracy of about 1.3%). Eratosthenes discovered that at noon on the longest day of summer, when the Sun is in the sky of the city of Aswan highest position and its rays fall vertically, in Alexandria at the same time the zenith distance of the Sun is 1/50 of the circle. Knowing the distance from Aswan to Alexandria, he was able to calculate the radius of the Earth, which, according to his calculations, was 6290 km. An equally significant contribution to astronomy was made by the Muslim astronomer and mathematician Biruni, who lived in the 10th-11th century AD. e. Despite the fact that he used the geocentric system, he was able to quite accurately determine the size of the Earth and the inclination of the equator to the ecliptic. Although the sizes of the planets were determined by him, but with big mistake; the only size he determined relatively accurately is the size of the moon.

In the 15th century, Copernicus put forward the heliocentric theory of the structure of the world. The theory, as is known, had no development for quite a long time, as it was persecuted by the church. The system was finally refined by I. Kepler at the end of the 16th century. Kepler also discovered the laws of planetary motion and calculated the eccentricities of their orbits, theoretically created a model of a telescope. Galileo, who lived somewhat later than Kepler, constructed a telescope with a magnification of 34.6 times, which allowed him to estimate even the height of the mountains on the moon. He also discovered a characteristic difference when observing stars and planets through a telescope: the clarity of the appearance and shape of the planets was much greater, and he also discovered several new stars. For almost 2000 years, astronomers believed that the distance from the Earth to the Sun is equal to 1200 Earth distances, i.e. making a mistake about 20 times! For the first time, these data were refined only in late XVII century as 140 million km, i.e. with an error of 6.3% by the astronomers Cassini and Richet. They also determined the speed of light as 215 km / s, which was a significant breakthrough in astronomy, since they previously believed that the speed of light was infinite. Around the same time, Newton discovered the law gravity, and the decomposition of light into a spectrum, which marked the beginning of spectral analysis several centuries later.

The Earth seems to us so huge, so reliable and means so much to us that we do not notice her secondary position in the family of planets. The only weak consolation is that the Earth is the largest of the terrestrial planets. In addition, it has an atmosphere of medium power, a significant part of the earth's surface is covered with a thin heterogeneous layer of water. And around it revolves a majestic satellite, the diameter of which is equal to a quarter of the earth's diameter. However, these arguments are hardly sufficient to support our cosmic conceit. Tiny in astronomical terms, the Earth is our home planet and therefore deserves the most careful study. After the painstaking and hard work of dozens of generations of scientists, it was irrefutably proven that the Earth is not at all the “center of the universe”, but the most ordinary planet, i.e. cold ball moving around the sun. According to Kepler's laws, the Earth revolves around the Sun at a variable speed in a slightly elongated ellipse. It is closest to the sun in early January, when winter reigns in the Northern Hemisphere, and farthest away in early July, when we have summer. The difference in the distance of the Earth from the Sun between January and July is about 5 million km. Therefore, winters in the northern hemisphere are slightly warmer than in the southern, and summers, on the contrary, are slightly cooler. This is most clearly felt in the Arctic and Antarctica. The ellipticity of the Earth's orbit has only an indirect and very insignificant influence on the nature of the seasons. The reason for the change of seasons lies in the tilt of the earth's axis. The axis of rotation of the Earth is located at an angle of 66.5º to the plane of its movement around the Sun. For most practical problems, it can be assumed that the Earth's axis of rotation always moves in space parallel to itself. In fact, the axis of rotation of the Earth describes a small circle on the celestial sphere, making one complete revolution in 26 thousand years. In the next hundreds of years, the north pole of the world will be located not far from the Polar Star, then it will begin to move away from it, and the name of the last star in the handle of the Ursa Minor bucket - Polaris - will lose its meaning. In 12 thousand years, the celestial pole will approach the brightest star in the northern sky - Vega from the constellation Lyra. The described phenomenon is called the precession of the Earth's axis of rotation. The phenomenon of precession was already discovered by Hipparchus, who compared the positions of the stars in the catalog with the star catalog of Aristillus and Timocharis compiled long before him. Comparison of catalogs indicated to Hipparchus the slow movement of the axis of the world.

There are three outer shells of the Earth: the lithosphere, hydrosphere and atmosphere. The lithosphere is understood as the upper solid cover of the planet, which serves as the bed of the ocean, and on the continents coincides with the land. The hydrosphere is groundwater, the waters of rivers, lakes, seas and, finally, the oceans. Water covers 71% of the entire surface of the Earth. The average depth of the World Ocean is 3900 m.

5. Exploring the Earth from space

Man first appreciated the role of satellites in monitoring the state of agricultural land, forests and other natural resources of the Earth only a few years after the onset of the space age. The beginning was laid in 1960, when with the help of meteorological satellites "Tiros" map-like outlines of the globe were obtained, lying under the clouds. These first black-and-white TV images gave very little insight into human activity, and yet it was a first step. Soon new technical means were developed that made it possible to improve the quality of observations. Information was extracted from multispectral images in the visible and infrared (IR) regions of the spectrum. The first satellites designed to make the most of these opportunities were the Landsat. For example, the Landsat-D satellite, the fourth in a series, observed the Earth from an altitude of more than 640 km using advanced sensitive instruments, which allowed consumers to receive much more detailed and timely information. One of the first areas of application of images of the earth's surface was cartography. In the pre-satellite era, maps of many areas, even in the developed regions of the world, were inaccurate. The Landsat images have corrected and updated some of the existing maps of the United States. In the mid-70s, NASA, the ministry Agriculture The United States decided to demonstrate the capabilities of the satellite system in forecasting the most important wheat crop. Satellite observations, which turned out to be extremely accurate, were later extended to other agricultural crops. The use of satellite information has revealed its undeniable advantages in assessing the volume of timber in the vast territories of any country. It became possible to manage the process of deforestation and, if necessary, to give recommendations on changing the contours of the deforestation area from the point of view of the best preservation of the forest. Thanks to satellite images, it is also possible to quickly assess borders forest fires, especially "crown-shaped", characteristic of the western regions of North America, as well as the regions of Primorye and the southern regions of Eastern Siberia in Russia.

Of great importance for humanity as a whole is the ability to observe almost continuously over the expanses of the World Ocean. It is above the depths of ocean water that monstrous forces are born of hurricanes and typhoons, bringing numerous victims and destruction to the inhabitants of the coast. Early warning to the public is often critical to saving the lives of tens of thousands of people. Determining the stocks of fish and other seafood is also of great practical importance. Ocean currents often curve, change course and size. For example, El Nino, a warm current in a southerly direction off the coast of Ecuador in some years can spread along the coast of Peru up to 12º S. When this happens, plankton and fish die in huge numbers, causing irreparable damage to the fisheries of many countries, including Russia. Large concentrations of unicellular marine organisms increase the mortality of fish, possibly due to the toxins they contain. Satellite observation helps to identify the “whims” of such currents and provide useful information to those who need it. According to some estimates by Russian and American scientists, the fuel savings, combined with the "extra catch" due to the use of information from satellites obtained in the infrared range, yields an annual profit of $ 2.44 million. The use of satellites for survey purposes has facilitated the task of plotting the course of ships .

6. The emergence of life on Earth

The emergence of living matter on Earth was preceded by a rather long and complex evolution of the chemical composition of the atmosphere, which ultimately led to the formation of a number of organic molecules. These molecules later served as a kind of “bricks” for the formation of living matter. According to modern data, the planets are formed from a primary gas-dust cloud, the chemical composition of which is similar to the chemical composition of the Sun and stars, their initial atmosphere consisted mainly of the simplest compounds of hydrogen - the most common element in space. Most of all there were molecules of hydrogen, ammonia, water and methane. In addition, the primary atmosphere should have been rich in inert gases - primarily helium and neon. At present, there are few noble gases on Earth, since they once dissipated (evaporated) into interplanetary space, like many hydrogen-containing compounds. However, a decisive role in establishing the composition of the earth's atmosphere was played by plant photosynthesis, in which oxygen is released. It is possible that some, and perhaps even significant, amount organic matter was brought to Earth by meteorites and possibly even comets. Some meteorites are quite rich in organic compounds. It is estimated that over 2 billion years meteorites could bring to Earth from 108 to 1012 tons of such substances. Also, organic compounds can occur in small quantities as a result of volcanic activity, meteorite impacts, lightning, due to the radioactive decay of some elements. There are fairly reliable geological data indicating that already 3.5 billion years ago the Earth's atmosphere was rich in oxygen. On the other hand, the age of the earth's crust is estimated by geologists at 4.5 billion years. Life must have originated on Earth before the atmosphere became rich in oxygen, since the latter is mainly a product of the vital activity of plants. According to a recent estimate by the American specialist in planetary astronomy Sagan, life on Earth arose 4.0-4.4 billion years ago. The mechanism of the complication of the structure of organic substances and the appearance in them of the properties inherent in living matter has not yet been sufficiently studied. But it is already clear that such processes last for billions of years.

Any complex combination of amino acids and other organic compounds is not yet a living organism. It can, of course, be assumed that under some exceptional circumstances, somewhere on Earth, a certain “praDNA” arose, which served as the beginning of all living things. This is hardly the case if the hypothetical “praDNA” was similar to the modern one. The fact is that modern DNA itself is completely helpless. It can function only in the presence of enzyme proteins. To think that purely by chance, by “shaking up” individual proteins - polyatomic molecules, such a complex machine as “praDNA” and the complex of protein-enzymes necessary for its functioning could arise - this means believing in miracles. However, it can be assumed that DNA and RNA molecules originated from a more primitive molecule. For the first primitive living organisms formed on the planet, high doses of radiation can be mortal danger, since mutations will occur so quickly that natural selection will not keep up with them.

The following question deserves attention: why does life on Earth not arise from non-living matter in our time? This can only be explained by the fact that the previously arisen life will not give an opportunity for a new birth of life. Microorganisms and viruses will literally eat the first sprouts of new life. We cannot completely exclude the possibility that life on Earth arose by chance. There is another circumstance that may be worth paying attention to. It is well known that all “living” proteins consist of 22 amino acids, while more than 100 amino acids are known in total. It is not entirely clear how these acids differ from their other “brothers”. Is there some deep connection between the origin of life and this amazing phenomenon? If life on Earth arose by chance, then life in the Universe is a rare phenomenon. For a given planet (like, for example, our Earth), the emergence of a special form of highly organized matter, which we call "life", is an accident. But in the vast expanses of the universe, life arising in this way should be a natural phenomenon. It must be noted again that central problem the emergence of life on Earth - the explanation of the qualitative leap from "non-living" to "living" - is still far from clear. No wonder one of the founders of modern molecular biology, Professor Crick, at the Byurakan Symposium on the Problem of Extraterrestrial Civilizations in September 1971, said: “We do not see a path from the primordial soup to natural selection. It can be concluded that the origin of life is a miracle, but this only testifies to our ignorance.”

8. The only satellite of the Earth is the Moon.

Long gone are the days when people believed that the mysterious forces of the moon had an impact on their daily lives. But the Moon does have a variety of influences on the Earth, which are due to the simple laws of physics and, above all, dynamics. The most amazing feature of the motion of the Moon is that the speed of its rotation around its axis coincides with the average angular velocity of revolution around the Earth. Therefore, the Moon always faces the Earth with the same hemisphere. Since the Moon is the nearest celestial body, its distance from the Earth is known with the greatest accuracy, up to several centimeters from measurements using lasers and laser rangefinders. The smallest distance between the centers of the Earth and the Moon is 356,410 km. The greatest distance of the Moon from the Earth reaches 406,700 km, and the average distance is 384,401 km. Earth atmosphere bends light rays to such an extent that the entire moon (or sun) can be seen before sunrise or after sunset. The fact is that the refraction of light rays entering the atmosphere from airless space is about 0,

5º, i.e. equal to the apparent angular diameter of the moon.

Thus, when the upper edge of the true Moon is just below the horizon, the entire Moon is visible above the horizon. Another surprising result was obtained from tidal experiments. It turns out that the Earth is an elastic ball. Prior to these experiments, it was commonly believed that the Earth was viscous, like molasses or molten glass; with slight distortions, it would probably have to keep them or slowly return to its original form under the action of weak restoring forces. Experiments have shown that the Earth as a whole is given tidal forces and immediately returns to its original form after the cessation of their action. Thus, the Earth is not only harder than steel, but also more resilient.

Conclusion

We got acquainted with state of the art our planet. The future of our planet, and indeed the entire planetary system, if nothing unforeseen happens, seems clear. The probability that the established order of the planets will be disturbed by some wandering star is small, even within a few billion years.

In the near future, one should not expect strong changes in the flow of solar energy. Likely to repeat ice ages. A person is able to change the climate, but in doing so, he can make a mistake. The continents will rise and fall in subsequent epochs, but we hope that the processes will be slow. Massive meteorite impacts are possible from time to time. But basically, the planet Earth will retain its modern appearance.

Space has attracted people's attention for a long time. Astronomers began to study the planets of the solar system in the Middle Ages, looking at them through primitive telescopes. But a thorough classification, description of the features of the structure and movement of celestial bodies became possible only in the 20th century. With the advent of powerful equipment equipped with last word observatories and spaceships, several previously unknown objects were discovered. Now each student can list all the planets of the solar system in order. Almost all of them have been landed by a space probe, and so far man has only been to the Moon.

What is the solar system

The universe is huge and includes many galaxies. Our solar system is part of a galaxy with over 100 billion stars. But there are very few that look like the Sun. Basically, they are all red dwarfs, which are smaller in size and do not shine as brightly. Scientists have suggested that the solar system was formed after the emergence of the sun. Its huge field of attraction captured a gas-dust cloud, from which, as a result of gradual cooling, particles of solid matter were formed. Over time, celestial bodies formed from them. It is believed that the Sun is now in the middle of its life path, therefore, it will exist, as well as all celestial bodies dependent on it, for several billion more years. Near space has been studied by astronomers for a long time, and any person knows what planets of the solar system exist. Photos of them, taken from space satellites, can be found on the pages of various information resources dedicated to this topic. All celestial bodies are held by the Sun's strong gravitational field, which makes up over 99% of the solar system's volume. Large celestial bodies revolve around the star and around their axis in one direction and in one plane, which is called the plane of the ecliptic.

Solar system planets in order

In modern astronomy, it is customary to consider celestial bodies, starting from the Sun. In the 20th century, a classification was created, which includes 9 planets of the solar system. But recent space exploration and the latest discoveries have prompted scientists to revise many positions in astronomy. And in 2006, at the international congress, due to its small size (a dwarf, not exceeding three thousand km in diameter), Pluto was excluded from the number of classical planets, and eight of them remained. Now the structure of our solar system has taken on a symmetrical, slender appearance. It includes four terrestrial planets: Mercury, Venus, Earth and Mars, then comes the asteroid belt, followed by four giant planets: Jupiter, Saturn, Uranus and Neptune. On the outskirts of the solar system also passes which scientists called the Kuiper belt. This is where Pluto is located. These places are still little studied because of their remoteness from the Sun.

Features of the terrestrial planets

What makes it possible to attribute these celestial bodies to one group? We list the main characteristics of the inner planets:

relatively small size;
hard surface, high density and similar composition (oxygen, silicon, aluminum, iron, magnesium and other heavy elements);
the presence of an atmosphere;
the same structure: a core of iron with nickel impurities, a mantle consisting of silicates, and a crust of silicate rocks (except for Mercury - it has no crust);
a small number of satellites - only 3 for four planets;
rather weak magnetic field.

Features of the giant planets

As for the outer planets, or gas giants, they have the following similar characteristics:

large size and weight;
they do not have a solid surface and are composed of gases, mainly helium and hydrogen (which is why they are also called gas giants);
a liquid core consisting of metallic hydrogen;
high rotation speed;
a strong magnetic field, which explains the unusual nature of many processes occurring on them;
there are 98 satellites in this group, most of which belong to Jupiter;
The most characteristic feature of gas giants is the presence of rings. All four planets have them, although they are not always noticeable.

The first planet is Mercury

It is located closest to the Sun. Therefore, from its surface, the luminary looks three times larger than from the Earth. This also explains the strong temperature fluctuations: from -180 to +430 degrees. Mercury is moving very fast in its orbit. Maybe that's why it got such a name, because in Greek mythology Mercury is the messenger of the gods. There is almost no atmosphere here, and the sky is always black, but the Sun shines very brightly. However, there are places at the poles where its rays never hit. This phenomenon can be explained by the tilt of the axis of rotation. No water was found on the surface. This circumstance, as well as the anomalously high daytime temperature (as well as the low nighttime temperature) fully explain the fact that there is no life on the planet.

Venus

If we study the planets of the solar system in order, then the second one is Venus. People could observe her in the sky in ancient times, but since she was shown only in the morning and in the evening, it was believed that these were 2 different objects. By the way, our Slavic ancestors called her Flicker. It is the third brightest object in our solar system. Formerly people they called it the morning and evening star, because it is best seen before sunrise and sunset. Venus and Earth are very similar in structure, composition, size and gravity. Around its axis, this planet moves very slowly, making a complete revolution in 243.02 Earth days. Of course, the conditions on Venus are very different from those on Earth. It is twice as close to the Sun, so it is very hot there. The high temperature is also explained by the fact that thick clouds of sulfuric acid and an atmosphere of carbon dioxide create on the planet Greenhouse effect. In addition, the pressure at the surface is 95 times greater than on Earth. Therefore, the first ship that visited Venus in the 70s of the 20th century survived there for no more than an hour. A feature of the planet is also the fact that it rotates in the opposite direction, compared to most planets. Astronomers know nothing more about this celestial object yet.

Third planet from the Sun

The only place in the solar system, and indeed in the entire universe known to astronomers, where life exists, is the Earth. In the terrestrial group, it has the largest dimensions. What else is her

The largest gravity among the terrestrial planets.
Very strong magnetic field.
High density.
It is the only one among all the planets that has a hydrosphere, which contributed to the formation of life.
It has the largest, in comparison with its size, satellite, which stabilizes its tilt relative to the Sun and affects natural processes.

The planet Mars

It is one of the smallest planets in our Galaxy. If we consider the planets of the solar system in order, then Mars is the fourth from the Sun. Its atmosphere is very rarefied, and the pressure on the surface is almost 200 times less than on Earth. For the same reason, very strong temperature drops are observed. The planet Mars is little studied, although it has long attracted the attention of people. According to scientists, this is the only celestial body on which life could exist. After all, in the past there was water on the surface of the planet. This conclusion can be drawn from the fact that there are large ice caps at the poles, and the surface is covered with many furrows, which could be dried up river beds. In addition, there are some minerals on Mars that can only be formed in the presence of water. Another feature of the fourth planet is the presence of two satellites. Their unusualness is that Phobos gradually slows down its rotation and approaches the planet, while Deimos, on the contrary, moves away.

What is Jupiter famous for?

The fifth planet is the largest. 1300 Earths would fit in the volume of Jupiter, and its mass is 317 times more than the earth. Like all gas giants, its structure is hydrogen-helium, reminiscent of the composition of stars. Jupiter is the most interesting planet that has many characteristic features:

it is the third brightest celestial body after the Moon and Venus;
Jupiter has the strongest magnetic field of all the planets;
it completes a full rotation around its axis in just 10 earth hours - faster than other planets;
an interesting feature of Jupiter is a large red spot - this is how an atmospheric vortex is visible from the Earth, rotating counterclockwise;
like all giant planets, it has rings, though not as bright as those of Saturn;
this planet has the largest number of satellites. He has 63 of them. The most famous are Europa, on which water was found, Ganymede - the largest satellite of the planet Jupiter, as well as Io and Calisto;
another feature of the planet is that in the shade the surface temperature is higher than in places illuminated by the Sun.

Planet Saturn

This is the second largest gas giant, also named after the ancient god. It consists of hydrogen and helium, but traces of methane, ammonia and water have been found on its surface. Scientists have found that Saturn is the most rarefied planet. Its density is less than that of water. This gas giant rotates very quickly - it completes one revolution in 10 Earth hours, as a result of which the planet is flattened from the sides. Huge speeds on Saturn and near the wind - up to 2000 kilometers per hour. It's more than the speed of sound. Saturn has another distinguishing feature- he keeps 60 satellites in his field of attraction. The largest of them - Titan - is the second largest in the entire solar system. The uniqueness of this object lies in the fact that, exploring its surface, scientists first discovered a celestial body with conditions similar to those that existed on Earth about 4 billion years ago. But the most important feature of Saturn is the presence of bright rings. They encircle the planet around the equator and reflect more light than itself. Four is the most amazing phenomenon in the solar system. Unusually, the inner rings move faster than the outer ones.

- Uranus

So, we continue to consider the planets of the solar system in order. The seventh planet from the Sun is Uranus. It is the coldest of all - the temperature drops to -224 ° C. In addition, scientists did not find metallic hydrogen in its composition, but found modified ice. Because Uranus is classified as a separate category of ice giants. An amazing feature of this celestial body is that it rotates while lying on its side. The change of seasons on the planet is also unusual: winter reigns there for 42 Earth years, and the Sun does not appear at all, summer also lasts 42 years, and the Sun does not set at this time. In spring and autumn, the luminary appears every 9 hours. Like all giant planets, Uranus has rings and many satellites. As many as 13 rings revolve around it, but they are not as bright as those of Saturn, and the planet holds only 27 satellites. If we compare Uranus with the Earth, then it is 4 times larger than it, 14 times heavier and is located at a distance from the Sun, in 19 times greater than the path to the luminary from our planet.

Neptune: the invisible planet

After Pluto was excluded from the number of planets, Neptune became the last from the Sun in the system. It is located 30 times farther from the star than the Earth, and is not visible from our planet even through a telescope. Scientists discovered it, so to speak, by chance: observing the peculiarities of the movement of the planets closest to it and their satellites, they concluded that there must be another large celestial body beyond the orbit of Uranus. After discovery and research, it turned out interesting features this planet:

due to the presence of a large amount of methane in the atmosphere, the color of the planet from space appears blue-green;
Neptune's orbit is almost perfectly circular;
the planet rotates very slowly - it completes one circle in 165 years;
Neptune is 4 times larger than the Earth and 17 times heavier, but the force of attraction is almost the same as on our planet;
the largest of the 13 moons of this giant is Triton. It is always turned to the planet on one side and slowly approaches it. Based on these signs, scientists have suggested that it was captured by Neptune's gravity.

In the entire galaxy, the Milky Way is about a hundred billion planets. So far, scientists cannot even study some of them. But the number of planets in the solar system is known to almost all people on Earth. True, in the 21st century, interest in astronomy has faded a little, but even children know the name of the planets of the solar system.

Planets are celestial bodies that revolve around a star. They, unlike stars, do not emit light and heat, but shine with the reflected light of the star to which they belong. The shape of the planets is close to spherical. At present, only the planets of the solar system are reliably known, but the presence of planets in other stars is very likely.

Gilbert expressed a hypothesis about terrestrial magnetism: the Earth is a large spherical magnet, the poles of which are located near the geographic poles. He substantiated his hypothesis with the following experience: if you bring a magnetic needle closer to the surface of a large ball made of a natural magnet, then it always sets in a certain direction, like a compass needle on Earth. Naidysh V.M. 2004 KSE

According to physical characteristics, large planets are divided into two groups. One of them - the planets of the terrestrial group - is made up of the Earth and Mercury, Venus and Mars similar to it. The second includes the giant planets: Jupiter, Saturn, Uranus and Neptune. Until 2006, Pluto was considered the largest planet farthest from the Sun. Now he, along with other objects of similar size - long-known large asteroids and objects found on the outskirts of the solar system - is among the dwarf planets.

The division of the planets into groups can be traced according to three characteristics (mass, pressure, rotation), but most clearly - in terms of density. Planets belonging to the same group differ insignificantly in density, while the average density of the terrestrial planets is about 5 times greater than the average density of the giant planets.

The Earth ranks fifth in size and mass among the large planets, but of the terrestrial planets, which includes Mercury, Venus, Earth and Mars, it is the largest. The most important difference between the Earth and other planets of the solar system is the existence of life on it, which reached its highest, intelligent form with the advent of man. The conditions for the development of life on the bodies of the solar system closest to the Earth are unfavorable; habitable bodies outside the latter have not yet been discovered either. However, life is a natural stage in the development of matter, therefore the Earth cannot be considered the only inhabited cosmic body of the Universe, and terrestrial forms of life are its only possible forms.

According to modern cosmogonic concepts, the Earth was formed approximately 4.5 billion years ago by gravitational condensation from gas and dust scattered in the circumsolar space, containing all known in nature chemical elements. The formation of the Earth was accompanied by the differentiation of matter, which was facilitated by the gradual heating of the earth's interior, mainly due to the heat released during the decay of radioactive elements (uranium, thorium, potassium, etc.). The result of this differentiation was the division of the Earth into concentrically located layers - geospheres, differing in chemical composition, state of aggregation and physical properties. In the center, the core of the Earth was formed, surrounded by a mantle. From the lightest and most fusible components of matter, released from the mantle in the processes of melting, the earth's crust, located above the mantle, arose. The totality of these inner geospheres, limited by the solid earth's surface, is sometimes called the "solid" Earth (although this is not entirely accurate, since it has been established that the outer part of the core has the properties of a viscous fluid). The "solid" Earth contains almost the entire mass of the planet.

The physical characteristics of the Earth and its orbital motion have allowed life to persist over the past 3.5 billion years. According to various estimates, the Earth will retain the conditions for the existence of living organisms for another 0.5 - 2.3 billion years.

The Earth interacts (is attracted by gravitational forces) with other objects in space, including the Sun and Moon. The Earth revolves around the Sun and makes a complete revolution around it in about 365.26 solar days - a sidereal year. The Earth's axis of rotation is tilted 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 about 24 hours long. The Moon began its orbit around the Earth approximately 4.53 billion years ago. The gravitational influence of the Moon on the Earth is the cause of ocean tides. The moon also stabilizes the tilt of the earth's axis and gradually slows down the rotation of the earth. Some theories suggest that asteroid impacts led to significant changes in environment and the surface of the Earth, causing, in particular, mass extinctions of various species of living beings. http://ru.wikipedia.org/wiki/%C7%E5%EC%EB%FF

The earth, as mentioned earlier, has a shape close to spherical. The radius of the ball is 6371 km. The Earth revolves around the Sun and rotates around its own axis. One natural satellite revolves around the Earth - the Moon. The moon is located at a distance of 384.4 thousand km from the surface of our planet. The periods of its revolution around the Earth and around its axis coincide, so the Moon is turned to the Earth only by one side, and the other is not visible from the Earth. The Moon does not have an atmosphere, so the side facing the Sun has a high temperature, and the opposite, darkened one, has a very low temperature. The surface of the moon is not uniform. The plains and mountain ranges on the Moon are criss-crossed.

The Earth, like other planets of the solar system, has early phases of evolution: the accretion phase (birth), the melting of the outer sphere of the globe, and the phase of the primary crust (lunar phase). A.P. Sadokhin KSE chapter 5 p. reservoirs (oceans) appeared on Earth, in which a combination of substances could occur for the future development of the planet.

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