Our planet is constantly in motion:

• rotation around its own axis, movement around the Sun;
• rotation together with the Sun around the center of our galaxy;
• motion relative to the center of the Local Group of galaxies and others.

Earth's motion around its own axis

Rotation of the Earth around its axis(Fig. 1). An imaginary line is taken for the earth's axis, around which it rotates. This axis is deviated by 23 ° 27 "from the perpendicular to the plane of the ecliptic. The earth's axis intersects with the earth's surface at two points - the poles - the North and South. When viewed from the North Pole, the Earth's rotation occurs counterclockwise or, as is commonly believed, with west to east.The planet makes a complete rotation around its axis in one day.

Rice. 1. Rotation of the Earth around its axis

A day is a unit of time. Separate sidereal and solar days.

sidereal day is the amount of time it takes the earth to rotate on its axis with respect to the stars. They are equal to 23 hours 56 minutes 4 seconds.

solar day is the amount of time it takes for the earth to rotate on its axis with respect to the sun.

The angle of rotation of our planet around its axis is the same at all latitudes. In one hour, each point on the surface of the Earth moves 15° from its original position. But at the same time, the speed of movement is inversely proportional to the geographical latitude: at the equator it is 464 m / s, and at a latitude of 65 ° - only 195 m / s.

The rotation of the Earth around its axis in 1851 was proved by J. Foucault in his experiment. In Paris, in the Pantheon, a pendulum was hung under the dome, and under it a circle with divisions. With each subsequent movement, the pendulum turned out to be on new divisions. This can only happen if the surface of the Earth under the pendulum rotates. The position of the swing plane of the pendulum at the equator does not change, because the plane coincides with the meridian. The axial rotation of the Earth has important geographic implications.

When the Earth rotates, a centrifugal force arises, which plays an important role in shaping the shape of the planet and reduces the force of gravity.

Another of the most important consequences of axial rotation is the formation of a turning force - Coriolis forces. In the 19th century it was first calculated by a French scientist in the field of mechanics G. Coriolis (1792-1843). This is one of the inertial forces introduced to take into account the influence of the rotation of a moving frame of reference on the relative motion of a material point. Its effect can be briefly expressed as follows: every moving body in the Northern Hemisphere deviates to the right, and in the Southern - to the left. At the equator, the Coriolis force is zero (Fig. 3).

Rice. 3. Action of the Coriolis force

The action of the Coriolis force extends to many phenomena of the geographic envelope. Its deflecting effect is especially noticeable in the direction of movement of air masses. Under the influence of the deflecting force of the Earth's rotation, the winds of temperate latitudes of both hemispheres take a predominantly western direction, and in tropical latitudes - east. A similar manifestation of the Coriolis force is found in the direction of movement of ocean waters. The asymmetry of river valleys is also associated with this force (the right bank is usually high in the Northern Hemisphere, in the Southern - the left).

The rotation of the Earth around its axis also leads to the movement of solar illumination across the earth's surface from east to west, i.e., to the change of day and night.

The change of day and night creates a daily rhythm in animate and inanimate nature. The daily rhythm is closely related to light and temperature conditions. The daily course of temperature, day and night breezes, etc. are well known. Daily rhythms also occur in wildlife - photosynthesis is possible only during the day, most plants open their flowers at different hours; Some animals are active during the day, others at night. Human life also proceeds in a daily rhythm.

Another consequence of the rotation of the Earth around its axis is the difference in time at different points on our planet.

Since 1884, a zone time account was adopted, that is, the entire surface of the Earth was divided into 24 time zones of 15 ° each. Behind standard time take the local time of the middle meridian of each belt. Neighboring time zones differ by one hour. The boundaries of the belts are drawn taking into account political, administrative and economic boundaries.

The zero belt is Greenwich (by the name of the Greenwich Observatory near London), which runs on both sides of the zero meridian. The time of the zero, or initial, meridian is considered World Time.

Meridian 180° accepted as international date measurement line- a conditional line on the surface of the globe, on both sides of which hours and minutes coincide, and calendar dates differ by one day.

For a more rational use of daylight in summer in 1930, our country introduced maternity time, ahead of the zone by one hour. To do this, the hands of the clock were moved forward one hour. In this regard, Moscow, being in the second time zone, lives according to the time of the third time zone.

Since 1981, between April and October, the time has been moved forward one hour. This so-called summer time. It is introduced to save energy. In summer, Moscow is two hours ahead of standard time.

The time zone in which Moscow is located is Moscow.

Movement of the Earth around the Sun

Rotating around its axis, the Earth simultaneously moves around the Sun, going around the circle in 365 days 5 hours 48 minutes 46 seconds. This period is called astronomical year. For convenience, it is considered that there are 365 days in a year, and every four years, when 24 hours out of six hours “accumulate”, there are not 365, but 366 days in a year. This year is called leap year, and one day is added to February.

The path in space along which the Earth moves around the Sun is called orbit(Fig. 4). The Earth's orbit is elliptical, so the distance from the Earth to the Sun is not constant. When the earth is in perihelion(from Greek. peri- near, around and helios- Sun) - the closest point of the orbit to the Sun - on January 3, the distance is 147 million km. It is winter in the Northern Hemisphere at this time. The farthest distance from the Sun in aphelion(from Greek. aro- away from and helios- Sun) - the greatest distance from the Sun - July 5. It is equal to 152 million km. At this time, it is summer in the Northern Hemisphere.

Rice. 4. Movement of the Earth around the Sun

The annual movement of the Earth around the Sun is observed by the continuous change in the position of the Sun in the sky - the midday height of the Sun and the position of its sunrise and sunset change, the duration of the bright and dark parts of the day changes.

When moving in orbit, the direction of the earth's axis does not change, it is always directed towards the North Star.

As a result of a change in the distance from the Earth to the Sun, as well as due to the inclination of the Earth's axis to the plane of its movement around the Sun, an uneven distribution of solar radiation is observed on Earth during the year. This is how the seasons change, which is typical for all planets that have an inclination of the axis of rotation to the plane of its orbit. (ecliptic) different from 90°. The orbital speed of the planet in the Northern Hemisphere is higher in winter and lower in summer. Therefore, the winter half-year lasts 179, and the summer half-year - 186 days.

As a result of the movement of the Earth around the Sun and the inclination of the earth's axis to the plane of its orbit by 66.5 °, not only the change of seasons is observed on our planet, but also a change in the length of day and night.

The rotation of the Earth around the Sun and the change of seasons on Earth are shown in Fig. 81 (equinoxes and solstices according to the seasons in the Northern Hemisphere).

Only twice a year - on the days of the equinox, the length of day and night on the whole Earth is almost the same.

Equinox- the moment at which the center of the Sun, during its apparent annual movement along the ecliptic, crosses the celestial equator. There are spring and autumn equinoxes.

The inclination of the Earth's axis of rotation around the Sun on the equinoxes of March 20-21 and September 22-23 is neutral with respect to the Sun, and the parts of the planet facing it are uniformly illuminated from pole to pole (Fig. 5). The sun's rays fall vertically at the equator.

The longest day and shortest night occur on the summer solstice.

Rice. 5. Illumination of the Earth by the Sun on the days of the equinox

Solstice- the moment of passage by the center of the Sun of the points of the ecliptic, the most distant from the equator (solstice points). There are summer and winter solstices.

On the day of the summer solstice on June 21-22, the Earth takes a position in which the northern end of its axis is tilted towards the Sun. And the rays fall vertically not on the equator, but on the northern tropic, whose latitude is 23 ° 27 "All day and night, not only the polar regions are illuminated, but also the space beyond them up to latitude 66 ° 33" (Arctic Circle). In the Southern Hemisphere at this time, only that part of it that lies between the equator and the southern Arctic Circle (66 ° 33 ") turns out to be illuminated. Beyond it, on this day, the earth's surface is not illuminated.

On the day of the winter solstice on December 21-22, everything happens the other way around (Fig. 6). The sun's rays are already falling sheer on the southern tropic. Lighted in the Southern Hemisphere are areas that lie not only between the equator and the tropic, but also around the South Pole. This situation continues until the spring equinox.

Rice. 6. Illumination of the Earth on the day of the winter solstice

At two parallels of the Earth on the days of the solstice, the Sun at noon is directly above the head of the observer, that is, at the zenith. Such parallels are called tropics. On the Tropic of the North (23° N), the Sun is at its zenith on June 22, on the Tropic of the South (23° S) on December 22.

At the equator, day is always equal to night. The angle of incidence of the sun's rays on the earth's surface and the length of the day there change little, so the change of seasons is not expressed.

arctic circles remarkable in that they are the boundaries of areas where there are polar days and nights.

polar day- the period when the sun does not fall below the horizon. The farther from the Arctic Circle near the pole, the longer the polar day. At the latitude of the Arctic Circle (66.5°) it lasts only one day, and at the Pole it lasts 189 days. In the Northern Hemisphere at the latitude of the Arctic Circle, the polar day is observed on June 22 - the day of the summer solstice, and in the Southern Hemisphere at the latitude of the Southern Arctic Circle - on December 22.

polar night lasts from one day at the latitude of the Arctic Circle to 176 days at the poles. During the polar night, the Sun does not appear above the horizon. In the Northern Hemisphere, at the latitude of the Arctic Circle, this phenomenon is observed on December 22.

It is impossible not to note such a wonderful natural phenomenon as white nights. White Nights- these are bright nights at the beginning of summer, when the evening dawn converges with the morning dawn and twilight lasts all night. They are observed in both hemispheres at latitudes exceeding 60°, when the center of the Sun at midnight falls below the horizon by no more than 7°. In St. Petersburg (about 60°N) white nights last from June 11 to July 2, in Arkhangelsk (64°N) from May 13 to July 30.

The seasonal rhythm in connection with the annual movement primarily affects the illumination of the earth's surface. Depending on the change in the height of the Sun above the horizon on Earth, there are five lighting belts. The hot belt lies between the Northern and Southern tropics (the Tropic of Cancer and the Tropic of Capricorn), occupies 40% of the earth's surface and is distinguished by the largest amount of heat coming from the Sun. Between the tropics and the Arctic Circles in the Southern and Northern Hemispheres there are moderate zones of illumination. The seasons of the year are already expressed here: the farther from the tropics, the shorter and cooler the summer, the longer and colder the winter. The polar belts in the Northern and Southern Hemispheres are limited by the Arctic Circles. Here, the height of the Sun above the horizon during the year is low, so the amount of solar heat is minimal. The polar zones are characterized by polar days and nights.

Depending on the annual movement of the Earth around the Sun, there are not only the change of seasons and the associated uneven illumination of the earth's surface across latitudes, but also a significant part of the processes in the geographical envelope: seasonal weather changes, the regime of rivers and lakes, the rhythm in the life of plants and animals, types and terms of agricultural work.

Calendar.Calendar- a system for calculating long periods of time. This system is based on periodic natural phenomena associated with the movement of celestial bodies. The calendar uses astronomical phenomena - the change of seasons, day and night, the change in the lunar phases. The first calendar was Egyptian, created in the 4th century. BC e. On January 1, 45, Julius Caesar introduced the Julian calendar, which is still used by the Russian Orthodox Church. Due to the fact that the duration of the Julian year is longer than the astronomical one by 11 minutes 14 seconds, by the 16th century. an “error” of 10 days accumulated - the day of the vernal equinox did not come on March 21, but on March 11. This mistake was corrected in 1582 by a decree of Pope Gregory XIII. The count of days was moved forward by 10 days, and the day after October 4 was prescribed to be considered Friday, but not October 5, but October 15. The spring equinox was again returned to March 21, and the calendar became known as the Gregorian. It was introduced in Russia in 1918. However, it also has a number of drawbacks: uneven length of months (28, 29, 30, 31 days), inequality of quarters (90, 91, 92 days), inconsistency of numbers of months by days of the week.

When the Earth moves around the Sun, the imaginary axis of the Earth remains always inclined at an angle of 66.5 o to the plane of the Earth's orbit. These two factors - the tilt of the axis and the movement of the Earth around the Sun - lead to the change of seasons. The tilt of the axis causes a different angle of incidence of the sun's rays, and consequently, a different supply of solar radiation to the earth's surface and an unequal length of day and night. The seasonal rhythm of nature is connected with the change of seasons.

Let us consider the position of the Earth in the most characteristic periods. For example, the tilt of the axis on March 21 and September 23 (during the spring and autumn equinoxes) turns out to be neutral with respect to the Sun 1 . At the same time, both hemispheres of the Earth (both northern and southern) are equally illuminated by the Sun. At all latitudes in these periods, the duration of the day and night is 12 hours. On the days of the spring and autumn equinoxes, the sun's rays fall vertically at the equator, i.e. The sun is at its zenith at the equator at noon.

On June 22 (summer solstice), the Earth takes such a position that the northern end of its axis is tilted towards the Sun, while the northern hemisphere is illuminated to the maximum. The sun's rays fall vertically no longer on the equator, but on the northern tropic (the Tropic of Cancer), whose latitude is 23.5 o N. Thus, on June 22, the Sun at noon is at its zenith over the northern tropic. At 66.5 about north latitude (Arctic Circle) on June 22, a polar day is observed, i.e. The sun does not set below the horizon for exactly one day. Around the clock, not only the latitude of the Arctic Circle, but also the entire space to the north of it, up to the North Pole, is illuminated.

At 66.5 about south latitude (Southern Arctic Circle) and south of it to the South Pole on June 22, polar night. June 22 is the longest day of the year in the northern hemisphere, and the shortest day in the southern hemisphere.

December 22 (winter solstice) is the opposite. The sun's rays are already falling sheer on the southern tropic (the Tropic of Capricorn). At the latitude of the Antarctic Circle and to the south of it - the polar day, and at the latitude of the Arctic Circle and to the north of it - the polar night. The earth is positioned so that the southern hemisphere is more illuminated than the northern. December 22 is the shortest day of the year in the northern hemisphere and the longest day in the southern hemisphere.

On the globe, five belts of illumination can be distinguished, the boundaries of which are the tropics and the polar circles. The tropical zone (occupies 40% of the earth's surface) is characterized by the fact that at any point in it the Sun at noon happens twice a year at the zenith, in the tropics themselves - one; on the northern tropic on June 22, on the southern - on December 22. Throughout the year in the tropical zone, the difference between the length of the day and the length of the night is negligible, and twilight is short. There are practically no seasons.

Two temperate belts (occupy 52% of the earth's surface). There are tangible contrasts in the length of day and night depending on the season. Twilight is long. In summer, the Sun is high above the horizon (especially near the tropics), although it does not reach the zenith position; the summer day is very long (especially near the polar circles), but there is no polar day. Accordingly, in winter the Sun is low above the horizon, the winter day is very short. The change of four seasons is clearly expressed.

The two polar belts occupy 8% of the earth's surface. They are characterized by the following features: in summer - a polar day, lasting from one day at the latitude of the Arctic Circle to six months at the pole, respectively, in winter - a polar night with a similar duration. The seasons of the year are weakly expressed: very cold long winters and short cold summers.

In addition to the fact that the Earth revolves around the Sun, it also rotates around its own axis (daily rotation). The direction of rotation is from west to east, as viewed from the North Star. The Earth makes one revolution around its axis in 23 hours 56 minutes. 4 sec. - 1 day). Each point on the earth's surface, except for the poles, describes a circle within a day of greater or lesser magnitude, if we assume that the axis is motionless. As a result of this, it seems to us that the celestial bodies move from east to west. An experimental proof of the rotation of the Earth around its axis is the experiment with the Foucault pendulum. There are several geographic consequences associated with the axial rotation of the Earth:

compression of the Earth from the poles;

the change of day and night, which is associated with the daily rhythm of nature;

emergence of the Coriolis force. With any movement in a rotating system, this force is directed perpendicular to the axis of rotation. Due to the Coriolis force, winds in temperate latitudes of both hemispheres take a predominantly westerly direction, and in tropical latitudes - east (trade winds). A similar manifestation of the Coriolis force is found in the direction of movement of ocean waters. The Coriolis force also explains the Baer-Babinet law, according to which the right banks of the rivers of the northern hemisphere are steeper than the left, and in the southern hemisphere the situation is the opposite.

The movement of the Earth around the Sun occurs in an orbit that is approximately elliptical in shape. The speed of the Earth is about 30 km per second. The Earth makes a complete revolution in 365.26 days. This time is called the sidereal year. The Earth's axis is constantly inclined to the orbital plane at an angle of 66.5°. When the Earth moves around the Sun, the axis does not change its position. Therefore, each point on the earth's surface meets the sun's rays at angles that change during the year. During different periods of the year, the hemispheres of the Earth receive at the same time an unequal amount of solar heat and light, which causes the change of seasons. At the equator, the sun's rays fall at almost the same angle throughout the year, so the seasons there differ little from each other. This is due to the sphericity of our Earth. In temperate latitudes, the seasons are very different from each other. This is due not only to the sphericity of the Earth, but also to the different positions of the planet throughout the year, which is determined by the inclination of the Earth's axis of rotation to the orbit and affects the change in the angle of incidence of the sun's ray throughout the year.

Length of day and night at different latitudes of the Northern Hemisphere at different times of the year

Moving around the Sun, the Earth rotates at the same time around its axis from west to east with a complete revolution during a sidereal day or in 23 hours 56 minutes 4.0905 seconds. The change of day and night is connected with this movement on Earth. On the side illuminated by the Sun - day, on the opposite side - night. Only at the pole there is no usual division of time into days and nights, since for about half a year the Sun does not fall below the horizon and does not rise for the same amount of time. Only in autumn and spring in these latitudes is it possible to observe the change of day and night.

An idea of ​​the change in the length of day and night at different latitudes can be obtained by examining the figure.

One of the consequences of the Earth's rotation around its axis is the deviation of moving bodies in the Northern Hemisphere to the right, in the Southern - to the left. It is caused by the action of the Coriolis force based on the law of inertia. According to it, each body seeks to maintain the direction and speed of its movement, while the rotating Earth, meanwhile, moves, which causes a deviation in the direction of the moving body. The Coriolis force has a deflecting effect on the movement of air and in

These equations make it possible to calculate the characteristics of the Earth's rotation - the coordinates of the pole and the speed of the Earth's rotation. If the masses of ice are unknown, but there are data on the instabilities of the Earth's rotation, then the inverse problem can be solved: using the coordinates of the pole and the speed of rotation, calculate the annual values ​​of the masses of ice in Antarctica, Greenland and water in the World Ocean. Unfortunately, we were unable to match...

Breeds. At the same time, the thickness of the crust becomes less and averages 10-15 km. The crust becomes especially thin in deep-sea depressions (4-5 km). The anomalous gravitational field of the Earth reflects the total effect of gravitating masses located at different depths in the earth's crust and upper mantle. Despite the difficult...

More prosaically, they are connected with periodic oscillations of physical systems and the impact on them of external forces, which also have a physical nature. So, natural disasters are caused by periodic oscillations of the atmosphere - ocean - Earth system under the influence of the Sun (precession), uneven heating of the atmosphere (impact of air masses on the Earth), uneven heating of the ocean (ocean ...

In the sequence of the spectrum (red, orange, yellow, green, blue, indigo, violet), however the colors are almost never pure as the bands overlap. As a rule, the physical characteristics of rainbows vary significantly, and therefore they are very diverse in appearance. Their common feature is that the center of the arc is always located on a straight line drawn from ...

The earth makes a complete rotation around its axis in 23 hours 56 minutes. 4 s. The angular velocity of all points on its surface is the same and is 15 degrees / h. Their linear velocity depends on the distance that the points must travel during the period of their daily rotation. Points on the equator line (464 m / s) rotate with the highest speed. The points that coincide with the North and South Poles remain practically motionless. Thus, the linear speed of points lying on the same meridian decreases from the equator to the poles. It is the unequal linear speed of points on different parallels that explains the manifestation of the deflecting action of the Earth's rotation (the so-called Coriolis force) to the right in the Northern Hemisphere and to the left - in the Southern Hemisphere relative to the direction of their movement. The deflecting action especially affects the direction of air masses and sea currents.

The Coriolis force acts only on moving bodies, it is proportional to their mass and speed of movement and depends on the latitude at which the point is located. The greater the angular velocity, the greater the Coriolis force. The deflecting force of the Earth's rotation increases with latitude. its value can be calculated by the formula

where m- weight; v- the speed of the body moving; w- angular velocity of the Earth's rotation; j is the latitude of the given point.

The rotation of the Earth causes a rapid change of day and night. Daily rotation creates a special rhythm in the development of physical and geographical processes and nature in general. One of the important consequences of the daily rotation of the Earth around its axis is the tides - the phenomenon of periodic fluctuations in the level of the ocean, which is caused by the forces of attraction of the Sun and the Moon. Most of these forces are monthly, and therefore it determines the main features of tidal phenomena. Influx phenomena also take place in the earth's crust, but here they do not exceed 30-40 cm, while in the oceans in some cases they reach 13 m (Penzhina Bay) and even 18 m (Bay of Fundy). The height of water ledges on the surface of the oceans is about 20 cm, and they circle the oceans twice a day. The extreme position of the water level at the end of the inflow is called high water, at the end of the outflow - low water; the difference between these levels is called the magnitude of the tide.

The mechanism of tidal phenomena is quite complex. Their main essence is that the Earth and the Moon are the only system in rotation around a common center of gravity, which lies inside the Earth at a distance of about 4800 km from its center (Fig. 10). As with any flesh, two forces act on the Earth-Moon system: attraction and centrifugal. The ratio of these forces on different sides of the Earth is not the same. On the side of the Earth facing the Moon, the forces of attraction of the Moon are larger than the centrifugal forces of the system, and their resultant is directed towards the Moon. On the side of the Earth opposite to the Moon, the system's centrifugal forces are larger than the Moon's gravity, and their resultant force is directed away from it. These resultant forces are tidal forces; they cause an increase in water on opposite sides of the Earth.

Rice. 10.

Due to the fact that the Earth performs a daily rotation in the field of these forces, and the Moon moves around it, inflow waves try to move in accordance with the position of the Moon, therefore, in each region of the ocean for 24 hours and 50 minutes. twice there is high tide and twice low tide. Daily backlog of 50 minutes. due to the advanced motion of the Moon in its orbit around the Earth.

The sun also causes tides on Earth, although they are three times smaller in height. They are superimposed on the lunar tides, changing their characteristics.

Despite the fact that the Sun, the Earth and the Moon are almost in the same plane, they constantly change their relative position in their orbits, so their influx influence changes accordingly. Twice in a monthly cycle - on a new (young) month and a full moon - the Earth, Moon and Sun are on the same line. At this time, the tidal forces of the Moon and the Sun coincide and unusually high, so-called spring tides arise. In the first and third quarters of the Moon, when the tidal forces of the Sun and Moon are directed at right angles to each other, they have the opposite effect and the height of the lunar tides is less than about one third. These tides are called quadrature.

The problem of using the colossal energy of ebbs and flows has long attracted the attention of mankind, but its solution began with the construction of tidal power plants (TPP) only now. The first TPP went into operation in France in 1960. In Russia, in 1968, the Kislogubskaya TPP was built on the coast of the Kola Bay. In the area of ​​the White Sea, as well as in the Far Eastern seas of Kamchatka, it is planned to build several more TPPs.

Inflow waves gradually slow down the speed of the Earth's rotation because they move in the opposite direction. Therefore, the Earth's day becomes longer. It is estimated that only because of water inflows for every 40 thousand years, the day increases by 1 s. A billion years ago, a day on Earth was only 17 hours long. In a billion years, a day will last 31 hours. And in a few billion years, the Earth will be turned to the Moon all the time on one side, just as the Moon is now to the Earth.

Some scientists believe that the interaction of the Earth with the Moon is one of the main reasons for the primary heating of our planet. Forced friction causes the Moon to move away from the Earth at a rate of about 3 cm/yr. This value is highly dependent on the distance between the two bodies, which is now 60.3 Earth radii.

If we assume that at first the Earth and the Moon were much closer, then, on the one hand, the tidal force should be greater. The tidal wave creates internal friction in the body of the planet, which is accompanied by the release of heat,

With the rotation of the Earth around its axis, its strength is associated, which depends on the angular velocity of the daily rotation of the planet. Rotation generates a centrifugal force that is directly proportional to the square of the angular velocity. Now the centrifugal force at the equator, where it is greatest, is only 1/289 of the earth's gravity. On average, the Earth has 15 times the safety margin. The sun is 200 times, and Saturn is only 1.5 times due to the rapid rotation around its axis. Its rings were formed, possibly due to the faster rotation of the planet in the past. It was hypothesized that the Moon was also formed as a result of the separation of part of the Earth's mass in the Pacific Ocean due to its rapid rotation. However, after studying samples of lunar rocks, this hypothesis was rejected, but the fact that the shape of the Earth changes depending on the speed of its rotation does not cause any doubts among specialists.

Such concepts as sidereal, solar, standard and local time, the date line, etc. are associated with the daily rotation of the Earth. Time is the main unit for determining the time during which the apparent counterclockwise rotation of the celestial sphere occurs. Having noticed the starting point in the sky, the angle of rotation is deducted from it, according to which the time elapsed is calculated. The sidereal hour is counted from the moment of the upper climax of the vernal equinox, at which the ecliptic intersects with the equator. They are used for astronomical observations. Solar time (real, or true, average) is counted from the moment of the lower culmination of the center of the solar disk on the meridian of the observer. Local time is the mean solar time at each point on Earth, which depends on the longitude of that point. The further east a point on Earth is, the more local time it has (every 15 ° of longitude gives a difference in time by 1 hour), and the farther west, the less time.

The earth's surface is conditionally divided into 24 time zones, on the territory of which time is considered equal to the time of the central meridian, that is, the meridian passing through the middle of the zone.

In densely populated regions, the limits of the belts run along the borders of states and administrative regions, sometimes they coincide with natural boundaries: riverbeds, mountain ranges, and the like. In the first time zone, the time is one hour ahead of the zero zone, or Greenwich meridian mean solar time, in the second zone it is 2:00, and so on.

Standard time, which divides the planet into 24 time zones, was introduced in many countries around the world in 1884 p. And although its concentration did not eliminate all the misunderstandings associated with the calculation of time (let us recall, for example, the recent heated discussions in some regions of Ukraine about the introduction on its territory instead of Moscow Kyiv time, that is, the time of the second time zone, in which our country, in fact, located), yet the system of time zones has become generally accepted on the planet. After all, the standard time not only differs little from the local time, it is also convenient when using it on travels far in geographical longitude. In this regard, it would be appropriate to recall one interesting story that unexpectedly happened to the participants of the first round-the-world trip at its completion.

At the end of 1522, an unusual procession was going through the narrow streets of the Spanish city of Seville: 18 sailors of F. Magellan's expedition had just returned to their native harbor after a long ocean voyage. People were extremely exhausted during the almost three-year voyage. For the first time they went around the globe, accomplished a feat. But the winners were not similar. In hands trembling with weakness, they carried burning candles and slowly headed towards the cathedral in order to atone for the involuntary sin that was committed on a long voyage ...

What were the pioneers of the planet guilty of? When the Victoria approached the Cape Verde Islands on her way back, a boat was sent ashore for food and fresh water. The sailors soon returned to the ship and informed the astonished crew: on land, for some reason, this day is considered Thursday, although according to the ship's log it is Wednesday. When they returned to Seville, they finally realized that they had lost a day in their ship account! And this means that they committed a great sin, because they celebrated all religious holidays a day earlier than the calendar required. In this they repented in the cathedral.

How did experienced sailors lose a day? It must be said right away "that they did not make any mistake in counting the days. The fact is that the globe rotates around its axis from west to east and makes one revolution in a day. F. Magellan's expedition moved in the opposite direction from east to west and from for three years of a round-the-world trip, she also made a complete revolution around the earth's axis, but in the direction opposite to the direction of the Earth's rotation, which means that the travelers made one revolution less than all mankind on Earth.And they did not lose a day, but won it.If if the expedition was moving not to the west, but to the east, then the ship's log would have recorded one day more than all people.The astronomer of the expedition of F. Magellan Antonio Pigafetta guessed that in different places of the globe at the same time different. And it should be so, because the Sun does not rise at the same time for the entire planet. This means that on each meridian there is a local time, the beginning of which is counted from that moment nta, when the Sun is low below the horizon, that is, it is in the so-called lower climax. However, people in their daily activities do not pay attention to this and are guided by standard time, which corresponds to the local time of the middle meridian of the corresponding time zone.

But the distribution of the globe into time zones still does not solve all the problems, in particular the problem of the rational use of the daylight period. Therefore, on the last Sunday of March in many countries, including Ukraine, the clock hands are moved forward one hour, and at the end of October they are returned to standard time again. The transition to summer time allows more economical use of fuel and energy resources. In addition, this allows people to work and relax more in natural light conditions, and use the darkest time of the day for sleep.

In the practical distribution of time zones on our planet, the spaces through which the date line conditionally passes are specific. This line runs mostly in the open ocean along the geographic meridian of 180° and deviates somewhat where it crosses islands or separates various states. This was done in order to avoid certain calendar inconveniences for the people who inhabit them. When crossing the line from west to east, the date is repeated, when moving in the opposite direction, one day is excluded from the account. Interestingly, there are two islands in the Bering Strait between Chukotka and Alaska that are separated by the international date line: Ratmanov Island, which belongs to Russia, and Kruzenshtern Island, which belongs to SELA. Having overcome the distance of several kilometers between the two islands, you can get ... to yesterday, if you are sailing from Ratmanov Island, or to tomorrow, when you are heading in the opposite direction.

The Earth makes a complete revolution around the Sun in 365 days 6 hours 9 minutes and 9 seconds. On March 21 and September 23, the inclination of the earth's axis is neutral with respect to the Sun (equinox days). On June 21, the Earth occupies a position in which its axis at its northern end on December 22, on the day of the winter solstice, the sheer rays fall on the southern tropic, and the northern polar countries , starting from the Arctic Circle, are not illuminated. In the Antarctic Circle and further to the pole, the Sun is above the horizon around the clock. This continues until the spring equinox - March 21.

Lighting belts

There are 13 lighting zones in total. The equatorial belt is located on both sides of the equator. day and night are almost always equal here, twilight is very short, there is no change of seasons. Tropical zones: the length of day and night varies from 10.5 to 13.5 hours; twilight is short, there are two seasons of the year that differ little in temperature. Subtropical belts: The length of day and night for extreme latitudes ranges from 9 hours to 14 hours. Twilight is short, winter and summer are often pronounced, spring and autumn are less pronounced. Temperate zones: All four seasons are clearly expressed (spring, summer, autumn, winter). Winter and summer are approximately equal. Belts of summer nights and short winter days: all four seasons are expressed, winter is longer than summer. subpolar belts. Polar belts: the seasons coincide with day and night.

The motion of the binary planet Earth-Moon and tidal friction

Universal gravitation is balanced by universal repulsion. The essence of gravitation (gravity) is that all bodies are attracted to each other in proportion to their masses and inversely proportional to the square of the distance between them. Repulsion is a centrifugal force that occurs during the rotation and circulation of celestial bodies. The Earth and the Moon are mutually attracted, but the Moon cannot fall to the Earth, since it revolves around the Earth and thus tends to get away from it. The balance of attraction and repulsion is true for the centers of the planets. However, it does not apply to individual points on the Earth's surface. So there are ebbs and flows. The interaction of two forces - the force of attraction and the centrifugal force - is the tide-forming force. The tides are best expressed in the oceans.

ATMOSPHERE

The atmosphere is the gaseous envelope of the Earth. At present, the atmosphere consists of the following components: Nitrogen - 78.08%, Oxygen - 20.94%, Argon - 0.93%, Carbon dioxide - 0.03%, Other gases - 0.02%. The atmosphere consists of the following layers: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The geographic envelope includes only the troposphere and the lower part of the stratosphere. The average thickness of the troposphere is about 11 km. Above the troposphere is the tropopause, which is a thin transitional layer with a thickness of about one kilometer. Above the tropopause is the stratosphere. The stratosphere begins 8 km above the poles and 16-18 km above the equator. Above the heated layer of the upper atmosphere, after the stratopause, i.e., above 55 km, lies the mesosphere, which extends to a height of 80 km. In it, the temperature again drops to -90 0C. At altitudes from 80 to 90 km there is a mesopause with a constant temperature of about 1800 C. Above the mesopause is the thermosphere, which extends up to 800 - 1000 km. Above 1,000 km, the outer atmosphere, or exosphere, begins, extending up to 2,000–3,000 km. The troposphere and lower stratosphere are called the lower atmosphere, and all higher layers are called the upper atmosphere.

Solar radiation

Solar radiation is the totality of solar matter and energy entering the Earth. Solar radiation carries light and heat. The intensity of solar radiation must be measured primarily outside the atmosphere, because when passing through the air sphere, it is transformed and weakens. The intensity of solar radiation is expressed by the solar constant. The solar constant is the flux of solar energy in 1 minute over an area with a cross section of 1 cm2, perpendicular to the sun's rays and located outside the atmosphere. The solar constant, contrary to its name, does not remain constant. It changes due to the change in the distance from the Sun to the Earth as the Earth moves in its orbit. No matter how small these fluctuations are, they always affect the weather and climate.