Even in ancient times, observing the starry sky, people noticed that during the day the sun, and in the night sky - almost all the stars - repeat their path from time to time. This suggested that there were two reasons for this phenomenon. Either it takes place against the background of a fixed starry sky, or the sky revolves around the Earth. Claudius Ptolemy, an outstanding ancient Greek astronomer, scientist and geographer, seemed to have solved this issue by convincing everyone that the Sun and the sky revolve around the motionless Earth. Despite the fact that she could not explain, many resigned themselves to this.

The heliocentric system, based on another version, won its recognition in a long and dramatic struggle. Giordano Bruno died at the stake, the aged Galileo recognized the "correctness" of the Inquisition, but "... it still spins!"

Today, the rotation of the Earth around the Sun is considered fully proven. In particular, the movement of our planet in a near-solar orbit is proved by the aberration of starlight and parallactic displacement with a periodicity equal to one year. Today it has been established that the direction of rotation of the Earth, more precisely, its barycenter, along the orbit coincides with the direction of its rotation around its axis, that is, it occurs from west to east.

There are many facts that indicate that the Earth moves in space along a very complex orbit. The rotation of the Earth around the Sun is accompanied by its movement around the axis, precession, nutational oscillations and rapid flight along with the Sun in a spiral within the Galaxy, which also does not stand still.

The rotation of the Earth around the Sun, like other planets, takes place in an elliptical orbit. Therefore, once a year, on January 3, the Earth is as close as possible to the Sun and once, on July 5, it moves away from it at the greatest distance. The difference between perihelion (147 million km) and aphelion (152 million km), compared to the distance from the Sun to the Earth, is very small.

Moving in a near-solar orbit, our planet makes 30 km per second, and the revolution of the Earth around the Sun is completed within 365 days 6 hours. This is the so-called sidereal, or stellar, year. For practical convenience, it is customary to consider 365 days a year. The "additional" 6 hours in 4 years add up to 24 hours, that is, one more day. These (running, extra) days are added to February once every 4 years. Therefore, in our calendar, 3 years include 365 days, and a leap year - the fourth year, contains 366 days.

The Earth's own rotation axis is tilted to the orbital plane by 66.5°. In this regard, during the year, the sun's rays fall on every point on the earth's surface under

corners. Thus, at different times of the year, points on different sites receive at the same time an unequal amount of light and heat. Because of this, in temperate latitudes, the seasons have a pronounced character. At the same time, throughout the year, the sun's rays at the equator fall on the earth at the same angle, so the seasons there differ slightly from each other.

Basic movements of the Earth in space

© Vladimir Kalanov,
website"Knowledge is power".

Our planet rotates around its own axis from west to east, that is, counterclockwise (when viewed from the North Pole). The axis is a conditional straight line crossing the globe in the region of the North and South Poles, that is, the poles have a fixed position and "do not participate" in rotational motion, while all other locations on the earth's surface rotate, and the linear speed of rotation on surface of the globe depends on the position with respect to the equator - the closer to the equator, the higher the linear speed of rotation (let us explain that the angular speed of rotation of any ball is the same at its various points and is measured in rad / sec, we are discussing the speed of movement of an object located on surface of the Earth and it is the higher, the more the object is removed from the axis of rotation).

For example, at the mid-latitudes of Italy, the rotation speed is about 1200 km / h, at the equator it is maximum and is 1670 km / h, while at the poles it is zero. The consequences of the rotation of the Earth around its axis are the change of day and night and the apparent movement of the celestial sphere.

Indeed, it seems that the stars and other celestial bodies of the night sky are moving in the opposite direction to our motion with the planet (that is, from east to west). It seems that the stars are around the North Star, which is located on an imaginary line - the continuation of the earth's axis in a northerly direction. The movement of the stars is not evidence that the Earth rotates on its axis, because this movement could be a consequence of the rotation of the celestial sphere, if we consider that the planet occupies a fixed, unmoving position in space, as previously thought.

Day. What are sidereal and solar days?

A day is the length of time it takes for the Earth to complete one rotation around its own axis. There are two definitions of the term "day". A "solar day" is the time period of the Earth's rotation, in which the Sun is taken as the starting point. Another concept is “sidereal day” (from lat. sidus- Genitive sideris- star, celestial body) - implies another starting point - a "fixed" star, the distance to which tends to infinity, and therefore we assume that its rays are mutually parallel. The duration of the two types of days is different from each other. The sidereal day is 23 h 56 min 4 s, while the duration of the solar day is slightly longer and equal to 24 hours. The difference is due to the fact that the Earth, rotating around its own axis, also performs an orbital rotation around the Sun. It is easier to understand this with the help of a picture.

Solar and sidereal days. Explanation.

Consider the two positions (see Fig.) that the Earth occupies while moving along its orbit around the Sun, “ BUT» - the place of the observer on the earth's surface. 1 - the position that the Earth occupies (at the beginning of the countdown of the day) either from the Sun or from some star, which we will define as a reference point. 2 - the position of our planet after making a revolution around its own axis relative to this star: the light of this star, and it is at a great distance, will reach us parallel to the direction 1 . When the earth takes position 2 , we can talk about "sidereal days", because The Earth has made a complete rotation around its axis relative to the distant star, but not yet relative to the Sun. The direction of observation of the Sun has changed somewhat due to the rotation of the Earth. In order for the Earth to make a complete revolution around its own axis relative to the Sun (“solar day”), you need to wait until it “turns” by about 1 ° (the equivalent of the daily movement of the Earth at an angle - it passes 360 ° in 365 days), this takes just about four minutes.

In principle, the duration of a solar day (although it is taken as 24 hours) is a variable value. This is due to the fact that the movement of the Earth in orbit actually occurs at a variable speed. When the Earth is closer to the Sun, the speed of its movement in orbit is higher, as it moves away from the sun, the speed decreases. As a result, the notion of "mean solar day", namely, their duration is twenty-four hours.

In addition, it is now reliably established that the period of the Earth's rotation increases under the influence of the change in sea tides caused by the Moon. The slowdown is approximately 0.002 s per century. The accumulation of such seemingly imperceptible deviations, however, means that from the beginning of our era to the present day, the total slowdown is already about 3.5 hours.

The revolution around the Sun is the second main movement of our planet. The earth moves in an elliptical orbit, i.e. the orbit is elliptical. When the Moon is in close proximity to the Earth and falls into its shadow, eclipses occur. The average distance between the Earth and the Sun is approximately 149.6 million kilometers. Astronomy uses a unit to measure distances within the solar system; they call her "astronomical unit" (a.u.). The speed at which the Earth moves in its orbit is approximately 107,000 km/h. The angle formed by the earth's axis and the plane of the ellipse is approximately 66°33" and is maintained throughout the orbit.

From the point of view of an observer located on Earth, the revolution leads to the apparent movement of the Sun along the ecliptic through the stars and constellations represented in the Zodiac. In fact, the Sun also passes through the constellation Ophiuchus, but it does not belong to the Zodiac circle.

Seasons

The change of seasons is a consequence of the revolution of the Earth around the Sun. The reason for seasonal changes is the inclination of the Earth's axis of rotation to the plane of its orbit. Moving in an elliptical orbit, the Earth in January is at the point closest to the Sun (perihelion), and in July at the point farthest from it - aphelion. The reason for the change of seasons is the tilt of the orbit, as a result of which the Earth tilts towards the Sun with one hemisphere, then with the other, and, accordingly, receives a different amount of sunlight. In summer, the Sun reaches the highest point of the ecliptic. This means that the Sun makes the longest movement over the horizon in a day, and the duration of the day is maximum. In winter, on the contrary, the Sun is low above the horizon, the sun's rays fall on the Earth not directly, but obliquely. The length of the day is short.

Depending on the time of year, different parts of the planet are exposed to the sun's rays. The rays are perpendicular to the tropics at the time of the solstice.

Seasons in the northern hemisphere

Earth's annual motion

The definition of the year, the main calendar unit of time, is not as simple as it seems at first glance, and depends on the chosen reference system.

The time interval for which our planet makes a complete revolution in its orbit around the Sun is called a year. However, the length of the year differs depending on whether it is taken as a reference point when measuring it. infinitely distant star or The sun.

In the first case, it means sidereal year . He is equal 365 days 6 hours 9 minutes and 10 seconds and represents the time required for the complete revolution of the Earth around the Sun.

But if we measure the time required for the Sun to return to the same point in the celestial coordinate system, for example, at the vernal equinox, then we get the duration "solar year" 365 days 5 hours 48 minutes 46 seconds. The difference between the sidereal and solar years is due to the precession of the equinoxes, each year the days of the equinoxes (and, accordingly, the sun stands) come "earlier" by about 20 minutes. compared to the previous year. Thus, the Earth goes around its orbit a little faster than the Sun in its apparent movement through the stars returns to the vernal equinox.

Considering that the duration of the seasons is in close connection with the Sun, when compiling calendars, it is precisely "solar year" .

Also in astronomy, instead of the usual astronomical time, determined by the period of rotation of the Earth relative to the stars, a new uniformly current time was introduced, not related to the rotation of the Earth and called ephemeris time.

Read more about ephemeris time in the section: .

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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 westerly 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 prime 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.

Our planet is in constant motion. Together with the Sun, it moves in space around the center of the Galaxy. And that, in turn, moves in the universe. But the most important thing for all living things is the rotation of the Earth around the Sun and its own axis. Without this movement, the conditions on the planet would be unsuitable for sustaining life.

solar system

Earth as a planet of the solar system, according to scientists, was formed more than 4.5 billion years ago. During this time, the distance from the sun practically did not change. The speed of the planet and the gravitational pull of the sun balance its orbit. It is not perfectly round, but stable. If the force of attraction of the star were stronger or the speed of the Earth decreased noticeably, then it would fall on the Sun. Otherwise, sooner or later it would fly into space, ceasing to be part of the system.

The distance from the Sun to the Earth makes it possible to maintain the optimum temperature on its surface. The atmosphere also plays an important role in this. As the Earth rotates around the Sun, the seasons change. Nature has adapted to such cycles. But if our planet were further away, then the temperature on it would become negative. If it were closer, all the water would evaporate, since the thermometer would exceed the boiling point.

The path of a planet around a star is called an orbit. The trajectory of this flight is not perfectly round. It has an ellipse. The maximum difference is 5 million km. The closest point of the orbit to the Sun is at a distance of 147 km. It's called perihelion. Its land passes in January. In July, the planet is at its maximum distance from the star. The greatest distance is 152 million km. This point is called aphelion.

The rotation of the Earth around its axis and the Sun provides, respectively, a change in daily regimes and annual periods.

For a person, the movement of the planet around the center of the system is imperceptible. This is because the mass of the Earth is enormous. Nevertheless, every second we fly through space about 30 km. It seems unrealistic, but such are the calculations. On average, it is believed that the Earth is located at a distance of about 150 million km from the Sun. It makes one complete revolution around the star in 365 days. The distance traveled in a year is almost a billion kilometers.

The exact distance that our planet travels in a year, moving around the sun, is 942 million km. Together with her, we move in space in an elliptical orbit at a speed of 107,000 km / h. The direction of rotation is from west to east, that is, counterclockwise.

The planet does not complete a complete revolution in exactly 365 days, as is commonly believed. It still takes about six hours. But for the convenience of chronology, this time is taken into account in total for 4 years. As a result, one additional day “runs in”, it is added in February. Such a year is considered a leap year.

The speed of rotation of the Earth around the Sun is not constant. It has deviations from the mean. This is due to the elliptical orbit. The difference between the values ​​is most pronounced at the points of perihelion and aphelion and is 1 km/sec. These changes are imperceptible, since we and all the objects around us move in the same coordinate system.

change of seasons

The rotation of the Earth around the Sun and the tilt of the planet's axis make it possible for the seasons to change. It is less noticeable at the equator. But closer to the poles, the annual cyclicity is more pronounced. The northern and southern hemispheres of the planet are heated by the energy of the Sun unevenly.

Moving around the star, they pass four conditional points of the orbit. At the same time, twice in turn during the semi-annual cycle, they turn out to be further or closer to it (in December and June - the days of the solstices). Accordingly, in a place where the surface of the planet warms up better, the ambient temperature is higher there. The period in such a territory is usually called summer. In the other hemisphere at this time it is noticeably colder - it is winter there.

After three months of such movement, with a frequency of six months, the planetary axis is located in such a way that both hemispheres are in the same conditions for heating. At this time (in March and September - the days of the equinox) the temperature regimes are approximately equal. Then, depending on the hemisphere, autumn and spring come.

earth axis

Our planet is a spinning ball. Its movement is carried out around a conditional axis and occurs according to the principle of a top. Leaning with the base in the plane in the untwisted state, it will maintain balance. When the speed of rotation weakens, the top falls.

The earth has no stop. The forces of attraction of the Sun, the Moon and other objects of the system and the Universe act on the planet. Nevertheless, it maintains a constant position in space. The speed of its rotation, obtained during the formation of the nucleus, is sufficient to maintain relative equilibrium.

The earth's axis passes through the planet's ball is not perpendicular. It is inclined at an angle of 66°33´. The rotation of the Earth on its axis and the Sun makes it possible to change the seasons of the year. The planet would "tumble" in space if it did not have a strict orientation. There would be no question of any constancy of environmental conditions and life processes on its surface.

Axial rotation of the Earth

The rotation of the Earth around the Sun (one revolution) occurs during the year. During the day it alternates between day and night. If you look at the Earth's North Pole from space, you can see how it rotates counterclockwise. It completes a full rotation in about 24 hours. This period is called a day.

The speed of rotation determines the speed of the change of day and night. In one hour, the planet rotates approximately 15 degrees. The speed of rotation at different points on its surface is different. This is due to the fact that it has a spherical shape. At the equator, the linear speed is 1669 km / h, or 464 m / s. Closer to the poles, this figure decreases. At the thirtieth latitude, the linear speed will already be 1445 km / h (400 m / s).

Due to axial rotation, the planet has a slightly compressed shape from the poles. Also, this movement "forces" moving objects (including air and water flows) to deviate from the original direction (Coriolis force). Another important consequence of this rotation is the ebbs and flows.

the change of night and day

A spherical object with the only light source at a certain moment is only half illuminated. In relation to our planet in one part of it at this moment there will be a day. The unlit part will be hidden from the Sun - there is night. Axial rotation makes it possible to change these periods.

In addition to the light regime, the conditions for heating the surface of the planet with the energy of the luminary change. This cycle is important. The speed of change of light and thermal regimes is carried out relatively quickly. In 24 hours, the surface does not have time to either overheat or cool below the optimum.

The rotation of the Earth around the Sun and its axis with a relatively constant speed is of decisive importance for the animal world. Without the constancy of the orbit, the planet would not have stayed in the zone of optimal heating. Without axial rotation, day and night would last for six months. Neither one nor the other would contribute to the origin and preservation of life.

Uneven rotation

Mankind has become accustomed to the fact that the change of day and night occurs constantly. This served as a kind of standard of time and a symbol of the uniformity of life processes. The period of rotation of the Earth around the Sun to a certain extent is influenced by the ellipse of the orbit and other planets of the system.

Another feature is the change in the length of the day. The axial rotation of the Earth is uneven. There are several main reasons. Seasonal fluctuations associated with the dynamics of the atmosphere and the distribution of precipitation are important. In addition, the tidal wave, directed against the motion of the planet, constantly slows it down. This figure is negligible (for 40 thousand years for 1 second). But over 1 billion years, under the influence of this, the length of the day increased by 7 hours (from 17 to 24).

The consequences of the Earth's rotation around the Sun and its axis are being studied. These studies are of great practical and scientific importance. They are used not only to accurately determine stellar coordinates, but also to identify patterns that can affect human life processes and natural phenomena in hydrometeorology and other fields.

For a very long time, people thought that our planet has a flattened shape and lies on 3 whales. A person is unable to notice its rotation, being on it itself. The reason for this is the size. They matter a lot! The size of a man is too small in relation to the size of the globe. Time moved forward, science progressed, and with it people's ideas about their own planet.

What have we come to today? Is it true that and not vice versa? What other astronomical knowledge in this area is valid? About everything in order.

Along its axis

Today we know that it takes part in two types of its movement simultaneously: the Earth revolves around the Sun and along its own imaginary axis. Yes, axles! Our planet has an imaginary line that "pierces" the surface of the earth at its two poles. Draw the axis mentally into the sky, and it will pass next to the North Star. That is why this point always seems to us motionless, and the sky seems to be rotating. We think that we are moving from east to west, but we note that it only seems to us! Such a movement is visible, since it is a reflection of the present rotation of the planet - along the axis.

The daily rotation lasts exactly 24 hours. In other words, in one day the globe performs one full circle along its own axis. Each of the earthly points first passes through the illuminated side, then the dark side. And a day later, everything repeats again.

For us, it looks like a constant change of days and nights: morning - afternoon - evening - morning ... If the planet did not rotate in this way, then there would be eternal day on the side facing the light, and eternal night on the opposite side. Horrible! It's good that it's not! In general, we figured out the daily rotation. Now let's find out how many times the Earth revolves around the Sun.

Solar "round dance"

This is also not visible to the naked eye. However, this phenomenon can be felt. We all know very well the warm and cold seasons. But what do they have in common with the movements of the planet? Yes, they have everything in common! The earth revolves around the sun in three hundred and sixty-five days, or one year. In addition, our globe is a participant in other movements. For example, together with the Sun and its "colleagues" - the planets, the Earth moves relative to its own galaxy - the Milky Way, which, in turn, moves relative to its "colleagues" - other galaxies.

It is important to know that in the whole Universe nothing is immovable, everything flows and changes! Note that the movement of the celestial body that we see is just a reflection of a rotating planet.

Is the theory correct?

Today, many people are trying to prove the opposite: they believe that it is not the Earth that revolves around the Sun, but, on the contrary, the celestial body around the globe. Some scientists talk about the joint movement of the Earth and the Sun, which occurs relative to each other. Perhaps someday the world's scientific minds will turn "upside down" all the scientific ideas about space known today! So, all the dots over the “and” are dotted, and you and I learned that around the Sun (at a speed, by the way, about 30 kilometers per second), and it makes a full revolution in 365 days (or 1 year), at the same time Our planet rotates its axis in a day (24 hours).