For an observer located in the Northern Hemisphere, for example, in the European part of Russia, the Sun usually rises in the east and rises to the south, occupying the highest position in the sky at noon, then slopes to the west and disappears behind the horizon. This movement of the Sun is only visible and is caused by the rotation of the Earth around its axis. If you look at the Earth from above in the direction of the North Pole, it will rotate counterclockwise. At the same time, the Sun remains in place, the appearance of its movement is created due to the rotation of the Earth.

Annual rotation of the Earth

The Earth also rotates counterclockwise around the Sun: if you look at the planet from above, from the North Pole. Because the Earth's axis is tilted relative to its plane of rotation, it illuminates it unevenly as the Earth rotates around the Sun. Some areas receive more sunlight, others less. Thanks to this, the seasons change and the length of the day changes.

Spring and autumn equinox

Twice a year, on March 21 and September 23, the Sun illuminates the Northern and Southern Hemispheres equally. These moments are known as the autumn equinox. In March, autumn begins in the Northern Hemisphere, and autumn in the Southern Hemisphere. In September, on the contrary, autumn comes to the Northern Hemisphere, and spring to the Southern Hemisphere.

Summer and winter solstice

In the Northern Hemisphere, on June 22, the Sun rises highest above the horizon. The day has the longest duration, and the night on this day is the shortest. The winter solstice occurs on December 22 - the day has the shortest duration and the night has the longest. In the Southern Hemisphere, the opposite happens.

polar night

Due to the tilt of the earth's axis, the polar and subpolar regions of the Northern Hemisphere are without sunlight during the winter months - the Sun does not rise above the horizon at all. This phenomenon is known as polar night. A similar polar night exists for the circumpolar regions of the Southern Hemisphere, the difference between them is exactly six months.

What gives the Earth its rotation around the Sun

Planets cannot help but revolve around their stars - otherwise they would simply be attracted and burnt up. The uniqueness of the Earth lies in the fact that its axis tilt of 23.44° turned out to be optimal for the emergence of all the diversity of life on the planet.

It is thanks to the tilt of the axis that the seasons change, there are different climatic zones that provide the diversity of the earth's flora and fauna. Changes in the heating of the earth's surface ensure the movement of air masses, and therefore precipitation in the form of rain and snow.

The distance from the Earth to the Sun of 149,600,000 km also turned out to be optimal. A little further, and water on Earth would only be in the form of ice. Any closer and the temperature would have been too high. The very emergence of life on Earth and the diversity of its forms became possible precisely thanks to the unique coincidence of so many factors.

Man sees the Earth as flat, but it has long been established that the Earth is a sphere. People agreed to call this celestial body a planet. Where did this name come from?

Ancient Greek astronomers, who observed the behavior of celestial bodies, introduced two terms with opposite meanings: planetes asteres - “stars” - celestial bodies similar to stars, moving throughout; asteres aplanis - “fixed stars” - celestial bodies that remained motionless throughout the year. In the beliefs of the Greeks, the Earth was motionless and located in the center, so they classified it as a “fixed star”. The Greeks knew Mercury, Venus, Mars, Jupiter and Saturn, visible to the naked eye, but they called them not “planets”, but “wandering”. In Ancient Rome, astronomers already called these bodies “planets”, adding to this the Sun and the Moon. The idea of ​​a seven-planet system survived until the Middle Ages. In the 16th century, Nicolaus Copernicus changed his views on the device, noticing its heliocentricity. The Earth, previously considered the center of the world, was reduced to the position of one of the planets revolving around the Sun. In 1543, Copernicus published his work entitled “On the Revolutions of the Celestial Spheres,” in which he expressed his point of view. Unfortunately, the church did not appreciate the revolutionary nature of Copernicus’s views: his sad fate is known. By the way, according to Engels, the “liberation of natural science from theology” begins its chronology precisely with the published work of Copernicus. So, Copernicus replaced the geocentric system of the world with a heliocentric one. The name “planet” has stuck with the Earth. The definition of a planet, in general, has always been ambiguous. Some astronomers argue that the planet must be quite massive, while others consider this an optional condition. If we approach the issue formally, the Earth can be safely called a planet, if only because the word “planet” itself comes from the ancient Greek planis, meaning “movable,” and modern science has no doubt about the mobility of the Earth.

“And yet, she spins!” – we have known this encyclopedic phrase, uttered by the physicist and astronomer of the past Galileo Galilei, since our school days. But why does the Earth rotate? In fact, this question is often asked by their parents as young children, and adults themselves are not averse to understanding the secrets of the Earth’s rotation.

For the first time, an Italian scientist spoke about the fact that the Earth rotates around its axis in his scientific works at the beginning of the 16th century. But there has always been a lot of controversy in the scientific community about what rotation occurs. One of the most common theories says that in the process of the earth’s rotation, other processes played a major role - those that took place in time immemorial, when only education. Clouds of cosmic dust “came together”, and thus the “embryos” of planets were formed. Then other cosmic bodies – large and smaller – were “attracted”. It is precisely collisions with large celestial ones, according to a number of scientists, that determine the constant rotation of the planets. And then, according to the theory, they continued to rotate by inertia. True, if we take this theory into account, many natural questions arise. Why are there six planets in the solar system that rotate in one direction, and another one, Venus, in the opposite direction? Why does the planet Uranus rotate in such a way that there is no change in time of day on this planet? Why can the speed of rotation of the earth change (slightly, of course, but still)? Scientists have yet to answer all these questions. It is known that the Earth tends to slow down its rotation somewhat. Every century, the time for a complete rotation around an axis increases by approximately 0.0024 seconds. Scientists attribute this to the influence of the Earth's satellite, the Moon. Well, about the planets of the solar system, we can say that the planet Venus is considered the “slowest” in terms of rotation, the fastest is Uranus.

Sources:

• Every six years the Earth spins faster - Naked Science

Our planet is in constant motion. Together with the Sun, it moves in space around the center of the Galaxy. And she, in turn, moves in the Universe. But the rotation of the Earth around the Sun and its own axis plays the greatest importance for all living things. Without this movement, conditions on the planet would be unsuitable for supporting life.

solar system

According to scientists, the Earth as a planet in the solar system was formed more than 4.5 billion years ago. During this time, the distance from the luminary practically did not change. The speed of the planet's movement and the gravitational force of the Sun balanced its orbit. It's not perfectly round, but it's stable. If the gravity of the star had been stronger or the speed of the Earth had noticeably decreased, then it would have fallen into 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 optimal 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 at a greater distance, 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 circular. 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 ensures a corresponding change in daily patterns and annual periods.

For humans, 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 about 30 km in space. This seems unrealistic, but these 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 full revolution around the star in 365 days. The distance traveled per year is almost a billion kilometers.

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

The planet does not complete a full revolution in exactly 365 days, as is commonly believed. In this case, about six more hours pass. But for the convenience of chronology, this time is taken into account for a total of 4 years. As a result, one additional day “accumulates”; it is added in February. This year is considered a leap year.

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

Change of seasons

The Earth's rotation around the Sun and the tilt of the planet's axis make the seasons possible. This 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 unevenly by the energy of the Sun.

Moving around the star, they pass four conventional orbital points. At the same time, alternately twice during the six-month cycle they find themselves 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 there is higher. The period in such a territory is usually called summer. In the other hemisphere it is noticeably colder at this time - it is winter there.

After three months of such movement with a periodicity of six months, the planetary axis is positioned 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 begin.

Earth's axis

Our planet is a rotating ball. Its movement is carried out around a conventional axis and occurs according to the principle of a top. By resting its base on the plane in an untwisted state, it will maintain balance. When the rotation speed weakens, the top falls.

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

The earth's axis does not pass perpendicularly through the globe of the planet. It is inclined at an angle of 66°33´. The rotation of the Earth around its axis and the Sun makes possible the change of seasons. The planet would “tumble” in space if it did not have a strict orientation. There would be no talk 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 throughout 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 approximately 24 hours. This period is called a day.

The speed of rotation determines the speed 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/sec. Closer to the poles this figure decreases. At the thirtieth latitude, the linear speed will already be 1445 km/h (400 m/sec).

Due to its axial rotation, the planet has a somewhat compressed shape at the poles. This movement also “forces” moving objects (including air and water flows) to deviate from their original direction (Coriolis force). Another important consequence of this rotation is the ebb and flow of tides.

the change of night and day

A spherical object is only half illuminated by a single light source at a certain moment. In relation to our planet, in one part of it there will be daylight at this moment. The unlit part will be hidden from the Sun - it is night there. Axial rotation makes it possible to alternate 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 cyclicality 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 heat up excessively or cool down below the optimal level.

The rotation of the Earth around the Sun and its axis at a relatively constant speed is of decisive importance for the animal world. Without a constant orbit, the planet would not remain in the optimal heating zone. 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

Throughout its history, humanity 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 is influenced to a certain extent by the ellipse of the orbit and other planets in the system.

Another feature is the change in the length of the day. The Earth's axial rotation occurs unevenly. There are several main reasons. Seasonal variations associated with atmospheric dynamics and precipitation distribution are important. In addition, a tidal wave directed against the direction of the planet’s movement constantly slows it down. This figure is negligible (for 40 thousand years per 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 influence human life processes and natural phenomena in hydrometeorology and other areas.

Our planet is constantly in motion:

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

Movement of the Earth around its own axis

Rotation of the Earth around its axis(Fig. 1). The earth's axis is taken to be an imaginary line around which it rotates. This axis is deviated by 23°27" from the perpendicular to the ecliptic plane. The Earth's axis intersects with the Earth's surface at two points - the poles - 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 completes a full revolution around its axis in one day.

Rice. 1. Rotation of the Earth around its axis

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

Sidereal day- this is the period of time during which the Earth will turn around its axis in relation to the stars. They are equal to 23 hours 56 minutes 4 seconds.

Sunny day- this is the period of time during which the Earth turns around its axis in relation 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 Earth's surface moves 15° from its original position. But at the same time, the speed of movement is inversely proportional to the geographic latitude: at the equator it is 464 m/s, and at a latitude of 65° it is only 195 m/s.

The rotation of the Earth around its axis in 1851 was proved in his experiment by J. Foucault. 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 ended up on new divisions. This can only happen if the surface of the Earth under the pendulum rotates. The position of the pendulum's swing plane at the equator does not change, because the plane coincides with the meridian. The Earth's axial rotation has important geographical consequences.

When the Earth rotates, 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 rotational 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 inertia forces introduced to take into account the influence of the rotation of a moving reference frame on the relative motion of a material point. Its effect can be briefly expressed as follows: every moving body in the Northern Hemisphere is deflected to the right, and in the Southern Hemisphere - 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 geographical 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 - eastern. 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, and the left bank in the Southern Hemisphere).

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 living and inanimate nature. The circadian rhythm is closely related to light and temperature conditions. The daily variation of temperature, day and night breezes, etc. are well known. Circadian rhythms also occur in living nature - 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 flows in a circadian rhythm.

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

Since 1884, zone time 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 zone. Time in neighboring time zones differs by one hour. The boundaries of the belts are drawn taking into account political, administrative and economic boundaries.

The zero belt is considered to be the Greenwich belt (named after the Greenwich Observatory near London), which runs on both sides of the prime meridian. The time of the prime, or prime, meridian is considered Universal time.

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

For a more rational use of daylight in summer, in 1930, our country introduced maternity time, one hour ahead of the time zone. To achieve this, the clock hands 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, from April to October, time has been moved forward one hour. This is the so called summer time. It is introduced to save energy. In summer, Moscow is two hours ahead of standard time.

The time of 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 believed 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 perihelia(from Greek peri- near, near and helios- Sun) - the point of orbit closest to the Sun - on January 3, the distance is 147 million km. It is winter in the Northern Hemisphere at this time. Greatest distance from the Sun in aphelion(from Greek aro- away from and helios- Sun) - greatest distance from the Sun - July 5th. It is equal to 152 million km. It's summer in the Northern Hemisphere at this time.

Rice. 4. The 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 altitude of the Sun and the position of its sunrise and sunset change, the duration of the light 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 changes 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 throughout the year. This is how the change of seasons occurs, which is characteristic of all planets whose axis of rotation is tilted 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 days, and the summer half-year - 186 days.

As a result of the Earth's movement around the Sun and the tilt of the Earth's axis to the plane of its orbit by 66.5°, our planet experiences not only a change of seasons, 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 in accordance with the seasons in the Northern Hemisphere).

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

Equinox- the moment in time 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 tilt of the Earth's rotation axis around the Sun on the days of the equinoxes March 20-21 and September 22-23 turns out to be neutral with respect to the Sun, and the parts of the planet facing it are evenly 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 equinoxes

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

On the day of the summer solstice, June 21-22, the Earth occupies 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, the latitude of which is 23°27". Not only the polar regions are illuminated around the clock, but also the space beyond them up to a latitude of 66°33" (the 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") is illuminated. Beyond it, the earth's surface is not illuminated on this day.

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

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

On two parallels of the Earth on the days of the solstices, the Sun at noon is directly above the observer’s head, i.e. at the zenith. Such parallels are called the tropics. In the Northern Tropic (23° N) the Sun is at its zenith on June 22, in the Southern Tropic (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 pronounced.

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 the pole is from the Arctic Circle, the longer the polar day. At the latitude of the Arctic Circle (66.5°) it lasts only one day, and at the pole - 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 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 zones. The hot zone lies between the Northern and Southern tropics (Tropic of Cancer and 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 light zones. The seasons of the year are already expressed here: the further from the tropics, the shorter and cooler the summer, the longer and colder the winter. The polar zones in the Northern and Southern Hemispheres are limited by the Arctic Circles. Here the height of the Sun above the horizon is low throughout the year, 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, not only the change of seasons and the associated unevenness of illumination of the earth’s surface across latitudes, but also a significant part of the processes in the geographical envelope: seasonal changes in weather, the regime of rivers and lakes, rhythms in the life of plants and animals, types and timing 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, and changes in 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 length of the Julian year is 11 minutes 14 seconds longer than the astronomical one, by the 16th century. an “error” of 10 days accumulated - the day of the vernal equinox did not occur on March 21, but on March 11. This error was corrected in 1582 by decree of Pope Gregory XIII. The count of days was moved forward 10 days, and the day after October 4 was prescribed to be considered Friday, but not October 5, but October 15. The vernal equinox was again returned to March 21, and the calendar began to be called the Gregorian calendar. It was introduced in Russia in 1918. However, it also has a number of disadvantages: unequal length of months (28, 29, 30, 31 days), inequality of quarters (90, 91, 92 days), inconsistency of the numbers of months by day of the week.

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). An 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 location points on the earth’s surface rotate, with a linear rotation speed of surface of the globe depends on the position relative 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 the higher it is, the further the object is removed from the axis of rotation).

For example, at the mid-latitudes of Italy the rotation speed is approximately 1200 km/h, at the equator it is maximum and amounts to 1670 km/h, while at the poles it is zero. The consequences of the Earth's rotation 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 movement 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 - a continuation of the earth's axis in a northerly direction. The movement of the stars is not proof that the Earth rotates around its axis, because this movement could be a consequence of the rotation of the celestial sphere, if we assume that the planet occupies a fixed, motionless position in space, as was previously thought.

Day. What are sidereal and solar days?

A day is the length of time during which the Earth makes a complete revolution around its own axis. There are two definitions of the concept “day”. A “solar day” is a period of time for 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 length of the two types of days differs from each other. A sidereal day is 23 hours 56 minutes 4 seconds, while the duration of a solar day is slightly longer and is 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's easier to figure this out with the help of a drawing.

Solar and sidereal days. Explanation.

Let us consider two positions (see figure) that the Earth occupies as it moves along its orbit around the Sun, “ A" - the observer's place 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 any star, which we define as the reference point. 2 - the position of our planet after completing a revolution around its own axis relative to this star: the light of this star, and it is located at a great distance, will reach us parallel to the direction 1 . When the Earth takes its position 2 , we can talk about “sidereal days”, because The Earth has made a full revolution around its axis relative to the distant star, but not yet relative to the Sun. The direction of observing the Sun has changed somewhat due to the rotation of the Earth. In order for the Earth to make a full revolution around its own axis relative to the Sun (“solar day”), you need to wait until it “turns” about 1° more (equivalent to the daily movement of the Earth at an angle - it travels 360° in 365 days), this It will take just about four minutes.

In principle, the length of a solar day (although it is taken to be 24 hours) is not a constant value. This is due to the fact that the Earth's orbital movement actually occurs at a variable speed. When the Earth is closer to the Sun, its orbital speed is higher; as it moves away from the sun, the speed decreases. In this regard, a concept such as "average solar day", precisely their duration is twenty-four hours.

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

Revolution around the Sun is the second main movement of our planet. The Earth moves in an elliptical orbit, i.e. the orbit has the shape of an ellipse. 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.e.). The speed at which the Earth moves in 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 entire orbit.

From the point of view of an observer on Earth, the revolution results in 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 Earth's revolution around the Sun. The reason for seasonal changes is the inclination of the Earth's rotation axis to the plane of its orbit. Moving along 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 inclination of the orbit, as a result of which the Earth tilts towards the Sun with one hemisphere and then 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 its longest movement over the horizon during the day, and the length 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 during the solstice.

Seasons in the Northern Hemisphere

Annual movement of the Earth

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

The time interval during which our planet completes its orbit around the Sun is called a year. However, the length of the year differs depending on whether the starting point is taken to measure it infinitely distant star or Sun.

In the first case we mean “sidereal year” (“sidereal year”) . It is equal 365 days 6 hours 9 minutes and 10 seconds and represents the time required for the Earth to completely revolve 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 occurs due to the precession of the equinoxes; every year the equinoxes (and, accordingly, the sun stations) come “earlier” by approximately 20 minutes. compared to the previous year. Thus, the Earth moves 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 taken as a basis "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 flowing time, not related to the rotation of the Earth and called ephemeris time, was introduced.

Read more about ephemeris time in the section: .

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Japan

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Ra

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36

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East

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Round

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Rotation of the Earth around its axis

The Earth rotates around an axis from west to east, that is, counterclockwise when looking at the Earth from the North Star (North Pole). In this case, the angular velocity of rotation, i.e. the angle through which any point on the Earth’s surface rotates, is the same and amounts to 15° per hour. Linear speed depends on latitude: at the equator it is highest - 464 m/s, and the geographic poles are stationary.

The main physical proof of the Earth's rotation around its axis is the experiment with Foucault's swinging pendulum. After the French physicist J. Foucault c. In the Parisian Pantheon he carried out his famous experiment, the rotation of the Earth around its axis became an immutable truth.

Physical evidence of the Earth’s axial rotation is also provided by measurements of the arc of the 1° meridian, which is at the equator and at the poles. These measurements prove the compression of the Earth at the poles, and this is characteristic only of rotating bodies. And finally, the third proof is the deviation of falling bodies from the plumb line at all latitudes except the poles. The reason for this deviation is due to their inertia maintaining a higher linear velocity of point A (at altitude) compared to point B (near the earth's surface). When falling, objects are deflected to the east on the Earth because it rotates from west to east. The magnitude of the deviation is maximum at the equator. At the poles, bodies fall vertically, without deviating from the direction of the earth's axis.

The geographic significance of the Earth's axial rotation is extremely large. First of all, it affects the figure of the Earth. The compression of the Earth at the poles is the result of its axial rotation. Previously, when the Earth rotated at a higher angular velocity, the polar compression was greater. The lengthening of the day and, as a consequence, a decrease in the equatorial radius and an increase in the polar one is accompanied by tectonic deformations of the earth's crust (faults, folds) and a restructuring of the Earth's macrorelief.

An important consequence of the axial rotation of the Earth is the deviation of bodies moving in the horizontal plane (winds, rivers, sea currents, etc.) from their original direction: in the northern hemisphere - to the right, in the southern - to the left (this is one of the forces of inertia, called the Coriolis acceleration in honor to the French scientist who first explained this phenomenon).

According to the law of inertia, every moving body strives to maintain unchanged the direction and speed of its movement in world space.

Deflection is the result of the body participating in both translational and rotational movements simultaneously. At the equator, where the meridians are parallel to each other, their direction in world space does not change during rotation and the deviation is zero. Toward the poles, the deviation increases and becomes greatest at the poles, since there each meridian changes its direction in space by 360° per day. The Coriolis force is calculated by the formula F=m*2w*v*sinj, Where F– Coriolis force, m– mass of a moving body, w– angular velocity, v– speed of a moving body, j– geographical latitude. The manifestation of the Coriolis force in natural processes is very diverse. It is because of it that vortices of different scales arise in the atmosphere, including cyclones and anticyclones, winds and sea currents deviate from the gradient direction, influencing the climate and through it the natural zonality and regionality; The asymmetry of large river valleys is associated with it: in the northern hemisphere, many rivers (Dnieper, Volga, etc.) for this reason have steep right banks, left banks are flat, and in the southern hemisphere it’s the other way around.

The rotation of the Earth is associated with a natural unit of time - the day - and there is a change between day and night. There are sidereal and sunny days. Sidereal day is the time interval between two successive upper culminations of a star through the meridian of the observation point. During a sidereal day, the Earth makes a complete rotation around its axis. They are equal to 23 hours 56 minutes 4 seconds. Sidereal days are used for astronomical observations. A true solar day is the time interval between two successive upper culminations of the center of the Sun through the meridian of the observation point. The length of the true solar day varies throughout the year, primarily due to the uneven movement of the Earth along its elliptical orbit. Therefore, they are also inconvenient for measuring time. For practical purposes, the average solar day is used. Mean solar time is measured by the so-called mean Sun - an imaginary point that moves evenly along the ecliptic and makes a full revolution per year, like the true Sun. The average solar day is 24 hours long. They are longer than sidereal days, since the Earth rotates around its axis in the same direction in which it moves in its orbit around the Sun with an angular velocity of about 1° per day. Because of this, the Sun moves against the background of the stars, and the Earth still needs to “turn” by about 1° for the Sun to “come” to the same meridian. Thus, during a solar day, the Earth rotates approximately 361°. To convert true solar time to mean solar time, a correction is introduced - the so-called equation of time.

Its maximum positive value was +14 min on February 11, its greatest negative value was -16 min on November 3. The beginning of the average solar day is taken to be the moment of the lowest culmination of the average Sun - midnight. This counting of time is called civil time.

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More articles about the Earth as a planet

When viewed from the North Pole, the Earth rotates counterclockwise, and when viewed from the South Pole, it rotates clockwise. And the Earth (like all the planets of the solar system, except Venus) rotates around its axis counterclockwise. The snail's house spins clockwise from the center (that is, the rotation occurs in a counterclockwise direction). What else is spinning and spinning? One cat’s tail spins clockwise when it sees sparrows (these are her favorite birds), and if they are not sparrows, but other birds, then it spins counterclockwise.

Therefore, experimental evidence of the rotation of the Earth comes down to the proof of the existence of these two inertial forces in the reference frame associated with it. This effect should be most clearly expressed at the poles, where the period of complete rotation of the pendulum plane is equal to the period of rotation of the Earth around its axis (sidereal day).

There are a number of other experiments with pendulums used to prove the rotation of the Earth. The first such experiment was carried out by Hagen in 1910: two weights on a smooth crossbar were installed motionless relative to the surface of the Earth. Then the distance between the loads was reduced.

There are a number of other experimental demonstrations of the Earth's daily rotation. In general, the reason for the precession and nutation of the Earth is its non-sphericity and the mismatch of the equator and ecliptic planes.

As a result of the gravitational attraction of the Moon and the Sun at the equatorial thickening of the Earth, a moment of force arises that tends to combine the planes of the equator and ecliptic.

The explanation of the daily rotation of the sky by the rotation of the Earth around its axis was first proposed by representatives of the Pythagorean school, the Syracusans Hicetus and Ecphantus. About a century later, the assumption of the rotation of the Earth became part of the first heliocentric system of the world, proposed by the great astronomer Aristarchus of Samos (3rd century BC).

The fact that the idea of ​​the daily rotation of the Earth had its supporters back in the 1st century AD. e., evidenced by some statements of the philosophers Seneca, Dercyllidas, and the astronomer Claudius Ptolemy.

Clockwise or counterclockwise?

One of Ptolemy's arguments in favor of the immobility of the Earth is the verticality of the trajectories of falling bodies, just like Aristotle. From the work of Ptolemy it follows that supporters of the hypothesis of the rotation of the Earth responded to these arguments that both air and all earthly objects move together with the Earth.

At the same time, he, however, rejected one of Varahamihira’s arguments: in his opinion, even if the Earth rotated, objects could not come off it due to their gravity. The possibility of the rotation of the Earth was considered by many scientists of the Muslim East. However, the role of air was no longer considered fundamental: not only air, but also all objects are transported by the rotating Earth.

A special position in these disputes was taken by the third director of the Samarkand Observatory, Alauddin Ali al-Kushchi (XV century), who rejected the philosophy of Aristotle and considered the rotation of the Earth physically possible.

In his opinion, astronomers and philosophers have not provided sufficient evidence to refute the rotation of the Earth. Buridan and Oresme rightly disagreed with this, according to whom celestial phenomena should occur in the same way regardless of whether the rotation is made by the Earth or the Cosmos. If the Earth rotates, then the arrow flies vertically upward and at the same time moves east, being captured by the air rotating with the Earth.

Basic movements of the Earth in space.

However, Oresme's final verdict on the possibility of the Earth's rotation was negative. Thus, the main role in the unobservability of the Earth’s rotation is played by the entrainment of air by its rotation. When refuting the arguments of opponents of the hypothesis about the rotation of the Earth, Bruno also used the theory of impetus. He also predicted that due to the action of centrifugal force, the Earth should be flattened at the poles. A number of objections to the rotation of the Earth were associated with its contradictions with the text of Holy Scripture.

I became interested in the topic of what rotates clockwise and what rotates counterclockwise, and this is what I discovered.

In this case, the axial rotation of the Earth was affected, since the movement of the Sun from east to west is part of the daily rotation of the sky. Since the command to stop was given to the Sun, and not to the Earth, it was concluded that it was the Sun that performed the daily movement. You have set the earth on firm foundations: it will not be shaken forever and ever. Proponents of the rotation of the Earth (notably Giordano Bruno, Johannes Kepler, and especially Galileo Galilei) advocated on several fronts.

See what “EARTH ROTATION” is in other dictionaries:

What kind of news is this? In the end they would consider him a fool, and he would indeed be a fool. These arguments were considered unconvincing by the Catholic Church, and in 1616 the doctrine of the rotation of the Earth was prohibited, and in 1631

Galileo was convicted by the Inquisition for his defense. It must be added that religious arguments against the movement of the Earth were given not only by church leaders, but also by scientists (for example, Tycho Brahe).

Annual movement of the Earth.

According to the law of right-hand traffic adopted in our country, circular traffic goes counterclockwise. That is, in some countries helicopters are made with a rotor rotating clockwise, and in others - counterclockwise.

Flocks of bats, flying out of caves, usually form a “right-handed” vortex. But in the caves near Karlovy Vary (Czech Republic), for some reason they spin in a spiral, twisted counterclockwise... But the dog, before going on business, will definitely spin counterclockwise. The spiral staircases in the castles were twisted clockwise (if viewed from below, and counterclockwise if viewed from above) - so that it would be inconvenient for attackers to attack when ascending.