The rotation of the Earth around its axis and the Sun occurs continuously. Many phenomena depend on this movement. So, day is followed by night, one season is another, in different areas a different climate is established.
Daily rotation Earth, according to scientists, is 23 hours, 56 minutes, 4.09 seconds. Thus, one complete revolution occurs. The planet rotates around its axis at a speed of approximately 1,670 km / h. Towards the poles, the speed decreases to zero.
A person does not notice rotation due to the fact that all objects located next to him move simultaneously and in parallel with the same speed.
Carried out in orbit. It is located on an imaginary surface passing through the center of our planet and This surface is called the orbital plane.
An imaginary line between the poles - the axis - runs through the center of the earth. This line and the plane of the orbit are not perpendicular. The tilt of the axis is approximately 23.5 degrees. The tilt angle is always the same. The line around which the Earth moves is always tilted to one side.
Orbiting the planet takes a year. In this case, the rotation of the Earth is carried out counterclockwise. It should be noted that the orbit is not perfectly circular. The average distance to the Sun is about one hundred and fifty million kilometers. It (distance) changes by an average of three million kilometers, thus forming an insignificant orbital oval.
The Earth's orbital revolution is 957 million km. The planet covers this distance in three hundred and sixty-five days, six hours, nine minutes and nine and a half seconds. According to calculations, the Earth's orbital rotation occurs at a speed of 29 kilometers per second.
Scientists have found that the movement of the planet is slowing down. This is mainly due to tidal braking. On the surface of the Earth, under the influence of the attraction of the Moon (in to a greater extent) and the Sun, tidal waves are formed. They move from east to west (following these in the opposite direction to the movement of our planet.
Less importance is attached to the tides in the lithosphere of the Earth. In this case, deformation occurs solid somewhat delayed tidal wave... It provokes the emergence of a braking moment, which contributes to the fact that the rotation of the Earth slows down.
It should be noted that the tides in the lithosphere affect the deceleration of the planet by only 3%, the remaining 97% are due to sea tides... This data was obtained as a result of the creation of maps of the waves of lunar and solar tides.
The speed of the Earth is also influenced by atmospheric circulation. It is believed to be the main cause of the seasonal uneven atmosphere occurring from east to west in low latitudes, and from west to east in high and temperate latitudes. At the same time, the westerly winds have a positive angular momentum, while those of the easterly winds are negative and, according to calculations, are several times less than that of the former. This difference is redistributed between the Earth and the atmosphere. With the strengthening of the westerly wind or the weakening of the east one, it increases in the atmosphere, and decreases near the Earth. Thus, the movement of the planet slows down. With the strengthening of the eastern winds and the weakening of the western ones, respectively, the angular momentum of the atmosphere decreases. Thus, the movement of the Earth becomes faster. The total angular momentum of the atmosphere and the planet is constant.
Scientists managed to find out that the lengthening of the day until 1620 occurred on average by 2.4 milliseconds per hundred years. After that year, the value decreased by almost half and became 1.4 milliseconds per hundred years. Moreover, according to some recent calculations and observations, the Earth slows down by an average of 2.25 milliseconds per hundred years.
The Earth rotates around an axis from west to east, i.e. counterclockwise, if you look at the Earth from the North Star (from the North Pole). In this case, the angular speed of rotation, that is, the angle by which any point on the surface of the Earth rotates, is the same and amounts to 15 ° per hour. Linear velocity depends on latitude: at the equator it is greatest - 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 in 1851 in the Paris Pantheon 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 1 ° meridian arc, which is 110.6 km at the equator and 111.7 km at the poles (Fig. 15). These measurements prove the compression of the Earth at the poles, and it 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 for the poles (Fig. 16). The reason for this deviation is due to their preservation by inertia of a greater linear velocity of the point A(at height) compared to the point V(near the earth's surface). When falling, objects are deflected to the east on the Earth because it rotates from west to east. The deviation is greatest at the equator. At the poles, bodies fall vertically without deviating from the direction of the earth's axis.
The geographic significance of the axial rotation of the Earth is extremely high. First of all, it affects the shape of the Earth. The compression of the Earth at the poles is the result of its axial rotation. Earlier, when the Earth rotated at a higher angular velocity, the polar contraction was more significant. The lengthening of the day and, as a consequence, the decrease in the equatorial radius and the increase in the polar one are accompanied by tectonic deformations. crust(faults, folds) and restructuring of the Earth's macro-relief.
An important consequence of the axial rotation of the Earth is the deflection 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 south - to the left(this is one of the forces of inertia, named the Coriolis acceleration after the French scientist who first explained this phenomenon). According to the law of inertia, each moving body strives to keep the direction and speed of its movement in the world space unchanged (Fig. 17). Deviation is the result of the body participating simultaneously in both translational and rotational movements. 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. The deviation increases towards the poles and becomes the 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 x 2ω x υ x sin φ, where F - Coriolis force, T- mass of a moving body, ω - angular velocity, υ - speed of a moving body, φ - latitude. The manifestation of the Coriolis force in natural processes is very diverse. It is because of it that eddies of various scales arise in the atmosphere, including cyclones and anticyclones, winds and sea currents deviate from the gradient direction, influencing the climate and, through it, on natural zonality and regionality; it is associated with the asymmetry of large river valleys: in the northern hemisphere, many rivers (Dnieper, Volga, etc.) for this reason, the right banks are steep, the left ones are gentle, and in the southern hemisphere it is vice versa.
The natural unit of time is associated with the rotation of the Earth - day and happens the change of night and day. The day is starry and sunny. Stellar day- the time interval between two successive upper climaxes of a star across the meridian of the observation point. For a sidereal day, the Earth makes a complete revolution around its axis. They are equal to 23 hours 56 minutes 4 seconds. Sidereal days are used for astronomical observations. True solar day- the time interval between two successive upper culminations of the center of the Sun through the meridian of the observation point. The duration of true solar days varies throughout the year primarily due to the uneven motion of the Earth in an elliptical orbit. Hence, they are also inconvenient for measuring time. For practical purposes use average sunny days. Average solar time is measured by the so-called average sun - an imaginary point that moves uniformly along the ecliptic and makes a full revolution per year, like the true sun. Average solar days are 24 hours. They are longer than stellar days, since the Earth rotates around its axis in the same direction in which it orbits the Sun with an angular velocity of about 1 ° per day. Because of this, the Sun shifts against the background of the stars, and the Earth still needs to "turn around" by about 1 ° in order for the Sun to "come" to the same meridian. Thus, for a solar day, the Earth makes a revolution by about 361 °. To translate true solar time into mean solar time, an amendment is introduced - the so-called equation of time. Its maximum positive value+ 14 minutes on February 11, the largest negative –16 minutes on November 3. The beginning of the average solar day is taken to be the moment of the lower climax of the average Sun - midnight. This counting of time is called civil time.
In everyday life, it is also inconvenient to use the average solar time, since it has its own on each meridian, local time. For example, on two adjacent meridians, drawn at an interval of 1 °, the local time differs by 4 minutes. The presence of their local time at different points lying on different meridians led to many inconveniences. Therefore, at the International Astronomical Congress in 1884, the standard time count was adopted. For this, the entire surface of the globe was divided into 24 time zones, 15 ° each. Per standard time the local time of the middle meridian of each belt is taken. To convert local time to standard time and vice versa, there is a formula T n – m = N – λ °, where T NS - standard time, m - local time, N- the number of hours equal to the zone number, λ ° - longitude, expressed in hourly measure. The zero (aka 24th) belt is the one in the middle of which the zero (Greenwich) meridian passes. Its time is taken as universal time. Knowing the universal time, it is easy to calculate the standard time using the formula T n = T 0 + N, where T 0 - universal time. The belts are counted to the east. In two neighboring zones, zone time differs by exactly 1 hour. For convenience, the boundaries of time zones on land are drawn not strictly along the meridians, but along natural boundaries (rivers, mountains) or state and administrative boundaries.
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In our country, standard time was introduced on July 1, 1919. Russia is located in ten time zones: from the second to the eleventh. However, in order to more efficiently use daylight in summer in our country in 1930, a special government decree introduced the so-called daylight saving time, leading the zone time by 1 hour. For example, Moscow is formally located in the second time zone, where zone time is calculated according to the local time of the meridian 30 ° E. But in fact, the time in winter in Moscow is set according to the time of the third time zone, corresponding to the local time on the meridian 45 ° E. e. Such a "movement" is valid throughout the territory of Russia, except Kaliningrad region, the time in which actually corresponds to the second time zone. |
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Rice. 17. Deviation of bodies moving along the meridian, in the northern hemisphere - to the right, in the southern hemisphere - to the left |
In a number of countries, the time is shifted one hour ahead only for the summer. In Russia, from 1981 for the period from April to October, summer time due to the transfer of time one more hour ahead of the maternity. Thus, in summer, the time in Moscow actually corresponds to the local time on the meridian 60 ° E. The time according to which residents of Moscow and the second time zone in which it is located live is called Moscow. Moscow time in our country is the timetable for the movement of trains, airplanes, the time is noted on telegrams.
In the middle of the twelfth belt, approximately along the 180 ° meridian, in 1884 was drawn international date line. This is a conditional line on the surface of the globe, on either side of which hours and minutes coincide, and calendar dates differ by one day. For example, on New Year's Eve at 00:00 to the west of this line, there is already January 1 of the new year, and to the east - only December 31 of the old year. When crossing the border of dates from west to east in the count of calendar days, they go back one day, and from east to west, one day in the count of dates is skipped.
The change of day and night creates daily rhythm in living and inanimate nature. The daily rhythm is associated with light and temperature conditions. The diurnal variation of temperature, day and night breezes, etc. is well known. The diurnal rhythm of living nature is very clearly manifested. It is known that photosynthesis is possible only during the day, if sunlight that many plants open their flowers at different times. According to the time of manifestation of activity, animals can be divided into nocturnal and daytime: most of them are awake during the day, but many (owls, bats, moths) - in the darkness of the night. Human life also proceeds in a daily rhythm.
Rice. 18. Twilight and White Nights
The period of smooth transition from daylight to night darkness and back is called twilight. V they are based on an optical phenomenon observed in the atmosphere before sunrise and after sunset, when it is still (or already) under the horizon, but illuminates the firmament, from which the light is reflected. The duration of twilight depends on the declination of the Sun (the angular distance of the Sun from the plane of the celestial equator) and the latitude of the observation site. At the equator, twilight is short, increasing with latitude. There are three periods of twilight. Civil twilight observed when the center of the Sun plunges under the horizon shallowly (at an angle of up to 6 °) and not for long. This is actually White Nights, when the evening dawn converges with the morning dawn. In summer, they are observed at latitudes of 60 ° and more. For example / in St. Petersburg (latitude 59 ° 56 "N) they continue from June 11 to July 2, in Arkhangelsk (64 ° 33" N) - from May 13 to July 30. Nautical twilight observed when the center of the solar disk plunges 6–12 ° below the horizon. In this case, the horizon line is visible, and from the ship you can determine the angle of the stars above it. Finally, astronomical twilight observed when the center of the Sun's disk plunges 12–18 ° below the horizon. Moreover, the dawn in the sky still interferes with astronomical observations of faint luminaries (Fig. 18).
The rotation of the Earth gives two fixed points - geographic poles(the point of intersection of the imaginary axis of rotation of the Earth with the earth's surface) - and thus allows you to build a coordinate grid from parallels and meridians. Equator(lat. aequator - equalizer) - the line of intersection of the globe with a plane passing through the center of the Earth perpendicular to the axis of its rotation. Parallels(Greek. parallelos - going side by side) - the lines of intersection of the earth's ellipsoid by planes parallel to the equatorial plane. Meridians(lat. meridlanus - midday) - the lines of intersection of the earth's ellipsoid by planes passing through both of its poles. The length of the 1 ° meridian is 111.1 km on average.
The earth is always in motion. Although it seems that we are standing motionless on the surface of the planet, it continuously revolves around its axis and the sun. This movement is not felt by us, as it resembles a flight in an airplane. We are moving at the same speed as the plane, so we do not feel that we are moving at all.
At what speed does the Earth rotate on its axis?
The Earth makes one revolution on its axis in almost 24 hours (to be precise, for 23h 56min 4.09sec or 23.93 hours)... Since the circumference of the Earth is 40,075 km, then any object on the equator rotates at a speed of approximately 1,674 km per hour or approximately 465 meters (0.465 km) per second (40,075 km is divided by 23.93 hours and we get 1,674 km per hour).
At (90 degrees north latitude) and (90 degrees south latitude), the speed is effectively zero because the pole points rotate at a very slow speed.
To determine the speed at any other latitude, simply multiply the cosine of latitude by the planet's rotation speed at the equator (1674 km per hour). The cosine of 45 degrees is 0.7071, so multiply 0.7071 by 1674 km per hour and get 1183.7 km per hour.
The cosine of the required latitude can be easily determined using a calculator or look at the cosine table.
Earth's rotation rate for other latitudes:
- 10 degrees: 0.9848 × 1674 = 1648.6 km per hour;
- 20 degrees: 0.9397 × 1674 = 1573.1 km per hour;
- 30 degrees: 0.866 × 1674 = 1449.7 km per hour;
- 40 degrees: 0.766 × 1674 = 1282.3 km per hour;
- 50 degrees: 0.6428 × 1674 = 1076.0 km per hour;
- 60 degrees: 0.5 × 1674 = 837.0 km per hour;
- 70 degrees: 0.342 × 1674 = 572.5 km per hour;
- 80 degrees: 0.1736 × 1674 = 290.6 km per hour.
Cyclic braking
Everything is cyclical, even the speed of rotation of our planet, which geophysicists can measure with an accuracy of milliseconds. The Earth's rotation typically has five-year deceleration and acceleration cycles, and Last year the slowing cycle is often correlated with the burst of earthquakes around the world.
Since 2018 is the last slowdown in a cycle, scientists expect growth this year seismic activity... Correlation is not causal, but geologists are always looking for tools to try and predict when the next massive earthquake will hit.
Vibrations of the earth's axis
The earth wobbles slightly as it rotates as its axis drifts at the poles. It has been observed that the Earth's axis drift has accelerated since 2000, moving at a speed of 17 cm per year to the east. Scientists have found that the axis is still moving east instead of moving back and forth due to the combined effects of Greenland melting and water loss in Eurasia.
Axis drift is assumed to be particularly sensitive to changes occurring at 45 degrees north and south latitude. This discovery led scientists to finally answer the long-standing question of why the axis drifts at all. The wobble to the East or West was caused by dry or wet years in Eurasia.
How fast is the earth moving around the sun?
In addition to the speed of the Earth's rotation on its axis, our planet also orbits the Sun at a speed of about 108,000 km per hour (or about 30 km per second), and fully completes its orbit around the Sun in 365.256 days.
Only in the 16th century did people realize that the Sun is the center of our Solar system, and that the Earth moves around him, and is not the stationary center of the universe.
A theory about the world like geocentric system, in the old days, was repeatedly criticized and doubted. It is known that Galileo Galilei worked on the proof of this theory. This is the phrase that went down in history belongs to him: “And yet it turns!”. But still, he did not manage to prove this, as many think, but Nicolaus Copernicus, who in 1543 wrote a treatise on the movement of celestial bodies around the Sun. Surprisingly, despite all this evidence, about the circular course of the Earth around a huge luminary, in theory there are still open questions about the reasons that prompted it to this movement.
Reasons for movement
The Middle Ages are over, when people considered our planet to be motionless, and no one disputes its movements. But the reasons why the Earth is heading around the Sun are not known for certain. Three theories have been put forward:
- inert rotation;
- magnetic fields;
- exposure to solar radiation.
There are others, but they don't stand up to scrutiny. It is also interesting that the question: "In which direction does the Earth rotate around a huge celestial body?" Is also not correct enough. The answer has been received, but it is accurate only in relation to the generally accepted reference point.
The sun is a huge star around which life is concentrated in our planetary system. All these planets move around the Sun in their orbits. The earth is moving in a third orbit. Studying the question: "In which direction does the Earth rotate in its orbit?", Scientists have made many discoveries. They realized that the orbit itself is not ideal, so our green planet is located from the Sun at different points at different distances from each other. Therefore, the average was calculated: 149.6 million km.
The Earth is closest to the Sun on January 3, and further - on July 4. The concepts are associated with these phenomena: the smallest and largest temporary day in the year, in relation to the night. Studying the same question: "In which direction does the Earth rotate in its solar orbit?" Having made the discoveries of these two rotations, scientists asked questions not only about the reasons for such phenomena, but also about the shape of the orbit, as well as the speed of rotation.
How did scientists determine in which direction the Earth rotates around the Sun in the planetary system?
The orbital picture of the planet Earth was described by a German astronomer and mathematician. In his fundamental work "New Astronomy" he calls the orbit elliptical.
All objects on the Earth's surface rotate with it, using generally accepted descriptions of the planetary picture of the solar system. We can say that, observing from the north from space, to the question: "In which direction does the Earth rotate around the central star?", The answer will be as follows: "From west to east."
Comparing with the movements of the hands in hours - this is against its course. This point of view was adopted regarding the North Star. The same will be seen by a person on the surface of the Earth from the side of the Northern Hemisphere. Imagining himself on a ball moving around a stationary body, he will see its rotation from right to left. This is tantamount to walking against the clock hand or from west to east.
Earth axis
All this also applies to the answer to the question: "In which direction does the Earth rotate around its axis?" - in the opposite direction of the clock hands. But if you imagine yourself as an observer in the Southern Hemisphere, the picture will look different - on the contrary. But, realizing that in space the concepts of west and east are absent, scientists pushed off from the earth's axis and the North Star, to which the axis is directed. This determined the generally accepted answer to the question: "In which direction does the Earth rotate around its axis and around the center of the solar system?" Accordingly, the Sun is shown in the morning from the horizon with east direction, but hides from our eyes in the west. Interestingly, many people compare the earth's revolutions around its own invisible axial rod with the rotation of a top. But at the same time, the earth's axis is not visible and is somewhat tilted, rather than vertical. All this is reflected in the shape of the globe and the elliptical orbit.
Sidereal and solar days
In addition to answering the question: "In which direction does the Earth rotate clockwise or counterclockwise?", Scientists calculated the time of revolution around its invisible axis. It is 24 hours. The interesting thing is that this is only an approximate number. In fact, the total revolution is 4 minutes less (23 hours 56 minutes 4.1 seconds). This is the so-called star day. We count the day by sunny day: 24 hours, since the Earth in its planetary orbit every day needs an additional 4 minutes to return to its place.
Like other planets of the solar system, it makes 2 main movements: around its own axis and around the sun. Since ancient times, it is these two regular movements that have been the basis for timing and the ability to draw up calendars.
Day is the time of rotation around its own axis. Year - revolutions around the sun. The division into months is also directly related to astronomical phenomena - their duration is associated with the phases of the moon.
Rotation of the Earth around its own axis
Our planet rotates around its own axis from west to east, that is, counterclockwise (when viewed from the side North Pole.) An axis is a virtual straight line crossing Earth in the North and South Poles, i.e. poles have a fixed position and do not participate in rotary motion, while all other points of location on the earth's surface rotate, and the rotation speed is not identical and depends on their position in relation to the equator - the closer to the equator, the higher the rotation speed.
For example, in the region of Italy, the rotation speed is approximately 1200 km / h. 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 others celestial bodies of the night sky move in the direction opposite to our motion with the planet (that is, from east to west).
It seems that the stars are located 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 assume that the planet occupies a fixed, stationary position in space.
Foucault's pendulum
Irrefutable proof that the earth rotates on its own axis was presented in 1851 by Foucault, who conducted the famous experiment with a pendulum.
Imagine that, being at the North Pole, we set a pendulum in oscillatory motion. The force from the outside acting on the pendulum is gravity, and it does not affect the change in the direction of the oscillations. If we prepare a virtual pendulum that leaves footprints on the surface, we can make sure that after a while the footprints will move in the clockwise direction.
This rotation can be associated with two factors: either with the rotation of the plane on which the pendulum is oscillating, or with the rotation of the entire surface.
The first hypothesis can be discarded, taking into account that there are no forces on the pendulum that can change the plane of oscillatory movements. Hence it follows that it is the Earth that rotates, and it makes movements around its own axis. This experiment was carried out in Paris by Foucault, he used a huge pendulum in the form of a bronze sphere weighing about 30 kg, suspended from a 67-meter cable. On the surface of the floor of the Pantheon, the starting point of the oscillatory movements was recorded.
So, it is the Earth that rotates, not the celestial sphere. People observing the sky from our planet record the movement of both the Sun and the planets, i.e. all objects move in the universe.
Time criterion - day
A day is a period of time during which the Earth makes a complete revolution around its own axis. There are two definitions of the term “day”. “Solar day” is the period of time of the Earth's rotation, at which it is taken as the starting point. Another concept - "sidereal day" - implies a different starting point - any star. The duration of the two types of day is not identical. The longitude of a sidereal day is 23 hours 56 minutes 4 s, while the longitude of a solar day is 24 hours.
Different durations are associated with the fact that the Earth, rotating around its own axis, performs and orbital rotation around the sun.
In principle, the duration of a sunny day (although it is taken as 24 hours) is not a constant value. This is due to the fact that the Earth's orbital movement 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 star, the speed decreases. In this regard, such a concept as “average solar day” has been introduced, namely, their duration is 24 hours.
Orbiting the Sun at a speed of 107,000 km / h
The speed of the Earth's revolution around the Sun is the second main motion of our planet. The earth moves in an elliptical orbit, i.e. the orbit is elliptical. When it 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 150 million kilometers. Astronomy uses a unit of measure for distances within the solar system; it is called the “astronomical unit” (au).
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 ', this is a constant value.
If you observe the Sun from the Earth, you get the impression that it is it that moves across the sky during the year, passing through the stars and that make up the Zodiac. In fact, the Sun also passes through the constellation Ophiuchus, but it does not belong to the Zodiacal circle.
