Like other planets solar system, makes 2 main movements: around its own axis and around the Sun. Since ancient times, it is on these two regular movements that the calculation of time and the ability to draw up calendars have been based.
A day is the time of rotation around its own axis. A year is a revolution around the sun. The division into months is also in direct connection with 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 North Pole.) The axis is a virtual straight line that crosses the globe in the region of the North and South Poles, i.e. 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 rotation speed is not identical and depends on their position relative 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 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 located 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 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, immovable position in space.
Foucault pendulum
Irrefutable proof that the Earth rotates on its own axis was presented in 1851 by Foucault, who conducted famous experiment with a pendulum.
Imagine that, being at the North Pole, we set a pendulum in oscillatory motion. The external force acting on the pendulum is gravity, while it does not affect the change in the direction of oscillation. If we prepare a virtual pendulum that leaves tracks on the surface, we can make sure that after a while the tracks move in a clockwise direction.
This rotation can be associated with two factors: either with the rotation of the plane on which the pendulum oscillates, or with the rotation of the entire surface.
The first hypothesis can be rejected, taking into account that there are no forces on the pendulum capable of changing the plane of oscillatory motions. It follows from this 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. The starting point of oscillatory movements was fixed on the surface of the floor of the Pantheon.
So, it is the Earth that rotates, and not the celestial sphere. People observing the sky from our planet fix the movement of both the Sun and the planets, i.e. All objects in the universe are in motion.
Time criterion - day
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 interval of the Earth's rotation, in which . 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 h 56 min 4 s, while the longitude of the solar day is 24 hours.
The different duration is due to the fact that the Earth, rotating around its own axis, also performs an orbital rotation around the Sun.
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 its orbit 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. In this regard, such a concept as “average solar day” was introduced, namely, their duration is 24 hours.
Circulation around the Sun at a speed of 107,000 km / h
The speed of the Earth 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 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 to measure distances within the solar system; it is called the “astronomical unit” (AU).
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 ', this is a constant value.
If you watch the Sun from the Earth, it seems 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 Zodiac circle.
The Earth is one of the celestial bodies that revolve around the Sun. The sun is a star, a flaming ball around which the planets revolve. Together with the Sun, their satellites, many small planets (asteroids), comets and meteor dust, they make up. Earth is the third of eight planets, it has a diameter of about 13 thousand km. The Earth makes one revolution around the Sun in 365 days 5 hours 48 minutes, or in one year. The path of the Earth around the Sun (Earth's orbit) is close in shape to a circle.
Simultaneously with the movement around the Sun around its axis, turning to the Sun with one hemisphere, then the other. The rotation period is approximately 24 hours, or one day. The earth's axis is an imaginary straight line passing through the center of the earth. The axis crosses the Earth's surface at two points: the North and South Poles. At equal distances from the geographic poles, the equator passes - an imaginary line that divides the Earth into two equal hemispheres: Northern and Southern.
The imaginary axis around which the Earth revolves is inclined to the plane of the orbit along which the Earth revolves around the Sun. Because of this, at different times of the year, the Earth is turned towards the Sun with either one pole or the other. When the area around the North Pole faces the Sun, it is summer in the Northern Hemisphere (in which we live) and winter in the Southern Hemisphere. When the area around the South Pole is facing the Sun, then vice versa: in the Southern Hemisphere it is summer, and in the Northern Hemisphere it is winter.
Thus, due to the rotation of the Earth around the Sun, as well as due to the tilt of the earth's axis, the seasons on our planet change. In addition, different parts of the Earth receive different amounts of heat from the Sun, which determines the existence of thermal zones: hot tropical, temperate and cold polar. (You will learn more about the thermal zones of the Earth when studying our planet.)
The earth has an invisible magnetic field. The presence of this field causes the arrow to always point north.
moon
The Earth has a single natural satellite - (at a distance of 384,400 km from the Earth). The moon revolves around the earth. It reflects sunlight, so it seems to us that it glows. Its surface is mountainous, covered with numerous meteorite craters.
From the attraction of the Moon on Earth there are ebbs and flows. They are especially noticeable on the coast of the open ocean. In our country, the tides are especially high in (find it on the map) and in the Far East.
Even in the Ancient One, they noticed the connection between the tides and the movement of the moon across the sky. According to the laws of interaction of cosmic bodies, the Earth attracts the Moon, and the Moon - the Earth. The lunar attraction is so strong that the surface of the ocean curves towards our satellite. The moon moves around the earth, and a tidal wave runs along the ocean behind it. When it reaches the shore, there is a tide. After a while, the water moves away from the coast after the moon.
According to the same laws of interaction of cosmic bodies, the Sun should also influence the water level in the ocean, but it is too far from the Earth, so its influence is much less than that of the Moon.
Date of: 25.10.2015
Our planet performs several types of movement at the same time:
- around its axis - change of day and night(complete rotation occurs in 23 hours 56 minutes and 4 seconds)
- in orbit around the sun - the change of seasons(complete rotation occurs in 365 days and 6 hours)
- with the entire solar system - around the center of the Galaxy,
- around the center of the universe.
In addition, the Earth moves along with its natural satellite - the Moon - around their common center of mass. We do not feel these movements, because we move together with the Earth, and in relation to us, it remains motionless.
The Earth, like other planets, revolves around the Sun. This path of the earth is called orbit. The orbit of the Earth is an ellipse, close to a circle, in one of the focuses of which is the Sun.
The distance from the Earth to the Sun varies throughout the year from 147 million km - at perihelion (in January) - to 152 million km - at aphelion (in July). The length of the orbit is more than 980 million km.
The speed of the Earth in orbit around the Sun is 29.76 km/s. This path the Earth overcomes for 365 days and 6 hours, therefore, the duration of a normal year is 365 days, and the "extra" hours every four years are an additional day on February 29. Such a year lasts 366 days and is called a leap year.. A leap year must be divisible by 4 without a remainder, by this sign it is easy to recognize.
The Earth's axis is permanently inclined to the plane of the Earth's orbit at an angle of 66.5°. Therefore, when moving along the orbit, the Northern and Southern hemispheres are illuminated by the Sun unevenly.
The angle of incidence of solar rays in the Northern Hemisphere is the largest in June, and the smallest - in December. In the Southern Hemisphere, the opposite is true. Therefore, the surface of the Earth is heated unevenly, since heating largely depends on the angle of incidence of the sun's rays.
Twice a year, March 21 And 23 September, on the equator, which separates the two hemispheres, there is a sheer influx of sunlight (the sun is at its zenith). At this time, both hemispheres warm up equally, and therefore there are transitional seasons - spring and autumn.
Characteristic positions of the Earth in circumsolar orbit
|
date of |
||||
|
Location of the Sun at its zenith |
northern tropic |
Equator |
southern tropic |
Equator |
|
Day length in the Northern Hemisphere |
The day is longer than the night |
Day equals night |
The day is shorter than the night |
Day equals night |
|
polar day |
Beyond the Arctic Circle |
Beyond the Antarctic Circle |
||
|
Position of the Sun in the Northern Hemisphere |
Summer solstice |
autumnal equinox |
Winter solstice |
The vernal equinox |
|
Position of the Sun in the Southern Hemisphere |
Winter solstice |
The vernal equinox |
Summer solstice |
autumnal equinox |
The motion of the Earth in orbit and the inclination of its axis of rotation lead to a regular change of seasons and the existence of lighting belts ( thermal zones), which are the basis of climatic zonality and natural zonality in general.
The tropics and polar circles delimit the Earth's surface into five zones of illumination, or thermal zones - territories that differ from each other in the height of the midday position of the Sun above the horizon, the length of the day and, accordingly, temperature conditions.
hot belt lies between the tropics. Within its limits, the Sun is at its zenith twice a year, in the tropics - once a year, on the days of the solstices (and in this they differ from all parallels). In this zone, the length of day and night differs little. The hot belt takes about 40% of the earth's surface.
Temperate zones (northern and southern) situated between the tropics and the polar circles. The sun in them is never at its zenith. During the day, there is a change of day and night, and their duration depends on the latitude and time of year. At the polar circles (from 60 ° to 66.5 °) in summer there are bright, so-called “white nights with twilight illumination due to the merging of the evening star with the morning star, since the Sun sets for a short time and not far behind the horizon. area temperate zones is 52% of the earth's surface.
Cold belts (northern and southern) - north of the northern and south of the southern polar circles. They are distinguished by the presence of polar days and nights, the duration of which increases from one day - at the polar circles - to six months - at the poles. Area of cold belts - 8% of the earth's surface.
As a result of this rotation on the Earth, there is a change of day and night, since the Sun illuminates only one side of the Earth.
Day is the time it takes for the Earth to complete one revolution around its axis. Our planet makes such a revolution in 23 hours 56 minutes 4 seconds (for convenience, it is considered that there are 24 hours in a day). At different points on the surface of the Earth, the speed of rotation is different. It is maximum at the equator - an imaginary line equidistant from the poles, and at the poles it is equal to zero. The capital of Ukraine - Kyiv - rotates around the earth's axis at a speed of approximately 260 m/s.
Important consequence Earth's axial rotation is flow deviations moving horizontally (winds, sea currents, etc.), from their original direction: in the northern hemisphere - to the right, in the southern - to the left(this is the result of the action of one of the forces of inertia, called Coriolis force after the French scientist who first explained this phenomenon). According to the law of inertia, all flesh crumbles, striving to keep the direction and speed of its movement in space unchanged.
Deviation- the result of the fact that the body is involved in both translational and rotational motion. Since the Coriolis force acting on a body is proportional to the sine of the geographic latitude of its location, the deviation at the equator is zero. As we approach the poles, the deviation increases and becomes the largest at the poles.
The rotation of the Earth around its axis and the associated change of day and night creates a daily rhythm of living and inanimate nature. The daily rhythm is mainly associated with light and temperature conditions. The daily course of temperature, day and night breezes, etc. are well known. The daily rhythm of wildlife is very clearly manifested. It is known that photosynthesis is possible only during the day, that many flowers bloom at different times. Animals are divided into nocturnal and those that become active during the day. Human life also proceeds in a daily rhythm. The daily rotation of the Earth causes the tides to change.
Movement of the Earth - the movement of the Earth relative to some chosen coordinate system. The earth is involved in several types of movements:
1) Movement together with the solar system around the center of the Galaxy. One revolution is a galactic year (230 or 280 million years).
Approximately every 230 million years, mountain building processes are activated on Earth, but it has not yet been proven that this is due to the circulation of the solar system around the center of the Galaxy.
The revolution around the Sun, the daily rotation and tilt of the earth's axis lead to the change of seasons.
2) Movement around the Sun in an elliptical orbit close to a circle with a radius of about 149.6 million km. The circulation period is a year. The plane of the orbit is called the plane of the ecliptic.
3) The rotation of the Earth around its axis - one revolution per day.
The rotation of the Earth on its axis has several consequences:
Change of day and night
Flattening of the Earth at the Poles
The emergence of the Coriolis force
More uniform heating of the planet's surface
4) Circulation around the center of mass common with the Moon with a period of 27.32 days.
The circulation of the Earth and the Moon around a common center of mass and the daily rotation of the Earth create ebbs and flows in the hydrosphere, atmosphere and lithosphere.
31. Axial rotation of the Earth
Os. Z.'s rotation occurs from the west. to the east or against the hour. arrows, when viewed from the north. poles of the World. This is the direction of movement. inherent in our entire galaxy.
Rotary axis Z. naz. straight, pass. h / z the center of its mass, around the cat. Z. rotates.
For the nature of the earth. surface os.rotation Z. has great importance:
1. It creates the main. units time - day, dividing into 2 main parts - illuminated and unilluminated .. A physiologist is associated with this unit of time. activities of animals and plants. The change of tension (work) and relaxation (rest) is an internal need of organisms. Its rhythms could be different, but in the process of evolution there was a selection of such organisms, the internal biological "clock" of which "works" daily.
The main synchronizer of biological rhythms is the alternation of light and darkness. It is associated with the rhythm of photosynthesis, cell division and growth, respiration, the glow of algae and much more.
The most important feature of the thermal regime of the earth's surface depends on the day - the change of daytime heating and nighttime cooling. At the same time, not only the change is important, but also their duration.
The daily rhythm is also manifested in inanimate nature: in the heating and cooling of rocks and weathering, temp. mode of reservoirs, temp. air and winds, ground. precipitation.
2. Second noun. value rotation geog. space consists in dividing it into right and left. This causes the paths of moving bodies to deviate to the right in the northern hemisphere and to the left in the southern.
3. Rotate Z. in the field of solar radiation determined west-east. stretch of natural areas.
32. Earth's revolution around the sun
The path of the Earth around the Sun is called an orbit. The Earth's orbit is an ellipse close to a circle. Its length is more than 930 million km. The Earth makes a complete revolution in 365 days 6 hours and 9 minutes. This interval is called a sidereal year. The axis of rotation of the Earth is inclined to the orbit at an angle of 66.5 degrees, this phenomenon contributes to the change of seasons. The inclination of the earth's axis to the plane of the orbit and the preservation of its orientation in space causes a different angle of incidence of the sun's rays and, accordingly, differences in the flow of heat to the earth's surface, and also affects the unequal length of day and night during the year at all latitudes except the equator.
The Earth makes a complete revolution around the Sun in 365 days. 6 h 9 min 9 s. At the end of a sidereal year, an observer from Earth will see the Sun near the same star where it was a year ago. A tropical year, that is, the time interval between two successive passages of the Sun through the points of the vernal equinox, lasts 365 days. 5 h 48 min 46 s; it is about 20 min shorter than the stellar one.
The path of the annual movement of the Earth, or orbit, has the shape of an ellipse, in one of the focuses of which is the Sun. It follows that the distance between the Earth and the Sun varies throughout the year. The Earth is closest to the Sun, or at perihelion, on January 3rd. Then the distance from the Earth to the Sun is 147,000,000 km. On July 5, at aphelion, the Earth moves away from the Sun by 152,000,000 km. The length of the earth's orbit is 940 million km.
The revolution of the Earth around the Sun gives the second basic unit of time - year. In contrast to the daily rotation, the year is not due to the Earth’s revolution around the Sun itself and not even to a change in the distance to it, but to the fact that the Earth’s axis of rotation is inclined to the plane of the orbit
34. Gravitational field of the Earth. Earth's geomagnetic field
Gravity- fundamental interaction in nature, cat. all material bodies are subject. Gravity plays a defining role on the scale of the cosmos
Earth's gravitational field gravity field; force field due to the attraction (gravitation) of the Earth and the centrifugal force caused by its daily rotation. It also depends (slightly) on the attraction of the Moon, the Sun, and other celestial bodies and the masses of the earth's atmosphere. G. p. Z. is characterized by the force of gravity, the potential of gravity and various derivatives of it.
Within the framework of the classic mechanics gr. interaction is described by the law of universal gravitation: the force gr. attraction is equal to prod. masses per square of distances:
F \u003d G ∙ (m 1 ∙m 2) / R 2 G \u003d 6.67 ∙ 10 -11 H ∙ m 2 / kg 2
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 approximately 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 on Earth, the reversal leads to visible movement Suns 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: .
