The earth is moving simultaneously around its axis (diurnal movement) and around the Sun (annual movement). Due to the movement of the Earth around its axis, the cycle of day and night occurs. The globe completes a full revolution around its axis in approximately 24 hours, i.e. per day. The epoch is the main unit of time on our planet. At each meridian, the time of day at one moment is not the same, which is associated with uneven illumination of the globe by the sun's rays. Therefore, time on a particular meridian is defined as solar, or local.

If the country's territory is very long from west to east, local time in different parts of it is not the same. This is inconvenient in practice. Therefore, by international agreement, the Earth was divided into 24 time zones (from zero to 23) and standard time was introduced. The length of each time zone (from west to east) is 15°. Time zone boundaries are sometimes drawn taking into account state borders. The time zone is divided in half by the central meridian. The solar time of the central meridian of each zone is zone time. The local time of the Greenwich (primary) meridian is called universal time.

Time zone map

Consider time zone map.
How many zones is Africa located in? Determine what time is local and standard time in the cities of Buenos Aires and Canberra if it is noon in Kyiv.

If you move from east to west around the globe, then in each subsequent time zone you will have to move the clock hands back one hour. At the end of such a journey (after passing through 24 time zones), it turns out that one day is “lost.”

After completing their round-the-world expedition, Magellan's companions learned that they had returned on Friday. But according to their calculations it should be Thursday. The travelers lost a day as they moved from east to west. Consequently, they made one less revolution around the axis than those who did not go anywhere.

When moving around the world “against the sun,” that is, from west to east, the clock hands in each subsequent time zone are moved forward one hour, and then at the end of such movement one day will be “extra.”

According to international agreement, in order to avoid misunderstandings with the calendar, a date line was drawn along the 180th meridian. (Find it on a map.) It passes through the least populated area on Earth. A new era is counted from this line, which “moves” from east to west. Therefore, when crossing the international date line in this direction, one day is added. For example, instead of May 1, May 2 comes immediately. If you move in the opposite direction, then the same day will have to be counted twice: after December 15, it will be December 15 again.

The change of day and night leads to daily rhythms in nature, that is, the regular repetition of various natural processes during the day. These include regular changes in the illumination of the Earth's surface, in air temperature, in the direction of splashes, etc. Diurnal rhythms are no less clearly manifested in living nature. For example, many flowers open and then close at certain times of the day. Most animal species sleep at night; some, on the contrary, become active at this time. Human life is also subject to circadian rhythms.
The shape of the planet is also related to the rotation of the Earth around its axis. An important consequence of such rotation is the deflection of any bodies on the surface of the Earth moving horizontally - rivers, sea currents, air masses, etc. In the Northern Hemisphere they are deflected to the right, in the Southern Hemisphere - to the left. From the equator to both poles this deviation gradually increases.

Main geographical consequences of the Earth's rotation around its axis:

• The change of day and night and the daily rhythm of natural phenomena;
• Planet shape- flattened at the poles and somewhat expanded at the equator;
• The emergence of natural force, under the influence of which all moving bodies on the surface of the earth are deflected to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere.

The Earth moves around the Sun in an orbit that is shaped like an ellipse. The Earth's axis is inclined to the orbital plane at an angle of 66 ° 33 'which does not change due to movement. Therefore, four characteristic positions of the Earth relative to the Sun appear in the orbit: the summer and winter solstices and the spring and autumn equinoxes.

At the equator, which divides the globe into two hemispheres - Northern and Southern, the angle of incidence of the sun's rays (and the amount of heat) changes little throughout the year. Therefore, there are no seasons known to us: winter, summer, autumn, spring.

Parallels between which the sun at noon can occupy a high, so-called zenital, position, when the angle of incidence of the sun's rays is 90 °, are called tropics. There are Northern and Southern tropics. (Locate them on the map and determine the latitude of each.) On them, the Sun is at its zenith once a year.

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 conventional 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, and the linear speed of rotation is 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 case 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's consider two positions (see figure) that the Earth occupies when moving 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 day length 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 varies 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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Remember

• What is the orbit of a planet? What shape does it have? Which planet is closest to the Sun? What is the Earth's distance from the Sun? Is its movement noticeable to a person?

By human standards, the Earth is huge. It weighs 6,000,000,000,000,000,000,000 tons! Therefore, it is difficult for people living on Earth to believe that such a huge body is in constant motion. The two main types of motion of the Earth, known to mankind since ancient times, are rotation around its axis and around the Sun.

Rice. 15. Rotation of the Earth around its axis

The rotation of the Earth around its axis. The Earth is often compared to a huge top, but, unlike a top, the Earth's axis is an imaginary line. In addition, the earth's axis is inclined to the orbital plane at an angle of 66.5°. The earth's axis is strictly oriented in outer space. Its northern end is directed towards the North Star (Fig. 15).

The points at which the imaginary earth's axis intersects the earth's surface are called geographic poles. There are two such poles - North and South.

All objects on the earth's surface rotate with the Earth. If you observe our planet from space from the North Pole, you can see that it rotates around its axis counterclockwise, that is, from west to east. The Earth completes a full rotation around its axis in about 24 hours. This period is called a day.

Geographical consequences of the Earth's rotation around its axis:

1. The rotation of the Earth affects its shape: it is slightly flattened at the poles.
2. Due to the rotation of the Earth, all bodies moving on its surface are deflected to the right in the direction of their movement in the Northern Hemisphere, and to the left in the Southern Hemisphere.
3. Due to the rotation of the Earth, the cycle of day and night occurs.

If the earth's axis were not strictly oriented in space, the earth would move randomly, "tumbling."

If the Earth stopped rotating around its axis and around the Sun, it would always have one side facing the Sun, on which there would be eternal day. The temperature on this side of the Earth would reach 100°C or more, and all the water would evaporate. The unlit side of the planet would turn into a kingdom of eternal cold, where earthly moisture would accumulate in the form of a giant ice cap.

The movement of the Earth around the Sun. You already know that the Earth moves around the Sun in orbit at a speed of 30 km/s. It is located almost 150 million km away from the Sun (Fig. 16). This distance - huge by human standards and insignificant for space - turned out to be the best for the emergence of life.

Rice. 16. The rotation of the Earth around the Sun

For convenience, the length of the year is considered to be 365 days. The remaining 6 hours are summed up and form an additional day every 4 years. Such years are called leap years; they have 366 days rather than 365. In leap years, the shortest month - February - has not 28, but 29 days.

Scientists' calculations show that throughout the existence of the Earth - 4.6 billion years - the distance between it and the Sun remained practically unchanged.

If the Sun stopped attracting the Earth, it would fly into space 40 times faster than a bullet! If the Earth moved slower in its orbit, it would not be able to resist the gravity of the Sun and would fall towards it.

If the Earth were closer to the Sun, its temperature would be much higher. On Venus, which is 42 million km closer to the Sun, the temperature is about 500°C! If the Earth were further from the Sun, its temperature would be negative. Mars is 228 million km away from the Sun and the temperature on its surface is -60°C. The Earth completes a full revolution around the Sun in 365 days. and 6 hours. This period is called a year.

Questions and tasks

1. Name the two main types of Earth motion.
2. In which direction does the Earth rotate around its axis?
3. Name the consequences of the Earth's rotation around its axis.
4. Name the consequences of the Earth's rotation around the Sun.

Our planet is in constant motion, it rotates around the Sun and its own axis. The Earth's axis is an imaginary line drawn from the North to the South Pole (they remain motionless during rotation) at an angle of 66 0 33 ꞌ relative to the plane of the Earth. People cannot notice the moment of rotation, because all objects move in parallel, their speed is the same. It would look exactly the same as if we were sailing on a ship and did not notice the movement of objects and objects on it.

A full revolution around the axis is completed within one sidereal day, consisting of 23 hours 56 minutes and 4 seconds. During this period, first one or the other side of the planet turns towards the Sun, receiving different amounts of heat and light from it. In addition, the rotation of the Earth around its axis affects its shape (flattened poles are the result of the planet’s rotation around its axis) and the deviation when bodies move in the horizontal plane (rivers, currents and winds of the Southern Hemisphere deviate to the left, of the Northern Hemisphere to the right).

Linear and angular rotation speed

(Earth Rotation)

The linear speed of rotation of the Earth around its axis is 465 m/s or 1674 km/h in the equator zone; as you move away from it, the speed gradually slows down, at the North and South Poles it is zero. For example, for citizens of the equatorial city of Quito (the capital of Ecuador in South America), the rotation speed is exactly 465 m/s, and for Muscovites living at the 55th parallel north of the equator, it is 260 m/s (almost half as much) .

Every year, the speed of rotation around the axis decreases by 4 milliseconds, which is due to the influence of the Moon on the strength of sea and ocean tides. The Moon's gravity "pulls" the water in the opposite direction to the Earth's axial rotation, creating a slight frictional force that slows the rotation speed by 4 milliseconds. The speed of angular rotation remains the same everywhere, its value is 15 degrees per hour.

Why does day give way to night?

(Change of day and night)

The time for a complete revolution of the Earth around its axis is one sidereal day (23 hours 56 minutes 4 seconds), during this time period the side illuminated by the Sun is first “in the power” of the day, the shadow side is under the control of the night, and then vice versa.

If the Earth rotated differently and one side of it was constantly turned towards the Sun, then there would be a high temperature (up to 100 degrees Celsius) and all the water would evaporate; on the other side, on the contrary, frost would rage and the water would be under a thick layer of ice. Both the first and second conditions would be unacceptable for the development of life and the existence of the human species.

Why do the seasons change?

(Change of seasons on Earth)

Due to the fact that the axis is tilted relative to the earth's surface at a certain angle, its parts receive different amounts of heat and light at different times, which causes the change of seasons. According to the astronomical parameters necessary to determine the time of year, certain points in time are taken as reference points: for summer and winter these are the Solstice Days (June 21 and December 22), for spring and autumn - the Equinoxes (March 20 and September 23). From September to March, the Northern Hemisphere faces the Sun for less time and, accordingly, receives less heat and light, hello winter-winter, the Southern Hemisphere receives a lot of heat and light at this time, long live summer! 6 months pass and the Earth moves to the opposite point of its orbit and the Northern Hemisphere receives more heat and light, the days become longer, the Sun rises higher - summer comes.

If the Earth were located in relation to the Sun in an exclusively vertical position, then the seasons would not exist at all, because all points on the half illuminated by the Sun would receive the same and uniform amount of heat and light.

Like other planets of the solar system, it makes 2 main movements: around its own axis and around the Sun. Since ancient times, it was on these two regular movements that calculations of time and the ability to compile calendars were 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 related to 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.) An axis is a virtual straight line crossing the globe in the area of ​​the North and South Poles, i.e. the poles have a fixed position and do not participate in rotational motion, while all other location points 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 Italian region the rotation speed is approximately 1200 km/h. 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 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.

Foucault 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.

Let's imagine that, being at the North Pole, we set a pendulum into oscillatory motion. The external force acting on the pendulum is gravity, but it does not affect the change in the direction of oscillations. If we prepare a virtual pendulum that leaves marks on the surface, we can make sure that after some time the marks will move in a clockwise direction.

This rotation can be associated with two factors: either with the rotation of the plane on which the pendulum makes oscillatory movements, 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 that can change the plane of oscillatory movements. 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. The starting point of the oscillatory movements was recorded 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 record the movement of both the Sun and planets, i.e. All objects in the Universe move.

Time criterion – day

A day is the period 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 of the Earth’s rotation, during which . Another concept - “sidereal day” - implies a different starting point - any star. The duration of the two types of days is not identical. The length of a sidereal day is 23 hours 56 minutes 4 seconds, while the length of a solar day is 24 hours.

The different durations are due to the fact that the Earth, rotating around its own axis, also performs an orbital rotation around the Sun.

In principle, the length of a solar 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, its orbital speed 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 its 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 movement of our planet. The Earth moves in an elliptical orbit, i.e. the orbit has the shape of an ellipse. 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 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 Earth, you get the impression that it is the Sun that moves across the sky throughout the year, passing through the stars and stars that make up the Zodiac. In fact, the Sun also passes through the constellation Ophiuchus, but it does not belong to the Zodiac circle.