The exact time of the earth's revolution around the sun. How fast is the earth spinning
Our star through filters
The rotation of the Sun depends on where the observer measures it from, interested? Spots on the equator take about 24.47 Earth days to make a complete revolution around.
Astronomers call this the sidereal rotation period, which differs from the synodic period by the amount of time it takes for the sunspots to rotate around the Sun as viewed from Earth.
The rate of rotation decreases as you get closer to the poles, so that at the poles the period of rotation around the axis can be up to 38 days.
rotation observations
The movement of the Sun is clearly visible if you observe its spots. All spots move on the surface. This movement is part of the general movement of the star around its axis.
Observations show that it does not rotate as a rigid body, but differentially.
This means that it moves faster at the equator and slower at the poles. The gas giants Jupiter and Saturn also have differential rotation.
Astronomers have measured the rotational speed of the sun from a latitude of 26° from the equator, and found that it takes 25.38 days to complete one rotation around its axis. Its axis makes an angle equal to 7 degrees and 15 minutes.
The inner regions and core rotate together as a rigid body. And the outer layers convective zone and the photosphere rotate at different speeds.
The revolution of the sun around the center of the galaxy
Our luminary and we, together with it, revolve around the center of the galaxy. Milky Way. The average speed is 828,000 km/h. One revolution takes about 230 million years. The Milky Way is a spiral galaxy. It is believed that it consists of a central core, 4 main arms with several short segments.
It took man many millennia to understand that the Earth is not the center of the universe and is in constant motion.
The phrase of Galileo Galilei "And yet it spins!" forever went down in history and became a kind of symbol of the era when scientists from different countries tried to refute the theory of the geocentric system of the world.
Although the rotation of the Earth was proven about five centuries ago, the exact reasons that prompt it to move are still unknown.
Why does the earth spin on its axis?
In the Middle Ages, people believed that the Earth was stationary, and the Sun and other planets revolved around it. Only in the 16th century did astronomers manage to prove the opposite. Despite the fact that many associate this discovery with Galileo, in fact it belongs to another scientist - Nicolaus Copernicus.
It was he who in 1543 wrote the treatise "On the Revolution of the Celestial Spheres", where he put forward a theory about the motion of the Earth. For a long time this idea did not receive support either from his colleagues or from the church, but in the end it had a huge impact on scientific revolution in Europe and became the foundation of further development astronomy. 
After the theory of the rotation of the Earth was proven, scientists began to look for the causes of this phenomenon. Over the past centuries, many hypotheses have been put forward, but even today no astronomer can accurately answer this question.
Currently, there are three main versions that have the right to life - theories about inertial rotation, magnetic fields and the impact of solar radiation on the planet.
Theory of inertial rotation
Some scientists are inclined to believe that once (during the time of its appearance and formation) the Earth spun, and now it rotates by inertia. Formed from cosmic dust, it began to attract other bodies to itself, which gave it an additional impulse. This assumption also applies to other planets in the solar system.
The theory has many opponents, since it cannot explain why in different time the speed of the Earth's movement either increases or decreases. It is also unclear why some planets in the solar system rotate in the opposite direction, such as Venus.
Theory about magnetic fields
If you try to connect two magnets with the same charged pole together, they will start to repel each other. The theory of magnetic fields suggests that the poles of the Earth are also charged in the same way and, as it were, repel each other, which causes the planet to rotate. 
Interestingly, scientists recently made a discovery that the Earth's magnetic field pushes its inner core from west to east and causes it to rotate faster than the rest of the planet.
Sun exposure hypothesis
The most probable is considered to be the theory of solar radiation. It is well known that it warms up the surface shells of the Earth (air, seas, oceans), but heating occurs unevenly, resulting in the formation of sea and air currents.
It is they who, when interacting with the solid shell of the planet, make it rotate. A kind of turbines that determine the speed and direction of movement are the continents. If they are not monolithic enough, they begin to drift, which affects the increase or decrease in speed.
Why does the earth move around the sun?
The reason for the revolution of the Earth around the Sun is called inertia. According to the theory about the formation of our star, about 4.57 billion years ago, a huge amount of dust arose in space, which gradually turned into a disk, and then into the Sun.
The outer particles of this dust began to combine with each other, forming planets. Even then, by inertia, they began to rotate around the star and continue to move along the same trajectory today. 
According to Newton's law, all cosmic bodies move in a straight line, that is, in fact, the planets of the solar system, including the Earth, should have long flown into outer space. But that doesn't happen.
The reason is that the Sun has a large mass and, accordingly, great power attraction. The Earth, during its movement, is constantly trying to rush away from it in a straight line, but gravitational forces pull it back, so the planet is kept in orbit and revolves around the Sun.
Movement around the axis of rotation is one of the most common types of movement of objects in nature. In this article, we will consider this type of movement from the point of view of dynamics and kinematics. We also give formulas relating the main physical quantities.
What movement are we talking about?
In the literal sense, we will talk about moving bodies around a circle, that is, about their rotation. A prime example such movement is the rotation of the wheel of a car or bicycle while the vehicle is moving. Rotation around its axis of a figure skater performing complex pirouettes on ice. Or the rotation of our planet around the Sun and around its own axis inclined to the plane of the ecliptic.
As you can see, an important element of the type of movement under consideration is the axis of rotation. Each point of an arbitrary-shaped body makes circular motions around it. The distance from the point to the axis is called the radius of rotation. Many properties of the entire mechanical system depend on its value, for example, the moment of inertia, linear velocity, and others.
If the reason for the linear translational movement of bodies in space is the force acting on them external force, then the cause of motion around the axis of rotation is the external moment of force. This value is described as vector product applied force F¯ by the distance vector from the point of its application to the axis r¯, that is:
The action of the moment M¯ leads to the appearance of an angular acceleration α¯ in the system. Both quantities are related to each other through a certain coefficient I by the following equality:
The quantity I is called the moment of inertia. It depends both on the shape of the body and on the distribution of mass inside it and on the distance to the axis of rotation. For a material point, it is calculated by the formula:
If the external is zero, then the system retains its angular momentum L¯. This is another vector quantity, which, according to the definition, is equal to:
Here p¯ is the linear momentum.
The momentum conservation law L¯ is usually written in the following form:
Where ω is the angular velocity. It will be discussed further in the article.
Kinematics of rotation
Unlike dynamics, this branch of physics considers exclusively practical important quantities associated with the change in time of the position of bodies in space. That is, the objects of study of the kinematics of rotation are velocities, accelerations and angles of rotation.
First, let's introduce the angular velocity. It is understood as the angle through which the body makes a turn per unit of time. The formula for the instantaneous angular velocity is:
If the body rotates through equal angles in equal intervals of time, then the rotation is called uniform. For him, the formula for the average angular velocity is valid:
ω is measured in radians per second, which in the SI system corresponds to reciprocal seconds (s -1).
In the case of non-uniform rotation, the concept of angular acceleration α is used. It determines the rate of change in time of the value ω, that is:
α \u003d dω / dt \u003d d 2 θ / dt 2
α is measured in radians per square second (in SI - s -2).
If the body initially rotated uniformly at a speed ω 0, and then began to increase its speed with a constant acceleration α, then such a movement can be described by the following formula:
θ = ω 0 *t + α*t 2 /2
This equality is obtained by integrating the angular velocity equations with respect to time. The formula for θ allows you to calculate the number of revolutions that the system will make around the axis of rotation in time t.
Linear and angular speeds
Both speeds are related to each other. When talking about the speed of rotation around an axis, they can mean both linear and angular characteristics.
Suppose that some material point rotates around an axis at a distance r with a speed ω. Then its linear speed v will be equal to:
The difference between linear and angular speed is significant. Thus, ω does not depend on the distance to the axis during uniform rotation, while the value of v increases linearly with increasing r. Last fact explains why with an increase in the radius of rotation it is more difficult to keep the body on a circular trajectory (its linear velocity and, as a result, inertial forces increase).
The task of calculating the speed of rotation around its axis of the Earth
Everyone knows that our planet is in solar system performs two types of rotational movement:
- around its axis;
- around the star.
Let us calculate the speeds ω and v for the first of them.
The angular velocity is not difficult to determine. To do this, remember that the planet makes a complete revolution equal to 2 * pi radians in 24 hours ( exact value 23 h 56 min. 4.1 sec.). Then the value of ω will be equal to:
ω \u003d 2 * pi / (24 * 3600) \u003d 7.27 * 10 -5 rad / s
The calculated value is small. Let us now show how much the absolute value of ω differs from that of v.
Let us calculate the linear velocity v for points lying on the surface of the planet at the latitude of the equator. Since the Earth is an oblate ball, the equatorial radius is slightly larger than the polar one. It is 6378 km. Using the formula for the connection of two velocities, we obtain:
v \u003d ω * r \u003d 7.27 * 10 -5 * 6378000 ≈ 464 m / s
The resulting speed is 1670 km/h, which is greater than the speed of sound in air (1235 km/h).
The rotation of the Earth around its axis leads to the appearance of the so-called Coriolis force, which should be taken into account when flying ballistic missiles. It is also the cause of many atmospheric phenomena, such as the deviation of the direction of the trade winds to the west.
Since ancient times, mankind has known two main types of Earth motion - rotation around its axis and around the Sun.
Turns around its own axis
It is established that the Earth rotates around its axis counterclockwise, that is, from west to east. The Earth makes a complete revolution around its axis in 23 hours 56 minutes and 4.091 seconds. This period is called a sidereal day. The axis around which the Earth rotates is imaginary. It is inclined to the plane of its orbit by 23.5°. This angle does not change during the motion of the Earth. The northern end of the imaginary axis is always directed towards the North Star.
Rotating, the Earth substitutes to the Sun either one side or the other. On the side of the Earth illuminated by the Sun, it is day, and on the opposite side, it is night. Thus, the change in day and night is a consequence of the rotation of the Earth around its axis.
Tellurium is a device that visually shows the annual movement of the Earth around the Sun and the daily rotation of the Earth around its axis.
The intersection points of the imaginary earth's axis with the earth's surface are called geographic poles. There are two such poles - North and South. At the same distance from the poles, an imaginary circle is drawn on the surface of the globe - the equator. To the north of the equator is the Northern Hemisphere of the Earth, to the south - the Southern.
Since the Earth's axis of rotation is inclined by 23.5° relative to the plane of the ecliptic, in the regions close to the poles the Sun almost does not set in summer, and the polar day lasts for several months. In winter, the Sun hardly rises, and the polar night lasts for several months.
Why is there a leap year
The Earth makes a complete revolution around the Sun in 365 days and 6 hours, that is, in a year. For convenience, it is considered that there are exactly 365 days in a year, and every four years, when another 24 hours are “collected” from the remaining time, one more day is added to the year and it becomes 366 days. Such a year is called a leap year, and a day is added in February - and instead of the usual 28, it has 29 days.
Solstices and equinoxes
The change of day and night occurs on Earth continuously. But twice a year on the days of the spring and autumn equinoxes - March 21 and September 23 - their duration is the same in all parts of the globe.
The longest day and shortest night occurs on the day of the summer solstice, which in the Northern Hemisphere falls on June 21-22. At this time, the earth's axis is tilted by the northern end to the Sun. The northern hemisphere receives more heat than the southern, and therefore in the first of them - summer, in the second - winter. And on December 21-22, on the contrary, the southern end of the earth's axis is inclined to the Sun. IN southern hemisphere at this time summer, and in the North - winter. This is the winter solstice, the shortest day in the Northern Hemisphere.
The average distance from the Earth to the Sun is approximately 150 million kilometers. But since rotation of the earth around the sun occurs not in a circle, but in an ellipse, then at different times of the year the Earth is either a little further from the Sun, or a little closer to it.
In this real time-lapse photo, we see the path the Earth makes in 20-30 minutes relative to other planets and galaxies, rotating around its axis.
Change of seasons
It is known that in summer, in the hottest time of the year - in June, the Earth is about 5 million kilometers farther from the Sun than in winter, in the coldest season - in December. Hence, change of seasons happens not because the Earth is further or closer to the Sun, but for another reason.
The Earth, in its translational motion around the Sun, constantly maintains the same direction of its axis. And with the translational rotation of the Earth around the Sun in orbit, this imaginary earth's axis is always inclined to the plane of the earth's orbit. The reason for the change of seasons is precisely the fact that the Earth's axis is always inclined to the plane of the Earth's orbit in the same way.
Therefore, on June 22, when our hemisphere has the longest day of the year, the Sun also illuminates the North Pole, and the South Pole remains in darkness, since the sun's rays do not illuminate it. While summer in the Northern Hemisphere has long days and short nights, in the Southern Hemisphere, on the contrary, there are long nights and short days. There, therefore, it is winter, where the rays fall "obliquely" and have a low calorific value.
Time difference between day and night
It is known that the change of day and night occurs as a result of the rotation of the Earth around its axis, (more details:). A time difference between day and night depends on the rotation of the earth around the sun. In winter, December 22, when the longest night and the shortest day begin in the Northern Hemisphere, the North Pole is not illuminated by the Sun at all, it is “in darkness”, and the South Pole is illuminated. In winter, as you know, the inhabitants of the Northern Hemisphere have long nights and short days.
On March 21–22, the day is equal to the night, the vernal equinox; the same equinox autumn- happens on September 23rd. These days, the Earth occupies such a position in its orbit relative to the Sun that the sun's rays simultaneously illuminate both the North and South Poles, and they fall vertically on the equator (the Sun is at its zenith). Therefore, on March 21 and September 23, any point on the surface of the globe is illuminated by the Sun for 12 hours and is in darkness for 12 hours: day and night all over the world.
Climatic zones of the Earth
The rotation of the Earth around the Sun explains the existence of various climatic zones Earth. Due to the fact that the Earth has a spherical shape and its imaginary axis is always inclined to the plane of the earth's orbit at the same angle, different parts of the earth's surface are heated and illuminated by the sun's rays in different ways. They fall on separate areas of the earth's surface at different angles of inclination, and as a result, their calorific value in different zones of the earth's surface is not the same. When the Sun is low above the horizon (for example, in the evening) and its rays fall on the earth's surface under high angle they heat very little. On the contrary, when the Sun is high above the horizon (for example, at noon), its rays fall on the Earth at a large angle, and their calorific value increases.
Where the Sun is at its zenith on some days and its rays fall almost vertically, there is the so-called hot belt. In these places, animals have adapted to the hot climate (for example, monkeys, elephants and giraffes); tall palm trees, bananas grow there, pineapples ripen; there, under the shadow of the tropical Sun, spreading their crown widely, there are gigantic baobab trees, the thickness of which in girth reaches 20 meters.
Where the sun never rises high above the horizon, there are two cold zones with poor flora and fauna. Here the animal and plant world is monotonous; large areas are almost devoid of vegetation. Snow covers boundless expanses. Between the hot and cold zones are two temperate belts, which occupy the largest areas of the surface of the globe.
The rotation of the Earth around the Sun explains the existence five climatic zones: one hot, two moderate and two cold.
The hot belt is located near the equator, and its conditional boundaries are the northern tropic (the tropic of Cancer) and the southern tropic (the tropic of Capricorn). The conditional boundaries of the cold belts are the northern and southern polar circles. Polar nights last there for almost 6 months. Days are the same length. There is no sharp boundary between the thermal zones, but there is a gradual decrease in heat from the equator to the South and North Poles.
Around the North and South Poles, huge spaces are occupied by continuous ice fields. In the oceans washing these inhospitable shores, colossal icebergs float (more:).
North and South Pole explorers
Reach North or South Pole has long been a daring dream of man. Brave and tireless Arctic explorers have made these attempts more than once.
So was the Russian explorer Georgy Yakovlevich Sedov, who in 1912 organized an expedition to the North Pole on the ship St. Foca. The tsarist government was indifferent to this great undertaking and did not provide adequate support to the brave sailor and experienced traveler. Due to lack of funds, G. Sedov was forced to spend the first winter on Novaya Zemlya, and the second on. In 1914, Sedov, together with two companions, finally made the last attempt to reach the North Pole, but the state of health and strength changed this daring man, and in March of that year he died on the way to his goal.
More than once, large expeditions on ships to the Pole were equipped, but even these expeditions failed to reach their goal. heavy ice"fettered" ships, sometimes broke them and carried them away with their drift far in the direction opposite to the intended path.
Only in 1937, for the first time, was a Soviet expedition delivered by airships to the North Pole. The brave four - astronomer E. Fedorov, hydrobiologist P. Shirshov, radio operator E. Krenkel and the old sailor, expedition leader I. Papanin - lived on a drifting ice floe for 9 months. The huge ice floe sometimes gave cracks and collapsed. Brave explorers were more than once in danger of dying in the waves of the cold Arctic sea, but, despite this, they produced their own Scientific research where no human foot has ever set foot. Important research has been carried out in the fields of gravimetry, meteorology and hydrobiology. The fact of the existence of five climatic zones associated with the rotation of the Earth around the Sun has been confirmed.
