The earth rotates or. If the Earth stops, what will happen? The speed of the earth's rotation. North and South Pole. What would happen if the Earth suddenly stopped
Our planet is in constant motion. Together with the Sun, it moves in space around the center of the Galaxy. And that, in turn, moves in the universe. But the most important thing for all living things is the rotation of the Earth around the Sun and its own axis. Without this movement, the conditions on the planet would be unsuitable for sustaining life.
solar system
Earth as a planet of the solar system, according to scientists, was formed more than 4.5 billion years ago. During this time, the distance from the sun practically did not change. The speed of the planet and the gravitational pull of the sun balance its orbit. It is not perfectly round, but stable. If the force of attraction of the star were stronger or the speed of the Earth decreased noticeably, then it would fall on the Sun. Otherwise, sooner or later it would fly into space, ceasing to be part of the system.
The distance from the Sun to the Earth makes it possible to maintain the optimum temperature on its surface. The atmosphere also plays an important role in this. As the Earth rotates around the Sun, the seasons change. Nature has adapted to such cycles. But if our planet were further away, then the temperature on it would become negative. If it were closer, all the water would evaporate, since the thermometer would exceed the boiling point.
The path of a planet around a star is called an orbit. The trajectory of this flight is not perfectly circular. It has an ellipse. The maximum difference is 5 million km. The closest point of the orbit to the Sun is at a distance of 147 km. It's called perihelion. Its land passes in January. In July, the planet is at its maximum distance from the star. The greatest distance is 152 million km. This point is called aphelion.
The rotation of the Earth around its axis and the Sun provides, respectively, a change in daily regimes and annual periods.
For a person, the movement of the planet around the center of the system is imperceptible. This is because the mass of the Earth is enormous. Nevertheless, every second we fly through space about 30 km. It seems unrealistic, but such are the calculations. On average, it is believed that the Earth is located at a distance of about 150 million km from the Sun. It makes one complete revolution around the star in 365 days. The distance traveled in a year is almost a billion kilometers.
The exact distance that our planet travels in a year, moving around the sun, is 942 million km. Together with her, we move in space in an elliptical orbit at a speed of 107,000 km / h. The direction of rotation is from west to east, that is, counterclockwise.
The planet does not complete a complete revolution in exactly 365 days, as is commonly believed. It still takes about six hours. But for the convenience of chronology, this time is taken into account in total for 4 years. As a result, one additional day “runs in”, it is added in February. Such a year is considered a leap year.
The speed of rotation of the Earth around the Sun is not constant. It has deviations from the mean. This is due to the elliptical orbit. The difference between the values is most pronounced at the points of perihelion and aphelion and is 1 km/sec. These changes are imperceptible, since we and all the objects around us move in the same coordinate system.
change of seasons
The rotation of the Earth around the Sun and the tilt of the planet's axis make it possible for the seasons to change. It is less noticeable at the equator. But closer to the poles, the annual cyclicity is more pronounced. The northern and southern hemispheres of the planet are heated by the energy of the Sun unevenly.
Moving around the star, they pass four conditional points of the orbit. At the same time, twice in turn during the semi-annual cycle, they turn out to be further or closer to it (in December and June - the days of the solstices). Accordingly, in a place where the surface of the planet warms up better, the ambient temperature is higher there. The period in such a territory is usually called summer. In the other hemisphere at this time it is noticeably colder - it is winter there.
After three months of such movement, with a frequency of six months, the planetary axis is located in such a way that both hemispheres are in the same conditions for heating. At this time (in March and September - the days of the equinox) the temperature regimes are approximately equal. Then, depending on the hemisphere, autumn and spring come.
earth axis
Our planet is a spinning ball. Its movement is carried out around a conditional axis and occurs according to the principle of a top. Leaning with the base in the plane in the untwisted state, it will maintain balance. When the speed of rotation weakens, the top falls.
The earth has no stop. The forces of attraction of the Sun, the Moon and other objects of the system and the Universe act on the planet. Nevertheless, it maintains a constant position in space. The speed of its rotation, obtained during the formation of the nucleus, is sufficient to maintain relative equilibrium.
The earth's axis passes through the planet's ball is not perpendicular. It is inclined at an angle of 66°33´. The rotation of the Earth on its axis and the Sun makes it possible to change the seasons of the year. The planet would "tumble" in space if it did not have a strict orientation. There would be no question of any constancy of environmental conditions and life processes on its surface.
Axial rotation of the Earth
The rotation of the Earth around the Sun (one revolution) occurs during the year. During the day it alternates between day and night. If you look at the Earth's North Pole from space, you can see how it rotates counterclockwise. It completes a full rotation in about 24 hours. This period is called a day.
The speed of rotation determines the speed of the change of day and night. In one hour, the planet rotates approximately 15 degrees. The speed of rotation at different points on its surface is different. This is due to the fact that it has a spherical shape. At the equator, the linear speed is 1669 km / h, or 464 m / s. Closer to the poles, this figure decreases. At the thirtieth latitude, the linear speed will already be 1445 km / h (400 m / s).
Due to axial rotation, the planet has a slightly compressed shape from the poles. Also, this movement "forces" moving objects (including air and water flows) to deviate from the original direction (Coriolis force). Another important consequence of this rotation is the ebbs and flows.
the change of night and day
A spherical object with the only light source at a certain moment is only half illuminated. In relation to our planet in one part of it at this moment there will be a day. The unlit part will be hidden from the Sun - there is night. Axial rotation makes it possible to change these periods.
In addition to the light regime, the conditions for heating the surface of the planet with the energy of the luminary change. This cycle is important. The speed of change of light and thermal regimes is carried out relatively quickly. In 24 hours, the surface does not have time to either overheat or cool below the optimum.
The rotation of the Earth around the Sun and its axis with a relatively constant speed is of decisive importance for the animal world. Without the constancy of the orbit, the planet would not have stayed in the zone of optimal heating. Without axial rotation, day and night would last for six months. Neither one nor the other would contribute to the origin and preservation of life.
Uneven rotation
Mankind has become accustomed to the fact that the change of day and night occurs constantly. This served as a kind of standard of time and a symbol of the uniformity of life processes. The period of rotation of the Earth around the Sun to a certain extent is influenced by the ellipse of the orbit and other planets of the system.
Another feature is the change in the length of the day. The axial rotation of the Earth is uneven. There are several main reasons. Seasonal fluctuations associated with the dynamics of the atmosphere and the distribution of precipitation are important. In addition, the tidal wave, directed against the motion of the planet, constantly slows it down. This figure is negligible (for 40 thousand years for 1 second). But over 1 billion years, under the influence of this, the length of the day increased by 7 hours (from 17 to 24).
The consequences of the Earth's rotation around the Sun and its axis are being studied. These studies are of great practical and scientific importance. They are used not only to accurately determine stellar coordinates, but also to identify patterns that can affect human life processes and natural phenomena in hydrometeorology and other fields.
The movement of the planet in orbit is determined by two reasons:
- linear inertia of motion (it tends to rectilinear - tangent)
and the gravitational force of the sun.
It is the force of gravity that will change the direction of movement from rectilinear to circular. And gravitational forces applied to a smaller radius will act
stronger on the planet.
If we consider gravity as a force applied to the center, then this gives a change in the direction of movement to a circular one.
If we consider gravity as the sum of forces applied to the entire mass of the planet,
then this gives both a change in the motion vector to a circular one and a rotation around the axis.
Look at the drawing.
The planet has points closer to the Sun and points more distant.
Point A will be closer to the Sun than point B.
And the attraction of point A will be greater than point B. Recall that the force of gravity depends on the squared radius.
When the planet moves clockwise, the gravitational force through point A will pull the planet more than through point B. This difference in forces, gravity applied to diametrically opposite points of the planet, while moving, creates rotation.
Thus, the period of revolution of the planet around its axis directly depends on the equatorial radius of the planet.
With large planets such as Jupiter and Saturn, the difference in the attraction of opposite points is greater and the planet rotates faster.
Table of solar days for planets and equatorial radius:
r
Mercury..... - 175.9421 .... - 0.3825
Venus ..... - 116.7490 .....-0.9488
Earth ...... - 1.0 .... .. - 1.0
M a r s .... - 1.0275 ... ... - 0.5326
Jupiter..... - 0.41358 ... - 11.209
Saturn..... - 0.44403 .... - 9.4491
U r a n ..... - 0.71835 ... - 4.0073
Neptune..... - 0.67126 ... - 3.8826
Pluto..... - 6.38766 .... - 0.1807
The first number is the period of rotation of the planet around its axis in Earth days, the second number is similar - the equatorial radius of the planet. And it can be seen that the largest planet, Jupiter, rotates the fastest, and the smallest, Mercury, the slowest.
In general, the reason for the rotation of the Earth can be explained simply.
When the planet moves in orbit, there is a constant change in the direction of its movement from direct to circular. And at the same time, the planet simultaneously rotates, due to the fact that the points of attraction of the planets located closer to the Sun will pull the planet more strongly than the distant ones.
For example, on Jupiter, where the planet is not a monolith, rotation occurs in layers. The equatorial motion of the layers stands out in particular.
Reviews
Dear Nikolay!
There is no gravity. Newton's and Einstein's laws do not work.
It is impossible to justify the causes of rotation by such methods.
But the topic is interesting.
I hope that by joint efforts, and not on this site, we will solve it.
No. Gravity is everything! But the reasons for its appearance have not yet been established by us.
"Gravity force" - the term conditionally accepted hereinafter, means an external influence on the body. Conditionally in physics it is called "force" the force of gravity.
And the rotation comes from the action of two forces: the inertia of the rectilinear motion and its change to a circular one under the action of the gravitational force, which is perpendicular to the vector of inertia in terms of the vector.
Dear Nikolay!
Dear Nikolay!
In your works there are already calculations, I will not say, justifying the absence of gravity. These works aroused my interest in you, because. it is clear that there is a large statistical material and on it, together and quickly build a science for ourselves, where many things will fall into place. And whether they accept it or not, it should not concern us. Let Volosatov prove it, and we will do it.
I can formulate my position on gravity as follows.
Gravity, as a force of attraction that occurs between two bodies, does not exist.
Exists - an external influence on bodies, the consequence of which is the appearance of a force that causes them to move towards each other. Force leads not to the appearance of another force, but to movement. In this case, the vector of this force is directed along the line connecting these two bodies.
Not attraction, but movement towards.
And not the force arising in the bodies themselves, but the force of external influence.
As the wind blows on the sail.
In general, I understand force as a factor of external influence.
Dear Nikolay!
You, having refuted the forces and their reactions, return to them again.
Yes, these are the "weights" of our teachings. It is difficult to break away from them. I still break away from the remnants of the "institute" teachings. But the physics of the world is completely different. You intuitively felt it. The rest is in personal correspondence.
As a child, I learned that The earth is spinning. My grandfather once told me about a sundial and what its principle is. It's so habitual to watch sunrise and sunset sun, but what happens if The earth will stop?
In which direction does the earth rotate
It all depends on how you look at it. Relatively South Pole, the globe will rotate in the direction clockwise, and quite the opposite for north pole. It is logical that the rotation occurs in the direction of the east - after all, the Sun appears from the east and disappears in the west. Scientists have found that the planet is gradually slows down thousandths of a second per year. Most of the planets in our system have the same direction of rotation, the only exceptions are Uranus and Venus. If you look at the Earth from space, you can notice two types of movement: around its axis, and around the star - the Sun.
Few people noticed whirlpool water in the bathroom. This phenomenon, despite its routine, is a rather big mystery for the scientific world. Indeed, in northern hemisphere whirlpool directed counterclock-wise, and vice versa. Most scientists consider it a manifestation of power Coriolis(inertia caused by rotation Earth). Some other manifestations of this force can be cited in favor of this theory:
- in northern hemisphere winds of the central part cyclone blow counterclockwise, in the south - vice versa;
- the left rail of the railway wears out the most in southern hemisphere, while in the opposite - right;
- by the rivers northern hemisphere pronounced right steep bank, in the South - on the contrary.
What if she stops
It is interesting to guess what will happen if our planet stop spinning. For an ordinary person, this would be equivalent to driving cars at a speed of 2000 km/h and then hard braking. I think it is not necessary to explain the consequences of such an event, but it will not be the worst. If you are at this moment equator, the human body will continue to “fly” at a speed of almost 500 meters per second, however, those who are lucky enough to be closer to poles will survive, but not for long. The wind will become so strong that in terms of the strength of its action it will be comparable to the force nuclear bomb explosion, and the friction of the winds will cause fires all over the world.
For billions of years, day after day, the Earth rotates around its axis. This makes sunrises and sunsets commonplace for life on our planet. The Earth has been doing this since it formed 4.6 billion years ago. And it will continue to do so until it ceases to exist. This will probably happen when the Sun turns into a red giant and swallows our planet. But why Earth?
Why does the earth rotate?
The Earth was formed from a disk of gas and dust that revolved around the newborn Sun. Thanks to this spatial disk, particles of dust and rock were folded together to form the Earth. As the Earth grew, space rocks continued to collide with the planet. And they had an impact on it that made our planet rotate. And because all the debris in the early solar system revolved around the sun in roughly the same direction, the collisions that made the earth (and most of the rest of the solar system's bodies) spin round the sun in that same direction.
Gas and dust disk
A reasonable question arises - why did the gas and dust disk itself rotate? The sun and the solar system were formed at the moment when a cloud of dust and gas began to condense under the influence of its own weight. Most of the gas came together to become the Sun, and the remaining material created the planetary disk surrounding it. Before it took shape, gas molecules and dust particles moved within its boundaries evenly in all directions. But at some point, randomly, some gas and dust molecules folded their energy in the same direction. This set the direction of rotation of the disc. As the gas cloud began to contract, its rotation accelerated. The same process occurs when skaters start to spin faster if they press their hands to the body.
In space, there are not many factors capable of planetary rotation. Therefore, as soon as they begin to rotate, this process does not stop. The rotating young solar system has a large angular momentum. This characteristic describes the tendency of an object to continue rotating. It can be assumed that all exoplanets probably also begin to rotate in the same direction around their stars when their planetary system is formed.
And we're doing the opposite!
Interestingly, in the solar system, some planets have a direction of rotation opposite to the movement around the sun. Venus rotates in the opposite direction relative to the Earth. And the axis of rotation of Uranus is tilted 90 degrees. Scientists do not fully understand the processes that caused these planets to get such directions of rotation. But they have some guesses. Venus may have received such a rotation as a result of a collision with another cosmic body at an early stage of its formation. Or perhaps Venus began to rotate in the same way as other planets. But over time, the Sun's gravity began to slow down its rotation due to its dense clouds. Which, combined with the friction between the planet's core and its mantle, caused the planet to rotate in the opposite direction.
In the case of Uranus, scientists have suggested that there was a collision of the planet with a huge rocky fragment. Or perhaps with several different objects that changed the axis of his rotation.
Despite such anomalies, it is clear that all objects in space rotate in one direction or another.
Everything is spinning
Asteroids are spinning. The stars are turning. According to NASA, galaxies also rotate. It takes the solar system 230 million years to complete one revolution around the center of the Milky Way. Some of the fastest rotating objects in the universe are dense, round objects called pulsars. They are the remnants of massive stars. Some city-sized pulsars can rotate around their axis hundreds of times per second. The fastest and most famous of them, discovered in 2006 and called Terzan 5ad, rotates 716 times per second.
Black holes can do this even faster. It is assumed that one of them, named GRS 1915 + 105, can rotate at a speed of 920 to 1150 times per second.
However, the laws of physics are inexorable. All rotations eventually slow down. When , it rotated around its axis at a rate of one revolution every four days. Today, our star takes about 25 days to complete one revolution. Scientists believe that the reason for this is that the Sun's magnetic field interacts with the solar wind. This is what slows it down.
The Earth's rotation is also slowing down. The moon's gravity acts on the earth in such a way that it slowly slows down its rotation. Scientists have calculated that the Earth's rotation has slowed by a total of about 6 hours over the past 2,740 years. This is only 1.78 milliseconds over a century.
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Our planet is constantly in motion:
- rotation around its own axis, movement around the Sun;
- rotation together with the Sun around the center of our galaxy;
- motion relative to the center of the Local Group of galaxies and others.
Earth's motion around its own axis
Rotation of the Earth around its axis(Fig. 1). An imaginary line is taken for the earth's axis, around which it rotates. This axis is deviated by 23 ° 27 "from the perpendicular to the plane of the ecliptic. The earth's axis intersects with the earth's surface at two points - the poles - North and South. When viewed from the North Pole, the Earth's rotation occurs counterclockwise or, as is commonly believed, with west to east.The planet makes a complete rotation around its axis in one day.
Rice. 1. Rotation of the Earth around its axis
A day is a unit of time. Separate sidereal and solar days.
sidereal day is the amount of time it takes the earth to rotate on its axis with respect to the stars. They are equal to 23 hours 56 minutes 4 seconds.
solar day is the amount of time it takes for the earth to rotate on its axis with respect to the sun.
The angle of rotation of our planet around its axis is the same at all latitudes. In one hour, each point on the surface of the Earth moves 15° from its original position. But at the same time, the speed of movement is inversely proportional to the geographical latitude: at the equator it is 464 m / s, and at a latitude of 65 ° - only 195 m / s.
The rotation of the Earth around its axis in 1851 was proved by J. Foucault in his experiment. In Paris, in the Pantheon, a pendulum was hung under the dome, and under it a circle with divisions. With each subsequent movement, the pendulum turned out to be on new divisions. This can only happen if the surface of the Earth under the pendulum rotates. The position of the swing plane of the pendulum at the equator does not change, because the plane coincides with the meridian. The axial rotation of the Earth has important geographic implications.
When the Earth rotates, a centrifugal force arises, which plays an important role in shaping the shape of the planet and reduces the force of gravity.
Another of the most important consequences of axial rotation is the formation of a turning force - Coriolis forces. In the 19th century it was first calculated by a French scientist in the field of mechanics G. Coriolis (1792-1843). This is one of the inertial forces introduced to take into account the influence of the rotation of a moving frame of reference on the relative motion of a material point. Its effect can be briefly expressed as follows: every moving body in the Northern Hemisphere deviates to the right, and in the Southern - to the left. At the equator, the Coriolis force is zero (Fig. 3).
Rice. 3. Action of the Coriolis force
The action of the Coriolis force extends to many phenomena of the geographic envelope. Its deflecting effect is especially noticeable in the direction of movement of air masses. Under the influence of the deflecting force of the Earth's rotation, the winds of temperate latitudes of both hemispheres take a predominantly westerly direction, and in tropical latitudes - east. A similar manifestation of the Coriolis force is found in the direction of movement of ocean waters. The asymmetry of river valleys is also associated with this force (the right bank is usually high in the Northern Hemisphere, in the Southern - the left).
The rotation of the Earth around its axis also leads to the movement of solar illumination over the earth's surface from east to west, i.e., to the change of day and night.
The change of day and night creates a daily rhythm in animate and inanimate nature. The daily rhythm is closely related to light and temperature conditions. The daily course of temperature, day and night breezes, etc. are well known. Daily rhythms also occur in wildlife - photosynthesis is possible only during the day, most plants open their flowers at different hours; Some animals are active during the day, others at night. Human life also proceeds in a daily rhythm.
Another consequence of the rotation of the Earth around its axis is the difference in time at different points on our planet.
Since 1884, a zone time account was adopted, that is, the entire surface of the Earth was divided into 24 time zones of 15 ° each. Per standard time take the local time of the middle meridian of each zone. Neighboring time zones differ by one hour. The boundaries of the belts are drawn taking into account political, administrative and economic boundaries.
The zero belt is Greenwich (by the name of the Greenwich Observatory near London), which runs on both sides of the prime meridian. The time of the zero, or initial, meridian is considered World time.
Meridian 180° accepted as international date measurement line- a conditional line on the surface of the globe, on both sides of which hours and minutes coincide, and calendar dates differ by one day.
For a more rational use of daylight in summer in 1930, our country introduced maternity time, ahead of the zone by one hour. To do this, the hands of the clock were moved forward one hour. In this regard, Moscow, being in the second time zone, lives according to the time of the third time zone.
Since 1981, between April and October, the time has been moved forward one hour. This so-called summer time. It is introduced to save energy. In summer, Moscow is two hours ahead of standard time.
The time zone in which Moscow is located is Moscow.
Movement of the Earth around the Sun
Rotating around its axis, the Earth simultaneously moves around the Sun, going around the circle in 365 days 5 hours 48 minutes 46 seconds. This period is called astronomical year. For convenience, it is considered that there are 365 days in a year, and every four years, when 24 hours out of six hours “accumulate”, there are not 365, but 366 days in a year. This year is called leap year, and one day is added to February.
The path in space along which the Earth moves around the Sun is called orbit(Fig. 4). The Earth's orbit is elliptical, so the distance from the Earth to the Sun is not constant. When the earth is in perihelion(from Greek. peri- near, around and helios- Sun) - the closest point of the orbit to the Sun - on January 3, the distance is 147 million km. It is winter in the Northern Hemisphere at this time. The farthest distance from the Sun in aphelion(from Greek. aro- away from and helios- Sun) - the greatest distance from the Sun - July 5. It is equal to 152 million km. At this time, it is summer in the Northern Hemisphere.
Rice. 4. Movement of the Earth around the Sun
The annual movement of the Earth around the Sun is observed by the continuous change in the position of the Sun in the sky - the midday height of the Sun and the position of its sunrise and sunset change, the duration of the bright and dark parts of the day changes.
When moving in orbit, the direction of the earth's axis does not change, it is always directed towards the North Star.
As a result of a change in the distance from the Earth to the Sun, as well as due to the inclination of the Earth's axis to the plane of its movement around the Sun, an uneven distribution of solar radiation is observed on Earth during the year. This is how the seasons change, which is typical for all planets that have an inclination of the axis of rotation to the plane of its orbit. (ecliptic) different from 90°. The orbital speed of the planet in the Northern Hemisphere is higher in winter and lower in summer. Therefore, the winter half-year lasts 179, and the summer half-year - 186 days.
As a result of the movement of the Earth around the Sun and the inclination of the earth's axis to the plane of its orbit by 66.5 °, not only the change of seasons is observed on our planet, but also a change in the length of day and night.
The rotation of the Earth around the Sun and the change of seasons on Earth are shown in Fig. 81 (equinoxes and solstices according to the seasons in the Northern Hemisphere).
Only twice a year - on the days of the equinox, the length of day and night on the whole Earth is almost the same.
Equinox- the moment at which the center of the Sun, during its apparent annual movement along the ecliptic, crosses the celestial equator. There are spring and autumn equinoxes.
The inclination of the Earth's axis of rotation around the Sun on the equinoxes of March 20-21 and September 22-23 is neutral with respect to the Sun, and the parts of the planet facing it are uniformly illuminated from pole to pole (Fig. 5). The sun's rays fall vertically at the equator.
The longest day and shortest night occur on the summer solstice.
Rice. 5. Illumination of the Earth by the Sun on the days of the equinox
Solstice- the moment of passage by the center of the Sun of the points of the ecliptic, the most distant from the equator (solstice points). There are summer and winter solstices.
On the day of the summer solstice on June 21-22, the Earth takes a position in which the northern end of its axis is tilted towards the Sun. And the rays fall vertically not on the equator, but on the northern tropic, whose latitude is 23 ° 27 "All day and night, not only the polar regions are illuminated, but also the space beyond them up to latitude 66 ° 33" (Arctic Circle). In the Southern Hemisphere at this time, only that part of it that lies between the equator and the southern Arctic Circle (66 ° 33 ") turns out to be illuminated. Beyond it, on this day, the earth's surface is not illuminated.
On the day of the winter solstice on December 21-22, everything happens the other way around (Fig. 6). The sun's rays are already falling sheer on the southern tropic. Lighted in the Southern Hemisphere are areas that lie not only between the equator and the tropic, but also around the South Pole. This situation continues until the spring equinox.
Rice. 6. Illumination of the Earth on the day of the winter solstice
At two parallels of the Earth on the days of the solstice, the Sun at noon is directly above the head of the observer, that is, at the zenith. Such parallels are called tropics. On the Tropic of the North (23° N), the Sun is at its zenith on June 22, on the Tropic of the South (23° S) on December 22.
At the equator, day is always equal to night. The angle of incidence of the sun's rays on the earth's surface and the length of the day there change little, so the change of seasons is not expressed.
arctic circles remarkable in that they are the boundaries of areas where there are polar days and nights.
polar day- the period when the sun does not fall below the horizon. The farther from the Arctic Circle near the pole, the longer the polar day. At the latitude of the Arctic Circle (66.5°) it lasts only one day, and at the Pole it lasts 189 days. In the Northern Hemisphere at the latitude of the Arctic Circle, the polar day is observed on June 22 - the day of the summer solstice, and in the Southern Hemisphere at the latitude of the Southern Arctic Circle - on December 22.
polar night lasts from one day at the latitude of the Arctic Circle to 176 days at the poles. During the polar night, the Sun does not appear above the horizon. In the Northern Hemisphere, at the latitude of the Arctic Circle, this phenomenon is observed on December 22.
It is impossible not to note such a wonderful natural phenomenon as white nights. White Nights- these are bright nights at the beginning of summer, when the evening dawn converges with the morning dawn and twilight lasts all night. They are observed in both hemispheres at latitudes exceeding 60°, when the center of the Sun at midnight falls below the horizon by no more than 7°. In St. Petersburg (about 60°N) white nights last from June 11 to July 2, in Arkhangelsk (64°N) from May 13 to July 30.
The seasonal rhythm in connection with the annual movement primarily affects the illumination of the earth's surface. Depending on the change in the height of the Sun above the horizon on Earth, there are five lighting belts. The hot belt lies between the Northern and Southern tropics (the Tropic of Cancer and the Tropic of Capricorn), occupies 40% of the earth's surface and is distinguished by the largest amount of heat coming from the Sun. Between the tropics and the Arctic Circles in the Southern and Northern Hemispheres there are moderate zones of illumination. The seasons of the year are already expressed here: the farther from the tropics, the shorter and cooler the summer, the longer and colder the winter. The polar belts in the Northern and Southern Hemispheres are limited by the Arctic Circles. Here, the height of the Sun above the horizon during the year is low, so the amount of solar heat is minimal. The polar zones are characterized by polar days and nights.
Depending on the annual movement of the Earth around the Sun, there are not only the change of seasons and the associated uneven illumination of the earth's surface across latitudes, but also a significant part of the processes in the geographical envelope: seasonal weather changes, the regime of rivers and lakes, the rhythm in the life of plants and animals, types and terms of agricultural work.
Calendar.Calendar- a system for calculating long periods of time. This system is based on periodic natural phenomena associated with the movement of celestial bodies. The calendar uses astronomical phenomena - the change of seasons, day and night, the change in the lunar phases. The first calendar was Egyptian, created in the 4th century. BC e. On January 1, 45, Julius Caesar introduced the Julian calendar, which is still used by the Russian Orthodox Church. Due to the fact that the duration of the Julian year is longer than the astronomical one by 11 minutes 14 seconds, by the 16th century. an “error” of 10 days accumulated - the day of the vernal equinox did not come on March 21, but on March 11. This mistake was corrected in 1582 by a decree of Pope Gregory XIII. The count of days was moved forward by 10 days, and the day after October 4 was prescribed to be considered Friday, but not October 5, but October 15. The spring equinox was again returned to March 21, and the calendar became known as the Gregorian. It was introduced in Russia in 1918. However, it also has a number of drawbacks: unequal duration of months (28, 29, 30, 31 days), inequality of quarters (90, 91, 92 days), inconsistency of numbers of months by days of the week.
