Moon- the only celestial body that orbits the Earth, not counting artificial Earth satellites created by man over the past last years.
The moon continuously moves across the starry sky and, in relation to any star, per day moves towards the daily rotation of the sky by approximately 13°, and after 27.1/3 days it returns to the same stars, having described a full circle in the celestial sphere. Therefore, the period of time during which the Moon makes a complete revolution around the Earth in relation to the stars is called sidereal (or sidereal)) month; it is 27.1/3 days. The Moon moves around the Earth in an elliptical orbit, so the distance from the Earth to the Moon changes by almost 50 thousand km. The average distance from the Earth to the Moon is taken to be 384,386 km (rounded - 400,000 km). This is ten times the length of the Earth's equator.
Moon It itself does not emit light, so only its surface, the daylight side, illuminated by the Sun, is visible in the sky. Night time, dark, not visible. Moving across the sky from west to east, in 1 hour the Moon shifts against the background of stars by about half a degree, i.e., by an amount close to its apparent size, and in 24 hours - by 13º. FOR a month, the Moon in the sky catches up and overtakes the Sun, and a change occurs lunar phases: new moon , first quarter , full moon And last quarter .
IN new moon The moon cannot be seen even with a telescope. It is located in the same direction as the Sun (only above or below it), and is turned towards the Earth by the night hemisphere. Two days later, when the Moon moves away from the Sun, a narrow crescent can be seen a few minutes before its sunset in the western sky against the background of the evening dawn. The first appearance of the crescent moon after the new moon was called “neomenia” by the Greeks (“ new Moon"), From this moment the lunar month begins.
7 days 10 hours after the new moon, a phase called first quarter. During this time, the Moon moved away from the Sun by 90º. From Earth, only the right half of the lunar disk, illuminated by the Sun, is visible. After sunset Moon is in the southern sky and sets around midnight. Continuing to move from the Sun more and more to the left. Moon in the evening it appears already on the eastern side of the sky. She comes in after midnight, every day later and later.
When Moon appears in the direction opposite to the Sun (at an angular distance of 180 from it), comes full moon. 14 days and 18 hours have passed since the new moon. After that Moon begins to approach the Sun from the right.
There is a decrease in illumination of the right part of the lunar disk. The angular distance between it and the Sun decreases from 180 to 90º. Again, only half of the lunar disk is visible, but its left part. 22 days 3 hours have passed since the new moon. last quarter. The moon rises around midnight and shines throughout the second half of the night, ending up in the southern sky by sunrise.
The width of the lunar crescent continues to decrease, and Moon gradually approaches the Sun from the right (western) side. Appearing in the eastern sky, every day later, the lunar crescent becomes very narrow, but its horns are turned to the right and look like the letter “C”.
They say, Moon old An ashen light is visible on the night part of the disk. The angular distance between the Moon and the Sun decreases to 0º. Finally, Moon catches up with the Sun and becomes invisible again. The next new moon is coming. The lunar month has ended. 29 days 12 hours 44 minutes 2.8 seconds passed, or almost 29.53 days. This period is called synodic month (from the Greek sy "nodos-connection, rapprochement).
The synodic period is associated with the visible position of the celestial body relative to the Sun in the sky. Lunar a synodic month is the period of time between successive phases of the same name Moons.
Your path in the sky relative to the stars Moon completes 7 hours 43 minutes 11.5 seconds in 27 days (rounded - 27.32 days). This period is called sidereal (from Latin sideris - star), or sidereal month .
No. 7 Eclipse of the Moon and the Sun, their analysis.
Solar and lunar eclipses - most interesting phenomenon nature, familiar to man since ancient times. They occur relatively often, but are not visible from all areas earth's surface and therefore seem rare to many.
Solar eclipse occurs when our natural satellite - the Moon - in its movement passes against the background of the Sun's disk. This always happens at the time of the new moon. The Moon is located closer to the Earth than the Sun, almost 400 times, and at the same time its diameter is also approximately 400 times smaller than the diameter of the Sun. Therefore, the apparent sizes of the Earth and the Sun are almost the same, and the Moon can cover the Sun. But not every new moon there is a solar eclipse. Due to the tilt of the Moon's orbit relative to Earth's orbit, the Moon usually "misses" slightly and passes above or below the Sun at the time of the new moon. However, at least 2 times a year (but no more than five) the shadow of the Moon falls on the Earth and a solar eclipse occurs.
The lunar shadow and penumbra fall on the Earth in the form of oval spots, which travel at a speed of 1 km. per second run across the earth's surface from west to east. In areas that are in the lunar shadow, a total solar eclipse is visible, that is, the Sun is completely obscured by the Moon. In areas covered by penumbra, a partial solar eclipse occurs, that is, the Moon covers only part of the solar disk. Beyond the penumbra, no eclipse occurs at all.
Longest duration full phase eclipses do not exceed 7 minutes. 31 sec. But most often it is two to three minutes.
A solar eclipse starts from the right edge of the Sun. When the Moon completely covers the Sun, twilight sets in, as in dark twilight, and the most bright stars and planets, and around the Sun a beautiful pearl-colored radiant glow is visible - the solar corona, which is the outer layers of the solar atmosphere, not visible outside of an eclipse due to their low brightness compared to the brightness of the daytime sky. The appearance of the corona changes from year to year depending on solar activity. A pink glow ring flashes above the entire horizon - this is the area covered with the moon's shadow, sunlight penetrates from neighboring zones where total eclipse does not happen, but only the particular is observed.
SOLAR AND LUNAR ECLIPSE
The Sun, Moon and Earth in the new moon and full moon stages rarely lie on the same line, because The lunar orbit does not lie exactly in the plane of the ecliptic, but at an inclination of 5 degrees to it.
Solar eclipses new moon. The Moon blocks the Sun from us.
Lunar eclipses. The Sun, Moon and Earth lie on the same line in the stage full moon. The Earth blocks the Moon from the Sun. The moon turns brick red.
Every year there are on average 4 solar and lunar eclipses. They always accompany each other. For example, if the new moon coincides with a solar eclipse, then the lunar eclipse occurs two weeks later, in the full moon phase.
Astronomically, solar eclipses occur when the Moon, as it moves around the Sun, completely or partially obscures the Sun. The apparent diameters of the Sun and the Moon are almost the same, so the Moon completely obscures the Sun. But this is visible from the Earth in the full phase band. A partial solar eclipse is observed on both sides of the total phase band.
The width of the band of the total phase of a solar eclipse and its duration depend on the mutual distances of the Sun, Earth and Moon. As a result of changes in distances, the apparent angular diameter of the Moon also changes. When it is slightly larger than the solar eclipse, a total eclipse can last up to 7.5 minutes; when it is equal, then one instant; if it is smaller, then the Moon does not completely cover the Sun. In the latter case, an annular eclipse occurs: a narrow bright solar ring is visible around the dark lunar disk.
During a total solar eclipse, the Sun appears as a black disk surrounded by a radiance (corona). Daylight is so weak that you can sometimes see stars in the sky.
A total lunar eclipse occurs when the Moon enters the Earth's shadow.
A total lunar eclipse can last 1.5-2 hours. It can be observed from all over the night hemisphere of the Earth, where the Moon was above the horizon at the time of the eclipse. Therefore, in this area, total lunar eclipses can be observed much more often than solar eclipses.
During a total lunar eclipse of the Moon, the lunar disk remains visible, but takes on a dark red hue.
A solar eclipse occurs on a new moon, and a lunar eclipse occurs on a full moon. Most often there are two lunar and two solar eclipses in a year. The maximum possible number of eclipses is seven. After a certain period of time, lunar and solar eclipses are repeated in the same order. This interval was called saros, which translated from Egyptian means repetition. Saros is approximately 18 years, 11 days. During each Saros there are 70 eclipses, of which 42 are solar and 28 are lunar. Total solar eclipses from a certain area are observed less frequently than lunar eclipses, once every 200-300 years.
CONDITIONS FOR A SUN ECLIPSE
During a solar eclipse, the Moon passes between us and the Sun and hides it from us. Let us consider in more detail the conditions under which a solar eclipse can occur.
Our planet Earth, rotating around its axis during the day, simultaneously moves around the Sun and makes a full revolution in a year. The Earth has a satellite - the Moon. The Moon moves around the Earth and completes a full revolution in 29 1/2 days.
The relative position of these three celestial bodies changes all the time. During its movement around the Earth, the Moon at certain periods of time finds itself between the Earth and the Sun. But the Moon is a dark, opaque solid ball. Finding itself between the Earth and the Sun, it, like a huge curtain, covers the Sun. At this time, the side of the Moon that faces the Earth turns out to be dark and unlit. Therefore, a solar eclipse can only occur during a new moon. During a full moon, the Moon passes away from the Earth in the direction opposite to the Sun and may fall into the shadow cast by the globe. Then we will observe a lunar eclipse.
The average distance from the Earth to the Sun is 149.5 million km, and the average distance from the Earth to the Moon is 384 thousand km.
The closer an object is, the larger it seems to us. The Moon, compared to the Sun, is almost 400 times closer to us, and at the same time its diameter is also approximately 400 times less than the diameter of the Sun. Therefore, the apparent sizes of the Moon and the Sun are almost the same. The Moon can thus block the Sun from us.
However, the distances of the Sun and Moon from the Earth do not remain constant, but change slightly. This happens because the path of the Earth around the Sun and the path of the Moon around the Earth are not circles, but ellipses. As the distances between these bodies change, their apparent sizes also change.
If at the moment of a solar eclipse the Moon is at its smallest distance from the Earth, then the lunar disk will be slightly larger than the solar one. The Moon will completely cover the Sun, and the eclipse will be total. If during an eclipse the Moon is in greatest distance from the Earth, then it will have slightly smaller apparent dimensions and will not be able to cover the Sun entirely. The light rim of the Sun will remain uncovered, which during an eclipse will be visible as a bright thin ring around the black disk of the Moon. This type of eclipse is called an annular eclipse.
It would seem that solar eclipses should occur monthly, every new moon. However, this does not happen. If the Earth and the Moon moved in a visible plane, then at every new moon the Moon would actually be exactly in a straight line connecting the Earth and the Sun, and an eclipse would occur. In fact, the Earth moves around the Sun in one plane, and the Moon around the Earth in another. These planes do not coincide. Therefore, often during new moons the Moon comes either higher than the Sun or lower.
The apparent path of the Moon in the sky does not coincide with the path along which the Sun moves. These paths intersect at two opposite points, which are called the nodes of the lunar orbit. Near these points, the paths of the Sun and Moon come close to each other. And only when the new moon occurs near a node is it accompanied by an eclipse.
The eclipse will be total or annular if the Sun and Moon are almost at a node at the new moon. If the Sun at the moment of the new moon is at some distance from the node, then the centers of the lunar and solar disks will not coincide and the Moon will only partially cover the Sun. Such an eclipse is called a partial eclipse.
The moon moves among the stars from west to east. Therefore, the covering of the Sun by the Moon begins from its western, i.e., right, edge. The degree of closure is called the eclipse phase by astronomers.
Around the spot of the lunar shadow there is a penumbral region, here a partial eclipse occurs. The diameter of the penumbra region is about 6-7 thousand km. For an observer located near the edge of this region, only a small fraction of the solar disk will be covered by the Moon. Such an eclipse may go unnoticed altogether.
Is it possible to accurately predict the occurrence of an eclipse? Scientists in ancient times established that after 6585 days and 8 hours, which is 18 years 11 days 8 hours, eclipses are repeated. This happens because it is after such a period of time that the location in space of the Moon, Earth and Sun is repeated. This interval was called saros, which means repetition.
During one Saros there are on average 43 solar eclipses, of which 15 are partial, 15 are annular and 13 are total. By adding 18 years, 11 days and 8 hours to the dates of eclipses observed during one saros, we can predict the occurrence of eclipses in the future.
In the same place on Earth, a total solar eclipse is observed once every 250 - 300 years.
Astronomers have calculated the visibility conditions for solar eclipses many years in advance.
LUNAR ECLIPSE
Lunar eclipses are also among the “extraordinary” celestial phenomena. This is how they happen. The full light circle of the Moon begins to darken at its left edge, a round brown shadow appears on the lunar disk, it moves further and further and after about an hour covers the entire Moon. The moon fades and turns red-brown.
The diameter of the Earth is almost 4 times larger than the diameter of the Moon, and the shadow from the Earth, even at the distance of the Moon from the Earth, is more than 2 1/2 times the size of the Moon. Therefore, the Moon can be completely immersed in the Earth's shadow. A total lunar eclipse is much longer than a solar eclipse: it can last 1 hour and 40 minutes.
For the same reason that solar eclipses do not occur every new moon, lunar eclipses do not occur every full moon. Largest number there are 3 lunar eclipses per year, but there are years without any eclipses at all; This was the case, for example, in 1951.
Lunar eclipses recur after the same period of time as solar eclipses. During this interval, in 18 years 11 days 8 hours (saros), there are 28 lunar eclipses, of which 15 are partial and 13 are total. As you can see, the number of lunar eclipses in Saros is significantly less than solar eclipses, and yet lunar eclipses can be observed more often than solar ones. This is explained by the fact that the Moon, plunging into the shadow of the Earth, ceases to be visible on the entire half of the Earth not illuminated by the Sun. This means that each lunar eclipse is visible significantly larger territory than any solar one.
The eclipsed Moon does not disappear completely, like the Sun during a solar eclipse, but is faintly visible. This happens because some of the sun's rays come through the earth's atmosphere, are refracted in it, enter the earth's shadow and hit the moon. Since the red rays of the spectrum are least scattered and weakened in the atmosphere. During an eclipse, the moon takes on a copper-red or brown hue.
CONCLUSION
It is difficult to imagine that solar eclipses occur so often: after all, each of us has to observe eclipses extremely rarely. This is explained by the fact that during a solar eclipse the shadow from the Moon does not fall on the entire Earth. The fallen shadow has the shape of almost round spot, the diameter of which can reach at most 270 km. This spot will cover only a negligible fraction of the earth's surface. IN this moment Only on this part of the Earth will a total solar eclipse be visible.
The moon moves in its orbit at a speed of about 1 km/sec, i.e. faster than a gun bullet. Consequently, its shadow moves at high speed along the earth's surface and cannot cover any one place on the globe for a long time. Therefore, a total solar eclipse can never last more than 8 minutes.
Thus, the lunar shadow, moving across the Earth, describes a narrow but long strip, in which a total solar eclipse is successively observed. The length of the total solar eclipse reaches several thousand kilometers. And yet the area covered by the shadow turns out to be insignificant compared to the entire surface of the Earth. In addition, oceans, deserts and sparsely populated areas of the Earth are often in the zone of total eclipse.
The sequence of eclipses repeats itself almost exactly in the same order over a period of time called a saros (saros is the Egyptian word meaning “repetition”). Saros, known in ancient times, is 18 years and 11.3 days. Indeed, eclipses will be repeated in the same order (after any initial eclipse) after as much time as is necessary for the same phase of the Moon to occur at the same distance of the Moon from the node of its orbit as during the initial eclipse.
During each Saros there are 70 eclipses, of which 41 are solar and 29 are lunar. Thus, solar eclipses occur more often than lunar eclipses, but at a given point on the Earth’s surface, lunar eclipses can be observed more often, since they are visible over the entire hemisphere of the Earth, while solar eclipses are visible only in a relatively narrow band. It is especially rare to see total solar eclipses, although there are about 10 of them during each Saros.
No. 8 The Earth is like a ball, an ellipsoid of revolution, a 3-axis ellipsoid, a geoid.
Assumptions about the spherical shape of the earth appeared in the 6th century BC, and from the 4th century BC some of the evidence known to us was expressed that the Earth is spherical in shape (Pythagoras, Eratosthenes). Ancient scientists proved the sphericity of the Earth based on the following phenomena:
- circular view of the horizon in open spaces, plains, seas, etc.;
- the circular shadow of the Earth on the surface of the Moon during lunar eclipses;
- change in the height of stars when moving from north (N) to south (S) and back, due to the convexity of the noon line, etc. In his essay “On the Heavens,” Aristotle (384 – 322 BC) indicated that The earth is not only spherical in shape, but also has finite dimensions; Archimedes (287 - 212 BC) proved that the surface of water in calm state is a spherical surface. They also introduced the concept of the Earth's spheroid as a geometric figure close in shape to a ball.
Modern theory The study of the figure of the Earth originates from Newton (1643 - 1727), who discovered the law universal gravity and used it to study the figure of the Earth.
By the end of the 80s of the 17th century, the laws of planetary motion around the Sun were known, the very precise dimensions of the globe determined by Picard from degree measurements (1670), the fact that the acceleration of gravity on the Earth's surface decreases from north (N) to south (S ), Galileo's laws of mechanics and Huygens' research on the motion of bodies along curvilinear trajectory. A generalization of these phenomena and facts led scientists to a well-founded view about the spheroidality of the Earth, i.e. its deformation in the direction of the poles (flatness).
Newton's famous work, “Mathematical Principles of Natural Philosophy” (1867), sets out a new doctrine about the figure of the Earth. Newton came to the conclusion that the figure of the Earth should be shaped like an ellipsoid of rotation with slight polar compression (this fact was justified by him by decreasing the length of the second pendulum with decreasing latitude and decreasing gravity from pole to equator due to the fact that “Earth slightly higher at the equator").
Based on the hypothesis that the Earth consists of a homogeneous mass of density, Newton theoretically determined the polar compression of the Earth (α) in a first approximation to be approximately 1: 230. In fact, the Earth is heterogeneous: the crust has a density of 2.6 g/cm3, while average density Earth is 5.52 g/cm3. The uneven distribution of the Earth's masses produces extensive gentle convexities and concavities, which combine to form hills, depressions, depressions and other shapes. Note that individual elevations above the Earth reach heights of more than 8000 meters above the ocean surface. It is known that the surface of the World Ocean (MO) occupies 71%, land – 29%; the average depth of the World Ocean is 3800 m, and the average height of land is 875 m. The total area of the earth's surface is 510 x 106 km2. From the given data it follows, most of The Earth is covered with water, which gives grounds to take it as a level surface (LS) and, ultimately, as the general figure of the Earth. The figure of the Earth can be represented by imagining a surface at each point of which the force of gravity is directed normal to it (along a plumb line).
The complex figure of the Earth, limited by a level surface, which is the beginning of the report of heights, is usually called a geoid. Otherwise, the surface of the geoid, as an equipotential surface, is fixed by the surface of oceans and seas that are in a calm state. Under continents, the geoid surface is defined as the surface perpendicular to power lines(Figure 3-1).
P.S. The name of the Earth's figure - geoid - was proposed by the German physicist I.B. Listig (1808 – 1882). When mapping the earth's surface, based on many years of research by scientists, the complex geoid figure, without compromising accuracy, is replaced by a mathematically simpler one - ellipsoid of revolution. Ellipsoid of revolution– a geometric body formed as a result of rotation of an ellipse around a minor axis.
The ellipsoid of rotation comes close to the geoid body (the deviation does not exceed 150 meters in some places). The dimensions of the earth's ellipsoid were determined by many scientists around the world.
Basic Research figures of the Earth made by Russian scientists F.N. Krasovsky and A.A. Izotov, made it possible to develop the idea of a triaxial earth ellipsoid, taking into account large geoid waves, as a result of which its main parameters were obtained.
In recent years (late 20th and early 21st centuries), the parameters of the Earth’s figure and external gravitational potential have been determined using space objects and the use of astronomical, geodetic and gravimetric research methods so reliably that now we are talking about assessing their measurements in time.
The triaxial terrestrial ellipsoid, which characterizes the figure of the Earth, is divided into a general terrestrial ellipsoid (planetary), suitable for solving global problems of cartography and geodesy, and a reference ellipsoid, which is used in individual regions, countries of the world and their parts. An ellipsoid of revolution (spheroid) is a surface of revolution in three-dimensional space, formed by rotating an ellipse around one of its main axes. An ellipsoid of revolution is a geometric body formed as a result of the rotation of an ellipse around a minor axis.
Geoid- the figure of the Earth, limited by the level surface of the gravity potential, which coincides in the oceans with the average ocean level and is extended under the continents (continents and islands) so that this surface is everywhere perpendicular to the direction of gravity. The surface of the geoid is smoother than the physical surface of the Earth.
The shape of the geoid does not have an exact mathematical expression, and to construct cartographic projections, the correct geometric figure is selected, which differs little from the geoid. The best approximation of the geoid is the figure obtained by rotating an ellipse around a short axis (ellipsoid)
The term "geoid" was coined in 1873 by the German mathematician Johann Benedict Listing to refer to geometric figure, more accurately than an ellipsoid of revolution, reflecting the unique shape of planet Earth.
An extremely complex figure is the geoid. It exists only theoretically, but in practice it cannot be touched or seen. You can imagine the geoid as a surface, the force of gravity at each point of which is directed strictly vertically. If our planet were a regular sphere filled evenly with some substance, then the plumb line at any point would point to the center of the sphere. But the situation is complicated by the fact that the density of our planet is heterogeneous. In some places there are heavy rocks, in others, voids, mountains and depressions are scattered across the entire surface, and plains and seas are also unevenly distributed. All this changes the gravitational potential at each specific point. The fact that the shape of the globe is a geoid is also to blame for the ethereal wind that blows our planet from the north.
We can say that at first glance, the Moon simply moves around planet Earth at a certain speed and in a certain orbit.
In reality, this is a very complex process of movement of a cosmic body, difficult to describe from a scientific point of view, occurring under the influence of many different factors. Such, for example, as the shape of the Earth, if we remember from school curriculum, it is slightly flattened, and it is also very strongly influenced by the fact that, for example, the Sun attracts it 2.2 times stronger than our home planet.
Images from the Deep Impact spacecraft sequence of the Moon's movement
At the same time producing accurate calculations movement, it is also necessary to take into account that through tidal interaction the Earth transfers angular momentum to the Moon, thereby creating a force that forces it to move away from itself. At the same time, the gravitational interaction of these cosmic bodies is not constant and with increasing distance it decreases, leading to a decrease in the speed of the Moon’s retreat. The rotation of the Moon around the Earth relative to the stars is called a sidereal month and is equal to 27.32166 days.
Why is she glowing?
Have you ever wondered why sometimes we only see part of the Moon? Or why does it glow? Let's figure it out! The satellite reflects only 7% of the sunlight falling on it. This happens because during periods of intense solar activity, only certain parts of its surface are able to absorb and accumulate solar energy, and then weakly emit it.
Ash Light - Reflected Light from the Earth
By itself, it cannot glow, but can only reflect the light of the Sun. Therefore, we see only that part of it that was previously illuminated by the Sun. This satellite moves in a certain orbit around our planet and the angle between it, the Sun and the Earth is constantly changing, as a result we see different phases of the Moon.
Moon phases infographic
The time between new moons is 28.5 days. The fact that one month is longer than the other can be explained by the movement of the Earth around the Sun, that is, when the satellite makes a full revolution around the Earth, the planet itself at that moment moves 1/13 around its orbit. And for the Moon to be between the Sun and the Earth again, it needs about two more days of time.
Despite the fact that it constantly rotates around its axis, it always looks at the Earth with the same side, which means that the rotation it makes around its own axis and around the planet itself is synchronous. This synchronicity is caused by the tides.
back side
back side
Our satellite rotates uniformly around its own axis, and around the Earth according to a certain law, the essence of which is as follows: this movement is uneven - near the perigee it is faster, but near the apogee it is a little slower.
Sometimes it is possible to look at the far side of the Moon if you are in the east or, for example, in the west. This phenomenon is called optical libration in longitude; there is also optical libration in latitude. It arises due to the tilt of the lunar axis relative to the Earth, and this can be observed in the south and north.
The orbit of the Moon is the trajectory along which the Moon rotates around a common center of mass with the Earth, located approximately 4700 km from the center of the Earth. Each revolution takes 27.3 Earth days and is called a sidereal month.
The Moon is the natural satellite of the Earth and the closest celestial body to it.
Rice. 1. Orbit of the Moon 
Rice. 2. Sidereal and synodic months
It revolves around the Earth in an elliptical orbit in the same direction as the Earth around the Sun. The average distance of the Moon from the Earth is 384,400 km. The plane of the Moon’s orbit is inclined to the plane of the ecliptic by 5.09’ (Fig. 1).
The points where the Moon's orbit intersects the ecliptic are called the nodes of the lunar orbit. The movement of the Moon around the Earth appears to the observer as its visible movement across the celestial sphere. The apparent path of the Moon across the celestial sphere is called the apparent orbit of the Moon. During the day, the Moon moves in its visible orbit relative to the stars by approximately 13.2°, and relative to the Sun by 12.2°, since the Sun also moves along the ecliptic by an average of 1° during this time. The period of time during which the Moon makes a full revolution in its orbit relative to the stars is called a sidereal month. Its duration is 27.32 average solar days.
The period of time during which the Moon makes a full revolution in its orbit relative to the Sun is called the synodic month.
It is equal to 29.53 average solar days. The sidereal and synodic months differ by approximately two days due to the movement of the Earth in its orbit around the Sun. In Fig. Figure 2 shows that when the Earth is in orbit at point 1, the Moon and the Sun are observed on the celestial sphere in the same place, for example, against the background of the star K. After 27.32 days, i.e., when the Moon makes a full revolution around the Earth, it will again be observed against the background of the same star. But since the Earth, together with the Moon, will move in its orbit relative to the Sun by approximately 27° during this time and will be at point 2, the Moon still needs to travel 27° to take its previous position relative to the Earth and the Sun, which will take about 2 days . Thus, the synodic month is longer than the sidereal month by the length of time that the Moon needs to move 27°.
The period of rotation of the Moon around its axis is equal to the period of its revolution around the Earth. Therefore, the Moon always faces the Earth with the same side. Due to the fact that in one day the Moon moves across the celestial sphere from west to east, i.e., in the direction opposite to the daily movement of the celestial sphere, by 13.2°, its rising and setting are delayed by approximately 50 minutes every day. This daily delay causes the Moon to continuously change its position relative to the Sun, but after a strictly defined period of time it returns to its original position. As a result of the movement of the Moon along its visible orbit, there is a continuous and rapid change in its equatorial
coordinates On average, per day the Moon's right ascension changes by 13.2°, and its declination by 4°. The change in the equatorial coordinates of the Moon occurs not only due to its rapid movement in orbit around the Earth, but also due to the extraordinary complexity of this movement. The Moon is subject to many forces of varying magnitude and period, under the influence of which all elements of the lunar orbit are constantly changing.
The inclination of the Moon's orbit to the ecliptic ranges from 4°59' to 5°19' over a period of slightly less than six months. The shapes and sizes of the orbit change. The position of the orbit in space changes continuously with a period of 18.6 years, as a result of which the nodes of the lunar orbit move towards the movement of the Moon. This leads to a constant change in the angle of inclination of the visible orbit of the Moon to the celestial equator from 28°35’ to 18°17’. Therefore, the limits of change in the declination of the Moon do not remain constant. In some periods it varies within ±28°35', and in others - ±18°17'.
The declination of the Moon and its Greenwich hour angle are given in the daily MAE tables for each hour of Greenwich time.
The movement of the Moon on the celestial sphere is accompanied by a continuous change in its appearance. The so-called change of lunar phases occurs. The phase of the Moon is the visible part of the lunar surface illuminated by the sun's rays.
Let's consider what causes the lunar phases to change. It is known that the Moon shines by reflected sunlight. Half of its surface is always illuminated by the Sun. But due to the different relative positions of the Sun, Moon and Earth, the illuminated surface appears to the earthly observer in different types(Fig. 3).
It is customary to distinguish between four phases of the moon: new moon, first quarter, full moon and last quarter.
During the new moon, the Moon passes between the Sun and the Earth. In this phase, the Moon faces the Earth with its unlit side, and therefore it is not visible to an observer on Earth. In the first quarter phase, the Moon is in such a position that the observer sees it as half an illuminated disk. During a full moon, the Moon is in the opposite direction to the Sun. Therefore, the entire illuminated side of the Moon faces the Earth and is visible as a full disk. 
Rice. 3. Positions and phases of the Moon:
1 - new moon; 2 - first quarter; 3 - full moon; 4 - last quarter
After the full moon, the illuminated part of the Moon visible from the Earth gradually decreases. When the Moon reaches its last quarter phase, it is again visible as a half-lit disk. In the Northern Hemisphere, in the first quarter, the right half of the Moon’s disk is illuminated, and in the last quarter, the left half is illuminated.
In the interval between the new moon and the first quarter and in the interval between the last quarter and the new moon, it is facing the Earth small part illuminated Moon, which is observed in the form of a crescent. In the intervals between the first quarter and the full moon, the full moon and the last quarter, the Moon is visible in the form of a damaged disk. The full cycle of changing lunar phases occurs within a strictly defined period of time. It is called the phase period. It is equal to the synodic month, i.e. 29.53 days.
The time interval between the main phases of the Moon is approximately 7 days. The number of days that have passed since the new moon is usually called the age of the moon. As age changes, the moonrise and moonset points also change. The dates and moments of the onset of the main phases of the Moon according to Greenwich time are given in MAE.
The movement of the Moon around the Earth causes lunar and solar eclipses. Eclipses occur only when the Sun and Moon are simultaneously located near the nodes of the lunar orbit. A solar eclipse occurs when the Moon is between the Sun and the Earth, i.e. during the new moon, and a lunar eclipse occurs when the Earth is between the Sun and the Moon, i.e. during the full moon.
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The Earth's natural satellite is the Moon, a non-luminous body that reflects sunlight.
The study of the Moon began in 1959, when the Soviet Luna-2 spacecraft first landed on the Moon, and the Luna-3 spacecraft first took pictures from space. reverse side Moons.
In 1966, Luna 9 landed on the Moon and established a solid soil structure.
The first people to walk on the moon were Americans Neil Armstrong and Edwin Aldrin. This happened on July 21, 1969. Soviet scientists for further study of the Moon preferred to use automatic vehicles - lunar rovers.
General characteristics of the Moon
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The mass of the Moon is 1/81 of the mass of the Earth. The position of the Moon in orbit corresponds to one or another phase (Fig. 1).
Rice. 1. Moon phases
Moon phases- various positions relative to the Sun - new moon, first quarter, full moon and last quarter. During a full moon, the illuminated disk of the Moon is visible, since the Sun and Moon are on opposite sides from the Earth. During the new moon, the Moon is on the side of the Sun, so the side of the Moon facing the Earth is not illuminated.
The Moon always faces the Earth with one side.
The line that separates the illuminated part of the Moon from the unlit part is called terminator.
In the first quarter, the Moon is visible at an angular distance of 90" from the Sun, and Sun rays They illuminate only the right half of the Moon facing us. In other phases, the Moon is visible to us in the form of a crescent. Therefore, in order to distinguish the growing Moon from the old one, one must remember: the old Moon resembles the letter “C”, and if the Moon is growing, then you can mentally draw a vertical line in front of the Moon and you will get the letter “P”.
Due to the proximity of the Moon to the Earth and its large mass, they form the Earth-Moon system. The Moon and Earth rotate around their axes in the same direction. The plane of the Moon's orbit is inclined to the plane of the Earth's orbit at an angle of 5°9".
The intersection of the orbits of the Earth and the Moon is called nodes of the lunar orbit.
Sidereal(from Latin sideris - star) month is the period of rotation of the Earth around its axis and the same position of the Moon on the celestial sphere in relation to the stars. It is 27.3 Earth days.
Synodic(from the Greek synod - connection) a month is the period of complete change of lunar phases, i.e. the period of the Moon returning to its original position relative to the Moon and the Sun (for example, from new moon to new moon). It averages 29.5 Earth days. The synodic month is two days longer than the sidereal month, since the Earth and Moon rotate around their axes in the same direction.
The gravity on the Moon is 6 times less strength gravity on Earth.
The relief of the Earth's satellite is well studied. The visible dark areas on the surface of the Moon are called “seas” - these are vast waterless lowland plains (the largest is “Oksan Bur”), and the light areas are called “continents” - these are mountainous, elevated areas. The main planetary structures of the lunar surface are ring craters with a diameter of up to 20-30 km and multi-ring circuses with a diameter of 200 to 1000 km.
The origin of ring structures is different: meteorite, volcanic and shock-explosive. In addition, there are cracks, shifts, domes and fault systems on the surface of the Moon.
Studies by the Luna-16, Luna-20, and Luna-24 spacecraft have shown that the surface clastic rocks of the Moon are similar to terrestrial igneous rocks - basalts.
The meaning of the Moon in the life of the Earth
Although the mass of the Moon is 27 million times less than the mass of the Sun, it is 374 times closer to the Earth and has a strong influence on the planet, causing rising tides in some places and low tides in others. This happens every 12 hours 25 minutes, since the Moon makes a full revolution around the Earth in 24 hours 50 minutes.
Due to the gravitational influence of the Moon and the Sun on the Earth, ebb and flow(Fig. 2).
Rice. 2. Scheme of the occurrence of ebbs and flows on Earth
The most distinct and important in their consequences are tidal phenomena in the wave shell. They represent periodic rises and falls in the level of oceans and seas, caused by the gravitational forces of the Moon and the Sun (2.2 times less than the lunar one).
In the atmosphere, tidal phenomena manifest themselves in semidiurnal changes in atmospheric pressure, and in earth's crust- in deformation solid Earth.
On Earth, there are 2 high tides at the point closest and farthest from the Moon and 2 low tides at points located at an angular distance of 90° from the Moon-Earth line. Highlight cygisian tides, which occur on new and full moons and quadrature- in the first and last quarter.
In the open ocean, tidal movements are small. Water level fluctuations reach 0.5-1 m. In the inland seas (Black, Baltic, etc.) they are almost not felt. However, depending on geographical latitude and the outlines of the coastline of the continents (especially in narrow bays), water during high tides can rise up to 18 m (Bay of Fundy in the Atlantic Ocean off the coast of North America), 13 m on west coast Sea of Okhotsk. In this case, tidal currents are formed.
The main significance of tidal waves is that, moving from east to west following visible movement Moons, they slow down the axial rotation of the Earth and lengthen the day, change the figure of the Earth by reducing polar compression, cause pulsation of the Earth's shells, vertical displacements of the Earth's surface, semi-diurnal changes in atmospheric pressure, change the conditions of organic life in the coastal parts of the World Ocean and, finally, influence economic activities of coastal countries. Sea vessels can only enter a number of ports at high tide.
After a certain period of time on Earth they repeat solar and lunar eclipses. They can be seen when the Sun, Earth and Moon are on the same line.
Eclipse- an astronomical situation in which one celestial body blocks the light from another celestial body.
A solar eclipse occurs when the Moon comes between the observer and the Sun and blocks it. Since the Moon before an eclipse faces us with its unlit side, there is always a new moon before an eclipse, i.e. the Moon is not visible. It seems that the Sun is covered by a black disk; an observer from Earth sees this phenomenon as a solar eclipse (Fig. 3).
Rice. 3. Solar eclipse (the relative sizes of bodies and the distances between them are relative)
A lunar eclipse occurs when the Moon, while aligned with the Sun and Earth, falls into the cone-shaped shadow cast by the Earth. The diameter of the Earth's shadow spot is equal to the minimum distance of the Moon from the Earth - 363,000 km, which is about 2.5 times the diameter of the Moon, so the Moon can be completely obscured (see Fig. 3).
Lunar rhythms are repeated changes in the intensity and nature of biological processes. There are lunar-monthly (29.4 days) and lunar-diurnal (24.8 hours) rhythms. Many animals and plants reproduce at a certain phase of the lunar cycle. Lunar rhythms are characteristic of many marine animals and plants of the coastal zone. Thus, people have noticed changes in their well-being depending on the phases of the lunar cycle.
