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 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 lunar orbit. The movement of the Moon around the Earth appears to the observer as its apparent movement along celestial sphere. Visible path The moon along the celestial sphere is called the visible 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 full turn 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 the Moon moves across the celestial sphere from west to east in one day, i.e. in the opposite direction daily movement celestial sphere, by 13.2°, its sunrise and sunset are delayed by approximately 50 minutes every day. This daily delay leads to the fact that the Moon continuously changes its position relative to the Sun, but after a strictly defined period of time it returns to initial position. As a result of the movement of the Moon along its visible orbit, continuous and rapid change 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 fast 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. It leads to constant change inclination angle visible orbit 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. There is a so-called change lunar phases. The phase of the moon is called the visible part 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 reflected sunlight. Half of its surface is always illuminated by the Sun. But due to various mutual provisions The illuminated surface of the Sun, Moon and Earth 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 direction opposite direction in 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, a small part of the illuminated Moon faces the Earth, 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. Full cycle Changes in lunar phases occur 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. Solar eclipse occurs when the Moon is between the Sun and the Earth, i.e. during the new moon, and lunar - when the Earth is between the Sun and the Moon, i.e. during the full moon.
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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, it is very complex and difficult to describe. scientific point view of the process of movement of a cosmic body, occurring under the influence of many various 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.
Pictures spacecraft Deep Impact moon movement sequence
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. Wherein gravitational interaction data 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% sunlight falling on her. This happens because during the period of rapid activity of the Sun, only certain areas of its surface are able to absorb and accumulate solar energy, and then weakly radiate 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 faces the Earth with the same side, which means that the rotation it makes around own axis and around the planet itself synchronously. 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 moon accompanies our planet in its great space travel for several billion years now. And she shows us, earthlings, from century to century always the same lunar landscape. Why do we admire only one side of our companion? Does the Moon rotate around its axis or does it float in outer space still?
Characteristics of our cosmic neighbor
IN solar system there are much more satellites larger than the moon. Ganymede is a satellite of Jupiter, for example, twice as heavy as the Moon. But she is the most large satellite relative to the mother planet. Its mass is more than a percent of the Earth's, and its diameter is about a quarter of the Earth's. There are no such proportions in the solar family of planets anymore.
Let's try to answer the question of whether the Moon rotates on its axis by taking a closer look at our closest cosmic neighbor. According to the theory accepted today in scientific circles, natural satellite our planet acquired while still a protoplanet - not completely cooled, covered with an ocean of liquid hot lava, as a result of a collision with another planet, smaller in size. That's why chemical compositions lunar and terrestrial soils are slightly different - the heavy cores of the colliding planets merged, which is why earth rocks richer in iron. Luna got the leftovers upper layers both protoplanets, there is more rock there.
Does the Moon Rotate?
To be precise, the question of whether the Moon rotates is not entirely correct. After all, like any satellite in our system, it turns around the mother planet and spins around the star with it. But the Moon is not quite usual.
No matter how much you look at the Moon, it is always turned towards us by the crater of Quiet and the Sea of Tranquility. “Does the Moon rotate around its axis?” - earthlings have asked themselves this question from century to century. Strictly speaking, if you operate geometric concepts, the answer depends on the chosen coordinate system. Relative to Earth axial rotation the Moon really does not have it.
But from the point of view of an observer located on the Sun-Earth line, the axial rotation of the Moon will be clearly visible, and one polar revolution will be equal in duration to an orbital revolution up to a fraction of a second.
Interestingly, this phenomenon is not unique in the solar system. Thus, Pluto's satellite Charon always looks at its planet with one side, and the satellites of Mars - Deimos and Phobos - behave in the same way.
On scientific language this is called synchronous rotation or tidal locking.
What is a tide?
In order to understand the essence of this phenomenon and confidently answer the question of whether the Moon rotates around its own axis, it is necessary to understand the essence of tidal phenomena.
Let's imagine two mountains on the surface of the Moon, one of which “looks” directly at the Earth, while the other is located in opposite point lunar ball. Obviously, if both mountains were not part of the same celestial body, but rotated around our planet independently, their rotation could not be synchronous, the one that is closer, according to the laws Newtonian mechanics, should rotate faster. That is why the masses of the lunar ball, located at points opposite to the Earth, tend to “run away from each other.”
How the Moon “stopped”
How do tidal forces affect things? heavenly body, it is convenient to analyze it using the example of our own planet. After all, we also revolve around the Moon, or rather, the Moon and Earth, as it should be in astrophysics, “dance in a circle” around the physical center of mass.
As a result of the action of tidal forces, both at the point closest and at the most distant point from the satellite, the level of water covering the Earth rises. Moreover, the maximum amplitude of the ebb and flow can reach 15 meters or more.
Another feature this phenomenon is that these tidal “humps” daily bend around the surface of the planet against its rotation, creating friction at points 1 and 2, and thus slowly stopping Earth in its rotation.
The impact of the Earth on the Moon is much stronger due to the difference in mass. And although there is no ocean on the Moon, there is rocks tidal forces act no worse. And the result of their work is obvious.
So does the Moon rotate on its axis? The answer is yes. But this rotation is closely related to the movement around the planet. Over millions of years, tidal forces have aligned the Moon's axial rotation with its orbital rotation.
What about the Earth?
Astrophysicists say that immediately after big collision, which caused the formation of the Moon, the rotation of our planet was much greater than now. The day lasted no more than five hours. But as a result of friction tidal waves on the bottom of the ocean, year after year, millennium after millennium, the rotation slowed down, and the current day already lasts 24 hours.
On average, each century adds 20-40 seconds to our day. Scientists suggest that in a couple of billion years our planet will look at the Moon in the same way as the Moon looks at it, that is, on the same side. True, this most likely will not happen, since even earlier the Sun, having turned into a red giant, will “swallow” both the Earth and its faithful companion- The moon.
By the way, tidal forces give earthlings not only an increase and decrease in the level of the world's oceans in the equator region. By influencing masses of metals in earth's core, deforming the hot center of our planet, the Moon helps maintain it in liquid state. And thanks to the active liquid core, our planet has its own magnetic field, protecting the entire biosphere from deadly solar wind and deadly cosmic rays.
They say about the Moon that it is a satellite of the Earth. The meaning of this is that the Moon accompanies the Earth in its constant movement around the Sun - she accompanies her. While the Earth moves around the Sun, the Moon moves around our planet.
The movement of the Moon around the Earth can generally be imagined as follows: either it is in the same direction where the Sun is visible, and at this time it moves, as it were, towards the Earth, rushing along its path around the Sun: then it passes to the other side and moves in the same direction. the direction in which our earth is rushing. But in general, the Moon accompanies our Earth. This actual movement of the Moon around the Earth can easily short term every patient and attentive observer will notice.
The proper movement of the Moon around the earth does not consist at all in the fact that it rises and sets or together with everything starry sky moves from east to west, from left to right. This apparent movement of the Moon is due to daily rotation the Earth itself, that is, for the same reason that the Sun rises and sets.
As for own movement The moon is around the Earth, then it affects itself in another way: the Moon seems to lag behind the stars in their apparent daily movement.
Indeed: notice any stars in visible close proximity to the Moon on this particular evening of your observations. Remember more precisely the position of the Moon relative to these stars. Then, look at the Moon a few hours later or the next evening. You will be convinced that the Moon is behind the stars you noticed. You will notice that the stars that were on the right of the Moon are now further from the Moon, and the Moon has become closer to the stars on the left, and the closer the more time has passed.
This clearly indicates that, moving apparently for us from east to west, due to the rotation of the Earth, the Moon at the same time slowly but steadily moves around the Earth from west to east, completing a full revolution around the Earth in about a month.
This distance is easy to imagine by comparing it with the apparent diameter of the Moon. It turns out that in one hour the Moon travels a distance in the sky approximately equal to its diameter, and in a day - an arc path equal to thirteen degrees.
The dotted line shows the orbit of the Moon, that closed, almost circular path along which, at a distance of about four hundred thousand kilometers, the Moon moves around the Earth. It is not difficult to determine the length of this huge path if we know the radius of the lunar orbit. The calculation leads to the following result: the orbit of the Moon is approximately two and a half million kilometers.
There is nothing easier to obtain now and the information we are interested in about the speed of the Moon around the Earth. But for this* we need to know more precisely the period during which the Moon will cover this entire huge path. By rounding, we can equate this period to a month, that is, approximately equal to seven hundred hours. Dividing the orbital length by 700, we can establish that the Moon covers a distance of approximately 3600 km in an hour, that is, about one kilometer per second.
This average speed The movement of the Moon shows that the Moon is not moving as slowly around the Earth as it might seem from observations of its displacement among the stars. On the contrary, the Moon is rapidly rushing along its orbit. But since we see the Moon at a distance of several hundred thousand kilometers, we barely notice its rapid movement. So the courier train, which we observe in the distance, seems to be barely moving, while it rushes past nearby objects with extreme speed.
For more accurate calculations of the Moon's speed, readers can use the following data.
The length of the lunar orbit is 2,414,000 km. The period of revolution of the Moon around the Earth is 27 days 7 hours. 43 min. 12 sec.
Did any of the readers think that there was a typo in the last line? Shortly before (p. 13) we said that the cycle of the lunar phases takes 29.53 or 29% of the day, and now we indicate that a full revolution of the Moon around Earth occurs in 27 g/z days. If the indicated data is correct, then what is the difference? We will talk about this a little further.
In the section on the question What is the rotation speed of the Moon around the Earth? given by the author chevron the best answer is Orbital speed1.022 km/s
Movement of the Moon
To a first approximation, we can assume that the Moon moves in an elliptical orbit with an eccentricity of 0.0549 and a semimajor axis of 384,399 km. The actual motion of the Moon is quite complex; when calculating it, many factors must be taken into account, for example, the oblateness of the Earth and strong influence The Sun, which attracts the Moon 2.2 times stronger than the Earth. More precisely, the movement of the Moon around the Earth can be represented as a combination of several movements:
rotation around the Earth in an elliptical orbit with a period of 27.32 days;
precession (plane rotation) of the lunar orbit with a period of 18.6 years (see also saros);
rotation of the major axis of the lunar orbit (apse line) with a period of 8.8 years;
periodic change in the inclination of the lunar orbit relative to the ecliptic from 4°59′ to 5°19′;
periodic change in the size of the lunar orbit: perigee from 356.41 Mm to 369.96 Mm, apogee from 404.18 Mm to 406.74 Mm;
the gradual removal of the Moon from the Earth (about 4 cm per year) so that its orbit is a slowly unwinding spiral. This is confirmed by measurements carried out over 25 years.
Answer from Suck through[newbie]
Here are the wise guys, Wikipedia Christmas trees. They copied from all sorts of Wikipedias of various insanity and even did not bother to remove references to internal resources like “-” or “(see also saros)”. The elliptical orbit has not yet gone anywhere, but an eccentricity of 0.0549 or a semimajor axis of 384,399 kilometers is already too much.
Well, they would write that the Moon moves around our planet in a rather elongated elliptical orbit and makes rather complex evolutionary movements and librations, that is, slow ones oscillatory movements clearly visible when observed from Earth. Average orbital speed earth's satellite is 1.023 km/s or 3682.8 kilometers per hour. That's all.
Answer from Wake up[newbie]
1.022
Answer from Yoni Tunoff[newbie]
The Moon moves in orbit around the Earth at a speed of 1.02 km per second. If the Moon rotates around its axis at the same speed, then dividing the length of the Moon’s equator by the speed of 1.02 km per second, we find out the time of 1 rotation of the Moon around its axis in seconds. The length of the Moon's equator is 10920.166 km.