The Moon is a satellite of our planet, which has attracted the attention of scientists and simply curious people since time immemorial. In the ancient world, both astrologers and astronomers devoted impressive treatises to it. Poets also did not lag behind them. Today, in this sense, little has changed: the orbit of the Moon, the features of its surface and interior are carefully studied by astronomers. Horoscope compilers also do not take their eyes off her. The influence of the satellite on the Earth is studied by both. Astronomers are studying how the interaction of two cosmic bodies affects the movement and other processes of each. During the study of the Moon, knowledge in this area has increased significantly.
Origin
According to scientists' research, the Earth and the Moon were formed at approximately the same time. Both bodies are 4.5 billion years old. There are several theories about the origin of the satellite. Each of them explains certain features of the Moon, but leaves several unresolved questions. The theory of a giant collision is considered to be the closest to the truth today.
According to the hypothesis, a planet similar in size to Mars collided with the young Earth. The impact was tangential and caused the ejection of most of the substance of this cosmic body into space, as well as some amount of terrestrial “material”. From this substance a new object was formed. The radius of the Moon's orbit was originally sixty thousand kilometers.
The giant collision hypothesis well explains many features of the structure and chemical composition of the satellite, and most of the characteristics of the Moon-Earth system. However, if we take the theory as a basis, some facts still remain unclear. Thus, the deficiency of iron on the satellite can only be explained by the fact that by the time of the collision, differentiation of the internal layers had occurred on both bodies. To date, there is no evidence that this happened. And yet, despite such counterarguments, the giant impact hypothesis is considered the main one throughout the world.
Options
The Moon, like most other satellites, has no atmosphere. Only traces of oxygen, helium, neon and argon were detected. The surface temperature in illuminated and darkened areas is therefore very different. On the sunny side it can rise to +120 ºС, and on the dark side it can drop to -160 ºС.
The average distance between the Earth and the Moon is 384 thousand km. The shape of the satellite is almost a perfect sphere. The difference between the equatorial and polar radius is small. They are 1738.14 and 1735.97 km respectively.
A full revolution of the Moon around the Earth takes just over 27 days. The movement of a satellite across the sky for an observer is characterized by a change of phases. The time from one full moon to another is slightly longer than the indicated period and is approximately 29.5 days. The difference arises because the Earth and satellite also move around the Sun. The moon has to travel a little more than one circle to be in its original position.
Earth-Moon system
The Moon is a satellite that is somewhat different from other similar objects. Its main feature in this sense is its mass. It is estimated at 7.35 * 10 22 kg, which is approximately 1/81 of that of the Earth. And if the mass itself is not something out of the ordinary in outer space, then its relationship with the characteristics of the planet is atypical. As a rule, the mass ratio in satellite-planet systems is somewhat smaller. Only Pluto and Charon can boast of a similar ratio. These two cosmic bodies some time ago began to be characterized as a system of two planets. It seems that this designation is also true in the case of the Earth and the Moon.
Movement of the Moon in orbit
The satellite makes one revolution around the planet relative to the stars in a sidereal month, which lasts 27 days, 7 hours and 42.2 minutes. The orbit of the Moon is an ellipse in shape. At different periods, the satellite is located either closer to the planet or further from it. The distance between the Earth and the Moon varies from 363,104 to 405,696 kilometers.
The trajectory of the satellite is associated with another piece of evidence in favor of the assumption that the Earth and the satellite must be considered as a system consisting of two planets. The Moon's orbit is not located near the equatorial plane of the Earth (as is typical for most satellites), but practically in the plane of rotation of the planet around the Sun. The angle between the ecliptic and the satellite’s trajectory is slightly more than 5º.
The Moon's orbit around the Earth is influenced by many factors. In this regard, determining the exact trajectory of the satellite is not the easiest task.
A little history
The theory explaining how the Moon moves was laid down back in 1747. The author of the first calculations, which brought scientists closer to understanding the peculiarities of the satellite’s orbit, was the French mathematician Clairaut. Then, back in the eighteenth century, the revolution of the Moon around the Earth was often put forward as an argument against Newton's theory. Calculations made using it differed greatly from the apparent movement of the satellite. Clairaut solved this problem.
The issue was studied by such famous scientists as d'Alembert and Laplace, Euler, Hill, Puiseau and others. The modern theory of lunar revolution actually began with the work of Brown (1923). The research of the British mathematician and astronomer helped eliminate the discrepancies between calculations and observation.
Not an easy task
The movement of the Moon consists of two main processes: rotation around its axis and revolution around our planet. It would not be so difficult to derive a theory to explain the movement of the satellite if its orbit were not affected by various factors. This is the attraction of the Sun, and the peculiarities of the shape of the Earth and other planets. Such influences disturb the orbit and predicting the exact position of the Moon at a particular period becomes a difficult task. In order to understand what’s going on here, let’s look at some parameters of the satellite’s orbit.
Ascending and descending node, apsidal line
As already mentioned, the Moon's orbit is inclined to the ecliptic. The trajectories of two bodies intersect at points called the ascending and descending nodes. They are located on opposite sides of the orbit relative to the center of the system, that is, the Earth. The imaginary straight line that connects these two points is designated as a line of nodes.
The satellite is closest to our planet at the perigee point. The maximum distance separates two cosmic bodies is when the Moon is at its apogee. The straight line connecting these two points is called the apse line.
Orbital disturbances
As a result of the influence of a large number of factors on the movement of the satellite at once, it essentially represents the sum of several movements. Let us consider the most noticeable disturbances that arise.
The first one is node line regression. The straight line connecting the two points of intersection of the plane of the lunar orbit and the ecliptic is not fixed in one place. It moves very slowly in the direction opposite (which is why it is called regression) to the movement of the satellite. In other words, the plane of the Moon's orbit rotates in space. It takes 18.6 years for one full rotation.
The line of apses is also moving. The movement of the straight line connecting the apocenter and periapsis is expressed in the rotation of the orbital plane in the same direction in which the Moon is moving. This happens much faster than in the case of a line of nodes. A full revolution takes 8.9 years.
In addition, the lunar orbit experiences fluctuations of a certain amplitude. Over time, the angle between its plane and the ecliptic changes. The range of values is from 4°59" to 5°17". Just as in the case of the line of nodes, the period of such fluctuations is 18.6 years.
Finally, the Moon's orbit changes its shape. It stretches out a little, then returns to its original configuration. In this case, the eccentricity of the orbit (the degree of deviation of its shape from a circle) changes from 0.04 to 0.07. Changes and return to the original position take 8.9 years.
Not so simple
In fact, four factors that need to be taken into account during calculations are not that many. However, they do not exhaust all disturbances in the satellite's orbit. In fact, each parameter of the Moon's movement is constantly influenced by a large number of factors. All this complicates the task of predicting the exact location of the satellite. And taking into account all these parameters is often the most important task. For example, calculating the trajectory of the Moon and its accuracy affects the success of the mission of the spacecraft sent to it.
The influence of the Moon on the Earth
The satellite of our planet is relatively small, but its influence is clearly visible. Perhaps everyone knows that it is the Moon that forms the tides on Earth. Here we must immediately make a reservation: the Sun also causes a similar effect, but due to the much greater distance, the tidal influence of the luminary is little noticeable. In addition, changes in water levels in the seas and oceans are also associated with the peculiarities of the rotation of the Earth itself.
The gravitational effect of the Sun on our planet is approximately two hundred times greater than that of the Moon. However, tidal forces primarily depend on the inhomogeneity of the field. The distance separating the Earth and the Sun smooths them out, so the influence of the Moon close to us is more powerful (twice as much as in the case of the luminary).
A tidal wave is formed on the side of the planet that is currently facing the night star. There is also a tide on the opposite side. If the Earth were motionless, then the wave would move from west to east, located exactly under the Moon. Its full revolution would be completed in just over 27 days, that is, in a sidereal month. However, the period around the axis is slightly less than 24 hours. As a result, the wave runs along the surface of the planet from east to west and completes one revolution in 24 hours and 48 minutes. Since the wave constantly encounters the continents, it moves forward in the direction of the Earth's movement and is ahead of the planet's satellite in its run.
Removing the Moon's orbit
A tidal wave causes the movement of a huge mass of water. This directly affects the motion of the satellite. An impressive part of the planet's mass is displaced from the line connecting the two bodies, and attracts the Moon towards itself. As a result, the satellite experiences a moment of force, which accelerates its movement.
At the same time, continents running into a tidal wave (they move faster than the wave, since the Earth rotates at a higher speed than the Moon rotates) experience a force that slows them down. This leads to a gradual slowdown in the rotation of our planet.
As a result of the tidal interaction of the two bodies, as well as the action and angular momentum, the satellite moves to a higher orbit. At the same time, the speed of the Moon decreases. It begins to move slower in orbit. Something similar is happening with the Earth. It slows down, resulting in a gradual increase in the length of the day.
The Moon is moving away from the Earth by about 38 mm per year. Research by paleontologists and geologists confirms the calculations of astronomers. The process of the gradual slowing down of the Earth and the removal of the Moon began approximately 4.5 billion years ago, that is, from the moment the two bodies were formed. Researchers' data support the assumption that previously the lunar month was shorter and the Earth rotated at a faster speed.
A tidal wave occurs not only in the waters of the world's oceans. Similar processes occur in the mantle and in the earth's crust. However, they are less noticeable because these layers are not as malleable.
The removal of the Moon and the slowing down of the Earth will not happen forever. Eventually, the planet's rotation period will become equal to the satellite's rotation period. The moon will “hover” over one area of the surface. The earth and the satellite will always face the same side towards each other. It is appropriate to remember here that part of this process has already been completed. It is tidal interaction that has led to the fact that the same side of the Moon is always visible in the sky. In space there is an example of a system in such equilibrium. These are already called Pluto and Charon.
The Moon and Earth are in constant interaction. It is impossible to say which body influences the other more. At the same time, both are exposed to the sun. Other, more distant, cosmic bodies also play a significant role. Taking into account all such factors makes it quite difficult to accurately construct and describe a model of the motion of a satellite in orbit around our planet. However, a huge amount of accumulated knowledge, as well as constantly improving equipment, make it possible to more or less accurately predict the position of the satellite at any time and predict the future that awaits each object individually and the Earth-Moon system as a whole.
The Earth is often, and not without reason, called the double planet Earth-Moon. The Moon (Selene, goddess of the Moon in Greek mythology), our celestial neighbor, was the first to be directly studied.
The Moon is a natural satellite of the Earth, located at a distance of 384 thousand km (60 radii of the Earth). The average radius of the Moon is 1738 km (almost 4 times less than the Earth's). The Moon's mass is 1/81 that of the Earth, which is significantly greater than similar ratios for other planets in the Solar System (except for the Pluto-Charon pair); therefore, the Earth–Moon system is considered a double planet. It has a common center of gravity - the so-called barycenter, which is located in the body of the Earth at a distance of 0.73 radii from its center (1700 km from the surface of the Ocean). Both components of the system rotate around this center, and it is the barycenter that moves in orbit around the Sun. The average density of lunar substance is 3.3 g/cm 3 (terrestrial - 5.5 g/cm 3). The volume of the Moon is 50 times smaller than the Earth. The force of lunar gravity is 6 times weaker than the earth's. The moon rotates around its axis, which is why it is slightly flattened at the poles. The axis of rotation of the Moon makes an angle of 83°22" with the plane of the lunar orbit. The plane of the Moon's orbit does not coincide with the plane of the Earth's orbit and is inclined to it at an angle of 5°9". The places where the orbits of the Earth and the Moon intersect are called the nodes of the lunar orbit.
The orbit of the Moon is an ellipse, in one of the foci of which the Earth is located, therefore the distance from the Moon to the Earth varies from 356 to 406 thousand km. The period of the orbital revolution of the Moon and, accordingly, the same position of the Moon on the celestial sphere is called the sidereal (sidereal) month (Latin sidus, sideris (genus) - star). It is 27.3 Earth days. The sidereal month coincides with the period of the Moon’s daily rotation around its axis due to their identical angular speed (approx. 13.2° per day), established due to the braking effect of the Earth. Due to the synchronicity of these movements, the Moon always faces us with one side. However, we see almost 60% of its surface due to libration - the apparent swaying of the Moon up and down (due to the mismatch of the planes of the lunar and Earth's orbits and the inclination of the Moon's rotation axis to the orbit) and left and right (due to the fact that the Earth is in one of the foci of the lunar orbit, and the visible hemisphere of the Moon faces the center of the ellipse).
When moving around the Earth, the Moon takes different positions relative to the Sun. Associated with this are the different phases of the Moon, i.e., different shapes of its visible part. The main four phases are: new moon, first quarter, full moon, last quarter. The line on the surface of the Moon separating the illuminated part of the Moon from the unlit part is called the terminator.
During the new moon, the Moon is between the Sun and the Earth and faces the Earth with its unlit side, therefore invisible. In the first quarter, the Moon is visible from the Earth at an angular distance of 90° from the Sun, and the sun's rays illuminate only the right half of the side of the Moon facing the Earth. During a full moon, the Earth is between the Sun and the Moon, the hemisphere of the Moon facing the Earth is brightly illuminated by the Sun, and the Moon is visible as a full disk. During the last quarter, the Moon is again visible from the Earth at an angular distance of 90° from the Sun, and the sun's rays illuminate the left half of the visible side of the Moon. In the intervals between these main phases, the Moon is visible either as a crescent or as an incomplete disk.
The period of complete change of lunar phases, i.e., the period of the Moon returning to its original position relative to the Sun and Earth, is called the synodic month. It averages 29.5 mean solar days. During the synodic month on the Moon there is a change of day and night once, the duration of which is = 14.7 days. The synodic month is more than two days longer than the sidereal month. This is the result of the fact that the direction of the axial rotation of the Earth and the Moon coincides with the direction of the orbital motion of the Moon. When the Moon completes a full revolution around the Earth in 27.3 days, the Earth will advance approximately 27° in its orbit around the Sun, since its angular orbital speed is about 1° per day. In this case, the Moon will take the same position among the stars, but will not be in the full moon phase, since for this it needs to advance in its orbit another 27° behind the “escaped” Earth. Since the angular velocity of the Moon is approximately 13.2° per day, it covers this distance in about two days and additionally moves another 2° behind the moving Earth. As a result, the synodic month turns out to be more than two days longer than the sidereal month. Although the Moon moves around the Earth from west to east, its apparent movement in the sky occurs from east to west due to the high speed of rotation of the Earth compared to the orbital movement of the Moon. Moreover, during the upper culmination (the highest point of its path in the sky), the Moon shows the direction of the meridian (north - south), which can be used for approximate orientation on the ground. And since the upper culmination of the Moon at different phases occurs at different hours of the day: during the first quarter - about 18 o'clock, during the full moon - at midnight, during the last quarter - about 6 o'clock in the morning (local time), this can also be used for rough estimate of time at night.
In 1609, after the invention of the telescope, humanity was able to examine its space satellite in detail for the first time. Since then, the Moon has been the most studied cosmic body, as well as the first one that man managed to visit.
The first thing we have to figure out is what our satellite is? The answer is unexpected: although the Moon is considered a satellite, technically it is the same full-fledged planet as the Earth. It has large dimensions - 3476 kilometers across at the equator - and a mass of 7.347 × 10 22 kilograms; The Moon is only slightly inferior to the smallest planet in the Solar System. All this makes it a full participant in the Moon-Earth gravitational system.
Another such tandem is known in the Solar System, and Charon. Although the entire mass of our satellite is a little more than a hundredth of the mass of the Earth, the Moon does not orbit the Earth itself - they have a common center of mass. And the proximity of the satellite to us gives rise to another interesting effect, tidal locking. Because of it, the Moon always faces the same side towards the Earth.
Moreover, from the inside, the Moon is structured like a full-fledged planet - it has a crust, a mantle and even a core, and in the distant past there were volcanoes on it. However, nothing remains of the ancient landscapes - over the course of four and a half billion years of the Moon’s history, millions of tons of meteorites and asteroids fell on it, furrowing it, leaving craters. Some of the impacts were so strong that they tore through its crust all the way to its mantle. The pits from such collisions formed lunar maria, dark spots on the Moon that are easily visible from. Moreover, they are present exclusively on the visible side. Why? We will talk about this further.
Among cosmic bodies, the Moon influences the Earth the most - except, perhaps, the Sun. Lunar tides, which regularly raise water levels in the world's oceans, are the most obvious, but not the most powerful, impact of the satellite. Thus, gradually moving away from the Earth, the Moon slows down the rotation of the planet - a solar day has grown from the original 5 to the modern 24 hours. The satellite also serves as a natural barrier against hundreds of meteorites and asteroids, intercepting them as they approach the Earth.
And without a doubt, the Moon is a tasty object for astronomers: both amateurs and professionals. Although the distance to the Moon has been measured to within a meter using laser technology, and soil samples from it have been brought back to Earth many times, there is still room for discovery. For example, scientists are hunting for lunar anomalies - mysterious flashes and lights on the surface of the Moon, not all of which have an explanation. It turns out that our satellite hides much more than is visible on the surface - let's understand the secrets of the Moon together!
Topographic map of the Moon
Characteristics of the Moon
Scientific study of the Moon today is more than 2200 years old. The motion of a satellite in the Earth's sky, its phases and distance from it to the Earth were described in detail by the ancient Greeks - and the internal structure of the Moon and its history are studied to this day by spacecraft. Nevertheless, centuries of work by philosophers, and then physicists and mathematicians, have provided very accurate data about how our Moon looks and moves, and why it is the way it is. All information about the satellite can be divided into several categories that flow from each other.
Orbital characteristics of the Moon
How does the Moon move around the Earth? If our planet were stationary, the satellite would rotate in an almost perfect circle, from time to time slightly approaching and moving away from the planet. But the Earth itself is around the Sun - the Moon has to constantly “catch up” with the planet. And our Earth is not the only body with which our satellite interacts. The Sun, located 390 times farther than the Earth from the Moon, is 333 thousand times more massive than the Earth. And even taking into account the inverse square law, according to which the intensity of any energy source drops sharply with distance, the Sun attracts the Moon 2.2 times stronger than the Earth!
Therefore, the final trajectory of our satellite’s motion resembles a spiral, and a complex one at that. The axis of the lunar orbit fluctuates, the Moon itself periodically approaches and moves away, and on a global scale it even flies away from the Earth. These same fluctuations lead to the fact that the visible side of the Moon is not the same hemisphere of the satellite, but its different parts, which alternately turn towards the Earth due to the “swaying” of the satellite in orbit. These movements of the Moon in longitude and latitude are called librations, and allow us to look beyond the far side of our satellite long before the first flyby by spacecraft. From east to west, the Moon rotates 7.5 degrees, and from north to south - 6.5. Therefore, both poles of the Moon can be easily seen from Earth.
The specific orbital characteristics of the Moon are useful not only to astronomers and cosmonauts - for example, photographers especially appreciate the supermoon: the phase of the Moon in which it reaches its maximum size. This is a full moon during which the Moon is at perigee. Here are the main parameters of our satellite:
- The Moon's orbit is elliptical, its deviation from a perfect circle is about 0.049. Taking into account orbital fluctuations, the minimum distance of the satellite to the Earth (perigee) is 362 thousand kilometers, and the maximum (apogee) is 405 thousand kilometers.
- The common center of mass of the Earth and the Moon is located 4.5 thousand kilometers from the center of the Earth.
- A sidereal month - the complete passage of the Moon in its orbit - takes 27.3 days. However, for a complete revolution around the Earth and a change in lunar phases, it takes 2.2 days more - after all, during the time that the Moon moves in its orbit, the Earth flies a thirteenth part of its own orbit around the Sun!
- The Moon is tidally locked into the Earth - it rotates on its axis at the same speed as around the Earth. Because of this, the Moon is constantly turned to the Earth with the same side. This condition is typical for satellites that are very close to the planet.
- Night and day on the Moon are very long - half the length of an earthly month.
- During those periods when the Moon comes out from behind the globe, it is visible in the sky - the shadow of our planet gradually slides off the satellite, allowing the Sun to illuminate it, and then covers it back. Changes in the illumination of the Moon, visible from the Earth, are called ee. During the new moon, the satellite is not visible in the sky; during the young moon phase, its thin crescent appears, resembling the curl of the letter “P”; in the first quarter, the Moon is exactly half illuminated, and during the full moon it is most noticeable. Further phases - the second quarter and the old moon - occur in the reverse order.
Interesting fact: since the lunar month is shorter than the calendar month, sometimes there can be two full moons in one month - the second is called a “blue moon”. It is as bright as an ordinary light - it illuminates the Earth by 0.25 lux (for example, ordinary lighting inside a house is 50 lux). The Earth itself illuminates the Moon 64 times stronger - as much as 16 lux. Of course, all the light is not our own, but reflected sunlight.
- The Moon's orbit is inclined to the Earth's orbital plane and regularly crosses it. The satellite's inclination is constantly changing, varying between 4.5° and 5.3°. It takes more than 18 years for the Moon to change its inclination.
- The Moon moves around the Earth at a speed of 1.02 km/s. This is much less than the speed of the Earth around the Sun - 29.7 km/s. The maximum speed of the spacecraft achieved by the Helios-B solar probe was 66 kilometers per second.
Physical parameters of the Moon and its composition
It took people a long time to understand how big the Moon is and what it consists of. Only in 1753, the scientist R. Bošković was able to prove that the Moon does not have a significant atmosphere, as well as liquid seas - when covered by the Moon, the stars disappear instantly, when their presence would make it possible to observe their gradual “attenuation”. It took another 200 years for the Soviet station Luna 13 to measure the mechanical properties of the lunar surface in 1966. And nothing was known at all about the far side of the Moon until 1959, when the Luna-3 apparatus was able to take its first photographs.
The Apollo 11 spacecraft crew returned the first samples to the surface in 1969. They also became the first people to visit the Moon - until 1972, 6 ships landed on it and 12 astronauts landed. The reliability of these flights was often doubted - however, many of the critics' points were based on their ignorance of space affairs. The American flag, which, according to conspiracy theorists, “could not have flown in the airless space of the Moon,” is in fact solid and static - it was specially reinforced with solid threads. This was done specifically in order to take beautiful pictures - a sagging canvas is not so spectacular.
Many distortions of colors and relief shapes in the reflections on the helmets of the spacesuits in which counterfeits were sought were due to gold plating on the glass, which protected against ultraviolet. Soviet cosmonauts who watched the live broadcast of the astronaut landing also confirmed the authenticity of what was happening. And who can deceive an expert in his field?
And complete geological and topographic maps of our satellite are being compiled to this day. In 2009, the Lunar Reconnaissance Orbiter (LRO) space station not only delivered the most detailed images of the Moon in history, but also proved the presence of large amounts of frozen water on it. He also put an end to the debate about whether people were on the Moon by filming traces of the activities of the Apollo team from low lunar orbit. The device was equipped with equipment from several countries, including Russia.
Since new space states like China and private companies are joining the lunar exploration, new data is arriving every day. We have collected the main parameters of our satellite:
- The surface area of the Moon occupies 37.9x10 6 square kilometers - about 0.07% of the total area of the Earth. Incredibly, this is only 20% greater than the area of all human-inhabited areas on our planet!
- The average density of the Moon is 3.4 g/cm 3 . It is 40% less than the density of the Earth - primarily due to the fact that the satellite is devoid of many heavy elements like iron, which our planet is rich in. In addition, 2% of the Moon's mass is regolith - small crumbs of rock created by cosmic erosion and meteorite impacts, the density of which is lower than normal rock. Its thickness in some places reaches tens of meters!
- Everyone knows that the Moon is much smaller than the Earth, which affects its gravity. The acceleration of free fall on it is 1.63 m/s 2 - only 16.5 percent of the entire gravitational force of the Earth. The astronauts' jumps on the Moon were very high, even though their spacesuits weighed 35.4 kilograms - almost like knight's armor! At the same time, they were still holding back: a fall in a vacuum was quite dangerous. Below is a video of the astronaut jumping from the live broadcast.
- Lunar maria cover about 17% of the entire Moon - mainly its visible side, which is covered by almost a third. They are traces of impacts from particularly heavy meteorites, which literally tore the crust off the satellite. In these places, only a thin, half-kilometer layer of solidified lava—basalt—separates the surface from the lunar mantle. Because the concentration of solids increases closer to the center of any large cosmic body, there is more metal in the lunar maria than anywhere else on the Moon.
- The main form of relief of the Moon is craters and other derivatives from impacts and shock waves from steroids. Huge lunar mountains and circuses were built and changed the structure of the surface of the Moon beyond recognition. Their role was especially strong at the beginning of the history of the Moon, when it was still liquid - the falls raised whole waves of molten stone. This also caused the formation of lunar seas: the side facing the Earth was hotter due to the concentration of heavy substances in it, which is why asteroids affected it more strongly than the cool back side. The reason for this uneven distribution of matter was the gravity of the Earth, which was especially strong at the beginning of the Moon’s history, when it was closer.
- In addition to craters, mountains and seas, there are caves and cracks in the moon - surviving witnesses of the times when the bowels of the Moon were as hot as , and volcanoes were active on it. These caves often contain water ice, just like the craters at the poles, which is why they are often considered as sites for future lunar bases.
- The real color of the Moon's surface is very dark, closer to black. All over the Moon there are a variety of colors - from turquoise blue to almost orange. The light gray tint of the Moon from the Earth and in the photographs is due to the high illumination of the Moon by the Sun. Due to its dark color, the surface of the satellite reflects only 12% of all rays falling from our star. If the Moon were brighter, during full moons it would be as bright as day.
How was the Moon formed?
The study of lunar minerals and its history is one of the most difficult disciplines for scientists. The surface of the Moon is open to cosmic rays, and there is nothing to retain heat at the surface - therefore, the satellite heats up to 105 ° C during the day, and cools down to –150 ° C at night. The two-week duration of day and night increases the effect on the surface - and as a result, the minerals of the Moon change beyond recognition with time. However, we managed to find out something.
Today it is believed that the Moon is the product of a collision between a large embryonic planet, Theia, and the Earth, which occurred billions of years ago when our planet was completely molten. Part of the planet that collided with us (and it was the size of ) was absorbed - but its core, along with part of the surface matter of the Earth, was thrown into orbit by inertia, where it remained in the form of the Moon.
This is proven by the deficiency of iron and other metals on the Moon, already mentioned above - by the time Theia tore out a piece of earthly matter, most of the heavy elements of our planet were drawn by gravity inward, to the core. This collision affected the further development of the Earth - it began to rotate faster, and its axis of rotation tilted, which made the change of seasons possible.
Then the Moon developed like an ordinary planet - it formed an iron core, mantle, crust, lithospheric plates and even its own atmosphere. However, the low mass and composition poor in heavy elements led to the fact that the interior of our satellite quickly cooled, and the atmosphere evaporated from the high temperature and lack of a magnetic field. However, some processes inside still occur - due to movements in the lithosphere of the Moon, moonquakes sometimes occur. They represent one of the main dangers for future colonizers of the Moon: their scale reaches 5.5 points on the Richter scale, and they last much longer than those on Earth - there is no ocean capable of absorbing the impulse of the movement of the Earth’s interior.
The main chemical elements on the Moon are silicon, aluminum, calcium and magnesium. The minerals that form these elements are similar to those on Earth and are even found on our planet. However, the main difference between the minerals of the Moon is the absence of exposure to water and oxygen produced by living beings, a high proportion of meteorite impurities and traces of the effects of cosmic radiation. The Earth's ozone layer was formed quite a long time ago, and the atmosphere burns most of the mass of falling meteorites, allowing water and gases to slowly but surely change the appearance of our planet.
Future of the Moon
The Moon is the first cosmic body after Mars that claims priority for human colonization. In a sense, the Moon has already been mastered - the USSR and the USA left state regalia on the satellite, and orbital radio telescopes are hiding behind the far side of the Moon from the Earth, a generator of a lot of interference on the air. However, what does the future hold for our satellite?
The main process, which has already been mentioned more than once in the article, is the moving away of the Moon due to tidal acceleration. It happens quite slowly - the satellite moves away no more than 0.5 centimeters per year. However, something completely different is important here. Moving away from the Earth, the Moon slows down its rotation. Sooner or later, a moment may come when a day on Earth will last as long as a lunar month - 29–30 days.
However, the removal of the Moon will have its limit. After reaching it, the Moon will begin to approach the Earth in turns - and much faster than it was moving away. However, it will not be possible to completely crash into it. 12–20 thousand kilometers from the Earth, its Roche lobe begins - the gravitational limit at which a satellite of a planet can maintain a solid shape. Therefore, the Moon will be torn into millions of small fragments as it approaches. Some of them will fall to Earth, causing a bombardment thousands of times more powerful than nuclear, and the rest will form a ring around the planet like . However, it will not be so bright - the rings of gas giants consist of ice, which is many times brighter than the dark rocks of the Moon - they will not always be visible in the sky. The ring of the Earth will create a problem for astronomers of the future - if, of course, by that time there is anyone left on the planet.
Colonization of the Moon
However, all this will happen in billions of years. Until then, humanity views the Moon as the first potential object for space colonization. However, what exactly is meant by “lunar exploration”? Now we will look at the immediate prospects together.
Many people think of space colonization as similar to New Age colonization of Earth - finding valuable resources, extracting them, and then bringing them back home. However, this does not apply to space - in the next couple of hundred years, delivering a kilogram of gold even from the nearest asteroid will cost more than extracting it from the most complex and dangerous mines. Also, the Moon is unlikely to act as a “dacha sector of the Earth” in the near future - although there are large deposits of valuable resources there, it will be difficult to grow food there.
But our satellite may well become a base for further space exploration in promising directions - for example, Mars. The main problem of astronautics today is restrictions on the weight of spacecraft. To launch, you have to build monstrous structures that require tons of fuel - after all, you need to overcome not only the gravity of the Earth, but also the atmosphere! And if this is an interplanetary ship, then it also needs to be refueled. This seriously constrains designers, forcing them to choose economy over functionality.
The moon is much better suited as a launch pad for spaceships. The lack of an atmosphere and low speed to overcome the Moon's gravity - 2.38 km/s versus 11.2 km/s on Earth - make launches much easier. And the satellite's mineral deposits make it possible to save on the weight of fuel - a stone around the neck of astronautics, which occupies a significant proportion of the mass of any apparatus. If the production of rocket fuel were developed on the Moon, it would be possible to launch large and complex spacecraft assembled from parts delivered from Earth. And assembly on the Moon will be much easier than in low-Earth orbit - and much more reliable.
The technologies existing today make it possible, if not completely, then partially to implement this project. However, any steps in this direction require risk. The investment of huge amounts of money will require research for the necessary minerals, as well as the development, delivery and testing of modules for future lunar bases. And the estimated cost of launching even the initial elements alone can ruin an entire superpower!
Therefore, the colonization of the Moon is not so much the work of scientists and engineers, but of the people of the whole world to achieve such valuable unity. For in the unity of humanity lies the true strength of the Earth.
Moon- the only celestial body that orbits the Earth, not counting the artificial Earth satellites created by man in recent 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 the lunar phases change: 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 lunar crescent after the new moon was called “neomenia” (“new moon”) by the Greeks. 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 are an interesting natural phenomenon, familiar to man since ancient times. They occur relatively often, but are not visible from all areas of the earth’s surface and therefore seem rare to many.
A 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.
The longest duration of the total eclipse phase does 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 brightest stars and planets appear in the darkened sky, and around the Sun you can see a beautiful radiant glow of pearl color - the solar corona, which is the outer layers of the solar atmosphere, not visible outside the eclipse. for 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 by the lunar shadow, where sunlight penetrates from neighboring zones where a total eclipse does not occur, but only a partial eclipse 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 at its greatest distance from the Earth, then it will have a slightly smaller apparent size 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. The largest number of lunar eclipses in a year is 3, 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 over a much larger area than any solar eclipse.
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 an almost circular spot, the diameter of which can reach at most 270 km. This spot will cover only a negligible fraction of the earth's surface. At the moment, only this part of the Earth will see a total solar eclipse.
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 a 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.
The modern theory of studying the figure of the Earth originates from Newton (1643 - 1727), who discovered the law of universal gravitation and applied 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 a 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 The average density of the 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 that most of the Earth is covered with water, which gives grounds to accept 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 the field 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.
Fundamental studies of the figure of the Earth, carried out 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 German mathematician Johann Benedict Listing to refer to a geometric figure, more precisely than an ellipsoid of revolution, that reflects 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 there are 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.
Hello dear readers of the site! Even 4 years ago, looking at the Moon on winter nights, I came to the conclusion that it was moving quite funny across the sky. Then I was not familiar with celestial mechanics, and had no idea that its orbit is inclined to the ecliptic by 5.6 degrees, and in general astronomy was included in physics at the thin lyceum and was given 4 hours. But even then it became clear that the orbital movement of the Moon does not go in a circle at all, as we simply imagine. Later, I was shocked by the pictures from the lunar rovers, and finally forced me to pay attention to the topic of the Moon. Now I’m already studying to become a planetary scientist, while simultaneously absorbing tons of related information. I would like to share with the reader some very interesting information on celestial mechanics, in particular our satellite the Moon. Modern astronomers tend to consider the earth-moon system as a single conglomerate, and there is a reasonable opinion that the system is a double planet. Quite reasonably, it is impossible to consider the movement and interaction with space and other celestial bodies of the mistress of the night separately from her mistress the Earth. To better understand the question, I will give diagrams of the movement of the Moon around the Earth, the movement of the system around the sun, and I will also briefly describe 13 movements of the earth in which the Moon participates, and the reason for some of them is it.
There are more than 13 earth movements, in this question we will not even touch on all 13. The first thing you should know is that the periods of revolution of the Moon around its axis and the period of revolution around the Earth are synchronized and we always see one side of the Moon. The second is that, strictly speaking, the center of mass flies around the sun in the orbit of the earth-moon system, and the subjects of the system circle around it.
So the movements of the Earth are in order, and the Moon also participates in them. To one degree or another, all factors of both subjects of the earth-moon system are mutually reflected. 1) The first movement of the Earth is the rotation of the planet around its own axis
2) The second movement of the Earth - the revolution of the planet in orbit around the Sun 3) The third movement of the Earth - precession 4) The fourth movement of the Earth - nutation 5) The fifth movement of the Earth - a change in the inclination of the ecliptic 6) The sixth movement of the Earth - a change in the eccentricity of the Earth's orbit 7) The seventh movement of the Earth - secular change of perihelion 8) Eighth movement of the Earth - parallactic inequality of the Sun 9) Ninth movement of the Earth - "parade of planets" 10) Tenth movement of the Earth - the effects of the attraction of planets: "disturbances" or "perturbations" 11) Eleventh movement of the Earth - caused by the translational movement of the Sun towards Vega 12) The twelfth movement of the Earth is movement around the galactic core 13) The thirteenth movement of the Earth is movement relative to the center of a cluster of nearby galaxies. Of course, we will touch only on the most pronounced aspects affecting the difficult movement in orbit. Astronomers know about the so-called 13 movements of the Earth and take them into account when determining the orbit of the Moon. Let me remind you that modern science considers the movement of the moon-earth system in orbit as a single whole. The Moon participates by force of circumstances in all 13 movements of the Earth, being the cause of some of them, but the Earth also forces the Moon to “dance to its tune.” What exactly does it and the sun cause the Moon to librate, accelerate towards perigee and slow down towards apogee in its orbit. Change the position of the semimajor axis of the Moon’s orbit in relation to the sun, which changes the quality of eclipses - total and annular. If at the moment of an eclipse the Moon is at perigee, then we see a total eclipse in the center of its shadow. On the contrary, when the Moon is closer to aphelion at the nodes of its orbit, and the cone of its shadow does not touch the earth, we will see an annular eclipse in the center of the penumbra. The Moon's orbit is not strictly circular, having a slight eccentricity that causes changes in its orbital speed and supermoons. Such accelerations and decelerations in orbit are the cause of physical and optical librations, due to which we see 59% of the lunar surface. Librations are distinguished by latitude and longitude; the Moon actually sways as it circles in space. If the eyes of an outside observer were in the ecliptic plane, he would see a strange “drunken” dance of the Moon and the Earth. Old Lady Earth would sway strangely in this waltz, while her pale friend would make irregular figure eights around her. Swinging and speeding up in the small figure eight loop and slowing down in the big one. The middle of the figure eight exactly coincides with the nodes of the lunar orbit. Orbital nodes are the points at which the lunar orbit passes through the ecliptic plane. If an observer looks, for example, from the north pole, he will see an equally strange picture. The conventional ellipse of the orbit will be drawn as a somewhat wavy zigzag line with smoothed waves at the perigee and pronounced at the apogee, and the figure described by the Moon will somewhat resemble a pear, where the wide part of the fruit is the apogee of the orbit. However, the figure will have features depending on whether the perigee point falls on, for example, a new moon or a full moon; the sun, with its gravity, will add strangeness to the described figure. Everything in the universe is in constant motion and everything is interconnected, the pattern of the Moon's orbit will also be influenced by such movement as the parade of planets in combination with the position relative to the sun. The same applies to the perigee and aphelion of the earth's orbit relative to the sun and the many combinations described here. I hope the reader enjoys this astronomical sketch.