Is it true that the moon is moving away from the earth? Can the moon fly away from the Earth? Why is the Moon moving away from the Earth?

We are accustomed to the fact that the Moon is a satellite of the Earth. However, will it always be like this? According to the general director of the Central Scientific Research Institute of Mechanical Engineering, Gennady Raikunov, our night star may sooner or later leave the earth's orbit and become an independent planet. In this case, the Earth will turn into a lifeless desert...

Raikunov assures that the Moon may well repeat the fate of Mercury, which is supposed to have once been a satellite of Venus, but then “flew away” from it. After this, the conditions on Venus became unsuitable for life, despite the fact that it is an Earth-like planet.

“The Moon also moves away from the Earth every year, and someday, apparently, if reverse processes do not happen, it must leave the Earth,” the director of TsNIIMash made such a statement at the ongoing air show in Bourges. “Won’t it turn out that the Earth will go along the path of Venus, when conditions are formed that are unsuitable for existing life forms - an aggressive atmosphere, enormous pressure, the greenhouse effect, etc.?”

According to the scientist, space research is currently being carried out to help find out whether living conditions on our planet will change if it loses its natural satellite, and how the worst case scenario can be prevented.

Gennady Raikunov has long been concerned about the fate of the Moon. Earlier, he called the satellite the “seventh continent” and said that it was necessary to create a permanently functioning base on it, whose employees would be engaged in research and use of the resources of this celestial body.

The Moon is now moving around the Earth in a nearly elliptical orbit, counterclockwise (as viewed from the North Pole) at an average speed of 1.02 kilometers per second. In fact, the movement of our natural satellite is a rather complex process, which is influenced by various disturbances caused by the attraction of the Sun, planets and the oblate shape of the Earth. How likely is the scenario proposed by Raikunov?

Sergei Popov, a researcher at the Sternberg State Astronomical Institute of Moscow State University (SAI), confirmed that the Moon is indeed moving away from the Earth, but very slowly - the speed of removal is about 38 millimeters per year. “Over a few billion years, the Moon’s orbital period will simply increase by one and a half times, and that’s all,” Popov said. “The Moon cannot completely leave. It has nowhere to get the energy to escape.”

According to Surdin, under the influence of solar tides (the movement of water masses caused by the attraction not of the Moon, but of the Sun. - Ed. ) the rotation speed of our planet is gradually decreasing, and the speed of the satellite’s removal will gradually decrease. In about five billion years, the radius of the lunar orbit will reach its maximum value - 463 thousand kilometers, and the length of the earth's day will increase to 870 hours.

“The statement “The Moon can leave the Earth’s orbit and turn into a planet” is incorrect,” Vladimir Surdin commented on the words of his colleague Raikunov. “The solar tides will continue to slow down the Earth. But now the Moon will outstrip the Earth’s rotation, and tidal friction will begin to slow down its movement. In As a result, the Moon will begin to approach the Earth, albeit very slowly, since the strength of the solar tides is small."

But even if we imagine that the Moon is no longer a satellite of the Earth, this will not turn our planet into a semblance of lifeless Venus, scientists say. Thus, the head of the laboratory of comparative planetology at the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, Alexander Bazilevsky, commented: “The departure of the Moon will have little effect on the conditions on the Earth’s surface. There will be no ebbs and flows (they are mainly lunar), and the nights will be moonless. We will survive.”

Raikunov’s colleagues do not entirely agree with his statement that Mercury was once a satellite of Venus. “Calculations have shown that this is possible, which, however, does not prove that it was so,” Bazilevsky said. In addition, he believes, the development of the Earth and Venus cannot follow the same paths, since in the Venusian atmosphere there is an increased content of the heavy isotope of hydrogen - deuterium.

“This may be due to the fact that Venus once had a relatively large amount of water. When water in the upper layers of the atmosphere decomposed into hydrogen and oxygen, the light isotope of hydrogen escaped into space faster than the heavy one, and the observed anomaly resulted,” says the scientist. “But It’s not a fact that there was liquid water on the surface of Venus and not steam in the atmosphere, that is, it’s not a fact that it wasn’t as hot there as it is now.”

Let's start with the fact that back in 1695, the great scientist Edmund Halley noticed that the records that were left by earlier scientists about the times and places of solar eclipses did not coincide with the calculated ones. Halley, using modern information about eclipses, the movement of the Moon and the Sun, referring to Isaac Newton's new universal law of gravitation (1687), calculated,
the exact places and times where eclipses should have occurred in ancient times, and then compared the results obtained with data on eclipses that were actually observed more than 2000 years earlier. As it turned out, they did not match. Halley did not doubt the validity of Newton's law of gravitation and resisted the temptation to conclude that the force of gravity had changed over time. Instead, he suggested that the length of Earth's day must have increased slightly since then.

If the rotation of the Earth has indeed slowed down a little, then in order to maintain the total angular momentum in the Earth-Moon system, it is necessary that the Moon receive additional angular momentum. This transfer of angular momentum to the Moon corresponds to its movement along a weakly untwisting spiral with a gradual removal from the Earth and with a corresponding slowdown in orbital motion. If 2000 years ago the Earth's day was indeed a little shorter, the Earth rotated on its axis a little faster, the Moon's orbit was a little closer and the Moon moved along it a little faster, then the theoretical predictions and historical observations of replacements coincide. Scientists soon realized that Halley was right.

What could cause such a slowdown in the Earth's rotation? These are the ebbs and flows. Ebbs and flows
The gravitational influence of the Earth on the Moon and vice versa is quite large. Different parts of, say, the Earth are subject to the attraction of the Moon in different ways: the side facing the Moon is to a greater extent, the opposite side is to a lesser extent, since it is further away from our satellite. As a result, different parts of the Earth tend to move towards the Moon at different speeds. The surface facing the Moon swells, the center of the Earth moves less, and the opposite surface lags behind, and a bulge also forms on this side - due to the “lag”. The earth's crust deforms reluctantly; on land we do not notice tidal forces. But everyone has heard about changes in sea level, about ebbs and flows. Water is influenced by the Moon, forming tidal humps on two opposite sides of the planet. As the Earth rotates, it “exposes” its different sides to the Moon, and the tidal hump moves across the surface. Such deformations of the earth's crust cause internal friction, which slows down the rotation of our planet. It used to spin much faster. The Moon is even more affected by tidal forces, because the Earth is much more massive and larger. The speed of rotation of the Moon has slowed down so much that it obediently turned one side towards our planet, and the tidal hump no longer runs along the lunar surface.

The influence of these two bodies on each other will lead in the distant future to the fact that the Earth will eventually turn one side towards the Moon. In addition, tidal forces caused by the proximity of the Earth, as well as the influence of the Sun, slow down the movement of the Moon in its orbit around the Earth. The slowdown is accompanied by the Moon moving away from the center of the Earth. As a result, this could lead to the loss of the Moon...

During the Apollo missions to the Moon in 1969-1972, 3 laser radiation reflectors were placed on the lunar surface. Since then, scientists have had access to a way to very accurately determine the distance to our satellite. If you send a powerful laser signal from the earth to the lunar reflector and measure with sufficient accuracy the time after which it returns, you can determine the distance to the Moon with an error not exceeding one centimeter. According to such experiments, the Moon is moving away from the Earth by 3.8 centimeters per year. Like this.

The ancient age of the Moon also raises doubts in connection with another parameter of its orbit - its inclination. Currently it varies from 18 to 28 degrees. What was the initial inclination of the lunar orbit if the Moon moved away from the Earth over 4.6 billion years? To simplify the problem, we will assume that the Moon simultaneously rotates around two mutually perpendicular axes - the Earth’s rotation axis (equatorial rotation) and the axis coinciding with the Earth’s equatorial diameter (polar rotation). Tidal friction affects changes in these orbits differently - the radius of polar rotation, unlike the radius of equatorial rotation, does not increase, but decreases (about 30 times slower). This means that while the radius of equatorial rotation increased by more than 300 thousand km, the polar radius decreased by almost 10 thousand km and was initially about 130 - 190 thousand km. If the Moon was formed 4.6 billion years ago, it would initially have been in a very high polar orbit around the Earth.

Launching an artificial Earth satellite into a polar orbit requires much more energy than a similar launch into an equatorial orbit (which is why cosmodromes are trying to be built closer to the equator), because high equatorial speed somewhat reduces the speed at which it is necessary to accelerate the launched object.

In the case assumed by the official version of the formation of the Moon, the equatorial speed of the Earth was 6 times higher than now (the angular momentum of the Moon is tens of times greater than that of the Earth, which gives the length of the Earth’s day at the time of the formation of the Moon about 4 hours). This allowed the authors of the hypothesis to significantly reduce the mass of the impactor, and, accordingly, its size to a Mars-like level. If 4.6 billion years ago the Moon's orbit was polar, then the advantages of the Earth's high equatorial speed disappear, and again the need arises for a significant increase in the mass of the impactor. To avoid this, the authors of the hypothesis significantly increase the initial tilt of the Earth's rotation axis, as a result of which the ejection of matter occurs in the equatorial plane, and the Moon ends up in a high polar orbit. True, it remains unclear what subsequently forced the Earth to change the angle of its rotation axis so radically.

However, the problems with the polar orbit of the Moon do not end there. Such an orbit also assumes the Moon’s own rotation immediately after its formation around a completely different axis than the one around which it now rotates! The Moon must have rotated almost perpendicular to its modern axis of rotation. What forces caused it to stop rotating around this axis? Even if we assume that in the future it changed the inclination of the rotation axis due to tidal friction, then, all the same, there should have been a significant inclination of the Moon’s rotation axis relative to the modern orbit of the Moon, which does not exist, otherwise we would have the opportunity to observe the Moon from all sides .

We are accustomed to the fact that the Moon is a satellite of the Earth. However, will it always be like this? According to the general director of the Central Scientific Research Institute of Mechanical Engineering, Gennady Raikunov, our night star may sooner or later leave the earth's orbit and become an independent planet. In this case, the Earth will turn into a lifeless desert...

Raikunov assures that the Moon may well repeat the fate of Mercury, which is supposed to have once been a satellite of Venus, but then “flew away” from it. After this, the conditions on Venus became unsuitable for life, despite the fact that it is an Earth-like planet.

“The Moon also moves away from the Earth every year, and someday, apparently, if reverse processes do not happen, it must leave the Earth,” the director of TsNIIMash made such a statement at the ongoing air show in Bourges. “Won’t it turn out that the Earth will go along the path of Venus, when conditions are formed that are unsuitable for existing life forms - an aggressive atmosphere, enormous pressure, the greenhouse effect, etc.?”

According to the scientist, space research is currently being carried out to help find out whether living conditions on our planet will change if it loses its natural satellite, and how the worst case scenario can be prevented.

Gennady Raikunov has long been concerned about the fate of the Moon. Earlier, he called the satellite the “seventh continent” and said that it was necessary to create a permanently functioning base on it, whose employees would be engaged in research and use of the resources of this celestial body.

The Moon is now moving around the Earth in a nearly elliptical orbit, counterclockwise (as viewed from the North Pole) at an average speed of 1.02 kilometers per second. In fact, the movement of our natural satellite is a rather complex process, which is influenced by various disturbances caused by the attraction of the Sun, planets and the oblate shape of the Earth. How likely is the scenario proposed by Raikunov?

Sergei Popov, a researcher at the Sternberg State Astronomical Institute of Moscow State University (SAI), confirmed that the Moon is indeed moving away from the Earth, but very slowly - the speed of removal is about 38 millimeters per year. “Over a few billion years, the Moon’s orbital period will simply increase by one and a half times, and that’s all,” Popov said. “The Moon cannot completely leave. It has nowhere to get the energy to escape.”

According to Surdin, under the influence of solar tides (the movement of water masses caused by the attraction not of the Moon, but of the Sun. - Ed. ) the rotation speed of our planet is gradually decreasing, and the speed of the satellite’s removal will gradually decrease. In about five billion years, the radius of the lunar orbit will reach its maximum value - 463 thousand kilometers, and the length of the earth's day will increase to 870 hours.

“The statement “The Moon can leave the Earth’s orbit and turn into a planet” is incorrect,” Vladimir Surdin commented on the words of his colleague Raikunov. “The solar tides will continue to slow down the Earth. But now the Moon will outstrip the Earth’s rotation, and tidal friction will begin to slow down its movement. In As a result, the Moon will begin to approach the Earth, albeit very slowly, since the strength of the solar tides is small."

But even if we imagine that the Moon is no longer a satellite of the Earth, this will not turn our planet into a semblance of lifeless Venus, scientists say. Thus, the head of the laboratory of comparative planetology at the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, Alexander Bazilevsky, commented: “The departure of the Moon will have little effect on the conditions on the Earth’s surface. There will be no ebbs and flows (they are mainly lunar), and the nights will be moonless. We will survive.”

Raikunov’s colleagues do not entirely agree with his statement that Mercury was once a satellite of Venus. “Calculations have shown that this is possible, which, however, does not prove that it was so,” Bazilevsky said. In addition, he believes, the development of the Earth and Venus cannot follow the same paths, since in the Venusian atmosphere there is an increased content of the heavy isotope of hydrogen - deuterium.

“This may be due to the fact that Venus once had a relatively large amount of water. When water in the upper layers of the atmosphere decomposed into hydrogen and oxygen, the light isotope of hydrogen escaped into space faster than the heavy one, and the observed anomaly resulted,” says the scientist. “But It’s not a fact that there was liquid water on the surface of Venus and not steam in the atmosphere, that is, it’s not a fact that it wasn’t as hot there as it is now.”

Origin of the Moon. It was a long time ago. So long ago that it’s hard to even imagine. To determine the number of years that have passed, you would have to write a number with nine zeros.

At that time, the Moon and Earth were one. The huge molten ball made one revolution around its axis in just four hours. The centrifugal force at the equator and the tides that the Sun caused in this ball elongated in its direction came into resonance with the ball’s own vibration and tore off a piece from it, which eventually became the Moon.

At the site of this detachment, the greatest depression on Earth has remained to this day, now occupied by the Pacific Ocean.

This is what the famous English astronomer believed George Darwin(1845–1912), son Charles Darwin(1809–1882). And, despite the fact that his hypothesis about the origin of the Moon is not now generally accepted, observations and calculations show that two billion years ago our natural satellite was at a very close distance from the Earth.

But our planet and the Moon are 4.5 billion years old (this is also evidenced by the age of the oldest lunar rocks). If the Earth and Moon had appeared together at that moment, they would have moved significantly further away from each other than they do now.

What happened during the first half of their existence? Where was the moon? Maybe they formed together, but earlier the Moon was moving away from our planet less intensely than it is now? Or maybe somewhere it revolved around the Sun as a planet, and then, due to some circumstances, was captured into low-Earth orbit and became a satellite of the Earth?

These questions, together with Darwin’s version, reflect three hypotheses of the origin of the Moon, which have been quite popular in science for a long time: 1) separation from the Earth, 2) its formation at the same time as our planet, and 3) capture of a ready-made satellite.

In 1975, another, catastrophic hypothesis appeared, which connects the origin of the Moon with the collision of the Earth with a large cosmic body comparable in mass to the planet Mars.

Let us briefly dwell on these hypotheses and analyze them, taking into account the main physical characteristics of our natural satellite. Along with its size and mass, the most important parameter of a planet is its average density, which allows us to determine its chemical composition. For the Moon it is 3.3 g/cm 3 (for the Earth 5.5 g/cm 3). The lunar density is close to the density of the Earth mantle, lithosphere The Earth, its rocky shell, which occupies 70% of the planet’s mass - from the iron-nickel core (half the Earth’s radius) to the surface. As for the Moon, it has a very small iron-nickel core, only 2–3% by mass (Fig. 2).

1) It would seem that if the lunar substance is similar to the substance of the earth’s mantle, then this is a convincing argument that the Moon at one time broke away from the Earth. Based on this, the hypothesis of the separation of the Moon from the Earth (jokingly called “daughter”) was very popular at one time and was generally accepted at the beginning of the twentieth century.

In favor of this version of the origin of the Moon, a similar ratio of oxygen isotopes 16 O, 17 O and 18 O was obtained relatively recently in lunar rocks and rocks of the Earth’s mantle. However, in addition to the similarity of the lunar substance with the substance of the earth's mantle, there are also significant differences.

Indeed, the so-called volatile (low-melting) and siderophilic There are significantly fewer elements in lunar rocks than in terrestrial rocks. In addition, for centrifugal force and tide to tear off a piece of the globe, a period of its rotation of at least 2 hours is required so that the half-period of rotation would resonate with the period of natural oscillations of this ball (about an hour), and the mass of the torn piece, as calculations show, should make up 10–20% of the Earth's mass.

In fact, the mass of the Moon is 81 times less than the mass of the Earth, and the mass of the mantle material in the volume of the Pacific Trench would be only a small fraction of the mass of the Moon. In addition, the age of the Pacific Ocean is estimated to be about 500 million years, while the age of the Moon and Earth is 4.5 billion years. Thus, the hypothesis of the separation of the Moon from the Earth does not withstand the strict criticism of specialists.

2) If the Moon and Earth were simultaneously formed from the same ring protoplanetary clouds (jokingly - a “sister” hypothesis), this easily explains the identity of the oxygen-isotopic ratio of their substance, but does not agree with its difference in density and with a deficiency of iron and siderophile and volatile elements.

One of the authors of the impact hypothesis V. Hartman wrote: " It is difficult to imagine that two celestial bodies grow side by side from the same orbital layer of matter, but at the same time one of them takes all the iron, while the other remains practically without it».

3) Legends of some peoples (for example, Dogon, West Africa) tell about the time when there was no Moon in the sky, and about the appearance of a new star. Contrary to this, the results of computer simulations of the capture of the Moon by the Earth (jokingly called the “marital” hypothesis) show that the likelihood of such a capture is very small.

Much more likely is a collision or ejection of the proto-moon by Earth's gravity beyond the Earth's orbit. The Moon's low density and small iron core could be explained by the assumption that it formed outside the terrestrial planets (Mercury, Venus, Earth and Mars), but in this case it is impossible to explain the deficiency of volatile elements, which are abundant there. It is difficult to find a place in the solar system with both a low content of one and the other.

4) One of the main goals of the American space missions to the Moon in the 1960s and 70s was to find evidence in favor of one or another of the three above

named hypotheses of the origin of the Moon. During the Apollo program, 385 kg of lunar material was delivered to Earth. Already his first analyzes revealed significant disagreements between the results obtained and all three hypotheses.

Most experts believe that the currently available facts testify in favor of a hypothesis that did not yet exist before the flight of spacecraft to the Moon - the hypothesis of a catastrophic collision. To explain the iron deficiency on the Moon, we had to make the assumption that at the time of the collision (4.5 billion years ago) gravitational pull had already occurred in the depths of both bodies. differentiation substances when heavy chemical elements sank down and formed the core, and lighter ones floated to the surface and formed the mantle, crust, hydrosphere And atmosphere.

This assumption has no geological justification, but, nevertheless, the catastrophic hypothesis of the origin of the Moon is now considered the most acceptable.

Evolution of the Earth-Moon system. Let us now consider how the Earth and the Moon have coexisted since fate brought them together. The main driving force of their interaction was and remains tidal friction. The tidal force on Earth is the resultant of two forces: the attraction of the Moon or Sun and the centrifugal force of the Earth's rotation around the common Earth-Moon center (called barycenter system and is located in the Earth’s mantle at a depth of 1700 km) or Earth-Sun (Fig. 3).

At the center of the Earth these forces balance each other, but at the point A attraction prevails, and at the point IN- centrifugal force. These are the points of maximum tide on the surface of the planet.

Due to the daily rotation of the Earth in places of tidal protrusions A And IN visits the same point on the earth's surface twice a day. Residents of coasts and islands are well aware of the tides, when the water rises and falls twice a day. In some places, due to a combination of circumstances (current direction, narrow bays and river mouths), the height of the sea tide reaches 10 m, and, for example, at the mouth of the Sevrn River or in the Bay of Fundy (England) it reaches 16 m.

But tides are not only observed in the ocean. The solid Earth, attracted by the Moon and the Sun, behaves like a spring and is deformed, i.e. the solid body of the Earth also experiences a tide. These phenomena are called earth tides . The highest height of the earth's tide at the equator is 55 cm, and at the latitude of Kiev - about 40 cm. It is to this height that we rise and fall twice a day, slowly and continuously, 6 hours up, 6 hours down.

Since there is no fixed reference point against which such movements could be observed, this phenomenon remains unknown to many. But high-precision instruments (gravimeters, tiltmeters) reliably record the earth's tides. In this case, the observation point moves away from the center of the Earth by only one ten-millionth of the Earth’s radius (Earth’s radius ≈ 6400 km).

Gravimeters record this movement as a decrease in gravity, because gravity decreases with increasing distance from the center of the Earth.

During tides, both in the ocean and in the earth's firmament, due to the viscosity of the substance and the friction of water along the bottom and shores of reservoirs, part of the energy of the rotational movement of the Earth is dissipated in the form of heat. Tidal protrusions from friction A And IN do not have time to fall quickly and are carried forward by the Earth in the course of its rotation (Fig. 3). Moon's attraction to the ledge A(more than protrusion IN) slows down the daily rotation of the Earth, and gravity protrudes A Moon (more than a ledge IN) spins our natural satellite in orbit.

Due to the first effect, the Earth slows down its rotation around its axis, and due to the second, the Moon moves away from the Earth. True, the figures that describe the increase in the day and the lengthening of the radius of the Lunar orbit are extremely small: the day increases by 0.002 s per 100 years, and the Moon moves away from the Earth by 3 cm/year. Laser determinations of the distance to the Moon, carried out in 1969–2001 using corner reflectors installed on the Moon, give a value of 3.81 ± 0.07 cm/year for increasing the radius of the lunar orbit.

These seemingly insignificant quantities cause significant changes on a cosmological time scale. In addition, when the Moon was closer to our planet, their interaction was more intense: the days on Earth increased more significantly, and our natural satellite moved away faster (Fig. 4).

This is confirmed not only by the results of astronomical observations. There are also paleontological, fossil evidence suggests that days on Earth were previously shorter.

During the growth process, some corals and mollusks, as well as algae, form not only annual rings, as is the case with trees, but also daily rings. Using these data, you can calculate the number of days throughout the year. Modern organisms produce 365 diurnal rings in one annual, while fossils produce more.

Thus, organisms living in Devonian period Paleozoic era (400 million years ago, when the first vertebrates—fish) just appeared—accumulated 400 daily layers per year, and those who lived in Proterozoic(670 million years ago) – 435.

Astronomers do not know the reasons that, throughout the history of the Earth, could significantly influence the length of the year - the period of the Earth’s revolution around the Sun. Thus, the year did not change noticeably during this long period of time, only the length of the day changed.

It is easy to calculate from these observations that in Devon the day lasted 22 modern hours, and 670 million years ago ( Proterozoic era) were equal to only 20 modern hours. Previously, the days were even shorter, but there is no paleontological evidence of this at this time.

According to the calculations of astronomers studying the origin of planets and the past of the solar system, the initial period of rotation of the Earth around its axis (day) was 10 hours. The day on the giant planets Jupiter and Saturn is close to this value, the enormous inertia of which and numerous satellites that act inconsistently contributed to the preservation of their primary daily rotation. Uranus and Neptune have slowed down their axial rotation slightly: a day on Uranus lasts about 17 hours, and on Neptune - about 16.

The Earth will slow down its rotation until the day is equal to the period of revolution of the Moon around our planet. Their total rotation period will then be 47 current days. The Earth and the Moon will rotate facing each other with tidal protrusions, on the same side, as if connected by a bridge, like a dumbbell.

By the way, the Moon used to rotate around its axis much faster, and then it was possible to admire not only one side of our satellite. However, the tides that Earth’s gravity causes on the Moon are significantly greater than those caused by the Moon on Earth, since the mass of our planet is 81 times greater, and the force of gravity on the surface of our satellite is 6 times less.

Lunar tides have long slowed down the rotation of the Moon, and its tidal protrusion is now always directed towards the Earth. Such a rotation of the satellite around the central planet and around its axis, when one side of the satellite is always facing the planet, and the period of rotation around the central body and around the axis coincide, is called synchronous.

Surprising in this regard is the foresight of the famous German philosopher Immanuel Kant(1724–1804) at a time when there was no scientific data on this issue yet.

In his work “General History and Theory of Heaven” in 1754, he wrote: “ If the Earth is steadily approaching the moment of suspension of its rotational motion, then the period during which this change occurs will be completed when the surface of the Earth is at rest in relation to the Moon, that is, when the Earth begins to rotate around its axis at that the very time at which the Moon makes a revolution around the Earth, therefore, when the Earth will always face the same side to the Moon. The reason for this state is the movement of a liquid substance covering part of its surface only to a very small depth. This immediately shows us the reason why the Moon, in its rotation around the Earth, always faces it with the same side».

It is curious that the height of the tidal ridge on the Moon is now 2 km. This is 100 times more than the tide that our planet would cause at its current distance from the Moon. Obviously, at the time when such a high tide formed, our natural satellite was significantly closer to the Earth. For such a huge tide, the distance would not be 380 thousand km, as it is now, but 5 times less.

The moon then had molten interiors, which, cooling, hardened and retained this huge tidal protrusion in its body, as a memory of that long-ago era. This also indicates that the Moon began to rotate synchronously with its revolution around the Earth already when the distance between them was only 75 thousand km. This happened less than two billion years ago.

Let us now turn to the Earth. As mentioned, the length of the day and month in the distant future will be equal to each other and will be 47 current days. For this process to be completed, it will take a long time - about 50 billion years. Let us recall that the age of the Earth and planets is about 4.5 billion years.

This would have stabilized the process of joint rotation of the Earth and the Moon, if not for the Sun. The fact is that solar tides also slow down the daily rotation of the Earth. Although they are two times smaller than the lunar ones, they do not change over time.

And if the braking effect of the Moon on the daily rotation of the Earth stops at the moment when the day and month become equal, then the influence of the Sun on this process will continue. As a result, the day on Earth will continue to increase, and as a result, our planet will rotate around its axis more slowly than the Moon around it.

In this situation, the tides caused by the Moon on Earth will affect its rotation in the direction opposite to the previously considered case, i.e. the Earth will accelerate in its rotation, and the Moon will slow down in orbit. The reverse process will begin: the day will begin to decrease, and the Moon will begin to approach the Earth, and this will continue until the Moon approaches the so-called Roche limit.

For a satellite with zero strength (liquid, individual fragments of a solid body), this limit is approximately 1.5 radii from the surface of the central planet. Here, the centrifugal force of the Moon's revolution and the gravity of the planet, acting in opposite directions (their resultant is the tidal force), will prevail over the force of gravity on the surface of the satellite and tear it apart. A ring of many small satellites forms around the Earth.

Such examples are known in our solar system: the giant planets Jupiter, Saturn, Uranus and Neptune all have rings near the surface, although the origin of these rings is not necessarily related to tides. Obviously, the satellites of these planets could not form near the Roche limit.

In the Earth-Moon system, tidal processes occur extremely slowly. It has already been mentioned: for a day on Earth to become equal to the length of a month, it takes about 50 billion years. And for the Moon to return back to the Earth, it takes too long, even in cosmological scale.

In the Solar System there are many examples of the effective effect of tides on the rotational motion of celestial bodies. The planets Mercury and Venus have slowed down significantly as a result of the influence of solar tides on them, and their day (period of rotation around their axis) lasts 58.6 and 243 Earth days, respectively.

The synchronous rotation is followed by the small satellites of Mars Phobos and Deimos. On the large satellite Io, closest to Jupiter, the height of the tide, frozen during synchronous rotation, is 3 km. Only as a result of the satellite moving along an elongated (eccentric) orbit does this height change by 84 meters. Moreover, due to the deformation of the satellite’s body, 10 times more heat is released than on the Moon from the decay of radioactive substances. As a result, Io has volcanoes that are more powerful than those on Earth (Fig. 5).

The large moons of Jupiter, Saturn and Uranus, and Neptune's largest moon Triton, rotate synchronously. Pluto and Charon are prime examples of tidal locking. In this system, not only Charon rotates synchronously, but Pluto also faces Charon with one side all the time, they rotate with a period of 6.4 days, as if connected by a jumper.

As a result, we emphasize that tidal friction is an important factor in the evolution of cosmic systems, not only planets and satellites, but also multiple star clusters and even galaxies.

Dictionary
Atmosphere(from the Greek ατμος - steam and σφαϊρα - ball) - the air shell of the Earth.
Hydrosphere(from the Greek υδωρ - water and σφαϊρα - ball) - the water shell of the Earth.
Gravimeter(from Latin gravis - heavy and Greek μετρεω - to measure) - a device for measuring the magnitude of gravity.
Devonian(from the name of the English county of Devonshire) – fourth period Paleozoic era from 419 to 359 million years ago.
Differentiation(from Latin differentia - difference) - division of the whole into qualitatively different parts.
Cosmological(from the Greek κοσμοζ - space, universe) - everything that relates to the Universe.
Climax(from Latin culmen - peak) - here is the maximum height of the luminary.
Lithosphere(from the Greek λιτος - stone and σφαϊρα - ball) - the stone shell of the Earth.
Mantle(from the Greek μαντιον - cover) - the rocky shell of the Earth from the core to the earth's crust.
Paleozoic(from the Greek παλαιος - ancient ςωη - life) - the third geological era in the history of the Earth from 541 to 251 million years ago.
Paleontology(from the Greek παλαιος - ancient, οντος - essence and λογος - teaching) - the science of the fossil remains of living organisms.
Proterozoic(from the Greek προτερος - previous) - the second geological era in the history of the Earth from 2500 to 541 million years ago.
Protoplanetary, protosolar(from the Greek πρωτος - first) - the primary nebula from which the Sun and planets were formed at one time.
Siderophiles(from the Greek σίδηρος - iron and φίλεω - love) - chemical elements adjacent to iron in the periodic table.
Synchronous(from the Greek συγχρονο - simultaneously) - coincidence in the period of oscillation of two or more processes.
Tectonics(from the Greek τεκτονικη - construction) - the science of the structure and movements of the earth's crust and the masses located under it (lithospheric plates).

I.A. Dychko, candidate of physical and mathematical sciences, Poltava

The influence of the Moon on Earth is difficult to overestimate. In particular, it keeps the Earth at an inclination of 66 degrees from the orbital plane. Thanks to this, the climate on most of our planet is quite good.

It is impossible to predict which side the Earth will turn to the Sun if the Moon leaves to wander through space. Presumably, it will literally lie on its side. Glaciers will melt, deserts will freeze, and the ebb and flow of tides will be forgotten. To understand how this threatens all life on the planet, just watch any apocalyptic film.

Meanwhile, Russian ufologists have already taken the version with the removal of the Moon in pencil and put forward a theory in their own style.

Ufologists have long considered the Moon as the closest base of alien civilizations to us,” ufologist Yuri Senkin told Vecherka. - The fact that telescopes, lunar rovers and people who have visited the Moon several times did not find them there can be explained simply - we examined only one side of the satellite. No one has studied the reverse side.

It is difficult to say what caused the Moon to move away, but it is possible that this is the work of aliens - or whatever they have instead of hands. And even if this is so, it is unlikely that this was done in order to harm our civilization. Alien races may pursue completely different goals. The Moon, for example, is rich in resources, including those that are in terrible short supply on Earth.

The Vecherka journalists were not at all inspired by the prospect of losing the Earth’s satellite: firstly, it would be quite boring at night without it, and secondly, they want to live some more. Therefore, we immediately turned to the P. K. Sternberg State Astronomical Institute for clarification.

The head of the Department of the Moon and Planets, Doctor of Physical and Mathematical Sciences Vladislav Shevchenko laughed for a long time after listening to the question. He asked me to repeat it. And he laughed again without stopping.

Oh storytellers! - he said, catching his breath. - But seriously, the Moon is indeed moving away from the Earth, but we must understand that this has been happening for four billion years, ever since the Moon itself was formed.

According to Shevchenko, the removal of the Earth's satellite is a completely natural physical phenomenon - we remember the school curriculum in physics - called inertia. Imagine that you are riding on a carousel. Spinning faster and faster, you feel yourself starting to lean in the direction opposite to the axis of the carousel. And if you don't grab onto something, you could simply be thrown out. But the Moon has nothing to cling to. The speed with which it rotates around the Earth sets such inertia that the Earth’s gravitational field is powerless to hold this ball. And you need to understand that gravity affects our satellite less and less as it moves away.

According to calculations, the Moon is moving away from the Earth by about 3.8 centimeters per year, continues Vladislav Shevchenko. - Now the distance to it is 384 thousand kilometers. And when the Moon was just forming, it was about 60 thousand kilometers. Just a stone's throw away! It took about four billion years for this distance to increase sixfold.

And it will take several more million years for the Moon to move away, ceasing to completely cover the Sun during an eclipse. Therefore, it is too early to worry about this. Just know: when this happens, “Evening Moscow” will notify you personally first.

There are several versions of the origin of the Moon, but in recent decades scientists have been leaning toward the theory of a giant collision. This happened about 4.6 billion years ago: the hypothetical planet Theia collided with the Earth tangentially, tearing out a huge piece from our long-suffering planet. The Earth immediately boiled, almost turning inside out, and the part of it that Theia tore out was captured by the Earth’s gravitational field, so that billions of years later we could lift our heads and say: “The moon is awesome today!”

INTERESTING FACT

Residents of the southern hemisphere see the Moon the other way around: for them it grows on the left, and decreases to the right.

The first artificial satellite of the Sun was the Soviet station Luna-1 in 1959. Due to an error in the calculations, it missed the Earth's satellite at the second cosmic speed.

The smartphone your neighbor boy is carrying is many times more powerful than the computer that controlled the landing of astronauts on the moon.