Distance from the earth to the moon. Distance from earth to moon
Since time immemorial, the Moon has been a constant satellite of our planet and the closest celestial body to it. Naturally, people always wanted to visit there. But how far is it to fly there and how far is it?
The distance from the Earth to the Moon is theoretically measured from the center of the Moon to the center of the Earth. It is impossible to measure this distance using conventional methods used in everyday life. Therefore, the distance to the earth's satellite was calculated using trigonometric formulas.
Similar to the Sun, the Moon experiences constant movement in the earth's sky near the ecliptic. However, this movement is significantly different from the movement of the Sun. So the planes of the orbits of the Sun and Moon differ by 5 degrees. It would seem that, as a result of this, the trajectory of the Moon in the earth’s sky should be similar in general terms to the ecliptic, differing from it only by a shift of 5 degrees:
In this, the movement of the Moon resembles the movement of the Sun - from west to east, in the opposite direction to the daily rotation of the Earth. But in addition, the Moon moves across the earth's sky much faster than the Sun. This is due to the fact that the Earth revolves around the Sun in approximately 365 days (Earth year), and the Moon revolves around the Earth in only 29 days (lunar month). This difference became the impetus for dividing the ecliptic into 12 zodiacal constellations (in one month the Sun moves along the ecliptic by 30 degrees). During the lunar month, a complete change in the phases of the Moon occurs:
In addition to the trajectory of the Moon, there is also the factor of a very elongated orbit. The eccentricity of the Moon's orbit is 0.05 (for comparison, for the Earth this parameter is 0.017). The difference from the circular orbit of the Moon causes the apparent diameter of the Moon to constantly change from 29 to 32 arcminutes.
In one day, the Moon shifts relative to the stars by 13 degrees, and in an hour by about 0.5 degrees. Modern astronomers often use lunar occultations to estimate the angular diameters of stars near the ecliptic.
What determines the movement of the Moon?
An important point in the theory of the movement of the Moon is the fact that the Moon’s orbit in outer space is not constant and stable. Due to the relatively small mass of the Moon, it is subject to constant disturbances from more massive objects in the Solar System (primarily the Sun and Moon). In addition, the orbit of the Moon is influenced by the oblateness of the Sun and the gravitational fields of other planets in the Solar System. As a result, the eccentricity of the Moon's orbit fluctuates between 0.04 and 0.07 with a period of 9 years. The consequence of these changes was a phenomenon called a supermoon. A supermoon is an astronomical phenomenon in which the full moon is several times larger in angular size than normal. So during the full moon on November 14, 2016, the Moon was at its closest distance since 1948. In 1948, the Moon was 50 km closer than in 2016.
In addition, fluctuations in the inclination of the lunar orbit to the ecliptic are observed: by approximately 18 arc minutes every 19 years.
What is equal to
Spacecraft will have to spend a lot of time flying to the earth's satellite. You cannot fly to the Moon in a straight line - the planet will move in orbit away from the destination point, and the path will have to be adjusted. At a second escape velocity of 11 km/s (40,000 km/h), the flight will theoretically take about 10 hours, but in reality it will take longer. This is because the ship at the start gradually increases its speed in the atmosphere, bringing it to a value of 11 km/s, in order to escape from the Earth’s gravitational field. Then the ship will have to slow down as it approaches the Moon. By the way, this speed is the maximum that modern spacecraft have managed to achieve.
The notorious American flight to the Moon in 1969, according to official data, took 76 hours. NASA's New Horizons was the fastest to reach the Moon in 8 hours and 35 minutes. True, he did not land on the planetoid, but flew past - he had a different mission.
Light from the Earth will reach our satellite very quickly - in 1.255 seconds. But flights at light speeds are still in the realm of science fiction.
You can try to imagine the path to the Moon in familiar terms. On foot at a speed of 5 km/h, the journey to the Moon will take about nine years. If you drive a car at a speed of 100 km/h, it will take 160 days to get to the earth’s satellite. If airplanes flew to the moon, the flight to it would last about 20 days.
How in ancient Greece astronomers calculated the distance to the Moon
The Moon became the first celestial body to which it was possible to calculate the distance from the Earth. It is believed that astronomers in Ancient Greece were the first to do this.
People have been trying to measure the distance to the Moon since time immemorial - Aristarchus of Samos was the first to try. He estimated the angle between the Moon and the Sun to be 87 degrees, so it turned out that the Moon is 20 times closer to the Sun (the cosine of an angle of 87 degrees is 1/20). The angle measurement error resulted in a 20-fold error; today it is known that this ratio is actually 1 to 400 (the angle is approximately 89.8 degrees). The large error was caused by the difficulty of estimating the exact angular distance between the Sun and Moon using the primitive astronomical instruments of the ancient world. Regular solar eclipses by this time had already allowed ancient Greek astronomers to conclude that the angular diameters of the Moon and the Sun were approximately the same. In this regard, Aristarchus concluded that the Moon is 20 times smaller than the Sun (in fact, about 400 times).
To calculate the sizes of the Sun and Moon relative to the Earth, Aristarchus used a different method. We are talking about observations of lunar eclipses. By this time, ancient astronomers had already guessed the reasons for these phenomena: the Moon was eclipsed by the Earth's shadow.
The diagram above clearly shows that the difference in distances from the Earth to the Sun and to the Moon is proportional to the difference between the radii of the Earth and the Sun and the radii of the Earth and its shadow to the distance of the Moon. At the time of Aristarchus, it was already possible to estimate that the radius of the Moon is approximately 15 arc minutes, and the radius of the earth's shadow is 40 arc minutes. That is, the size of the Moon was approximately 3 times smaller than the size of the Earth. From here, knowing the angular radius of the Moon, one could easily estimate that the Moon is located about 40 Earth diameters from the Earth. The ancient Greeks could only approximately estimate the size of the Earth. Thus, Eratosthenes of Cyrene (276 - 195 BC), based on differences in the maximum height of the Sun above the horizon in Aswan and Alexandria during the summer solstice, determined that the radius of the Earth is close to 6287 km (modern value 6371 km). If we substitute this value into Aristarchus’ estimate of the distance to the Moon, it will correspond to approximately 502 thousand km (the modern value of the average distance from the Earth to the Moon is 384 thousand km).
A little later, a mathematician and astronomer of the 2nd century BC. e. Hipparchus of Nicaea calculated that the distance to the earth's satellite is 60 times greater than the radius of our planet. His calculations were based on observations of the movement of the Moon and its periodic eclipses.
Since at the moment of the eclipse the Sun and the Moon will have the same angular dimensions, using the rules of similarity of triangles one can find the ratio of the distances to the Sun and to the Moon. This difference is 400 times. Applying these rules again, only in relation to the diameters of the Moon and the Earth, Hipparchus calculated that the diameter of the Earth is 2.5 times greater than the diameter of the Moon. That is, R l = R z /2.5.
At an angle of 1′, you can observe an object whose dimensions are 3,483 times smaller than the distance to it - this information was known to everyone in the time of Hipparchus. That is, with the observed radius of the Moon being 15′, it will be 15 times closer to the observer. Those. the ratio of the distance to the Moon to its radius will be equal to 3483/15 = 232 or S l = 232R l.
Accordingly, the distance to the Moon is 232 * R з /2.5 = 60 radii of the Earth. This turns out to be 6,371*60=382,260 km. The most interesting thing is that measurements made using modern instruments confirmed the rightness of the ancient scientist.
Now measuring the distance to the Moon is carried out using laser instruments that allow it to be measured with an accuracy of several centimeters. In this case, measurements take place in a very short time - no more than 2 seconds, during which the Moon moves away in orbit approximately 50 meters from the point where the laser pulse was sent.
The evolution of methods for measuring the distance to the Moon
Only with the invention of the telescope were astronomers able to obtain more or less accurate values for the parameters of the Moon’s orbit and the correspondence of its size to the size of the Earth.
A more accurate method of measuring the distance to the Moon appeared in connection with the development of radar. The first radar survey of the Moon was carried out in 1946 in the USA and Great Britain. Radar made it possible to measure the distance to the Moon with an accuracy of several kilometers.
Laser ranging has become an even more accurate method for measuring the distance to the Moon. To implement it, several corner reflectors were installed on the Moon in the 1960s. It is interesting to note that the first experiments on laser ranging were carried out even before the installation of corner reflectors on the surface of the Moon. In 1962-1963, several experiments were carried out at the Crimean Observatory of the USSR on laser ranging of individual lunar craters using telescopes with a diameter of 0.3 to 2.6 meters. These experiments were able to determine the distance to the lunar surface with an accuracy of several hundred meters. In 1969-1972, Apollo astronauts delivered three corner reflectors to the surface of our satellite. Among them, the most advanced was the reflector of the Apollo 15 mission, since it consisted of 300 prisms, while the other two (Apollo 11 and Apollo 14 missions) only consisted of one hundred prisms each.
In addition, in 1970 and 1973, the USSR delivered two more French corner reflectors to the lunar surface on board the Lunokhod-1 and Lunokhod-2 self-propelled vehicles, each of which consisted of 14 prisms. The use of the first of these reflectors has an extraordinary history. During the first 6 months of operation of the lunar rover with the reflector, it was possible to conduct about 20 laser ranging sessions. However, then, due to the unfortunate position of the lunar rover, it was not possible to use the reflector until 2010. Only photographs of the new LRO apparatus helped to clarify the position of the lunar rover with the reflector, and thereby resume work sessions with it.
In the USSR, the largest number of laser ranging sessions were carried out at the 2.6-meter telescope of the Crimean Observatory. Between 1976 and 1983, 1,400 measurements were taken with this telescope with an error of 25 centimeters, then observations were stopped due to the curtailment of the Soviet lunar program.
In total, from 1970 to 2010, approximately 17 thousand high-precision laser ranging sessions were carried out in the world. Most of them were associated with the Apollo 15 corner reflector (as mentioned above, it is the most advanced - with a record number of prisms):
Of the 40 observatories capable of performing laser ranging on the Moon, only a few can perform high-precision measurements:
Most of the ultra-precise measurements were made on a 2-meter telescope at the Mac Donald Observatory in Texas:
At the same time, the most accurate measurements are performed by the APOLLO instrument, which was installed on the 3.5-meter telescope at Apache Point Observatory in 2006. The accuracy of its measurements reaches one millimeter:
Evolution of the Moon and Earth system
The main goal of increasingly accurate measurements of the distance to the Moon is to attempt to gain a deeper understanding of the evolution of the Moon's orbit in the distant past and in the distant future. To date, astronomers have come to the conclusion that in the past the Moon was several times closer to the Earth, and also had a significantly shorter rotation period (that is, it was not tidally locked). This fact confirms the impact version of the formation of the Moon from the ejected material of the Earth, which prevails in our time. In addition, the tidal influence of the Moon causes the Earth's rotation speed around its axis to gradually slow down. The rate of this process is an increase in the Earth's day every year by 23 microseconds. In one year, the Moon moves away from the Earth by an average of 38 millimeters. It is estimated that if the Earth-Moon system survives the transformation of the Sun into a red giant, then after 50 billion years the Earth's day will be equal to the lunar month. As a result, the Moon and Earth will always face only one side towards each other, as is currently observed in the Pluto-Charon system. By this time, the Moon will move away to approximately 600 thousand kilometers, and the lunar month will increase to 47 days. In addition, it is assumed that the evaporation of the Earth's oceans in 2.3 billion years will lead to an acceleration of the process of removal of the Moon (Earth's tides significantly slow down the process).
In addition, calculations show that in the future the Moon will again begin to move closer to the Earth due to tidal interaction with each other. When approaching the Earth at 12 thousand km, the Moon will be torn apart by tidal forces, the debris of the Moon will form a ring similar to the known rings around the giant planets of the Solar System. Other known satellites of the Solar System will repeat this fate much earlier. So Phobos is given 20-40 million years, and Triton is about 2 billion years old.
Every year, the distance to the earth’s satellite increases by an average of 4 cm. The reasons are the movement of the planetoid in a spiral orbit and the gradually decreasing power of gravitational interaction between the Earth and the Moon.
Between the Earth and the Moon, it is theoretically possible to place all the planets of the solar system. If you add up the diameters of all the planets, including Pluto, you get a value of 382,100 km.
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 axis of rotation of the Earth (equatorial rotation) and the axis coinciding with the equatorial diameter of the Earth (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 .
Among all the moons of the solar system, the Earth's satellite is the most unique. Due to its close location to the Earth, as well as its size, the Moon gives our planet a stable and stable position in its eternal path in orbit. That is, it must be said that the Earth-Moon connection maintains its position in outer space in a more or less uniform rotation.
The formation of the Moon occurred approximately 4.5 billion years ago; according to the latest information from scientists, the Moon has become younger, shedding several million years. I must say that the history of the formation of the Moon is amazing. And the Earth’s satellite itself is extremely important for the existence of life on the planet. However, the Earth is also important for finding the Moon in its orbit.
As has been described more than once, billions of years ago, a cosmic object of no less smaller size crashes into a huge protoplanetary substance. It was then, from the molten mass - and this was the Earth - that huge pieces of matter were pulled out from the mass of the planet. Thrown into space, solid rocks are retained by the Earth's gravity.
Trying to escape the captivity of the Earth's gravity, but not having the strength to do this, they begin to gather into one large object. And under the influence of rotational forces, they turn into a ball. So, our Blue Planet has acquired an important component for the education and preservation of life.
It's amazing how precisely in time the space object arrived. No less surprising is the fact that someone’s hand placed both space objects in exactly the position and points where it was necessary for the flourishing of life on Earth.
Before the impact and formation of the Moon, our planet was not yet blue, and rotated 4 times faster than it does now. The Earth's axis stood at an inclination of 10 degrees, and the Earth's day at that time was very short - only 6 hours. And the angle of inclination affected the average temperature on Earth.
At this time, the Moon had not yet entered its current orbit, and was 12 thousand times closer to the Earth. Exerting a strong influence on the planet by powerful gravity. Soon, oceans began to form, and tidal friction began to slow the Earth's rotation. Over the course of 3 billion years, the formation of continents continued, and the speed of rotation of the planet continued to decrease, reaching 18 hours a day. After another half a billion years, the earth's day reaches 222 hours, and by adding seconds per year, it reaches 24 hours.
Why is the Moon so necessary for the Earth?
In fact, the Moon plays a very important role in the life of our planet. Firstly, it is necessary to note the gravitational force of the satellite, acting in conjunction with the Moon-Earth, our planet is in a stable orbit. And also, thanks to the Moon, our Blue Planet received an inclination angle of 23 degrees.
This degree of inclination can be called optimal; nature, as if specially took care of the comfort of human life on Earth. Indeed, thanks to this angle, the planet maintains a rather narrow range of temperatures. The sun's rays emitted by our luminary spread evenly across the globe, which creates good conditions for life on Earth. The stability of sunrises and sunsets is also associated with the Moon on Earth, supporting the changes of seasons that are familiar to us.
The Moon also has a strong influence on the Earth's water basins. The tides ebb and flow, all this passes under the watchful eye of our companion. The Moon also maintains a 4-meter rise in water level at the equator.
What will happen if the Moon moves away from the Earth? What does the Moon's distance threaten the Earth with?
It is impossible to say that the Moon is eternal above the Earth, and it may happen that the Earth’s satellite will occupy a more distant orbit relative to our planet. Or he will completely go on a free voyage through outer space. After all, as you know, the Moon, although by a small amount, is still moving away from the Earth.
Experts have been observing the Moon for almost half a century. The first American astronauts left a reflector on the satellite. This helped to accurately measure the distance between the Moon and the Earth. And on Earth, the satellite was monitored by modern technology.
And experts were able to answer the question of how far the Moon is moving away from the Earth. It turned out that this is about 4 centimeters per year - not such a small amount, considering that the distance is increasing every year. However, this is not a constant amount of removal. As we know, the distance between the satellite and our planet is not constant. Hence the amount of removal is inaccurate.
Periodically, as the Moon moves away, the Earth's axis changes its tilt angle by 2-3 degrees, in one direction or another from the axis. But even this small value of a couple of degrees responds to natural disasters on Earth. And if the chain connecting the Earth and the Moon is broken, then the two space objects, having lost their buoyant attractive force, will simply scatter in the vastness of space. Released as if from a sling.
About 100 thousand years ago, a slight change in the angle of the axis caused the sun's rays to fall differently. This led to an environmental catastrophe - where forests once flourished, sun-scorched wastelands formed. And as scientists suggest, it could have been the reason for the migration of the ancient inhabitants of the planet from Africa to the North. And in Europe and North America this led to the beginning of an ice age that lasted for millennia.
And if the Moon breaks the Moon-Earth chain, then a time of catastrophe will come on the planet. The truth is very fleeting. Huge masses of water, held by the Moon, will immediately break free and move deep into the planet with a powerful, unrestrained force. Sweeping away and destroying everything in its path, the first to experience this will be the residents of New York and Rio de Janeiro.
In addition, having lost lunar protection, the Earth may fall under the gravitational influence of another planet. And then there is no need to talk about stability on Earth. The planet will have a different inclination, and a changeable one at that. Which will lead to strong temperature changes. There will also be a redistribution of water basins; the level may increase by hundreds of meters.
However, the Earth also has an impact on the Moon, for example, the rotation of our satellite has slowed down to one revolution per month. The Earth also slows down its rotation, this is influenced by the enormous frictional forces of ocean waves on the bottom. In this case, the tidal wave shifts from the point directly facing the Moon.
Much in the life of our planet is connected with the Moon. A lot can be explained from a scientific point of view. However, at the moment no one is able to answer the curious question of who fine-tuned the celestial mechanism so precisely and placed all the cosmic bodies strictly in their places.
At any given moment in time, the Moon is no closer than 361,000 and no further than 403,000 kilometers from the Earth. The distance from the Moon to the Earth changes because the Moon rotates around the Earth not in a circle, but in an ellipse. In addition, the Moon is gradually moving away from the Earth by an average of 5 centimeters per year. People have been observing the gradually decreasing Moon for many centuries. The day may come when the Moon will break away from the Earth and fly into space, becoming an independent celestial body. But this may not happen. The balance of gravitational forces holds the Moon firmly in Earth orbit.
Why is the Moon moving away from the Earth?
Any moving body wants, by inertia, to continue its path in a straight line. A body moving in a circle tends to break away from the circle and fly tangentially to it. This tendency to break away from the axis of rotation is called centrifugal force. You feel the centrifugal force in a children's park, riding on a high-speed swing, or when driving a car, when it turns sharply and pushes you against the door.
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The word "centrifugal" means "running from the center." The moon also strives to follow this force, but it is held in orbit by the force of gravity. The Moon remains in orbit because the centrifugal force is balanced by the force of Earth's gravity. The closer to a planet its satellite is, the faster it rotates around it.
What is the reason? Any moving object has an angular momentum. The moment of a rotating body depends on the mass, speed and distance from the axis of rotation. The moment can be calculated by multiplying these three quantities together. Scientists have found that the moment of rotation of a given body does not change. Therefore, when an object approaches the axis of rotation, due to the law of conservation of momentum, it will rotate faster, since the mass in this equation cannot be changed arbitrarily.
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Previously, the Moon was much closer to Earth
This law is called the law of conservation of torque. The Moon makes one revolution around the Earth in about 27 days. But 2.8 billion years ago, the Moon, which is closer to us, orbited the Earth in 17 days. According to Clark Chapman, an astronomer at the Planetary Science Institute in Tucson, Arizona, the Moon was once even closer. At the time of the formation of the Earth's Moon 4.6 billion years ago, the Moon's orbital period was only 7 days. If then anyone could see the Moon, he would be amazed at the enormous size of the rising blood-red Moon.
The tide of the oceans pushes the moon away
Surprisingly, ocean tides are the very force that pushes the Moon away from the Earth. It happens like this. The gravitational force of the Moon acts on the waters of the Earth's oceans, attracting them. But the Earth does not stand still - it rotates around its axis. When the waters of the ocean swell, rushing towards the Moon, the Earth, with its rotation, seems to tear this mass of water away from it.
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The gravitational force of ocean water at the same time attracts the Moon, but not directly towards itself, but slightly forward, along the rotation of the globe. Therefore, the Moon receives an impulse directed not strictly along the radius of its orbit, but along a tangent to it. This phenomenon lengthens the Moon's orbit. As the lunar orbit imperceptibly (month after month) lengthens, the Moon moves away little by little from the Earth. The process is very slow and invisible to the eye, but it lasts millions of years and the overall result is very noticeable.
Probably, someday the Moon will be so far from the Earth that the force of the Earth's gravity will weaken, and the Moon will be able to set off on an independent flight around the Sun. However, scientists believe that such loneliness is unlikely to threaten the Moon. After all, tides also affect the Earth. The movement of masses of ocean water slows down the rotation of the Earth, so over 100 years the day increases by about half a minute. (Billions of years ago, the day lasted no more than six hours.)
Perhaps billions of years ago, the Moon orbited the Earth in just 7 days.
In the future, millions of years from now, the length of the day and the time of one revolution of the Moon around the Earth will still be equal, but will already be much longer than twenty-four hours. When the Moon moves far enough away from the Earth, their rotations will be more synchronous and the tides of the oceans will be exactly under the Moon. Then the gravity of the water will begin to have an attractive effect on the Moon, and it will stop moving away from the Earth. The process will reverse when the tidal regions are behind the Moon. The Moon's orbit will begin to shorten, and it will gradually approach the Earth. Perhaps the time will come when the huge Moon will appear in the sky again.
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- Maybe the Earth will slow down...
New research by scientist Matthew Huber from Purdue University has shown that over the past 50 million years, the Moon has begun to move away from the Earth at an increasing speed. The main reason for this phenomenon, according to the scientist, is the daily cycles of tides on Earth. This process helps to slow down the planet's rotation around its axis and move away from the Earth by approximately 3.8 centimeters per year. Based on these studies, it can be assumed that, provided that the Moon moves away at the same rate over the entire period of its existence, the age of the satellite should be approximately 1.5 billion years. However, it is quite obvious that these calculations are erroneous, since ongoing studies of lunar rocks have shown that the age of the Moon is much greater - almost 4.5 billion years, from which it follows that the formation of the Earth and our satellite occurred almost simultaneously.
Based on calculations by Matthew Hubert, it follows that every year the Moon moves away from the Earth by at least 4 cm
By studying the contours of continents and ocean floors that existed 50 million years ago, Matthew Huber and his colleagues created an accurate model of the tides of the distant past and calculated the gravitational interaction of the Earth and the Moon. It turned out that previously the energy of this interaction was half as much as it is now. Consequently, at this stage the Moon is moving away from the Earth at an increasing speed. There is no clear opinion about the causes of this phenomenon yet; one of the versions voiced by scientists is the likelihood of the influence of the expansion of the North Atlantic Ocean over the past centuries, as a result of which very large waves and high tides are formed, pushing the Moon away much more intensely.
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