We can observe the closest celestial body to our planet - the Moon - with the naked eye every evening. In ancient times, people came up with many legends associated with its pale glow, spots on its surface, etc.
But what do we even know about the Moon, its size, properties, etc.? In fact - not so little.
Comparison of the sizes of the Earth and the Moon
As you know, the Moon is our Earth. This means that the Moon is much smaller in mass and size than the Earth. Let's compare some of their sizes.
— The diameter of the Moon is on average 3,474 kilometers, while the diameter of the Earth is 12,742 kilometers. That is, the size of the Moon in diameter is only 3/11 of the Earth's diameter, it is 3.67 times smaller than the Earth's diameter.
— The surface of the Moon covers an area of 37.9 million square meters. km, and the area of the earth’s surface, as is known, is 510 million square meters. km. If we compare these indicators, it turns out that the surface area of the Moon is 13.5 times less than the Earth’s. Even if we compare the area of the Moon with the Earth's land, it turns out that the lunar surface occupies 4 times less area than the continents and islands of our planet.
— The volume occupied by the Moon is almost 50 times less than that of the Earth. In percentage terms, the Moon occupies only 2% of the Earth's volume. 
— The mass of the Moon is approximately 80 times less than the mass of our Earth. This means that the average density of the rocks that make up the Moon is much less than the density of Earth's rocks (about 60% of Earth's). Perhaps there are a lot of empty spaces inside the Moon.
— Gravity on the Moon is only 1.6 m/sq. sec, this is 6 times less than Earth’s gravity, which is, as we remember, 9.8 m/sq. sec. Therefore, on the Moon, every person can become a jumping champion.
Indeed, the Earth turns out to be much larger by all indicators. This is why the Moon is a satellite of our Earth, and not vice versa.
Some interesting facts about the Moon
— If you visually compare the sizes of the Moon, Earth and Sun, then you need to put next to each other an ordinary pea (Moon), a five-ruble coin (Earth) and a double-leaf door (Sun).
— A full lunar day is 29 Earth days, and the Moon around the Earth takes 27 of our days.
— The Moon does not have its own satellites.
— There is practically no atmosphere on the Moon that protects our Earth from the impacts of random meteorites. Therefore, the surface of the Moon is pitted with large and small craters, which were left after numerous collisions with celestial rocks of different sizes. 
— Due to the lack of an atmosphere, cosmic cold reigns on the surface of the Moon at night. Therefore, water there can only be in a frozen state. No living organism can withstand such conditions. If there was once on the Moon, now it is all gone.
Lunar exploration
The Moon is the most studied celestial body by people. To study it, researchers from different countries launched more than 100 different spacecraft. Most of them simply flew around the Moon and transmitted the information they received.
Back in 1959, the Soviet Union was the first in the world to launch the Luna-1 research apparatus, which flew close to the lunar surface and made the first direct measurements of its physical parameters. Then it was discovered that the Moon, unlike the Earth, does not have its own magnetic field.
The Soviet space program for launching automatic stations was quite successful, although there were also unsuccessful launches. However, even those lunar modules that failed to land on the Moon transmitted images of the surface, i.e. brought some benefit.
For the first time, in 1966, a Soviet spacecraft made a soft landing on the surface of the Moon and transmitted images from the surface of our satellite. The unmanned research complex Luna-16 was able to land on the surface of the Moon in 1970, take soil samples and return to Earth.
In addition, the USSR delivered two automatic Lunokhod modules to the lunar surface. The first one worked for about 10 months, covering more than 10 kilometers on the surface of the Moon, the second - about 4 months, covering 37 kilometers.
The United States launched 6 expeditions to the Moon with astronauts who reached the surface of the Moon and were able to return back. Before the start of the manned Apollo program, American researchers had several unsuccessful attempts at soft landing of automatic stations - the devices crashed when they collided with the lunar surface. 
All manned launches took place between 1969 and 1972, and without exception, all were successful. Today it is believed that the first person to set foot on the surface of the Moon was American astronaut Neil Armstrong in 1969.
The Earth's natural satellite is the Moon, a non-luminous body that reflects sunlight.
The study of the Moon began in 1959, when the Soviet Luna 2 spacecraft first landed on the Moon, and the Luna 3 spacecraft first took pictures of the far side of the Moon from space.
In 1966, Luna 9 landed on the Moon and established a solid soil structure.
The first people to walk on the moon were Americans Neil Armstrong and Edwin Aldrin. This happened on July 21, 1969. Soviet scientists for further study of the Moon preferred to use automatic vehicles - lunar rovers.
General characteristics of the Moon
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Average distance between the centers of the Earth and the Moon, km |
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The inclination of the orbit to the plane of its orbit |
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Average radius of the Moon, km |
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Equatorial radius, km |
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Polar radius, km |
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Inclination to the equator, degrees. |
The mass of the Moon is 1/81 the mass of the Earth. The position of the Moon in orbit corresponds to one or another phase (Fig. 1).
Rice. 1. Moon phases
Moon phases- various positions relative to the Sun - new moon, first quarter, full moon and last quarter. During a full moon, the illuminated disk of the Moon is visible, since the Sun and Moon are on opposite sides of the Earth. During the new moon, the Moon is on the side of the Sun, so the side of the Moon facing the Earth is not illuminated.
The Moon always faces the Earth with one side.
The line that separates the illuminated part of the Moon from the unlit part is called terminator.
In the first quarter, the Moon is visible at an angular distance of 90" from the Sun, and the sun's rays illuminate only the right half of the Moon facing us. In other phases, the Moon is visible to us in the form of a crescent. Therefore, in order to distinguish the growing Moon from the old one, we must remember: the old Moon resembles the letter “C”, and if the Moon is waxing, then you can mentally draw a vertical line in front of the Moon and you will get the letter “P”.
Due to the proximity of the Moon to the Earth and its large mass, they form the Earth-Moon system. The Moon and Earth rotate around their axes in the same direction. The plane of the Moon's orbit is inclined to the plane of the Earth's orbit at an angle of 5°9".
The intersection of the orbits of the Earth and the Moon is called nodes of the lunar orbit.
Sidereal(from Latin sideris - star) month is the period of rotation of the Earth around its axis and the same position of the Moon on the celestial sphere in relation to the stars. It is 27.3 Earth days.
Synodic(from the Greek synod - connection) a month is the period of complete change of lunar phases, i.e. the period of the Moon returning to its original position relative to the Moon and the Sun (for example, from new moon to new moon). It averages 29.5 Earth days. The synodic month is two days longer than the sidereal month, since the Earth and Moon rotate around their axes in the same direction.
The gravity on the Moon is 6 times less than the gravity on Earth.
The relief of the Earth's satellite is well studied. The visible dark areas on the surface of the Moon are called “seas” - these are vast waterless lowland plains (the largest is “Oksan Bur”), and the light areas are called “continents” - these are mountainous, elevated areas. The main planetary structures of the lunar surface are ring craters with a diameter of up to 20-30 km and multi-ring circuses with a diameter of 200 to 1000 km.
The origin of ring structures is different: meteorite, volcanic and shock-explosive. In addition, there are cracks, shifts, domes and fault systems on the surface of the Moon.
Studies by the Luna-16, Luna-20, and Luna-24 spacecraft have shown that the surface clastic rocks of the Moon are similar to terrestrial igneous rocks - basalts.
The meaning of the Moon in the life of the Earth
Although the mass of the Moon is 27 million times less than the mass of the Sun, it is 374 times closer to the Earth and has a strong influence on the planet, causing rising tides in some places and low tides in others. This happens every 12 hours 25 minutes, since the Moon makes a full revolution around the Earth in 24 hours 50 minutes.
Due to the gravitational influence of the Moon and the Sun on the Earth, ebb and flow(Fig. 2).
Rice. 2. Scheme of the occurrence of ebbs and flows on Earth
The most distinct and important in their consequences are tidal phenomena in the wave shell. They represent periodic rises and falls in the level of oceans and seas, caused by the gravitational forces of the Moon and the Sun (2.2 times less than the lunar one).
In the atmosphere, tidal phenomena manifest themselves in semidiurnal changes in atmospheric pressure, and in the earth's crust - in the deformation of the solid matter of the Earth.
On Earth, there are 2 high tides at the point closest and farthest from the Moon and 2 low tides at points located at an angular distance of 90° from the Moon-Earth line. Highlight cygisian tides, which occur on new and full moons and quadrature- in the first and last quarter.
In the open ocean, tidal movements are small. Water level fluctuations reach 0.5-1 m. In the inland seas (Black, Baltic, etc.) they are almost not felt. However, depending on the geographic latitude and the contours of the coastline of the continents (especially in narrow bays), water during high tides can rise up to 18 m (Bay of Fundy in the Atlantic Ocean off the coast of North America), 13 m on the western coast of the Sea of Okhotsk. In this case, tidal currents are formed.
The main significance of tidal waves is that, moving from east to west following the apparent movement of the Moon, they slow down the axial rotation of the Earth and lengthen the day, change the figure of the Earth by reducing polar compression, cause pulsation of the Earth’s shells, vertical displacements of the Earth’s surface, semidiurnal changes in atmospheric pressure change the conditions of organic life in the coastal parts of the World Ocean and, finally, affect the economic activities of coastal countries. Sea vessels can only enter a number of ports at high tide.
After a certain period of time on Earth they repeat solar and lunar eclipses. They can be seen when the Sun, Earth and Moon are on the same line.
Eclipse- an astronomical situation in which one celestial body blocks the light from another celestial body.
A solar eclipse occurs when the Moon comes between the observer and the Sun and blocks it. Since the Moon before an eclipse faces us with its unlit side, there is always a new moon before an eclipse, i.e. the Moon is not visible. It seems that the Sun is covered by a black disk; an observer from Earth sees this phenomenon as a solar eclipse (Fig. 3).
Rice. 3. Solar eclipse (the relative sizes of the bodies and the distances between them are relative)
A lunar eclipse occurs when the Moon, while aligned with the Sun and Earth, falls into the cone-shaped shadow cast by the Earth. The diameter of the Earth's shadow spot is equal to the minimum distance of the Moon from the Earth - 363,000 km, which is about 2.5 times the diameter of the Moon, so the Moon can be completely obscured (see Fig. 3).
Lunar rhythms are repeated changes in the intensity and nature of biological processes. There are lunar-monthly (29.4 days) and lunar-diurnal (24.8 hours) rhythms. Many animals and plants reproduce at a certain phase of the lunar cycle. Lunar rhythms are characteristic of many marine animals and plants of the coastal zone. Thus, people have noticed changes in their well-being depending on the phases of the lunar cycle.
Moon– satellite of planet Earth in the solar system: description, history of research, interesting facts, size, orbit, dark side of the Moon, scientific missions with photos.
Get away from the city lights on a dark night and admire the beautiful moonlight. Moon is the only earthly satellite that has been orbiting the Earth for more than 3.5 billion years. That is, the Moon has accompanied humanity since its appearance.
Due to its brightness and direct visibility, the satellite has been reflected in many myths and cultures. Some thought it was a deity, while others tried to use it to predict events. Let's take a closer look at the interesting facts about the Moon.
There is no "dark side"
- There are many stories where the far side of the moon appears. In reality, both sides receive the same amount of sunlight, but only one of them is visible to earth. The fact is that the time of the lunar axial rotation coincides with the orbital one, which means it is always turned to us with one side. But we explore the “dark side” with spacecraft.
The Moon influences Earth's tides
- Due to gravity, the Moon creates two bulges on our planet. One is on the side facing the satellite, and the second is on the opposite side. These ridges cause high and low tides throughout the Earth.
Luna tries to escape
- Every year the satellite moves away from us by 3.8 cm. If this continues, then in 50 billion years the Moon will simply run away. At that time, it will spend 47 days on the orbital flyby.
The weight on the Moon is much less
- The moon yields to Earth's gravity, so you'll weigh 1/6 less on the moon. That is why the astronauts had to move by jumping like a kangaroo.
12 astronauts have walked on the moon
- In 1969, Neil Armstrong was the first to set foot on satellite during the Apollo 11 mission. The last one was Eugene Cernan in 1972. Since then, only robots have been sent to the Moon.
No atmospheric layer
- This means that the surface of the Moon, as can be seen in the photo, is devoid of protection from cosmic radiation, meteorite impacts and solar wind. Serious temperature fluctuations are also noticeable. You will not hear any sounds, and the sky always seems black.
There are earthquakes
- Created by earth's gravity. The astronauts used seismographs and found that there were cracks and breaks several kilometers below the surface. The satellite is believed to have a molten core.
The first device arrived in 1959
- The Soviet spacecraft Luna 1 was the first to land on the Moon. It flew past the satellite at a distance of 5995 km, and then entered orbit around the Sun.
It is in 5th position in size in the system
- In diameter, the earth's satellite extends over 3475 km. The Earth is 80 times larger than the Moon, but they are about the same age. The main theory is that at the beginning of its formation, a large object crashed into our planet, tearing material into space.
We'll go to the moon again
- NASA plans to create a colony on the lunar surface so that there will always be people there. Work could begin as early as 2019.
In 1950, they planned to detonate a nuclear bomb on the satellite.
- It was a secret project during the Cold War - Project A119. This would show a significant advantage for one of the countries.
Size, mass and orbit of the Moon
The characteristics and parameters of the Moon should be studied. The radius is 1737 km, and the mass is 7.3477 x 10 22 kg, so it is inferior to our planet in everything. However, if compared with the celestial bodies of the Solar System, it is clear that it is quite large in size (in second position after Charon). The density indicator is 3.3464 g/cm 3 (in second place among moons after Io), and gravity is 1.622 m/s 2 (17% of Earth’s).
The eccentricity is 0.0549, and the orbital path covers 356400 – 370400 km (perihelion) and 40400 – 406700 km (aphelion). It takes 27.321582 days to completely circle the planet. In addition, the satellite is in a gravitational block, that is, it always looks at us from one side.
Physical characteristics of the Moon |
| Polar compression | 0,00125 |
|---|---|
| Equatorial | 1738.14 km 0.273 earth |
| Polar radius | 1735.97 km 0.273 earth |
| Average radius | 1737.10 km 0.273 earth |
| Large circumference | 10,917 km |
| Surface area | 3.793 10 7 km² 0.074 earth |
| Volume | 2.1958 10 10 km³ 0.020 earth |
| Weight | 7.3477 10 22 kg 0.0123 earth |
| Average density | 3.3464 g/cm³ |
| Acceleration free falls at the equator |
1.62 m/s² |
| First space speed |
1.68 km/s |
| Second space speed |
2.38 km/s |
| Rotation period | synchronized |
| Axis tilt | 1.5424° |
| Albedo | 0,12 |
| Apparent magnitude | −2,5/−12,9 −12.74 (with full moon) |
Composition and surface of the Moon
The Moon replicates the Earth and also has an inner and outer core, mantle and crust. The core is a solid iron sphere extending over 240 km. An outer core of liquid iron (300 km) is concentrated around it.
You can also find igneous rocks in the mantle, where there is more iron than ours. The crust extends for 50 km. The core covers only 20% of the entire object and contains not only metallic iron, but also small impurities of sulfur and nickel. You can see what the structure of the Moon looks like in the diagram.
Scientists were able to confirm the presence of water on the satellite, most of which is concentrated at the poles in shadowed crater formations and subsurface reservoirs. They think that it appeared due to the contact of the satellite with the solar wind.
Lunar geology diverges from Earth's. The satellite is devoid of a dense atmospheric layer, so there is no weather or wind erosion on it. Small size and low gravity lead to rapid cooling and lack of tectonic activity. You can note a huge number of craters and volcanoes. There are ridges, wrinkles, highlands and depressions everywhere.
The most noticeable contrast is between bright and dark areas. The first ones are called lunar hills, but the dark ones are called seas. The highlands were formed by igneous rocks, represented by feldspar and traces of magnesium, pyroxene, iron, olivine, magnetite and ilmenite.
Basalt rock formed the basis of the seas. Often these areas coincide with lowlands. You can mark channels. They are arcuate and linear. These are lava tubes, cooled and destroyed since volcanic hibernation.
An interesting feature is the lunar domes, created by the ejection of lava into the vents. They have gentle slopes and a diameter of 8-12 km. The wrinkles appeared due to the compression of tectonic plates. Most are found in the seas.
A notable feature of our satellite is impact craters formed when large space rocks fall. The kinetic impact energy forms a shock wave resulting in depression causing a lot of material to be ejected.
The craters range from small pits to 2500 km and a depth of 13 km (Aitken). The largest appeared in early history, after which they began to decrease. You can find approximately 300,000 depressions with a width of 1 km.
In addition, lunar soil is of interest. It was formed by impacts of asteroids and comets billions of years ago. The stones crumbled into fine dust that covered the entire surface.
The chemical composition of regolith differs depending on the position. If the mountains have a lot of aluminum and silicon dioxide, then the seas can boast of iron and magnesium. Geology was studied not only by telescopic observations, but also by analysis of samples.
Atmosphere of the Moon
The Moon has a weak atmosphere (exosphere), which causes its temperature to fluctuate greatly: from -153°C to 107°C. The analysis shows the presence of helium, neon and argon. The first two are created by solar winds, and the last is the decay of potassium. There is also evidence of frozen water reserves in craters.
Formation of the Moon
There are several theories about the appearance of the earth's satellite. Some people think that it’s all about the Earth’s gravity, which attracted the ready-made satellite. They formed together in the solar accretion disk. Age – 4.4-4.5 billion years.
The main theory is impact. It is believed that a large object (Theia) flew into the proto-Earth 4.5 billion years ago. The torn material began to rotate along our orbital path and formed the Moon. Computer models also confirm this. In addition, the tested samples showed almost identical isotopic compositions to ours.
Connection with the Earth
The Moon revolves around the Earth in 27.3 days (sidereal period), but both objects move around the Sun at the same time, so the satellite spends 29.5 days on one phase for the Earth (known phases of the Moon).
The presence of the Moon has an impact on our planet. First of all, we are talking about tidal effects. We notice this as sea levels rise. The Earth's rotation occurs 27 times faster than the Moon's. Ocean tides are also enhanced by the frictional coupling of water to the earth's rotation through ocean floors, water inertia, and basin oscillation.
Angular momentum accelerates the lunar orbit and lifts the satellite higher over a longer period. Because of this, the distance between us increases, and the earth's rotation slows down. The satellite moves away from us by 38 mm per year.
As a result, we will achieve mutual tidal locking, repeating the situation of Pluto and Charon. But this will take billions of years. So the Sun will most likely become a red giant and swallow us up.
Tides are also observed on the lunar surface with an amplitude of 10 cm for 27 days. Cumulative stress results in moon rays. And they last an hour longer because there is no water to dampen the vibrations.
Let's not forget about such a magnificent event as an eclipse. This happens if the Sun, satellite and our planet line up in a straight line. The lunar one appears if the full Moon appears behind the earth's shadow, and the solar one - the Moon is located between the star and the planet. During a total eclipse, you can see the solar corona.
The lunar orbit is tilted 5° to the Earth's, so eclipses occur at certain moments. The satellite needs to be located near the intersection of orbital planes. The periodicity covers 18 years.
History of lunar observations
What does the history of lunar exploration look like? The satellite is located close and visible in the sky, so prehistoric inhabitants could have followed it. Early examples of recording lunar cycles begin in the 5th century BC. e. This was done by scientists in Babylon, who noted the 18-year cycle.
Anaxagoras of Ancient Greece believed that the Sun and satellite were large-scale spherical rocks, where the Moon reflected sunlight. Aristotle in 350 BC believed that the satellite is the boundary between the spheres of the elements.
The connection between the tides and the Moon was stated by Seleucus in the 2nd century BC. He also thought that the height would depend on the lunar position in relation to the star. The first distance from the Earth and size was obtained by Aristarchus. His data was improved by Ptolemy.
The Chinese began predicting lunar eclipses in the 4th century BC. They already knew then that the satellite reflected sunlight and was made in a spherical shape. Alhazen said that the sun's rays are not mirrored, but are emitted from each lunar area in all directions.
Until the advent of the telescope, everyone believed that they were seeing a spherical object, as well as a completely smooth one. In 1609, the first sketch by Galileo Galilei appeared, which depicted craters and mountains. This and observations of other objects helped advance Copernicus' heliocentric concept.
The development of telescopes has led to the detailing of surface features. All craters, mountains, valleys and seas were named in honor of scientists, artists and prominent figures. Until the 1870s all craters were considered volcanic formations. But it was only later that Richard Proctor suggested that they might be impact marks.
Exploring the Moon
The space era of lunar exploration has allowed us to take a closer look at our neighbor. The Cold War between the USSR and the USA caused all technologies to develop rapidly, and the Moon became the main target of research. It all started with spacecraft launches and ended with human missions.
The Soviet Luna program began in 1958, with the first three probes crashing onto the surface. But a year later, the country successfully delivered 15 devices and obtained the first information (information about gravity and images of the surface). The samples were delivered by missions 16, 20 and 24.
Among the models were innovative ones: Luna-17 and Luna-21. But the Soviet program was closed and the probes were limited to just surveying the surface.
NASA started launching probes in the 60s. In 1961-1965. There was a Ranger program that created a map of the lunar landscape. Then in 1966-1968. Rovers landed.
In 1969, a real miracle happened when Apollo 11 astronaut Neil Armstrong took the first step on the satellite and became the first man on the Moon. It was the culmination of the Apollo mission, which had originally aimed for human flight.
There were 13 astronauts on the Apollo 11-17 missions. They managed to extract 380 kg of rock. Also, all participants were engaged in various studies. After this there was a long lull. In 1990, Japan became the third country that managed to install its probe above the lunar orbit.
In 1994, the United States sent a ship to Clementine, who was creating a large-scale topographic map. In 1998, a scout managed to find ice deposits in the craters.
In 2000, many countries became eager to explore the satellite. ESA sent the SMART-1 spacecraft, which analyzed the chemical composition in detail for the first time in 2004. China launched the Chang'e program. The first probe arrived in 2007 and remained in orbit for 16 months. The second device was also able to capture the arrival of asteroid 4179 Toutatis (December 2012). Chang'e-3 launched a rover to the surface in 2013.
In 2009, the Japanese Kaguya probe entered orbit, studying geophysics and creating two full-fledged video reviews. Since 2008-2009, the first mission from the Indian ISRO Chandrayaan has been in orbit. They were able to create high-resolution chemical, mineralogical and photogeological maps.
NASA used the LRO spacecraft and the LCROSS satellite in 2009. The internal structure was examined by two additional NASA rovers launched in 2012.
The treaty between the countries states that the satellite remains a common property, so all countries can launch missions there. China is actively preparing a colonization project and is already testing its models on people who are locked in special domes for a long time. America, which also intends to populate the Moon, is not far behind.
Use the resources of our website to view beautiful and high-quality photos of the Moon in high resolution. Useful links will help you find out the maximum known amount of information about the satellite. To understand what the Moon is like today, just go to the appropriate sections. If you can’t buy a telescope or binoculars, then look at the Moon through an online telescope in real time. The image is constantly updated, showing the crater surface. The site also tracks the phases of the moon and its position in orbit. There is a convenient and fascinating 3D model of the satellite, the solar system and all celestial bodies. Below is a map of the lunar surface.
Earth satellites: from artificial to natural
Astronomer Vladimir Surdin about expeditions to the Moon, the Apollo 11 landing site and the equipment of the astronauts:
Click on the image to enlarge it
The Moon, after the Sun, is the second brightest object. It is the fifth largest object in the solar system. The average distance between the centers of the Moon and the Earth is 384,467 km. The mass of the Moon corresponds to the value 7.33 * 1022 kg.
Since ancient times, people have made attempts to describe and explain its movement. The basis of all modern calculations is Brown's theory, which was created at the turn of the 19th - 20th centuries. To determine the exact movement of this, more than just the mass of the Moon was needed. Numerous coefficients of trigonometric functions were taken into account. Modern science is capable of making more accurate calculations.
Laser ranging makes it possible to measure the sizes of celestial objects with an error of only a few centimeters. With its help, it was established that the mass of the Moon is significantly less than the mass of our planet (81 times), and its radius is 37 times less. For a long time it was not possible to accurately determine this value, but the launch of space satellites made it possible to open up new perspectives. An interesting fact is known that in Newton’s time the mass of the Moon was determined by the magnitude of the tide it caused.
We can see the illuminated surface of this satellite in different ways. The visible part of the disk illuminated by the Sun is called the phase. There are four phases in total: the completely dark surface of the Moon is the new moon, the growing crescent moon is the first quarter, the fully illuminated disk is the full moon, the illuminated half on the second side is the last quarter. They are expressed in hundredths and tenths of a unit. The change of all lunar phases is the synodic period, which represents the revolution of the Moon from the new moon phase to the subsequent new moon. It is also called a synodic month, equal to approximately 29.5 days. During this period of time, the Moon will be able to travel along the orbit and have time to be in the same phase twice. The sidereal orbital period, lasting 27.3 days, is the full revolution of the Moon around the Earth.
It is a mistakenly common statement that we see the surface of the Moon from one side and that it does not rotate. The movements of the Moon occur in the form of rotation around its axis and revolution around the Earth and the Sun
A complete revolution around its own axis occurs in 27 Earth days and 43 minutes. and 7 o'clock. Circulation in an elliptical orbit around the Earth (one full revolution) occurs in the same time. This is influenced by tides in the lunar crust, which cause tides on Earth, which occur under the influence of lunar gravity.
Being at a farther distance from the Moon than the Earth, the Sun, due to its enormous mass, attracts the Moon twice as strongly as the Earth. The Earth distorts the trajectory of the Moon around the Sun. In relation to the Sun, its trajectory is always concave.
The moon has no atmosphere, the sky above it is always black. Due to the fact that sound waves do not travel in a vacuum, there is complete silence on this planet. Under direct rays in the daytime it is many times higher than water, and at night it reaches -150 C. The moon is one. Its density is only 3.3 rubles. more water. On its surface there are huge plains that are covered with solidified lava, many craters formed when the force of gravity is inferior to the earth's gravity, and the weight of the Moon is less than the Earth, so a person can shrink by 6 times while on the Moon.
Using radioactive substances, scientists determined the approximate age of the Moon, which is 4.65 billion years. According to the last most plausible hypothesis, it is assumed that the formation of the Moon occurred as a result of a giant collision of a huge celestial body with the young Earth. According to another theory, the Earth and Moon were formed independently in completely different parts of the solar system.
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 of 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, there is anyone left on the planet by that time.
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.