Knowledge about the moon

Overview The moon is commonly known as the moon, also known as the moon. The moon is also about 4.6 billion years old and is closely related to the earth. The moon also has layered structures such as shell, mantle and core. The average thickness of the outermost lunar shell is about 60-65 kilometers. Below the lunar crust to the depth of 1000 km is the lunar mantle, which occupies most of the volume of the moon. Below the moon mantle is the moon nucleus, the temperature of which is about 1000 degrees, and it is likely to be in a molten state. The moon is about 3476 kilometers in diameter, which is 3/ 1 1 of the earth. The volume is only 1/49 of the earth's, and the mass is about 735 billion tons, which is equivalent to 1/8 1 of the earth's mass. The gravity on the surface of the moon is almost equal to 1/6 of the gravity of the earth. There are dark parts and bright areas on the moon. When early astronomers observed the moon, they thought that the dark area was covered by seawater, so they called it "sea". The more famous ones are the sea of clouds, the wet sea and the sea of tranquility. The bright part is the mountains, where mountains are stacked and criss-crossed, and craters are dotted. Bailey Crater is located near the South Pole, with a diameter of 295 kilometers, which can hold the whole Hainan Island. The deepest mountain is Newton crater, which is 8788 meters deep. Besides craters, there are ordinary mountains on the moon. Mountains and valleys overlap, giving you a unique perspective. The front of the moon always faces the earth. On the other hand, most of the back of the moon can't be seen from the earth, except the area near the edge of the moon, which can be seen occasionally due to the movement of Libra. In the era without detectors, the back of the moon has always been an unknown world. A major feature of the back of the moon is that there are almost no dark moon features such as the moon and the sea. When the probe runs to the back of the moon, it will not be able to communicate directly with the earth. The moon revolves around the earth for about one lunar month, and moves half a degree relative to the background starry sky every hour, which is similar to the apparent diameter of the moon. Unlike other satellites, the orbital plane of the moon is closer to the ecliptic plane than the equatorial plane of the earth. Relative to the background starry sky, the time required for the moon to go around the earth (the moon makes one revolution) is called sidereal month; The time between the new moon and the next one (or the time between two identical moon phases) is called the new moon. The reason why Wang Shuo's moon is longer than that of the star moon is that during the earth's operation on the moon, it moved forward a certain distance in its orbit around the sun. Because the rotation period of the moon is exactly the same as its period of revolution, we can only see that the moon always faces the earth with the same face. From the early days of the moon's formation, the moon was affected by a moment /url], which led to the slow rotation speed. This process is called tidal locking. Therefore, part of the angular momentum of the earth's rotation is converted into the angular momentum of the moon's revolution around the earth. As a result, the moon is far away from the earth at a speed of about 38 mm per year. At the same time, the earth's rotation is getting slower and slower, and the length of a day is getting longer every year 15 microsecond. The gravity exerted by the moon on the earth is one of the reasons for the tidal phenomenon. The orbit of the moon around the earth is synchronous, and the so-called synchronous rotation is not strict. Because the orbit of the moon is elliptical, when the moon is at perihelion, its rotation speed can't keep up with the revolution speed, so we can see that the eastern part of the moon reaches 98 degrees east longitude. On the contrary, when the moon is at apohelion, its rotation speed is faster than its revolution speed, so we can see that the western part of the moon passes through 98 degrees Darcy. This phenomenon is called Libra movement. Because the orbit of the moon is inclined to the equator of the earth, when the moon moves in the starry sky, the polar regions will shake about 7 degrees, which is called Libra movement. Furthermore, since the distance between the earth and the moon is only 60 times that of radius of the earth, if the observer observes the moon from sunrise to sunset, the observation point will have the displacement of the diameter of the earth, which can be seen in the area with the longitude of 1 degree. This phenomenon is called Libra movement. Strictly speaking, the earth and the moon revolve around a concentric center, which is 4,700 kilometers away from the center of the earth (2/3 of radius of the earth's). Because the center of homogeneity is below the surface, the movement of the earth around the center of homogeneity seems to be "shaking". Seen from above the North Pole of the Earth, both the Earth and the Moon rotate clockwise. Moreover, the moon is also clockwise around the earth; Even the earth moves clockwise around the sun. Many people don't understand why the inclination of the moon's orbit and the inclination of the moon from the axis change so much. In fact, the orbital inclination is relative to the central celestial body (the earth), while the axial inclination is relative to the orbital plane of the satellite (the moon) itself. In this definition, customization is very suitable for general situations (such as the orbit of a satellite) and the value is quite fixed, but the moon is not. The orbit plane of the moon (ecliptic plane) keeps an included angle of 5. 145396 with the ecliptic plane (earth's orbit plane), while the rotation axis of the moon forms an included angle of 1.5424 with the normal of the ecliptic plane. Because the earth is not a perfect sphere, but bulges at the equator, the white road surface keeps precessing (that is, the intersection with the ecliptic rotates clockwise) and completes one week every 6793.5 days (18.5966). During this period, the angle between the white plane and the equatorial plane of the earth (the equatorial plane of the earth inclines to the ecliptic plane at 23.45) will change from 28.60 (i.e. 23.45+5. 15) to18.30 (i.e. 23.45-5. 15). Similarly, the angle between the rotation axis of the moon and the white plane will be between 6.69 (that is, 5. 15+ 1.54) and 3.60 (that is, 5. 15- 1.54). These changes in the lunar orbit will in turn affect the inclination of the earth's rotation axis, making it swing by 0.002 56, which is called nutation. The two intersections between the ecliptic plane and the ecliptic plane are called the lunar intersection-the ascending intersection (north point) refers to the point where the moon passes to the north of the ecliptic plane; Descending node (South Point) refers to the point where the moon passes south of the ecliptic. When the new moon is just at the intersection of the moon, a solar eclipse will occur; An eclipse occurs when the full moon is just at the intersection of the moons. The average track radius of the track data is 384400km, the track eccentricity is 0.0549, the perigee distance is 363300km, and the apogee distance is 405. The average period of revolution of 500 km is 27 days, 7 hours and 43 minutes 1 1.559 seconds, the average revolution speed 1.023 km/s, and the orbital inclination varies from 28.58 to 18.28 (the intersection angle with the ecliptic plane is 5. 145). Ascending node right ascension 125.08 perigee radiation angle 3 18. 15 silent winter chapter (repeat phase/day). 19, the average distance between the moon and the earth is ~ 384,400km, the regression period of the intersection point is 18.6 1, the perigee movement period is 8.85 years, and the solar eclipse period is 346.6 days. 1810/1The average inclination of celestial orbit and ecliptic is 5 9'. The average inclination of the equator and ecliptic of the moon is132'. The physical characteristics are that the equatorial diameter is 3,476.2km, The average density of water with polar diameter of 472.0km, flatness of 0.00 12 and surface area of 3.976x128+0022kg is 3.350 times that of equatorial gravity acceleration 1.62 m/s2. The escape speed of the earth 1/6 is 2.38km/ s, the second rotation period is 27 days, 7 hours and 43 minutes 1 1.559 seconds (synchronous rotation), and the rotation speed is 16.655 m/s (at the equator). Unequal albedo 0. 12 apparent magnitude at full moon-12.74 surface temperature (T) -233~ 123℃ (average -23℃) atmospheric pressure1.3×10-/. Kloc-0/ Compared with the background star, the lunar node 27.2 1220, compared with the ascending node, the first man-made object in the history of human lunar exploration was the unmanned lander Luna-2 of the former Soviet Union, which crashed into the moon in September 1959. Lunar 3 photographed the back of the moon on June 7 10 of the same year. Lunar 9 is the first lander to soft land on the moon. It sent back photos taken on the surface of the moon on February 3, 1966. In addition, Lunar/KOOC-0/0 successfully entered the scheduled orbit on March 3/KOOC-0/,/KOOC-0/966, becoming the first artificial satellite on the moon. During the cold war, the United States of America and the former Soviet Union always hoped to stay ahead of each other in space science and technology. The space race reached its climax on1July 20th, 969 when the first man landed on the moon. Neil armstrong, commander of Apollo 1 1, was the first man to land on the moon, and eugene cernan was the last. He was a member of Apollo 17 in February, 972. Apollo 1 1 astronauts left a 9-inch by 7-inch stainless steel plaque on the surface of the moon to commemorate the landing and provide some information for other creatures who might find it. Six Apollo missions and three unmanned missions to the moon (Lunar 16, 20 and 24) brought back rock and soil samples from the moon. In February 2004, President george walker bush of the United States of America proposed to send a man to the moon by 2020. The European Space Agency and People's Republic of China (PRC) also plan to send probes to the moon. The European Smart 1 detector was launched on September 27th, 2003, and went into orbit around the moon on June 27th+June 5th, 2004. It will investigate the lunar environment and make an X-ray map of the lunar surface. People's Republic of China (PRC) is also actively carrying out the lunar exploration program, seeking the feasibility of developing lunar resources, especially the helium isotope helium -3, which is expected to become the future energy source of the earth. China people and national lunar exploration plan, see the Chang 'e project. Japan and India are close behind. Japan has preliminarily determined the mission of exploring the moon in the future. JAXA has even begun to plan a manned lunar base. India will be the first to launch Chandrayan, an unmanned lunar probe. Myths and Legends In the ancient myths of China people, there are countless stories about the moon. In ancient Greek mythology, the name of the goddess of the moon was themis. She is the twin sister of Apollo, the sun god, and the goddess of hunting. The astronomical symbol of the moon is like a crescent moon, symbolizing the bow of Artemis. Spherical Movement The Moon is the only natural satellite of the Earth and the closest celestial body to the Earth. Its average distance from the earth is about 384,406,5438+0 km. Its average diameter is about 3476 kilometers, slightly larger than the earth's diameter 1/4. The surface area of the moon is 38 million kilometers, which is not as big as our Asia. The mass of the moon is about 735 billion tons, which is equivalent to 1/8 1 of the earth's mass, and the surface gravity of the moon is almost equivalent to 1/6 of the earth's gravity. The orbit of the moon The moon orbits the earth in an elliptical orbit. The great circle cut by this orbital plane on the celestial sphere is called "White Road". The ecliptic plane is neither coincident with the celestial equator nor parallel to the ecliptic plane, and its spatial position is constantly changing. The period is 173 days. The rotation of the moon The rotation period of the moon around the earth is 27.438+066 days, which happens to be a sidereal moon, so we can't see the back of the moon. We call this phenomenon "synchronous rotation", which is almost a universal law in the satellite world. It is generally believed that it is the result of the long-term tidal action of planets on satellites. The libration is a wonderful phenomenon, which enables us to see 59% of the moon. The main reasons are as follows: 1. In different parts of the elliptical orbit, the rotation speed does not match the revolution angular speed. 2, the intersection of the white road and the equator. Physical conditions The topography of the lunar surface mainly includes: The name crater was named by Galileo. It is a remarkable feature of the lunar surface, covering almost the whole lunar surface. The largest crater is the Bailey Mountain near the South Pole, with a diameter of 295 kilometers, which is a little larger than Hainan Island. A small round mountain, or even a pothole of tens of centimeters. There are about 33,000 with a diameter of not less than 65,438+000m m. It accounts for 7- 10% of the lunar area. A Japanese scholar put forward the classification of craters in 1969, which can be divided into Cravey type (ancient craters are generally unrecognizable, and some craters contain mountains), Copernican type (young craters often have "radial lines", and the inner wall generally has concentric sections and a central peak), Archimedean type (the ring wall is low, which may have evolved from Copernicus type). The dark part of the moon seen by the naked eye is actually a vast plain on the moon. Due to historical reasons, this misnamed name has been preserved to this day. There are 22 identified moon seas, and some landforms are called "moon seas" or "moon-like seas". Most of the 22 recognized ones are distributed on the front of the moon. Three in the back and four on the side. On the front, the area of the Moon Sea is slightly over 50%, and the largest "storm sea" covers an area of 5 million square kilometers, almost the total area of nine France. Most of the moon seas are generally round and oval, and most of them are surrounded by some mountains, but some seas are connected together. Besides the sea, there are five lakes with similar topography-Hu Meng, Dead Lake, Fox Xia, Qiuhu and Chun Hu, but some lakes are bigger than the sea. For example, Hu Meng has an area of 70,000 square kilometers, which is much larger than Qihai. The parts of the moon and the ocean that extend to the land are called "bays" and "swamps", and they are both distributed on the front. There are five bays: Luwan, Xiawan, Central Bay, Hongwan and Yue Mei Bay. There are three kinds of marshes: humus, epidemic marshes and dream marshes. Actually, there is no difference between a swamp and a bay. The topography of the Moon Sea is generally low, similar to the basins on the earth. The moon sea is1-2km lower than the average moon horizon, and the southeast of the lowest sea is even 6000m lower than its surroundings. The albedo of the moon (a physical quantity to measure the ability to reflect sunlight) is also relatively low, so it looks darker now. The land and mountains on the moon are called the moon land, which is generally 2-3 kilometers above the horizon of the moon sea. Because of the high albedo, it looks brighter. On the front of the moon, the area of the moon land is roughly equal to that of the moon sea, but on the back of the moon, the area of the moon land is much larger than that of the moon sea. Isotope determination shows that the moon and land are much older than the moon and ocean, and they are the oldest landforms on the moon. On the moon, in addition to many craters, there are some mountains similar to those on the earth. Mountains on the moon often borrow the names of mountains on the earth, such as Alps and Caucasus mountains. The longest mountain range is the Apennines, which stretches for 1000 km, but its height is only three or four kilometers higher than the moon horizon. There are also some steep peaks in the mountains, whose height was overestimated in the past. At present, it is believed that the heights of most peaks are similar to those of the earth, and the highest peaks (also near the south pole of the moon) are only 9000 meters and 8000 meters. On the moon, there are 6 peaks over 6000 meters, 20 at 5000-6000 meters, 80 at 4000-5000 meters, and 200 at 1000 meters. The mountains on the moon have a common feature: the slopes on both sides are asymmetrical, and the slopes on the seaward side are steep, sometimes cliff-shaped, while the other side is quite flat. In addition to the high mountains, there are four cliffs hundreds of kilometers long on the moon. Three of them stand out in the Moon Sea, also known as the "Moon Graben". Another main feature of the radiation pattern on the surface of the moon is that some young craters often have beautiful "radiation patterns", which is a bright belt extending in all directions with craters as the radiation point, and it passes through mountains, the moon sea and craters almost in a straight line. The length and brightness of radiation patterns are different, and the most striking one is the radiation pattern of Tycho crater. The longest one is as long as 1800 km, especially at full moon. Secondly, Copernicus and Kepler craters also have quite beautiful radiation patterns. According to statistics, there are 50 craters with radiation patterns. The reason for the formation of radiation pattern is still inconclusive. Essentially, it is closely related to the theory of crater formation. At present, many people tend to say that meteorite impact may make high-temperature debris fly far on the moon, with no atmosphere and little gravity. Other scientists believe that the function of volcano is not ruled out, and the eruption of volcano may also form a flying radiation shape. Moon Gap There are many famous rift valleys on the earth, such as the Great Rift Valley in East Africa. There is also such a structure on the surface of the moon-those seemingly winding black cracks are the Moon Valley, and some extend for hundreds of meters to Qian Qian meters, with widths ranging from several kilometers to tens of kilometers. Most of those broad moon valleys appear on the flat land of the moon, while those narrow and narrow moon valleys (sometimes called moon streams) can be seen everywhere. The most famous Moon Valley is the alpine Moon Valley connecting Yuhai and Leng Hai, which is located in the southeast of Plato's crater. It cut off the Alps on the moon, which is very spectacular. The photos taken from space are estimated to be 130 km long and 10- 12 km wide. Why can't we always see the back of the moon? The moon always faces the earth. Because the autobiography of the moon is the same as that of the revolutionary period. (27.32 166) To understand this phenomenon, we can do an experiment. Draw a circle and mark the positive east, west, north and south directions. You stand at the center of the circle (representing the earth), find another friend, stand on the circle, let his face face forward (that is, don't twist his neck), move counterclockwise along the circle, and ask his face to always face the center of the circle, that is, you. Then such a process basically simulates the process of the moon's rotation around the earth. Obviously, in this process, your friends always face you. Let's understand why in such a process, period of revolution is equal to the rotation period. Your friend starts from your due north, turns around you, and appears in due north again. He completes a revolution. It is similar to the time that the moon goes around the earth once. Let's see what his rotation time is. We might as well set your friend's posture when he is in your due north position and his face is facing due south as the initial posture. Then we can find that when your friend moves counterclockwise to your due west position, his rotation posture rotates counterclockwise by 90 degrees. If your friend doesn't "rotate" in this process, he will still face due south when he is in this position. In the actual experiment, your friend faces due east, so he rotates 90 degrees counterclockwise around himself relative to his initial position. Similarly, when he walked directly south of you, he autobiographed 180 degrees relative to the initial posture. When he was walking due east of you, he autobiographed 270 degrees relative to his original posture. When he walked to your true north again, he autobiographed 360 degrees relative to his original posture. In other words, he completed a rotation cycle. Because the completion of a revolution is only the completion of a rotation process, in terms of time, this rotation period is equal to period of revolution. Because in the whole process, your friend always faces you with his body and face, that is to say, the moon always faces the earth. Guanghan Palace-Moon When night falls, a bright moon rises in the night sky, and the clear moonlight spreads all over the earth, which makes people feel countless feelings and reverie. Scholars especially like the moon. The Tang Dynasty poet Zhang said that "whoever sees the moon at the first sight on the river shines at the beginning of the month", and the Song Dynasty writer Su Shi said that "when will the moon ask for wine" are all well-known poems about the moon. When the moon is bright, we can clearly see that there are dark parts and bright areas on the moon. When early astronomers observed the moon, they thought that the dark area was covered by seawater, so they called it "sea". The more famous ones are the sea of clouds, the wet sea and the sea of tranquility. The bright part is the mountains, where mountains are stacked and criss-crossed, and craters are dotted. Bailey Crater is located near the South Pole, with a diameter of 295 kilometers, which can hold the whole Hainan Island. The deepest crater is Newton crater with a depth of 8788 kilometers. Besides craters, there are ordinary mountains on the moon. Mountains and valleys overlap, giving you a unique perspective. The age of the moon, about 4.6 billion years, is closely related to the earth. The moon also has layered structures such as shell, mantle and core. The average thickness of the outermost lunar shell is about 60 ~ 65 kilometers. Below the lunar crust to the depth of 1000 km is the lunar mantle, which occupies most of the volume of the moon. Below the moon mantle is the moon nucleus, the temperature of which is about 1000 degrees, and it is likely to be in a molten state. The moon is about 3476 kilometers in diameter, which is 3/ 1 1 of the earth. The volume is only 1/49 of the earth's, and the mass is about 735 billion tons, which is equivalent to 1/8 1 of the earth's mass. The gravity on the surface of the moon is almost equal to 1/6 of the gravity of the earth. Discussion on the causes 1. Split theory. This is the earliest hypothesis to explain the origin of the moon. As early as 1898, George Darwin, the son of the famous biologist Darwin, pointed out in the article Tides and Similar Effects in the Solar System that the moon was originally a part of the earth, but later, due to the rapid rotation of the earth, some substances on the earth were thrown out, forming the moon after leaving the earth, and the pit left on the earth is now the Pacific Ocean. This view was quickly opposed by some people. They think that it is impossible to throw such a big thing at the speed of the earth's rotation. Besides, if the moon was thrown out by the earth, then the material composition of the two should be the same. However, through the analysis of the rock samples brought back from the moon by Apollo 12 spacecraft, it is found that there is a great difference between them. Second, the capture theory. This hypothesis holds that the moon was originally just an asteroid in the solar system. Once, because it ran near the earth, it was captured by the gravity of the earth and never left the earth again. There is also a view close to the capture theory, that is, the earth keeps accumulating substances that enter its orbit, and over time, more and more things are accumulated, and finally the moon is formed. However, it has also been pointed out that for a planet as big as the moon, the earth may not have that great power to capture it. Third, homology theory. This hypothesis holds that both the Earth and the Moon are floating nebulae in the solar system, which rotate and accrete at the same time to form stars. In the process of accretion, the earth is a little faster than the moon and becomes a "brother". This assumption has also been challenged by objective existence. By analyzing the rock samples brought back from the moon by Apollo 12 spacecraft, people found that the moon is much older than the earth. Some people think that the moon should be at least 7 billion years old. Fourth, the big collision theory. This is a new hypothesis about the origin of the moon in recent years. 1986 On March 20th, at the symposium on the Moon and Planets held at the Johnson Space Center in Houston, Ben Ci and Slattery of Los Alamos National Laboratory and Cameron of Smith Center for Astrophysics of Harvard University put forward the big collision hypothesis. This hypothesis holds that in the early stage of the evolution of the solar system, a large number of "planetesimals" were formed in interstellar space, and they grew up through collision and accretion. The planetesimals merged to form the primitive earth, and at the same time formed celestial bodies equivalent to 0. 14 times the mass of the earth. In the course of their respective evolution, these two celestial bodies formed a metal core dominated by iron and a curtain shell composed of silicate respectively. Because the two celestial bodies are not far apart, there is a great chance of meeting. Occasionally, small celestial bodies hit the earth at a speed of about 5 kilometers per second. The violent collision not only changed the motion state of the earth and tilted its axis, but also caused small celestial bodies to be smashed, the silicate shell and mantle were heated and evaporated, and the expanding gas and huge speed took a large number of shattered dust away from the earth. These materials flying away from the earth are mainly composed of the mantle of collision bodies, and there are also a small amount of materials on the earth, with a ratio of 0.85:0. 15. When the impactor broke, the metal core separated from the curtain slowed down due to the expanding and flying gas, and was absorbed to the earth after about 4 hours. The gas and dust flying away from the earth are not completely out of the control of the earth's gravity. They accrete and combine with each other to form a completely melted satellite, or form several separated small satellites first, and then gradually accrete to form a partially melted satellite. Sphere composition 4.5 billion years ago, the surface of the moon was still a sea of liquid magma. Scientists believe that the mineral KREEP, which constitutes the moon, shows the chemical clues left by the magma ocean. KREEP is actually a component called "incompatible element" by scientists-substances that cannot enter the crystal structure are left behind and float to the surface of magma. For researchers, KREEP is a convenient clue to understand the volcanic history of the lunar crust and infer the frequency and time of the impact of comets or other celestial bodies. The lunar crust consists of many major elements, including uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, aluminum and hydrogen. When bombarded by cosmic rays, each element emits specific gamma radiation. Some elements, such as uranium, thorium and potassium, are already radioactive, so they can emit gamma rays by themselves. But whatever the reason, the gamma rays emitted by each element are different, and each element has its own unique spectral line characteristics, which can be measured by spectrometer. Until now, human beings have not made a comprehensive measurement of the abundance of moon elements. At present, the measurement of spacecraft is limited to a part of the moon. Libra Movement Because the orbit of the moon is elliptical, when the moon is at perihelion, its rotation speed can't keep up with the revolution speed, so we can see that the eastern part of the moon reaches 98 degrees east longitude. On the contrary, when the moon is at apohelion, its rotation speed is faster than its revolution speed, so we can see the west of the moon at 98 degrees Darcy. This phenomenon is called meridian libration. The front and back of the moon;

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