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 square 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. Rotation period, 27.32. The lowest surface temperature is-183 degrees Celsius. 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. The physical condition of the moon-the topography of the moon surface mainly includes: the name crater was called 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 moon seas identified, and some landforms are called "Moon Lake" or "Moon-like Sea". 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 covers 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 land of the moon is roughly equal to the ocean of the moon. But on the back of the moon, the land of the moon is much bigger than the ocean of the moon. 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-like, 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. The moon itself revolves around the earth from west to east, so it should rise in the west and set in the east. However, because the earth's rotation direction is also from west to east, the actual visual effect is that the moon rises in the west and sets in the west.

Material introduction

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 1000 km is the lunar mantle, which occupies most of the moon's volume. Below the moon's mantle is the moon's core, whose temperature is about 1000 degrees, which 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 surface temperature is (t) -233~ 123℃ (average -23℃), and the atmospheric pressure is1.3×10-10 kpa. The moon orbits the earth once every 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 surface. 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 influenced by a certain moment, 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 west 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; When the full moon is just at the intersection of the moon, an eclipse will occur;