What is the information about the moon?

The moon, commonly known as the moon, also known as the lunar moon, is the only natural satellite of the earth and the closest celestial body to the earth.

The average distance to the moon is 38440 1 km. This distance is about 10 times of the equatorial circumference of the earth. The orbit of the moon is elliptical, with an average distance of 363,300 kilometers at perigee and 405,500 kilometers at apogee. The moon is 3476 kilometers in diameter, which is about 3/ 1 1 of the earth's diameter. The surface area of the moon is about114 of the surface area of the earth, slightly smaller than that of Asia. The moon is only 1/49 the size of the earth. The mass of the moon is about 1/8 1.3 of the mass of the earth. The average density of lunar material is 3.34 grams per cubic centimeter, which is only 3/5 of the density of the earth. The gravitational acceleration of a free fall on the lunar surface is 1/6 of that of the earth. The escape speed on the moon is about 2.4 kilometers per second, which is about 1/5 of the escape speed on the earth.

The moon makes an elliptical motion around the earth, and it also accompanies the earth to revolve around the sun once a year. The moon is not only influenced by the gravity of the earth, but also by the gravity from the sun, so it has a very complicated orbital motion. The moon itself is neither luminous nor transparent, but it can reflect sunlight. Because the relative positions of the sun, the earth and the moon are constantly changing, the illuminated part of the moon seen by observers on the earth is also constantly changing, resulting in different visual shapes. This is called the moon phase. The change of the moon phase is regular. The periodicity of the moon phase changes provides people with a measure of time. The lunar calendar or lunar month is based on the moon phase, from which the week evolved.

Since ancient times, people have known that the moon always faces the same direction of the earth. This is because the rotation period of the moon is exactly equal to that of the moon around the earth, and the same two periods are the result of long-term tidal action.

The inclination of the equatorial plane of the moon and its orbital plane is 6 degrees 4 1 min. Because of this inclination and the uneven speed of the moon, observers at a certain point on the ground can still see the edge of the moon swinging back and forth during the movement of the moon. From the ground observation, not only half of the moon can be seen, but also 59% of the moon can be seen, and the remaining 4 1% cannot be seen directly.

The shape of the moon is also oblate, with the north and south poles slightly oblate and the equator slightly higher. Its average polar radius is 500 meters shorter than the equatorial radius. The polar regions are also asymmetrical, with the Arctic region uplifting and the Antarctic region sinking by about 400 meters. The center of gravity of the moon does not coincide with the geometric center, and the center of gravity is 2 kilometers away from the earth. This conclusion has been confirmed by the data obtained by Apollo landing on the moon.

On the moon, the mountains are undulating and densely covered with peaks. In addition, there are various distinctive names such as ocean, sea, bay and lake. In fact, there is no water on the moon. Only in the early years, observers borrowed the name of the earth by imagination, which is at most some morphological similarities.

The most obvious feature on the moon is the crater, which usually refers to the bowl-shaped pit structure. Among them, the large diameter can exceed 100 km, and the small one is just a pit. There are more than 30,000 craters with a diameter greater than 1km, accounting for 7 ~ 10% of the surface area of the moon. Most craters are named after famous astronomers or other scholars. There are four craters on the back of the moon, named after China's ancient astronomers Shi Shen, Zhang Heng, Zu Chongzhi and Guo Shoujing. The largest craters on the moon are: Bailey crater near the South Pole, with a diameter of 295 kilometers; Crater Crater in Krakow, with a diameter of 233 kilometers; Newton crater, 230 kilometers in diameter. There is a central peak or central peak group in the central area of many craters, which is as high as 2.5 kilometers.

The dark spots on the surface of the moon seen by naked eyes are called "Moon Sea", which is an endless plain. On the front of the moon, the area of the moon sea accounts for about half of the whole hemisphere surface. There are 22 known moon seas (including the back), the largest of which is called storm ocean, covering an area of about 5 million square kilometers. Yuhai covers an area of about 900,000 square kilometers. The area of Jinghai in the center of the moon is about 260,000 square kilometers. In addition, the larger ones are Chenghai, Fengfuhai, Dangerous Sea and Haiyun. Most of the Moon Sea is round and closed, surrounded by mountains. Some moon seas extend to land and are called bays, while small moon seas are called lakes.

The land on the moon is higher than the ocean on the moon, generally 2 ~ 3 kilometers higher. The lunar land is mainly composed of light plagioclase with high albedo. On the front of the moon, the land area is roughly equal to the sea area, while on the back, the land area is larger. According to isotope dating, the land-forming age of the moon is 4.6 billion years, which is earlier than that of the moon and the sea. There are also some mountains on the moon, most of which are named after the mountains on the earth, such as Apennines, Caucasus and Alps. The longest mountain range is as long as 1000 km, which is often 3 ~ 4 km higher than the moon sea. The highest peak is near the south pole of the moon, reaching 9000 meters, which is higher than Mount Everest, the highest on the earth. In addition to mountains, there are hundreds of kilometers of cliffs, the longest of which is Altai Cliff.

There are some radiation patterns on the surface of the moon, typically around Tycho crater and Copernicus crater. There are 12 radiation lines in Tycho crater, which extend radially outward from the periphery of the crater, and the longest is 1800 km, which is most clearly seen at the full moon. Its cause is still inconclusive: some people say it was formed by volcanic eruption; Some people think that it was caused by meteorites bombarding the moon.

Long-term astronomical observations and direct visits to the moon have confirmed that there is no obvious magnetic field around the moon. The strength of the lunar magnetic field is less than11000 of the earth's magnetic field. There is no radiation belt on the moon like Earth and Jupiter. There is no water in any form on the moon, there is no atmosphere at all, and it is almost in a vacuum. According to the rocket sounding of the moon, there are 12 gravity anomaly areas on the front of the moon, which are called "gravity tumor" or "mass tumor". Most of the surface of the moon is covered by a layer of lunar dust and debris with different thicknesses.

The moon has no protective layer like the earth's atmosphere, and the surface of the moon is directly hit by meteoroids, so it will affect the chemical composition, fragment size, glass content and recrystallization degree of moon rocks to some extent. Volcanic eruption occurred widely in the early moon, spewing out a large amount of molten slurry, thus forming a vast lava plain on the moon.

The moon itself does not shine, but reflects sunlight. Its brightness varies with the angular distance between the sun and the moon and the distance between the earth and the moon. Its average brightness is 1/465000 of the brightness of the sun, and its brightness changes from 1/630000 to 1/375000. The average brightness at the full moon is-12.7, etc. Its average illumination to the earth is equivalent to the illumination of a 100 watt electric lamp at a distance of 2 1 meter. The surface of the moon is not a good reflector. Its average albedo is only 7%, and the other 93% is absorbed by the moon. The albedo of Guangdong Sea is even lower, about 6%. The albedo of the lunar highlands and craters is 17%, and it seems that the mountains are brighter than the moon sea.

Because there is no atmosphere on the moon, the heat capacity and thermal conductivity of lunar materials are very low, so the temperature difference between day and night on the surface of the moon is very large. During the day, where the sun shines vertically, the temperature is as high as 127 degrees Celsius. At night, the temperature can be reduced to minus 183 degrees Celsius. These values only represent the temperature on the surface of the moon. The temperature in the lunar soil can be measured by radio observation. The longer the wavelength of radio waves used, the deeper the temperature in the lunar soil can be detected. This measurement shows that the temperature in the deep soil on the surface of the moon rarely changes, which is precisely because of the low thermal conductivity of the material on the surface of the moon.

From the propagation of lunar seismic waves, we know that the moon also has layered structures such as shell, mantle and core. The outermost lunar shell is 60 ~ 65km thick. 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 lunar mantle is the lunar core. The temperature of the lunar nucleus is about 1000 degrees Celsius, which is probably in a molten state.

The structure on the back of the moon is quite different from that on the front. The Moon Sea occupies less land and there are many craters. The terrain is uneven. The longest and shortest radius of the moon is located on the back, some places are 4 kilometers longer than the average radius of the moon, and some places are 5 kilometers shorter (such as Van der Graf Depression). No "lump" was found on the back. The moon shell on the back is thicker than that on the front, with the thickest point reaching 150km, while the thickness of the moon shell on the front is only about 60km.

There are different opinions about the origin of the moon, and there are mainly three hypotheses, namely, capture theory, split theory and homology theory.

Capture said: the moon may be an asteroid that runs near the earth's orbit, and was later captured by the earth and became a satellite of the earth. Because the average density and chemical composition of the moon and the earth are very different, it may be formed by different substances in different parts of the solar protonebula. On the other hand, the average density of the moon is very close to that of meteorites and asteroids. Therefore, it is very likely that the asteroid was captured by the earth because it was close to the earth in its orbit. Some people think that this event happened 3.5 billion years ago and the whole process took 500 million years. After the moon was captured by the earth, due to the tidal force of the earth, the moon spewed out a lot of magma, forming moon sea basalt.

Split theory: in the early days of the formation of the solar system, the earth and the moon were originally a whole. At that time, the earth was still in a molten state, and the rotation speed was very fast, and the rotation period was only about 4 hours. Therefore, the tidal action period of the sun on the earth at this time is 2 hours. This period is just equal to the period of the earth's free swing, which produces * * * vibration, thus forming a series of slender expansion bodies on the equatorial plane, and finally splitting to form the moon. The Pacific Ocean is a relic left by the split of the moon. According to the calculation, the total angular momentum of earth-moon system, even with the angular momentum loss of several billion years, is not enough to split the earth and the moon. And the position of the moon is not on the equatorial plane of the earth. These facts differ and are difficult to explain.

Homologous theory: the earth and the moon are formed by the same planetary dust cloud. Their average density and chemical composition are different, because the metal particles in the original nebula have condensed long before the formation of planets. When the earth formed a planet, iron was the main component and iron was the core from the beginning. The moon, on the other hand, was formed after the formation of the earth, and it was composed of non-metallic substances left around the earth. These three hypotheses about the formation of the moon can more or less explain the basic facts such as the composition, density, structure and orbit of the moon. Apart from fission theory, capture theory and homology theory, which is more reasonable is still inconclusive.

According to the study of various thermal history models of the moon, the whole moon has experienced many local melts. In the early days of the moon's formation, most of the temperature of the moon reached 1000 degrees Celsius. 465.438 billion years ago, a large-scale magmatic movement occurred on the moon. In the process of magma separation, a lunar shell composed of plagioclase was formed, and the rest became the highland of the lunar surface. After the surface of the moon was consolidated, it melted locally in a deeper place, forming syenite melt. About 4 billion years ago, non-lunar basalt rich in radioactive elements and refractory elements was formed. The plagioclase highland has been exposed on the surface of the moon for a long time, and it has been constantly hit by meteorite materials, so it has been cut 1.5 ~ 2 km, and a large number of ancient impact craters have developed on the highland. Later, the highlands were cut and destroyed by a series of faults. 41~ 3.9 billion years ago, the moon was hit by a variety of large meteorites, which produced many moon-sea basins, that is, large-scale ring structures, the most typical of which was the rain-sea event. Both the moon and the oceans on the moon were formed in similar periods. The general order of the formation of the Moon Sea is: wine sea, Chenghai sea, wet sea, dangerous sea and rainy sea. The Moon Sea formed during the Yuhai period was filled and covered by basalt erupted in the later period about 3.9 ~ 3.65438 billion years ago. According to isotopic dating, the approximate filling time sequence is: Yuxi, Yu Haidong, Wet Sea, Dangerous Sea, Yuhai, Jinghai, Fenghai, Chenghai and Storm Ocean. Since then, the outline of the lunar surface has basically taken shape. Since 365,438+billion years, the evolution of the interior of the moon has been in a state of "stagnation", and external forces have played a leading role in the evolution history of the moon. Meteorites hit the surface of the moon, making the craters of the moon constantly form and increase. The radiation lunar crater formed during the solar period in erato, due to various functions of the lunar surface, its radiation pattern became inconspicuous or disappeared; The lunar crater formed by Copernicus has obvious radiation patterns.