1. A: July 21, 1969 on the moon, 2. A: U.S.. Armstrong. 3. A: The origin of the Moon is not clear: There are three main schools of thought on the origin of the Moon, but they are still undecided. Some scientists believe that the Moon was formed 4.6 billion years ago from cosmic gases and dust, just like the Earth; others believe that the Moon is a child of the Earth, split off from it. However, the data brought back by Helios on several occasions show that the composition of the Moon and the Earth are very different. Many scientists believe that the Moon was accidentally sucked into the gravitational pull of the Earth many years ago, and thus accidentally incorporated into the Earth's orbit. However, some cite celestial mechanics to argue against this theory. The Moon is Older Than Earth: To the surprise of scientists, 99% of the rocks brought back from the Moon are older than 90% of the old rocks on Earth. Moon rocks brought back by astronauts have been dated to be between 4.3 and 4.6 billion years old, which is equivalent to the history of the solar system. Soil is older than rock: the first American astronauts landed on the "Sea of Tranquility", the age of the soil is older than the rock. According to analysis, the difference between the two is 1 billion years. Chemical analysis shows that the soil on the Moon did not evolve from rocks, but may have come from somewhere else. Impacts make loud noises: During lunar explorations, the Lunar Landing Craft (LLB) and rockets hit the surface of the Moon on their way back. But each time, the Moon rang like a large gong or bell, and during the Apollo 12 exploration, the Moon's echoes lasted for four hours, a phenomenon that no scientist has been able to explain. Black shadow area has rare metals: on the Earth to see the moon, will see some black shadow, astronauts landed on this plain-like black shadow area, found it difficult to drill holes in its surface, after researching the soil samples here contain metal elements such as titanium, berkelium, yttrium, etc., scientists are very surprised, because these metal elements to be in a fairly high degree of heat --- 6,000 degrees Celsius above the melting and mixing in some of the surrounding rocks. The surrounding rock is mixed with some. Pure Iron Particles Don't Rust: The rock samples that astronauts brought back from the moon contained particles of pure iron that scientists believe did not come from meteorites. Some experts reported that these pure iron particles have not rusted for many years after they were brought back to Earth, which is the first time that pure iron does not rust in the scientific world. Smooth as a Mirror: Many parts of the Moon's surface are as smooth as a mirror. It seems to have been "scalded" by some unknown source of heat. Experts say it wasn't caused by a huge meteorite impact, but some scientists believe the heat from the sun was the main factor. Shocked by magnetism: Early studies of the moon said it had no magnetic field, but in recent years, after analyzing the moon's rocks, it became clear that they were strongly magnetic. However, if the moon's rocks really have a magnetic field, there should be an iron core, but nowadays the information tells us that such a huge hot core cannot exist inside the moon, nor can it get magnetic properties from the magnetic field of the earth, because if the moon wants to get magnetic properties from the earth, it has to be very close to the earth, and if it is, it is feared that the earth's center force will destroy it. Concentrates at the bottom of the crust: Space probes have brought back information that there are large concentrates under the moon's crust and that there is a force of attraction that causes spacecraft to tilt as they fly by. Scientists only know that this concentrate is a heavy, dense substance, but nothing else. A: Helium, atomic number 2, atomic weight 4.002602, is a rare gas. The name of the element comes from the Greek, the original meaning is "the sun". 1868, someone using a spectroscope to observe the surface of the sun, found a new yellow spectral line, and thought it belonged to the sun on an unknown element, so the name helium. Later, some people used inorganic acid to deal with pitchblende uranium ore to get a kind of inactive gas, and in 1895, the British scientist Ramsay used the spectrum to prove that it was helium. Helium has since been found in other ores, air and natural gas. Helium is found in very small amounts in the earth's crust, accounting for 23% of the universe by mass, second only to hydrogen. The amount of helium in air is 0.0005%. Helium has two natural isotopes: helium 3 and helium 4, and essentially all helium present in nature is helium 4. Helium is normally a colorless, odorless gas; melting point -272.2°C (25 atmospheres), boiling point -268.9°C; density 0.1785 g/l, critical temperature -267.8°C, critical pressure 2.26 atmospheres; solubility in water 8.61 cm? /kg of water. Helium is the only substance that cannot be solidified at standard atmospheric pressure. Liquid helium undergoes a sudden change in properties when the temperature drops to 2.18 K. It becomes a superfluid that can flow upward along the walls of the container, has a thermal conductivity 800 times that of copper, and becomes a superconductor; its specific heat capacity, surface tension, and compressibility are all anomalous. Helium is the least reactive element and forms essentially no compounds. Helium is used as a protective gas, as a working fluid in gas-cooled nuclear reactors, and as an ultra-low-temperature refrigerant. A: "Artificial Moon" will be put up at the beginning of the next century On February 5, 1999, the Russian "Progress M-40" cargo spacecraft re-entered the atmosphere. This time, however, in addition to the trash brought back from the Mir space station, the "artificial moon", code-named "Flag 2.5", which failed to start as planned, was burned up. The atmosphere in Moscow's space command center is subdued. The atmosphere in Moscow's Space Command Center was depressing, and the specialists involved in the Flag program were helplessly swallowing the bitter taste of failure. People all over the world could not help but sigh with regret. February 4 is an unusual day, according to the arrangement of the Russian Space Agency, the "Mir" space station carried out a unique "artificial moon" experiment, the experiment code name "Flag 2.5 The experiment was code-named "Flag 2.5". This is the world's first controllable solar reflector device, if all goes well, "Mir" cosmonauts can control the attitude of the mirror, so that the reflected sunlight is fixed in a particular region of the Earth, the sun's rays will shine 24 hours a day on the earth, to realize the people's hearts, "the sun never sets! The sun will shine 24 hours a day, realizing people's wish that "the sun will never set". At noon, the Progress M-40 cargo spacecraft loaded with the solar reflector followed the instructions of the ground command center to leave the Mir space station. After several maneuvers, the ship flew to a position 400 meters from Mir. Maneuvered by the two cosmonauts on board Mir (Padalka and Avdeyev), the solar mirrors on the docking port of the spacecraft began to rotate and attempted to deploy by centrifugal force. After only one minute, however, the Progress antennae suddenly and inexplicably opened up and hooked onto the 25-meter-long solar panels, and the cosmonauts tried to shake the mirrors to loosen them, but without success. On day 2, another attempt was made, which still failed. Both the ground commanders and the cosmonauts on the station were at a loss. The Russian space authorities decided to terminate the experiment because they believed that it would be fruitless to continue the experiment and that the cargo ship's prolonged flight in the vicinity of the Mir space station posed a threat to the safety of Mir, and they issued a command. The cargo spacecraft de-orbited and crashed into the atmosphere. The flag of the "artificial moon", which had been eagerly awaited, fell before it could be raised. According to the original plan, under the command of the astronauts, 8 mirrors like petals will slowly open in space. The eight petals of the frame is made of special high-strength ultra-lightweight plastic, coated with reflective aluminum film. This 25-meter diameter "artificial moon" has a total weight of less than 4 kilograms. If successfully deployed, a beam of sunlight will be cast from space in almost every country where the Mir station orbits, including Russia, France, the Czech Republic and Canada. The beam has a diameter of 5 to 7 kilometers at ground level. At night, this "sunlight" will be 5 to 10 times stronger than the moonlight, and people on the streets will be able to read books, play chess, and so on. The "artificial moon" was scheduled to orbit the Earth for 16 weeks, lasting about 24 hours, and then return to Earth with the "Progress" spacecraft filled with garbage from the "Mir" space station. The idea of reflecting sunlight for the benefit of mankind first appeared in the United States in the Columbus 500 program. The main content of the program was to create a solar sailboat powered by the thrust of the solar wind in order to fly to Mars via the Moon within a few years by virtue of the thrust of the solar wind. Russia, Japan and France are all very interested in the solar sailing program and have conducted research in this area. Russia presided over the development of solar sailboat work of the famous designer Vladimir Thromyatnikov sudden whim, came up with the use of ultra-thin reflective film manufacturing space lighting system of high technology. This system could first of all solve the problem of illumination in the high latitudes of Russia, where every year there is a period of long and difficult polar night, which is suffered by people who long for light. In addition, the space reflector can be used to illuminate areas where natural disasters, such as earthquakes or floods, have occurred, so that rescue work can be carried out at night. Since space mirrors bring light to mankind without bringing pollutants such as carbon dioxide to the earth's environment, they are considered an environmentally friendly energy source, and from this point of view, they deserve to be strongly advocated. However, a few people have raised objections to it, biologists worry that it will change the biological patterns of certain regions of the Earth; astronomers are strongly opposed to it because of its possible impact on astronomical observations. But Russian scientists thought the "artificial moon" was a very useful experiment. A series of programs, code-named "Flag," were implemented. February 4, 1993, Russia in the "Peace" space station on the use of the "Progress" cargo spacecraft for a code-named "Flag 2" of the The "artificial moon" experiment was conducted on board the "Mir" space station using the "Progress" cargo spacecraft, code-named "Flag 2", which unfurled the first solar sail of mankind. The experiment was a great success. "The Flag 2 sunlight reflector was housed in a mirror package consisting of eight ultra-thin coated aluminum flaps only 5 microns thick, connected by 32 wires. The mirror package was mounted on the Progress M-15 cargo spacecraft. After the spacecraft left the space station to reach the designated location, the cosmonauts on board the Mir issued a command, the mirror package opened, "Flag 2" rely on their own centrifugal force generated by the placement of the spread out, becoming a round of "artificial moon This "moon" was opened by the astronauts on board the spacecraft. This "moon" diameter of 20 meters, the ground spot diameter of 4000 meters. When it ran over Western Europe, it was the middle of the night, and it generously shot the first rays of sunlight to the ground. Unfortunately, due to thick cloud cover, this unusual phenomenon could not be observed in detail. However, many people reported having seen a beam of light. At the end of the test, the reflector was separated from the Progress spacecraft. In the clear Canadian night sky, people could clearly see the Flag 2 "flying" in the sky, and some people even took pictures of it. Prior to this, Russia conducted ground-based engineering experiments with the Flag 1 sunlight reflector. The efforts of Russian scientists in the quest for light are evident to the world. The failure of the Flag 2.5 sunlight-reflecting experiment, for which Russian scientists have been preparing for five or six years, will be a major setback in the process of developing a space lighting system. In fact, compared with the "Flag 2" experiment, the "Flag 2.5" sunlight-reflecting experiment has been greatly improved, both in terms of the test method and the structure of the light reflector itself. Russian scientists said that in the near future will not carry out similar "artificial moon" experiment. But this does not mean that Russia has given up research in space lighting systems. Sources say that Russia intends to develop a 70-meter-diameter solar reflector in the "Flag 3" program, which is expected to be test-flown at the beginning of the next century. It is also expected that solar sails with an area of more than 1 million square meters may be assembled on the completed ISS between 2008 and 2010. Once assembled, the solar sails will enter the northern hemisphere with the help of an orbiting tow cable. A space lighting system consisting of three to four such solar reflectors may be constructed by 2015, flooding high latitudes, which have long craved light, with sunlight. 6. a: 384,401 kilometers 7. a: We know that the moon revolves around the earth. One revolution is one month in our lunar calendar. It can be figured out that one of the positions in each revolution is exactly between the Earth and the Sun, that is, the sun, moon and earth into a line. This moment is the "first day of the month", which must be the first day of the month in our lunar calendar. Another position is exactly on the extension line between the sun and the earth, which is the line between the sun, the earth and the moon. This time is "Wang", which is around the fifteenth day of the lunar calendar. You may think, so not every "solstice" when the moon to cover the sun and solar eclipse? No, it won't. Because the moon's orbit around the earth (the white path) and the earth's orbit around the sun (the ecliptic) have an angle of almost 5°. Therefore, the Moon may be above or below the Sun at the time of the "solstice". But we know that solar eclipses must occur on the first day of the month. But we know that solar eclipses must occur at the time of the first day of the month, and lunar eclipses must occur at the time of the first day of the month. A: The so-called lunar sea is not the ocean above the Moon. The largest lunar sea is the "stormy ocean". As a matter of fact, no liquid water has been found on the Moon so far. The reason it is called a "sea" is that early observers noticed that parts of the lunar surface were dark. Without a clear view of the lunar surface at the time, observers, based on their knowledge of the Earth, assumed that this area was an ocean, and thus had a lower reflectance than the rest of the Moon. In contrast, the other brighter areas were called lunar land. In addition, there are also "Lunar Lakes" called lakes, "Lunar Bays" called bays, and "Lunar Swamps" called marshes. The largest lunar sea is called the Stormy Ocean, which is located in the northeastern part of the Moon and covers an area of 5 million square kilometers, which is equivalent to the area of 9 France. The Rainy Sea covers an area of about 900,000 square kilometers, while the Quiet Sea in the center of the Moon's surface covers an area of about 260,000 square kilometers. The area of the Moon Sea accounts for 16% of the total area of the lunar surface. The American "Apollo" spacecraft has landed on the Moon Sea six times, such as "Apollo-11", "Apollo-17" landed in the Sea of Tranquility, "Apollo-12" landed in the Sea of Tranquility, "Apollo-17" landed in the Sea of Tranquility, "Apollo-17" landed in the Sea of Tranquility. "Apollo 12 landed in the stormy ocean. The astronauts, wearing spacesuits, walked on the "sea" and left a trail of footprints about 3 centimeters deep. The dust on the surface of the Moon was found to be a fine, almost grayish powder, somewhat like sticky charcoal shavings. A: The Moon is large. Studies have shown that Earth rocks are at most 4.5 billion years old, while some Moon rocks are 5 billion years old, and the Moon is actually a companion of the Earth. The diameter of the Moon is 3,476 kilometers, about 3/11 of the diameter of the Earth. 10. A: On the fifteenth and sixteenth days of the lunar calendar, the Moon orbits in the direction opposite to the Sun. If the centers of the Earth and the Moon are roughly in the same line, the Moon enters the Earth's umbra and a total lunar eclipse occurs. If only part of the Moon enters the Earth's umbra, a partial lunar eclipse is produced. When the Moon enters the Earth's penumbra, it is supposed to be a penumbral eclipse, but it is not called a lunar eclipse because it diminishes so little that it is not easy to detect, so there are only two kinds of lunar eclipses: total and partial. Lunar eclipses occur at the first full moon, but not every first full moon has a lunar eclipse, for the same reason that solar eclipses do not occur at every first lunar month. A: Meteorites. Under normal circumstances (such as the Earth, the outer atmosphere, when the meteorite through the atmosphere, and the air friction, this heat is enough to burn off the meteorite, there are a few very large or contain a special substance, not sufficiently burned off, fell to the ground) and the moon has no atmosphere, the meteorite fell directly to the surface of the moon, the formation of such a crater, look at the shape of whether it looks like a stone! when it falls to the surface. The Moon The front and back of the Moon: Front:
Back:/eriol1987/pic/item/ddff85359fbaf71191ef3960.jpg Physical Description: The Moon is commonly known as the Moon, also known as the Tai Yin. The age of the Moon is also about 4.6 billion years, and it is closely related to the shape of the Earth. The Moon also has a layered structure of shell, mantle and core. The outermost lunar crust is about 60-65 kilometers thick on average. Below the crust, at a depth of 1,000 kilometers, is the mantle, which makes up most of the volume of the Moon. Below the mantle is the nucleus, which has a temperature of about 1,000 degrees Celsius and is probably in a molten state. The Moon has a diameter of about 3,476 kilometers, which is 3/11 of the Earth's. It has a volume of only 1/49 of the Earth's, a mass of about 735 billion billion tons, which is equivalent to 1/81 of the Earth's mass, and the gravity at the surface of the Moon is almost equivalent to 1/6 of the Earth's gravity. There are both shadowy parts and bright regions above the Moon. Early astronomers, when observing the Moon, thought that the darkened areas were covered with seawater, so they called them " seas ". Famous ones are the Sea of Clouds, the Wet Sea, and the Sea of Tranquility. And the bright parts are mountain ranges, where there are layers of mountains and ranges of hills, and everywhere there are starry craters. Bailey's Crater, located near the South Pole, is 295 kilometers in diameter and could fit the entire island of Hainan. The deepest mountain is Newton's Crater, which is 8,788 meters deep. In addition to craters, there are also ordinary mountains on the lunar surface. High mountains and deep valleys appear on top of each other. The front side of the Moon is always facing the Earth. On the other hand, most of the Moon's backside is not visible from the Earth, except for the area near the edge of the Moon's surface, which is occasionally visible due to the movement of the celestial scales. In the absence of probes, the back of the Moon has remained an unknown world. One of the unique features of the Moon's backside is that it is almost devoid of the darker lunar features like the lunar sea. And when a probe operates to the back of the Moon, it will not be able to communicate directly with Earth. Orbital Data Mean Orbital Radius 384,400 km Orbital Eccentricity 0.0549 Perigee Distance 363,300 km Apogee Distance 405,500 km Mean Rotation Period 27 days, 7 hours, 43 minutes, and 11.559 seconds Mean Rotation Speed 1.023 km/s Orbital Inclination varies between 28.58° and 18.28° (Intersection with ecliptic plane 5.145°). 5.145°) Ascending node longitude 125.08° Perigee angle 318.15° Physical characteristics Equatorial diameter 3,476.2 km Diameter at the poles 3,472.0 km Flatness 0.0012 Surface area 3.976×107 sq. km Flatness 0.0012 Volume 2.199×1010 cubic kilometers Mass 7.349×1022 kilograms Average density 3.350 times the gravitational acceleration at the equator. 3.350 times Equatorial gravitational acceleration 1.62 m/s2 1/6th of Earth's escape velocity 2.38 km/s Rotation period 27 days, 7 hours, 43 minutes, 11.559 seconds (synchrotron rotation) Rotation speed 16.655 m/s (at the equator) Inclination of the axis of rotation varies between 3.60° and 6.69° (intersection with the ecliptic is 1.5424°) Albedo 0.12 at full moon Apparent magnitude -12.74 Surface temperature (t) -233~123°C (mean -23°C) Atmospheric pressure 1.3×10-10 kPa The Moon orbits the Earth in about one lunar month while moving about half a degree per hour relative to the background stars, i.e., about the same apparent diameter as the lunar surface. Unlike other satellites, the Moon's orbital plane is closer to the ecliptic than to the Earth's equator. The time required for the Moon to orbit around the Earth (lunar rotation) for one week relative to the background stars is called a sidereal month; and the time required between a new moon and the next new moon (or between two identical moon phases) is called a lunation. The lunation is longer than the sidereal month because the Earth itself advances some distance in its orbit around the Sun during the Moon's orbit. Because the Moon's rotation period is exactly the same as its revolution period, we can only see the Moon always facing the Earth in the same direction. Since the early days of the Moon's formation, the Moon has been subjected to a torque that causes its rotation to slow down, a process known as tidal locking. As a result, part of the angular momentum of the Earth's rotation is converted into the angular momentum of the Moon's revolution around the Earth, with the result that the Moon is moving away from the Earth at a rate of about 38 millimeters per year. At the same time, the Earth's rotation becomes slower and slower, and the length of the day becomes 15 microseconds longer and longer each year. The gravitational pull of the Moon on the Earth is one of the causes of tidal phenomena. The Moon's orbit around the Earth is synchronous, and the so-called synchronous rotation is not strict. Since the Moon's orbit is elliptical, when the Moon is at perihelion, its rotation does not catch up with its revolution, so that we can see the eastern part of the lunar surface up to 98 degrees east longitude, while on the contrary, when the Moon is at aphelion, its rotation is faster than its revolution, so that we can see the western part of the lunar surface up to 98 degrees west longitude. This phenomenon is called libration. Since the Moon's orbit is inclined to the Earth's equator, the polar regions of the Moon make a wobble of about 7 degrees when the Moon moves in the starry sky, a phenomenon known as libration. Furthermore, since the Moon is only 60 Earth radii away from the Earth, if the observer observes from moonrise to moonset, the observation point will have a displacement of one Earth diameter, and the area of one degree of longitude on the Moon's surface can be seen more often. This phenomenon is called libration. Strictly speaking, the Earth and the Moon orbit around the *** homogeneous center of mass, which is 4,700 km from the center of the Earth (i.e., at 2/3 of the Earth's radius). Because the center of mass is below the Earth's surface, the Earth's motion around the center of mass appears to be a "wobble". When viewed from the north pole of the earth, both the earth and the moon rotate in a clockwise direction; and the moon also orbits around the earth in a clockwise direction; and even the earth rotates around the sun in a clockwise direction. Many people do not understand why the values of the inclination of the Moon's orbit and the inclination of the Moon's rotation axis vary so much. In fact, the orbital inclination is relative to the central body (i.e., the Earth), while the rotational axis inclination is relative to the satellite (i.e., the Moon) itself on the orbital plane. Whereas this definitional convention is well suited to the general case (e.g., the orbits of artificial satellites) and is fairly constant in value, this is not the case for the Moon. The Moon's orbital plane (the plane of the White Way) maintains an angle of 5.145 396° with the plane of the ecliptic (the plane of the Earth's orbital revolution), while the Moon's axis of rotation is at an angle of 1.5424° to the normal to the plane of the ecliptic. Because the Earth is not perfectly spherical, but is more elevated at the equator, the leucopause is in constant motion (i.e., the intersection with the ecliptic rotates clockwise), completing one week every 6793.5 days (18.5966 years). During this period, the angle of the White Way Plane with respect to the Earth's equatorial plane (which is inclined to the ecliptic at 23.45°) varies from 28.60° (i.e., 23.45° + 5.15°) to 18.30° (i.e., 23.45° - 5.15°). Similarly, the angle between the Moon's rotation axis and the white channel plane varies between 6.69° (i.e. 5.15° + 1.54°) and 3.60° (i.e. 5.15° - 1.54°). These changes in the Moon's orbit in turn affect the inclination of the Earth's rotational axis, causing it to oscillate by ±0.002 56°, known as a translational motion. The two points of intersection of the white and ecliptic planes are called lunar nodes - the ascending node (north point), through which the Moon passes north of the ecliptic plane, and the descending node (south point), through which the Moon passes south of the ecliptic. A solar eclipse occurs when the new Moon is exactly on the nodes, and a lunar eclipse occurs when the full Moon is exactly on the nodes; Moon's Cycle Name Value (d) Definition Sagittarius Moon 27.321 661 Relative to background stars Solstice Moon 29.530 588 Relative to the Sun (lunar phases) Equinox Moon 27.321 582 Relative to equinox Perigee Moon 27.554 550 Relative to the perigee Node Moon 27.230 588 Relative to the Sun (lunar phases) Perigee month 27.554 550 relative to perigee Nodal month 27.212 220 relative to ascending node Other characteristics of the Moon's orbit Name Numerical value (d) Definition Repeat phase/day 19 years Mean Moon-Earth distance ~384 400 km Perigee distance ~364 397 km Apogee distance ~406 731 km Mean orbital eccentricity 0.0549003 Nodal recession period 18.61 years Perigee period 18.61 years Perigee motion period 8.85 years Eclipse year 346.6 days Repeat eclipses 18 years 10/11 days Mean inclination of the orbit to the ecliptic 5°9' Mean inclination of the Moon's equator to the ecliptic 1°32' Exploration of the Human Moon Landing: The first manmade object to reach the Moon was the unmanned Soviet Lunar Lander Lunar 2 which hit the surface on September 14, 1959 and was the first to reach the Moon. The first man-made object to reach the Moon was the Soviet unmanned lander Luna 2, which hit the lunar surface on September 14, 1959 Luna 3 photographed the back of the Moon on October 7 of the same year. Luna 9 was the first soft-landing vehicle on the Moon, and on February 3, 1966, it returned photos taken from the lunar surface. In addition, Luna 10 was successfully orbited on March 31, 1966, becoming the first artificial satellite on the Moon. During the Cold War, the United States of America and the former Soviet Union had always wanted to be ahead of each other in space technology. This space race came to a climax on July 20, 1969 when the first man landed on the moon. Neil Armstrong, commander of Apollo 11 in the United States of America, was the first man to set foot on the Moon, while Eugene Cernan, a member of the December 1972 Apollo 17 mission, was the last man to stand on the Moon. See: List of Lunar Astronauts The Apollo 11 astronauts left a 9-inch by 7-inch stainless steel plaque on the surface of the Moon to commemorate the landing and to provide some information about other organisms that might discover it. The plaque depicts both sides of the Earth and is signed by the three astronauts and by then-President Nixon of the United States of America. Six Helios missions and three unmanned Luna missions (Luna 16, 20, 24) brought rock and soil samples from the Moon back to Earth. In February 2004, the President of the United States of America, George W. Bush, proposed to send another man to the Moon before 2020. The European Space Agency and the People's Republic of China also have plans to launch probes to the Moon. The European Smart 1 probe was launched on September 27, 2003, and on November 15, 2004, it entered orbit around the Moon. It will survey the lunar environment and produce X-ray maps of the lunar surface. The People's Republic of China has also been actively pursuing a lunar exploration program and seeking the feasibility of exploiting the Moon's resources, in particular the helium isotope helium-3, which is expected to be a future energy source for the Earth. For more information on the People's Republic of China's lunar exploration program, see the entry for Chang'e Project. Japan and India are not far behind. Japan has already set out a preliminary plan for future missions to the Moon. Japan's Aerospace Exploration Agency (Aerospace Exploration Agency) has even begun planning for a manned lunar base. India will launch Chandrayan, an unmanned lunar probe, first. Myths about the Moon: In the ancient mythology of the People's Republic of China, there are countless stories about the moon. In ancient Greek mythology, the name of the goddess of the moon was Artemis, who was the twin sister of Apollo, the god of the sun, and who was also the goddess of the hunt. The Moon's astronomical symbol resembles a curved crescent, symbolizing Artemis' sacred bow. The Moon is the only natural satellite of the Earth and is the closest celestial body, its average distance from the Earth is about 384,401 kilometers. Its average diameter is about 3,476 kilometers, which is slightly larger than 1/4 of the Earth's diameter. The surface area of the Moon is 38 million kilometers, which is not as large as the area of our Asia. The mass of the Moon is about 735 billion billion tons, which is equivalent to 1/81 of the mass of the Earth, while the gravity on the surface of the Moon is almost equivalent to 1/6 of that of the Earth. Orbital Motion of the Moon The Moon orbits the Earth in an elliptical orbit. The plane of this orbit intercepts a great circle on the celestial sphere called the "white channel". The plane of the White Way does not coincide with the celestial equator, nor is it parallel to the plane of the ecliptic, and its spatial position is constantly changing. It has a period of 173 days. The rotation of the Moon The Moon rotates around the Earth at the same time, with a period of 27.32166 days, which is exactly a sidereal month, so we cannot see the back of the Moon. This phenomenon, which we call "synchronized rotation", is almost universal in the world of satellites. It's generally thought to be the result of the long-term tidal action of the planets on the satellites. The libration is a wonderful phenomenon that allows us to see 59% of the Moon's surface. This is mainly due to the following reasons: 1. the mismatch between the rotational speed and the angular speed of rotation in different parts of the elliptical orbit. 2. the mismatch between the White Way and the equator. 2. the angle of intersection of the White Way and the Equator. Physical Conditions of the Moon - The main topography of the lunar surface is: Craters The name was given by Galileo. It is a prominent feature of the lunar surface and covers almost the entire surface. The largest crater is Bailey's crater near the South Pole, 295 kilometers in diameter, a little larger than Hainan Island. Smaller craters may even be craters of a few tens of centimeters. There are about 33,000 that are no smaller than 1,000 meters in diameter. That's 7-10% of the moon's surface area. A Japanese scholar proposed a classification of craters in 1969, which is divided into Clavian (old craters, generally unrecognizable, some with mountains within mountains), Copernican (young craters, often "radial", with concentric circular segments in the inner wall and a central peak in the center), and Archimedean (rings with lower walls, probably evolved from Copernicus). Archimedean (lower ring walls, probably derived from Copernican) Bowl and Dimple (small craters, some less than a meter in diameter). The dark portion of the Moon's surface visible to the naked eye is actually a broad plain on the Moon's surface. For historical reasons, this misnomer has survived to the present day. Twenty-two lunar seas have been identified, in addition to some terrains known as "lunar seas" or "lunar-like seas". The vast majority of the 22 recognized ones are located on the front side of the Moon. Three are on the backside and four are on the fringes. Slightly more than 50% of the Lunar Seas are on the front side, and the largest of them, the "Stormy Ocean", has an area of more than 5 million square kilometers, which is almost the size of nine French countries combined. Most of the lunar seas are roughly circular or oval and are surrounded by mountain ranges, but there are also some seas that are connected. In addition to the "sea", there are five terrain and similar "lake" ---- dream lake, dead lake, summer lake, autumn lake, spring lake, but some lakes than the sea is also large, such as the dream lake area of 70,000 square kilometers, than the steam sea and so on is also much larger. The part of the Lunar Sea that extends to the land is called a "bay" or "marsh," and it is located on the front side. There are five bays: Dew Bay, Summer Bay, Central Bay, Rainbow Bay, and Meigetsu Bay; and there are three marshes: Rot Marsh, Epidemic Marsh, and Yume Marsh, but there is no difference between a marsh and a bay. The terrain of the Moon Sea is generally low, similar to the basin on the Earth, the Moon Sea is 1-2 kilometers lower than the average level of the Moon, and the southeastern part of the individual lowest sea is even 6,000 meters lower than the surrounding area of the Rainy Sea. The moon's surface also has a lower albedo (a physical measure of the ability to reflect sunlight), making it appear darker. The area of the Moon's surface above the lunar sea is called the lunar terrestrial area, which is generally 2-3 kilometers above the level of the lunar sea and appears brighter because of its high albedo. On the front side of the Moon, the Moon's landmass is roughly equal in size to the Moon's sea.