First, the division 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.
The moon is commonly known as the moon, also known as the Moon. The moon is the most obvious example of a natural satellite. In the solar system, except Mercury and Venus, all other planets are natural satellites. 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, except for the area near the edge of the moon, which is visible in the middle due to Libra movement, most areas on the back of the moon are invisible from the earth. 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 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 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.
data
The average orbital radius is 384,400 kilometers.
Track eccentricity is 0.0549.
Perigee distance is 363,300 kilometers.
The apogee is 405500 kilometers away.
The average revolution period is 27 days, 7 hours and 43 minutes 1 1.559 seconds.
The average speed is1.023km/s.
The inclination of the track varies from 28.58 to 18.28.
(The intersection angle with the ecliptic plane is 5. 145).
Ascending intersection right ascension 125.08.
The perigee angle is 3 18. 15.
Repeat stage/day 19.
The average distance between the moon and the earth is about 384,400 kilometers.
The retrogression period of intersection is 18.438+0 years.
The perigee movement period is 8.85 years.
The annual food consumption was 346.6 days.
Repeated lunar eclipse)181011day.
The average inclination of track and ecliptic is 5 9'
The average inclination between the equator and the ecliptic of the moon is132'
The equatorial diameter is 3476.2 kilometers.
The diameter of the pole is 3472.0km.
Flatness 0.00 12
The surface area is 3.976×10.7 square kilometers.
Flatness 0.00 12
The volume is 2.199×1010 cubic kilometer.
The mass is 7.349× 10 22kg.
3.350 times the average density of water.
Equatorial gravity acceleration1.62m/s2
1/6 of the earth
The escape speed is 2.38km/s.
The rotation period is 27 days, 7 hours and 43 minutes 1 1.559 seconds.
(synchronous rotation)
Rotational speed16.655m/s (on the equator)
The axial inclination varies between 3.60 and 6.69.
(The intersection angle with the ecliptic is 1.5424)
Albedo 0. 12
Apparent magnitude at full moon-12.74
Surface temperature (t) -233~ 123℃ (average -23℃)
Atmospheric pressure 1.3× 10- 10 kPa
Monthly cycle
Name value (d) definition
The moon and the moon are 27.32 1 66 1
The moon is 29.530 588 relative to the sun (moon phase).
The equinox 27.32 1.582 is relative to the vernal equinox.
Perigee month 27.554 550 relative to perigee
The node month 27.2 12 220 is relative to the rising node.
The history of human exploration of the moon
The first man-made object to reach the moon was the unmanned lander "Luna II" of the former Soviet Union, which crashed into the moon in September 1959. "Moon 3" photographed the back of the moon on1October 7 10 in the same year. Lunar 9 was the first lander to land on the moon. It sent back1photos taken on the moon on February 3, 966. In addition, "Moon 10" successfully entered the scheduled orbit on March 3 1 and 1966, 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 the Apollo 17 mission in February, 1972.
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" probe was launched on September 27th, 2003, and entered the orbit around the moon in June 165438+ 10+May, 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 ancient myths of China, there are countless stories about the moon. Like the goddess the Goddess Chang'e flying to the moon: It is said that in ancient times, there were ten suns in the sky, which made the earth smoke and the sea dry up, so ordinary people could not live any longer. This incident alarmed a hero named Hou Yi. He climbed to the top of Kunlun Mountain, drew his bow and shot down nine redundant suns in one breath. Hou Yi has made great achievements in the world and is respected and loved by the people. Many people with lofty ideals come here to study and be teachers. The treacherous and cunning Meng Peng also mixed in. Soon, Hou Yi married a beautiful and kind wife named Chang 'e. Besides hunting, Hou Yi spends all his time with his wife, and people envy this beautiful and loving couple. One day, Hou Yi went to Kunlun Mountain to visit friends and seek truth. He happened to meet the Queen Mother passing by and asked her for a bag of elixir. It is said that taking this medicine can instantly ascend to heaven and become immortal. However, Hou Yi was reluctant to leave his wife, so he had to temporarily give the elixir to Chang 'e. Chang 'e hid the medicine in the dresser's treasure chest, but Meng Peng saw it. Three days later, Hou Yi led his entourage out hunting, while Meng Peng with ulterior motives pretended to be ill. Shortly after Hou Yi led the crowd to leave, Meng Peng broke into the backyard of the back room with a sword in his hand, threatening Chang 'e to hand over the elixir. Chang 'e knew that she was no match for Meng Peng. In times of crisis, she made a decisive decision, turned around and opened the treasure chest, took out the elixir and swallowed it in one gulp. Chang 'e swallowed the medicine and immediately floated off the ground, rushed out of the window and flew into the sky. Because Chang 'e was worried about her husband, she flew to the nearest moon and became a fairy. In the evening, when Hou Yi came home, the maids cried and told what happened during the day. Hou Yi was surprised and angry, and drew his sword to kill the villain. Meng Peng has escaped. I was so angry that Hou Yi beat his chest and shouted. The grief-stricken Hou Yi looked up at the night sky and called the name of his beloved wife. At this time, he was surprised to find that today's moon is particularly bright and bright, and there is a swaying figure resembling Chang 'e. Hou Yi hurriedly sent someone to Chang 'e's favorite back garden, put on a table sweetmeats, and put on her favorite candied fruit to pay tribute to Chang 'e at the Moon Palace. After hearing the news that the Goddess Chang'e flying to the moon became an immortal, people set up an incense table under the moon and prayed for good luck and peace to the kind Chang 'e. Since then, the custom of Mid-Autumn Festival in Yue Bai has spread among the people. (This is just a way of saying "the Goddess Chang'e flying to the moon", and there are many different ways of saying it among the people. There is a saying that after Hou Yi shot down the sun, he was elected as the leader by the people. He became grumpy and killed people casually if he was unhappy. Chang 'e stole two pills of Dan medicine and prepared to take them with Hou Yi in the future to become immortal. But the most popular one is the one above, because people yearn for such an ending. )
WU GANG won.
There is also a legend about the Mid-Autumn Festival: It is said that osmanthus trees in front of Guanghan Palace on the moon are flourishing, reaching more than 500 feet. There is a man who often cuts down, but every time he finishes cutting, the cut place closes immediately. For thousands of years, this laurel tree can never be cut down. It is said that the person who cut down trees was WU GANG, a native of Xihe in Han Dynasty. He used to practice in heaven with the immortal, but when he made a mistake, the immortal demoted him to the moon palace, and * * did this futile work as punishment. In Li Bai's poems, there is a record that "if you want to be in the middle of the month, you will pay for the cold."
Zhu Yuanzhang and Moon Cake Uprising
It is said that eating moon cakes in the Mid-Autumn Festival began in the Yuan Dynasty. At that time, the broad masses of the people in the Central Plains could not bear the cruel rule of the ruling class in the Yuan Dynasty and rose up against the Yuan Dynasty. Zhu Yuanzhang joined forces with various resistance forces to prepare for the uprising. However, the officers and men of the imperial court searched very closely and it was very difficult to pass on the news. Liu Bowen, a military strategist, came up with a plan and ordered his men to hide a note with the words "Uprising on the 15th of August" in the cake, and then sent people to the uprising troops in various places to inform them to respond to the uprising on 15th of August. On the day of the uprising, all the rebels responded together, such as a single spark can start a prairie fire.
Soon, Xu Da captured the Yuan Dynasty and the uprising was successful. When the news came, Zhu Yuanzhang was overjoyed and quickly sent a message saying that all the soldiers should have fun with the people in the upcoming Mid-Autumn Festival, and they should give the "moon cakes" secretly sent at the time of the war as seasonal cakes to the ministers. Since then, the production of "moon cakes" has become more and more elaborate, and there are more and more varieties, such as dishes, which have also become good gifts. After the Mid-Autumn Festival, the custom of eating moon cakes spread among the people.
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.
Lunar motion
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.
Orbital motion of the moon
The moon moves around 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 moon revolves around the earth and rotates at the same time, with a period of 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. There are mainly the following reasons:
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.