Hua Feng slowly understood that because the orbit of the moon is elliptical, when the moon is at perigee, its rotation speed cannot catch up with the rotational speed, so we can see the area in the east of the moon reaching 98 degrees east longitude, on the contrary, when the moon is at apogee, the rotation speed is faster than the revolution speed, so we can see the area in the west of the moon up to 98 degrees west longitude.

This phenomenon is called Libra motion. And because the moon's orbit is inclined to the earth's equator, when the moon moves in the starry sky, the polar region will shake by about 7 degrees, a phenomenon called libra motion. In addition, since the Moon is only 60 Earth radius from the Earth, if the observer observes from moonrise to moonset, the observation point will have a displacement of the Earth's diameter, and the longitude of the Moon can be seen in the region with 1 degree of longitude on the moon.

The gravitational pull exerted by the Moon on the Earth is one of the causes of tidal phenomena. The Moon's orbit around the Earth is a synchronous orbit, and the so-called synchronous rotation is not strict.

Strictly speaking, the Earth and the Moon orbit around a common center of mass, which is 4,700 kilometers from the center of the Earth (i.e., 3/4 of the Earth's radius). Since the common center of mass is below the surface of the Earth, the movement of the Earth around the common center of mass appears to be "shaking". The reason why both the Earth and the Moon rotate in a clockwise direction when viewed from the south pole of the Earth, and that the Moon orbits the Earth in a clockwise direction, and that even the Earth revolves around the Sun in a clockwise direction.

The origin of the moon is inconsistent. There are three major schools of thought about the origin of the moon in history. In the later period, on the basis of various theories, combined with new research results, the "Great Collision Theory" was newly formed.

This was one of the earliest hypotheses to explain the origin of the moon. As early as 1898, George Darwin, the son of the famous biologist Charles 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 because the earth rotated too fast, a part of the earth's material was thrown out, and these materials separated from the earth to form the moon, and the big crater left on the earth is the Pacific Ocean.

This view was quickly opposed by some. They believed that with the speed of the Earth's rotation, it was impossible to throw a piece of that size out. Furthermore, if the Moon was thrown by the Earth, then the material composition of the two should be the same. However, through laboratory analysis of rock samples brought back from the moon by the Apollo 12 spacecraft, it was found that the two were very far apart. The age of the rocks on the surface of the moon is extremely ancient, the age of the rocks on the surface of the whole moon is between 30 and 4.2 billion years, the age of the oldest rocks on the surface of the earth is limited to the 3.8 billion years old ancient metamorphic rocks exposed in individual areas, and the age of the rocks on the Pacific Ocean floor is extremely young, which is completely contrary to the theory of "splitting theory".

This hypothesis holds that the Moon was originally just a moon-sized asteroid in the solar system, and at one point, because it orbited near the Earth, it was captured by the Earth's gravity and never left the Earth again. There is also a view close to the capture theory that the Earth is constantly accreting the material that has entered its orbit, and over time, more and more things are accused, and eventually the Moon is formed. However, some people pointed out that on a planet as large as the moon, the earth may not have that much power to capture it.

This hypothesis holds that both the Earth and the Moon are diffuse nebulae material in the solar system, rotating and accretion in almost the same region of the solar nebula, while forming objects of different sizes. In the process of accretion, the Earth correspondingly a little faster than the Moon, becoming the "older brother". This assumption is also challenged by objective facts. Through laboratory analysis of rock samples brought back from the moon by the Apollo spacecraft, the average chemical composition of the Earth and the Moon is very different, and it has been found that the rocks of the Moon are also much older than the rocks of the Earth.

This hypothesis holds that in the early stage of the evolution of the solar system, a large number of "stars" were formed in the space of the solar system, and a celestial star equivalent to 0.14 times the mass of the earth was formed first, and the stars grew and merged to form a primitive earth through collision and accretion with each other. In the process of their respective evolution, these two celestial bodies formed a metal core dominated by iron and a mantle and crust composed of silicate, respectively. Since these two celestial bodies are not far apart, there is a good chance of encountering.

By chance, the small celestial body crashed into the Earth at a speed of about 5 kilometers per second. The violent collision not only changed the state of motion of the Earth and tilted the Earth's axis of rotation, but also caused the small celestial body to be fractured by the impact, the silicate crust and mantle were heated and evaporated, and the expanding gas flew away from the Earth with a large amount of shattered dust at great speed. The material that flies away from the Earth is mainly composed of the mantle of the collider.

The vast majority of the earth's mantle and crust materials that have been hit by the huge impact are heated and evaporated, and the expanding gases fly away from the earth with a large amount of crushed dust at a great speed. The metal core, which separated from the mantle when the impactor ruptures, is slowed down by the gas that expands and flies away, and is accretion to Earth in about 4 hours. The gas and dust that fly away from the Earth are not completely separated from the gravitational control of the Earth, and combine through mutual accretion to form an almost molten Moon, or they first form a ring and then gradually accretion to form a partially molten Moon. This version is universally recognized.

This model clearly explains that the average composition of the Moon is lower than that of the Earth compared to the average composition of the Earth, which is relatively poor in iron and volatile. The isotopic composition of certain elements with contrasting characteristics of the "genes" of the Earth and the Moon, such as oxygen, chromium, titanium, iron, tungsten, silicon, etc., the measured values of the Moon and the Earth are consistent within the margin of error, indicating that the Moon is the "daughter" of the Earth. "For 4.5 billion years, the earth has carried its daughter by its side, and the moon has been accompanied by its mother, and it has experienced 4.5 billion long and ancient years together.

The moon itself does not emit light, only reflects sunlight. The brightness of the Moon varies with the angular distance between the Sun and the Moon and the distance between the Earth and the Moon, and the brightness of the Full Moon is more than ten times greater than that of the upper and lower strings.

The average brightness of the Moon is 1/465,000 of the Sun's, and the brightness varies from 1/630,000 to 1/375,000. The brightness at the Full Moon averages -12.7 magnitude. It gives an average of 0.22 lux to the earth, which is equivalent to the illuminance of a 100-watt electric light at a distance of 21 meters. The lunar surface is not a good reflector, its average albedo is only 9%, and the remaining 91% is absorbed by the moon. The albedo of the moon sea is even lower, about 7%. The albedo of the lunar highlands and craters is 17%, and it looks like the mountains are brighter than the lunar sea. [8]

The distance from the Moon to the Earth is about 1/400th of the distance from the Earth to the Sun, so the Moon is as big as the Sun when viewed from the Earth.

Because there is no atmosphere on the Moon, and the heat capacity and thermal conductivity of the lunar surface are very low, the temperature difference between day and night on the surface of the Moon is very large. During the day, the surface of the Moon can reach temperatures of up to 127°C where the sun shines vertically, and at night, the surface temperature can drop to -183°C. Measurements of the temperature in the lunar soil, which can be determined by radio observations, show that the temperature in the deeper layers of the lunar soil changes very little, precisely due to the low thermal conductivity of lunar materials.

From the propagation of lunar seismic waves, it is known that the moon also has a layered structure such as crust, mantle, and nucleus. The outermost layer of the lunar crust is on average about 60-64.7 km thick. Below the lunar crust to a depth of 1,000 km is the lunar mantle, which occupies most of the moon's volume.

Below the mantle is the lunar core, and the temperature of the lunar core is about 1000~1500°C, so it is likely to be in a molten state, and it is speculated that it is composed of Fe-Ni-S and dolerite materials.

The Earth and the Moon orbit each other, and the two celestial bodies rotate around a common center of gravity 1,600 kilometers below the surface. The birth of the moon has added a lot of new things to the earth.

As the Moon revolves around the Earth, its special gravitational pull attracts the water on Earth and moves with it to form a tidal wave. Tides helped the earth's early aquatic life to move to land.

A long, long time ago, the earth had a large temperature difference between day and night, and the temperature was between the boiling point and the freezing point of water, which was unsuitable for human habitation. However, the special influence of the moon and the gravitational pull of the earth's seawater have slowed down the earth's rotation, making the earth's rotation and revolution period tend to be reasonable, bringing us precious four seasons and reducing the temperature difference, so as to be suitable for human habitation.

The reason why the earth sees half of the moon is because the rotation period of the moon is strictly equal to the revolution period, is this a coincidence or is there an intrinsic connection? Let's take a look at the condition of the moons of the other planets in the solar system, we can find that the rotation period of most of the moons is strictly equal to the rotation period, and it seems that there seems to be some internal connection.

Under the long-term action of the Earth's gravity, the Moon's center of mass is no longer in its geometric center, but on the side close to the Earth, so the Moon's gravitational potential energy relative to the Earth becomes the smallest, and in the process of the Moon's rotation around the Earth, the Moon's center of mass is always facing the side of the Earth, as if the Earth is tied to the Moon with a rope. This is also the case with other moons of the solar system, so it is not a coincidence that the rotation period and the orbital period of the satellites are equal, but there are inherent factors.

Is there a relationship between earthquakes and the moon? This is a question that has puzzled scientists for nearly 100 years. Now, a joint research team composed of researchers from the Japan Institute of Disaster Prevention Science and the University of California, Los Angeles in the United States, has finally confirmed that the gravitational pull of the moon affects the tides of seawater, and the gravitational pull of the moon is likely to be the cause of earthquakes between the earth's tectonic plates when abnormal changes in the earth's crust accumulate a lot of energy. On October 22, the well-known American journal Science published their research results.

The natural rise and fall of the sea is often referred to as the tides. When the Moon reaches close to the Earth, called perigee, the synodic tide is even larger than usual, and the high tide at this time is called the perigee synodic tide.

Scientists have speculated for a long time about the effects of tides on earthquakes, but no one has yet demonstrated their effect on a global scale, and earthquakes and tides have only shown a clear connection between earthquakes and tides when they previously only occurred on the seafloor or near volcanoes. The researchers found that the occurrence of earthquakes is highly correlated with the tidal pressure in the fault plane, and the violent tide exerts enough pressure on the shallow fault plane to cause earthquakes. When the tide is large, reaching about 2-3 meters, 3/4 of earthquakes will occur, and the smaller the tide, the less chance of earthquakes occurring.

Elizabeth Göchlan, the author of the article, said: "The gravitational pull of the moon affects the ebb and flow of the seawater, and the earth itself is deformed by the gravitational pull of the moon. Violent tides play a large role in the initiation of earthquakes, which can be earlier or delayed due to pressure fluctuations caused by the tides. ”