The moon, commonly known as the moon, was called Taiyin, Xuantu, Chanjuan and Pan Yu in ancient times. It is the satellite of the earth and the fifth largest satellite in the solar system. The diameter of the moon is about a quarter of that of the earth, and its mass is about one-eighty-first of that of the earth. The moon is the most massive satellite, and its surface is covered with craters formed by small celestial bodies. The average distance between the moon and the earth is about 380,000 kilometers, which is about 30 times the diameter of the earth.

Brief introduction of the moon

The moon may have formed about 4.5 billion years ago. Shortly after the formation of the earth, there were several hypotheses about its origin. There is more factual evidence to support the "big collision origin theory" formed by the debris generated by the huge collision between the earth and the Martian-sized celestial body "Teia". There are a large number of huge impact craters on the front of the moon, which are filled with basalt lava flows from dark volcanoes, forming a vast plain called "Moon Sea". In fact, there is not a drop of water in the Moon Sea. There are bright and ancient plagioclase highlands and obvious impact craters between the periphery of the Moon Sea and the Moon Sea.

It is the brightest celestial body in the sky except the sun. Although it is very bright white, the surface is actually very dark, and the reflectivity is only slightly higher than that of old asphalt. The rotation period of the moon is equal to period of revolution (called tidal locking), so the moon always faces the same direction of the earth. The earth's ocean tides are mainly caused by the gravity of the moon.

Because the tidal force of the earth's ocean is opposite to the direction of the earth's rotation, the earth's rotation is always "braked" by an extremely weak force, which accumulates over time. There is ample evidence that the earth's rotation cycle is getting slower and slower, and the time of day is growing very slowly, increasing by 1 second in a few years. Due to the reaction of the earth, the moon is getting farther and farther away from the earth, about 3.8 cm away from the earth every year.

The ratio of the size of the moon to the sun is close to the ratio of the distance, which makes its apparent size almost the same as that of the sun. During a solar eclipse, the moon can completely cover the sun and form a total solar eclipse. The moon is the first alien object that human beings landed on. 1958 The lunar probes launched by the United States and the former Soviet Union failed. 2065438+In April 2008, NASA released a video made from data collected by lunar orbiter. The data in this video was collected by the Lunar Reconnaissance Orbiter (LRO) for nine years. Since June 2009, the probe has been observing the moon 50 kilometers above the surface of the moon, capturing unprecedented details on the surface of the moon.

Extended data

1. Crater

The name crater was coined by Galileo. It is a remarkable feature of the lunar surface, covering almost the whole lunar surface. The largest crater is Bailey crater near the South Pole, with a diameter of 295 kilometers, which is a little larger than Hainan Island. A small crater may even be a hole of dozens 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 surface area.

A Japanese scholar put forward the classification of impact craters in 1969, which can be divided into Cravi type (ancient impact craters are generally unrecognizable, and some impact craters have central peaks) and Copernicus type (young impact craters often splash a lot of rocks around the moon surface, and a large number of sputtered rock fragments are thrown on the moon surface at high speed, which changes the original topography of the moon surface and the structure and color of the surface soil, forming obvious.

2. Moon Sea

The dark part of the moon seen by the naked eye on the earth is actually a vast plain on the moon. Due to historical reasons, this misnamed name has been preserved. There are 22 identified moon seas, and some landforms are called "moon seas" or "moon-like seas". 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%, of which the largest "storm sea" covers an area of about 5 million square kilometers, almost the total area of nine French countries. 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.

References:

Baidu Encyclopedia-Moon