The moon is a spherical celestial body rotating around the earth, and it is also the only natural satellite of the earth. The moon may have formed about 4.5 billion years ago, shortly after the formation of the earth.

Huge impact craters filled with basalt lava flows from dark volcanoes are widely distributed on the front of the moon, forming a vast plain called "moon sea". In fact, there is not a drop of water in the "moon sea". Bright, ancient plagioclase highlands and striking impact craters are mixed between the periphery of the moon sea and the moon sea.

The moon is the brightest object in the sky except the sun. Although it is very bright, its surface is actually very dark, and its reflectivity is only slightly higher than that of old asphalt. Since the moon is very conspicuous in the sky, coupled with the regular phase changes of the moon, it has had a significant impact on human culture since ancient times, such as myths and legends, religious beliefs, philosophy, calendar compilation, literature and art, customs, and traditions.

The moon's rotation and revolution have the same period (called tidal locking), so the moon always faces the earth on the same side. The earth's ocean tides are mainly due to 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 subject to an extremely weak force, which "brakes" the earth's rotation. After long-term accumulation, there is sufficient evidence that the earth's rotation cycle is getting slower and slower, and the time of a day increases extremely slowly, about 1 second in a few years; Due to the earth's reaction, the moon is slowly farther and farther away from the earth, about 3.8 cm away from the earth every year. The ratio of the size and distance between the moon and the sun is similar, which makes its apparent size almost the same as that of the sun. During the solar eclipse, the moon can completely shield the sun and form a total solar eclipse.

The moon is the first extraterrestrial object that man has landed on. In 1958, the lunar probes launched by the United States failed. In 1959, the United States successfully launched the lunar probes "Moon" and "pioneer" respectively. In 1969, Apollo-11 of the United States realized the first manned landing on the moon, followed by apollo-12, 14, 15, 16 and 17. A total of 12 American astronauts landed on the moon to carry out scientific investigation, collect lunar samples and bury scientific instruments for long-term exploration of the moon. A total of 381.7 kilograms of lunar samples were brought back to the earth, which greatly increased mankind's understanding of the origin and evolution of the moon.