Astronomy

This article focuses on the origin of the solar system, introducing the historical background of the "Kant-Laplace nebular hypothesis" and the core content of the modern nebular hypothesis, which is currently widely accepted by the scientific community.

This article answers the question of what the main members of the solar system are, and introduces the characteristics and related situations of various members of the solar system, including planets, dwarf planets, asteroids, satellites, comets, meteorites, and interplanetary matter.

This article explains why the sun and the moon appear to be about the same size, pointing out that this is a coincidence: the sun's diameter is 400 times that of the moon, and the distance between the sun and the Earth just happens to be 400 times that between the moon and the Earth, so their apparent sizes are similar. At the same time, because both their orbits are elliptical, changes in distance cause slight differences in apparent size, which can be reflected in the different phenomena of total solar eclipses and annular solar eclipses. In addition, due to tidal friction between the Earth and the moon, the moon is gradually moving away, and the types of solar eclipses visible on Earth vary in different periods.

This article focuses on the question of "why solar eclipses are rarer than lunar eclipses", introducing the annual frequency of solar and lunar eclipses, explaining that people perceive solar eclipses as rarer because the visible range of solar eclipses is much smaller than that of lunar eclipses, and also mentioning the spectacular phenomena such as Baily's beads and diamond rings that occur during total solar eclipses.

This article answers the question of why there are solar and lunar eclipses, introduces the formation principles and specific types of solar and lunar eclipses, and describes the history of human observation of solar and lunar eclipses and the laws of their recurrence cycles.

This article focuses on the question of "why there are so many 'seas' on the moon", introducing the naming origin, appearance characteristics, distribution and quantity of lunar seas, explaining that landforms such as lunar lakes, swamps, and bays are essentially no different from lunar seas, and explaining the formation of lunar seas caused by large celestial bodies impacting the moon, triggering internal magma eruptions and covering the impacted depressions. It also mentions that lunar seas are a huge titanium-iron ore repository, and in the future, humans can rationally develop and utilize the relevant mineral resources on the moon.

This article focuses on the question of "why lunar material is 'lighter' than terrestrial material". It explains that the mass of the Moon is only 1/80 of that of the Earth, and its radius is about 1/4 of that of the Earth, so its density (about 3.3 g/cm^3) is lower than that of the Earth (about 5.6 g/cm^3). The main reason for this phenomenon is the different internal structures of the Earth and the Moon. The article also introduces the layered structure and composition of the Moon's crust, mantle, and core, and points out through the comparison of the densities and volumes of the Earth and the Moon that the density of the Moon's iron core is lower than that of the Earth's and occupies a smaller proportion of the volume, so the average density of the Moon is lower

This article focuses on the question of why the Earth has a moon as its companion, introduces the basic parameters of the moon as the Earth's natural satellite, and explains three imperfect hypotheses about the formation of the moon: the Earth's splitting hypothesis, the Earth's capture theory, and the co-formation theory. It particularly elaborates on the specific content of the Big Impact Theory, which is currently the most popular and widely accepted by most astronomers and supported by evidence from chemistry, geology, and other fields. It also points out that with the advancement of technology, the details of the moon's origin will eventually be fully revealed.

This article focuses on the theme of "Why does 'Chang'e' also need to go to the moon", and introduces the launching background of China's "Chang'e Project" lunar exploration program, its four major scientific goals, the three-step implementation plan of "orbiting, landing, and returning", as well as the launch process, mission execution, and exploration results of the two lunar probes, "Chang'e No.1" and "Chang'e No.2".

This article focuses on the theme of "Why did Americans decide to land on the moon?" It introduces the background of the United States initiating and advancing the "Apollo" lunar landing program after being stimulated by the Soviet Union's Yuri Gagarin becoming the first person to fly into space. It details the implementation process of the "Apollo 11" lunar landing mission, the overall development of the entire "Apollo" program and its scientific research achievements, as well as the important impact of the program on the United States' aerospace technology, economy, and other fields.

This article focuses on the question of "why the surface of the moon looks like a pockmarked face", explaining that the "pockmarked face" of the moon's surface is due to the widespread crater formations. Since the moon lacks an atmosphere and weathering processes, the craters formed by meteorite impacts can be preserved for a long time. The article also introduces the number of lunar craters, their naming rules, the largest Bell Crater, and other lunar features such as the Apennine Mountains, which are also formed by impacts on the moon.

This article focuses on the question of "Is there water on the moon?" It introduces that the lunar rocks collected during the US "Apollo program" were extremely dry in the early days. People once believed that the moon had no connection with water except for the names of places related to water. However, the lack of water on the moon would make it extremely costly to build a lunar base by transporting water from Earth. Subsequent research found that the angle between the lunar equator and ecliptic is only about 1.5°. There are extremely cold permanent shadow zones (low temperature traps) at the poles, which can accumulate and preserve water ice. Inspired by the detection of ice layers in the permanent shadow zones at the poles of Mercury, various countries conducted explorations through multiple probes such as "Clémentine", "Lunar Prospector", "Lunar Reconnaissance Orbiter", and "Chandrayaan-1". Finally, the US "Lunar Crater Observation and Sensing Satellite" confirmed the existence of water ice in the permanent shadow zones of lunar craters at the poles through its impact probe detection.