What is an astronomical calendar?

Astronomy is the foundation of the calendar. In the pre-Qin period, people thought that the sky was round, supported by four big pillars, east, west, north and south, which covered the earth like a hemispherical cover. The ancient calendar of China adopted the combination of Yin and Yang, that is, the cycle of the sun was taken as the year, the cycle of the moon as the month, and the leap month was used to coordinate the relationship between the year and the month.

According to the position change of the sun in a year and the evolution order of the ground climate caused by it, the ancients divided the year into 24 segments and 12 months to reflect the four seasons, temperature and phenology. These 24 solar terms, established by the movement of the sun, reflect the changes of the four seasons and are closely related to the production of agriculture and animal husbandry, so they are also called lunar calendar.

The complete name of the twenty-four solar terms first appeared in Huai Nan Zi Tian Wenxun in the early Han Dynasty, which is consistent with the current name. Solar terms originated in ancient China, reflecting the changes of the four seasons when the earth revolves around the sun, and reflecting the farming season, which is well-known in rural areas.

With the spread of the ancient calendar in China, solar terms spread to the places where overseas Chinese went. Solar terms are determined according to the apparent position of the sun in the starry sky. Solar terms are also called twenty-four solar terms, which are the floorboard of twelve solar terms and twelve solar terms alternately arranged.

Extended data

Mayan astronomical calendar:

The Mayans have more profound astronomical knowledge than modern people, and they are very accurate about the movements of stars such as the moon, the earth, the sun, Venus and the corresponding calendars. The Mayans had 22 calendars, covering the cycles of many planets in the solar system and beyond.

Maya Observatory is full of characteristics, and its function or appearance is very similar to that of modern observatories. Take Kairuoka Observatory as an example: it is built on a huge and exquisite platform, and the small steps lead to the big platform; A cylindrical ground floor building with a hemispherical cover is where the astronomical telescope extends.

The four doors on the ground floor face in four directions. Looking east, it is the sunrise direction of the vernal equinox and the autumnal equinox. Looking northeast, it is the sunrise direction from summer solstice. Looking to the southeast, it is the sunrise direction from winter solstice to Sunday.

The Mayans had several observatories, which archaeologists thought was an astronomical observation network. The most prestigious Chenchiyi Tea Observatory is the only circular building in Ma Zhi culture. A spiral staircase leads to a three-story platform with a pair of skylights at the top to observe the constellation.

From the diagonal line formed by the wall of the upper north window (3 meters thick), you can see the semi-circle of sunset at the vernal equinox and autumn equinox; The diagonal line of the south window just points to the south pole and the north pole of the earth. The observation windows of the Observatory are all aimed at Uranus and Neptune, which are invisible to the naked eye. Uranus was discovered by Herschel in 178l.

Neptune was discovered by Berlin Observatory at 1846. How did the Mayans know their existence and master their operation thousands of years ago?

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