What are the 24 solar terms based on?

What is the basis for the ancients to formulate the twenty-four solar terms?

Specifically, the beginning is a law, which is summed up by residents in a certain area of China by observing the periodic climate change every year. It is also gradually established. A few years ago, it was discovered that there was a legend in Chu silk that two gods gave birth to four sons, and each son controlled two or two. There is nothing to say about other solar terms. It can be seen that the vernal equinox in spring and autumn and the sol point in winter and summer were established very early. After all, this solar term can almost be seen with the naked eye.

Moreover, China's rod measuring method and technology also have a certain historical origin. The noon shadow of the sun is the longest in winter and the shortest in summer. This is obvious. By the Qin and Han Dynasties, there had been 24 complete solar terms. This method usually measures the time between two winter solstices and divides them into 24 equal parts. This is the so-called "flat gas method". So this method is actually based on the length of the noon sun shadow or the noon sun height.

Of course, the Qing dynasty was already a western astronomy.

Another method to calculate solar terms is based on the ecliptic coordinates of the sun.

The twenty-four solar terms are based on the position change of the ancient ecliptic (that is, the earth's orbit around the sun). Each solar term corresponds to a position on the ecliptic where the sun reaches every 15. Formulate a climate law. The earth's orbit around the sun was called "ecliptic" by the ancients, also known as "solar path". The ecliptic is divided into 24 equal parts, separated by 15, forming 24 solar festivals. The 24 solar terms are actually 24 solar terms, 2 per month. The twenty-four solar terms take the period of the earth's revolution around the sun as the cycle, which fundamentally summarizes the different positions of the sun on the ecliptic at different times of the year, the exact cold and hot time, the laws of natural phenomena such as rainfall and snowfall, and records the moments of some phenological phenomena in nature.