The origin of the twenty-four solar terms

China's astrology culture has a long history and is profound. The ancients began to explore the mysteries of the universe very early, and thus deduced a complete and profound star-watching culture. Twenty-four solar terms were originally formulated according to the bucket handle rotation direction of the Big Dipper, which rotates circularly and is closely related to the seasonal changes. The Big Dipper consists of seven stars, namely Shu Tian, Tian Xuan, Tianji, Tianquan, Yuheng, Kaiyang and Yaoguang. Named for its twists and turns. The Big Dipper is an important astrological sign in the northern hemisphere (China is located in the northern hemisphere). The natural rhythm of the corresponding area in the northern hemisphere changes gradually when the Big Dipper rotates repeatedly, so it becomes the basis for ancient people to judge the seasonal changes. "Twenty-four solar terms" is a special festival to express the natural rhythm changes in the dry calendar and establish "December" (monthly order), which is a solar month based on "Twenty-four solar terms". One-year-old (taking photos) is divided into twelve days (made in December, made in December), and the monthly order is calculated by the Big Dipper. The day referred to by bucket handle is called "sword fighting" (also called Jian Yue). In traditional culture, the branch is linked with the time position of gossip, and the yin position is the root position of gossip the day after tomorrow. It is the position at the end of the year and the beginning of the year, representing the end and the beginning, such as Yi Shuo Gua Zhuan: "The root is also the divination of the Northeast, and everything begins." That is to say, bucket handle rotates clockwise from due east to due north (yin position, gossip position the day after tomorrow), indicating a "year old" (from beginning of spring to the next beginning of spring is one year old). Silver moon said that "spring is positive", and the beginning of spring is the beginning of a year. Beginning of spring is the beginning of all things and the meaning of all self-renewal. Bucket handle, the Big Dipper, points to the establishment of the 24 solar terms, starting from beginning of spring and ending in severe cold.

During the period of Emperor Wu of the Western Han Dynasty, "Twenty-four solar terms" were included in taichu calendar as a supplement to guide the agricultural calendar. In the Yellow River Basin, the longest day and the shortest day (the shortest day) of the sun shadow are measured by the expensive sun shadow method, and the winter solstice is taken as the starting point of the "24 solar terms". The winter solstice and the next winter solstice are divided into 24 equal parts, the time between each solar term is equal, and the interval between each solar term is 15 days. The solar terms divided by the "Land Returning to the Sun Shadow Law" list the winter solstice as the first of the "twenty-four solar terms", starting from the winter solstice and ending with heavy snow. The current "twenty-four solar terms" come from a method established more than 300 years ago (1645) to determine solar terms according to the position of the sun on the ecliptic, that is, on a 360-degree circle "ecliptic" (the sun's apparent path on the celestial sphere for one year), it is divided into 24 equal parts, and each 15 is 65438. That is to say, the sun starts at 0 degrees of the yellow meridian (when the sun shines vertically on the equator), every time it advances to 15 degrees, it is a solar term, and once it runs back to the vernal equinox, it is a tropic year. The circumference of the ecliptic is 360 degrees. Every time the sun runs 15 degrees on the ecliptic, it is a solar term, and each solar term has the same degree and different time. According to the "degree of longitude of the sun", the solar terms begin in the beginning of spring and end in the great cold.