Which solar term was first determined in ancient China?

The vernal equinox ranks fourth among the 24 solar terms and is one of the earliest solar terms in ancient China. As early as the Spring and Autumn Period and the Warring States Period, China began to measure the length of the midday sun shadow with earth gauge. Through this ancient method, the ancients in China determined four solar terms: winter solstice, summer solstice, vernal equinox and autumn equinox. During the Qin and Han Dynasties, China had a complete concept of twenty-four solar terms.

Every year on March 2 1 day, the sun reaches the hottest meridian zero, which is the vernal equinox. The vernal equinox means the average distribution of time between day and night, every 12 hours. The vernal equinox is in the first three months of the year. During the spring equinox, the average temperature in China is stable at around 10 degrees Celsius. In the meteorological sense, agricultural production enters the peak season in spring.

In the pre-Qin period, China had four seasons. "History? Yao Dian recorded four solar terms:? Riyong? A short time? Japanese and China? At night, it represents the vernal equinox, autumnal equinox, summer solstice and winter solstice respectively. In ancient China, the vernal equinox was divided into three stages: waiting for the arrival of mysterious birds; Second, wait for Lei Nai to make a sound; Wait for the third power on? Xuanbird? This refers to swallows, right? Equinox? . ? Autumn equinox? It is a migratory bird. The vernal equinox is one of the earliest solar terms in China, which is both a solar term and a festival. Since the Zhou dynasty, there has been a ceremony to worship the sun at the vernal equinox. Later, various dynasties gradually formed the ritual system of vernal equinox and autumnal equinox.

On the vernal equinox, there are many folk customs, such as outing, flying kites, sending spring cattle and eating spring vegetables. There is another interesting custom? Vertical eggs. Why do eggs stand upright at the vernal equinox and autumn equinox? Scientists analyzed the reasons and found that the length of day and night in the northern and southern hemispheres is the same at the vernal equinox and the autumnal equinox, and the earth axis and the orbital plane around the sun are in a relatively balanced state, which is conducive to egg-shaped erection. From the perspective of an egg, you can choose a new egg that has been laid for four or five days. This time, the yolk of the egg sinks and the center of gravity of the egg drops, which makes the success rate of the egg standing up higher.