Does spring begin at the beginning of spring or at the vernal equinox?

Beginning of spring is the first of the 24 solar terms and an important festival. Astronomically speaking, it marks the beginning of spring. The understanding of beginning of spring is explained in the ancient book Qunfangpu: "Li, Jian also. Spring began and was established. "

The establishment of the traditional twenty-four solar terms in China requires rigorous knowledge of astronomy and mathematics. When the earth revolves around the sun at a certain inclination, it is in different positions in the orbit at different times, and different places on the earth receive different sunlight, which leads to seasonal changes and differences between cold and hot.

The traditional 24 solar terms in China have corresponding astronomical positions. At the vernal equinox and autumnal equinox, the sun shines directly at the equator, while at the summer solstice and winter solstice, the sun shines directly at the Tropic of Cancer and Tropic of Capricorn. Therefore, the four seasons are only produced because the earth revolves around the sun with a special tilt. Simply put, there is an included angle between the orbital plane (ecliptic plane) of the earth's revolution and the equatorial plane of the earth, which is called the ecliptic angle. At present, the equatorial angle of the earth is about 23 26'.

The angle between yellow and red is not constant. There has always been a slight change, but because the change is small, it can be ignored in a short time. It's really scary to think about it. Our four seasons, our apricot blossom and spring rain, Xia Shu under our shade, our geese walking, and our dogs barking on snowy nights are all based on the inclination of the earth around the sun. If the earth stands up straight and doesn't lean, then all this is gone.