Brief introduction and origin of vernal equinox

First of all, the origin of the vernal equinox

Every year, the vernal equinox begins on March 20th, and the sun reaches 0 degrees of the yellow meridian (vernal equinox). The length of day and night is average, just half of the 90th day of spring, so it is called "vernal equinox". On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. Then the direct sunlight position gradually moved northward, and the days were long and the nights were short.

Second, introduce the vernal equinox

The vernal equinox is one of the 24 solar terms and the fourth solar term in spring. The vernal equinox is of great significance in astronomy. On the day of the vernal equinox, the sun shines directly on the equator, and the northern and southern hemispheres are divided equally day and night. Since then, the direct position of the sun has continued to move from the equator to the northern hemisphere. In the northern hemisphere, the day begins to be longer than the night, while in the southern hemisphere, it is the opposite. Climatically, there are also obvious characteristics. After the vernal equinox, China has entered a beautiful spring except the Qinghai-Tibet Plateau, Northeast China, Northwest China and North China.