Vernal equinox phenology

In ancient China, the vernal equinox was divided into three stages: "One stage is the arrival of mysterious birds; Second, wait for Lei Nai to make a sound; Third, wait for electricity. " In other words, after the vernal equinox, swallows will fly from the south, and when it rains, the sky will thunder and lightning.

The vernal equinox is one of the 24 solar terms. The sun moves from south to north on the celestial sphere to the intersection of the celestial equator and the ecliptic. At this time, it is called the vernal equinox. On this day, day and night are equal in length. When the vernal equinox comes, there are various cultural customs to celebrate the arrival of spring. At this time, day and night are equally divided, each for 12 hours. Second, in ancient times, it was spring from beginning of spring to long summer, and the vernal equinox was divided equally among the three months of spring.

Every spring equinox, tens of millions of people all over the world are making "China folk custom vertical eggs". Eggs are easy to stand on the vernal equinox, because the vernal equinox in the northern and southern hemispheres is the same day, and the earth's axis is tilted by 66.5 degrees and is in relative balance with the orbital plane of the earth revolving around the sun, which is beneficial to stand eggs.