2, the autumn equinox, "points" is "half". At the autumnal equinox, the world is as long as day and night. After the autumnal equinox, the days are getting shorter and shorter in the northern hemisphere, and the nights are getting longer and longer in the southern hemisphere. China's ancient book "The Story of the Spring and Autumn Period, Yin and Yang in and out" said: "The autumn equinox, Yin and Yang are also half-phase, so it is cold and hot day and night.
3. In ancient China, the autumnal equinox was divided into three periods: "First, waiting for the arrival of birds; Second, wait for Lei Nai to make a sound; Third, wait for the power to start. " In other words, after the autumnal equinox, swallows will fly from the south, and when it rains, the sky will thunder and lightning; There is another sentence: "When the thunder stops; Second, wait for scorpion blank households; Wait until the water is dry. " It means that it thunders because the yang is strong, and after the autumnal equinox, the yin starts to be strong, so it doesn't thunder anymore. "