What is the autumnal equinox solar terms

1, the autumnal equinox, is the sixteenth of the twenty-four solar terms, and the time is generally from September 22nd to 24th of the Gregorian calendar every year. On the day of the autumnal equinox, the sun reaches the longitude 180 (autumnal equinox), almost reaching the equator of the earth, and the length of day and night is equal all over the world (regardless of the refraction of the sun light by the atmosphere and the shadow in the morning). In ancient times, there was a folk activity of "Spring Festival to the Sun and the Moon". The autumnal equinox used to be the traditional "Festival to offer sacrifices to the moon", and the Mid-Autumn Festival evolved from offering sacrifices to the moon in autumn.

2. After the autumnal equinox, the direct point of the sun continues to move from the equator to the southern hemisphere, and the days in the northern hemisphere become shorter and the nights become longer, that is, the days in a day are shorter than the nights; The southern hemisphere is the opposite. Therefore, the autumnal equinox is also called the landing point. At the North Pole and South Pole, on the day of the autumn equinox, the sun is on the horizon all day. After that, as the direct point of the sun continued to move southward, a six-month polar night began near the North Pole, which gradually expanded and then narrowed. A six-month polar day began near the South Pole, which gradually expanded and then narrowed.