Twenty-four tacos

In autumn, which is the sixteenth of the twenty-four festivals in the agricultural calendar, as in spring, the sun is almost straight towards the equator on the day of autumn, after which it moves southward and the northern hemisphere is short of day and night. Also, there were a few special phenomena on that day, when the direct rays of the Sun were impartial on the equator, and when people were on the equator line, they found that no object could find its own shadow sun; on that day, the Southern Arctic could see the sun at the same time; and at 45 degrees north, the height of the object was as long as the shadow。