Is the vernal equinox divided equally between day and night?

On the vernal equinox, the world is almost equally divided day and night. At the vernal equinox, theoretically, the world is as long as day and night (see the dawn). After the vernal equinox, the days in the northern hemisphere are getting longer and shorter, and the nights in the southern hemisphere are getting shorter and shorter.

The rotation of the earth causes the whole surface to alternate day and night. In astronomy, the dividing line between the daytime hemisphere and the night hemisphere is called the termination line. The terminator line divides the day arc and the night arc of the latitude circle into two. The length of solar arc and night arc determines the change of day and night in a place.

Explanation of diurnal variation

The earth is not only divided into day and night hemispheres in space, but also because of the rotation and revolution of the earth, the day and night hemispheres alternate in time, so that every place is sometimes located in the day hemisphere, thus experiencing the day.

Sometimes it is located in the hemisphere at night, so it experiences night. It's called day and night alternation. The cycle of alternating day and night is called 1 day, which is called solar day, which is different from sidereal day. Sidereal day is a simple cycle of the earth's rotation, and the formation of the solar day is not only due to the earth's rotation, but also includes the earth's revolution, which is the intersection of the two.