The length of day and night in the northern and southern hemispheres at the vernal equinox, summer solstice, autumn equinox and winter solstice.

During the vernal equinox and the autumnal equinox, the days and nights in the northern hemisphere and the southern hemisphere are equally long, while during the summer solstice, the days in the northern hemisphere are long and the nights in the southern hemisphere are short. The winter solstice is short in the northern hemisphere and long in the southern hemisphere.

Day and night are produced by rotation, which is called "solar day", but the length of day and night is not equal to the rotation period, because the earth rotates once and revolves once at the same time, which changes the relative angle between the earth and the sun. Day and night are based on the range of the sun shining on the earth, so one day and night is 3 minutes and 56 seconds longer than the rotation period.

Extended data:

When the earth rotates, the ground facing the sun is "daytime" and the ground facing away from the sun is "night". This is the formation of day and night. After the vernal equinox, there are more and more sunshine in the northern hemisphere, so the nights in the northern hemisphere are short and the days are long, while the days in the southern hemisphere are the opposite; After the autumnal equinox, there is more and more sunshine in the southern hemisphere, so the days in the northern hemisphere are short and the nights are long, while the southern hemisphere is still the opposite.