When is the day equal to the night?
In the calendar of our planet there are 2 days, whenday is equal to night. These dates are called equinox days and are March 20-21 in spring and autumn - September 22-23. Accordingly, the time of the year, they are called the spring and autumn equinox.
This is due to the fact that our planetRotates, both around its invisible axis, and around the Sun. The line of the equator of the Earth has a slope of 23.5 degrees with respect to the plane of its orbit, therefore our Sunshine is half the calendar year in the northern hemisphere of the sky, and the second half in the southern hemisphere.
The day of the equinox is the calendar date, whenOur Svetilo passes from one hemisphere to another, relative to the celestial equator. From the moment when the day is equal to the night, in each hemisphere of the planet the astronomical season changes, that is, there comes the astronomical spring or the astronomical autumn, and the duration of the day increases or decreases with respect to the duration of the night. Accordingly, in the spring there is an increase in the day, and in the fall it decreases.