The length of a day by comparison with that of a night depends on the date and the place. This is the result of the sphericity of the Earth and its inclination in relation to the Sun.
The part of the Earth which lies in the shadow of the Sun corresponds to the night zone. This zone is a half sphere but, when transferred to the plane projection of a flat world map, this shadowed zone takes on a complex shape that changes in the course of a year.
This animation enables us to simulate these changes and to illustrate the following phenomena:
Click on the button to speed up the passage of time.
Click and drag the cursor to change the date.
Click and then pivot the terrestrial globe to change the viewing angle.