The Earth is tilted on its orbit. This causes an unequal amount of sunshine to fall in different parts of the planet during the course of a year, and this is responsible for the seasons. You can use this animation to illustrate the variations in the length of daylight, and the seasons, in the different hemispheres.
The three cities represented (Stockholm, Brazzaville and Cape town) are located on the same meridian.
The animation is not drawn to scale.
Click on 'comments' to display the variation of the length of the day for three cities located on the same meridian line.