Earth’s Axial Tilt
The Earth spins each day on an axis which is tilted with respect to the Sun. The diagram shows the summer solstice in the Northern Hemisphere: there are 24 hours of sunlight north of the Arctic Circle, and the rest of the Northern Hemisphere will experience its longest day and shortest night.
Six months later, the Earth will have travelled to the other side of the Sun. There will now be 24 hours of darkness north of the Arctic Circle, and the rest of the Northern Hemisphere will experience its shortest day and longest night.
This tilt of the Earth’s Axis is the direct cause of our weather seasons.