1. The movement of the Earth as it rotates on its axis causes different parts of the Earth to be turned toward the Sun, which causes day, and away from the Sun, which causes night.

2. The tilt of the Earth alters how directly the light shines on the Earth during different points in its revolution. This causes some areas of the Earth to experience seasonal changes. For example, summer in the Northern Hemisphere occurs because light received from the Sun is more direct (and therefore more intense) on the northern hemisphere at that point in the Earth’s revolution than at any other. At the same time of the year, due to the tilt of the Earth’s axis, the light received at the Southern Hemisphere is more indirect (and therefore less intense) than at any other time of year.