Day occurs and night occurs because of the rotation of the Earth on its axis. The tilt of the Earth results in different parts of the Earth receiving direct sunlight at different times, resulting in the progression of day into night and back again. As the Earth rotates, the side facing the Sun is illuminated and experiences day, while the opposite side is dark and experiences night. The specific time of day—dawn, morning, noon, evening, and night—depends on the position of the observer relative to the Sun's position in the sky.