The darkness that occurs at night on Earth is primarily due to the rotation of our planet. Earth spins on its axis, which is an imaginary line passing through its North and South Poles. This rotational motion causes day and night cycles.
As Earth rotates, different parts of the planet are either facing towards or away from the Sun, leading to the alternation between day and night. When a particular region is facing the Sun, it experiences daylight, while the opposite side is in shadow and experiences darkness.
During daytime, the Sun's rays directly illuminate the portion of Earth facing it, providing light and warmth. As the Earth continues to rotate, that illuminated region moves away from the Sun, and the areas previously in darkness come into daylight.
At night, when a specific location on Earth is facing away from the Sun, the sunlight is blocked by the Earth itself, leading to darkness. The absence of direct sunlight causes the sky to appear dark, although it is not completely devoid of light. Various other celestial objects, such as stars, planets, the Moon, and artificial lights, contribute to the overall illumination of the night sky.
The duration of daylight and darkness during a day varies depending on factors like the latitude and the time of year due to the tilt of Earth's axis and its elliptical orbit around the Sun. These factors influence the length of day and night, leading to variations in the amount of daylight experienced at different locations and times of the year.