Astronomy was first studied by ancient Egyptians in their exploration of the Moon, stars and other objects in space. The ancient Egyptians were the first explorers to find out what causes day and night. They studied how the Sun and the Moon travelled across the sky by observing their different movements. The early astronomers discovered that the Earth contains an imaginary line, called an axis, that passes through the centre of the Earth. This axis also passed between the North and South Poles.
Occurrence of Day and Night
The Earth rotates on its axis. This rotation causes day and night. When the Earth faces the Sun, the part of the Earth experiences daytime. On the other hand, when the Earth faces away from the Sun, the part of the Earth experiences night-time. Thus, day being on one side of the Earth and night is on the other side of the Earth. Each rotation on the Earth’s axis takes about 24 hours to complete. This 24 hour cycle includes both day and night, and makes one day.