The reason for the cycle of day and night is the rotation of the Earth on its axis. The Earth is an oblate spheroid, which means it’s slightly flattened at the poles and bulging at the equator. It takes the Earth approximately 24 hours (one “day”) to complete one full rotation on its axis. As it rotates, different parts of the planet are facing the sun, which causes the cycle of day and night.

During the day, the part of the Earth that is facing the sun is in daylight. The sun’s light and heat reach this part of the planet, creating the conditions for daytime. At night, the part of the Earth that is facing away from the sun is in darkness. The sun’s light and heat do not reach this part of the planet, creating the conditions for nighttime. As the Earth continues to rotate, the cycle of day and night repeats.

It’s also to be noted that, Seasons are also caused by the tilt of the Earth’s axis. This tilt causes different parts of the planet to receive different amounts of sunlight over the course of the year, which leads to the change in the seasons.