Why is there day and night on Earth?
Earth is a sphere, and it is always spinning. As it spins, different parts of Earth are facing the sun. The side of Earth that is facing the sun is daytime. The side of Earth that is not facing the sun is nighttime.
Figure 1. Sun and moon
How do day and night happen?
Earth takes about 24 hours to spin once. That means that every 24 hours, the same part of Earth is facing the sun again. So, day and night happen over and over again.
What happens when the Earth’s axis is tilted?
Earth is tilted on its axis by about 23.5 degrees. That means that one part of Earth is always tilted towards the sun, and the other part is always tilted away from the sun. This tilt is what causes the seasons.
Figure 2. Earth with a tilted axis
Recommended books