Audio Guide：

The plane of Earth’s orbit around the Sun is called the ecliptic. Seasonal changes are a result of the 23.5-degree angle between Earth’s rotational axis and the ecliptic plane. This tilt angle allows the Northern and Southern Hemisphere to receive different amount of solar energy during different times of the year. The division of day and night derives from the fact that it takes 24 hours for the Earth to complete a full rotation. While it is daytime for the side of the Earth facing the Sun, it is night time for the other side in the dark.