Points to Notice:

1. Earth’s axis of rotation is inclined 23.5°, and that makes the sun move into the northern sky in the spring and into the southern sky in the fall. The four seasons of the year are defined by the location of the sun along the ecliptic.
2. The seasons are caused by the changes in solar energy that Earth’s northern and southern hemispheres receive at different times of the year. Because of circulation patterns in Earth’s atmosphere, the northern and southern hemispheres are mostly isolated from each other and exchange little heat. When one hemisphere receives more solar energy than the other, it grows rapidly warmer.