http://www.georgefcram.com/education/lgl6.html#l15
Lesson 15 - The Changing Seasons

[graphic]

The Earth revolves around the Sun in what is called an orbit (circle). As
the Earth moves around the Sun, it is inclined, or tilted, 23½° from the
perpendicular. The Earth's revolution and inclination are what cause the
changing seasons.

The illustration above shows the Earth's orbit around the Sun. Note that
the Earth is not straight up and down. The Earth is inclined 23½°. The
arrows extending from the Sun to the Earth represent where the direct rays
of the Sun are striking the Earth on the first day of each season.