The Earth's Elliptical Orbit around the Sun

Students create models of orbital precession using different colors of chalk.

Due to Earth being one 7 planets in the solar system, the forces from these planets (as well as the Sun and our moon) causes the Earth's orbit to vary over time.  While these changes are slight... they greatly impact our climate.  There are three kinds of changes:  eccnetricity, obliquity, and precession... these insolation cycles are called Milankovitch Cycles.