• This video explains that the gradual change in the direction of Earth's axis causes perihelion (the point when the Earth is closest to the Sun) to occur at different times in the calendar year. 
• Students will learn that the winter solstice always occurs on the same date because our calendar is based on the direction of the Earth's tilt with regard to the Sun.
  

Positives

• This video takes a unique approach as it starts with a misconception then shows why it is incorrect.
• There is a season simulator available to view the Earth throughout the seasons.

Additional Prerequisites

• This video is one of a series of Khan Academy videos on Earth's rotation and tilt. Students should watch the video on precession and obliquity before watching this video.
  

Differentiation

• Earth science classes could work in groups to act out the concept of precession. If students need help getting started, teachers could assign parts (e.g., narrator, sun, earth, perihelion, aphelion). Kinesthetic learners will enjoy this activity. 
• Other resources on this topic include this video that explains how seasons work, this Khan Academy video on how Earth's tilt causes the seasons, and this lesson on how latitude affects the climate.
  

This resource addresses the listed standards. To fully meet standards, search for more related resources.