A Month on the Ecliptic

[Play/Download Movie (13 MB)]

Students can be confused by the number of things that are moving at once. The Sun appears to be moving from west to east on the celestial sphere, but from east to west on the sky. Students can cnfuse the apparent nightly rotations that arise from (in this model) the rotation of the celestial sphere with motions across the face of the celestial sphere.

This animation shows the celestial sphere rotate thirty times, over the course of the month. It starts on September 21, and ends on October 21. The ecliptic is shown on the celestial sphere, and the Sun is shown in its position on the celestial sphere. It has moved 1/12 of the way around the ecliptic by the end of the month.

This animation is also useful for illustrating the "wobbling" of the ecliptic described in the ecliptic tutorial in Adams et al.'s Lecture Tutorials for Introductory Astronomy.

As with many of my movies, there is no narration or sound. It's designed to be used by a lecturer, who will pause it at opportune places to discuss it or ask questions of students.

This work is licensed under a Creative Commons License.

Earth texture by Rick Kohrs.

[Back to Rob's Physics & Astronomy Movies]