The Sun's Declination

[Download/Play Movie (2 MB)]

We talk about how the seasons result from the tilt of the Earth's axis. Students often find this to be new and surprising, and so memorize that "the tilt" is responsible for all sorts of things. Later I will find that they use "the tilt" or "the tilt of the Earth" (without even any conception of what is tilted relative to what) as an answer to any qeustion regarding why things appear to be moving the way they do in the sky.

This movie tries to show why the tilt makes the Sun higher in the sky some times of the year than othe times of the year. It starts showing the Earth orbiting the Sun, with tilted poles sticking out of the earth. After a few orbits, it turns on an extended equatorial plane, so that you can see when the Sun is above or below that equatorial plane.

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.

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