Why Does the Sunset Move? A Lesson on Earth's Tilt and the Seasons
Students explain why the Sun sets in a different place on the horizon through the year, using a model of Earth's tilted axis.
Aligned to: NGSS MS-ESS1-1: develop and use a model of the Earth-Sun system to describe seasons.
Materials
- A lamp without a shade (the Sun)
- A globe or ball with a pencil through it, tilted about 23½ degrees
- A compass or phone compass
- The horizon sketch sheet below
Lesson steps
| 5 min | Hook. Ask: does the Sun always set in the west? Collect answers. Most students say yes, exactly west. |
| 10 min | Notice the pattern. Share the facts: near the June solstice the Sun sets well north of west in the Northern Hemisphere; near the December solstice it sets well south of west; at the equinoxes it sets very close to due west. |
| 15 min | Model it. Darken the room. Walk the tilted globe around the lamp, keeping the tilt pointing the same direction. Students observe which hemisphere leans toward the lamp in each position. |
| 12 min | Horizon sketch. Students sketch their real western horizon (from a window or memory) and mark where they predict the Sun sets in June, March/September and December. |
| 8 min | Exit ticket. Students answer on their own. |
Exit ticket
Name: ____________________
- Where does the Sun set near the June solstice (Northern Hemisphere)?
- What causes the sunset position to move during the year?
- Predict: where will the Sun set on the day of your next birthday?
Answer key and teacher notes
- North of due west.
- Earth's tilted axis, which keeps pointing the same direction as Earth orbits the Sun.
- Answers vary; check that the reasoning uses the month and the solstice pattern.
Keep practising
Asterfold: Sunset Planner
To check predictions for your own school's horizon, Asterfold: Sunset Planner draws the Sun's real path for any place and date and shows the year's range of sunset directions. It calculates on the iPhone, so it works offline in class.
Get it free on the App StoreTeacher FAQ
Is this lesson plan free to use?
Yes. Print and copy it for your class or group. No sign-up.
How long does it take?
About 50 minutes, with timings for each part so you can trim it to fit.
What do I need?
Only everyday classroom materials, listed under Materials. No app or device is required to teach it.