Phases & Seasons

Geometry in the sky

An interactive lesson with 8 steps, about 7 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Moon phases come from seeing different amounts of its sunlit half.
• Seasons come from Earth’s 23.4° axial tilt, not from its distance to the Sun.
• Eclipses are rare because the Moon’s orbit is tilted about 5°.

Steps

1. Why phases?
2. Orbit the Moon
3. Two kinds of month
4. Full moon timing
5. Seasons
6. Hours of daylight
7. The noon Sun
8. Eclipses