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Seasons and Ecliptic Simulator
Earth's tilt & seasons
Earth's axis is tilted 23.5°. When the northern hemisphere tilts toward the Sun, it's summer there (and winter in the south).
N. hemisphere season: Summer
Sun declination: 23.4°
HK noon Sun altitude: 88.9°
Orbit view (top down)
Before you start
Seasons are caused by Earth's axial tilt, not by changing distance to the Sun. This simulator shows the geometry.
Key idea
When your hemisphere tilts toward the Sun, sunlight is more direct and days are longer — summer. Tilting away gives winter.
What you see
- Top-down Earth orbit with tilted axis
- Ecliptic vs celestial equator angle diagram
- Season and declination readouts for HK
Try this
- Set day to June 21 — northern summer, HK Sun nearly overhead at noon
- Set day to December 21 — northern winter
- Watch how declination drives the season label
Why it matters in Hong Kong
Hong Kong experiences distinct wet/dry seasons influenced by monsoons, layered on top of this solar geometry.
Common mistakes
- Believing summer is when Earth is closest to the Sun
- Thinking both hemispheres have summer at the same time
Glossary
- Obliquity
- Earth's axial tilt, currently 23.45°.