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Motions of the Sun Simulator
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Default latitude is Hong Kong (22.3°N). Turn on Show the analemma in General settings for the figure-8 / solar-term pattern.
Before you start
The Sun has two main motions: daily (east to west from Earth's spin) and yearly (west to east along the ecliptic from Earth's orbit).
Key idea
Daily motion dominates what we see each hour. Yearly motion shifts the Sun's background constellation and changes the daily path through the seasons.
What you see
- Daily tab: horizon dome with Sun moving along today's path
- Yearly tab: Earth orbiting the Sun
- Optional analemma image with Chinese solar terms
Try this
- Daily tab: slide time from sunrise to sunset on the solstice
- Yearly tab: move day of year and watch Earth's orbital position
- Enable analemma overlay to see the full yearly pattern
Why it matters in Hong Kong
The Chinese solar terms (节气) in the analemma image divide the year based on the Sun's ecliptic longitude — still used in traditional calendars.
Common mistakes
- Thinking the Sun's yearly motion is east to west (it's the opposite of daily)
- Confusing solar and sidereal days
Glossary
- Analemma
- Figure-8 shape traced by the Sun at the same clock time over a year.
- Ecliptic
- Apparent yearly path of the Sun among the stars.