Earth takes about 365.2 days to orbit the Sun; Mercury about 88 and Mars about 687. After 100 Earth days, Mercury has completed more than one orbit, while Mars has completed only part of one. Count complete turns as well as looking at the marker’s final position.
Space · Discover & try
Why do different planets have different years?
Reading level 3 of 5 · IndependentChange
Word help
Orbital period
The time required for one complete orbit.
Rotation
Turning around an axis, distinct from orbiting another body.
Earth day
The common time unit used in this comparison.
Watch · Try · Explain
See how it works
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Published periods with circular, constant-speed timing paths; drawn orbital radii are not a distance scale.
What to look for
- Use one elapsed-time clock for both planets.
- Count whole completed orbits.
- Distinguish orbit radius in the drawing from real distance.
Explain what you noticed
A hypothetical planet takes 500 Earth days to orbit its star. After 1,000 Earth days, how many years have passed on that planet?
Keep this idea: A year is one orbit around the Sun, not one daily rotation.
Follow the sources
Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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