All the planets share our Sun, but their orbital paths and speeds differ. Planets farther from the Sun generally take longer to complete an orbit. The activity uses published orbital periods to advance two clocks together. The circles are spaced for clarity rather than to show actual distances.
Space · Discover & try
Why do different planets have different years?
Reading level 2 of 5 · DevelopingChange
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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