Share one clock
Every planet experiences exactly the same elapsed time.
Planet Year Race
Advance one shared clock and compare all eight planets as they complete different numbers of orbits.
Grades 3–5 · Earth Science
Your goal
Select Earth and advance the shared clock until it completes about 1 orbit. Compare Earth's completed orbits at the same time.
Reduced motion is on. The controls still update the scene.
0.00 Earth years elapsed for every planet. Earth completed 0.00 orbits. Earth completed 0.00 orbits.
Earth years
All eight planets share the same elapsed time. Circular orbital periods follow Kepler's law, period squared equals average distance cubed in Earth years and AU, with a fixed Sun. Orbit circles and planet icons are equal display sizes to make phases readable. They do not represent distance or diameter scales. Initial alignment is invented.
Related resources
Related explainers
Study as flashcards
Related infographics
Learn with Planet Year Race
Planet Year Race gives elementary learners one clock for comparing the years of all eight planets. Select a planet to track, advance the elapsed Earth years, and read how many orbits each world has completed. Mercury moves through many circuits while distant planets have barely begun a single trip. Equal display circles keep positions readable, and the orbital periods come from the relationship between distance and gravity. Guided goals ask for complete orbits so students can compare a planet’s own year with the same span of time on Earth.
What to look for
Read the orbit count
A planet year ends when that planet completes one circuit of the Sun.
Compare outer planets
Advance several Earth years and see how slowly the outer planets complete an orbit.
For teachers and curious learners
Recognize that planets farther from the Sun take longer to complete an orbit. Ask students to predict what will happen, change one setting, and explain what they observe. Learn gives a starting point. Practice and Challenge offer new goals with the same scene.
Circular orbits around a fixed Sun use period squared equal to average distance cubed in Earth years and AU. Equal display circles and planet icons are independent of physical distance and diameter. Starting alignment is invented.