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Space / Class 4–8 / 12 min / Medium

Solar System Orbit Explorer

Discover that planets farther from the Sun move more slowly and take longer to complete an orbit (Kepler’s third law, explored visually).

Before you try

What if you lived on Neptune? How many Earth years would pass before your first birthday?

Try it out

Interactive activity

Loading simulator…

Loading controls…

What happened?

Move a control to see what changes and why.

Distances are squashed to fit the screen and the orbits are drawn as circles. The orbit times are real, but the real paths are slightly oval.

Try these ideas

  • Select Mercury and count how many laps it makes while Earth makes one.
  • Set the speed high and watch which planet barely moves.
  • Compare the orbit time of Mars and Jupiter.

Why it works

All eight planets travel around the Sun in nearly circular paths called orbits. Mercury, closest to the Sun, finishes a lap in 88 days; Neptune, the farthest, needs about 165 Earth years.

Distances in the solar system are enormous, so this simulator uses a squashed distance scale to fit everything on one screen, while keeping the real orbital periods. Pick a planet to follow it and read its real numbers.

Check your understanding

Question 1 of 3

Which planet takes the longest to orbit the Sun?

As a planet is farther from the Sun, its orbit time…

About how many Earth days is one Mercury year?

Explain it in your own words

What changed? Why did it happen? Where might you notice this in everyday life?

What will you discover next?

Try Day, Night and Seasons: Discover Earth’s Tilt next.

Continue learning

For parents & teachers

  • Work out your age in Mars years (divide Earth age by 1.88).
  • Ask: why might Earth be the “just right” distance for life?
  • Discuss why a model needs a squashed scale. How big is the real solar system?

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