← All experimentsSPACE AND EARTH · AGES 8+

Planet Distance Explorer

Move planets and discover how far apart they can be.

SPACE & EARTH · DISTANCE LAB

How far apart are the planets?

Pick two planets, move one around the Sun and discover how their distance changes.

ORBIT VIEW · TOP DOWNILLUSTRATION ONLY

Move planet B around the Sun60°

Same directionOpposite sidesSame direction

The diagram’s orbit sizes and planet markers are not to scale. The calculation uses circular, coplanar orbits based on average Sun distances; it is not a live map.

STRAIGHT-LINE MODEL DISTANCE200.6 million km

Average distance from the Sun

Earth A

149.6 million km

Mars B

228 million km

Choose your learning level

Planet APlanet B

1. Predict: which arrangement is closer?

Why it happens: changing planet distances

Planets travel around the Sun at different speeds. As their positions change, the straight-line distance between them changes too. This model lets you control their relative angle; it is a simplified snapshot, not a forecast of where the planets actually are.

One astronomical unit (AU) is approximately the average Earth–Sun distance: 149.6 million km. Our calculations use rounded average Sun distances from NASA’s Planetary Fact Sheet.

Real-world connection & myth buster

Space missions must consider that planets move while a spacecraft travels. Actual trajectories are curved and travel times depend on many factors, not just the straight-line gap.

Myth: Planets stay lined up at fixed distances from one another. Actually: each planet travels around the Sun, so the distance between a pair changes.

Planet markers are enlarged to be visible. This activity compares distances separately from planet sizes.

My experiment notebook

Pin up to 10 setups on this device and restore them to investigate again.

My idea or observation

No setups pinned yet.

Quick knowledge check · 3 questions

1. What does 1 AU roughly measure?

2. Why does the distance between two planets change?

3. Are planet sizes shown to the same scale as orbital distances here?

Loading the fun.

THE BIG IDEA

What is happening?

Choose two planets, predict what happens when they move, and compare their distances.

Circular coplanar orbits use rounded average Sun distances. Illustrations and planet sizes are not to scale, and positions are not live.

Questions to explore

How far apart are the planets?

The distance between planets changes as they move around the Sun. This model calculates an approximate gap using circular orbits.

How far is Mars from Earth?

In this simplified circular model, Earth and Mars range from about 78.4 million to 377.6 million km apart; real distances differ.

What is an astronomical unit?

One AU is about 149.6 million kilometres, approximately the average Earth–Sun distance.

Are the orbit pictures and planet sizes to scale?

No. Markers and orbit pictures are illustrative; the distances are calculated separately.