A journey from the Sun through the eight planets using proportional mean orbital distances. Choose any stop in the list or use Previous and Travel. Each stop has a written distance, light-time, diameter, and basketball-Sun analogy.
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How far apart are the planets? A solar system scale model
Pictures of the solar system squeeze the planets close together. Really, they are tiny specks spread across enormous empty space. Shrink the Sun to a 24 cm basketball , shrink everything else by the same amount, and here is what you get:
The solar system with the Sun shrunk to a 24 cm basketball (average distances from the Sun)
Planet Size Distance from the Sun
Mercury 0.8 mm, a grain of salt 10 m Venus 2.1 mm, a peppercorn 19 m Earth 2.2 mm, a peppercorn 26 m Mars 1.2 mm, a pinhead 39 m Jupiter 24 mm, a walnut 134 m Saturn 20 mm, a large marble 246 m Uranus 8.7 mm, a pea 495 m Neptune 8.5 mm, a pea 776 m
So on a school field, Earth is a peppercorn about 26 m from the ball, and Neptune is a pea almost 800 m away. Everything in between is almost completely empty.
How far away is the nearest star on this scale?
The nearest star to the Sun, Proxima Centauri, would be about 7,000 km away. If the basketball Sun sat in New York, the nearest star would be somewhere near Rome.
How long does sunlight take to reach each planet?
Light is the fastest thing there is, about 300,000 km every second. Even so, sunlight takes about 8 minutes to reach Earth, about 43 minutes to reach Jupiter, and more than 4 hours to reach Neptune. When you see the Sun, you are seeing light that left it about 8 minutes ago.
Why do books show the planets so close together?
Because a true-scale picture would not fit. If Earth were drawn as a dot you could see, Neptune would be hundreds of metres off the edge of the page. Books and most 3D models squeeze the distances, which is fine, as long as we remember that they do.
How to use the Scale Walk
Press Travel to move outward from the Sun one planet at a time, or pick a stop from the list. Each stop shows the average distance from the Sun, how long sunlight takes to get there, the planet’s size, and its basketball-scale comparison. Planet markers on screen are enlarged so you can see them, and the planets are lined up in a row rather than where they are tonight.
For teachers
Ages 8–14 (grades 3–8)
Time 20 minutes, or an hour with the outdoor walk
Standards NGSS MS-ESS1-3, 5-ESS1-1
Learning goals
Use one scale to compare the sizes of planets and the distances between them.
Recognise that the solar system is mostly empty space.
Use light travel time as another way to describe distance.
Try this in class
Before opening the page, ask students to draw the Sun and planets “to scale” on one sheet of paper. Keep the drawings.
Travel through the Scale Walk stop by stop and record each scaled distance.
Go outside with a ball for the Sun and seeds or beads for the planets. Pace out Mercury (10 m) to Mars (39 m). A large field can reach Jupiter at 134 m.
Back inside, compare the walk with the drawings from step 1. What surprised students most?
Discussion questions
Jupiter is the biggest planet, yet on this scale it is only 2.4 cm across. What does that tell you about space?
Why do spacecraft take years to reach the outer planets?
The Sun is a star. Why does it look so much brighter than the stars we see at night?
Why do textbook diagrams squeeze the planets together?
Sources
JPL Planet sizes
JPL Planet orbits
NASA scale model activity
Reviewed Sep 27, 2026