A walk from the Sun to Neptune

Almost every picture of the solar system lies. To fit on a page, the planets are squeezed together and blown up in size. Walk it at true scale and you discover the real star of the show: empty space.

The solar system is mostly empty space, and that emptiness is the whole story.

Look

Most pictures of the solar system squeeze the planets together like beads on a string, and draw them far too big. They have to: at true scale, a page would be almost completely empty.

Guess first: if the Sun were a beach ball, how far away would Earth be? A step? A room? A street?

A street. With the Sun as a 1-metre ball, Earth is a 9 mm pea about 107 metres away: roughly the length of a football pitch. Keep that picture in mind as you travel.

The Scale Walk above is drawn at true scale: sizes and distances in the same proportion. Every pixel you scroll carries you 3,000 km. Scroll inside the frame, press Next world, or tap a planet on the journey map at the top.

• The journey map is to scale too. The white marker is you. Notice how the Sun and the four inner planets crowd together at the far left.
• The odometer counts kilometres and the time sunlight has needed to get where you are.
• When you stop near a world, the camera locks on and leans in (the zoom is shown next to the scale bar), and a card tells you where you are.
• Earth, a globe 12,742 km across, is almost 50,000 scrolled pixels from the Sun. Neptune is about 1.5 million pixels away.

Notice how much of the trip is just black, with only a few lines of narration drifting past. That is the real solar system: tiny worlds separated by enormous emptiness.

Understand

A scale model divides every length by the same number. Here the number is 3,000: 3,000 km of real space becomes 1 pixel.

World	Real diameter	Diameter at 1 px = 3,000 km	Distance from Sun	At this scale
Sun	1,391,400 km	464 px	0	0
Earth	12,742 km	4 px	149.6 million km	49,866 px
Jupiter	139,822 km	47 px	778.3 million km	259,437 px
Neptune	49,244 km	16 px	4,498 million km	1,499,000 px

A handy comparison uses the Sun as a 1-metre ball. Divide everything by the Sun’s diameter (1.39 million km):

• Earth is a 9 mm pea, 107 m away.
• Jupiter is a 10 cm grapefruit, 560 m away.
• Neptune is a 3.5 cm marble, 3.2 km away.
• The nearest star, Proxima Centauri, would be another ball about 29,000 km away: more than two thirds of the way around the real Earth.

Try the autopilot at 1×, the real speed of light. You move 100 pixels per second, which feels slow on screen. Real sunlight really does need 8 minutes to reach Earth and more than 4 hours to reach Neptune. The faster settings compress time, not distance: the autopilot still brakes and pauses at every world.

Guess first: scrolling with a mouse wheel, are you moving faster or slower than light?

Much faster. A brisk scroll carries you millions of kilometres per second, often ten or more times the speed of light; the speed readout under the odometer shows it. Even so, the outer planets take a long time to reach. That is how big the distances are.

Master

Two separate compressions distort normal diagrams: the size scale and the distance scale. The ratio of the Sun-Neptune distance (4.5 × 10⁹ km) to Earth’s diameter (1.27 × 10⁴ km) is about 350,000. A screen 1,000 pixels tall can resolve a range of about 1,000, so no single static image can show both the planets and their spacing. Interactive zoom, logarithmic axes or a scroll-length model like this one are the only honest options.

This is also why the orrery on this site offers two modes. Readable scale compresses distance with a square root (r_screen ∝ √r) and draws planets at fixed legible sizes. True scale is linear in both size and distance, so the planets shrink to sub-pixel dots.

The emptiness has consequences for spaceflight. Travelling between planets is not like driving between cities: the planets move, the distances are huge, and the energy cost depends far more on changes of speed than on distance. That idea, delta-v, is at the heart of the Navigator path.

A last scale fact: the asteroid belt, often drawn as a crowded field of rocks, is so sparse that spacecraft cross it without any special manoeuvres. The Kuiper belt beyond Neptune is emptier still.