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Explorer · Modul 2

A walk from the Sun to Neptune

Almost every picture of the solar system is wrong about scale. Walk it at true scale and feel how empty space really is.

10 min

NASA

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Everything here is at true scale: sizes and distances in the same proportion. Each pixel you scroll carries you 3.000 km.

Sabuk asteroid utama
Sabuk Kuiper
1 menit cahaya
5 menit cahaya
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1 jam cahaya
70 menit cahaya
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110 menit cahaya
2 jam cahaya
130 menit cahaya
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3 jam cahaya
190 menit cahaya
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4 jam cahaya
250 menit cahaya
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5 jam cahaya
310 menit cahaya
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340 menit cahaya
Merkurius 4.879 km · 0,387 au · 3 mnt 13 dtk
Venus 12.104 km · 0,723 au · 6 mnt 1 dtk
Bumi 12.742 km · 1 au · 8 mnt 19 dtk
Mars 6.779 km · 1,52 au · 12 mnt 40 dtk
Ceres 939 km · 2,77 au · 23 mnt 0 dtk
Jupiter 139.822 km · 5,2 au · 43 mnt 16 dtk
Saturnus 116.464 km · 9,54 au · 1 j 19 mnt
Uranus 50.724 km · 19,2 au · 2 j 40 mnt
Neptunus 49.244 km · 30,1 au · 4 j 10 mnt
Pluto 2.377 km · 39,6 au · 5 j 29 mnt

Keep scrolling. Every picture you have seen of the solar system squeezed this emptiness out.

Mercury is ahead, where sunlight is almost seven times stronger than on Earth.

Still nothing. You have crossed 16,8 juta km since Merkurius.

The sunlight passing you now left the Sun 5 mnt 5 dtk ago.

Earth is ahead. Watch how small home turns out to be.

Mars is still 58,8 juta km ahead.

A radio message from Earth takes between 3 and 22 minutes to reach Mars, depending on where the two planets are.

You could line up 4.611 Earths side by side in the space you have crossed since Bumi.

You are 14% of the way from Mars to Ceres.

Still nothing. You have crossed 53,1 juta km since Mars.

The sunlight passing you now left the Sun 17 mnt 6 dtk ago.

Ceres is still 79,6 juta km ahead.

You are inside the asteroid belt. Did you hit anything? On average the asteroids are about a million kilometres apart.

You could line up 12.497 Earths side by side in the space you have crossed since Mars.

You are 17% of the way from Ceres to Jupiter.

Still nothing. You have crossed 122 juta km since Ceres.

The sunlight passing you now left the Sun 33 mnt 8 dtk ago.

Jupiter is still 122 juta km ahead.

You could line up 23.846 Earths side by side in the space you have crossed since Ceres.

You are 10% of the way from Jupiter to Saturnus.

Still nothing. You have crossed 130 juta km since Jupiter.

The sunlight passing you now left the Sun 54 mnt 5 dtk ago.

Saturnus is still 389 juta km ahead.

Voyager 1 took about 20 months to fly from Jupiter to Saturn.

You could line up 30.529 Earths side by side in the space you have crossed since Jupiter.

You are 70% of the way from Jupiter to Saturnus.

Still nothing. You have crossed 519 juta km since Jupiter.

The sunlight passing you now left the Sun 1 j 16 mnt ago.

Uranus is still 1,31 miliar km ahead.

You could line up 20.605 Earths side by side in the space you have crossed since Saturnus.

You are 27% of the way from Saturnus to Uranus.

Still nothing. You have crossed 525 juta km since Saturnus.

Uranus orbits twice as far from the Sun as Saturn. The farther out you go, the emptier it gets.

The sunlight passing you now left the Sun 2 j 3 mnt ago.

Uranus is still 525 juta km ahead.

You could line up 82.418 Earths side by side in the space you have crossed since Saturnus.

You are 82% of the way from Saturnus to Uranus.

Still nothing. You have crossed 1,31 miliar km since Saturnus.

The sunlight passing you now left the Sun 2 j 48 mnt ago.

Neptunus is still 1,33 miliar km ahead.

You could line up 34.840 Earths side by side in the space you have crossed since Uranus.

You are 36% of the way from Uranus to Neptunus.

Still nothing. You have crossed 740 juta km since Uranus.

Voyager 2 needed about three and a half years to cross this gap, from Uranus in 1986 to Neptune in 1989.

The sunlight passing you now left the Sun 3 j 37 mnt ago.

Neptunus is still 444 juta km ahead.

You could line up 104.519 Earths side by side in the space you have crossed since Uranus.

You are 91% of the way from Uranus to Neptunus.

Still nothing. You have crossed 129 juta km since Neptunus.

The sunlight passing you now left the Sun 4 j 24 mnt ago.

The Kuiper belt: a ring of icy worlds so spread out that after Pluto, New Horizons flew close to just one of them.

Pluto is still 906 juta km ahead.

You could line up 50.798 Earths side by side in the space you have crossed since Neptunus.

You are 55% of the way from Neptunus to Pluto.

Still nothing. You have crossed 906 juta km since Neptunus.

New Horizons, one of the fastest spacecraft ever launched, took nine and a half years to reach Pluto. Sunlight gets to Pluto's average distance in about five and a half hours.

The sunlight passing you now left the Sun 5 j 15 mnt ago.

Pluto is still 129 juta km ahead.

0 km 0 au · Cahaya telah bepergian untuk 0 s
Autopilot speed

Tabel data (alternatif teks)
DuniaDiameterJarak dari MatahariWaktu perjalanan cahaya dari Mataharipx
Merkurius4.879 km0,387 au3 mnt 13 dtk19.303
Venus12.104 km0,723 au6 mnt 1 dtk36.070
Bumi12.742 km1 au8 mnt 19 dtk49.866
Mars6.779 km1,52 au12 mnt 40 dtk75.981
Ceres939 km2,77 au23 mnt 0 dtk137.907
Jupiter139.822 km5,2 au43 mnt 16 dtk259.447
Saturnus116.464 km9,54 au1 j 19 mnt475.555
Uranus50.724 km19,2 au2 j 40 mnt956.886
Neptunus49.244 km30,1 au4 j 10 mnt1.499.465
Pluto2.377 km39,6 au5 j 29 mnt1.974.125

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.

A thin crescent of Neptune against black space.
Neptune, the farthest planet, seen by Voyager 2 as it left for interstellar space. Credit: NASA/JPL

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.

WorldReal diameterDiameter at 1 px = 3,000 kmDistance from SunAt this scale
Sun1,391,400 km464 px00
Earth12,742 km4 px149.6 million km49,866 px
Jupiter139,822 km47 px778.3 million km259,437 px
Neptune49,244 km16 px4,498 million km1,499,000 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.

Cobalah.

Set the autopilot speed to 1× and press 'Travel at the speed of light'. Watch the light-time clock as you reach Earth: about 8 minutes 20 seconds. Before you look at the table, guess how long the same trip takes to Neptune, then check.

Kuis Cepat

3 quick questions. Pick an answer to see if you are right.

  1. If the Sun were a ball 1 metre wide, about how big would Earth be?

    1. A A football
    2. B A grapefruit
    3. C About 9 millimetres, like a pea
    4. D About 1 millimetre
    Show the answer

    C. About 9 millimetres, like a pea The Sun is about 109 times wider than Earth, so 1 m ÷ 109 ≈ 9 mm.

  2. At that same scale, how far away would Earth be from the 1-metre Sun?

    1. A About 1 metre
    2. B About 10 metres
    3. C About 107 metres
    4. D About 1 kilometre
    Show the answer

    C. About 107 metres 1 au is about 107.5 Sun diameters, so Earth would be a pea about the length of a football pitch away.

  3. Why do most drawings of the solar system show the planets close together?

    1. A Because they really are close
    2. B Because at true scale the planets would be too small to see on the page
    3. C Because the drawings show the planets at their closest approach
    4. D Because of light pollution
    Show the answer

    B. Because at true scale the planets would be too small to see on the page

Finish line

  • Played with the interactive
  • Read the lesson
  • Did the challenge
  • Took the quiz

Mark the lesson complete to save it to your progress on this device.

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