← Back to course
Earth and Space 6-8 / Week 07 / Wednesday
3/6
Week 07 · How Far: Distances

Wednesday

Sky Deck Lab: Walk the solar system
// Walking the solar system one step at a time
⏱ about 20 min

Wednesday: Sky Deck Lab: Walk the Solar System

Rocket sets the Sun ball at the Sky Deck corner and lays a tape measure flat on the grass.

"One step for 150 million kilometers," he says. "Earth is one step. Here we go."

He takes one step and drops the Earth card. Half a step back, Mercury. Then Venus, then Mars. Four cards in a little cluster.

"What do you notice?" Raven asks. "You barely moved, and the inner planets are done."

Rocket walks on. Five steps, Jupiter. Nearly ten, Saturn. Nineteen, Uranus. Thirty, Neptune, at the far fence.

Nova hovers above the long empty gap between Saturn and Uranus. "Models make the quiet parts loud," she says. "Record the gaps."

Your mission

Today you walk a scale model of the planets' distances. One normal step stands for 150 million kilometers, about one astronomical unit.

The distances come from the NASA Planetary Fact Sheet. Each one was divided by 150 to get the number of steps.

You will place a labeled card at each planet, measure the gaps, and record what the model shows.

  • A ball or a bright object for the Sun
  • Eight pieces of paper labeled with the planet names, plus one for the asteroid belt
  • A tape measure or a long piece of string laid flat on the ground
  • A cleared hallway or a yard corner away from any road
  • Your Sky Log and a pencil
Safety first
Walk the model in a cleared hallway or a yard away from roads. Never step into a street to fit a planet.
String and tape stay flat on the floor, never around anyone. Pick them up when you finish.
Watch where you step. Move toys and shoes out of the path first.
WorldDistance from the Sun (million km)Steps (distance divided by 150)Steps to walk
Mercury57.90.4less than half a step
Venus108.20.7about three quarters of a step
Earth149.61.01 step
Mars228.01.51 and a half steps
Jupiter778.55.2about 5 steps
Saturn1432.09.5about 9 and a half steps
Uranus2867.019.1about 19 steps
Neptune4515.030.1about 30 steps
  1. Set the Sun at the start of your tape or string. Stand with your heels at the Sun.
  2. Walk the steps for each planet in order, placing its card where your heel lands. Use half steps where the table says.
  3. Place the asteroid belt card between Mars and Jupiter.
  4. Measure the gap from the Sun to Mars, and the gap from Saturn to Uranus. Record both in your Sky Log.
  5. Stand at Neptune and look back at the Sun. Write what the inner planets look like from there.
  6. Short hallway backup: use one foot length, heel to toe, instead of one step. Neptune is then 30 foot lengths away.
GapMeasured lengthWhat I noticed
Sun to Mars (all four inner planets)
Mars to Jupiter (across the asteroid belt)
Saturn to Uranus
Uranus to Neptune
PREDICT, THEN CHECK
  • Read the question.
  • Tap your answer.
Before you walk: which gap will be longer?
How many planets fit within the first two steps from the Sun?

What the model gets right and wrong

Right: the spacing. The inner planets crowd close to the Sun and the outer planets spread far apart, exactly as the fact sheet shows.

Right: the order. Every card is in its true place from the Sun.

Wrong: the sizes. Your cards are all the same size. Real planets differ enormously, which is next week's topic.

Wrong: the shape. Your model is a straight line. Real planets orbit all the way around the Sun, and are rarely lined up.

Model claimTrue or false?
One step in the model stands for 150 million kilometers.?
The four inner planets all fit within two steps of the Sun.?
The gap from Saturn to Uranus is shorter than the gap from the Sun to Mars.?
The model shows the planets' true sizes.?
WHY THIS EXERCISEKnowing what a scale model shows and hides is part of using it as evidence.
WALKING OUT FROM THE SUN
  • Tap a card.
  • Then tap its spot.
1First
2Second
3Third
4Fourth
5Fifth
Try this
Walk the model again with a shorter scale: one foot length per AU. Does the pattern of crowding and spreading stay the same?
Write what changed and what stayed the same when the scale changed.
Draw your walked model from above as a line of dots. Keep the gaps in proportion. Label the Sun, Earth, the asteroid belt and Neptune.

Careful measuring. Tomorrow you read the full NASA distance table and compare the planets in numbers.

← Tuesday