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Earth and Space 6-8 / Week 07 / Sky Night
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Week 07 · How Far: Distances

Sky Night

Sky Night: The family walk
// Walking the solar system one step at a time
⏱ about 20 min

Sky Night: The Family Walk

At dusk the crew lines up planet cards along the porch rail with a grown-up. There is no Moon in the sky yet.

Raven writes the date in the Moon log. "What do you notice? Waxing gibbous last Saturday, so it is past full now. A waning gibbous rises after sunset."

"Our walk tonight is indoors," Rocket says, "so nobody trips in the dark." He lays the string down the hallway.

A younger cousin takes one step from the Sun and stops. "Earth already?"

"Already," Raven says. "Now walk to Neptune. Keep counting."

Nova hovers at the far end with her light on the floor, never in anyone's eyes. "Thirty," she says when the cousin arrives. "Welcome to the edge."

  1. The average Earth to Sun distance, about 150 million kilometers, is one astronomical unit.
  2. A scale shrinks every distance by the same rule. One step per AU puts Earth at one step and Neptune at about 30.
  3. The four inner planets crowd within two steps of the Sun. The four outer planets spread far apart.
  4. The NASA fact sheet shows the gaps between planets growing larger farther from the Sun.
  5. Light takes about eight minutes to reach Earth from the Sun. A light-year is the distance light travels in one year.
  6. Spacecraft have flown past, orbited or landed on every planet. Distance decides how long each trip takes.
◇ SKY NIGHT: MOON CHECK AND THE FAMILY WALK
With a grown-up, go to your usual Sky Deck spot after dark. If the Moon is up, sketch it with the date. If not, write "not up" and the date.
Indoors, lay your string down a cleared hallway. Put the Sun at one end and hand out the planet cards.
Let each family member walk a planet to its place, using one foot length per AU if the hall is short.
From Neptune, ask everyone to look back at the cluster of inner planets. Ask what surprised them.
Cloudy night backup: the family walk is the whole show. Sketch the Moon from your last clear night instead.
For a grown-up
Please go outside together. Use a flashlight for the path and point it at the ground, never at anyone's eyes.
Stay in a known spot in the yard, on the porch or at a window. No one crosses a road or climbs for a better view.
Clear the hallway of shoes and toys before the walk. String stays flat on the floor and is picked up afterward.
Safety first
Night observation only with a grown-up, from the yard, a porch or a window.
Walk the model in a cleared hallway or yard away from roads. String stays on the floor, never around anyone.
SKY NIGHT CHECK
  • Read the question.
  • Tap your answer.
In the family walk, how many steps or foot lengths is Earth from the Sun?
Which group of planets looks like a tight cluster from Neptune?
Draw the Moon as you saw it tonight, or as you expect it from your log. Beside it, draw the hallway model as a line of dots.

Well done, crew. Next week the planets get their true sizes, and you cut them out of paper.

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