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Earth and Space 6-8 / Week 11 / Sky Night
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Week 11 · Earth's Long Story

Sky Night

Sky Night: Walk the timeline
// Four and a half billion years on one roll of paper
⏱ about 20 min

Sky Night: Walk the Timeline

Saturday evening, the crew unrolls the timeline down the hall one more time, for the whole family.

"Earth forms here," Rocket says at the far wall. "Walk toward me. Say stop when you think life begins."

A grown-up stops far too soon. Raven grins. "Keep walking. Eight sheets in."

"What do you notice?" she asks when they reach the end. "All of us fit in three millimeters."

Nova glides to the porch door. "The Moon is up," she says. "It has been circling for most of this roll."

Rocket sketches its shape in the Sky Log. Nova hums. "Ancient Moon, young watchers."

  1. Earth is about 4.6 billion years old, 4,600 million years. The survey's best number is 4.54 billion with less than 1 percent uncertainty.
  2. The geologic time scale divides that history into eons, eras, periods and epochs. The eras are Paleozoic, Mesozoic and Cenozoic, ancient, middle and recent life.
  3. The three eras cover only the last 540 million years. The time before them is almost 90 percent of the story.
  4. On a 46-sheet roll, first life is 38 sheets back, multi-celled animals 6 sheets back, and humans about 3 millimeters.
  5. Slow processes build huge things given deep time: layers, mountains, oceans and new kinds of rock.
◇ FAMILY TIMELINE WALK AND MOON CHECK
Unroll the 46-sheet timeline down a hall or across the yard. Each family member guesses where life, land animals and humans go before the tags are placed.
Walk it together from Earth's formation to the present. At each tag, the youngest person reads it aloud.
If the sky is clear, sketch the Moon's shape from your known spot for the Moon log. If it is cloudy, write "cloudy" and the date.
Cloudy-night backup: use the one-year calendar instead. Each person finds their birthday's date and says whether life existed yet.
For a grown-up
Night observation happens only with you, from the yard, porch or a window, in a known spot. Bring warm clothes and a flashlight for the path.
The timeline is unrolled on a cleared floor or path away from roads and stays flat. Please roll it up afterward so no one trips.
The recap facts come from the United States Geological Survey at pubs.usgs.gov and the open textbook Physical Geology on geo.libretexts.org.
Safety first
Walk beside the paper, never on it, and never run in the hallway.
The paper stays on the floor and is never wrapped around anyone.
Stay in your known spot for the Moon. Never cross a road or climb for a better view. The flashlight points at the ground.
THINK IT THROUGH
  • Read the question.
  • Tap your answer.
A family member guesses life began halfway along the roll. Where does the textbook put it?
Which takes up more of the roll?
Sky Night checkTrue or false?
Each sheet of the roll stands for 100 million years.?
Humans appear on the first sheet.?
The Cenozoic era is the one we live in.?
WHY THIS EXERCISESaying the proportions aloud to your family is the best test that you understand them.
Draw your family walking the timeline. Mark where each person guessed life began and where it really goes.
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