← Back to course
Earth and Space 6-8 / Week 11 / Wednesday
3/6
Week 11 · Earth's Long Story

Wednesday

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

Wednesday: Sky Deck Lab: Unroll the Timeline

The hallway is cleared. Rocket holds the roll at the far wall. "Sheet one. Earth forms. Go!"

Raven walks backward, counting sheets out loud as the paper unrolls flat along the floor. "Ten. Twenty. Thirty."

Nova glides above the paper. "Stop at 38 from the end," she says. "The textbook puts the first simple life there."

"That is still eight sheets from Earth's start," Rocket says. "And nothing we would recognize for ages."

Raven reaches the last sheet and kneels. "What do you notice? Everything with legs, leaves or feathers fits here."

Rocket measures with a ruler. "Humans are three millimeters." Nova hums. "Now you have felt deep time."

Your mission

Today you build a scale model of time. Each sheet of paper stands for 100 million years, so 46 sheets make 4,600 million years.

You will place Earth's milestones from the textbook table at the right sheet, then measure the human sliver.

Milestones go on sticky notes or paper tags laid on the sheets, never written on the floor.

  • A roll of toilet paper or adding-machine tape, at least 46 sheets or about 5 meters
  • Eight sticky notes or paper tags and a pencil
  • A ruler with millimeter marks and a tape measure if your family has one
  • A cleared hallway, long room or yard path, and your Sky Log
Safety first
Unroll in a cleared hallway, room or yard away from roads. Walk, do not run, beside the paper.
The paper stays on the floor. It is never wrapped around anyone or pulled tight between people.
Roll it back up when you finish so no one trips. Recycle or reuse the paper.
  1. Mark sheet 1 with a tag that says "Earth forms, 4,600 million years ago." Hold that end at the far wall.
  2. Unroll 46 sheets flat along the floor, counting each one. The loose end is the present day.
  3. Count 38 sheets back from the present and lay a tag: "first simple life, 3,800 million years ago."
  4. Count 6 sheets back from the present: "first multi-celled animals, 600 million years ago."
  5. Measure 3.6 sheets back from the present: "animals first crawl onto land, 360 million years ago."
  6. On the last sheet, measure about two thirds of a sheet back: "dinosaurs gone, mammals spread, 65 million years ago."
  7. Measure the length of one sheet in millimeters. Divide by 100 to find how long 1 million years is on your roll.
  8. Humans of the genus Homo appeared about 2.8 million years ago. Multiply your millimeters per million years by 2.8 and mark that sliver at the very end.
  9. Fill in the data table, then roll the paper back up.
PREDICT BEFORE YOU UNROLL
  • Read the question.
  • Tap your answer.
Where will the first simple life tag land?
Which milestones will all crowd onto the last sheet?
Milestone from the textbookYears agoSheets back from the presentYour measured position (mm from the end)
Earth forms4,600 million46
First simple life3,800 million38
First multi-celled animals600 million6
Animals first crawl onto land360 million3.6
Dinosaurs gone, mammals spread65 million0.65
Genus Homo appears2.8 million0.028

Reading the roll

The textbook table puts the first primitive life about 3.8 billion years ago. The first multi-celled animals came about 600 million years ago.

Animals first crawled onto land about 360 million years ago. The non-bird dinosaurs were gone by 65 million years ago.

The genus Homo has existed for about 2.8 million years. The textbook says that is 0.06 percent of geological time, about one part in 1,600.

On a roll with sheets about 10 centimeters long, that is close to 3 millimeters. The most recent ice age ended around 11,700 years ago, far thinner than a pencil line.

What the model showsTrue or false?
Most of the roll has no multi-celled animals on it.?
Humans take up about half the roll.?
One sheet stands for 100 million years.?
The model shows the order and the proportions of Earth's history.?
WHY THIS EXERCISEThe model makes the proportions visible, which is what a number alone cannot do.
How many sheets back from the present is the first multi-celled animal tag? Type a number.
WHY THIS EXERCISESix sheets out of 46 shows how recent visible life is.
Sketch your unrolled timeline as a long strip. Mark the six tags and shade the empty stretch before life.

You have walked 4.6 billion years. Tomorrow you read the textbook's own calendar of Earth's history.

← Tuesday