Raven spreads a printed table on the Sky Deck. "The textbook squeezes all of Earth's history into one calendar year."
"January first, Earth forms," Rocket reads. "Early March, first life. Then nothing until November?"
"What do you notice about December?" Raven asks. "Almost everything we know is in the last month."
Nova hovers over the bottom rows. "Each day of this calendar is 12.5 million years," she says. "Each second is 145 years."
Rocket counts on his fingers. "So the first people in the table arrive one minute before midnight on New Year's Eve."
Raven nods. "Read the whole table before you decide what matters." Nova hums. "Row by row."
The open textbook Physical Geology scales all 4,570 million years into one year. Earth forms on January 1 and the present is the last instant of December 31.
At that scale each day is 12.5 million years and each hour about 500,000 years. Each minute is 8,694 years and each second 145 years.
Here is the textbook's table of events, shortened. Read every row before you answer.
| Event from the textbook | Approximate date | Calendar equivalent |
|---|---|---|
| Formation of oceans and continents | 4.5 to 4.4 billion years ago | January |
| First primitive life forms | 3.8 billion years ago | early March |
| First multi-celled animals | 600 million years ago | November 15 |
| Animals first crawl onto land | 360 million years ago | December 1 |
| Non-bird dinosaurs gone | 65 million years ago | December 26 |
| Most recent ice age begins | 2 million years ago | 8 p.m. on December 31 |
| Glacial ice retreats from southern Canada | 14,000 years ago | 11:58 p.m. on December 31 |
| First people arrive in western Canada | 10,000 years ago | 11:59 p.m. on December 31 |
The textbook says large organisms have existed for about 600 million years, a little over 13 percent of geological time.
Animals have been on land for 360 million years, about 8 percent. Mammals have dominated since 65 million years ago, about 1.5 percent.
The genus Homo has existed for about 2.8 million years, 0.06 percent of geological time.
Slow processes do big things over this much time. The Atlantic Ocean widens about 2.5 centimeters a year, and since 200 million years ago it has grown over 5,000 kilometers.
| Statement | True or false? |
|---|---|
| Animals have been on land for about 8 percent of Earth's history. | ? |
| Humans have existed for most of Earth's history. | ? |
| The Atlantic Ocean grew over 5,000 kilometers wide at about 2.5 centimeters a year. | ? |
| In the calendar model, mammals dominate from January. | ? |
Careful reading of a real table. Tomorrow you connect deep time to the rocks, layers and sky you already know.