The Earth before us

This is the longest era of all: it begins with the Big Bang, about 13.8 billion years ago, and runs until 7 million years ago. In this immense stretch of time the stars light up, and our galaxy, the Sun and the Earth are born. On Earth the oceans appear, along with the first living things, tiny and simple. Then come plants, fish, insects, dinosaurs, mammals and birds, while the continents drift and the climate changes many times. There were no human beings yet: we know about all this thanks to fossils, rocks and telescopes.

The era on a line: 25 events

1. about 13.8 billion years ago The Big Bang
2. about 13.5 billion years ago The first stars
3. about 13 billion years ago Birth of the Milky Way
4. about 4.6 billion years ago Formation of the Solar System
5. about 4.5 billion years ago Birth of the Earth
6. about 4.5 billion years ago Formation of the Moon
7. about 4.4 billion years ago The oldest pieces of Earth
8. about 4.3 billion years ago The first oceans
9. about 3.5 billion years ago The first life on Earth
10. about 2.7 billion years ago Cyanobacteria and photosynthesis
11. about 2.4 billion years ago The Great Oxidation Event
12. about 1.8 billion years ago The first complex cells
13. about 1 billion years ago The first many-celled living things
14. about 555 million years ago The Ediacaran creatures
15. about 539 million years ago The Cambrian explosion
16. about 475 million years ago The first plants on land
17. about 440 million years ago The first fish with jaws
18. about 400 million years ago The first insects
19. about 375 million years ago The first amphibians
20. about 320 million years ago Carboniferous forests
21. about 252 million years ago The great Permian extinction
22. about 230 million years ago The first dinosaurs
23. about 225 million years ago The first mammals
24. about 150 million years ago The first birds
25. about 66 million years ago Extinction of the non-avian dinosaurs

Did you know?

• If the whole history of the Universe lasted one year, the first dinosaurs would appear around Christmas and our species only in the last 12 minutes of 31 December.
• The sunlight you see right now left the Sun about 8 minutes ago: looking far out into space also means looking back in time.
• Tyrannosaurus and the sparrow on your balcony are relatives: both belong to the great family of theropod dinosaurs.

storiascopio.com/en/era/the-earth-before-us/ · free worksheet, you may photocopy it for your class

1. Put in order: write 1 next to the oldest and 5 next to the most recent.

• The first many-celled living things
• The first mammals
• The first insects
• The first oceans
• Birth of the Milky Way

2. Choose the right answer.

1. What happened with the Big Bang?

   • The Earth broke away from the Moon
   • Space itself began to stretch out
   • A bomb exploded in empty space
   • The Sun lit up first

2. Which gases made up the clouds where the first stars were born?

   • Hydrogen and helium
   • Carbon dioxide and steam
   • Oxygen and nitrogen
   • Methane and ammonia

3. According to the most widely accepted idea, how did the Moon form?

   • It was born from an icy comet
   • It was captured as it passed close to the Sun
   • It formed long after the dinosaurs
   • A body almost as big as Mars crashed into the Earth

4. Where have zircon crystals more than four billion years old been found?

   • In Italy
   • In Iceland
   • In Antarctica
   • In Australia

3. Match each one to what it brought to the Earth: write the right letter.

Storiascopio · texts by Ciro Simone Irmici, written with the help of AI and checked · sources in the online cards