Summary

In this video, they use a comparative method to help people grasp how old the Earth is. They utilize a timeline approach to key world events and compare them to current fractions of time such as a yearly calendar. Lastly, the video discusses the specifics around mass extinctions that took place on Earth and how they affected the world.

Why watch this video?

• Have you ever wondered how old the Earth is?
• Would you like to know how dinosaurs became extinct?
• Have you ever been confused by how old human life is compared to other species?

Key terms

Geological Timescale – A system for dividing Earth’s history into segments
Isotopes – Varieties of a chemical element having different numbers of neutrons
Fossil Record – Refers to viewing fossils as a tool for telling a story about what Earth was like at a given time

Loose ends

• A solar nebula is a cloud of dust and gas surrounding a new star. The planets in our solar system formed from such a cloud.
• When the video discussed unicellular organisms, it did not discuss what they were. Unicellular organisms are organisms that only consist of one cell.
• The Cambrian explosion was a period of time when numerous animal phyla and many new species appeared on Earth.