1. Summary

This video highlights specific events which lead to the formation of the Earth and Moon. It discusses how the protoplanetary disk accreted into larger bodies called protoplanets, the major collision between Earth and Theia, results of this collision, and the phenomenon of tidal locking. It gives the audience a brief understanding of how these events led to the formation of the current Earth and Moon.

2. Why Watch This Video?

• Have you ever wondered about the relationship between the formation of the Earth and Moon?
• Would you like to know the role of gases and dust leading up to the formation of the Earth and Moon?
• Have you ever been confused as to what exactly happens when the Moon recedes from the Earth each year?

3. Key Terms

• Protoplanetary Disk: A rotating disk of gases and dust that orbit a newly formed star, from which planets are (hypothesized to be) formed. Encyclopedia of Astrobiology
• Tidal locking: The phenomenon by which a body has the same rotational period as its orbital period around a partner. For example; the Moon is tidally locked to the Earth because it rotates in exactly the same time as it takes to orbit the Earth. BBC Science Focus
• Protoplanets: Small collection of matter that grows and becomes planets through the process of condensation.

4. Loose Ends

Loose end #1: Earth and Theia Collision

The “giant-impact hypothesis” was the collision of Early Earth and Theia (Mars-sized body). This collision spread vaporized chunks of the young planet’s crust into space. Gravity played a role in binding together the ejected particles and created the Moon. According to Nasa, “when the young Earth and this rogue body collided, the energy involved was 100 million times larger than the much later event believed to have wiped out the dinosaurs.” Almost 60% of Earth’s material is made up of Theia’s material. The Earth and Moon are almost similar in terms of their composition. Space: How Was the Earth Formed?

Loose end #2: What does the Earth’s atmosphere consist of?

The Earth’s atmosphere consists of 78% nitrogen, 21% oxygen and 1% other gases such as neon, carbon dioxide and argon. The atmosphere contributes to the Earth’s long-term climate, short-term local weather and protects against harmful radiation being emitted from the Sun.

Loose end #3: What is the proper structure of the Earth?

The Earth is composed of four main layers starting with: inner core, outer core, mantle and crust. The inner core is made up of nickel metals and the temperature can reach up to almost 9800 degrees Fahrenheit. The inner core is surrounded by the outer core. This layer is 1400 miles thick. Between the outer core and crust is the mantle. This is the thickest layer. It consists of molten rock that is 1800 miles thick. Lastly, the crust goes about 19 miles deep on an average land. At the bottom of the ocean, the crust is thinner.

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