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Formation of Earth

Earth formed from the solar nebula and contracted by gravity and differentiated; Moon formed when a giant asteroid struck Earth and flung material out into space.

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The Work of a Goddess

The Work of a Goddess

Credit: Jason Bache
Source: http://www.flickr.com/photos/jasonbache/4737761364/sizes/l/in/photolist-8dEgoL/
License: CC BY-NC 3.0

The Greek goddess Theia was the daughter of Earth (Gaia) and sky (Uranus). Theia gave birth to Selene, the goddess of the Moon. So Theia plays a big role in the Moon’s birth story.

Why It Matters

Credit: NASA
Source: http://en.wikipedia.org/wiki/File:As11-40-5886,_uncropped.jpg
License: CC BY-NC 3.0

Imagine being the first person to walk on the Moon! American astronaut Neil Armstrong claimed this title in 1969 [Figure2]

  • The Moon has been around for about 4.5 billion years.
  • The Moon is not an active planetary body, so there is some evidence of how it formed.
  • There are currently three hypotheses (hypothesis is the correct term) for how the Moon formed:
    • Capture Hypothesis: Earth’s gravity captured a passing asteroid
    • Co-formation Hypothesis: Earth and Moon formed at the same time
    • Giant Impact Hypotheses: A Mars-sized body collided with Earth and the Moon formed from the orbiting debris.

Explore More

With the links below, learn more about the formation of the Moon. Then answer the following questions.

  1. What is the evidence against the capture hypothesis?
  2. What is the evidence against the co-formation hypothesis?
  3. What is the evidence in favor of the giant impact hypothesis?
  4. How did the small planet of Theia cause the Moon to form?
  5. Why are Earth’s seasons evidence for this hypothesis for how the Moon formed?


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