6.
3 Formation of the moon
Where did the Moon come from?
● In the early twentieth century, scientists thought that the
Moon was formed by splitting away from the Earth, soon
after the Earth was formed.
● The calculations showed that, if this theory was correct, the
Moon would still be slowly moving away from Earth.
● Accurate measurements made more recently have shown that
the Moon is still moving away from Earth – at a rate of about
4 cm each year.
● These calculations could not completely confirm the theory
that the Moon had formed by splitting away from the Earth.
● In 1974, it was suggested that the Moon was formed in a
different way. This is called the collision theory
Collision theory for formation of the Moon
● The collision theory (more commonly called the giant impact
hypothesis) is another theory of how the Moon was formed.
● There is more evidence that supports the collision theory than
any other current theory.
● The collision theory refers to a collision that happened relatively
soon after the formation of the Solar System.
● A newly formed planet, about the same size as Mars, collided
with the newly formed Earth.
● Scientists have called the colliding planet Theia.
● The picture – drawn by an artist – shows what the collision
between Earth (left) and Theia may have looked like.
● The collision would have caused rocks and dust to break away
from both planets.
● The theory states that Earth was formed from the two planets
joined together.
● The Moon was formed when the rocks and dust was pulled
together by gravity.
The Collision Theory
https://www.youtube.com/watch?v=e4JTdTxyDEo
https://www.youtube.com/watch?v=oSkiVcnoN5w
https://www.amnh.org/explore/videos/space/formation-of-the-moon
