Collision Hypothesis -- 1997
A catastrophic collision lead to the formation of the Moon
- Body about the size of Mars collided with earth 4.5 b.y. ago
- Most of body swallowed by earth
- Debris from collision orbited earth
- Moon coalesced (accreted) from this material
- tidal forces caused moon to move away
- Earth’s rotation slowed from ~ 6h to present 24h day)