Harvard scientists, Sarah Stewart and Matija ─ćuk, have suggested that the Moon is made up of more of the Earth than we previously thought. The new theory says that the Moon was once part of the Earth that spun off after a giant collision with a planetary body half the size of Mars moving at 12-miles-per-second.
Wait a minute. Isn't that the way the moon was already theorized to be created? Not exactly. The old theory said that a Mars-sized object smashed into the earth and the resulting debris from both planetary bodies formed the moon. The new theory suggests that the object was moving so fast, it completely vaporized and a huge chunk of our planet, and only our planet, spun off to create the moon. This would explain why the Earth and Moon have similar composition and chemistry.
The Earth was also spinning much faster at the time, with a day being only two to three hours, and because of the faster rotation, enough material was launched after the collision to form the Moon. The Earth slowed down after interaction between its orbit around the Sun and the Moon's orbit around the Earth.
The collision might have looked something like this:
Yikes. I'm really glad we weren't there to witness this event.