Daughter theory of moon

The oldest of the four theories speculates that the moon was originally part of the earth, and was somehow spun off a rapidly spinning, partially molten, newly forming planet.
Once prevalent, this theory (sometimes referred to as the fission theory) has largely been rejected, because it does not explain how the proto-Earth could have been spinning with sufficient velocity to eject the material that became the moon. Moreover, it is highly unlikely that such an ejection would have put the moon into a stable Earth orbit.