accretion    earth's moon    formation    formation of the moon    george darwin    giant impact hypothesis    how the moon was formed    how was moon created    lunar origin    moon    moon formation    moon origin    moon origins    origin of our moon    origin of the moon    origin of the moon and earth    origin of the solar system early theories    origins of the moon    planet hit earth    reginald daly    simulation    solar system    space science    the moon    theia    where did the moon come from    where is moon from