As the brightest object in night sky, the Moon has guided people for Millennia by defining the rhythms of life and animating our myths. The nature of the Moon began to come into focus 4 Centuries ago. To some philosophers, the moon was a perfect, crystalline sphere of divine substance, free of Earth imperfections.

Galileo Galelei noted mountains and valleys on the moon, features like those of Earth. The so called Fission theory made by George Howard Darwin son of Charles Darwin, held that the Moon was once part of earth, cast off by rapid spin of its young parent.