He produced works which concerned physics, astronomy, zoology, biology, ethics, mathematics, and grammar. However, he is best known for his expanding on the atomic theory of Leucippus. In this theory, Democritus says that everything is made up of atoms, even the soul. He also states that the universe is a purely mechanical system obeying fixed laws. The origin of the universe came about through atoms moving randomly and colliding to form larger bodies and worlds.
Space is infinite, having always existed and the number of atoms are also infinite.
On the topic of the creation of earth, Democritus said that the whirling motion of clustering atoms drove the heavier down and the lighter up and away from the center. And that this whirling cluster of atoms massed together to create solid earth. There is also evidence that Democritus was interested in the creation of life on earth, however there is no records of what he had to say on this matter. Democritus was a very interesting philosopher. He lived during a time of great learning and a number of different theories on how everything began, including life and the universe.