He was a Greek philosopher who published cosmological theories.
Even though he did not have the tools of contemporary science, his ideas about cosmic motion and the existence of multiple worlds became very popular.
He was the first to say that everything was together as one unit and the universe was an undifferentiated mixture. He also said that elements continuously move and separate. Thus the galaxies are moving away from each other, so the universe expands.
He also believed that there is life in other places of the universe.
[Source: www.greekreporter.com]
