Identify the following individual:

Lived: c. 460 - c. 370 BCE
They devised an atomic theory featuring tiny particles always in motion interacting through collisions, advocated a universe containing an infinity of diverse inhabited worlds governed by natural, mechanistic laws rather than gods, deduced that the light of stars explains the Milky Way’s appearance, and discovered that a cone’s volume is one-third that of the cylinder with the same base and height.