Date: Lived 460-370 BCE
Contribution: He hypothesized that the physical world was made up of an infinite amount of moving atoms and claimed that atoms are all the same except for in shape, arrangement, position, and magnitude.
Observations: He broke sea shells in half continuously until he ended up with powder. He also adopted the theory from his teacher Leucippus.
Discovery: Everything is made up of atoms, they are indestructible, they are always moving, and between atoms is just empty space.