democritus contribution to atomic theory

Epicurus later assigned different weights to the atoms, and argued that the heavier atoms moved at a different speed than the lighter ones. Leucippus explained that weight resulted from the size of the atoms and their combinations, but neither he nor Democritus seemed to have thought weight very important and they never committed the error that Aristotle made later, of arguing for the existence of absolute weight. The concept of weight and its opposite, lightness, was something the Greeks did not understand, for the force of gravity had not yet been defined. Small, perfect atoms gravitated towards the outside of the universe and formed the dome of the sky, whereas heavier atoms gravitated towards the center and formed earth. The atoms were perpetually spinning, like the 'seeds' of Anaxagoras, and as they collided some stuck together while others were forced apart. Atoms were atoma somata (bodies that cannot be divided). Each atom, however, which was so small as to be invisible, was itself a plenum, and could not be split. Parmenides had argued that the universe was a plenum filled with matter, and there was nothing else, but Leucippus and Democritus argued that the opposite of a plenum-a vacuum-also existed.

Some were large, some small, and some might be smooth and round and others might have an irregular shape. Leucippus and Democritus conceived of particles of matter called 'atoms' which moved through space like the flecks of dust that can be seen moving in a sunbeam. Although Democritus was a prolific writer, none of his works survive to the present day. Both men referred to Leucippus as the author of a work on the atomic theory titled the Great World System, although other philosophers-notably Epicurus (342–271 b.c.e.) and his followers-attributed this theory to Leucippus' pupil, Democritus of Abdera. He was recognized, however, by such philosopher greats as Aristotle, who headed the school known as the Lyceum in Athens of the fourth century b.c.e., and his successor Theophrastus. Unlike his predecessors, he is a shadowy figure, overshadowed by his more famous follower Democritus to such an extent that some Greeks even denied his existence. To escape from this logic, someone had to produce a theory to prove that empty space was not the same thing as the Eleatic's 'that which does not exist.' The philosopher who provided the necessary leap of imagination to get over this Eleatic idea was Leucippus of Miletus, the same city that fathered Thales, Anaximander, and Anaximenes who had started the long tradition of Greek speculation about the nature of the universe. In actuality, at any given point in its apparent flight, it is at rest. Parmenides' follower, Zeno, proved to his own satisfaction that an arrow in flight only appears to move. Thus there can be no motion, for motion implies that there is empty space into which an object in motion can move, and there is no empty space. Since the world is composed of matter which does exist, it fills all the available space. The Atomic Theory Escaping the Logic of the Eleatic School.īoth Empedocles and Anaxagoras attempted to evade the ruthless logic of Parmenides and the Eleatic School of philosophers who argued that there are two opposites, 'that which exists,' which is matter, and 'that which does not exist,' which obviously does not exist.

Democritus contribution to atomic theory