Added:
Democritus (Greek: ΔημόκÏιτος, DÄ“mokritos, "chosen of the people") lived approximately between 460 BCand 370 BC, so roughly it must have been about 420 BC, certainly not 250 BC as stated in this answers up till now.
he did not develop anything regarding the 'atomic theory' for he was against that theory.
He pubish is own atomic theory in 1803 developed his atomic theory by observations gathered from many experiments .
Democritus contributed to the atomic theory around 400 BC. He proposed that all matter is composed of indivisible particles called atoms.
john Dalton
Democritus, an ancient Greek philosopher, became renowned for his development of the atomic theory around the 5th century BCE. His ideas about the structure of matter laid the foundation for modern atomic theory.
he did not develop anything regarding the 'atomic theory' for he was against that theory.
Democritus achievements are his atomic theory and his book -on the little order of the world- which describes his atomic theory.
They both thought the same theory but Dalton had evidence to prove it, unlike Democritus.
democritus was greek philosophers.
the atomic theory of the universe
The ancient Greeks did not perform any experiments to test the atomic theory proposed by Democritus. To the ancient Greeks the atomic theory was a part of philosophy, not science.
460 b.C
400b.C.
2012
Democritus is known for his atomic theory, which he developed in the 5th century BC. His ideas were revolutionary for the time and laid the groundwork for modern atomic theory.
He pubish is own atomic theory in 1803 developed his atomic theory by observations gathered from many experiments .
460 b.C.