When and Where did the Atomic Theory Come From?

[Rev. Rye]

This is actually a very complicated question:

• Leucippus (his historicity possible, but not proven) and his student Democritus developed the theory of the atom around the fifth century BC in an attempt at reconciling Heraclitus and Parmenides. Aristotle rejected atomic theory and so, with his ascendancy, atomic theory becomes dormant for over a millennium.
  
• Surprisingly, thinkers in India, most notably Kanada (and yes, that was his name), author of the Vaisesika Sutra, stumbled upon a very similar atomic theory to that of Democritus, and possibly even doing so before Democritus. That said, since Atoms weren't mentoned in the Vedas, it did not catch on in India until later.
  
• Near the end of the 18th Century, John Dalton, emboldened by the discovery of the Law of Conservation of Mass, starts work on figuring out the various elements, and even begins to figure out what they're made of and their relative size differences. He first does an oral presentation in 1803, publishes a paper in 1805, and fleshes it all out in 1808's A New System of Chemical Philosophy.
  
• And shit just gets more complicated from there...