If I recall correctly, it was only when chemists started noticing that the outputs of chemical reactions tended to factorize a certain way, which is to say that it took millennia after Democritus to get the point where the atomic hypothesis started making clearly relevant experimental predictions.
IIRC, even then, plenty of people considered it somewhat speculative, and it didn’t become universally accepted until Einstein’s explanation of Brownian motion.
IIRC, even then, plenty of people considered it somewhat speculative, and it didn’t become universally accepted until Einstein’s explanation of Brownian motion.