How did Democritus recognize that the Milky Way consists of a number of stars?

Answer 1

Democritus is often cited as the first person to propose atomic theory because he allegedly coined the word atom. In Greek, atom is formed of the bases "a" + "tomos", meaning "uncuttable" or "indivisible." The story goes that he coined this word by observing that any physical object can be made smaller by cutting it. For example, if you cut a table in half, you now have two smaller "tables." He reasoned that if you cut each of those halves in half, and then those quarters in half, and then those eighths in half, and kept going infinitely that eventually you would have to hit a point when the pieces of the original table were so small that you could not possibly cut them in half again. Hence the word atom. A thing which cannot be cut in half. Democritus was widely criticized and ridiculed for this view, I believe, but ultimately he was proven correct and modern atomic theory invented, albeit a little while after he could take credit. Democritus also, likely, used his conjecture of tables being made of uncuttable, little pieces to ask whether or not the Milky Way in the sky, too, could be made of stars so far away that they would appear to be one unbroken thing.

If this is an interesting topic to you, I would recommend also reading Lucretius' De Rerum Natura. This work takes a logical next step and, in essence, hypothesizes the way in which kinetic molecular energy (heat) and fluid dynamics work.