In Classical times, there were two major theories as to the existence of the Milky Way. The Pythagoreans thought it was residue left from the sun as it traveled that path (Darn that slimy residue.) Aristotle's Peripatetics believed it was formed of suspended exhalations. (Darn that morning breath.) There was a third theory according to William Hone ( a nineteenth century author on the subject), proposed by Democritus without the aid of a telescope. It was that the Milky Way contained innumerable fixed stars which caused the white trail in the sky. Of course, Galileo gets all the credit. Just because he almost got tortured or something.