Anaxagoras, that the sun moving under the earth and not being able to enlighten every place, the shadow of the earth, being cast upon the part of the heavens, makes the galaxy.
Democritus, that it is the splendor which ariseth from the coalition of many small bodies, which, being firmly united amongst themselves, do mutually enlighten one another.

Aristotle, that it is the inflammation of dry, copious, and coherent vapor, by which the fiery mane, whose seat is beneath the aether and the planets, is produced.

Posidonius, that it is a combination of fire, of finer substance than the stars, but denser than light..