Meteorology   

But the chief reason is that most of this stuff collects in the region

of the milky way.



8



Let us now explain the origin, cause, and nature of the milky way.

And here too let us begin by discussing the statements of others on

the subject.

(1) Of the so-called Pythagoreans some say that this is the path

of one of the stars that fell from heaven at the time of Phaethon's

downfall. Others say that the sun used once to move in this circle and

that this region was scorched or met with some other affection of this

kind, because of the sun and its motion.

But it is absurd not to see that if this were the reason the

circle of the Zodiac ought to be affected in the same way, and

indeed more so than that of the milky way, since not the sun only

but all the planets move in it. We can see the whole of this circle

(half of it being visible at any time of the night), but it shows no

signs of any such affection except where a part of it touches the

circle of the milky way.

(2) Anaxagoras, Democritus, and their schools say that the milky way

is the light of certain stars. For, they say, when the sun passes

below the earth some of the stars are hidden from it. Now the light of

those on which the sun shines is invisible, being obscured by the of

the sun. But the milky way is the peculiar light of those stars

which are shaded by the earth from the sun's rays.

This, too, is obviously impossible. The milky way is always

unchanged and among the same constellations (for it is clearly a

greatest circle), whereas, since the sun does not remain in the same

place, what is hidden from it differs at different times. Consequently

with the change of the sun's position the milky way ought to change

its position too: but we find that this does not happen. Besides, if