The Art of Navigation

Another reason, according to Aristotle, why the heaven must be round.

reasons to prove that the heaven is round. The first is that to the
first and most noble body, the first and most noble
shape must be given: now, the most noble and first
body is the heaven, and the round shape is the most perfect:
therefore, the spherical shape is owed to the heaven. The second
reason is that nature has given to each
The circular shape is the most noble of all others.

body a shape proportioned to its functions, as is apparent in ani-
mals and plants: and because the proper work of the heaven is to
move continually in a circle, it was fitting that it
had a shape appropriate to such movement, such as the round
one, which has no corner or angle to hinder its motion. Al-Farghani. Al-Farghani original: "Alphragan"; referring to the 9th-century Persian astronomer Al-Farghani, whose work was a primary source for European knowledge of Ptolemaic astronomy. says:
If the heaven were flat, one part of the heaven would be closer to us
than the other, such as that which is directly over our heads: so that
a star located in that place would be closer to us than one in the
East or the West. And as things that are
closer to us seem to be larger, it would seem that the star
at the mid-heaven The zenith, or the highest point directly above the observer. would be larger than the one in the East
or West. Yet we see the opposite: for the Sun, or any other
A notable point.

star, seems larger in the East or in the West than
in the middle of the sky: the cause is not that the Sun or star
is larger or smaller, nor that it is farther or
closer to us, but because of certain vapors that rise and
place themselves between our sight and the Sun or star: and as
such vapors are thick bodies, they refract original: "rabatent"; literally "beat back" or "diminish." In this context, it refers to the bending or scattering of light rays. the rays of our sight,
so that we cannot perceive the thing in its proper size;
just as appears with a coin thrown into clear water, which,
due to the scattering of the rays A 16th-century explanation of refraction., seems to be larger than it is:
so it is with the Sun or other stars when vapors are inter-
posed between them and our sight.

On the nobility of the heaven, and of its color.

CHAPTER IIII.

An ornamental woodcut drop cap "A" is decorated with intricate leaf and vine patterns.
Aristotle says that the nobility of the heaven is understood and
considered by the clarity of its transparency, by the round-
ness of its form, by the unity of its regularity, by the
power of its movement, and by the height of its situ-
ation, which is very far removed from the center of the earth:
for in the dimension of its quantity, it surpasses
all imagination and measure of reason: and there is nothing in nature that
resembles it, nor can anything be compared to it in terms of power.
The heaven is not made of any element, nor does it hold their qualities, nor is it com-
posed of them: for then it would be corruptible, because all things