[ Pobierz całość w formacie PDF ]

all other bodies is composite and relatively slow, for the reason
that each is moving on its own circle with the reverse motion to that
Get any book for free on: www.Abika.com
ON THE HEAVENS 35
of the heavens. This at once leads us to expect that the body which
is nearest to that first simple revolution should take the longest
time to complete its circle, and that which is farthest from it the
shortest, the others taking a longer time the nearer they are and
a shorter time the farther away they are. For it is the nearest body
which is most strongly influenced, and the most remote, by reason
of its distance, which is least affected, the influence on the intermediate
bodies varying, as the mathematicians show, with their distance.
Part 11
With regard to the shape of each star, the most reasonable view is
that they are spherical. It has been shown that it is not in their
nature to move themselves, and, since nature is no wanton or random
creator, clearly she will have given things which possess no movement
a shape particularly unadapted to movement. Such a shape is the sphere,
since it possesses no instrument of movement. Clearly then their mass
will have the form of a sphere. Again, what holds of one holds of
all, and the evidence of our eyes shows us that the moon is spherical.
For how else should the moon as it waxes and wanes show for the most
part a crescent-shaped or gibbous figure, and only at one moment a
half-moon? And astronomical arguments give further confirmation; for
no other hypothesis accounts for the crescent shape of the sun's eclipses.
One, then, of the heavenly bodies being spherical, clearly the rest
will be spherical also.
Part 12
There are two difficulties, which may very reasonably here be raised,
of which we must now attempt to state the probable solution: for we
regard the zeal of one whose thirst after philosophy leads him to
accept even slight indications where it is very difficult to see one's
way, as a proof rather of modesty than of overconfidence.
Of many such problems one of the strangest is the problem why we find
the greatest number of movements in the intermediate bodies, and not,
rather, in each successive body a variety of movement proportionate
to its distance from the primary motion. For we should expect, since
the primary body shows one motion only, that the body which is nearest
to it should move with the fewest movements, say two, and the one
next after that with three, or some similar arrangement. But the opposite
is the case. The movements of the sun and moon are fewer than those
of some of the planets. Yet these planets are farther from the centre
and thus nearer to the primary body than they, as observation has
itself revealed. For we have seen the moon, half-full, pass beneath
the planet Mars, which vanished on its shadow side and came forth
by the bright and shining part. Similar accounts of other stars are
given by the Egyptians and Babylonians, whose observations have been
kept for very many years past, and from whom much of our evidence
about particular stars is derived. A second difficulty which may with
equal justice be raised is this. Why is it that the primary motion
includes such a multitude of stars that their whole array seems to
defy counting, while of the other stars each one is separated off,
and in no case do we find two or more attached to the same motion?
On these questions, I say, it is well that we should seek to increase
our understanding, though we have but little to go upon, and are placed
Get any book for free on: www.Abika.com
ON THE HEAVENS 36
at so great a distance from the facts in question. Nevertheless there
are certain principles on which if we base our consideration we shall
not find this difficulty by any means insoluble. We may object that
we have been thinking of the stars as mere bodies, and as units with
a serial order indeed but entirely inanimate; but should rather conceive
them as enjoying life and action. On this view the facts cease to
appear surprising. For it is natural that the best-conditioned of
all things should have its good without action, that which is nearest
to it should achieve it by little and simple action, and that which
is farther removed by a complexity of actions, just as with men's
bodies one is in good condition without exercise at all, another after
a short walk, while another requires running and wrestling and hard
training, and there are yet others who however hard they worked themselves
could never secure this good, but only some substitute for it. To
succeed often or in many things is difficult. For instance, to throw
ten thousand Coan throws with the dice would be impossible, but to [ Pobierz całość w formacie PDF ]

  • zanotowane.pl
  • doc.pisz.pl
  • pdf.pisz.pl
  • szkla.opx.pl

    •