PYTHAGOREAN ASTRONOMY 
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attributed spherical shape to the earth (as to the universe) 
for the simple reason that the sphere is the most beautiful 
of solid figures. For the same reason Pythagoras would 
surely hold that the sun, the moon, and the other heavenly 
bodies are also spherical in shape. (2) Pythagoras is credited 
with having observed the identity of the Morning and the 
Evening Stars. (3) It is probable that he was the first to 
state the view (attributed to Alcmaeon and ‘ some of the 
mathematicians’) that the planets as well as the sun and 
moon have a motion of their own from west to east opposite 
to and independent of the daily rotation of the sphere of the 
fixed stars from east to west. 1 Hermesianax, one of the older 
generation of Alexandrine poets (about 300 B.C.), is quoted as 
saying: 
‘ What inspiration laid forceful hold on Pythagoras when 
he discovered the subtle geometry of (the heavenly) spirals 
and compressed in a small sphere the whole of the circle which 
the aether embraces.’ 2 
This would seem to imply the construction of a sphere 
on which were represented the circles described by the sun, 
moon and planets together with the daily revolution of the 
heavenly sphere; but of course Hermesianax is not altogether 
a trustworthy authority. 
It is improbable that Pythagoras himself was responsible 
for the astronomical system known as the Pythagorean, in. 
which the earth was deposed from its place at rest in the 
centre of the universe, and became a ‘ planet ’, like the sun, 
the moon and the other planets, revolving about the central 
fire. For Pythagoras the earth was still at the centre, while 
about it there moved (a) the sphere of the fixed stars revolv 
ing daily from east to west, the axis of rotation being a 
straight line through the centre of the earth, (b) the sun, 
moon and planets moving in independent circular orbits in 
a sense opposite to that of the daily rotation, i. e. from west 
to east. 
The later Pythagorean system is attributed by Aétius 
(probably on the authority of Theophrastus) to Philolaus, and 
1 Aet. ii. 16. 2, 3 (Vors. i 3 , p. 132. 15). 
2 See Athenaeus, xiii. 599 A. 
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