1 The Birth of Science - MSRI

248 10. Lost Science
in before the interruption of scientific activities at Alexandria in 145–144
B.C. (and in particular that it was not documented in the Library).
Heron is one of the few authors whose writings contain ideas akin to
those that appear in our Plutarchan passage, and this is significant because
there is other evidence that he may have known Hipparchan works that
were not available to other Alexandrian scholars. 64 That may have been
a result of his well-attested familiarity with the Mesopotamian scientific
tradition: since we know of scholarly exchanges between Rhodes, where
Hipparchus worked, and the neighboring Seleucid kingdom, 65 it may be
suspected that the astronomer’s works appearing after the pogrom of 145– page 309
144 were preserved in the East better than in Egypt.
The theory we are considering, by unifying the study of the motion of
weights with that of heavenly bodies such as the moon and treating both
as particular cases of motion subject to a fora toward the center, performs
a synthesis of astronomy and ballistics. It is not surprising that such a synthesis
should be performed by Hipparchus, the greatest astronomer of his
time and a denizen of Rhodes, then the main center of ballistic studies. 66
Other evidence, in my opinion conclusive, is provided by Simplicius.
He tells us that Hipparchus wrote a work on gravity titled On bodies thrust
down because of gravity ( ). 67 This
is the same terminology used several times by Plutarch: the boulder, the
stream and so on are said to be “thrust down” because of gravity. And
though Plutarch introduces the theory with the words “thrust toward the
center” rather than “thrust down”, the equivalence of the two is implied
by the very fact that later in the dialogue there is an extensive critique of
the identification of a single incorporeal point (the center) with “down”
(). 68
Simplicius mentions Hipparchus’ theory in the case of an object thrown
straight up. The motion is clearly described as first an upward motion page 310
with decreasing velocity and then a downward motion with increasing
velocity. At this point Simplicius adds:
64 One such work may have been a source for Heron’s Dioptra; see note 42 on page 243.
65 For example, Hipparchus used Mesopotamian astronomical data.
66 Philo of Byzantium, Belopoeica, 51 = [Marsden: TT], p. 108.
67 Simplicius, In Aristotelis De Caelo commentaria, [CAG], vol. VII, 264, 25–26. That this work of
Hipparchus, unknown to many Alexandrian scholars, was familiar to Simplicius and (as we know
from the latter) to Alexander of Aphrodisias, both coming from Asia Minor, corroborates the conjecture
that some Hipparchan works fared better in the East than in Egypt.
68 Plutarch, De facie. . . , 925E–926B.
Revision: 1.11 Date: 2003/01/06 02:20:46