same weight as Hiero’s crown, one of gold, the other of silver, and measuring the
amount of water displaced when each was immersed. This led to the Archimedes’
principle as dryly expressed in his treatise On Floating Bodies:
Solids heavier than the fluid will, if placed in the fluid, be carried down to the
bottom of the fluid, and they will be lighter in the fluid by the weight of the amount
of fluid that has the same volume as the solid.
(Proposition 7)He made advances in statics, ‘the science relating to weight and its mechanical
effects, and to the conditions of equilibrium as resulting from the distribution of
weight’; hence the significance of his famous remark ‘give me a place to stand and I
will move the earth’. Through his interest in hydrostatics (statics in relation to liquids)
he has been credited with the invention of a screwpump, duly called the Archimedean
screw.
Hipparchus from Bithynia (fl 240) made advances in trigonometry and in
astronomy making the science less theoretical and more practical by observing actual
measurements over time and so making it possible to predict celestial positions for
a given time. For this he invented instruments himself. He discovered the precession
of the equinoxes defined in the Oxford English Dictionaryas ‘the earlier occurrence of
the equinoxes in each successive sidereal year, due to the retrograde motion of the
equinoctial points along the ecliptic, produced by the slow change of direction in
space of the earth’s axis which moves so that the pole of the equator describes a circle
around the pole of the ecliptic once in about 28,500 years’. He was the first to
calculate accurately the distance of the moon from the earth. Hipparchus worked
with a geocentric model of the universe and did not adopt the heliocentric hypothesis
of his older contemporary Aristarchus of Samos, which remained unregarded in the
Greek world. In his computations he made use of the methods of the Babylonians,
who had a particular reputation in the ancient world in the study of mathematics and
astronomy.
One area of invention in which there was progress in Hellenistic times was to do
with weaponry:
Success in this work was recently achieved by the Alexandrian engineers, who
received considerable support from kings who were eager for fame and well
disposed to the arts and crafts.
(Philo, On Artillery Construction, 3, 50)Increasingly effective ballistic mechanisms of gigantic proportions were invented for
siege warfare. But in science generally, progress was limited by lack of any effective
PHILOSOPHY 217