1 The Birth of Science - MSRI

70 3. Other Hellenistic Scientific Theories
One important technical application of pneumatics was the pressure
pump. Vitruvius has left us a description of it taken from the Commentaries
of Ctesibius, to whom he attributes the pump’s invention. 88 (He refers the page 105
reader to the same work on the subject of several other air-operated machines.
89 ) The design is that of today’s two-piston, two-phase pumps. Its
construction was made possible by the introduction of a new element, the
valve, which became crucial in all later technology.
3.6 Aristarchus, Heliocentrism, and Relative Motion
Starting in the fourth century B.C., scientific astronomy developed in close
connection with mathematics. The greatest astronomers we know of were
Eudoxus of Cnidus (whose mathematical accomplishments we have already
mentioned), Callippus and Heraclides of Pontus in the fourth century;
Aristarchus of Samos, Conon of Samos 90 and Archimedes 91 in the
third; Apollonius of Perga (better-known for his treatise on conic sections)
between the third and second; and Seleucus and Hipparchus in the second page 106
century B.C. After that astronomical research stops.
Of all the astronomical works of the scientists mentioned so far, only
two remain, both altogether minor: Aristarchus’ On the sizes and distances
of the sun and moon, already mentioned, 92 and Hipparchus’ Commentary on
the Phenomena of Aratus and Eudoxus, containing a critical commentary on
Aratus’ poem and saved thanks to the latter’s popularity. To these one can
add a famous passage in Archimedes’ Arenarius describing the heliocentric
theory of Aristarchus of Samos. The information contained in these
writings is meager. Aristarchus’ surviving work, indeed, gives us a sense
88 Vitruvius, De architectura, X, vii, 1–3. A variation, used as a hydrant, is described by Heron
(Pneumatica, I, xxviii). A description of a vacuum pump contained in the Arabic text of the Pneumatica
of Philo of Byzantium (chapter lxiv) seems to be by Arabic hands and has scarce technical
value.
89 The clocks and pumps that Vitruvius describes are, he says, the “most useful” among the devices
in the Ctesibian Commentaries (ibid., 5); the others he dismisses as very ingenious but meant
solely for amusement. The contents of the first chapters of the Pneumatica of Philo, whose main
source was certainly Ctesibius’ work, may suggest that some of those “useless” devices might in
reality have been designed for experimental demonstrations (see page 68).
90 Conon is best known because Callimachus, in a famous short poem translated by Catullus,
mentions him as having explained the motion of heavenly bodies (Coma Berenices = Catullus 66, 1–
7; a fragmentary Greek text has been found on papyrus: Callimachus, fr. 110 Pfeiffer). One imagines
that he made important contributions to science, since Archimedes mentions him admiringly more
than once (Quadratura parabolae, 164, 1–12; De sphaera et cylindro, I, 9, 12–15; De lineis spiralibus, 8,
12–20) and Apollonius of Perga stresses the importance of some of his theorems on conics (Conics,
preface to Book IV; the passage is quoted on page 176).
91 The astronomical activities of Archimedes are attested by references in his extant works and
by a passage of Hipparchus reported by Ptolemy (Almagest, III, i, 195).
92 See page 58 and footnote 45 thereon.
Revision: 1.13 Date: 2002/10/16 19:04:00