335–ca. 405 c.e.) wrote commentaries on Ptolemy’s Almagest
and was the father of Hypatia, the fi rst well-known female
mathematician. Marinus of Neapolis (ca. 450–ca. 500 c.e.)
speculated on the nature of the Milky Way, arguing that it
could not be a collection of very faint stars, a theory that dat-
ed back to the fi ft h century b.c.e.
ROME
BY JOHN M. MCMAHON
Scientifi c astronomy did not occupy as important a position
in Rome as it held in Greece, but knowledge of the heavens
remained a major factor in the intellectual, social, cultural,
and political life of the Roman world. Early contact with
Etruscan civilization in Italy and later with Hellenistic Greek
civilization in the Mediterranean infl uenced attitudes to-
ward astronomy throughout the Roman period. Th e Romans’
own practical nature, which favored applied knowledge over
theoretical science, largely determined the role astronomy
played. Roman writers oft en included astronomical subject
matter in literary works, and by recording the discoveries of
the Greeks, Roman technical writers ensured that scientifi c
astronomical knowledge reached both Roman readers and
those of later ages.
During their earliest history the Romans incorporated
the monthly lunar cycle into a formal calendar, a concept
that may have originated with the Etruscans. Made up of
10 months (March through December), it had an unnamed
period of time during the winter. King Numa Pompilius
(ca. 715–ca. 672 b.c.e.) added two additional months,
January and February, to fill the gap. Since the annual so-
lar cycle is not compatible with a purely lunar calendar,
numerous adjustments to the Roman civil calendar were
made over the centuries. Finally, in 46 b.c.e. Julius Cae-
sar (100–44 b.c.e.), advised by the Greek astronomer Sosi-
genes, refashioned the Roman calendar by basing it on the
sun’s apparent yearly motion.
Roman farmers incorporated knowledge of the heavens
into agricultural activities and relied on recurring seasonal
events in the sky to indicate appropriate times for plowing,
sowing, and harvesting. Th ese times were marked by the ob-
servable annual rising or setting of specifi c stars and constel-
lations, which were noted on a parapegma, or “star calendar.”
Cato the Elder (234–149 b.c.e.) refers to such information in
his De agri cultura (On Agriculture). Th e writings of later au-
thors on farming practices, such as Varro (ca. 40 b.c.e.) and
Columella (ca. 60 c.e.), reveal the transition from the use of
astronomical information to the Julian civil calendar.
In the Roman world at large other practical applications
of astronomical information were common. Seafaring and
navigation, a major component of trade and commerce, nec-
essarily depended on astronomical principles and a familiar-
ity with the starry sky. Among a variety of astronomically
oriented instruments developed by Greek science during
the Roman period, such as the astrolabe (a two-dimensional
working model of the heavens) and the celestial globe, sundi-
als were by far the most commonly used. Th ese instruments
came in a wide range of sizes and applications, both public and
private. Surviving examples of the latter indicate that some
were even designed for use as portable personal timepieces.
Public sundials were also set up, the most famous being the
enormous Horologium Augusti of the emperor Augustus in
Rome’s Ca mpus Mar tius, which ser ved as a politica l as wel l as
calendrical monument.
During a period of close cultural assimilation in the
seventh and sixth centuries b.c.e. the Romans adopted from
the Etruscans the practice of observing the heavens to ascer-
tain the will of the divinities, to interpret past events, and to
predict future ones. In accordance with carefully prescribed
rules, the visible sky was divided into specifi c regions to de-
termine what celestial occurrences might mean for human
aff airs. Such traditional practices became an essential part
of Roman religious and civic custom. Th e tendency to rec-
ognize in the movements of the heavenly bodies an infl uence
on people’s lives became common in the Roman world with
the spread from the East of the pseudoscience of astrology.
Manilius (early fi rst century c.e.) composed an entire didac-
tic poem (a poem meant to instruct the reader) on astrology
called Astronomica (Astronomical Matters), and many lead-
ing fi gures were believers in the effi cacy of astrology.
From the third through fi rst centuries b.c.e. the Romans
were increasingly exposed to a more purely scientifi c ap-
proach to astronomy through their expansion into the Greek
cultural sphere. Th is contact occurred fi rst in southern Italy
and Sicily and subsequently on mainland Greece and in Asia
Minor, long the home of thriving centers of learning. An im-
portant Roman from this period was Sulpicius Gallus, who
wrote a work on astronomy based on Greek sources. His sci-
entifi c knowledge of mathematical astronomy was such that,
as an offi cer in the Roman army in 168 b.c.e., he predicted a
lunar eclipse before the battle of Pydna.
Intercultural contact with the Greek world also intro-
duced to the growing Roman intellectual class those philo-
sophical and literary elements associated with knowledge of
the heavens. Th e foremost example of this process was the
Phaenomena (Appearances) by Aratus (ca. 315–240 b.c.e.),
a lengthy didactic poem based on the earlier work of the
astronomer Eudoxus (ca. 400–ca. 350 b.c.e.). Combining
astronomical subject matter with Stoic philosophy, Aratus
proposed that the orderliness of the heavens was evidence of
divine intent in the universe. Th e Phaenomena became very
popular throughout antiquity and greatly infl uenced a num-
ber of Roman authors, including Cicero (106–43 b.c.e.) and
Ovid (43 b.c.e.–17 c.e.), both of whom wrote Latin versions of
the poem. On the other hand, the Roman poet Lucretius (ca.
94–55 b.c.e.) enlisted astronomy in support of Epicurean phi-
losophy, which he expounded in his work De rerum natura
(On the Nature of Th ings).132 astronomy: Rome