Roman government perceived it as reliable and useful. It re-
mained, however, the specialty of a few experts, usually those
of Greek descent and culture, oft en from the Greek popula-
tions and settlements of Asia Minor, Syria, and Egypt.
Th e ancient Romans also used armillary spheres, an as-
tronomical device that had moving parts and modeled the
movements of the heavenly bodies. Some scholars have sug-
gested t hat Nero’s Golden House conta i ned one. A n a rmi l la r y
sphere is depicted in a wall painting of a luxury villa from the
Stabiae (modern-day Castellammare di Stabia) region of It-
aly. Th e Roman elite liked to own gadgets and to demonstrate
an awareness of contemporary intellectual endeavor, but they
did not build their own.
GEOGRAPHY AND ASTRONOMY
Ptolemy, a Greek astronomer of the second century c.e. who
worked in Alexandria, is known for his theory on the mo-
tions of the stars and planets, which built upon earlier Greek
astronomy and became the accepted model of how the cos-
mos worked until the discoveries of Nicolaus Copernicus and
Johannes Kepler in the 16th and 17th centuries, respectively.
Ptolemy’s Geography gives the latitudes and longitudes of
over 8,000 places on the earth, just as astronomers located
the stars in the heavens through their celestial coordinates,
though not all of his information was accurate. He also de-
veloped a mathematical way to project the three-dimensional
world onto a two-dimensional surface such as a map.
Maps existed in ancient Rome but were probably not
oft en used by ordinary individuals for the purpose of fi nd-
ing their way about. More common were “itineraries,” which
listed the times it would take to travel between two places.
Geographical knowledge of the Northern Hemisphere in the
Roman period was quite detailed and extensive, especially of
the lands of the empire and, to a lesser extent, of the trade
routes to India and China. Th ere was a strong link between
geographical knowledge and imperial power, both ideologi-
cal and practical. To know a terrain well was to have some
control over it, especially from a military point of view. To be
able to display maps, such as the map of the empire that the
Roman general Agrippa (63?–12 b.c.e.) had carved in marble,
showed the general population the size and importance of
the empire and demonstrated the competence of the empire’s
leaders. Individuals may have known much less about the
world beyond the places that concerned them directly.
ASTRONOMY AND ASTROLOGY
Astrology was almost indistinguishable from astronomy in
the ancient world since its development in Ptolemaic Egypt
over the third to fi rst centuries b.c.e. Many astronomers
believed that the stars and planets infl uenced human lives.
Th e astronomer Ptolemy wrote Te t ra b i b l o s (Four Books) as
a scientifi c account of astrology. He thought that the heav-
enly bodies shaped earthly environments and so aff ected the
character of people according to what time of the year they
were born. Although not every event in a person’s life was
entirely determined in this way, a good astrologer could es-
timate the probability of certain events. For instance, a very
confi dent, adventurous person was more likely to die at sea.
Other astrologers and intellectuals had diff erent accounts of
how astrology worked or how rigidly deterministic it was.
Some viewed it as a matter of theology, contending that the
movements of the stars were messages from the gods.
Th ere were also skeptics, especially among intellectuals
such as the philosopher Favorinus (fl. second century c.e.),
who attacked inconsistencies in astrological theories, asking
why twins did not always have the same fate and pointing out
that many astrological predictions did not come true. Th e Ro-
man philosopher and statesmen Cicero (106–43 b.c.e.) gave
similar arguments in his dialogue De divinatione (On Divi-
nation), which discusses methods of predicting the future
through the observation of signs. It was, however, always pos-
sible to explain a false prediction by saying that the astrologer
was incompetent or that astrology, like medicine, is diffi cult
and that using it cannot always be done with perfect success.
Some astrological predictions could be self-fulfi lling, or iden-
tifi ed in retrospect. Th e horoscope of the emperor Augustus
(r. 27 b.c.e.–14 c.e.), drawn up aft er he had become ruler of
Rome, unsurprisingly predicted a remarkable career. Augus-
tus put his sign of Capricorn on some of his coinage.
Astrology could also be politically dangerous. Predic-
tions that the emperor would die could easily be connected to
assassination attempts. In 11 c.e. Augustus made it illegal to
make a prediction about anyone’s death. Astrology was also
seen as in origin a foreign expertise, connected to Greece,
Egypt, and Babylonia. Astrologers were usually called Chal-
deans, which was the name of the Babylonian order of priests
who watched the sky for omens. Both astrology and magic
were at times banned in Rome.
Nonetheless, astrology rapidly became extremely popu-
lar in Roman society. In his poems the Roman satirist Juvenal
(ca. 55–ca. 127 c.e.) mocks many of its adherents, especially
women and the lower classes. Most astrologers were not, in
fact, astronomers. By the early second century c.e., however,
there was suffi cient data to compose planetary tables in which
the relevant information could simply be read off for any year
and time.
Astronomy and astrology had a close relationship. As-
tronomy remained a demanding and specialized form of
mathematics. Astrology, on the other hand, was widespread
and practiced both by professionals and by individuals who
wanted to predict their own future. Astrology was, however,
ultimately dependent on astronomy and using astronomy’s
reputation for precise mathematical certainty for its own ad-
vantage. Astronomy, meanwhile, could explain its relevance
to human life through the predictions of astrology.
SCIENCE IN THE LATE EMPIRE
Th e late empire included many notable mathematicians, such
as Pappus of Alexandria, Th eon of Alexandria, and Eutocius,
as well as medical writers, such as Oribasius and Paul of Ae-
science: Rome 945
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