Encyclopedia of Society and Culture in the Ancient World

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-

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