of the fl at ends, surrounded by a thick mist that obscured the
spheres of fi re that enclosed the mist. People could glimpse
the enclosing fi re through pinpoint holes in the mist, holes
that were perceived as the sun, moon, and stars.
Astronomical observations of the movement of the stars
and their relationship to seasons were much older, because
they were crucial to a largely agricultural society. Offi cial cal-
endars followed the phases of the moon, but over many years
such calendars become out of phase with the solar year, until
an event originally placed in the spring took place when the
leaves were falling.
In the fi ft h century b.c.e. Meton, probably working
partly from Babylonian written observations of the move-
ments of the heavens (going back much further than those
of the Greeks), worked out a 19-year lunisolar calendar that
would have kept the moon and the sun in step over a 19-year
period to a precise degree of accuracy. Th e Athenian state did
not adopt this as the offi cial calendar. Th e results of specialist
intellectual inquiry were not always viewed as socially useful
or as an improvement on tradition.
In astronomy itself, however, observations were becom-
ing fuller and more detailed, including Callippus’s work
(fourth century b.c.e.) on the exact dates of the summer and
winter solstices and the realization that the year’s four seasons
are not of equal length. Th ese observations were incorporated
into attempts to produce models of the cosmos that would ac-
count for such phenomena as the movements of the sun, the
lunar cycle, and the movements of the so-called wandering
stars—the planets. (Planet is Greek for “wanderer.”)
Th e traditional story is that Plato challenged astrono-
mers and mathematicians to come up with such a model and
that in response Eudoxus developed his theory of concentric
spheres. In this theory the sun, moon, and fi ve planets are
fi xed to 27 spheres around the common center of the station-
ary earth, and these spheres revolve on diff erent axes of ro-
tation and at diff erent speeds. Th e theory was elaborated by
Callippus, mechanized by Aristotle (by which time it had 76
spheres), and eventually abandoned in the second century
b.c.e. when the mathematician-astronomers Apollonius of
Perga and Hipparchus invented models of epicyclic and ec-
centric rotation. Th eir model was further refi ned into the
Ptolemaic universe worked out by the astronomer Claudius
Ptolemaeus (Ptolemy) in the second century c.e., a system
that survived until Copernicus.
Th e aim of all such models seems at least partly to have
been “to save the phenomena”—that is, to discover a working
mathematical model of the heavens that allowed observations
to be accepted and not explained away as optical illusions or
untrue in some other way. Some of these models may have
been largely exercises in mathematical ingenuity, but many
astronomers were certainly interested in trying to discover
how the universe actually worked. In the third century b.c.e.
Aristarchus of Samos proposed a heliocentric cosmos, but
only one person supported the idea, and later astronomers
such as Claudius Ptolemaeus attacked it on the grounds thatit was not supported by observation or by current (Aristote-
lian) theories of physics.
Astronomy was an enterprise that required consider-
able mathematical knowledge, beyond that even of most
philosophers, although most people probably had a very
basic form of astronomical knowledge. Specialized and dif-
fi cult though mathematics was, it did have practical applica-
tions in the everyday world in meteorology, geography, and
especially astrology.METEOROLOGY
Th e Greeks traditionally associated changes in the weather
with changes in the sky. Storms, for example, were more fre-
quent around the time of the equinoxes. Th e sun, moon, stars,
and planets were thought to be much closer to the earth than
they actually are, and so their movements were thought to
aff ect the air around the earth and thus the weather. As as-
tronomy’s observations and models became increasingly de-
tailed and precise, predictions of the weather also grew much
more elaborate. In the third century b.c.e. the poet Aratus of
Soli recast a famous astronomical book by Eudoxus about the
movements of the stars and related weather patterns into po-
etry. It was extremely popular among the literate population
of the ancient Greek and Roman world.GEOGRAPHY
Th e early Greeks believed that the lands around the Medi-
terranean Sea were surrounded by a huge ocean. Going far
enough east, west, north, or south would take a person to the
edge of the world. Slowly, traders and other travelers brought
back information about foreign lands, and the world the
Greeks knew about got bigger.
By the fourth century b.c.e. many intellectuals had real-
ized the world must be a sphere. Aristotle pointed out that
someone watching a ship sailing away sees the front end of
it disappear fi rst. In the third century b.c.e. Eratosthenes
calculated the circumference of the earth, possibly to within
about 311 miles. (Th e exact length of the unit of measurement
he used is not known.) Although only a few experts and, to
a smaller extent, educated laymen, traders, and the military
needed to know much about astronomical geography, those
who did were slowly building up a three-dimensional picture
of the Northern Hemisphere.ASTROLOGY
Before the Greeks, Babylonian priests watched the sky for
omens, and their long-term observations provided vital as-
tronomical data for the Greeks. Th e data enabled astrono-
mers to predict the future movements of the stars based on
past patterns. Although the details are unclear, sometime be-
tween the third and fi rst centuries b.c.e. this ability to predict
movements developed among the Greek population of Egypt
into an astrological system, a synthesis of Greek thought with
Babylonian omen-based astronomy and some small Egyptian
infl uence. An important part of this astrological system wasscience: Greece 9390895-1194_Soc&Culturev4(s-z).i939 939 10/10/07 2:30:30 PM