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Heaven & Earth / Ptolemy

A
sk any geographer
to name one individual
responsible for founding
their discipline and they
are likely to answer:
“Ptolemy.” Claudius
Ptolemaeus (c100–
c170 AD) lived in second-century
Alexandria, where he wrote the Geographike
Hyphegesis (c150 AD), known today simply
as the Geography. It defined geography,
explained how to draw a world map and
offered a gazetteer of over 8,000 locations
in the known world.
For the next 1,500 years, virtually every
map-maker accepted Ptolemy’s Geography
as the authority on the shape and size of the
world. Columbus and Magellan both used
Ptolemy to embark on their voyages of
discovery, and even 16th-century map-
makers like Gerard Mercator and Abraham
Ortelius, who knew that Ptolemy’s geographi-
cal knowledge was limited, drew maps in
homage to the man they regarded as ‘the
father of modern geography’.
The basic principles of Ptolemy’s map
projections remain in use to this day – even
Google’s ‘Earth’ application uses a projection
first invented by him – and yet his life, as well
as his methods, remain a mystery. What little
we know is based on later Byzantine sources.
He was a native of Ptolemaic Egypt, which,
during his lifetime, was already under the
control of the Roman empire. Taking the
name ‘Ptolemaeus’ suggests he had Greek
ancestors and ‘Claudius’ indicates he
possessed Roman citizenship.

Circuits of the Earth
What is known is that Ptolemy worked at the
A 15th-century
Alexandria Library, founded in c300 BC, the
map of the ‘world’
repository of all written knowledge, which
based on Ptolemy’s treatise
held thousands of manuscripts from across on cartography, The Geography
the Greco-Roman world. Some of the (c150 AD). The pioneering
greatest classical scholars worked there, map-maker was regarded as the
authority on the shape and size
including the mathematicians Euclid
of the Earth for 1,500 years
(c325–265 BC) and Archimedes (c287–212
BC), the poet Callimachus (c310–240 BC)
and the astronomer – and one of the earliest a physical medium, such as wood, stone or Earth encircled by water in his Odyssey, but
librarians at Alexandria – Eratosthenes bronze, called pinax – for centuries, and by the fifth century BC Pythagoras and
(c275–194 BC). By Ptolemy’s time, the writing about them in works usually entitled Parmenides concluded that if the universe
library, like the Hellenic culture it repre- Periodos Ges (literally a ‘circuit of the was spherical, then so was the Earth.
sented, was in decline, ravaged by warfare, Earth’). Homer describes a circular, flat In Phaedo (c380 BC), Plato described the
neglect and looting. For Ptolemy this decline Earth as “round and in the centre of the
represented a unique opportunity to heavens”, “marvellous for its beauty” and
summarise nearly a millennia of Greek Ptolemy drew circular perfection. Aristotle agreed, adding
geography. By drawing on what remained a geometrical net climatic zones, which led his disciples to
of the library’s resources, Ptolemy compiled introduce rudimentary lines of latitude and
his Geography, to “show the known world of latitude and longitude. Using astronomy and geometry,
as a single and continuous entity” and to they pieced together a map of the known
“investigate the Earth’s shape, size, and longitude over world which they called the ecumene – an
position with respect to its surroundings”. inhabited ‘dwelling space’. Although none
The Greeks had been drawing maps – onto the world of these maps survive, a reconstruction of GETTY

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