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mate the planet’s circumference
within 1,000 miles.
Combining the work of
earlier Greek scholars with
travelers’ stories and town
records from across the then-
Roman world, Greek-Egyptian
astronomer Ptolemy compiled
Geographia, an eight-volume
atlas that formed the basis for
the next 1,500 years of map-making. Completed around
150 A.D., Geographia served
as a how-to manual for cartog-
raphy. Ptolemy explained map
projections—depicting a globe
on a f lat plane. And he listed
the coordinates for 8,000 loca-
tions in the recorded world—at
the time, Eurasia and northern
Africa—based on parallels of
latitude and meridians of lon-gitude, a precursor to today’s
system.
Maps based on Ptolemy’s
blueprint for the shape and size
of the world informed Colum-
bus’s voyage to the Americas and
led Ferdinand Magellan’s expe-
dition around the globe. Yet his
work disappeared with the fall of
the Roman Empire, not reemerg-
ing for almost 800 years.▲No original maps from Geographia
survived, but this, the oldest recreation,
was constructed in the 14th century
according to Ptolemy’s map projection
and locations.