Page 60 - BBC History The Story of Science & Technology - 2017 UK

Heaven & Earth / Ptolemy

This engraved allegory of
astronomy, taken from Margarita
Philosophica (1508), shows a
crowned Ptolemy being guided
by the muse Astronomy

harder to construct a map on this projection, and diagrams that allowed later map-makers Looking at a world map based on
as the curved meridians could not be drawn to adapt it. Perhaps we should therefore regard Ptolemy’s calculations, it is no wonder
with the aid of a swinging ruler. Ptolemy as the first digital geographer. that Columbus and Magellan believed it
However, Ptolemy cheerfully advised When Columbus and Magellan planned was possible to sail west to get to the east.
readers to “hold on to descriptions of both their epic voyages to the east by sailing west, Without Ptolemy’s mistaken calculations,
methods, for the sake of those who will be they both turned to Ptolemy to support they would probably have never set off on
attracted to the handier one of them because their expeditions, and for good reason. such daunting voyages, and the shape of
it is easy”. He was, in effect, offering Ignoring Eratosthenes’s calculations, the age of discovery might have looked
subsequent generations a mapping tool kit Ptolemy had estimated the length of very different.
and a gazetteer of places to which they could a degree as 500 stades, underestimating
expand almost indefinitely, building up an the global circumference by as much as Jerry Brotton is professor of Renaissance studies
ever-changing map of the world as new data 10,000km, or more than 18 per cent of the at Queen Mary University of London. He is the
became available. Earth’s actual circumference. author of This Orient Isle: Elizabethan England
and the Islamic World (Penguin, 2016)
Mapping the future He preferred the
But there was also another astonishing
reason for the success of Ptolemy’s projec- consistency of DISCOVER MORE
tions. The earliest surviving manuscripts BOOKS
of the Geography with maps come from late mathematics over The History of Cartography, vol. 1
12th-century Byzantium. There is no concrete eds JB Harley and David Woodward
evidence that Ptolemy ever drew his own the unreliable gossip (Chicago, 1987)
maps. Instead, he transmitted geographical A History of the World in Twelve Maps
data in digital form, using a series of numbers of travellers’ tales by Jerry Brotton (Penguin, 2013) GETTY

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