Geography Reference
In-Depth Information
canceled each other out, this calculation was an extraordinary example of the Greek ability to apply logic
and mathematics to measuring—and knowing—the world.
After Eratosthenes died, a conflicting view of the size of the earth came from another Greek historian-
geographer named Posidonius (circa 135-51
BC
) of Rhodes. His calculation was based upon the height of
the star Canopus, determined algebraically, and used the sailing time of ships. Ironically, his calculations
were close to the figure Eratosthenes had reached. But for some reason they were later reduced to the much
smaller size of 18,000 miles by Strabo, another significant scholar who comes along next. It was this figure
that Columbus would rely upon in making his case for a voyage west to the Orient.
While this mistake—a smaller earth—was widely accepted and perpetuated, another of the conclusions
reached by Posidonius was correct, but dismissed because it contradicted Aristotle. Posidonius believed
that the equatorial zone was quite habitable and that the highest temperatures were to be found in deserts
inside the so-called temperate zone, which is the case.
The expert who inaccurately recorded Posidonius was the second key “Greek” geographer, Strabo
(circa 64
BC-
circa
AD
20), who was born in what is now modern Turkey and who wrote at about the time
of Christ. Like Eratosthenes, Strabo worked in the Alexandria library. Unlike Eratosthenes, Strabo was no
innovative genius who came up with new theories about the world. His genius, instead, was as a compiler
and his work,
Geographica
, filling all of seventeen volumes, brought together the sum of the Mediter-
ranean world's knowledge to that time, describing Asia, North Africa, and much of Europe, which Strabo
had seen himself in his extensive travels. Among his chief contributions was his division of the world into
frigid, temperate, and tropic zones, although he badly miscalculated how far north and south of the equator
these lands were habitable. He believed, like Aristotle, that the dark skin of the Ethiopians was the result
of scorching by the sun and that the blond barbarians of the north were savage because of the frigidity of
the arctic zones.
And finally, there was Ptolemy (circa
AD
100-170), an Egyptian-Greek or Greek-Egyptian (but not one
of the royal Ptolemies) who condensed the sum of Greek world knowledge during the period of the Roman
Empire and whose views were accepted for centuries.
Although best known for his work in the area of astronomy—kept alive by the Arabs and known by its
Arabic name,
almagest
—Ptolemy's
Geographia
laid out many of the principles still followed in modern
cartography and included an atlas of the known world, based on the reports of the Roman legions as they
spread the Roman Empire. It included some eight thousand places identified by their latitude and longit-
ude—words Ptolemy is said to have coined. And the system he adopted is basically that of modern geo-
graphy, including the seemingly simple notion of orienting maps with the north at the top and the east on
the right. That is, it seems simple enough until you realize that if you set out to orient a map today, what
would you place at the top? Given the notion that the world is a sphere, any arbitrary spot might have been
used. For many centuries, for instance, European maps were oriented with east on top, emphasizing the
centrality of the Holy Lands, and Jerusalem in particular.
Ptolemy also attempted to address a problem that still exists: the impossibility of representing a round
earth on a flat piece of paper. His solution was a globe, but that posed its own problems, as a globe could
not be made large enough to encompass the fine details that Ptolemy wanted to include in his maps.
Ptolemy's world was surprisingly large, consisting of the three continents then known to the people
around the Mediterranean—Europe, Asia, and Africa. Although often inaccurate in matters of size, shape,
and precise location, it included the British Isles, Scandia (Scandinavia), and Sinae (China). He also de-
scribed the source of the Nile quite accurately as lakes in Africa south of the equator—hidden in the
“Mountains of the Moon”—a fact left unproven to the European world until the travels of the British ex-
plorers Sir Richard Francis Burton and John Speke in the nineteenth century.
