Mapmaking - The Science of Navigation - page 89

comes heavily influenced by external factors, such as religious orthodoxy
and the development of printing. But the beginnings are simple and clear. 1
Let us start with Herodotus in the fifth century BCE. An outstanding
historian, Herodotus speculated about the geography of the lands he wrote
about. In particular, he knew of the Nile and its annual flooding and
wrongly speculated that this must be due to snow melting in mountains
very far to the south. Here is an early example of a myth that was per-
petuated for millennia; well into the late nineteenth century, European
explorers were seeking the source of the Nile too far south. Eratosthenes,
whom we met earlier measuring the radius of the earth, proposed a grid
system for drawing maps. This idea was improved upon by Hipparchus of
Rhodes. In the second century BCE he proposed a reference grid that was
based upon astronomical factors, so that, for example, cities on the same
line should have the same number of daylight hours during their longest
day of the year. Hipparchus is thus credited with giving us the idea of
latitude and longitude. He also was the first to write about the precession of
the equinoxes.
The contribution of Hipparchus was recognized by a figure who is uni-
versally known as the father of geography: Claudius Ptolemy, the o≈cial
astronomer and geographer of Alexandria. Ptolemy wrote the hugely in-
fluential eight-volume Guide to Geography , which included a map of the
known world (fig. 4.1) with the latitude and longitude coordinates of 8,000
major places. Ptolemy's method was scientific in that he intentionally
included enough written information so that others could reconstruct his
map, were it to be lost. He established the convention of orienting maps
so that north appears at the top. Unfortunately, he also held a number
of wrong-headed views that would dog Western opinions for over 1,300
years—such was his authority. Ptolemy believed that the earth was the
center of the solar system, that the radius of the earth was some 40%
smaller than it really is (based upon a misunderstanding of Posidonius's
estimate, as we saw in chapter 2), that Asia spread across 180\ east to west
(it covers 130\), and that Africa was connected to a so-far-undiscovered
great southern continent and so could not be circumnavigated. 2
1. Early maps and mapmaking are well represented in the literature. Much of this sec-
tion comes from Balchin (2004), Berggren and Jones (2000), Boorstin (1983), Campbell
(1981), Edson (2007), Harley (1989), Harley and Woodward (1987), and Wilford (2000).
2. Captain Cook was sent to look for this great southern continent. He didn't find it and
convinced most people that it did not exist. Consequently, he was the last of a long list of
maritime explorers who chased after Ptolemy's will-o'-the-wisp.