Global Positioning System Reference
In-Depth Information
by early medieval times in Europe. Why the change in view? Observational
science came to influence Greek philosophers, and the evidence for a
spherical earth was right before their eyes. Pythagoras preferred a spherical
earth anyway, on aesthetic grounds (typical for him). Aristotle, who lived
two centuries after Pythagoras, placed greater value on evidence, and from
these observations he too considered the earth to be a sphere. Strabo, a
Greek geographer writing at the turn of the common era, deduced a spheri-
cal globe on the basis of what he saw closer to the surface. He noted that
lights in elevated lighthouses could be seen from farther out to sea than
lights at sea level. Masts of ships disappeared from view after the ship's
hull. Such maritime observations—which applied to observers looking
in all directions—strongly suggest a curved earth. Eratosthenes, another
Greek and a confirmed scientist, not only believed that the earth was a
sphere but also measured its radius—for which he, and a couple of other
like-minded philosophers, deserve a separate section in this topic.
The crew of Christopher Columbus may well have been close to mutiny.
The crews of many sailing ships that explored the world at earlier and later
FIGURE 2.1.
A fifteenth-
century depiction of the earth
as a globe. This illustration,
from a book by John Gower
(written ca. 1400 CE and now
in Glasgow University Li-
brary), shows him shooting
at the world: ''I throw my
darts and shoot my arrows at
the world. But where there is
a righteous man, no arrow
strikes. But I wound those
who live wickedly.''
