1.1 Eratosthenes Measures the Earth (6 pages)
position of stars at night could also be determined by an observer sighting through the ring
from inside the bowl.
Eratosthenes’ measurement reflects his interest in both mathematics and geographry. He
wrote a work on geography in three books which was apparently widely consulted in the
ancient world. (For example Julius Ceaser mentions in his Gallic Wars that Eratosthenes
knew of the Hercynian Forest in Germany.) Surely Eratosthenes’ measurement of the
earth was a fundamental bit of information in this work.
He introduced the partition of the globe into the artic (frigid), temperate, and tropical
(torrid) zones that we still use. His work included the first map of the known world on a
sphere giving locations relative to fixed lines on the globe, although the idea of a coordiante
system based on lattitude and longitude would have to wait for Ptolemy. Yet, it was the
first attempt at a scientific map.
The complete work is lost. But fragments are preserved in quotations from Strabo
BCE - 21 CE) often intermingled with quotations from Hipparchus. Hipparchus is our