Eratosthenes, the Philosopher
In ancient times, there was no clear-cut distinction between mathematicians,
astronomers, scientists, political theorists, or anyone else who discovered
things or came up with original ideas. We call all of them "philosophers."
The total amount of available knowledge at that time was so little that one
person could become an expert in all fields of knowledge in the space of his
lifetime. (Compare that to nowadays, where to read all publications in just
one field, mathematics, would require 18 hours every day just to stay even.)
Eratosthenes was born in Cyrene on the coast of North Africa, in what is now
called Libya, in 376 BC. He lived mostly in Alexandria during the
Ptolmaic Dynasty, when Egypt was ruled by the descendants of Ptolemy Soter,
one of Alexander the Great's generals.
Eratosthenes was an expert in mathematics and astronomy, to name just two
fields. He was also a philosopher of the Stoic school.
In astronomy, one of the most important accomplishments of Eratosthenes
was his
measurement of the circumference of the Earth. Had Christopher
Columbus been aware that Eratosthenes was right, he would never have tried
to sail to India, since it was too far from Spain to reach with his ships.
Instead, Columbus believed the erroneous value, perhaps that of
Posidonius, who gave a much smaller size for the Earth, putting Asia just
West of Europe, within reach of Spain.
Forget all the misconceptions from children's stories about Columbus, about
him proving the Earth was round.
No educated person in Columbus' time believed the Earth was flat, and the
Monarchs of Europe who refused to fund Columbus for 20 years were right to
believe that he could never reach Asia by sailing West, as
their advisors were fully aware of Eratosthenes.
Only when Queen Isabella suddenly changed her mind did he get funding.
Columbus never admitted that he had not reached Asia, but after his death
it became obvious that an entire New World had been discovered, validating
Eratosthenes' calculation.