"Wolfgang" wrote in
:

Actually, the story isn't quite that simple. The flat versus
spherical debate (not to mention infinite variations) raged for a long
time. It certainly IS true that most educated people knew a long time
ago that the question had been settled, but it was by no means a dead
issue as late as the mid-15th century......any more than evolution
versus intelligent design is today. Washington Irving may have
popularized the myth about Columbus, but many of the sailors aboard
his vessels undoubtedly had serious concerns about this spherical
Earth "theory."

Incidentally, while Columbus was obviously right about the shape of
the Earth, he was WAY wrong about its size (thus leading him to
believe that he'd arrived at the East Indies).......which had been
pretty accurately estimated by a number of folks centuries earlier.

Wolfgang


"Settled" might be an overstatement-- after all, we still have flat
earthers today. There do seem to be some historians that hold that the
flat earth theorists were influential at the later Middle Ages, but most
historians seem to agree that based upon a relative scarcity of traceable
reference to a flat earth after about 800AD, the influence was marginal.

As for Columbus, if he did in fact use a flat vs spherical Earth
hypothesis to bilk Spain out of funds, it certainly wouldn't be the last
time a scientist set up to disprove a straw horse to secure funding (but
it might have been the first!)

Size was a different matter. I think that the Late Middle Age "natural
philosophers" had a fair problem understanding scale, and the fact that
people didn't understand that the distance of stars was so vast as to
preclude parallax errors was responsible for geocentrism holding on as
long as it did.

This isn't what gave Columbus problems, though. Indeed, his estimation
of how far he travelled is remarkably accurate given his dead reckoning
preference (see http://www.columbusnavigation.com/v1a.shtml). The
problem was that he used Ptolemy's huge underestimation of circumference.
Almost 500 years before Ptolemy, Eratosthenes had an estimation of
circumference to within 8%.

While he preferred dead reckoning, Columbus also had a quadrant on board.
I would think that a well developed technique for quadrant based
navigation at Columbus' time would indicate a well developed sense of a
spherical earth.
--
Scott
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