Scott Seidman wrote:
"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.

Settled. Note that I said "educated people." Yeah, we have flat
earthers.....and we have creationists.....and we have intelligent
designers.....and we have dicklets and kennies and stevies.

There do seem to be some historians that hold that the
flat earth theorists were influential at the later Middle Ages,

It doesn't just seem so. It is so.

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.

The Church has not yet been marginalized. Would that it were so.

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!)

It would most certainly not have been the first.....not by a long shot.
However, it doesn't seem likely that he did. I mean, why would he so
much as hint at a discredited theory that predicted the certain failure
of the enterprise he was trying to bankroll?

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.

Well, all of that is, again, only partly true. Aristarchus of Samos
proposed a heliocentric model of the solar system as early as the third
century BCE. Hipparchus, a century or so later, came up with a good
estimate of the circumference of the Earth.....and the moon.....and the
distance between them, relying heavily on information gleaned from
eclipses, both solar and lunar. The ancient Greeks (as well as the
later Arabs) were well aware of the implications of the terminator on
the lunar surface. And, once again with the help of eclipses, they
were able to extrapolate from those implications and deduce the shape
of the Earth.* Astronomers and other natural philosophers in the late
middle ages had varying access to a lot of this information and equally
diverse opinions as to its validity and utility. Most of their
problems stemmed from, or were at least greatly exacerbated by,
official Church doctrine. Some things never change, it would appear.

This isn't what gave Columbus problems, though.

True. But then, I didn't suggest that it was.

Indeed, his estimation
of how far he travelled is remarkably accurate given his dead reckoning
preference (see http://www.columbusnavigation.com/v1a.shtml).

Stipulated. I don't need to follow the link.

The
problem was that he used Ptolemy's huge underestimation of circumference.

Yeah, that's what I said, he was wrong about the size of the Earth.

Almost 500 years before Ptolemy, Eratosthenes had an estimation of
circumference to within 8%.

O.k., you've got me there.....I didn't mention Eratosthenes
specifically.

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.

Yep. But then, I didn't suggest that Columbus was wrong about the
shape of the Earth. Quite the contrary, as a matter of fact.

Wolfgang
*and then there's the chinese, the mayans, the druids......and just
about everybody else who figured it out a long long time ago.