What I find plausible in the stories is mainly this: that the sailors who
landed in the Cape Verde Islands at the end of their circumnaviation found a
discrpancy about what date it was, differing by one day with the locals.
This would not only be correct scientifically, but seems correct
historically also. I can find no reason to doubt the accounts, which
apparently cite primary sources to this effect.
What I cannot accept, however, is mythological claims such as the following,
which Glenn quotes at length:
"During the Dark Ages literal interpretation of the Bible
had led the Church to endorse the absurd geographical dicta of
Topographia Christiana, a treatise by the sixth-century monk
Cosmas. Cosmas, who had traveled to India and should have known
better, held that the world was a flat, rectangular plane,
surmounted by the sky, above which was heaven. Jerusalem was at
the center of the rectangle, and nearby lay the Garden of Eden,
irrigated by the four Rivers of Paradise. The sun, much smaller
than the earth, revolved around a conical mountain to the north.
The monk's arguments were fragile, and not everyone accepted them
- the Venerable Bede, among others insisted that the earth was
round - but Cosmas scorned them. Rome agreeing with him,
rejected their protests as an affront to common sense.
"This patristic dismissal of so elementary a fact was a sign
of how deeply the wisdom of the ancient world had been buried.
More than three hundred years before the birth of Christ,
Aristotle had determined that the planet must be a sphere; after
an eclipse he pointed out that only an orb could throw a circular
shadow on the moon. The existence of India and Spain was known
in Athens. "
~William Manchester, A World Lit
Only By Fire: The Medieval Mind and the Renaissance: Portrait of
an Age, (Boston: Little, Brown & Co., 1992), p. 230
It's this kind of BS (that's the only term I can think of that accuractly
conveys my meaning, please forgive) that gets my hackles up. Cosmas was one
of only two persons we can name in the Latin West, after the time of Christ,
who believed in a flat earth; from this isolated fact, Manchester follows a
long, illustrious, and unsupportable tradition into mythmaking, by making
Cosmas the symbol of a collection of patristic writers who said nothing of
the sort. Manchester is a prize-winning historian, but not when he writes
about the "Dark Ages" -- a term that no contemporary scholar of that period
uses, to the best of my knowledge, because it conveys precisely the kind of
erroneous notions that Manchester should have known better than to believe.
Myths like the "flat earth" and the "warfare of Christianity and science,"
which incidentally are closely linked, are awfully easy to spot in
historical writing. Ask a couple of questions: (1) is "reason" being used
to show how "utterly foolish" Christians were? (2) can you hear the
orchestra coming to a crescendo as the hero steps into the center of the
stage and stands up for "truth"? If the answer to both questions is "yes,"
there is an awfully good probability that you're reading BS that passes for
historical scholarship. Not always, but very often. Get your antennae up.
PS. Glenn might be on to something about Magellan and Ptolemy, in terms of
the technical details and what his voyage was LATER understood to have
accomplished. I don't know, but he might be. I suggest that he write up
what he finds and send it to Owen Gingerich, or to the Journal for the
History of Astronomy, in which case Owen will eventually see it anyway. It
sounds plausible, at any rate. However, it is worth noting that Magellan's
voyage can't possibly have been taken for "proof" of Copernicanism at the
time. Although Copernicus' ideas were circulating informally from c. 1512,
his book wasn't printed until 1543, and we know of fewer than a dozen people
in the whole world who believed him concerning the earth's motion prior to
the time Galileo used a telescope to see a bunch of hitherto unknown things,
in 1609-10. None of those Copernicans, to the best of my knowledge, ever
linked Copernicanism with Magellan. Once again, we might have the makings
of a myth here.