Re: rotation of the earth

Glenn Morton (
Mon, 15 Dec 1997 19:18:30 -0600

At 01:31 PM 12/15/97 -0700, Don N Page wrote:
> I see that I opened a whole can of worms by questioning Glenn Morton's
>old posting. I certainly don't mean to rap anyone's knuckles with this, and I
>am not trying to prove which among us current ASA discussants is or is not
>correct about it,

I for one am NOT afraid of being proven wrong. In fact I wish someone could
tell me FROM THE DETAILS of the Ptolemaic system that I am full of it. I
simply want to know the truth. I use this example in my first book, and if
it is wrong, then I will remove it or put an errata in on it. I do not want
to teach anything that I know to be untrue. We all believe some untrue
things, but we have an obligation to do our best to check things out and
change them when proven wrong. But I WANT to understand why I am wrong if
that turns out to be the case. This is my interest so I hope that below this
point in your note, you can prove me right or wrong.

>but I see from all the response that it raises interesting
>questions of what people in the past did or did not believe, and whether or
>they had rational justifications for their beliefs. Glenn has brought out a
>very interesting historical point, that William Manchester claimed that
>Magellan's voyage discredited geocentrism. I'll be interested to hear from
>historians as to whether the voyage really had the historical effect of
>people to give up geocentrism, but I would claim that the "missing day" should
>not have, by itself, been any rational argument at all against geocentrism.
I agree that simply the missing day would not do it. But in the Ptolemaic
system after you forced me back into it, there are relative motions between
the planetary spheres and stellar sphere. And until Manchester's claim I had
never heard that Magellan had any effect on astronomy. But as Ted points
out, Manchester was an award winning historian, although this was not the
work which won an award. :-)

> Thus with a round earth, Ptolemy's system would have given the
>same "missing day" for the voyagers as a system in which the earth is taken to
>be rotating and/or revolving around the sun. In other words, the complication
>of Ptolemy's system that Glenn alludes to is irrelevant to the explanation of
>the "missing day."

You have missed the fact that it is not just a missing day but an added
rotation to the planetary spheres. Both of these effects occurred not just
one. Or am I missing something? Is the relative change between the stellar
and all other spheres spheres as Magellan traveled do damage to the
perceived causality of the system? All planetary spheres have relatively
slower westward rotation than the stellar sphere.

> I suppose it might be interesting for someone with an historical bent
>(Glenn Morton and/or Ted Davis?), if he/she/they agree(s) with my analysis
and >find(s) that Manchester had no historical justification for his
statements, to
>write a rebuttal to Manchester's account, but maybe this is just a drop in the
>bucket of Manchester's sillinesses about the "Dark Ages" if Ted is right.
I wish that Manchester had documented his page better. I agree with Ted and
George and you that Magellan's voyage does not play much of a historical
role that I have ever heard in the argument about heliocentricity.

The only complaint I have about your reply is that like George, you reduced
the problem to one of ONLY a missing day. There was also an equal but
opposite discrepancy between the ship and the planetary sphere which upsets
the ratios of epicycles to eccentrics. I am going to see if I can find
Manchester's e-mail address.


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