Re: rotation of the earth

Glenn Morton (
Sat, 13 Dec 1997 20:03:29 -0600

Hi George,

At 08:32 PM 12/13/97 -0500, George Murphy wrote:

> Thank you for these citations. I do not want to seem like the
>monks who refused to look through Galileo's telescope, but I am still
>quite puzzled by this. The primary problem is just that I have never
>heard of this having had any influence on the debates about the
>Ptolemaic & Copernican theories in the 16th & 17th century, as
>Manchester's account suggests that they did.

Now here I agree with you. Ever since my discussion with Ted I stop by the
history section of my favorite book stores and look in the indexes for
I am looking for someone else to support or refute Manchester. So far I
haven't come up with anything. Sometimes it takes years to find a given fact
I am looking for so I am quite patient. One story I was wanting to verify
(on another topic) took about 15 years before I found the documentation.

What I have found in the bookstores is that for the most part Magellan is
ignored. I know this, the crew were truly puzzled by the dates.

>> > It seems to me you've made things more complicated than
>> >necessary by introducing 4 motions. The essence of the problem can be
>> >seen just with the rotation of the "fixed stars" and the motion of the
>> >sun around the earth in an approximately circular orbit. The epicycles
>> >& deferent are unneeded refinements for this purpose.
>> If one is going to see if the voyage of Magellan had any implication for
>> Ptolemy, one must use the system that Ptolemy and the Medievals used. Their
>> system was a whole bunch of complicated cycles and epicycles etc. Mercury
>> rotated around an epicycle, which in turn rotated around a center which also
>> rotated around its own circle. I would refer you to A.C. Crombie, "Medieval
>> and Early Modern Science, Vo. 2, (new York: Doubleday, 1959) p. 171
> I'm quite aware of the complexity of the Ptolemaic system - &
>also of the fact that all the epicycles &c weren't removed by
>Copernicus. But while the general idea of geocentricity was essential
>to the Ptolemaic-Aristotelian world view of the Middle Ages, the precise
>system of epicycles &c wasn't _de fide_, & as I understand it, there was
>some freedom for astronomers to play with these details.

Within limits you are correct. A.C. Crombie Medieval and Early Modern
Science Vol 2, p. 169. Interestingly the same page says that in the
Ptolemaic system "the constants of epicycle and deferent were reversed
between the lower planets (mercury and Venus) and the upper ones; and the
sun's period of revolution appeared in the calculations for each of the five
planets." p. 169

I would say that the situation was even more complicated than I made it out
to be in my post.

It seems to me
>at the very least that an intelligent geocentrist would have said,
>"Well, I can't see how to get the details to work out, but the basic
>"loss of a day" shouldn't be a problem" - using the type of argument I

We have geocentrists today who say the same thing. We also have lots of
Christians saying "We don't know how to deal with pseudogenes but it
shouldn't be a problem. But that type of response is not one to the data.


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