Re: A rotating Earth?

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

The size of the universe was not a factor in the geocentric models,
except of course that any change from perfect circular motion (in the
most general sense) had to occur inside the lunar orbit.
One arguement against the earth's rotation was that if the earth were
rotating, then a stone dropped would appear to fly off horizontally as
the earth rotated below it.  That was not observed, hence the earth must
not be rotating.
This arguement places new significance on the thinking that led to what
we not call Newton's first law...things move at constant velocity unless
they don't.

cheers

On Thu, 3 Feb 2000, John Mallinckrodt wrote:

> On Thu, 3 Feb 2000, Leigh Palmer wrote:
>
> > The crucial question is whether Brahe considered the Earth to rotate.
>
> Precisely.  I fear that my question may have been misinterpreted by some.
> Of course, as Joe and Dan pointed out (and as I should have known), Kuhn
> is the obvious reference.  Unfortunately, I too am at home and away from
> my copy of the book.  Nevertheless, I do have a good library down the road
> and they were willing to loan me a copy.
>
> It appears from Kuhn that resistance to Earthly motion of *any* kind
> played a bigger role than I had previously understood.  Indeed, not only
> was rotation opposed on the grounds that we could not fail to notice its
> effects, but also simply by appeal to the absurdity of the notion that
> something as massive and substantial as Earth could possibly make a full
> rotation in just 24 hours.  (Note that it was perfectly acceptable for the
> rest of the entire universe to do so.  This, I assume, because heavenly
> bodies were ethereal and subject to different rules than terrestrial
> matter.  It is interesting, however, in this regard that the universe was
> considered finite largely as a result of the fact that it must rotate.
> Only after the Copernican revolution managed to stop the stars was an
> infinite universe considered a reasonable hypothesis.
>
> Kuhn also answers my question about Brahe and makes it clear that Brahe's
> Earth did *not* rotate since his primary motivation was to account for his
> observations while preventing Earthly motion of any kind.  Brahe was
> evidently a most committed anti-Copernican as were most folks for at least
> a half century after Copernicus' death.  Feature of Brahe's model is a bit
> of a revelation to me. I have always pictured it as featuring a leisurely
> yearly revolution of the Sun around Earth with the planets making somewhat
> more or less leisurely revolutions about the Sun; I hadn't really ever
> thought to wonder about diurnal motion in Brahe's model.  In fact, that
> leisurely yearly motion was only a minor perturbation of what was
> primarily a frenetic daily revolution of the whole structure about Earth.
> I suppose that really isn't so surprising given that that frenetic motion
> had been well accepted for a very long time but, somehow, it just seems
> out of place in Brahe's transitional scheme.
>
> John Mallinckrodt      mailto:ajm@csupomona.edu
> Cal Poly Pomona          http://www.csupomona.edu/~ajm