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I would like to add few remarks to this discussion
(and to defend the "ancient Greeks":-)

Lu wrote:

> >>Given the level of scientific knowledge, inquiry, and downright genius
> >>among the ancient Greeks, I'm rather surprised that the idea of a
> >>heliocentric universe didn't occur to one of them.

and Bill replied:

> > It did indeed occur to one or more of them, Aristarchus of Samos.

1. There are apparently hudge gaps in our knowledge
about "ancient Greek's" science. There are indicatrions that
the heliocentric system (and possibly the law of universal gravity)
were common knowledge among educated "Greeks" in 3-1 cent BC.
The problem is that very little of scientific writings
of that time survived.

At the time when Ptolemy wrote, this "ancient Greek" science was
already very ancient indeed. (Like Kepler to us). There was a hudge
regress in science
in these centuries, accompanied with destruction of major
scientific libraries. The "educated crowd" somehow lost
interest to science.

The epoch of Ptolemy was a brief and temporary and incomplete
revival, before Europe finally fell into the Dark Age.

In the modern times, I mean the times of Copernicus, Bruno,
Galileo, and Kepler,
heliocentric system was frequently called a
"Pithagorean teaching".
 Newton refers to "the ancients" in connection
with universal gravitation.

(I understand that these views are not quite common.
A good comprehensive source is the book
L. Russo, Forgotten revolution.)

2. Now we understand that the difference between geocentric
and heliocentric system is not so fundamental:-)
It is the question of convenient choice of coordinate system.
And we do use geocentric system in nautical almanach, for example.
It is just the question of convenience.

The real breakthrough (after the ancients) was the discovery of
Kepler laws, not the heliocentric system.
(In many cases, Copernicus system gives less precise predictions
that Ptolemy system).

> True, but then why didn't the rest of the "learned" crowd jump on the
> idea as a solution for the motion of the planets?   Or were they more
> interested in a "logically satisfying" solution than one that provided
> the easiest solution to a problem?

I afraid that the "learned crowd", beginning approx 1 cent. AD
just was not interested in these discussions, and was unable
to understand the writings of astronomers and mathematicians
of the previous century. Few centuries later there was no
learned crowd at all...

Alex.

P.S. There are many signs that we are living in the
beginning o a similar period of decline.

   

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