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Re: A rotating Earth?



A good reference is Kuhn's The Copernican Revolution, written before
Structures...

Indeed. To summarize a few of the details in Kuhn:

The idea that the daily motion of the sun and stars might be
due to the earth's rotation dates back to Heraclides of Pontus,
4th century B.C. He lived about a hundred years before
Aristarchus of Samos who was (probably) the first to suggest
that the earth might revolve around the sun. Aristarchus was
also the first to accurately calculate the true size and distance
of the moon, and to estimate the same for the sun. His values
for the sun were way too low, but he at least proved that the
sun must be several times larger than the earth. We don't know
what other reasons he might have had for suggesting that the
earth orbits the sun.

There's not much in Kuhn about ancient attempts to deal with the
physics implications of a moving earth. Probably too little is
known about what arguments Heraclides and Aristarchus would have
used. Kuhn does discuss the fourteenth-century scholastics
Jean Buridan and Nicole Oresme, who challenged much of Aristotle's
physics along these lines.

Copernicus almost surely would have been aware of most of these
ideas, though not necessarily of every historical detail.
But Copernicus's physics was no more advanced than that of
Oresme and Buridan, perhaps less. He still postulated physical
crystalline spheres to carry the planets (including the earth)
around in their orbits. He endowed the earth with three separate
motions: a daily spin around its axis, an annual orbit around
the sun, and an annual conical motion to keep the earth's north
pole pointed toward the north star, despite the fact that the
rigid sphere carrying the earth around the sun would tend to
cause the axis to precess. His book was influential because of
its mathematical rigor and detail, not because its hypotheses
were physically plausible.

That's enough from me. Read Kuhn.

Dan