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    Re: Universe of the ancient Greeks.
    From: Frank Reed CT
    Date: 2006 Mar 14, 02:12 EST

    Lu Abel, you wrote:
    "While I hesitate to  disagree with such giants of this list as George
    Huxtable and Frank  Reed..."
    Ho ho ho. For the record, I am 5 foot 8, quite ungigantic, and  an amateur in
    these matters, just like everyone else on this list.
    And  then you asked:
    "what about the motion of the planets?"
    What about  'em?? It is a popular myth that the Copernican system was
    significantly simpler  than the Ptolemaic. Most of "de Revolutionibus" is actually
    about epicycles.  There's some of this that's worth reading in a book I
    mentioned recently "The  Book Nobody Read" by Owen Gingerich. He has a section on the
    popular  misconception that the Ptolemaic system was slowly weighed down by
    "epicycles  upon epicycles".
    "If earth and the planets all were in  circular
    orbits around the Sun, the apparent motion of the planets was  easily
    explained by their relative motion with respect to the  earth."
    EARTH and the planets... We say it so easily today. The Earth is  a planet,
    of course, why didn't we think of that earlier? In fact, it was the  first
    planet discovered by science. The others had been seen since the dawn of  history.
    But it's not obvious at all until you invent the telescope.
    So  here's Copernicus, pre-telescope, and he's got an explanation for the
    Solar  System. It's one that is certainly not more complicated than the
    Ptolemaic, and it produces predicted positions that are just as good (but still
    pretty bad in many cases). An equivalent model producing equivalent data  starting
    from radically different assumptions... That's the sort of thing that
    launches a revolution.
    42.0N 87.7W, or 41.4N  72.1W.

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