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    Re: Universe of the ancient Greeks.
    From: Bill B
    Date: 2006 Mar 13, 23:01 -0500

    > To me, the great leap of imagination by Copernicus and Galileo was to
    > realize that a heliocentric universe could explain the motion of the
    > planets quite simply.  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.
    
    
    Sorry Lu, I did not address this adequately.  Not only a perfect circle with
    the sun at the center, but via Greek hand-me-downs, they must also move at a
    constant velocity along that arc.  Even with a heliocentric model, it
    doesn't work once you get accurate measurements (Tycho Brahe).  So if the
    earth moves in a circle around the sun, with the sun at the center of the
    circle, how do you account for the sun getting larger then smaller, or the
    eqn. of time?  You can't without a Rube Goldberg model.
    
    Bill
    
    
    

       
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