Re: Astronomy - History

["Paul Camp" <pjcamp@coastal.edu>]

> Are you sure you have indeed produced an ellipse, in the mathematical 
> sense, or just a shape which is generally elliptical.  Kepler's problem 
> what that try as he may, he could not account for the appearance of the 
> orbit of Mars with sets of circles, and in the end had to use a 
> non-circular device, the ellipse.  This suggests that ellipses cannot be 
> made from constructions of circles...but as has happened the the past, I 
> could be wrong.
>
> cheers
>
> joe bellina

I think you're right. Isn't this just a Fourier expansion of an 
ellipse? If so, strictly speaking you need an infinite number of 
circles.

Al Bachman writes:

> 1) How does one determine the orbit of a superior planet, eg Mars,
> from visual observations? A reference will do.

Kepler's method was to select from Brahe's set of observations only 
those made on the same day in different years so that the Earth was 
effectively frozen in place. Park's book The How and The Why has a 
pretty good section on this. Good luck finding numerical data on 
Ptolemy's model. You might try Neugebauer, A History of Ancient 
Mathematical Astronomy, Springer-Verlag 1975. I don't know if it 
contains this info since I am no longer at an institution whose 
library has a copy. But it might.

Paul J. Camp                   "The Beauty of the Universe
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