Re: OT, was Ptolemy in Re: VMs: Traditional Astrology and the Flat Earth

[elvogt@xxxxxxxxxxx]

Zitat von Bruce Grant <bgrant@xxxxxxxxxxxxx>:

> elvogt@xxxxxxxxxxx wrote:
> 
> >Zitat von Pamela Richards <spirlhelix@xxxxxxxxx>:
> >
> >>tolemy on the Shape of the Earth, from the Almagest,
> >>Book I, Ch. 4.:
> >>
> >>                               ...And since the
> >>differences in the hours is found to be proportional
> >>to the distances between the places, one would
> >>reasonably suppose the surface of the earth
> >>spherical...
> >>    
> >>
> >
> >That is pretty cool. How on Earth did he measure that...?
> >
> 
> I seem to remember reading somewhere that the Greeks had two other 
> arguments for theEarth being spherical:
> 
> 1)   that, as a ship sails away in any direction, its hull disappears 
> from view before the sails do
> 
> 2)  that the edge of the Earth's shadow on the Moon during a lunar 
> eclipse always appears circular (no corners).
> 
> Bruce
> 

Hi Bruce,

Pretty good answer, it seems to apply to the wrong question, though. :-)

How did Ptolemy measure the time differences in rise and setting of stars with 
the accuracy he claims?

   Elmar



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