Early Greek Astronomy
And
Ptolemy’s
Almagest
Eratosthenes
• Finds the size of the earth within 5%
)(2
500
360
5.7
EarthofRadius
mileso
o
milesREarth 38205.72
500360
%5.3
3950
aboutError
milesradiusActual
Important Ratio
Distance to the Moon
• If the sun is a point source
Trigonometry Tables in the Almagest
• Not in terms of our trig functions sine, cosine, tangent, etc.
Greek Number System
