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