Aristarchus On The Sizes and Distances - Results

Results

The above formulae can be used to reconstruct the results of Aristarchus. The following table shows the results of a reconstruction using n = 2, x = 19.1 (φ = 87°) and θ = 1°, alongside the modern day accepted values.

Quantity Relation Reconstruction Modern
s/t Sun's radius in Earth radii 6.7 109
t/ℓ Earth's radius in Moon radii 2.85 3.50
L/t Earth-Moon distance in Earth radii 20 60.32
S/t Earth-Sun distance in Earth radii 380 23,500

The error in this calculation comes primarily from the poor values for x and θ. The poor value for θ is especially surprising, since Archimedes writes that Aristarchus was the first to determine that the Sun and Moon had an apparent diameter of half a degree. This would give a value of θ = 0.25, and a corresponding distance to the moon of 80 Earth radii, a much better estimate. The disagreement of the work with Archimedes seems to be due to its taking an Aristarchos statement that the lunisolar diameter is 1/15 of a "meros" of the zodiac to mean 1/15 of a zodiacal sign (30°), unaware that the Greek word "meros" meant either "portion" or 7°1/2; and 1/15 of the latter amount is 1°/2, in agreement with Archimedes' testimony.

A similar procedure was later used by Hipparchus, who estimated the mean distance to the moon as 67 Earth radii, and Ptolemy, who took 59 Earth radii for this value.

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