Article ID: CBB000932306

Mean Motions in Ptolemy's Planetary Hypotheses (2009)

unapi

Abstract In the Planetary Hypotheses, Ptolemy summarizes the planetary models that he discusses in great detail in the Almagest, but he changes the mean motions to account for more prolonged comparison of observations. He gives the mean motions in two different forms: first, in terms of `simple, unmixed' periods and next, in terms of `particular, complex' periods, which are approximations to linear combinations of the simple periods. As a consequence, all of the epoch values for the Moon and the planets are different at era Philip. This is in part a consequence of the changes in the mean motions and in part due to changes in Ptolemy's time in the anomaly, but not the longitude or latitude, of the Moon, the mean longitude of Saturn and Jupiter, but not Mars, and the anomaly of Venus and Mercury, the former a large change, the latter a small one. The pattern of parameter changes we see suggests that the analyses that yielded the Planetary Hypotheses parameters were not the elegant trio analyses of the Almagest but some sort of serial determinations of the parameters based on sequences of independent observations.

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Authors & Contributors
Jones, Alexander
Swerdlow, Noel M.
Sidoli, Nathan Camillo
Duke, Dennis W.
Volk, Katharina
Tihon, Anne
Concepts
Astronomy
Cosmology
Solar system; planets
Celestial mechanics
Astrology
Solar astronomy
Time Periods
Ancient
2nd century
Early modern
Modern
Renaissance
Medieval
Places
Greece
Rome (Italy)
Middle and Near East
Assyria
Babylon (extinct city)
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