History of Science Online - Course Info - Time tips - Semester at a glance - Weekly assignments at a glance - Timeline - Week 5: Hellenistic Science

Hipparchos of Nikaia, fl. 150 BC

Background

Above all, Hipparchos represents the cross-cultural fusion of

1. the qualitative, geometric tradition of early Greek astronomy (e.g., Eudoxos); and
2. the quantitative mathematical tradition of Babylonian astronomy (e.g., Kidinnu).

With Hipparchos, Babylonian (1) numerical parameters, (2) astrological practices and beliefs, and (3) ideals of quantitative prediction all were appropriated into Hellenistic astronomy. This remarkable fruit of cross-cultural communication is illustrated by the way Hipparchos took the geometric models of Apollonios of Perga (epicycle-deferent models) and made them quantitative, incorporating Babylonian numerical parameters, to accurately model the retrograde motion of planets.

A similar point is illustrated in the succinct description of Hipparchos you already encountered in Stars over Ancient Babylon: "In early Greek natural philosophy, there was nothing comparable to the Babylonian achievement in astronomy, until cultural interchange between Mesopotamia and Greece increased after Alexander the Great. Around 150 BC, Hipparchos of Nicaea discovered the 26,000 year cycle of precession. This discovery was possible only because Hipparchos used Babylonian determinations of the length of the year."

For reasons like these, many historians of science regard Hipparchos as the most significant figure in ancient astronomy.

In addition to the discovery of precession and the three Babylonian influences noted above, Hipparchos also developed tables of chords (similar to the modern sine function), catalogued the stars by numerically specifying their locations; and accurately calculated the relative sizes and distances of the Sun and the Moon relative to the size of the Earth.

Assignments

1. Read Michael Crowe, p. 29, "Hipparchus of Nicaea" (ch. 2); pp. 30-35 (ch. 3); and pp. 38-40, "The Solar Theory of Hipparchus" and "The Lunar Theory of Hipparchus" (ch. 3). Don't get bogged down in Crowe's geometrical proofs; just read for the "gist" of the models Crowe explains. (Of course, if you're interested in the technical details, Crowe makes a superb introductory guide.)
2. Explore these animated models of various geometrical devices to ensure that you understand them:
   • Earth eccentric; with Sun.
   • Dennis Duke, various models (P = the planet in each model). Be sure to try these: Venus, Mars and Jupiter. The Earth is roughly central in each model. Note the relative motions of each planet and the Sun.

    

	HSCI 3013. History of Science to 17th century Kerry Magruder, Instructor, 2004-14 Brent Purkaple, TA Report typos or broken links	Go to this course at Janux spellcheck.net | wordcounter.net Many thanks to the pedagogical model developed in Mythology and Folklore and other online courses by Laura Gibbs, which have been an inspiration for this course.	Academic Calendar
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