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Astronomy and Geography

Some Unexplored Connections in Ptolemy

Klaus Geus    Freie Universität, Berlin, Deutschland    

Irina Tupikova    Lohrmann Observatory, Technische Universität Dresden, Deutschland    

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abstract

The authors discuss the so-called ‘zenith star method’, first mentioned in Ptolemy’s Geography (ca. AD 150), from an astronomical and historical perspective. They reach the conclusion that the exact representation in some texts, i.e. that the distance between the two points of culmination is 1°, does not in fact concern a pair of stars culminating at the zenith but only one star which is measured at an angle of 1Æ from the zenith. This peculiar condition points to a historical measurement carried out by an unknown Greek astronomer: it makes use of the fact that the bright star Pollux (β Geminorum) culminated at Alexandria with an angle distance of 1° from the zenith or (which is equivalent) culminated at the zenith over a place 1° south of Alexandria (ca. 110 km). Although a scholium to Ptolemy’s Geography claims this, the unknown author of the experiment is in all probability not Hipparchus of Nicaea.

Pubblicato
01 Settembre 2017
Accettato
31 Marzo 2017
Presentato
13 Gennaio 2017
Lingua
EN
ISBN (PRINT)
978-88-7543-440-3
ISBN (EBOOK)
978-88-6969-165-2

Keywords: HipparchusZenith star methodPtolemyCircumference of the earth

Copyright: © 2017 Klaus Geus, Irina Tupikova. This is an open-access work distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction is permitted, provided that the original author(s) and the copyright owner(s) are credited and that the original publication is cited, in accordance with accepted academic practice. The license allows for commercial use. No use, distribution or reproduction is permitted which does not comply with these terms.