World Library  
Flag as Inappropriate
Email this Article

Timocharis

Article Id: WHEBN0000236984
Reproduction Date:

Title: Timocharis  
Author: World Heritage Encyclopedia
Language: English
Subject: Axial precession, Hipparchus, Aristyllus, Ancient Greek astronomy, 320 BC
Collection: 260 Bc, 260 Bc Deaths, 260S Bc Deaths, 320 Bc, 320 Bc Births, 320S Bc Births, 3Rd-Century Bc Greek People, Ancient Greek Astronomers
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Timocharis

Timocharis of Alexandria (Greek: Τιμόχαρις; c. 320 – 260 BC) was a Greek astronomer and philosopher. Likely born in Alexandria, he was a contemporary of Euclid.

What little is known about Timocharis comes from citations by Ptolemy in the Almagest. These indicate that Timocharis worked in Alexandria during the 290s and 280s BCE. Ptolemy lists the declination of 18 stars as recorded by Timocharis or Aristillus in roughly the year 290 BCE.[1] Between 295 and 272 BCE, Timocharis recorded four lunar occultations and the passage of the planet Venus across a star.[2] These were recorded using both the Egyptian and Athenian calendars.[3] The observed stellar passage by Venus may have occurred on October 12, 272 BCE when the planet came within 15 arcminutes of the star η Virginis.[4]

The observations by Timocharis are among the oldest Greek records that can be assigned a specific date. They are only exceeded by records of the summer solstice of 432 BCE, as noted by Euctemon and Meton.[5] Timocharis worked with Aristillus in an astronomical observatory that was most likely part of the Library of Alexandria. Their equipment would have been simple, most likely consisting of gnomons, sundials and an armillary sphere. The two were contemporaries of Aristarchus of Samos, but it is unclear whether there was any association between Timocharis and Aristarchus.[6]

During his astronomical observations, Timocharis recorded that the star Spica was located 8° west of the Autumnal equinox. Later, Hipparchus observed that Spica was only 6° west of the Autumnal equinox. Hipparchus was able to deduce the period during which Timocharis made his observations based upon the records of earlier lunar eclipses. From this difference, Hipparchus discovered that the longitudes of the stars had changed over time, which led him to determine the first value of the precession of the equinoxes as no less than 1/100° per year.[5]

In approximately 3rd century BC, with the help of Aristillus, he created the first star catalogue in the Western world.

He made the third recorded mention of Mercury.

The crater Timocharis on the Moon is named after him.[7]

References

  1. ^ Newton, R. R. (1974). "The obliquity of the ecliptic two millenia ago".  
  2. ^ Jones, Alexander (1999). Astronomical papyri from Oxyrhynchus 1–2. DIANE Publishing. p. 84.  
  3. ^ Jones, A. (1997), On the reconstructed Macedonian and Egyptian lunar calendars (PDF) 119, pp. 157–166, retrieved 2009-09-10 
  4. ^ Fomenko, A. T.; Vi︠a︡cheslavovich, Vladimir Kalashnikov; Nosovskiĭ, Gleb Vladimirovich (1993). Geometrical and statistical methods of analysis of star configurations: dating Ptolemy's Almagest. CRC Press. p. 215.  
  5. ^ a b Evans, James (1998). The History & Practice of Ancient Astronomy. Oxford University Press US. p. 259.  
  6. ^ Sarton, George (1993). Hellenistic science and culture in the last three centuries B.C. Courier Dover Publications. p. 53.  
  7. ^ Blue, Jennifer. "Gazetteer of Planetary Nomenclature". United States Geological Survey. Retrieved 2009-09-10. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.