Hipparchus

Hipparchus of Rhodes

Born: 180 BC in Nicaea (now Iznik), Bithynia (now Turkey)
Died: 125 BC in Rhodes, Greece

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Little is known of Hipparchus's life, but he is known to have worked in Nicaea, Rhodes and Alexandria. worked on trigonometry. He introduced the division of a circle into 360 degrees into Greece and produced a table of chords, an early example of trig tables. He also gave methods for solving spherical triangles and advocated the use of latitude and longitude for position on the Earth.

Hipparchus calculated the length of the year to within 6.5 minutes and discovered the precession of the equinoxes. Hipparchus's value of 46" for the annual precession is good compared with the modern value of 50.26" and much better than the figure of 36" the Ptolemy was to obtain nearly 300 years later.

His star catalog, containing about 850 stars, lists magnitude with a six point scale similar to that used today. His star catalogue, completed in 129 BC, was used by Ptolemy and its quality was such that it was even used by Halley.

References elsewhere in this archive:

Tell me more about trigonometry

References:

  1. Dictionary of Scientific Biography
  2. Biography in Encyclopaedia Britannica
  3. O Neugebauer, A history of ancient mathematical astronomy (New York, 1975).
  4. G Sarton, A History of Science, Vol. 2, Hellenistic Science and Culture in the Last Three Centuries B.C. (1959). 
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JOC/EFR February 1996