Hipparchus
(
Ἵππαρχος).
1.
A son of Pisistratus. (See
Pisistratidae.)
2.
A Greek mathematician, the founder of scientific astronomy. He was born at Nicaea in
Bithynia about B.C. 160, lived chiefly at Rhodes and Alexandria, and died about B.C. 120. He
discovered the precession of the equinoxes, settled more accurately the length of the solar
year, as also of the revolution of the moon, and the magnitude and distances of the heavenly
bodies. He placed mathematical geography on a firmer basis, by teaching the application of
the latitude and longitude of the stars to marking the position of places on the surface of
the earth. He is also regarded as having invented trigonometry. In plane trigonometry he
constructed a table of chords of arcs, which is practically the same as one of natural sines;
and in spherical trigonometry he had some methods of solving triangles. Of his numerous
writings we possess only his commentary on the
Phaenomena of Eudoxus and
Aratus and a catalogue of 1026 fixed stars. The famous
Almagest of Ptolemy
(
Μεγίστη Σύνταξις) is founded on the writings of
Hipparchus. See Ball,
Short Hist. of Mathematics, pp. 79-81, 90
(London,
1888).