Hipparchus (redirected from Hipparchos)

Hipparchus, Athenian political figure

Hipparchus (hĭpär`kəs), c.555–514 B.C., Athenian political figure, son of Pisistratus. After the death of his father, he was closely associated with his brother Hippias, tyrant of Athens, in ruling the Athenian city-state. Under Hippias he was a patron of the arts and sponsored the poets Anacreon and Simonides. He was slain by Harmodius and Aristogiton because of his personal vices.

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Hipparchus, Greek astronomer

Hipparchus, fl. 2d cent. B.C., Greek astronomer, b. Nicaea, Bithynia. He is the first systematic astronomer of whom there are records. He made his observations chiefly on the island of Rhodes. Ptolemy's geocentric theory of the universe was based largely on the conclusions of Hipparchus, a record of whose researches is preserved in the Almagest of Ptolemy. In it Hipparchus is credited with the discovery of the precession of the equinoxes, the eccentricity of the sun's apparent orbit, and certain inequalities of the motions of the moon. He determined the lengths of the seasons and accurately measured the year. He calculated the sizes of the sun and moon using eclipses. He also made the first known comprehensive chart of the heavens giving the positions of at least 850 stars, and he divided them into brightness classes, a system of magnitudes later expanded by Ptolemy. Hipparchus suggested a method of determining longitude by observing the parallax of the moon in eclipse. He is believed to have been the first to make systematic use of trigonometry, and he computed a table of chords roughly equivalent to trigonometrical sines. Only one of his works, a commentary on the work of Aratus and Eudoxus, survives.

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Hipparchus

 or Hipparchos

(born , Nicaea, Bithynia—died after 127 BC, Rhodes?) Greek astronomer and mathematician. He discovered the precession of the equinoxes (see equinoxes, precession of the), calculated the length of the year to within 6.5 minutes, compiled the first known star catalog, and made an early formulation of trigonometry. His observations were painstaking and extremely accurate. He rejected all astrology but also Sun-centred views of the universe; his views had a profound influence on Ptolemy. His star catalog logged the positions of the stars in terms of celestial coordinates, listed about 850 stars, and specified their brightnesses by a system of six magnitudes similar to today's. He adequately accounted for the irregularities in the Moon's motion that are due to its elliptical orbit. His main contribution to geography was to apply rigorous mathematical principles to the determination of places on Earth's surface, and he was the first to do so by specifying latitude and longitude.

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Hipparchus

1. 2nd century bc, Greek astronomer. He discovered the precession of the equinoxes, calculated the length of the solar year, and developed trigonometry

2. died 514 bc, tyrant of Athens (527--514)

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Hipparchus

(fl. 146–127 B.C.) astronomer who calculated the year and discovered the precession of the equinoxes. [Turkish Hist.: EB, V: 55]

See : Astronomy

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Hipparchus

Born circa 180-190 B.C. in Nicaea; died 125 B.C. in Rhodes. Ancient Greek scientist; one of the founders of astronomy.

Hipparchus carried out the first systematic observations and investigations of the sky. He worked out the theory and compiled tables of the motions of the sun and moon, as well as a table of solar eclipses. This work was based on a geocentric system; Hipparchus rejected the idea of heliocentricism as a hypothesis without sufficient proof. He described lunar motion at full and new moon and rather accurately estimated the distance between the moon and the earth. Circa 129-127 B.C. he compiled a catalog, which was enormous for those times, of the positions of 850 stars, classifying the stars according to brightness into a system of six magnitudes. Comparing his positions of the stars with earlier ones (third century B.C.), Hipparchus discovered the phenomenon of precession and rather accurately estimated its magnitude. In connection with this, he determined the length of the tropical year (with an error of no more than 6 minutes) and its difference from the sidereal year (15 minutes; at present, 20 minutes). Hipparchus determined the inclination of the equator to the ecliptic, with an error of 5’. He introduced the geographical coordinates of latitude and longitude. His works in the original have not been preserved. The principal source of information on his work is Ptolemy’s Almagest.

REFERENCES

Seleshnikov, S. I. Astronomiia i kosmonavtika. Kiev, 1967.
Eremeeva, A. I. Vydaiushchiesia astronomy mira. Moscow, 1966. Pages 32-34. (List of works about Hipparchus.)

A. I. EREMEEVA