Claudius Ptolemaeus (in Greek: Κλαύδιος Πτολεμαῖος), commonly called Ptolémée (Ptolémaïs de Thébaïde (High-Egypt) towards 90 - Canope towards 168) was a astronomer and Greek astrologer which lived with Alexandria (today in Egypt). It is also one of the precursors of the Géographie.

Ptolémée was the author of several scientific treaties, whose two exerted thereafter a very great influence on sciences Islamic and European. One is the treaty of Astronomie, which is known today under the name of the Almageste (in Greek, Η μεγάλη Σύνταξις, the great treaty ). The other is the Géographie , which is a discussion thorough on knowledge Géographique S of the world gréco-Roman.

Astronomy

Ptolémée is the author of a treaty of astronomy known under the name of the Almageste ( Al in Arabic, follow-up of a Greek superlative means “the very large one”). In this work, he proposed a geocentric model Solar system, which was accepted like model in the world S Occident with and Arabic during more than thousand three hundred years. Also, this system was recognized in Europe and was used as reference during more than 14 centuries before Nicolas Copernic discovers his theory copernician: The heliocentric system or Héliocentrisme (1543), supported by Galileo Galilei (Galileo), which was shown of heresy by the Church, and Kepler. The Almageste also contains a star catalog and a list forty-eight Constellation S, former to the modern system of constellations although not covering all the celestial Sphère. Ptolémée described the Astrolabe probably invented by Hipparque.

Geography

Its Géographie is another major work. It is about a compilation of knowledge of the Géographie of the world at the time of the Roman Empire. Ptolémée was primarily based on work of another geographer, Marinus de Tyr, and on the geographical indices of the empires Roman and Perse, but the majority of its sources beyond the perimeter of the empire were doubtful origins.

The first part of the Géographie is a discussion on the data and the methods which it used. As for the model of the solar system in the Almageste , Ptolémée unified in a great unit all information it had. It allotted Coordonnée S to all the places and characteristics geographical which it knew, in a grid which covered the sphere. The Latitude was measured starting from the equator, like today, but Ptolémée preferred to rather express it according to the duration of the longest day than in degree S (the duration of the Solstice of summer passes from 12:00 to 24:00 as one moves away from the equator towards the Polar circle). It fixed the Méridien Longitude 0 at the point more in the west which it knew, the the Canaries.

Ptolémée also imagined and provided instructions on the way of drawing charts, at the same time of all the world inhabited ( ecoymene ) and Roman provinces. In the second part of the Geography , it provided the topographic lists necessary, and of the legends to the charts. Its ecoymene covered 180 degrees of longitude of the Canaries (in the Atlantic Ocean) until the China, and approximately 80 degrees of latitude of the Arctique to the the Indies and far in Africa. Ptolémée was quite conscious that its knowledge covered only one quarter of the sphere.

Unfortunately, more old charts of the manuscripts of the Géographie of Ptolémée go back only to 1300 approximately, after the redécouverte of the text by Maximus Planudes.

Astrology

The treaty of Ptolémée on astrology, the Tetrabiblos , was the astrological work most famous of Antiquity. He exerted a great influence in the study of the celestial bodies in the sublunary sphere . Thus, it provided explanations of the astrological effects of the Planet S, according to their effects heating, refreshing, dampener, and drying.

Music

Ptolémée also wrote the Harmoniques , a treaty of musicology of reference. After a criticism of approaches of its predecessors, Ptolémée pleads there to base musical intervals on mathematical proportions (contrary to the partisans of Aristoxène) supported by empirical observation (contrary to the purely theoretical approach of the École pythagorician). It presented its own divisions of the tétracorde and the octave, which it derived with the assistance from a monocorde. The interest of Ptolémée for astronomy also appears in a discussion on the music of the spheres.

See too

Homages

The Astéroïde (4001) Ptolémée (4001 Ptolemaeus) was named in its honor, just like the Ptolémée craters on Mars and the the Moon and also a storm on Venus.

Internal bond

Nds-nl: Claudius Ptolemaeus Simple: Ptolemy

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