Ptolémée

This article concerns the astronomer. For the Pharaons of the period lagide, to see .


Ptolémée
Ptolémée

Claudius Ptolemaeus, commonly called Ptolémée (Ptolémaïs de Thébaïde () 90 - Canope 168) was one and astrologer Greek who lived with Alexandria (today in ). It is also one of the precursors of .

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 astronomy, which is known today under the name ofAlmageste (in Greek? ?????? ????????, The great treaty). The other is Geography, which is a discussion thorough on geographical knowledge of the world gréco-Roman.

Synopsis

Astronomy

Ptolémée is the author of a treaty of astronomy known under the name ofAlmageste (Al in Arabic, follow-up of a Greek superlative means "the very large one"). In this work, it proposed a model geocentric , which was accepted like model in the Western worlds and Arabic during more than thousand three hundred years. Almageste also contains a star catalogue and a list the forty-eight one , former to the modern system of constellations although not covering all celestial sphere.

Geography

The chart of the world of Ptolémée, reconstituted from its Geographia (towards 150), the countries indicate of Serica, Sinae () with the extreme right-hand side, beyond the island of Taprobane (, too large) and itAurea Chersonesus ().

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

The first part of Geography is a discussion on the data and the methods which it used. As for the model of the solar system inAlmageste, Ptolémée unified in a great unit all information it had. It allotted co-ordinates with all the geographical places and characteristics that he knew, in a grid which covered the sphere. latitude was measured fromequator, like today, but Ptolémée preferred to rather express it according to the duration of the longest day than in degrees (duration of solstice from summer from 12 noon passes to 12 midnight as one moves away from the equator towards polar circle). It fixed it meridian line of longitude 0 at the point more in the west which he knew, them The Canaries.

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

Unfortunately, oldest charts of the manuscripts of Geography from Ptolémée go back only to approximately, after the rediscovery of the text by Maximus Planudes.

Astrology

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

Music

Ptolémée also wrote them Harmonics, 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 ofSchool pythagorician). It presented its own divisions of the tétracorde and ofoctave, that it derived with the assistance from a monocorde. The interest of Ptolémée for astronomy also appears in a discussion on music of the spheres.

Homages

4001 Ptolémée (4001 Ptolemaeus) was named in its honor, just like the Ptolémée craters on and on .

External bond

 

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