Creative English

Проект Чупахиной Виолетты.

Claudius Ptolemy

The Greek astronomer, astrologer, and geographer Claudius Ptolemy (ca. 100-ca. 170) established the system of mathematical astronomy that remained standard in Christian and Moslem countries until the 16th century.

Ptolemy is known to have made astronomical observations at Alexandria in Egypt between 127 and 141, and he probably lived on into the reign of Marcus Aurelius (161-180). Beyond the fact that his On the Faculty of Judgment indicates his adherence to Stoic doctrine, nothing more of his biography is available.

Content

1) The Almagest

2) Sources

3) Dictionary

4) His Influence

5) Harmonics and Optics

6) The Geography

7) Apotelesmatica

8) The Phases

9) Planetary Hypotheses

10) Canobic Inscription

The Almagest

The earliest and most influential of Ptolemy's major writings is the Almagest. In 13 books it establishes the kinematic models (purely mathematical and nonphysical) used to explain solar, lunar, and planetary motion and determines the parameters which quantify these models and permit the computation of longitudes and latitudes; of the times, durations, and magnitudes of lunar and solar eclipses; and of the times of heliacal risings and settings. Ptolemy also provides a catalog of 1, 022 fixed stars, giving for each its longitude and latitude according to an ecliptic coordinate system.

Ptolemy's is a geocentric system, though the earth is the actual center only of the sphere of the fixed stars and of the "crank mechanism" of the moon; the orbits of all the other planets are slightly eccentric. Ptolemy thus hypothesizes a mathematical system which cannot be made to agree with the rules of Aristotelian physics, which require that the center of the earth be the center of all celestial circular motions.

Canobic Inscription

This brief text was inscribed on a stele erected at Canobus near Alexandria in Egypt in 146 or 147. It contains the parameters of Ptolemy's solar, lunar, and planetary models as given in the Almagest but modified in some instances. There is also a section on the harmony of the spheres. The epoch of the Canobic Inscription is the first year of Augustus, or 30 B.C.

Planetary Hypotheses

In the two books of Planetary Hypotheses, an important cosmological work, Ptolemy "corrects" some of the parameters of the Almagest and suggests an improved model to explain planetary latitude. In the section of the first book, he proposes absolute dimensions for the celestial spheres. The second book describes a physical actualization of the mathematical models of the planets in the Almagest.

The Phases

This work originally contained two books, but only the second has survived. It is a calendar of the parapegma type, giving for each day of the Egyptian year the time of heliacal rising or setting of certain fixed stars.

Apotelesmatica

Consisting of four books, the Apotelesmatica is Ptolemy's contribution to astrological theory. He attempts in the first book to place astrology on a sound scientific basis. Astrology for Ptolemy is less exact than astronomy. In the second book, general astrology affecting whole states, societies, and regions is described. The final two books are devoted to genethlialogy, the science of predicting the events in the life of a native from the horoscope cast for the moment of his birth. The Apotelesmatica was long the main handbook for astrologers.

The Geography

In the eight books of the Geography, Ptolemy sets forth mathematical solutions to the problems of representing the spherical surface of the earth on a plane surface, but the work is largely devoted to a list of localities with their coordinates. This list is arranged by regions, with the river and mountain systems and the ethnography of each region also usually described. Claudius Ptolemy- The World

Despite his brilliant mathematical theory of map making, Ptolemy had not the requisite material to construct the accurate picture of the world that he desired. He was compelled to rely on travelers' estimates of distances, which varied widely in their reliability and were most uncertain guides. His efforts, however, provided western Europe, Byzantium, and Islam with their most detailed conception of the inhabited world. Ptolemey vosmaya karta Evropi StrasburgPtolemyWorldMap

Harmonics and Optics

These, the last two works in the surviving corpus of Ptolemy's writings, investigate two other fields included in antiquity in the general field of mathematics. The Harmonics in three books became one of the standard works on the mathematical theory of music in late antiquity and throughout the Byzantine period. The Optics in five books discussed the geometry of vision, especially mirror reflection and refraction.

His Influence

Ptolemy's brilliance as a mathematician, his exactitude, and his masterful presentation seemed to his successors to have exhausted the possibilities of mathematical astronomy and geography. To a large extent they were right. Without better instrumentation only minor adjustments in the Ptolemaic parameters or models could be made. The major "improvements" in the models - those of the School of Maragha - are designed primarily to satisfy philosophy, not astronomy; the lunar theory was the only exception. Most of the deviations from Ptolemaic methods in medieval astronomy are due to the admixture of non-Greek material and the continued use of pre-Ptolemaic elements. The Geography was never seriously challenged before the 15th century. Ptolemy urania