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May 29, 2023 · The primary argument put forth by proponents of the pre-11th century AD existence of Albanians revolves around the purported reference made by the Greek author Claudius Ptolemy in his work Geography around 150 AD, where he mentions Albans and Albanopolis. However, it is important to note that Ptolemy's original work is entirely lost to us.…
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Ptolemy’s mathematical model of the universe had a profound influence on medieval astronomy in the Islamic world and Europe. The Ptolemaic system was a geocentric system that postulated that the apparently irregular paths of the Sun, Moon, and planets were actually a combination of several regular circular motions seen in perspective from a stationary Earth.
How did Ptolemy impact the world?
In addition to his astronomical work, Ptolemy recorded longitudes and latitudes in degrees for roughly 8,000 locations on his world map, giving a detailed image of the inhabited world as it was known to a resident of the Roman Empire at its height. While distorted, his work influenced Byzantine and Renaissance cartographers.
What were Ptolemy’s achievements?
Ptolemy made contributions to astronomy, mathematics, geography, musical theory, and optics. He compiled a star catalog and the earliest surviving table of a trigonometric function and established mathematically that an object and its mirror image must make equal angles to a mirror. In several fields his writings represent the culminating achievement of Greco-Roman science.
Ptolemy (born c. 100 ce—died c. 170 ce) an Egyptian astronomer, mathematician, and geographer of Greek descent who flourished in Alexandria during the 2nd century ce. In several fields his writings represent the culminating achievement of Greco-Roman science, particularly his geocentric (Earth-centred) model of the universe now known as the Ptolemaic system.
The book that is now generally known as the Almagest (from a hybrid of Arabic and Greek, “the greatest”) was called by Ptolemy Hē mathēmatikē syntaxis (“The Mathematical Collection”) because he believed that its subject, the motions of the heavenly bodies, could be explained in mathematical terms. The opening chapters present empirical arguments for the basic cosmological framework within which Ptolemy worked. Earth, he argued, is a stationary sphere at the centre of a vastly larger celestial sphere that revolves at a perfectly uniform rate around Earth, carrying with it the stars, planets, Sun, and Moon—thereby causing their daily risings and settings. Through the course of a year the Sun slowly traces out a great circle, known as the ecliptic, against the rotation of the celestial sphere. (The Moon and planets similarly travel backward—hence, the planets were also known as “wandering stars”—against the “fixed stars” found in the ecliptic.) The fundamental assumption of the Almagest is that the apparently irregular movements of the heavenly bodies are in reality combinations of regular, uniform, circular motions.
How much of the Almagest is original is difficult to determine because almost all of the preceding technical astronomical literature is now lost. Ptolemy credited Hipparchus (mid-2nd century bce) with essential elements of his solar theory, as well as parts of his lunar theory, while denying that Hipparchus constructed planetary models. Ptolemy made only a few vague and disparaging remarks regarding theoretical work over the intervening three centuries, yet the study of the planets undoubtedly made great strides during that interval. Moreover, Ptolemy’s veracity, especially as an observer, has been controversial since the time of the astronomer Tycho Brahe (1546–1601). Brahe pointed out that solar observations Ptolemy claimed to have made in 141 are definitely not genuine, and there are strong arguments for doubting that Ptolemy independently observed the more than 1,000 stars listed in his star catalog. What is not disputed, however, is the mastery of mathematical analysis that Ptolemy exhibited.
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Ptolemy was preeminently responsible for the geocentric cosmology that prevailed in the Islamic world and in medieval Europe. This was not due to the Almagest so much as a later treatise, Hypotheseis tōn planōmenōn (Planetary Hypotheses). In this work he proposed what is now called the Ptolemaic system—a unified system in which each heavenly body is attached to its own sphere and the set of spheres nested so that it extends without gaps from Earth to the celestial sphere. The numerical tables in the Almagest (which enabled planetary positions and other celestial phenomena to be calculated for arbitrary dates) had a profound influence on medieval astronomy, in part through a separate, revised version of the tables that Ptolemy published as Procheiroi kanones (“Handy Tables”). Ptolemy taught later astronomers how to use quantitative observations with recorded dates to revise cosmological models.
Ptolemy also attempted to place astrology on a sound basis in Apotelesmatika (“Astrological Influences”), later known as the Tetrabiblos for its four volumes. He believed that astrology is a legitimate, though inexact, science that describes the physical effects of the heavens on terrestrial life. Ptolemy accepted the basic validity of the traditional astrological doctrines, but he revised the details to reconcile the practice with an Aristotelian conception of nature, matter, and change. Of Ptolemy’s writings, the Tetrabiblos is the most foreign to modern readers, who do not accept astral prognostication and a cosmology driven by the interplay of basic qualities such as hot, cold, wet, and dry.
Ptolemy has a prominent place in the history of mathematics primarily because of the mathematical methods he applied to astronomical problems. His contributions to trigonometry are especially important. For instance, Ptolemy’s table of the lengths of chords in a circle is the earliest surviving table of a trigonometric function. He also applied fundamental theorems in spherical trigonometry (apparently discovered half a century earlier by Menelaus of Alexandria) to the solution of many basic astronomical problems.
Among Ptolemy’s earliest treatises, the Harmonics investigated musical theory while steering a middle course between an extreme empiricism and the mystical arithmetical speculations associated with Pythagoreanism. Ptolemy’s discussion of the roles of reason and the senses in acquiring scientific knowledge have bearing beyond music theory.
Ptolemy was a geographer, mathematician, astronomer and poet, whose works resonated for many centuries. There are three of his surviving works that have historical significance, the Almagest (the Great Treatise) on mathematics, the Tetrabiblos (four Books) about philosophy and astronomy, and Geographia, the work that concerns us here. The ...
Sep 7, 2023 · Claudius Ptolemy (c. 100 to c. 170 CE) was an Alexandrian mathematician, astronomer, and geographer. His works survived antiquity and the Middle Ages intact, and his theories, particularly on a geocentric model of the universe with planets following orbits within orbits, were hugely influential until they were replaced by the heliocentric model ...
- Mark Cartwright
- Claudius Ptolemy is best known for being a 2nd-century Alexandrian astronomer who created a model of the universe with Earth as its centre. Ptolemy...
- Claudius Ptolemy's theory of the universe is that Earth is at the centre while the other planets and the Sun move around it. These heavenly bodies...
- Claudius Ptolemy's world map was relatively accurate for the Mediterranean region, but because nobody had been there, other parts of the world were...
Jan 13, 2022 · The earliest printed atlases were editions of the geographical text of Claudius Ptolemy (or Ptolemaeus), a Greek astronomer and geographer working in Alexandria, circa 150 A.D. Frequently accorded the accolade the “Father of Geography”, Ptolemy’s text dominated geographical study, in both the Christian and Muslim worlds, for over fifteen hundred years.
Sep 14, 2024 · Ptolemy - Geographer, Astronomer, Mathematician: Ptolemy’s fame as a geographer is hardly less than his fame as an astronomer. Geōgraphikē hyphēgēsis (Guide to Geography) provided all the information and techniques required to draw maps of the portion of the world known by Ptolemy’s contemporaries. By his own admission, Ptolemy did not attempt to collect and sift all the geographical ...
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What if Ptolemy had not preserved the substance of his cartographical work?
Ptolemy's theory of vision consisted of rays (or flux) coming from the eye forming a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer's intellect about the distance and orientation of surfaces.
