Historians have more information about his observations since they became the basis for later charts and theories. The first of his observations that can be dated exactly occurred on March 12, His last recorded one was February 2, Some experts think his life spanned the years 87 — However long he lived, Ptolemy did much to advance science and appears to have been a very accomplished observer of the stars and planets.
We get a few clues about his background from his name: Claudius Ptolemy. Together, they indicate that his family was probably Greek and they had settled in Egypt which was under Roman rule for some time before his birth. Very little else is known about his origins. Ptolemy's work was quite advanced, considering that he didn't have the types of tools that astronomers rely on today. He lived in a time of "naked eye" observations; no telescopes existed to make his life easier.
Among other topics. Ptolemy wrote about the Greek geocentric view of the universe which put Earth at the center of everything. That view seemed to quite nicely put humans at the center of things, as well, a notion that was hard to shake until Galileo's time. Ptolemy also calculated the apparent motions of the known planets. He did this by synthesizing and extending the work of Hipparchus of Rhodes , an astronomer who came up with a system of epicycles and eccentric circles to explain why Earth was the center of the solar system.
Epicycles are small circles whose centers move around the circumferences of larger ones. He used at least 80 of these tiny circular "orbits' to explain the motions of the Sun, the Moon, and the five planets known in his time. Ptolemy expanded this concept and made many fine calculations to fine-tune it.
This system came to be called the Ptolemaic System. It was the linchpin of the theories about objects' motions in the sky for nearly a millennium and a half. It predicted the positions of the planets accurately enough for naked-eye observations, but it turned out to be wrong and too complicated.
As with most other scientific ideas, simpler is better, and coming up with loopy circles wasn't a good answer to why planets orbit the way they do. Ptolemy was also a prolific writer in the subjects and disciplined he studied. For astronomy, he described his system in his books that make up the Almagest also known as Mathematical Syntaxis. It was a volume mathematical explanation of astronomy containing information about the numerical and geometrical concepts behind the motions of the Moon and known planets.
He also included a star catalog that contained 48 constellations star patterns he could observe, all with the same names that are still in use today. As a further example of some of his scholarship, he made regular observations of the sky at the time of the solstices and equinoxes, which allowed him to figure out the lengths of the seasons.
From this information, he then went on to try and describe the motion of the Sun around our planet. Ptolemy first of all justifies his description of the universe based on the earth-centred system described by Aristotle. It is a view of the world based on a fixed earth around which the sphere of the fixed stars rotates every day, this carrying with it the spheres of the sun, moon, and planets.
Ptolemy used geometric models to predict the positions of the sun, moon, and planets, using combinations of circular motion known as epicycles. Having set up this model, Ptolemy then goes on to describe the mathematics which he needs in the rest of the work.
Ptolemy devised new geometrical proofs and theorems. References show. Biography in Encyclopaedia Britannica. D Russian 'Nauka' Moscow, Berlin-Heidelberg-New York, O Petersen, A survey of the Almagest Odense, G J Toomer trs.
K Andersen, The central projection in one of Ptolemy's map constructions, Centaurus 30 2 , - J L Berggren, Ptolemy's maps of earth and the heavens : a new interpretation, Arch.
Exact Sci. J P Britton, Ptolemy's determination of the obliquity of the ecliptic, Centaurus 14 , 29 - B Chatterjee, Geometrical interpretation of the motion of the sun, moon and the five planets as found in the mathematical syntaxis of Ptolemy and in the Hindu astronomical works, J. Asiatic Soc. E Craig ed. Storia Sci. S Drake, Ptolemy, Galileo, and scientific method, Stud.
Yu N Efremov and E D Pavlovskaya, Determination of the epoch of the star catalogue 'Almagest' by analyzing the proper motion of the stars on a problem of the authorship of Ptolemy's star catalogue Russian , Istor. J Evans, On the function and the probable origin of Ptolemy's equant, Amer.
J Evans, On the origin of the Ptolemaic star catalogue, J. Statistical analysis, Acta Appl. O Gingerich, Was Ptolemy a fraud? For this reason Ptolemy is a controversial figure in the history of science. Robert Newton argues in his book The Crime of Claudius Ptolemy , that despite his skill as an astronomer, Ptolemy was simply an astronomical fraud. Newton says that Ptolemy simply fitted his measurements to his theories, rather than vice versa, often adapting observations made centuries before his time.
That assessment hardly endeared Newton to other historians of ancient science.
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