From its conception in the second century up to the late Renaissance, this work determined astronomy as a science. During this time the "Almagest" was not only a work on astronomy; the subject was defined as what is described in the "Almagest". Ptolemy describes himself very clearly what he is attempting to do in writing the work see for example [ 15 ] :- We shall try to note down everything which we think we have discovered up to the present time; we shall do this as concisely as possible and in a manner which can be followed by those who have already made some progress in the field.
For the sake of completeness in our treatment we shall set out everything useful for the theory of the heavens in the proper order, but to avoid undue length we shall merely recount what has been adequately established by the ancients.
However, those topics which have not been dealt with by our predecessors at all, or not as usefully as they might have been, will be discussed at length to the best of our ability. 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. This is the theory which Galileo Galilei and Isaac Newton eventually overthrew more than a thousand years later.
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.
This must be Ptolemy's greatest achievement in terms of an original contribution, since there does not appear to have been any satisfactory theoretical model to explain the rather complicated motions of the five planets before the Almagest. Ptolemy combined the epicycle and eccentric methods to give his model for the motions of the planets. This theory is a masterpiece. He created a sophisticated mathematical model to fit observational data, which before Ptolemy's time was scarce, and the model he produced, although complicated, represents the motions of the planets fairly well.
Ptolemy also a popular account of his results. This work, in 2 books, reduces the mathematical skills needed by a reader. Ptolemy does this rather cleverly by replacing the abstract geometrical theories by mechanical ones.
Ptolemy also wrote a work on astrology. In another book, he discussed methods of finding the angles need to construct a sundial which involves the projection of points on the celestial sphere. In yet another work, he is concerned with stereographic projection of the celestial sphere onto a plane. Ptolemy published a major work Geography , written in eight books, which attempts to map the known world giving coordinates of the major places in terms of latitude and longitude.
It is not surprising that the maps given by Ptolemy were quite inaccurate in many places for he could not be expected to do more than use the available poor data. Another work on optics is in 5 books.
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