Ptolemy's astronomy was therefore simple and elegant in the theoretical building-blocks it used, but disjointed in the model it proposed for the cosmos as a whole. And it was mathematically very demanding: the simulation of Ptolemaic theorizing integrated into Microcosmos necessarily simplifies its processes.
Ptolemy also produced other works. Most important of them was the Geography, a survey of the known world that was to be recovered in the Renaissance and inspire a scholarly tradition of its own. In addition, he wrote the Tetrabiblos, a work on astrology, or, more properly, on celestial causation, that eschewed the mathematical approach of the Almagest for a natural philosopher's attention to substance and process.
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N M Swerdlow, Ptolemy's theory of the inferior planets, J. N M Swerdlow, Ptolemy on trial, Amer. Scholar 48 , - 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. 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.
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