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Claudius Ptolemy was a Greek geographer and astronomer, who worked out a form of geocentric theory that lasted for 1400 years. The work he did, as compared to other Greek mathematicians, has caused argument and discussion.


Depending on what interpretation of history you believe, Ptolemy was either a top-ranked mathematician, or merely a skilled expositor, or even worse, one who betrayed the integrity and ethics of mathematicians.

Not much is known about the rest of Ptolemy's life. His astronomical observations were made from Alexandria, Egypt, in the years between 127 and 141 AD. His name has roots in both Roman and Greek Egyptian ancestry,

Ptolemy used some observations that were originally made by a mathematician named Theon, who is believed to be also known as Theon of Smyrna. It is believed that he was probably Ptolemy's teacher. Many early works by Ptolemy were dedicated to Syrus, and this may have been another of his teachers.

The major works of Ptolemy survived the years, including the well-known Almagest, contained in thirteen books. This was not the original name of the work - rather, it was called, in Greek, The Mathematical Compilation, and then The Greatest Compilation. This is one of his earliest works and brings forth theories of the Sun, the moon and the planets. Ptolemy worked with the details referring to the planets' motion.

The Almagest by Ptolemy has been used longer than any other scientific text. From the time it was conceived, until the later period of the Renaissance, his work solidified astronomy as a valid science. He believed that the earth was the center of the universe, though, wherein he thought that the earth was fixed and that the stars rotated around it, as did the sun, the moon and other planets.

In his study of the sun, Ptolemy confirmed older beliefs that the earth year was 1/300 less of a day than the standard 365 days, but the actual figure is 1/128 less of a day. This caused the rest of his suppositions to be inaccurate. Many historians and mathematicians find it hard to believe that he could have made such an obvious error.

Ptolemy determined the length of each season, and, using these, his model of the sun had a circular motion, and he no longer described the earth as being at the center of this circle. He also studied the oppositions of moon and sun, and motion of the moon. With this information, he developed a theory to explain eclipses.

The last books in Almagest discuss Ptolemy's theories on the planets. This is believed to be his greatest original achievement, since there wasn't a satisfactory model before these books were penned. His work in geography was the place where he attempted to map the world into coordinates of longitude and latitude. His work was inaccurate, because of errors in the maps of his time.

After all his works were done, some people still believe that he made more errors than his supporters will agree to. Newton felt that Ptolemy committed scientific crimes against his fellow scholars and scientists, saying that some theories should have been abandoned, rather than propped up with false observations.


Rumor Has It

Ptolemy discovered that objects in motion stay in motion until Peter Griffin sits on them in the Small Pets and Woodland Creatures Rodeo.

Written by Kevin Lepton