Who is Theon of Alexandria?June 25, 2021
Greek scholar and mathematician who lived in Alexandria, Egypt. He wrote various comments on the elements of Euclid and the hand charts of Claudios Ptolemy, as well as made additions and corrections on them. He is also the father of Hypatia, who has a reputation for mathematics.
The biography tradition identifies Theon as one of the Mouseion; in fact, both the library of Alexandria and the Mouseion were destroyed a century ago during the struggle of the emperor Aurelian with the queen of the Palmyrene Empire, Zenobia. Some scholars think that it was closed by the bishop Theophilus by order of the Christian Roman Emperor Theodosius I. He is the father of Hypathia, whose motive was “political jealousy inciting the people to violence” by Socrates Scholasticus.
Theon’s longest lasting work can be said to be his addition to Euclid’s Elements, which was published around 364 AD and became official in the 19th century. Despite the volume and size of this work, it can be said that it contains comments on important works by Theon’s Hellenistic predecessors. These include “lectures” (Synousiai) on Euclid, Ptolemy’s hand charts and Almages, and commentaries on the technical poet Aratus. In one of his comments on the hand charts, Theon states that certain ancient astrologers believed that the precessions of the equinoxes, rather than stasis in eternal motion, instead reversed every 640 years, and that the final reversal happened in 158 BC. Theon identifies but does not support this theory. This idea inspired Thabit ibn Qurra in the 9th century to come up with a theory to explain a variation on the oscillation of the equinox motion that he (mistakenly) believed was influenced by the rate of motion.