*Past talk:*

##### 12:00 Friday, April 10 WAG 316

## Richard Fitzpatrick

## “Ptolemy’s Almagest: Fact and Fiction”

The modern world inherited two major scientific treatises from the civilization of Ancient Greece. The first of these, the *Elements* of Euclid, is a large compendium of mathematical theorems concerning geometry, proportion, and number theory. The *Elements* is rightly regarded as the first, largely successful, attempt to construct an axiomatic system in mathematics, and is still held in high esteem within the scientific community. The second treatise, the *Almagest* of Claudius Ptolemy, is an attempt to find a simple geometric explanation for the apparent motions of the sun, the moon, and the five visible planets in the earth’s sky. The scientific reputation of the *Almagest* has not fared as well as that of Euclid’s *Elements*. Nowadays, it is a commonly held belief, even amongst scientists, that Ptolemy’s mistaken adherence to the tenets of Aristotelian philosophy—in particular, the immovability of the earth, and the necessity for heavenly bodies to move uniformly in circles—led him to construct an overcomplicated, unwieldy, and faintly ridiculous model of planetary motion. The aim of this talk is to re-examine the scientific merits of the Almagest and to determine whether the aforementioned criticisms are fair.

*UT Professor of Physics Fitzpatrick is author of several books, including *Plasma Physics: An Introduction* (2014) and a translation of *Euclid’s Elements of Geometry* (2007). *