Ptolemy

1. Ptolemy By Nick Bobish and Bree Balsamo

2. Biography • His full name is Claudius Ptolemaeus. While there are a lot of theories, no one is sure when he was born or where he died and this reflects in his personal life too. • He is a Greek Egyptian astronomer, mathematician and geographer during the Hellenistic era. • He is most famously known for living in Alexandria, Egypt where he made most of his astronomical observations. • He is also a writer and is know for writing about the subjects of geography, astrology, musical theory, optics, physics, and astronomy.

3. The Ptolemaic System • Using Hipparchus's system of epicycles and eccentric circles and his knowledge about Earth being a sphere, Ptolemy formed his own explanation about his geocentric theory of the solar system. • His system involves over 80 epicycles. These epicycles are used to show explain the motions of the Sun, Moon, and the five planets known during his time. (Mercury, Venus, Sun, Mars, Jupiter, Saturn) • This system became known as the Ptolemaic system.

4. The Almagest • This system can accurately predict the positions of the planets without the need for a telescope. This is mentioned in his well known book, the Almagest. • The Almagest itself is a series made of 13 volumes that applies mathematics to astronomy. • It contains information about many subjects, from earth conceptions, the movements of the sun, moon, and stars, eclipses and the breakdown on the length of months. Lastly it contains a star catalog containing 48 constellations, using the names that are still used today.

5. Geographica • Geographica (Geography) contained most of the information on geography that was collected by the Greeks and the Romans. • It is a work of seven volumes and remained the standard geography textbook until the 15th century. In modern times it is the equivalent to an ancient atlas. • It contains a world map, 26 regional maps and 67 maps for smaller areas. In this collection of map, three different methods for projecting the Earth’s surface is shown. (an equal area projection, a stereographic projection, and a conic projection) • Ptolemy also included directions on how to draw the spherical world on a flat map.

6. Minor Accomplishments • Mentioned before, Ptolemy discovered or developed the concepts of latitude and longitude and knew how to locate nearly 8,000 areas on the world by using longitude and latitude. • When creating his maps, Ptolemy placed the directions North on top and East on left. Now this orientation has become a standard for all maps.

7. Ptolemy’s Influence • Because of Ptolemy’s work, he inspired explorers, such as Christopher Columbus to voyage to unknown places. • Most navigation or factual maps used by early European explores were formed by copies and reprints of Ptolemy’s world maps. • Ptolemy’s theory remained wildly accepted dominated European cartography until 1543 a man named Copernicus created the heliocentric view. • The system Ptolemy created is actually more accurate than Copernicus's and is not notably improved until Kepler's Laws are added along with Copernicus’s idea. • Even though many of Ptolemy’s theories have been changed or proven wrong over the centuries, his works are still famous and became the foundation for future generations.

8. Works Cited • http://obs.nineplanets.org/psc/theman.html • http://www.csiss.org/classics/content/76