Born around 100 AD
Died around 170 AD
Claudius Ptolemaeus, better known as simply Ptolemy, lived in Alexandria, Egypt during the second century AD. He was a Roman citizen and is well known for his work as an astronomer, a mathematician, a scientist in the field of optics, and a geographer. Ptolemy wrote a book he called Geography, but it was mostly a book about maps.
Ptolemy’s book included directions for making a simple projection, descriptive information of various regions, theory, and maps. It also contained lists of places. Each of these locations were pictured in the volume of maps he created. This atlas of maps depicted the world as it was then known as well as 26 sectional maps.
Ptolemy was the first person to use a mathematically accurate form of projection. Previous to him another Greek geographer, Eratosthenes, worked out a way to calculate the earth’s circumference and used equally spaced parallel lines to show latitude. However Ptolemy, who also believed the earth was round, divided the earth into 360 degrees. This allowed him to not only add lines of latitude to his maps, but longitudinal lines.
The lists of places in Geography were each located on a map. These places could then be identified by both a latitude and a longitude. He completely covered the known parts of the earth in an imaginary network of lines, allowing others to quickly find each place.
While the Romans continued Ptolemy’s tradition of map making, for many years after the second century cartography, or the making of maps, did not advance much. But Ptolemy’s book was preserved in monasteries. His works were studied over the years by individuals including Christopher Columbus, who was greatly influenced by it.
The Geography continued to influence many of the Renaissance map makers and it was printed in many versions. In fact the first printed map of the new world, done by Johannes Ruysch, was included in an edition of Ptolemy’s Geography in 1508.
Books for Children
- How We Learned the Earth Is Round by Patricia Lauber - An interesting yet easily understandable explanation of the beginning of the geographic study of the earth. It describes the basics from the early Greeks to Magellan with a last page on the confirmation of the earth's shape by today's technology. Appropriate for children 5-10 (amazon.com has it ).
- The Geography by Claudius Ptolemy, translated by Edward Luther Stevenson - This is an English translation from the original article, including maps. If you want to dive deep into Ptolemy's geographic accomplishments, this is the book. Appropriate for ages 12 and older. (amazon.com has it)
- Claudius Ptolemy by J J O'Connor and E F Robertson - This is an indepth description of Ptolemy's work, especially the astronomical and mathematical.
- Ptolemy's Geography The Science of the Earth's Surface by the Library of Congress - shows actual pages of Ptolemy's work as well as giving a description about Ptolemy and his studies.
- Nine Planets, a multimedia tour of the solar system by Bill Arnett (note: the logo has been corrected with a hand-written style "8").
- Check out our Night Sky Watching page.