Claudius Ptolemy: biography and contributions of this researcher

Claudius Ptolemy was a Greek astronomer, mathematician, and geographer born in Egypt when the country was a Roman province. The contributions of this scientist were crucial, especially during the Middle Ages and the beginning of the Renaissance.

Not much is known about Ptolemy’s life, but some of his works transcended him, especially thanks to medieval Islamic intellectuals who echoed the precious knowledge that Claudius Ptolemy built up throughout his life. .

Below we will talk a bit about the life of this ancient Greek researcher through a brief biography of Claudius Ptolemy and we’ll see what his job was, and why it was so important.

    Brief biography of Claudius Ptolemy

    Claudius Ptolemy was a Greek astronomer, geographer, mathematician and astrologer born in Egypt in classical antiquity.. He is known for his proposal for the geocentric model of the universe, known as the Ptolemaic system, which had a notorious impact on Christian and Muslim intellectuals in the Middle Ages and part of the Renaissance. He is also credited with creating the first maps with the coordinates of major places on the planet in terms of latitude and longitude.

    His ideas and theories of geography and astronomy were very important until the 16th century, when Copernicus formulated his theory that the planets revolved around the Sun, including the Earth, an idea which until then was all the opposite. Ptolemy’s work is strongly influenced by Hipparchus of Nicaea, a Greek astronomer who lived several centuries before him.

    What do we know about the life of Claudius Ptolemy?

    It is not known when Claudius Ptolemy was born. Some sources point out that it was to take place around AD 85, but other authors believe it was around AD 100. This doubt persists, and will likely never be resolved, as there aren’t many historical documents detailing what his life was like.

    It is believed that his birthplace was in Upper Egypt, more precisely in the city of Ptolemy Hermia., located on the right bank of the Nile, near present-day Menshiyeh. It was one of three cities founded by the Greeks in northern Egypt, the other two being Alexandria and Naucratis.

    There is not much biographical information on Ptolemy, but it can be said that he worked and lived all his life in Egypt. Sources which contribute a little to the life of Claudius Ptolemy underline that he devoted himself mainly to astronomy and astrology. He is also known for his interest in mathematics and geography, and for having carried out numerous works on the knowledge and methods he possessed in these disciplines.

    Not much is known of his death either, although it is believed to have occurred around AD 165 in the city of Alexandria, where he worked as one of its librarians and collectors. knowledge. If it were true that he was born in 100 AD, he would have died at the age of 69 or 70.

      Ptolemaic empiricism

      One of the salient points of Claudius Ptolemy’s work was that he conducted studies emphasizing empiricism. He applied this approach to all his work, which set him apart from other scientists of the time.

      Many of Ptolemy’s descriptions did not seek to be real and exact replicas of the phenomena he was studying, but sought to understand and justify why they deviated from what he observed.

      Influence of Hipparchus of Nicaea

      It is difficult not to speak of Hipparchus of Nicaea in the life of Claudius Ptolemy, because this Greek geographer, mathematician and astronomer greatly influenced the work and the work of Ptolemy. As with Claudius Ptolemy, little is known about Hipparchus, who is known to have lived between 190 and 120 BC. We know the vital information of Hipparchus of Nicaea from the historian and geographer Strabo and Ptolemy himself.

      Claudius Ptolemy repeatedly described the successes and discoveries of Hipparchus and attributed many inventions to him. Among these inventions was a small telescope which helped improve the process of measuring angles, an instrument by which it was possible to establish that the period of the solar year lasted 365 to 6 hours, an approximation very close to that of today is the duration of a natural solar year (365 days, 6 hours, 9 minutes and 9.76 seconds).

      Hipparchus’ influence on Ptolemy’s work was also notorious thanks to the first publication made by the Greco-Egyptian: the Almagest.

      The passage through the Library of Alexandria

      For much of his life, Claudius Ptolemy devoted himself to astronomical observation in the city of Alexandria.. This was done between the reigns of Emperors Hadrian (117-138 AD) and Antoninus Pius (138-171 AD).

      Claudius Ptolemy is seen is part of the so-called second period of the Alexandrian school, which corresponds to a period during which the Roman Empire had spread throughout the Mediterranean and its surroundings.

      Although there is not much information, it is believed that Claudius Ptolemy did a great job at the Library of Alexandria. This building was one of the greatest centers of knowledge in the ancient world, and therefore Ptolemy had the opportunity to access great texts by astronomers and surveyors before his time.

      If this had been true, Claudius Ptolemy would have been the one in charge of compiling and systematizing all this knowledge, in particular those referring to astronomy, data which could date from the 3rd century BC. In addition, he has made many contributions to the field of astronomy, especially with regard to the movement of the planets, thanks to the vast knowledge he has acquired in his work as a librarian.


        Working at the Library of Alexandria, Claudius Ptolemy wrote a book that would become his most important work and his most important contribution to astronomy from a mathematical point of view: the Almagest. It was originally called “Hè megalè syntaxis” (The great composition) in thirteen volumes, but over time it will eventually receive the name by which it is known today, much more emblematic.

        “Almagesto” is a word that comes from the medieval term “almagestum” which, in turn, derives from the Arabic “al-magisti”, which can be translated as “the greatest”. The reason it is now called that is because, although originally written in Greek, it generated a lot of interest in the medieval Islamic world. Caliph al-Mamun (786-833) had it translated into Arabic in 827 and over time it will reach Christian Europe in this language.

          His work on astronomy and astrology

          The Almagest was inspired by the study of Hipparchus of Nicaea while Ptolemy worked at the Library of Alexandria. The artwork refers to the fact that the Earth is the center of the universe and, for this reason, it remains motionless.. The Sun, the Moon and the stars revolve around our planet, and according to Ptolemy, all celestial bodies draw perfectly circular orbits. In this book, he also tells us about the sizes of the Sun, the Moon and a set of celestial bodies which have reached a total of 1,028 stars.

          In ancient times, it was very common for people to believe that the personality was influenced by the position of the Sun, Moon, or other celestial bodies. at the time of birth. Astrology was a deeply rooted belief and shared even among the scientific elites of the time, who came to regard it as a science. Ptolemy was no exception.

          This Greek-Egyptian mathematician wrote a famous treatise on astrology called “Tetrabiblos” (Cuatro Libros), an in-depth work in which he talks about the principles that govern astrology and horoscopes. Inside defended the theory that diseases, illnesses and other health problems were caused by the influence of the Sun, Moon, stars and planets.. Each star had an influence on specific parts of the body.

            His contributions to optics

            One of his most interesting works is the so-called “Optics”, consisting of five volumes where it deals with the theory of mirrors and also with the reflection and refraction of light.

            He took these phenomena into account in his astronomical observations, and it must be said that he was advanced in this regard, because few scientists took into account the luminous and visual phenomena as he did in Greco-classical Egypt.

            His research in geography

            Another of his most important works was “Geography”, a text he completed because Marino de Tiro (60 AD-130 AD) could not complete it.. It is a collection of mathematical techniques allowing to draw more precise geographical maps, to compile different systems of projection and collection of coordinates of the main points of the world known at the time. While the maps were a precedent for making more accurate maps, Ptolemy made the mistake of exaggerating the extent of Asia and Europe.

            His maps are one of the oldest proofs of topographic maps with coordinates, longitude and latitude. Although they contained significant errors, it must be said that they were a big step forward for the mapping of their time. His work served to perfect methods of map projection and introduced terms equivalent to what we know today as parallels and meridians, tracing imaginary lines of altitudes and longitudes.

              Use of plain language

              Specialists in the figure of Claudius Ptolemy emphasize the simple language of works that have survived the passage of time. Ptolemy was aware of the importance of keeping his message simple. understandable to all who read his works, whether they are educated men as well as great mathematicians or ordinary people with a minimum of literacy.

              Ptolemy wanted the knowledge of what he knew to reach many people, regardless of his background in mathematics. You could say he was an outpost and had his own reasoning about cathedral thought, wanting what he discovered to transcend time. He wanted what he knew at the time to be used so that people in the future could discover more of what he discovered.

              He knew that the easier it was to understand his works, the more translations he would make and the more influence he would gain.. For this reason, it is said that, several centuries later, the knowledge collected and formulated by Claudius Ptolemy will serve the Genoese explorer Christopher Columbus, in particular that relating to the calculation of geographical distances and maps of very distant regions. Ptolemy believed that the Earth was a sphere, which is why Columbus thought it was possible to go to western India.

              Bibliographical references

              • García, J. (2003) The Iberian Peninsula in the geography of Claudius Ptolemy. University of the Basque Country. Cultural publishing fund.
              • Dorce, C. (2006) Ptolemy: The Astronomer of the Circles. Spain. Nivoa books and editions.
              • Bellver, J. (2001) Criticisms of Ptolemy in the s. XII. Mexico.
              • Fernández, Tomás and Tamaro, Elena. “Biography of Claude Ptolémée”. In Biographies and Lives. The online biographical encyclopedia [Internet]. Barcelona, ​​Spain, 2004. Available at [fecha de acceso: 23 de diciembre de 2021].
              • Bagrow, L. (1945). The origin of Ptolemy’s geography. Annaler Geographic, 27: 318-387.
              • Stevenson, EL Trad./ed. (1932). Claude Ptolémée: Geography. New York Public Library. Reprint: Dover, 1991.

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