Eratosthenes of Cyrene: Beta Teacher!


Eratosthenes of Cyrene was the third librarian of the Ancient Library of Alexandria, and one of the greatest scientists humanity has ever known. Eratosthenes, son of Aglaos, was born in Cyrene, Libya in 276 BCE; he passed away around 195 BCE. Throughout his childhood and until his young adulthood, he studied in Cyrene, which was at the time a center of Hellenistic culture.

Eratosthenes then moved to Athena, a significant educational and cultural place, where he studied philosophy, as well as mathematics and sciences, at its major educational centers: Plato’s Academy and Aristotle’s Lyceum. His philosophical beliefs inspired his literary and philosophical publications, which caught the attention. As a result, King Ptolemy III Euergetes summoned him to Egypt to tutor his son. Hence, he gained a scholarship and accommodation at the Mouseion, the home of sciences and arts, and the most famous scientific institute in the Ancient World.

Despite of Eratosthenes’ distinguished status and high rank, he did not stop at that; his scientific contributions were what immortalized him. He founded Geography—the name of which he derived from the word Geographicos, meaning “drawing Earth”—and Cartography, the study and practice of drawing maps. He also founded Chronology, and was the first to document Greek history by date, excluding all myths.

Eratosthenes was also the first to draw the Earth map on a sphere, and was the first to prove through a flawless scientific experiment that the Earth is round. Indeed, he was the first to successfully measure the Earth’s circumference; his result deviates by less than 1% from modern day calculation. He was one of few astronomers in the Ancient Library; moreover, he was a mathematician, and founded the “Sieve of Eratosthenes” used for finding prime numbers. Last but not least, he wrote about literature and language.

Eratosthenes’ companions gave him two nicknames that asserted his prolific knowledge as an encyclopedic scientist. The first was “Pentathlos”, meaning “multidisciplinary person with multiple gifts”, which was used at the time to refer to skilled athletes. The second and more famous nick name was “Beta Teacher”; Beta being the second letter in the Greek alphabet, implying that he was second to Plato in all sciences.

Eratosthenes directed the Library of Alexandria for around forty years. During this period, a “daughter library” was built at the Serapeum—currently Kom el Shoqafa, Alexandria—to house the huge number of papyrus scrolls that did not fit in the Main Library building at the Royal Quarter by the Sea. Eratosthenes was keen for knowledge till the end, spending days and nights learning and researching. Unfortunately, he lost his sight at the age of eighty, and hence gave up his job as librarian. It seems his sight meant the world to him, for he then decided to end his life, thus, starving himself to death.

There have been many accounts about the esteemed scientist; unfortunately, none of his written works survived. We only know him through those who followed; everybody endorsed his role, even those who disagreed with him. Everybody acknowledged that he really was the “Beta teacher”. We never knew what exactly happened to his written works; however, it remains amazing that his great legacy survived.

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