Under Ptolemaic rule the economy prospered, based largely on the export of horses and silphium, a plant used for rich seasoning and medicine.

Like any young Greek at the time, Eratosthenes would have studied in the local gymnasium, where he would have learned physical skills and social discourse as well as reading, writing, arithmetic, poetry, and music.

These works and his great poetic abilities led the king Ptolemy III Euergetes to seek to place him as a librarian at the Library of Alexandria in the year 245 BC.

Eratosthenes, then thirty years old, accepted Ptolemy's invitation and traveled to Alexandria, where he lived for the rest of his life.

Eratosthenes created a whole section devoted to the examination of Homer, and acquired original works of great tragic dramas of Aeschylus, Sophocles and Euripides.

In On the Circular Motions of the Celestial Bodies,[11] Cleomedes credited him with having calculated the Earth's circumference around 240 BC, with high accuracy.

Losing the ability to read and to observe nature plagued and depressed him, leading him to voluntarily starve himself to death.

[9] The measurement of Earth's circumference is the most famous among the results obtained by Eratosthenes,[13] who estimated that the meridian has a length of 252,000 stadia (39,060 to 40,320 kilometres (24,270 to 25,050 mi)), with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres (509 and 525 ft)).

[16] A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of one turn.

In the Library of Alexandria he had access to various travel books, which contained various items of information and representations of the world that needed to be pieced together in some organized format.

[1] However, his Geography has been lost to history, although fragments of the work can be pieced together from other great historians like Pliny, Polybius, Strabo, and Marcianus.

While this work is the earliest we can trace certain ideas, words, and concepts in the historical record, earlier contributions may have been lost to history.

Strabo argues it was Alexander's interpretation of their "real intent" in recognizing that "in some people there prevail the law-abiding and the political instinct, and the qualities associated with education and powers of speech".

[24] Eratosthenes was described by the Suda Lexicon as a Πένταθλος (Pentathlos) which can be translated as "All-Rounded", for he was skilled in a variety of things; he was a true polymath.

He wrote on many topics – geography, mathematics, philosophy, chronology, literary criticism, grammar, poetry, and even old comedies.