Eratosthenes

Early Life and Career

Eratosthenes of Cyrene (276 BC – 194 BC, Alexandria) was a Greek mathematician, geographer, philosopher, and astronomer. He is considered one of the greatest scientists of his time.

Achievements

Eratosthenes' most notable achievement is the measurement of the Earth's circumference for the first time. He used a geometrical calculation based on the length of the shade at noon on the day of the summer solstice at a location on a given meridian at a known distance from the Tropic of Cancer, where at this precise time there is no shadow, and the Sun being exactly vertical.

He also introduced a method for finding all prime numbers up to a given number, which bears his name: the Sieve of Eratosthenes. This method is still used today in mathematics.

Director of the Library of Alexandria

Eratosthenes was appointed director of the Great Library of Alexandria by the king of Egypt around 240 BC. He was a scholar recognized by his peers and held this position until his death.

Writings and Interests

Eratosthenes wrote books on various subjects, including mathematics, geography, astronomy, poetry, theatre, literature, and athletics. Unfortunately, most of his works have been lost, with only a few remaining. As a poet, he composed songs about mythological issues, which were intended for amusement rather than education.

Legacy

Eratosthenes is considered the inventor of geography, a term still used today to describe the study of the Earth's physical features and human populations. He was a polymath who made significant contributions to various fields, including mathematics, astronomy, and literature.

References

* Souda (main source for Eratosthene's life)
* Strabon (21)
* Denys de Cyzique (Greek Anthology, 78)
* Lucien de Samosate (Longues Vies, 27)
* Vitruve (De architectura , 1)
* Censorin (De die natali, chap.