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Eratosthenes of Cyrene (276 BC. Cyrene, North Africa - Alexandria, Egypt, 194 BC.)

One of Eratosthenes' teachers was Ariston of Chios, who studied under Zeno, who himself was a founder of the Stoic school of Philosophy. His other teaher, Callimachus became the librarian of the Alexandrian library - one of the greatest libraries that ever were, which holdings included hundreds of thousands of papyri and vellum scrolls. Eratosthenes went to Alexandria with Callimachus and when Callimachus died in about 240BC, Eratosthenes became a new librarian. He was a third librarian of this famous library.

Eratosthenes will always be remembered for his ingenuity in measuring the circumference of Earth. He gave a surprisingly accurate measurement - and this obviously involved his insight that Earth was a sphere. The details of the measurement were given in his book On the measurement of the Earth which is now lost. Other writers have, however, written on it, so we know that this measurement came from Eratosthenes.

Another great achievement of Eratosthenes was his invention of the calendar that included leap years. Once he did this, he tried to make a comprehensive history of all major events which happened to his time since the siege of Troy.

Eratosthenes is credited also by discovering or describing, his number 'sieve'. Click here to see a page where you can learn more about it, or here to learn more about prime numbers.


See some other famous mathematicians here, or even a page where some of them appear when they were kids.

You can try to work out for yourself how Eratosthenes measure Earth's circumference - click here to get to a page from a University of Texas.

Find more about other Greek mathematicians and their mathematics.


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