Eratosthenes was a Greek polymath. He devised an algorithm for identifying primes (the sieve of Eratosthenes). His calculation of the earth’s circumference was known of but rejected by, Columbus, who reckoned about 25% less. Had Columbus accepted the calculation, he may well have founded a new world and not, as he believed, Asia.
Eratosthenes was known to his devotees as “Pentathlos”, an intellectual athlete of wide achievement, while his critics called him “Beta”.
In his spare time, this chief librarian of Alexandria’s Library devised a calendar of world events, putting the fall of Troy at, to the modern ear, 24 April 1184.
Three thousand one hundred years later, 24 April 1916 was the first day of the Easter Rising, with Pádraig Pearse reading the Proclamation outside the Dublin GPO.
