The Sieve of Eratosthenes  

(Eratosthenes of Cyrene, ca 276-194 BC)

Eratosthenes of Cyrene was one of the great scientists of antiquity. He taught that the earth is a ball and by ingenious application of the methods of elementary geometry (at a time when most people thought that the earth is a flat disk) he determined its circumference with an amazing precision to be equal to 250000 "stadiums". This value corresponds roughly to 46000 kilometres. Today, as a more exact value the circumference of the earth's equator is taken to be 40075 kilometres.  

Furthermore, the name of Eratosthenes is connected with the Sieve of Eratosthenes. This procedure to generate prime numbers is described as follows.  

The Sieve of Eratosthenes (general description):    The-Sieve-of-Eratosthenes-Text 

Here is an interactive simulation (suitable for experiments) of the Sieve of Eratosthenes:  Sieve-of-Eratosthenes-Simulation  

Some remarks on the simulation: