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 he determined its circumference with an amazing precision to be 250 000 "stadiums". This value corresponds roughly to 46 000 kilometres. Today, as a more exact value the circumference of the earth's equator is taken to be 40 075 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 (description):    The-Sieve-of-Eratosthenes-Text 

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

In the simulation Eratosthenes Sieve procedure can be emulated interactively. The initial range of numbers is displayed in an array of rows and columns; the number of columns can be chosen arbitrarily. By choosing different colors for representing the process of "crossing out", various patterns appear in the course of the Sieve procedure. These patterns can be varied by using different column numbers.

Reaching or exceeding the root of the upper limit is signalled visually. This serves the purpose of showing that after reaching the root of the upper limit no new numbers are crossed out.

After finishing the Sieve procedure all the primes found are printed out.

All input fields can be manipulated at any time. Changes will be effective after pressing one of the buttons "Start" or "Continue".

The simulation can be started by input of the upper limit and the column number - followed by pressing the "Continue" button. Alternatively, it can be started by pressing the "Start" button - in which case default values for the upper limit and number of columns will be applied.