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Biographical Info on MacTutor   http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Eratosthenes.html

If, good friend, thou mindest to obtain from any small cube a cube the double of it, and duly to change any solid figure into another, this is in thy power; thou canst find the measure of a fold, a pit, or the broad basin of a hollow well, by this method, that is, if thou thus catch between two rulers two means with their extreme ends converging . . . Thus may it be, and let any one who sees this offering say
"This is the gift of Eratosthenes of Cyrene".       

Eratosthenes epigram on a column in Alexandria

Measuring the Circumference of the Earth:

Eratosthenes' Method   http://astrosun2.astro.cornell.edu/academics/courses//astro201/eratosthenes.htm
Measure the Earth Sci Project   http://www.k12science.org/noonday/
Eratosthenes & the Earth's Diameter   http://outreach.as.utexas.edu/marykay/assignments/eratos1.htm
Math Forum Explains EM   http://mathforum.org/library/drmath/view/57246.html

Prime Number Sites:

Prime Number Quiz   http://tqjunior.thinkquest.org/4116/History/prime.htm
Prime Number Machine   http://www.olympus.net/personal/7seas/pic.html
Eratosthenes Sieve (Javascript demo)   http://www.faust.fr.bw.schule.de/mhb/eratosiv.htm
Eratosthenes Sieve - another demo   http://ccins.camosun.bc.ca/~jbritton/jberatosthenes.htm
Murderous Maths Prime Game   http://www.murderousmaths.co.uk/games/primcal.htm
The Prime Pages   http://primes.utm.edu/
Largest Known Primes   http://www.utm.edu/research/primes/largest.html#intro
Patterns in Prime Numbers   http://www.fermi.franken.de/wschildbach/primes.html
Prime Number Cascade   http://www.olympus.net/personal/7seas/pic.html

Prime numbers, trigonometry, math and geography,large numbers, proportion and ratio.

Eratosthenes Measures the Earth

287 BC to 212 BC in Syracuse, Sicily Greece