ERASTOSTHENES

He was an astronomer, geographer, philosopher and mathematician Greek. He was born in 276 B.C in Libya and died in 194 B.C in Egypt. He was student of Ariston of Chios. Erastosthenes was appointed head of library in 245 B.C at the request of Ptolemy 3 , pharaoh of Egypt , and was tutor to his son Ptolemy4 . The asteroid 3251 was named Erastosthenes in his honor. As a matematician, he established the sieve of Erastosthenes , a method to find by excluding , all the prime numbers. He worked on the problem of duplication of the cube and imagined the mesolable, instrument to know the average proportion.

As an astronomer , he showed the inclination of the ecliptic on the equator and he invented the armillary sphere. His studies focused on the distribution of oceans and continents, the winds , areas climate , and elevations of mountains. He attributes the term geography. He left a general map of the ecumene which was for a long time the unique base of geography. It's the study of the circumference ( or meridian )of the Earth that marks the most work of Erastosthenes. He deduced the circumference in a purely geometrical way.

Minagaetry