Was it possible to calculate the circumference ot the Earth 200 years B.C.? Yes, the man who did this was Eratosthenes with simple measurings and mathematics. Six countries teams in our project repeated these measurings on 21st March 2011 - a day of equinox. Unfortunately there were clouds in Finland and Croatia, so the students could not measure the shadow of a stick.Because of lack of a camel caravan (which measured the necessary distance for Eratosthenes) we used GoogleEarth programme, geographical coordinates of our schools and on-line program APSalin.

Eratosthenes lived from 276 to 194 b.c. He knew that on the summer solstice at local noon in the city of Syene (Aswan) on the Tropic of Cancer, the sun would appear at the zenith, directly overhead. He also knew, from measurement, that in his hometown of Alexandria, the angle of elevation of the Sun would be 1/50 of a full circle (7°12') south of the zenith at the same time. Assuming that Alexandria was due north of Syene he concluded that the distance from Alexandria to Syene must be 1/50 of the total circumference of the Earth.

Spanish students' presentation about Eratosthenes' measurement: