Greek mathematician Eratosthenes served as the Alexandria Library’s head librarian. He is also credited for creating geography as a field of study. He used an ingenious application of basic geometry to a very challenging problem to determine the size of the Earth. Although he made a lot of assumptions and took a few slight liberties with the truth, his calculations were rather accurate.
Eratosthenes calculated the circumference of Earth by measuring the length of a stick’s shadow in Alexandria and the distance between Alexandria and Syrene on foot. He then took the inverse tangent of the ratio between the shadow’s length and the stick’s length to find the angle of inclination of the Sun. He calculated the total circumference of the Earth to be ((360/7.2) x D ) kilometers, with D being the distance between Alexandria and Syrene.
Project Paridhi is a hands-on activity based project that SPACE India hold to determine the Earth’s circumference. At Delhi Public School Grater Faridabad and Bal Bharati Public School, Pitampura conducted the activity where the students had to measure the circumference of the Earth. Solstice is the best time to conduct this activity. Students from class VIII participated in this activity on the occasion of the winter solstice under the supervision of educators. Students followed the instructions and correctly followed the steps which were discussed during the previous session. Most of the students correctly estimated the circumference of the earth using the Eratosthenes technique.
