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Sagar Gokhale
the wells at Syene (a city on Tropic of Cancer) do not see any shadow (Zero Shadow Day). So he performed an experiment at Alexandra, his hometown
Zero Shadow Day Activity Report
14
June 2020
Nationwide experiment to estimate the size of the Earth using Eratosthenes’ Method
ince ancient times, different scholars, astronomers, and mathematicians have put
in efforts to estimate size of the Earth. The branch of the
Science dealing with measurements of Earth is called Geodesy. The earliest conception about the shape of the Earth was that it is a flat body. Later on, when scientific evidences supported the spher- ical shape of the Earth, many scientists tried to estimate the size of it. Pythago- ras, Aristotle, Archimedes (Greece, 5th century BCE), Eratosthenes, Cleomedes (Egypt, 2nd century BCE), Posidonius (Greece, 1st century BCE), Ptolemy (Greece, 2nd century AD), Aryabhata (India, 5th century), Alfraganus (Iran, 9th century), Abu Rayhan al-Biruni (Iran, 10th century) are the few names in the history of geodesy who contrib- uted in developing methods to estimate the size of the Earth. After 16th century, with the evolution of modern physics, astronomers and geoscientists from Europe made very accurate calculations and reached to an accuracy of 100 m. In 19th century, as a result of Central Eu- ropean Arc Measurement, an institute named Mitteleuropäische Gradmessung was founded in Berlin dedicated to the scientific study of Earth using geodetic techniques. In 20th century, it was then converted to the International Associ- ation of Geodesy (IAG), working under the International Union of Geodesy and Geophysics (IUGG).
The Greek astronomer Eratosthenes is the first person who calculated the circumference of Earth and also es- tablished a method to calculate it. His
experiment to find Earth’s circumfer- ence was the first attempt having more than 90% accuracy. He observed that on summer solstice day, the bottom of
Figure 2 Figure 1