2:02   How Eratosthenes calculated the Earth's circumference 2:14   Carl Sagan explains how Eratosthenes calculated circumference of the Earth 8:34   How to Measure The Radius of the Earth Using Only a Camera and the Moon! 4:14   Diameter and Radius of Earth 10:25   The Radius of the Earth | Method Al Biruni 10:36   How to Measure the Earth's Radius 9:20   Why Can't a Planet Be Twice the Radius of Earth? 11:40   How al-Biruni Calculated the Radius of the Earth 8:33   How can YOU calculate the radius of the Earth? 7:50   Nandana Fort: Calculation of Earth's Radius by Al-Biruni almost 1000 years ago 4:31   Calculating Radius of Earth. 8:15   How We Calculated the Radius of Earth 3:17   How can we measure the radius of the Earth? 1:36   How did Eratosthenes calculate the circumference of the Earth? 1:50   If R is the radius of the earth and the acceleration due to gravity on the surface of earth is g = π 4:58   We Got The Radius Of The Earth! 3:02   200BC: Eratosthenes calculates Earth radius. How does he do it? 5:24   finding radius of earth, mathematical modelling