1. The problem statement, all variables and given/known data You and a friend decide to determine the radius of the Earth. You synchronize watches; then your friend drives 50km due west, at latitude 40°. Each of you determines the time when the Sun lies due south -- on the meridian Your friend observes the Sun to be on her meridian 140 seconds after you observe the Sun on your meridian. What is your determination for the Earth's radius? 2. Relevant equations rθ=s θ=2π(140s/86400s) 3. The attempt at a solution With those equations I can find the radius of the latitude 40° disc section. If I can find the height h from the center of the earth to the center of my latitude 40 disc, I can use Pythagorean theorem to find radius of the earth R. Is this the correct way to go about this? If so, how do I find the straight line height from center of disc to center of earth?