1. The problem statement, all variables and given/known data Suppose that, while lying on a beach near the equator watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears. You then stand,elevating your eyes by a height H=1.70 m, and stop the watch when the top of the Sun again disappears. If the elapsed time is t=11.1s, what is the radius r of Earth? 2. Relevant equations Does the Earth's rotation speed come into account? 3. The attempt at a solution This problem is baffling me, as I can't quite grip what to do or where to start. The Earth is also not flat either which introduces another problem. I am pretty sure there is going to be an equation with r in it. Then another one with r+1.7 in it. The other variable, I am not sure of but I know there has to be atleast another one. If someone could please draw a picture and upload, I immensely appreciate it as once I get a visual for what I am doing, I understand a whole lot more, but that is not the case with this problem. Thanks guys.