1. The problem statement, all variables and given/known data The sun sets, fully disappearing over the horizon as you lie on the beach, your eyes 20cm above the sand. you immediately jump up, your eyes now 150cm above the sand, and you can again see the top of the sun. if you count the number of seconds until the sun fully disappears again, you can estimate the radius of the earth. but for this problem use the knwon radius of the earth (6,380km) and calculate the time t. 3. The attempt at a solution The method that I used to attempt this question is to find out how fast the earth moves first, which is 107,218km/h. I think this info is essential because at first I must know how fast the earth turns in order to find out the second I will have to look at the sun before it dissapears. Then, I have no idea how to continue on with the problem, since I don't really know how to set the equation for change of the eye level related to the radius of the earth as well as how fast the eaarth moves.